Search

Background and Aims: The traditional practice of administrating neuromuscular blocking drugs (NMBDs) after checking face mask ventilation is challenged repeatedly. This study compared the efficiency of face mask ventilation before and after administrating an NMBD in a patient with a normal airway. The secondary outcome measured was the grade of mask ventilation and tracheal intubating conditions. Methods: After ethical approval, patients (n = 120) in the age group of 18-65 years scheduled for elective surgery under general anaesthesia were randomly assigned into two groups. Group 1 received an NMBD before checking face mask ventilation. Group 2 received an NMBD after checking face mask ventilation. Lungs were ventilated for 180 s, during which expiratory tidal volume (Vte) was recorded as the primary outcome. Hans's grading for face mask ventilation was used to grade mask ventilation. The ease of intubation was assessed based on intubating conditions (ease of laryngoscopy, vocal cord movement, and limb movement). SPSS 20.0 software was used for statistical analysis. Results: For a total of 180 seconds of mask ventilation, the mean (standard deviation) Vte measured after apnoea was significantly higher in Group 1 versus Group 2 [471.9 (63.3) vs 434.8 (77.0) mL/breath, P = 0.004]. The intubating condition was either excellent or good in all patients. Conclusion: The administration of NMBDs resulted in a larger mask Vte and shorter intubation time. Keywords: Airway, expiratory tidal volume, face mask, intubation conditions, muscle relaxant, neuromuscular blocking drug, ventilation, Author(s): Supriya Kumar [1]; Mumtaz Hussain (corresponding author) [1]; Alok K. Bharti [1]; Arvind Kumar [1] INTRODUCTION Face mask ventilation is an essential airway management skill for general anaesthesia and [...]

Author(s): Laurent Papazian [sup.1] [sup.2] [sup.3] , Laveena Munshi [sup.4] , Claude Guérin [sup.5] [sup.6] [sup.7] Author Affiliations: (1) Centre Hospitalier de Bastia, Service de Réanimation, , 604 Chemin de [...]

Author(s): Shagun B. Shah (corresponding author) [1]; Jitendra Kumar Dubey [1]; Vineet Chaudhary [1]; Rajiv Chawla [1] Sir, Traditional teaching prompts immediate switch-over to the manual-mode on encountering ventilator-malfunction, then [...]

Byline: Vithal. Dhulkhed, Pavan. Dhulkhed, Anusha. Katti, Madhuri. Kurdi, Sukhminder. Singh Bajwa Understanding the basic concepts and the dynamics of the equation of motion will help the anaesthesiologist and the [...]

Author(s): Nagarjuna Thakur (corresponding author) [1]; Aamuktha Malyadha Ramidi [1]; R. Gopinath [2]; M Srinivas [3] INTRODUCTION High flow nasal cannula (HFNC) is a relatively newer non-invasive ventilation therapy that [...]

Author(s): Theodoros Vassilakopoulos [sup.1] , Dimitrios Toumpanakis [sup.1] , Jordi Mancebo [sup.2] Author Affiliations: (1) grid.5216.0, 0000 0001 2155 0800, 3rd Department of Critical Care Medicine, Evgenideion Hospital, National & [...]

Author(s): Arnaud W. Thille [sup.1] [sup.2] [sup.3] , Ferran Roche-Campo [sup.4] , Laurent Brochard [sup.5] [sup.6] Author Affiliations: (1) 0000 0000 9336 4276, grid.411162.1, CHU de Poitiers, Service de Réanimation [...]

Author(s): T. Mauri [sup.1] , C. Guérin [sup.2] [sup.3] [sup.4] , R. Hubmayr [sup.5] Author Affiliations: (1) 0000 0004 1757 2822, grid.4708.b, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, University [...]

Byline: Francois Lellouche (1,2,5), Salvatore Maurizio Maggiore (1,3), Aissam Lyazidi (1), Nicolas Deye (1,4), Solenne Taille (1), Laurent Brochard (1) Keywords: Mechanical ventilation; Non-invasive ventilation; Heated humidifiers; Heat and moisture exchangers; Humidification; Psychrometry Abstract: Introduction No clear recommendation exists concerning humidification during non-invasive ventilation (NIV) and high flow CPAP, and few hygrometric data are available. Methods We measured hygrometry during NIV delivered to healthy subjects with different humidification strategies: heated humidifier (HH), heat and moisture exchanger, (HME) or no humidification (NoH). For each strategy, a turbine and an ICU ventilator were used with different FiO.sub.2 settings, with and without leaks. During CPAP, two different HH and NoH were tested. Inspired gases hygrometry was measured, and comfort was assessed. On a bench, we also assessed the impact of ambient air temperature, ventilator temperature and minute ventilation on HH performances (with NIV settings). Results During NIV, with NoH, gas humidity was very low when an ICU ventilator was used (5 mg[H.sub.2]O/l), but equivalent to ambient air hygrometry with a turbine ventilator at minimal FiO.sub.2 (13 mg[H.sub.2]O/l). HME and HH had comparable performances (25--30 mg[H.sub.2]O/l), but HME's effectiveness was reduced with leaks (15 mg[H.sub.2]O/l). HH performances were reduced by elevated ambient air and ventilator output temperatures. During CPAP, dry gases (5 mg[H.sub.2]O/l) were less tolerated than humidified gases. Gases humidified at 15 or 30 mg[H.sub.2]O/l were equally tolerated. Conclusion This study provides data on the level of humidity delivered with different humidification strategies during NIV and CPAP. HH and HME provide gas with the highest water content. Comfort data suggest that levels above 15 mg[H.sub.2]O/l are well tolerated. In favorable conditions, HH and HMEs are capable of providing such values, even in the presence of leaks. Author Affiliation: (1) Service de Reanimation Medicale, Assistance Publique-Hopitaux de Paris, Centre Hospitalier Albert Chenevier, Henri Mondor, Universite Paris 12, Creteil, INSERM U 955, Creteil, France (2) Service de soins intensifs de chirurgie cardiaque, Centre de recherche Institut Universitaire de Cardiologie et de Pneumologie de Quebec, Universite Laval, Quebec, Canada (3) Istituto di anestesiologia e Rianimazione, Universita Cattolica Policlinico A.Gemelli, Rome, Italy (4) Service de Reanimation Medicale, Hopital Lariboisiere, Assistance Publique-Hopitaux de Paris, Paris, France (5) Centre de recherche Institut Universitaire de Cardiologie et de Pneumologie de Quebec, Universite Laval, 2725, chemin Sainte-Foy, Quebec, G1V4G5, Canada Article History: Registration Date: 25/02/2009 Received Date: 28/07/2008 Accepted Date: 29/01/2009 Online Date: 18/03/2009 Article note: This article is discussed in the editorial available at: doi: 10.1007/s00134-009-1457-9. Presented in part at the 2003 American Thoracic Society meeting, 16--21 May, Seattle. Electronic supplementary material The online version of this article (doi: 10.1007/s00134-009-1455-y) contains supplementary material, which is available to authorized users.

Byline: Philipp G. H. Metnitz (1), Barbara Metnitz (2), Rui P. Moreno (3), Peter Bauer (2), Lorenzo Del Sorbo (4), Christoph Hoermann (5), Susana Afonso Carvalho (3), V. Marco Ranieri (4) Keywords: intensive care unit; mechanical ventilation; PEEP; mortality; risk adjustment; outcome Abstract: Objective To evaluate current practice of mechanical ventilation in the ICU and the characteristics and outcomes of patients receiving it. Design Pre-planned sub-study of a multicenter, multinational cohort study (SAPS 3). Patients 13,322 patients admitted to 299 intensive care units (ICUs) from 35 countries. Interventions None. Main measurements and results Patients were divided into three groups: no mechanical ventilation (MV), noninvasive MV (NIV), and invasive MV. More than half of the patients (53% [CI: 52.2-53.9%]) were mechanically ventilated at ICU admission. FiO.sub.2, Vt and PEEP used during invasive MV were on average 50% (40-80%), 8 mL/kg actual body weight (6.9-9.4 mL/kg) and 5 cm[H.sub.2]O (3-6 cm[H.sub.2]O), respectively. Several invMV patients (17.3% (CI:16.4-18.3%)) were ventilated with zero PEEP (ZEEP). These patients exhibited a significantly increased risk-adjusted hospital mortality, compared with patients ventilated with higher PEEP (O/E ratio 1.12 [1.05-1.18]). NIV was used in 4.2% (CI: 3.8-4.5%) of all patients and was associated with an improved risk-adjusted outcome (OR 0.79, [0.69-0.90]). Conclusion Ventilation mode and parameter settings for MV varied significantly across ICUs. Our results provide evidence that some ventilatory modes and settings could still be used against current evidence and recommendations. This includes ventilation with tidal volumes >8mL/kg body weight in patients with a low PaO2/FiO2 ratio and ZEEP in invMV patients. Invasive mechanical ventilation with ZEEP was associated with a worse outcome, even after controlling for severity of disease. Since our study did not document indications for MV, the association between MV settings and outcome must be viewed with caution. Author Affiliation: (1) ICU 13I1, Dept. of Anesthesiology and General Intensive Care, Medical University of Vienna, Vienna, Austria (2) Dept. of Medical Statistics, Medical University of Vienna, Vienna, Austria (3) Unidade de Cuidados Intensivos Polivalente, Hospital de St. Antonio dos Capuchos, Centro Hospitalar de Lisboa Central, E.P.E. Lisboa, Portugal (4) Dipartimento di Anestesiologia e Rianimazione, Universita di Torino, Ospedale S. Giovanni Battista-Molinette, Torino, Italy (5) Transplant ICU, Dept. of Anesthesiology and General Intensive Care, Medical University of Innsbruck, Innsbruck, Austria Article History: Registration Date: 10/02/2009 Received Date: 01/10/2008 Accepted Date: 30/12/2008 Online Date: 14/03/2009 Article note: Statistical analysis was supported by a grant from the Fund of the Austrian National Bank, Project 12690 ONB. This article is discussed in the editorial available at: doi: 10.1007/s00134-009-1450-3. Electronic supplementary material The online version of this article (doi: 10.1007/s00134-009-1449-9) contains supplementary material, which is available to authorized users.

