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Background: Non-invasive ventilation (NIV) has been increasingly used in COVID-19 patients. The limited physiological monitoring and the unavailability of respiratory mechanic measures, usually obtainable during invasive ventilation, is a limitation of NIV for ARDS and COVID-19 patients management., Objectives: This pilot study was aimed to evaluate the feasibility of non-invasively monitoring respiratory mechanics by oscillometry in COVID-19 patients with moderate-severe acute respiratory distress syndrome (ARDS) receiving NIV., Method: 15 COVID-19 patients affected by moderate-severe ARDS at the RICU (Respiratory Intensive Care Unit) of the University hospital of Cattinara, Trieste, Italy were recruited. Patients underwent oscillometry tests during short periods of spontaneous breathing between NIV sessions., Results: Oscillometry proved to be feasible, reproducible and well-tolerated by patients. At admission, 8 of the 15 patients showed oscillometry parameters within the normal range which further slightly improved before discharge. At discharge, four patients had still abnormal respiratory mechanics, not exclusively linked to pre-existing respiratory comorbidities. Lung mechanics parameters were not correlated with oxygenation., Conclusions: Our results suggest that lung mechanics provide complementary information for improving patients phenotyping and personalisation of treatments during NIV in COVID 19 patients, especially in the presence of respiratory comorbidities where deterioration of lung mechanics may be less coupled with changes in oxygenation and more difficult to identify. Oscillometry may provide a valuable tool for monitoring lung mechanics in COVID 19 patients receiving NIV., Competing Interests: Dr Dellaca’ reports grants and other from Restech, personal fees from Philips Healthcare, outside the submitted work. In addition, Dr Dellaca’ has a patent on the detection of EFL by FOT with royalties paid to Philips Respironics and Restech Srl, a patent on monitoring lung volume recruitment by FOT with royalties paid to Vyaire, and a patent on early detection of exacerbations by home monitoring of FOT with royalties paid to Restech and is co-founder and shareholder of Restech Srl, a spin-off company of the Politecnico di Milano University producing medical devices for lung function testing based on FOT. In details: System and methods for the automatic detection of expiratory flow limitation. Application number PCT/EP03/06119. International filing date 10/06/2003. Apparatus for respiratory support and non-invasive detection of alveolar derecruitment for patients suffering from respiratory failure. Application Number: PCT/EP2007/059534, publication date 20/03/2008. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Background: A correlation between unsuccessful noninvasive ventilation (NIV) and poor outcome has been suggested in de-novo Acute Respiratory Failure (ARF) patients. Consequently, it is of paramount importance to identify accurate predictors of NIV outcome. The aim of our preliminary study is to evaluate the Diaphragmatic Thickening Fraction (DTF) and the respiratory rate/DTF ratio as predictors of NIV outcome in de-novo ARF patients., Methods: Over 36 months, we studied patients admitted to the emergency department with a diagnosis of de-novo ARF and requiring NIV treatment. DTF and respiratory rate/DTF ratio were measured by 2 trained operators at baseline, at 1, 4, 12, 24, 48, 72 and 96 h of NIV treatment and/or until NIV discontinuation or intubation. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the ability of DTF and respiratory rate/DTF ratio to distinguish between patients who were successfully weaned and those who failed., Results: Eighteen patients were included. We found overall good repeatability of DTF assessment, with Intra-class Correlation Coefficient (ICC) of 0.82 (95% confidence interval 0.72-0.88). The cut-off values of DTF for prediction of NIV failure were < 36.3% and < 37.1% for the operator 1 and 2 (p < 0.0001), respectively. The cut-off value of respiratory rate/DTF ratio for prediction of NIV failure was > 0.6 for both operators (p < 0.0001)., Conclusion: DTF and respiratory rate/DTF ratio may both represent valid, feasible and noninvasive tools to predict NIV outcome in patients with de-novo ARF. Trial registration ClinicalTrials.gov Identifier: NCT02976233, registered 26 November 2016.