Byline: F. Willem Rozendaal (1), Peter E. Spronk (2), Ferdinand F. Snellen (3), Adri Schoen (4), Arthur R. H. Zanten (5), Norbert A. Foudraine (6), Paul G. H. Mulder (7), Jan Bakker (7) Keywords: Analgesia; Intensive care; Mechanical ventilation; Remifentanil; Sedation; Weaning Abstract: Objective Compare duration of mechanical ventilation (MV), weaning time, ICU-LOS (ICU-LOS), efficacy and safety of remifentanil-based regimen with conventional sedation and analgesia. Design Centre randomised, open-label, crossover, 'real-life' study. Setting 15 Dutch hospitals. Patients Adult medical and post-surgical ICU patients with anticipated short-term (2--3 days) MV. Interventions Patient cohorts were randomised to remifentanil-based regimen (n = 96) with propofol as required, for a maximum of 10 days, or to conventional regimens (n = 109) of propofol, midazolam or lorazepam combined with fentanyl or morphine. Measurements and main results Outcomes were weaning time, duration of MV, ICU-LOS, sedation- and analgesia levels, intensivist/ICU nurse satisfaction, adverse events, mean arterial pressure, heart rate. Median duration of ventilation (MV) was 5.1 days with conventional treatment versus 3.9 days with remifentanil (NS). The remifentanil-based regimen reduced median weaning time by 18.9 h (P = 0.0001). Median ICU-LOS was 7.9 days versus 5.9 days, respectively (NS). However, the treatment effects on duration of MV and ICU stay were time-dependent: patients were almost twice as likely to be extubated (P = 0.018) and discharged from the ICU (P = 0.05) on day 1--3. Propofol doses were reduced by 20% (P = 0.05). Remifentanil also improved sedation-agitation scores (P < 0.0001) and intensivist/ICU nurse satisfaction (P < 0.0001). All other outcomes were comparable. Conclusions In patients with an expected short-term duration of MV, remifentanil significantly improves sedation and agitation levels and reduces weaning time. This contributes to a shorter duration of MV and ICU-LOS. Author Affiliation: (1) Jeroen Bosch Hospital, 's-Hertogenbosch, The Netherlands (2) Gelre Hospitals, Apeldoorn, The Netherlands (3) Isala Clinics, Zwolle, The Netherlands (4) Rivierenland Hospital, Tiel, The Netherlands (5) Gelderse Vallei Hospital, Ede, The Netherlands (6) VieCuri Medical Centre North-Limburg, Venlo, The Netherlands (7) Department of Intensive Care, Hs-324, Erasmus MC University Medical Centre, P.O Box 2040, 3000 CA, Rotterdam, The Netherlands Article History: Registration Date: 02/10/2008 Received Date: 19/12/2007 Accepted Date: 17/09/2008 Online Date: 24/10/2008 Article note: Electronic supplementary material The online version of this article (doi: 10.1007/s00134-008-1328-9) contains supplementary material, which is available to authorized users.

Byline: Esko Ruokonen (1), Ilkka Parviainen (1), Stephan M. Jakob (2), Silvia Nunes (3), Maija Kaukonen (4), Stephen T. Shepherd (5), Toni Sarapohja (5), J. Raymond Bratty (5), Jukka Takala (2) Keywords: Dexmedetomidine; Sedatives; Deep sedation; Conscious sedation; Intensive care; Critical care; Mechanical ventilation Abstract: Purpose To compare dexmedetomidine (DEX) with standard care (SC, either propofol or midazolam) for long-term sedation in terms of maintaining target sedation and length of intensive care unit (ICU) stay. Methods A pilot, phase III, double-blind multicenter study in randomized medical and surgical patients (n = 85) within the first 72 h of ICU stay with an expected ICU stay of aY=48 h and sedation need for aY=24 h after randomization. Patients were assigned to either DEX (a$?1.4 ug kg.sup.-1 h.sup.-1 n = 41) or SC (n = 44), with daily sedation stops. Results Non-inferiority of DEX versus SC was not confirmed. Target Richmond agitation--sedation score (RASS) was reached a median of 64% (DEX) and 63% (SC) of the sedation time (ns). The length of ICU stay was similar in DEX and SC. Patients with RASS target 0--3 (DEX 78%, SC 80%) were at target sedation 74% (DEX) and 64% (SC) of the time (ns), whereas those with RASS target -4 or less reached the target 42% (DEX) and 62% (SC) of the time (P = .006). Post hoc analyses suggested shorter duration of mechanical ventilation for DEX (P = 0.025). Conclusions This pilot study suggests that in long-term sedation, DEX is comparable to SC in maintaining sedation targets of RASS 0 to -3 but not suitable for deep sedation (RASS -4 or less). DEX had no effect on length of ICU stay. Its effects on other relevant clinical outcomes, such as duration of mechanical ventilation, should be tested further. Author Affiliation: (1) Department of Anesthesiology and Intensive Care Medicine, Kuopio University Hospital, P.O. Box 1777, 70211, Kuopio, Finland (2) Department of Intensive Care Medicine, Bern University Hospital and University of Bern, 3010, Bern, Switzerland (3) Department of Intensive Care, Tampere University Hospital, P.O. Box 2000, 33521, Tampere, Finland (4) Units of Intensive Care Medicine, Division of Anesthesiology and Intensive Care Medicine, Department of Surgery, Helsinki University Central Hospital, P.O. Box 340, 00029, HUS, Helsinki, Finland (5) Orion Pharma, P.O. Box 65, 02101, Espoo, Finland Article History: Registration Date: 03/09/2008 Received Date: 13/05/2008 Accepted Date: 14/08/2008 Online Date: 16/09/2008 Article note: Registered at ClinicalTrials.gov, number NCT00226785. A complete list of investigators and study centers appears in the Appendix. This study was sponsored by Orion Pharma, Helsinki, Finland, through research contracts negotiated directly with the participating hospitals. Electronic supplementary material The online version of this article (doi: 10.1007/s00134-008-1296-0) contains supplementary material, which is available to authorized users.

Byline: Alysson R. Carvalho (1,2), Peter M. Spieth (1), Paolo Pelosi (3), Marcos F. Vidal Melo (4), Thea Koch (1), Frederico C. Jandre (2), Antonio Giannella-Neto (2), Marcelo Gama Abreu (1,5) Keywords: Acute lung injury; Lung protective strategy; Ventilator-induced lung injury Abstract: Objective To evaluate the ability of three indices derived from the airway pressure curve for titrating positive end-expiratory pressure (PEEP) to minimize mechanical stress while improving lung aeration assessed by computed tomography (CT). Design Prospective, experimental study. Setting University research facilities. Subjects Twelve pigs. Interventions Animals were anesthetized and mechanically ventilated with tidal volume of 7 ml kg.sup.-1. In non-injured lungs (n = 6), PEEP was set at 16 cm[H.sub.2]O and stepwise decreased until zero. Acute lung injury was then induced either with oleic acid (n = 6) or surfactant depletion (n = 6). A recruitment maneuver was performed, the PEEP set at 26 cm[H.sub.2]O and decreased stepwise until zero. CT scans were obtained at end-expiratory and end-inspiratory pauses. The elastance of the respiratory system (Ers), the stress index and the percentage of volume-dependent elastance (%E .sub.2) were estimated. Measurements and main results In non-injured and injured lungs, the PEEP at which Ers was lowest (8--4 and 16--12 cm[H.sub.2]O, respectively) corresponded to the best compromise between recruitment/hyperinflation. In non-injured lungs, stress index and %E .sub.2 correlated with tidal recruitment and hyperinflation. In injured lungs, stress index and %E .sub.2 suggested overdistension at all PEEP levels, whereas the CT scans evidenced tidal recruitment and hyperinflation simultaneously. Conclusion During ventilation with low tidal volumes, Ers seems to be useful for guiding PEEP titration in non-injured and injured lungs, while stress index and %E .sub.2 are useful in non-injured lungs only. Our results suggest that Ers can be superior to the stress index and %E .sub.2 to guide PEEP titration in focal loss of lung aeration. Author Affiliation: (1) Clinic of Anesthesiology and Intensive Care Therapy, Medical Faculty, University Hospital Carl Gustav Carus, Dresden, Germany (2) Program of Biomedical Engineering, COPPE, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil (3) Department of Ambient, Health and Safety, University of Insubria, Varese, Italy (4) Department of Anesthesia and Critical Care, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA (5) Pulmonary Engineering Group, Department of Anesthesiology and Intensive Care Therapy, University Hospital Dresden, Fetscherstrasse 74, 01307, Dresden, Germany Article History: Registration Date: 18/09/2008 Received Date: 15/10/2007 Accepted Date: 08/09/2008 Online Date: 30/09/2008 Article note: Electronic supplementary material The online version of this article (doi: 10.1007/s00134-008-1301-7) contains supplementary material, which is available to authorized users.

Byline: N. Patroniti (1,3), M. Saini (1), A. Zanella (1), D. Weismann (2), S. IsgrA2 (1), G. Bellani (1), G. Foti (4), A. Pesenti (1) Keywords: Oxygen washin--washout; Functional residual capacity; End-expiratory lung volume; Helium dilution; ARDS mechanical ventilation Abstract: Objective Assessing limits of agreement with helium dilution and repeatability of a new system (lung funcution, LUFU) that measures end-expiratory lung volume (EELV) in mechanically ventilated patients using the O.sub.2 washin (EELV.sub.Win) and washout (EELV.sub.Wout) technique. LUFU consists of an Evita 4 ventilator, a side-stream oxygen analyzer, and a dedicated PC software. Design and setting Prospective human study in a general ICU of a University hospital. Patients Thirty-six mechanically ventilated patients. Interventions We obtained 36 couples of both EELV.sub.Win and EELV.sub.Wout measurements in each patient (5 with healthy lungs, 9 with ALI, 22 with ARDS). Measurements were obtained with patients ventilated either by assisted (ASB, 16 measurements) or controlled (CMV, 20 measurements) ventilation. In 19 of 20 cases in CMV, we obtained helium dilution measurements (EELV.sub.He). Measurements and results Bias for agreement with EELV.sub.He was -16 +- 156 and 8 +- 161 ml, respectively, for EELV.sub.Win and EELV.sub.Wout. Bias for agreement between EELV.sub.Win and EELV.sub.Wout was 28 +- 78 and 23 +- 168 ml, respectively, for CMV and ASB. During CMV bias for repeatability were 8 +- 92 and 23 +- 165 ml, respectively, for EELV.sub.Win and EELV.sub.Wout. During ASB bias for repeatability were 32 +- 160 and -15 +- 147 ml, respectively, for EELV.sub.Win and EELV.sub.Wout. Conclusions The LUFU method showed good agreement with helium, and good repeatability during partial and controlled mechanical ventilation. The technique is simple and safe. Author Affiliation: (1) Department of Experimental Medicine, University of Milano-Bicocca, Ospedale San Gerardo Nuovo dei Tintori, via Donizetti 106, 20052, Monza, Milan, Italy (2) Draegerwerk AG, Luebeck, Germany (3) Department of Experimental Medicine, University of Milano-Bicocca, Ospedale San Gerardo Nuovo dei Tintori, via Cadore 48, 20048, Monza, Milan, Italy (4) Dipartimento di Medicina perioperatoria, Ospedale San Gerardo Nuovo dei Tintori, via Cadore 48, 20052, Monza, Milan, Italy Article History: Registration Date: 09/07/2008 Received Date: 13/06/2008 Accepted Date: 28/06/2008 Online Date: 23/07/2008

Byline: Davide Colombo (1), Gianmaria Cammarota (1), Valentina Bergamaschi (1), Marta Lucia (1), Francesco Della Corte (1), Paolo Navalesi (1) Keywords: Mechanical ventilation; Patient--ventilator interaction; Diaphragm electrical activity; Pressure support ventilation; Neurally adjusted ventilatory assist Abstract: Objective Neurally adjusted ventilatory assist (NAVA) is a new mode wherein the assistance is provided in proportion to diaphragm electrical activity (EAdi). We assessed the physiologic response to varying levels of NAVA and pressure support ventilation (PSV). Setting ICU of a University Hospital. Patients Fourteen intubated and mechanically ventilated patients. Design and protocol Cross-over, prospective, randomized controlled trial. PSV was set to obtain a V t/kg of 6--8 ml/kg with an active inspiration. NAVA was matched with a dedicated software. The assistance was decreased and increased by 50% with both modes. The six assist levels were randomly applied. Measurements Arterial blood gases (ABGs), tidal volume (V t/kg), peak EAdi, airway pressure (Paw), neural and flow-based timing. Asynchrony was calculated using the asynchrony index (AI). Results There was no difference in ABGs regardless of mode and assist level. The differences in breathing pattern, ventilator assistance, and respiratory drive and timing between PSV and NAVA were overall small at the two lower assist levels. At the highest assist level, however, we found greater V t/kg (9.1 +- 2.2 vs. 7.1 +- 2 ml/kg, P < 0.001), and lower breathing frequency (12 +- 6 vs. 18 +- 8.2, P < 0.001) and peak EAdi (8.6 +- 10.5 vs. 12.3 +- 9.0, P < 0.002) in PSV than in NAVA we found mismatch between neural and flow-based timing in PSV, but not in NAVA. AI exceeded 10% in five (36%) and no (0%) patients with PSV and NAVA, respectively (P < 0.05). Conclusions Compared to PSV, NAVA averted the risk of over-assistance, avoided patient--ventilator asynchrony, and improved patient--ventilator interaction. Author Affiliation: (1) Universita degli Studi del Piemonte Orientale 'A. Avogadro', SCDU Anestesia, Terapia Intensiva e Rianimazione Generale, Azienda Ospedaliera Universitaria 'Maggiore della Carita', C.so Mazzini 18, 28100, Novara, Italy Article History: Registration Date: 24/06/2008 Received Date: 08/04/2008 Accepted Date: 26/05/2008 Online Date: 16/07/2008 Article note: This article is discussed in the editorial available at: doi: 10.1007/s00134-008-1215-4.

Byline: Etienne Javouhey (1), Audrey Barats (2), Nathalie Richard (1), Didier Stamm (1), Daniel Floret (1) Keywords: Bronchiolitis; Non-invasive ventilation; Pulmonary infection; Children; Duration of ventilation Abstract: Objective To report our experience of non-invasive ventilation (NIV) as primary ventilatory support strategy in infants admitted for severe bronchiolitis. Design and setting Retrospective study in a paediatric intensive care unit of an university hospital. Patients Infants aged less than 12 months, admitted for bronchiolitis during 2003--2004 and 2004--2005 winter epidemics. Intervention NIV was used as the primary ventilatory support during the second winter (NIV period), whereas invasive ventilation (IV) was the only support employed during the first winter (IV period). NIV consisted in either continuous positive airway pressure (CPAP from 5 to 10 cm[H.sub.2]O) or bilevel positive airway pressure (inspiratory pressure from 12 to 18 cm[H.sub.2]O) with a nasal mask. Results During the IV period, 53 infants were included, compared to 27 during the NIV period. The two groups did not differ in age or in number of premature births. Children in NIV group had less apnoea on admission. The intubation rate was reduced during NIV period (p < 0.001). No children had ventilator-associated pneumonia (VAP) during NIV period compared to nine during IV period (p < 0.05). In the NIV group, 10 infants (37%) required supplemental oxygen for more than 8 days compared to 33 children (65%) in IV group (p < 0.05). The length of hospital stay and the duration of ventilation were similar. Conclusions In this retrospective study, the use of NIV decreased the rate of ventilator associated pneumonia and reduced the duration of oxygen requirement without prolonging the hospital stay. Author Affiliation: (1) Service de Reanimation Pediatrique Hopital Femme Mere Enfant, Groupement Hospitalier Est, 59 Boulevard Pinel, Hospices Civils de Lyon, Universite Lyon 1, 69677, Bron Cedex, France (2) Service de pediatrie 2, Hopital Hautepierre, avenue Moliere, 67200, Strasbourg, France Article History: Registration Date: 07/05/2008 Received Date: 02/03/2007 Accepted Date: 22/12/2007 Online Date: 24/05/2008 Article note: This article is discussed in the editorial available at: doi: 10.1007/s00134-008-1152-2. This work was accepted for a poster presentation in the XXXIVdeg congres de la Societe de Reanimation de Langue Francaise (SRLF). Paris-la Defense, 18--20 janvier 2006 (Reanimation vol 14, suppl 1, SP126) and for an oral presentation in the 8th European Conference in Paediatric and Neonatal Ventilation, 29 Mars--01 Avril 2006, Montreux, Switzerland. Electronic supplementary material The online version of this article (doi: 10.1007/s00134-008-1150-4) contains supplementary material, which is available to authorized users.

For disease states characterized by oscillatory ventilation, an ideal dynamic therapy would apply a counteracting oscillation in ventilation. Modulating respiratory gas transport through the circulation might allow this. We explore the ability of repetitive alternations in heart rate, using a cardiac pacemaker, to elicit oscillations in respiratory variables and discuss the potential for therapeutic exploitation. By incorporating acute cardiac output manipulations into an integrated mathematical model, we observed that a rise in cardiac output should yield a gradual rise in end-tidal C[O.sub.2] and, subsequently, ventilation. An alternating pattern of cardiac output might, therefore, create oscillations in C[O.sub.2] and ventilation. We studied the effect of repeated alternations in heart rate of 30 beats/rain with periodicity of 60 s, on cardiac output, respiratory gases, and ventilation in 22 subjects with implanted cardiac pacemakers and stable breathing patterns. End-tidal C[O.sub.2] and ventilation developed consistent oscillations with a period of 60 s during the heart rate alternations, with mean peak-to-trough relative excursions of 8.4 [+ or -] 5.0% (P < 0.0001) and 24.4 [+ or -] 18.8% (P < 0.0001), respectively. Furthermore, we verified the mathematical prediction that the amplitude of these oscillations would depend on those in cardiac output (r = 0.59, P = 0.001). Repetitive alternations in heart rate can elicit reproducible oscillations in end-tidal C[O.sub.2] and ventilation. The size of this effect depends on the magnitude of the cardiac output response. Harnessed and timed appropriately, this cardiorespiratory mechanism might be exploited to create an active dynamic responsive pacing algorithm to counteract spontaneous respiratory oscillations, such as those causing apneic breathing disorders. periodic breathing; physiology; pacing; reflex

Byline: Peter D. Wagner (1) Keywords: Ventilation/perfusion inequality; Shunt; Alveolar--capillary diffusion limitation; Hypoxemia; Hypercapnia; Inert gases Abstract: This brief review centers on the multiple inert gas elimination technique (MIGET). This technique, developed in the 1970s, measures the pulmonary exchange of a set of six different inert gases dissolved together in saline (or dextrose) and infused intravenously. It then uses those measurements to compute the distribution of ventilation/perfusion ratios that best explains the exchange of the six gases simultaneously. MIGET is based on the very same mass-conservation principles underlying the classic work of Rahn and Fenn and of Riley and coworkers in the 1950s, which defines the relationship between the ventilation/perfusion ratio and the alveolar and capillary partial pressures of any gas. After a brief history of MIGET, its principles are laid out, its information content is explained, and its limitations are described. It is noted that in addition to quantifying ventilation/perfusion inequality and pulmonary shunting, MIGET can identify and quantify diffusion limitation of O.sub.2 exchange, when present, as well as explain the contributions of extrapulmonary influences such as inspired O.sub.2 concentration, ventilation, cardiac output, Hb concentration/P.sub.50, body temperature and acid/base state on arterial oxygenation. An overview of the technical details of implementing MIGET is given, and the review ends with potential future applications. Author Affiliation: (1) Division of Physiology, Department of Medicine, University of California, San Diego, 9500 Gilman Drive, Dept. 0623A, CA 92093-0623A, La Jolla, USA Article History: Registration Date: 25/03/2008 Received Date: 01/02/2008 Accepted Date: 18/03/2008 Online Date: 18/04/2008

Byline: Fekri Abroug (1), Lamia Ouanes-Besbes (1), Souheil Elatrous (2), Laurent Brochard (3) Keywords: ARDS; ALI; Mechanical ventilation; Prone positioning Abstract: Objective To compare the effects of ventilation in prone and in supine position in patients with acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Design Meta-analysis of randomised controlled trials. Data sources BioMedCentral, PubMed, CINAHL, and Embase (to November 2007), with additional information from authors. Measurements and results From selected randomised controlled trials comparing positioning in ALI/ARDS we extracted data concerning study design, disease severity, clinical outcomes, and adverse events. Five trials including 1,372 patients met the inclusion criteria for mortality analysis one trial was added to assess the effects on acquisition of ventilator-associated pneumonia (VAP). The included trials were significantly underpowered and enrolled patients with varying severity. Prone positioning duration and mechanical ventilation strategy were not standardised across studies. Using a fixed-effects model, we did not find a significant effect of prone positioning (proning) on mortality (odds ratio 0.97, 95% confidence interval 0.77--1.22). The PaO.sub.2/FiO.sub.2 ratio increased significantly more with proning (weighted means difference 25 mmHg, pa- Conclusions Prone position is not associated with a significant reduction in mortality from ALI/ARDS despite a significant increase in PaO.sub.2/FiO.sub.2, is safe, and tends to decrease VAP. Published studies exhibit substantial clinical heterogeneity, suggesting that an adequately sized study optimising the duration of proning and ventilation strategy is warranted to enable definitive conclusions to be drawn. Author Affiliation: (1) Service de Reanimation Polyvalente, CHU F. Bourguiba, 5000, Monastir, Tunisia (2) Service de Reanimation Medicale, CHU T. Sfar, Mahdia, Tunisia (3) Service de Reanimation Medicale, AP-HP, Hopital Henri Mondor, INSERM U 841, Creteil, France Article History: Registration Date: 28/02/2008 Received Date: 02/08/2007 Accepted Date: 05/01/2008 Online Date: 19/03/2008

Byline: Nicolas Prost (1,2), Didier Dreyfuss (2,3), Jean-Damien Ricard (2,3,4), Georges Saumon (1,2) Keywords: Pulmonary edema; Intermittent positive pressure ventilation; Beta-adrenergic agonists; Radionuclide imaging Abstract: Objective To evaluate whether a [beta].sub.2-adrenergic agonist may reduce acute alveolo-capillary barrier alterations during high-volume ventilation. Design Experimental study. Setting Animal research laboratory. Subjects A total of 48 male Wistar rats. Interventions A zone of alveolar flooding was produced by liquid instillation in a distal airway. Proteins in the instilled solution were traced with 99m.sup.Tc-albumin. 111.sup.In, which binds to transferrin, was injected into the systemic circulation. Terbutaline was administered in the instilled solution or intra-peritoneally. Conventional ventilation was applied for 30a-min followed by different ventilation strategies for 90a-min: conventional ventilation, high-volume ventilation with or without 6a-cm[H.sub.2]O PEEP. Measurements and main results Protein fluxes across the alveolar and microvascular barriers were evaluated by scintigraphy. High-volume ventilation resulted in immediate leakage of 99m.sup.Tc-albumin from alveolar spaces and increased pulmonary uptake of systemic 111.sup.In-transferrin. Terbutaline in the instilled solution and PEEP lessened alveolar 99m.sup.Tc-albumin leakage and pulmonary 111.sup.In-transferrin uptake due to high-volume ventilation, whereas terbutaline given intra-peritoneally only lessened 111.sup.In-transferrin uptake. Terbutaline in the instilled solution also lessened the increase in lung wet-to-dry weight ratio due to high-volume ventilation. Conclusions Terbutaline reduces protein fluxes across the alveolar epithelial and pulmonary microvascular barriers during high-volume ventilation in vivo. The route of administration may be important. Author Affiliation: (1) INSERM U773, Equipe 11, Centre de Recherche Bichat Beaujon CRB3, BP 416, 75018, Paris, France (2) Site Xavier Bichat, Universite Paris 7 Denis Diderot, 75018, Paris, France (3) Assistance Publique -- Hopitaux de Paris, Service de Reanimation Medicale, Hopital Louis Mourier, 92700, Colombes, France (4) INSERM U722, 75018, Paris, France Article History: Registration Date: 21/11/2007 Received Date: 12/04/2007 Accepted Date: 25/10/2007 Online Date: 18/12/2007 Article note: Grant from CARDIF (Comite pour l'Assistance Respiratoire a Domicile d'Ile de France) Part of this study was presented in abstract form at the 35th meeting of the SRLF (Societe de Reanimation de Langue Francaise), 2007. This article is discussed in the editorial available at: http://dx.doi.org/10.1007/s00134-007-0966-7.

Byline: Claudia C. Dos Santos (1,2) Keywords: Fibroproliferation; Pulmonary fibrosis; Fibrosing alveolitis; Matrix deposition; Pulmonary remodelling Abstract: Background Acute respiratory distress syndrome (ARDS) is the most severe manifestation of acute lung injury (ALI). In patients who survive the acute injury the process of repair and remodelling may be an independent risk factor determining morbidity and mortality. This review explores recent advances in the field of fibroproliferative ARDS/ALI, with a special emphasis on (a) the primary contributing factors with a focus on cellular and soluble factors, and (b) mechanisms involved in repair and remodelling as they pertain to the importance of cell death, re-population, and matrix deposition. Discussion Factors influencing progression to fibroproliferative ARDS vs. resolution and reconstitution of the normal pulmonary parenchymal architecture are poorly understood. Determinants of persistent injury and abnormal repair and remodelling may be profoundly affected by both environmental and genetic factors. Moreover, cumulative evidence suggests that acute inflammation and fibrosis may be in part independenta-anda-interactivea-processes that are autonomously regulated and thus amenable to individual and specific therapy. Conclusions Although our current understanding of these processes is limited by the inability to accurately replicate the complex humana-physiologya-in laboratory settings, it has recently become apparent that the process of repair and remodelling begins early in the course of ARDS/ALI and may be determined by the type of pulmonary injury. Understanding the mechanisms leading to and regulating fibroproliferative changes may contribute to the development of novel early therapeutic interventions in ARDS/ALI patients. Author Affiliation: (1) Interdepartmental Division of Critical Care, University of Toronto, 30, Bond Street 4-008, M5G 1W8, Toronto, Ontario, Canada (2) Department of Critical Care Medicine, Saint Michael's Hospital, Toronto, Ontario, Canada Article History: Registration Date: 23/11/2007 Received Date: 18/09/2006 Accepted Date: 03/09/2007 Online Date: 09/02/2008 Article note: This article is discussed in the editorial available at: http://dx.doi.org/10.1007/s00134-007-0965-8.

Acute lung injury (ALI) in combination with acute kidney injury carries a mortality approaching 80% in the intensive care unit. Recently, attention has focused on the interaction of the lung and kidney in the setting of ALI and mechanical ventilation (MV). Small animal models of ALI and MV have demonstrated changes in inflammatory mediators, water channels, apoptosis, and function in the kidney early in the course of injury. The purpose of this investigation was to test the hypothesis that ALI and injurious MV cause early, measurable changes in kidney structure and function in a canine HC1 aspiration model of ALI when hemodynamics and arterial blood gas tensions are carefully controlled. Intratracheal HC1 induced profound ALI as demonstrated by increased shunt fraction and airway pressures compared with sham injury. Shaminjured animals had similar mean arterial pressure and arterial P[co.sub.2] and HC[O.sub.3] levels compared with injured animals. Measurements of renal function including renal blood flow, urine flow, serum creatinine, glomerular filtration rate, urine albumin-to-creatinine ratio, and kidney histology scores were not different between groups. With maintenance of hemodynamic parameters and alveolar ventilation, ALI and injurious MV do not alter kidney structure and function early in the course of injury in this acid aspiration canine model. Kidney injury in large animal models may be more similar to humans and may differ from results seen in small animal models. mechanical ventilation; biotrauma; renal function

Byline: Mohamad F. El-Khatib (1), Salah M. Zeineldine (2), Ghassan W. Jamaleddine (2) Keywords: Mechanical ventilation; Rapid shallow breathingindex; Pressure support ventilation; Positive end-expiratory pressure; Intensive care unit Abstract: Objective We compared rapid shallow breathing index (RSBI) values under various ventilatory support settings prior to extubation. Design and setting Prospective study in the intensive care unit at a university hospital. Patients Thirty six patients ready for extubation. Interventions Patients were enrolled when receiving pressure support ventilation (PSV) of 5a-cm[H.sub.2]O, PEEP of 5a-cm[H.sub.2]O, and FIO.sub.2 of 40% (PS). Subsequently each patient received a trial of PSV of 0a-cm[H.sub.2]O, PEEP of 5a-cm[H.sub.2]O, and FIO.sub.2 of 40% (CPAP), a trial of PSV of 0a-cm[H.sub.2]O, PEEP of 5a-cm[H.sub.2]O and FIO.sub.2 of 21% (CPAP-R/A), and a 1-minute spontaneously breathing room air trial off the ventilator (T-piece). Trials were carried out in random order. Measurements and results Respiratory frequency (f) and tidal volume (V.sub.T) were measured during PS, CPAP, CPAP-R/A, and T-piece in all patients. RSBI (f/V.sub.T) was determined for each patient under all experimental conditions, and the average RSBI was compared duringPS, CPAP, CPAP-R/A, and T-piece. RSBI was significantly smaller during PS (46a-+-a-8bpm/l), CPAP (63a-+-a-13bpm/l) and CPAP-R/A (67a-+-a-14bpm/l) vs. T-piece (100a-+-a-23bpm/l). There was no significant difference in RSBI between CPAP and CPAP-R/A. RSBI during CPAP and CPAP-R/A were significantly smaller than RSBI during T-piece. In all patients RSBI values were less than 105a-bpm/l during PS, CPAP, and CPAP-R/A. However, during T-piece the RSBI increased to greater than 105a-bpm/l in 13 of 36 patients. Conclusions In the same patient the use of PSV and/or PEEP as low as 5a-cm[H.sub.2]O can influence the RSBI. In contrast, changes in FIO.sub.2 may have no effect on the RSBI. Author Affiliation: (1) Department of Anesthesiology, American University of Beirut, Riad El Solh, P.O.Box 11-0236, 1107 2020, Beirut, Lebanon (2) Department of Internal Medicine, American University of Beirut, Riad El Solh, P.O.Box 11-0236, 1107 2020, Beirut, Lebanon Article History: Registration Date: 08/11/2007 Received Date: 01/08/2007 Accepted Date: 31/10/2007 Online Date: 01/12/2007

Byline: Andrew C. Argent (1,2), Christopher J. L. Newth (3), Max Klein (2,4) Keywords: Infants; Children; Flow--volume relationship; Pressure flow relationship; Pulmonary function tests; Face mask; Pneumotachygraph; Esophageal pressure measurement Abstract: Rationale The assessment of the severity of croup and response to therapy has remained a clinical one. Despite recognition of the importance of a reproducible and easily applicable method for objectively measuring severity, currently, no such technique exists. Objectives We postulated that measurements of air flow and intrathoracic pressure changes in patients with severe croup would provide detailed information about the mechanics of breathing and the potential for the development of continuous bedside methods for objective monitoring of upper airway obstruction. Methods Twenty out of 21 eligible infants and children with severe upper airway obstruction from croup, and 5 control participants, were studied under light sedation utilizing face masks and nasogastric feeding tubes for flow and esophageal pressure measurements. Measurements and main results Children with croup had lower tidal volumes, but breathed faster, thus maintaining similar minute volumes to the controls. During inspiration, all but 2 croup patients (but no controls) displayed flow limitation. Area within the flow--volume curve was significantly decreased and minute ventilation for effort expended was nearly 4.5 times higher in croup patients than in controls. Peak-to-trough pleural pressure swings, pressure--rate product and pressure--time integral were also significantly higher than in controls (pa- Conclusions Patients with severe croup maintain minute ventilation by means of huge increases in intrathoracic pressure changes. Inspiratory flow limitation is present. In future outcome studies, measurements of respiratory function that do not include intrathoracic pressure changes are unlikely to be effective measures of the severity of croup. Author Affiliation: (1) Division of Paediatric Critical Care and Children's Heart Disease, School of Child and Adolescent Health, University of Cape Town, Cape Town, South Africa (2) Red Cross War Memorial Children's Hospital, Cape Town, South Africa (3) Division of Critical Care Medicine, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA (4) Paediatric Pulmonology Services, School of Child and Adolescent Health, University of Cape Town, Cape Town, South Africa Article History: Registration Date: 27/09/2007 Received Date: 20/12/2006 Accepted Date: 26/09/2007 Online Date: 16/11/2007 Article note: Declaration: The authors are neither supported by, nor maintain any financial interest in, any commercial activity associated with the topic of this article. Electronic supplementary material The online version of this article (doi: 10.1007/s00134-007-0910-x) contains supplementary material, which is available to authorized users.

Byline: Robin Lovat (1), Christine Watremez (2), Michel Dyck (2), Olivier Caenegem (1), Franck Verschuren (3), Philippe Hantson (4), Luc-Marie Jacquet (1) Keywords: Intubated patient; Manual ventilation; Bag-valve device; Limitation of inspiratory gas flow Abstract: Objective To compare in intubated patients manually ventilated in order to mirror the ventilator, the respiratory and hemodynamic effects induced by a bag device equipped with an inspiratory gas flow-limiting valve (Smart Bag, 0-Two Medical Technologies Inc., Mississauga, ON, Canada) and a Standard bag. Design Non-randomized crossover study comparing 13a-respiratory and eight hemodynamically paired parameters. Eight intubated patients were manually ventilated, each by three different intensive care workers yielding 24 sets of data for comparison. Data were collected during two sessions of manual ventilation, first with the Standard bag and then with the Smart Bag. Between each session, the patient was reconnected to the ventilator until return to the baseline. Patients, included after coronary surgery, were sedated and paralyzed. Setting Intensive Care Unit, university hospital. Results Compared with Standard bag, the Smart Bag.sup.(r) provided a decrease of inspiratory flow (23a-+-a-4.7 vs. 47.3a-+-a-16.5a-l/min) with a decrease of peak pressure (13.3a-+-a-2.9 vs. 21.9a-+-a-7.3a-cm[H.sub.2]O) and tidal volume (9.4a-+-a-2.8 vs. 12.4a-+-a-2.7a-ml/kg). While the expiratory time was similar, the inspiratory time increased (1.83a-+-a-0.58 vs. 1.28a-+-a-0.46a-s) with the Smart Bag, limiting the respiratory rate (14a-+-a-5 vs. 17a-+-a-6a-cycles/min) and the minute volume (8.8a-+-a-2.9 vs. 14.4a-+-a-4.9a-l/min). Finally, it limited the fall of the ETCO.sub.2 (27.9a-+-a-5.1 vs. 24.3a-+-a-5.7a-mmHg) and probably the risks of severe respiratory alkalosis. The bags similarly affected hemodynamic states. Conclusion In intubated patients manually ventilated, the Smart Bag limits the risks of excessive airway pressure and the fall of the ETCO.sub.2, with hemodynamic effects similar to those of the Standard bag. Author Affiliation: (1) Cardiovascular Department, Intensive Care Unit, Cliniques Universitaires Saint Luc, Avenue Hippocrate 10, 1200, Brussels, Belgium (2) Department of Anesthesiology, Cliniques Universitaires Saint Luc, Avenue Hippocrate 10, 1200, Brussels, Belgium (3) Department of Acute Medicine, Emergency, Cliniques Universitaires Saint Luc, Avenue Hippocrate 10, 1200, Brussels, Belgium (4) Department of Acute Medicine, Intensive Care Unit, Cliniques Universitaires Saint Luc, Avenue Hippocrate 10, 1200, Brussels, Belgium Article History: Registration Date: 05/09/2007 Received Date: 12/02/2007 Accepted Date: 02/08/2007 Online Date: 10/10/2007

Byline: Craig R. Weinert (1,2), Mark Sprenkle (1,3) Keywords: Sedation; Amnesia; Stress disorders, post-traumatic; Intensive care units; Critical illness; Acute respiratory failure Abstract: Objective To determine the relationship between measures of critical illness (sedative/analgesic administration, wakefulness and organ dysfunction), intensive care unit (ICU) recall and symptoms of posttraumatic stress disorder. Design Prospective, observational study with post-ICU follow-up. Setting Medical and surgical ICUs at a teaching hospital. Patients Two hundred seventy-seven subjects requiring >a-36a-h of mechanical ventilation were enrolled 149 completed follow-up interviews 2 months later and 80 at 6 months. Interventions None. Results ICU recall was greater for events occurring at the end of critical illness however, 18% of subjects had amnesia for the entire ICU course. Factual ICU recall was weakly associated with increased wakefulness during mechanical ventilation (r 2.sup.a-=a-0.03--0.11, p Conclusion Wakefulness during mechanical ventilation has a greater influence on post-ICU recall and posttraumatic stress symptoms than sedative drug exposure or severity of illness. It is difficult to predict the future psychological consequences of an individual patient's critical illness. Author Affiliation: (1) Division of Pulmonary, Allergy and Critical Care Medicine, University of Minnesota Medical School, 420 Delaware Street, 55455, Minneapolis, MN, USA (2) Clinical Outcomes Research Center, University of Minnesota Medical School, Minneapolis, MN, USA (3) Hennepin County Medical Center, University of Minnesota Medical School, Minneapolis, MN, USA Article History: Registration Date: 19/07/2007 Received Date: 07/08/2006 Accepted Date: 17/07/2007 Online Date: 17/08/2007 Article note: Work supported by a grant from the National Institutes of Health to C.a-R.a-W. Electronic supplementary material The online version of this article (doi: 10.1007/s00134-007-0829-2) contains supplementary material, which is available to authorized users.

Abstract Objective: To test the usefulness of dead space for determining open-lung PEEP, the lowest PEEP that prevents lung collapse after a lung recruitment maneuver. Design: Prospective animal study. Setting: [...]

Tracheobronchial stenting was performed under general anesthesia, with (six patients) or without (two patients) muscle relaxant, in eight patients suffering from carcinoma. All patients had presented preoperatively with dyspnea, exhibiting [...]

Abstract Rationale: In mechanically ventilated patients respiratory system impedance may vary from time to time, resulting, with pressure modalities of ventilator support, in changes in the level of assistance. Recently, [...]

Purpose. To evaluate the effect of high-frequency jet ventilation (HFJV) and continuous positive airway pressure (CPAP) on oxygenation and the shunt fraction (Qs/Qt) during one-lung ventilation (OLV). Methods. Twenty-five patients [...]

Byline: Michael A. Pakulla (1), David Seidel (1), Detlef Obal (1), Stephan A. Loer (1) Keywords: Rats; Acid aspiration; Partial liquid ventilation Abstract: Objective Partial liquid ventilation can improve respiratory functions in acid-induced lung injury. We studied the effects of the interval between induction of injury and initiation of partial liquid ventilation on survival, gas exchange, and pulmonary neutrophil accumulation. Material and methods Anesthetized rats were randomly assigned to one of five groups (n = 6 per group). Group 1 served as the control group, in the other groups an extended lung injury was induced by intratracheal instillation of hydrochloric acid. Whereas lungs of group 2 were gas-ventilated, group 3 received an early partial liquid ventilation (5 min after acid instillation) and group 4 a delayed partial liquid ventilation (30 min after acid instillation, 5 ml/kg perfluorocarbon). Group 5 received an additional continuous perfluorocarbon application of 5 ml*kg.sup.-1*h.sup.-1 (30 min after acid instillation). Blood gases were measured with an intravascular blood gas sensor. Results Acid instillation resulted in a marked decrease in PO.sub.2-values within 30 min (from 481+-37 mmHg to 128+-71 mmHg, FiO.sub.2 1.0). Survival rate of the study period (12 h) was higher with early partial liquid ventilation. We observed no differences between groups in peak PO.sub.2-values during treatment. Histopathological examination, however, showed less pulmonary neutrophil accumulation in lungs of the early partial liquid ventilation group when compared to the delayed partial liquid ventilation group. Conclusions Our results suggest that early partial liquid ventilation increases survival after extended acid-induced lung injury. While effects on arterial oxygenation appear not to predict acute survival we observed less intrapulmonary neutrophil accumulation with early partial liquid ventilation. Author Affiliation: (1) Department of Anesthesiology, Heinrich-Heine-University, Moorenstrasse 5, 40225, Dusseldorf, Germany Article History: Registration Date: 03/08/2004 Received Date: 16/12/2003 Accepted Date: 26/07/2004 Online Date: 21/09/2004 Article note: Supported by a grant to S. A. Loer from the research committee of the medical faculty of the University of Dusseldorf

Byline: J. A. Farias (1), F. Frutos (2), A. Esteban (2), J. Casado Flores (3), A. Retta (1), A. Baltodano (4), I. Alia (2), T. Hatzis (5), F. Olazarri (1), A. Petros (6), M. Johnson (7) Keywords: Mechanical ventilation; Children; Infants; Survey; Weaning; Outcomes Abstract: Objective To describe the daily practice of mechanical ventilation (MV), and secondarily, its outcome in pediatric intensive care units (PICUs). Design Prospective cohort of infants and children who received MV for at least 12 h. Setting Thirty-six medical surgical PICUs. Patients All consecutive patients admitted to the PICUs during 2-month period. Measurements and main results Of the 1893 patients admitted, 659 (35%) received MV for a median time of 4 days (25th percentile, 75%: 2, 6). Median of age was 13 months (25th percentile, 75%: 5, 48). Common indications for MV were acute respiratory failure (ARF) in 72% of the patients, altered mental status in 14% of the patients, and ARF on chronic pulmonary disease in 10% of the patients. Median length of stay in the PICUs was 8 days (25th percentile, 75%: 5, 13). Overall mortality rate in the PICUs was 15% (confidence interval 95%: 13--18) for the entire population, 50% (95% CI: 25--74) in patients who received MV because of acute respiratory distress syndrome, 24% (95% CI: 16--35) in patients who received MV for altered mental status and 16% (95% CI: 9--29) in patients who received MV for ARF on chronic pulmonary disease. Conclusion One in every 3 patients admitted to the PICUs requires ventilatory support.. The ARF was the most common reason for MV, and survival of unselected infants and children receiving MV for more than 12 h was 85%. Author Affiliation: (1) Unidad de Cuidados Intensivos Pediatricos, Hospital de Ninos R Gutierrez, B de Irigoyen 49, 1834 , Temperley Bs. As, Argentina (2) Unidad de Cuidados Intensivos, Hospital Universitario de Getafe, Madrid, Spain (3) Unidad de Cuidados Intensivos Pediatricos, Hospital Universitario Nino Jesus, Madrid, Spain (4) Unidad de Cuidados Intensivos Pediatricos, Hospital Nacional de Ninos 'Dr. Carlos Saenz H' Universidad de Costa Rica, San Jose, Costa Rica (5) Pediatric Intensive Care Unit, Children's Hospital Santa Sophia, Athens, Greece (6) Pediatric Intensive Care Unit, Great Ormond Street Hospital for Children, London, UK (7) Pediatric Intensive Care Unit, Hospital de Ninos, Panama Article History: Registration Date: 16/02/2004 Received Date: 02/04/2003 Accepted Date: 30/01/2004 Online Date: 17/03/2004 Article note: Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00134-004-2225-5

Byline: Massimo Gorini (1), Roberta Ginanni (1), Giuseppe Villella (1), Donatella Tozzi (1), Annike Augustynen (1), Antonio Corrado (1) Keywords: Non-invasive mechanical ventilation; Acute respiratory failure; Chronic obstructive pulmonary disease; Non-invasive positive pressure ventilation; Negative pressure ventilation Abstract: Objective To investigate in clinical practice the role of non-invasive mechanical ventilation in the treatment of acute respiratory failure on chronic respiratory disorders. Design An 18 months prospective cohort study. Setting A specialised respiratory intensive care unit in a university-affiliated hospital. Patients A total of 258 consecutive patients with acute respiratory failure on chronic respiratory disorders. Interventions Criteria for starting non-invasive mechanical ventilation and for endotracheal intubation were predefined. Non-invasive mechanical ventilation was provided by positive pressure (NPPV) ventilators or iron lung (NPV). Results The main characteristics of patients (70% with chronic obstructive pulmonary disease) on admission were (mean, SD or median, 25th--75th centiles): pH 7.29 (0.07), PaCO.sub.2 83 mm Hg (19), PaO.sub.2/FiO.sub.2 198 (77), APACHE II score 19 (15--24). Among the 258 patients, 200 (77%) were treated exclusively with non-invasive mechanical ventilation (40% with NPV, 23% with NPPV, and 14% with the sequential use of both), and 35 (14%) with invasive mechanical ventilation. In patients in whom NPV or NPPV failed, the sequential use of the alternative non-invasive ventilatory technique allowed a significant reduction in the failure of non-invasive mechanical ventilation (from 23.4 to 8.8%, p=0.002, and from 25.3 to 5%, p=0.0001, respectively). In patients as a whole, the hospital mortality (21%) was lower than that estimated by APACHE II score (28%). Conclusions Using NPV and NPPV it was possible in clinical practice to avoid endotracheal intubation in the large majority of unselected patients with acute respiratory failure on chronic respiratory disorders needing ventilatory support. The sequential use of both modalities may increase further the effectiveness of non-invasive mechanical ventilation. Author Affiliation: (1) Respiratory Intensive Care Unit, Careggi Hospital CTO, Largo Palagi 1, 50134 , Firenze, Italy Article History: Registration Date: 17/12/2003 Received Date: 15/08/2003 Accepted Date: 10/12/2003 Online Date: 21/01/2004 Article note: Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00134-003-2145-9

Byline: Sven Lethvall (1), Sophie Lindgren (1), Stefan Lundin (1), Ola Stenqvist (1) Keywords: Dead space; Tracheal pressure; Carbon dioxide; Hypercapnia; Acute respiratory distress syndrome; Double-lumen tube Abstract: Objective Evaluation of ventilatory and circulatory effects with coaxial double-lumen tube ventilation for dead-space reduction as compared with standard endotracheal tube ventilation. Design Experimental study in a pig model of lung lavage induced acute lung injury. Setting University research laboratory. Measurements and results Tidal volumes of 6, 8 and 10 ml/kg body weight with a set respiratory rate of 20 breaths per minute were used in a random order with both double-lumen ventilation and standard endotracheal tube ventilation. Measurements of ventilatory and circulatory parameters were obtained after steady state at each experimental stage. With a tidal volume of 6 ml/kg, PaCO.sub.2 was reduced from 10.9 kPa (95% CI 9.0--12.9) with a standard endotracheal tube to 8.2 kPa (95% CI 7.0--9.4) with double-lumen ventilation. This corresponds to a reduction in carbon dioxide levels by 25%. At 6 ml/kg, pH increased from 7.17 (95% CI 7.09--7.24) with a standard endotracheal tube to 7.27 (95% CI 7.21--7.32) with double-lumen ventilation. Tracheal pressure was monitored continuously and no difference between single- or double-lumen ventilation was noted at corresponding levels of ventilation. There was no formation of auto-PEEP. Partial tube obstruction due to secretions was not observed during the experiments. Conclusions Coaxial double-lumen tube ventilation is an effective adjunct to reduce technical dead space. It attenuates hypercapnia and respiratory acidosis in a lung injury pig model. Author Affiliation: (1) Department of Anaesthesia and Intensive Care, Sahlgrenska University Hospital, S-413 45, Gothenburg, Sweden Article History: Registration Date: 26/01/2004 Received Date: 15/06/2003 Accepted Date: 22/01/2004 Online Date: 04/03/2004

Byline: Brigitte Fauroux (1), Bruno Louis (2), Nicholas Hart (3), Sandrine Essouri (4), Karl Leroux (5), Annick Clement (1), Michael Ian Polkey (3), Frederic Lofaso (6) Keywords: Non-invasive mechanical ventilation; Pressure support ventilation; Assist-control/volume-targeted ventilation; Back-up rate; Cystic fibrosis Abstract: Objective The aim of the study was to evaluate the effect of the back-up rate on respiratory effort during non-invasive mechanical ventilation. Design An in vitro study evaluated the inspiratory trigger in seven domiciliary ventilators. Then, a prospective, randomized, crossover trial compared the effect on respiratory effort of three different back-up rates during pressure support (PS) and assist-control/volume-targeted (AC/VT) ventilation. Setting A research unit and a tertiary referral pediatric center. Patients Ten patients with cystic fibrosis (CF). Interventions During the in vivo study, the back-up rate was progressively increased to the maximum that patients could tolerate (Fmax) and respiratory effort, as judged by pressure/time product of the diaphragm (PTPdi/min), was compared between the two ventilatory modes. Results Differences were observed between trigger pressure, trigger time delay, trigger pressure/time product and the slope between flow and pressure in the seven ventilators. PS and AC/VT ventilation were associated with a decrease in respiratory effort (PTPdi/min was 518+-172, 271+-119 and 291+-138 cm[H.sub.2]O . s.sup.-1 . min.sup.-1, for spontaneous breathing, PS and AC/VT ventilation, respectively, p=0.05). During the two modes, increasing the back-up rate to Fmax resulted in a greater reduction in PTPdi/min (p=0.001), which was more pronounced during AC/VT ventilation, due to the automatic adjustment of the inspiratory/expiratory time ratio. Conclusions Increasing the back-up rate during PS and AC/VT ventilation decreases respiratory effort in young patients with CF, but this effect was more marked with AC/VT ventilation. Author Affiliation: (1) Pediatric Pulmonary Department and INSERM 213, Armand Trousseau Hospital, Assistance Publique--Hopitaux de Paris, 28 avenue du Docteur Arnold Netter, 75012, Paris, France (2) INSERM U 492, Faculte de Medecine de Creteil, 8 rue du General Sarrail, 94010, Creteil, France (3) Respiratory Muscle Laboratory, Royal Brompton Hospital, Fulham Road, SW3 6NP, London, England (4) Pediatric Intensive Care Unit, Bicetre Hospital, Assistance Publique--Hopitaux de Paris, 78 rue du General Leclerc, 94270, Kremlin Bicetre, France (5) ADEP Assistance, 7 rue Voltaire, 92800, Puteaux, France (6) Physiology Department, Raymond Poincare Hospital, Assistance Publique--Hopitaux de Paris , 104 rue Raymond Poincare, 92380, Garches, France Article History: Registration Date: 05/12/2003 Received Date: 06/06/2003 Accepted Date: 01/12/2003 Online Date: 16/01/2004 Article note: This study was supported with grants from Vaincre la Mucoviscidose (VLM), the Comite National contre les Maladies Respiratoires (CNMR) and the Societe de Pneumologie de Langue Francaise (SPLF). Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00134-003-2126-z

Byline: Marco Piastra (1), Massimo Antonelli (2), Antonio Chiaretti (1), Giancarlo Polidori (1), Lorenzo Polidori (2), Giorgio Conti (2) Keywords: Acute respiratory failure; Non-invasive ventilation; Acute leukemia; Helmet interface; Child Abstract: Objective To evaluate the feasibility of non-invasive ventilation (NIV) through a new interface--the helmet--in the treatment of acute respiratory failure (ARF) in hematologic children. Design and setting Observational, non-randomized report of four consecutive cases. Pediatric Intensive Care Unit in a university hospital. Patients and methods Four consecutive females (aged 9--17 years) affected by acute leukemia (3 acute lymphocytic leukemia [ALL], 1 acute myeloid leukemia [AML]) and with hypoxemic ARF (defined by severe dyspnea at rest, respiratory rate >30 breaths/min, PaO.sub.2:FiO.sub.2 Results We evaluated the effect of pressure support ventilation delivered by helmet on blood gases, respiratory rate, hemodynamics, patient tolerance, complication rate and outcome. An improvement of oxygenation was uniformly observed within the first 3 h after admission. The helmet was well tolerated by all children. No complication was observed. Two patients were discharged from the PICU in stable clinical conditions, whereas the remaining two children overcame the respiratory distress but had non-respiratory complications and eventually died. Conclusion Non-invasive ventilation via the helmet can offer effective ventilatory support and improve gas exchange in the treatment of ARF in pediatric hematologic patients. As already shown in adults, NIV may decrease the risk of life-threatening complications associated with invasive mechanical ventilation (MV), also in children with hematologic malignancies moreover, it offers the possibility of an earlier approach to respiratory failure in this patient subset. Author Affiliation: (1) Pediatric Intensive Care Unit, Gemelli Policlinic, Catholic University Medical School, Largo Gemelli 8, 00168, Rome, Italy (2) Intensive Care Unit, Department of Anesthesiology and Intensive Care, Gemelli Policlinic, Catholic University Medical School, Largo Gemelli 8, 00168, Rome, Italy Article History: Registration Date: 19/11/2003 Received Date: 22/04/2003 Accepted Date: 14/11/2003 Online Date: 13/01/2004

Byline: Wolfram Burkhardt (1), Hans Proquitte (1), Susann Krause (1), Roland R. Wauer (1), Mario Rudiger (1) Keywords: Animal model; Fluorocarbons; Liquid ventilation; Near-infrared spectroscopy; Oxygen; Artificial ventilation Abstract: Objective To measure the impact of changes in the fraction of inspired oxygen (FiO.sub.2) on systemic and cerebral oxygen supply in gas and liquid ventilated healthy animals. Design Interventional prospective animal study. Setting University research laboratory. Participants Ten healthy, new-born piglets. Interventions Variations in FiO.sub.2 during conventional mechanical ventilation (CMV) followed by partial liquid ventilation (PLV) with two different filling volumes of PF 5080 (10 vs. 30 ml/kg). Measurements and results Arterial blood gases were obtained 15 min after changing FiO.sub.2 and concentrations of cerebral oxygenated and total hemoglobin were determined with near infrared spectroscopy. During CMV an increase in FiO.sub.2 1.0 was associated with a constant rise in PaO.sub.2 but only a small increase in the cerebral concentration of oxygenated Hb. Initiation of PLV (at FiO.sub.2 of 1.0) caused a rapid drop in PaO.sub.2 towards values that were similar to CMV at FiO.sub.2 of 0.5. At FiO.sub.2 of 0.5 a reduction in oxygenated Hb was found in the 30 ml/kg filling group. Complete filling of the lungs with PFC caused a significant drop in total cerebral Hb concentration. Conclusions According to our data, PLV in healthy lungs should be performed with a FiO.sub.2 of 1.0 and a small filling volume to avoid deterioration in cerebral oxygen supply. Author Affiliation: (1) Clinic of Neonatology, Charite-Mitte, Schumannstrasse 20, 10098, Berlin, Germany Article History: Registration Date: 06/11/2003 Received Date: 28/03/2003 Accepted Date: 31/10/2003 Online Date: 14/01/2004 Article note: Financial support: The study was supported by a grant of German Ministry of Education and Research (BMBF 'Perinatale Lunge-01ZZ9511). NIRO 300 was kindly supplied by Hamamatsu Germany.

Byline: Mauo-Ying Bien (1,4), Shu-Shya Hseu (2), Huey-Wen Yien (2), Benjamin Ing-Tiau Kuo (3), Yu-Ting Lin (2), Jia-Horng Wang (4), Yu Ru Kou (1) Keywords: Respiratory center; Postoperative care; Sepsis syndrome; Ventilators, mechanical; Ventilator weaning; Receiver operating characteristic curve Abstract: Objective To investigate whether breathing pattern variability can serve as a potential weaning predictor for postoperative patients recovering from systemic inflammatory response syndrome (SIRS). Design and setting A prospective measurement of retrospectively analyzed breathing pattern variability in a surgical intensive care unit. Patients Seventy-eight mechanically ventilated SIRS patients who had undergone abdominal surgery were included when they were ready for weaning. They were divided into success (n=57) and failure (n=21) groups based upon their weaning outcome. Measurements and results Before weaning, tidal volume, total breath duration, inspiratory time, expiratory time, and peak inspiratory flow were continuously monitored for 30 min, while patients received 5 cm[H.sub.2]O pressure support weaning trial. After the patients successfully completed the trial, they were extubated. Successful weaning was defined as patients free from the ventilator for over 48 h, whereas a weaning failure was considered as reinstitution of mechanical ventilation within 48 h of extubation. The coefficient of variation and two values of standard deviation (SD.sub.1 and SD.sub.2 indicators of the dispersion of data points in the plot) obtained from the Poincare plot of five respiratory parameters in the failure group were significantly lower than those in the success group. The area under the receiver operating characteristic curve of these variability indices was within the range of 0.73--0.80, indicating the accuracy of prediction. Conclusions Small breathing pattern variability is associated with a high incidence of weaning failure in postoperative patients recovering from SIRS, and this variability may potentially serve as a weaning predictor. Author Affiliation: (1) Institute of Physiology, School of Medicine, National Yang-Ming University, 11221, Taipei, Taiwan, Republic of China (2) Department of Anesthesiology, Department of Surgical Critical Care Unit, Taipei Veterans General Hospital, 11217, Taipei, Taiwan, Republic of China (3) Laboratory of Epidemiology and Biostatistics, Taipei Veterans General Hospital, 11217, Taipei, Taiwan, Republic of China (4) Department of Respiratory Therapy, Taipei Veterans General Hospital, 11217, Taipei, Taiwan, Republic of China Article History: Registration Date: 23/10/2003 Received Date: 26/05/2003 Accepted Date: 20/10/2003 Online Date: 26/11/2003 Article note: Supported by grants NSC91-2320-B-010-046-M59 and NSC91-2314-B-075-067 from the National Science Council, Taiwan, grant VGH-91-095 from Taipei Veterans General Hospital, Taiwan, and grant VTY92-P5-30 Electronic Supplementary Material Supplementary Material is available in the online version of this article at http://dx.doi.org/10.1007/s00134-2073-8

Byline: Josep Masip (1), Joaquim Paez (1), Montserrat Merino (1), Sandra Parejo (1), Francisco Vecilla (1), Clara Riera (1), Araceli Rios (1), Joan Sabater (1), Josep Ballus (1), J. Padro (1) Keywords: Intubation; Acute pulmonary edema; Noninvasive ventilation Abstract: Objective Noninvasive ventilation may reduce the endotracheal intubation rate in patients with acute cardiogenic pulmonary edema. However, criteria for selecting candidates for this technique are not well established. We analyzed a cohort of patients with severe acute cardiogenic pulmonary edema managed by conventional therapy to identify risk factors for intubation. These factors were used as guide for indications for noninvasive ventilation. Design and setting Observational cohort registry in the ICU and emergency and cardiology departments in a community teaching hospital. Patients 110 consecutive patients with acute cardiogenic pulmonary edema, 80 of whom received conventional oxygen therapy. Interventions Physiological measurements and blood gas samples registered upon admission. Measurements and results Twenty-one patients (26%) treated with conventional oxygen therapy needed intubation. Acute myocardial infarction, pH below 7.25, low ejection fraction ( Conclusions Patients with pH less than 7.25 or systolic blood pressure less than 180 mmHg associated with hypercapnia should be promptly considered for noninvasive ventilation. With this strategy about 40% of the patients would be initially treated with this technique, which would involve nearly 90% of the patients that require intubation. Author Affiliation: (1) ICU Department, Hospital Dos de Maig, Consorci Sanitari Integral, Dos de Maig 305, 08025, Barcelona, Spain Article History: Received Date: 05/12/2002 Accepted Date: 11/06/2003 Online Date: 10/09/2003

Byline: NicolA2 Patroniti (1), Giuseppe Foti (1), Annamaria Manfio (1), Anna Coppo (1), Giacomo Bellani (1), Antonio Pesenti (1) Keywords: Continuous positive airway pressure; Head helmet; Face mask; Hypoxemic respiratory failure; Healthy volunteers Abstract: Objective To assess selected physiological effects of non-invasive continuous positive airway pressure delivered by head helmet (CPAP.sub.H), a special interface device designed to completely contain the head of the patient, compared to face mask (CPAP.sub.M). Design Randomized physiological study. Setting University research laboratory. Patients Eight healthy volunteers. Intervention Continuous positive airway pressure delivered by face mask and CPA[P.sub.H ]in random order. Three gas flow rates (20-30-40 l/min and 30-45-60 l/min, respectively, for CPAP.sub.M and CPAP.sub.H) and four CPAP levels (0-5-10-15 cm[H.sub.2]O) were employed in a randomized sequence. Measurements and results In each patient we monitored airway pressure, esophageal pressure, expiratory flow, and inspiratory and expiratory CO.sub.2 concentration. End-expiratory lung volume changes from CPAP 0 were measured by inductance plethysmography. The application of increased levels of CPAP resulted in a significant increase in end-expiratory lung volume, similar for CPAP.sub.H and CPAP.sub.M. Inspiratory changes of airway pressure were comparable for the two CPAP modes. Inspiratory CO.sub.2 concentration was higher during CPAP.sub.H (significantly decreased at increased gas flow rates), compared to CPAP.sub.M. Conclusions Continuous positive airway pressure delivered by head helmet is as effective as CPAP.sub.M in increasing end-expiratory lung volume and in compensating for airway pressure changes without the need of a reservoir bag. Higher gas flow rates are necessary to maintain a relatively low inspiratory CO.sub.2 concentration. Author Affiliation: (1) Department of Anesthesia and Intensive Care, Ospedale San Gerardo Nuovo dei Tintori, University of Milano-Bicocca, Via Donizetti 106, 20052, Monza (Milano), Italy Article History: Received Date: 17/09/2002 Accepted Date: 30/06/2003 Online Date: 28/08/2003

Byline: Natalie Anton (1), Kenneth M. Joffe (1), Ari R. Joffe (1) Keywords: Acute respiratory distress syndrome; High-frequency ventilation; Mechanical ventilation; Pediatrics; Respiratory failure; Ventilators, mechanical Abstract: Objective To (a) describe the experience with high-frequency oscillation (HFO) in children with acute respiratory distress syndrome (ARDS) unresponsive to conventional ventilation (b) compare observed survival to that predicted by pediatric mortality scores and (c) determine if oxygenation index changes during HFO can predict survival. Design Retrospective, observational study. Setting A university hospital pediatric intensive care unit. Patients Nineteen children with ARDS (PaO.sub.2/FIO.sub.2 Interventions None. Measurements and results The following were recorded: demographic, arterial blood gas and ventilator variables at the time points 0, 6, 12 and 24 h after the start of HFO PRISM in the first 24 h of admission and pediatric respiratory failure and multiple organ system failure scores on the day of starting HFO. The mortality rate was 26% (5/19). The survival was better than predicted by the Pediatric Respiratory Failure score (p0.25). There was no significant change in oxygenation index over the first 24 h (p>0.18). Of patients with an initial oxygenation index higher than 20 who did not have at least a 20% reduction in oxygenation index by the time 6 h, 6/9 (67%) survived (sensitivity 75%, specificity 57%). Conclusions Survival in pediatric ARDS patients treated with HFO could not be predicted using several outcome scores or the oxygenation index (in the first 24 h). Survival was significantly better than predicted by the Pediatric Respiratory Failure score. A prospective randomized controlled trial of HFO in ARDS is warranted. Author Affiliation: (1) Pediatric Intensive Care Unit, Department of Pediatrics , University of Alberta, Edmonton, Alberta, T6G 2B7, Canada Article History: Received Date: 28/12/2000 Accepted Date: 08/08/2001 Online Date: 16/08/2003

Byline: Pinchas Halpern (1), Miri Y. Neufeld (2), Kobi Sade (3), Aviel Silbiger (4), Oded Szold (4), Natan M. Bornstein (2), Patrick Sorkine (4) Keywords: Doppler; Ultrasound; Transcranial; Middle cerebral artery; Carbon dioxide; Ventilation Abstract: Objective To define the changes in middle cerebral artery flow velocity (Vmca) and the electroencephalogram (EEG) during rapid reduction in arterial carbon dioxide (PCO.sub.2) from acute hypercapnia. Design Human volunteer study. Setting University-affiliated hospital experimental laboratory. Participants Nine healthy volunteers aged 25--35 years. Interventions Subjects rebreathed exhaled gas from a bag pre-filled with 5% carbon dioxide (CO.sub.2) in oxygen, up to an end-tidal CO.sub.2 of 10% or to the limit of discomfort, when they were disconnected. Measurements and results Middle cerebral artery blood flow velocity was continuously measured by transcranial Doppler ultrasound, quantitative EEG was recorded and hemodynamics were monitored non-invasively. Vmca closely correlated with end-tidal CO.sub.2 changes (r=0.65, p Conclusions These findings demonstrate the rapid changes occurring in cerebral blood flow during rapid declines in arterial CO.sub.2 and the consequent potential for producing brain ischemia and hemodynamic alterations if inadvertent hyperventilation occurs following institution of mechanical ventilation for acute hypercapnia. Author Affiliation: (1) Department of Emergency Medicine, Tel Aviv Sourasky Medical Center and the Sackler Faculty of Medicine , Tel Aviv University, 6 Weizman Street, 64239, Tel Aviv, Israel (2) Department of Neurology, Tel Aviv Sourasky Medical Center and the Sackler Faculty of Medicine, Tel Aviv University, 6 Weizman Street, 64239, Tel Aviv, Israel (3) Department of Pulmonary Medicine and Allergy, Tel Aviv Sourasky Medical Center and the Sackler Faculty of Medicine, Tel Aviv University, 6 Weizman Street, 64239, Tel Aviv, Israel (4) Department of Anesthesiology & Critical Care Medicine, Tel Aviv Sourasky Medical Center and the Sackler Faculty of Medicine, Tel Aviv University, 6 Weizman Street, 64239, Tel Aviv, Israel Article History: Received Date: 06/02/2003 Accepted Date: 23/06/2003 Online Date: 02/08/2003