During the COVID-19 pandemic, the Oasi Research Institute of Troina (Italy) became an important hotbed for infection; in fact, 109 patients with different levels of Intellectual Disability (ID) tested positive for COVID-19. The procedures and interventions put in place at the Oasi Research Institute due to the COVID-19 pandemic are exhaustively reported in this paper. The description of the clinical procedures as well as remote/in person psychological support services provided to people with ID and their families are here divided into three different sections: Phase I (or Acute phase), Phase II (or Activity planning), and Phase III (or Activity consolidation). In each section, the main psycho-pathological characteristics of patients, the reactions of family members and the multidisciplinary interventions put in place are also described., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Introduction: Little is still known about the prognostic impact of incident arrhythmias in hospitalized patients with COVID-19. The aim of this study was to evaluate the incidence and predictors of sustained tachyarrhythmias in hospitalized patients with COVID-19, and their potential association with disease severity and in-hospital mortality., Materials and Methods: This was a retrospective multicenter observation study including consecutive patients with laboratory confirmed COVID-19 admitted to emergency department of ten Italian Hospitals from 15 February to 15 March 2020. The prevalence and the type of incident sustained arrhythmias have been collected. The correlation between the most prevalent arrhythmias and both baseline characteristics and the development of ARDS and in-hospital mortality has been evaluated., Results: 414 hospitalized patients with COVID-19 (66.9 ± 15.0 years, 61.1% male) were included in the present study. During a median follow-up of 28 days (IQR: 12-45), the most frequent incident sustained arrhythmia was AF (N: 71; 17.1%), of which 50 (12.1%) were new-onset and 21 (5.1%) were recurrent, followed by VT (N: 14, 3.4%) and supraventricular arrhythmias (N: 5, 1.2%). Incident AF, both new-onset and recurrent, did not affect the risk of severe adverse events including ARDS and death during hospitalization; in contrast, incident VT significantly increased the risk of in-hospital mortality (RR: 2.55; P: .003)., Conclusions: AF is the more frequent incident tachyarrhythmia; however, it not seems associated to ARDS development and death. On the other hand, incident VT is a not frequent but independent predictor of in-hospital mortality among hospitalized COVID-19 patients., (© 2020 Stichting European Society for Clinical Investigation Journal Foundation. Published by John Wiley & Sons Ltd.)

Purpose: To investigate whether COVID-19-ARDS differs from all-cause ARDS., Methods: Thirty-two consecutive, mechanically ventilated COVID-19-ARDS patients were compared to two historical ARDS sub-populations 1:1 matched for PaO 2 /FiO 2 or for compliance of the respiratory system. Gas exchange, hemodynamics and respiratory mechanics were recorded at 5 and 15 cmH 2 O PEEP. CT scan variables were measured at 5 cmH 2 O PEEP., Results: Anthropometric characteristics were similar in COVID-19-ARDS, PaO 2 /FiO 2 -matched-ARDS and Compliance-matched-ARDS. The PaO 2 /FiO 2 -matched-ARDS and COVID-19-ARDS populations (both with PaO 2 /FiO 2 106 ± 59 mmHg) had different respiratory system compliances (Crs) (39 ± 11 vs 49.9 ± 15.4 ml/cmH 2 O, p = 0.03). The Compliance-matched-ARDS and COVID-19-ARDS had similar Crs (50.1 ± 15.7 and 49.9 ± 15.4 ml/cmH 2 O, respectively) but significantly lower PaO 2 /FiO 2 for the same Crs (160 ± 62 vs 106.5 ± 59.6 mmHg, p < 0.001). The three populations had similar lung weights but COVID-19-ARDS had significantly higher lung gas volume (PaO 2 /FiO 2 -matched-ARDS 930 ± 644 ml, COVID-19-ARDS 1670 ± 791 ml and Compliance-matched-ARDS 1301 ± 627 ml, p < 0.05). The venous admixture was significantly related to the non-aerated tissue in PaO 2 /FiO 2 -matched-ARDS and Compliance-matched-ARDS (p < 0.001) but unrelated in COVID-19-ARDS (p = 0.75), suggesting that hypoxemia was not only due to the extent of non-aerated tissue. Increasing PEEP from 5 to 15 cmH 2 O improved oxygenation in all groups. However, while lung mechanics and dead space improved in PaO 2 /FiO 2 -matched-ARDS, suggesting recruitment as primary mechanism, they remained unmodified or worsened in COVID-19-ARDS and Compliance-matched-ARDS, suggesting lower recruitment potential and/or blood flow redistribution., Conclusions: COVID-19-ARDS is a subset of ARDS characterized overall by higher compliance and lung gas volume for a given PaO 2 /FiO 2 , at least when considered within the timeframe of our study.

Aim: To investigate the prevalence and prognostic impact of right heart failure and right ventricular-arterial uncoupling in Corona Virus Infectious Disease 2019 (COVID-19) complicated by an Acute Respiratory Distress Syndrome (ARDS)., Methods: Ninety-four consecutive patients (mean age 64 years) admitted for acute respiratory failure on COVID-19 were enrolled. Coupling of right ventricular function to the pulmonary circulation was evaluated by a comprehensive trans-thoracic echocardiography with focus on the tricuspid annular plane systolic excursion (TAPSE) to systolic pulmonary artery pressure (PASP) ratio RESULTS: The majority of patients needed ventilatory support, which was noninvasive in 22 and invasive in 37. There were 25 deaths, all in the invasively ventilated patients. Survivors were younger (62 ± 13 vs. 68 ± 12 years, p = 0.033), less often overweight or usual smokers, had lower NT-proBNP and interleukin-6, and higher arterial partial pressure of oxygen (PaO 2 )/fraction of inspired O 2 (FIO 2 ) ratio (270 ± 104 vs. 117 ± 57 mmHg, p < 0.001). In the non-survivors, PASP was increased (42 ± 12 vs. 30 ± 7 mmHg, p < 0.001), while TAPSE was decreased (19 ± 4 vs. 25 ± 4 mm, p < 0.001). Accordingly, the TAPSE/PASP ratio was lower than in the survivors (0.51 ± 0.22 vs. 0.89 ± 0.29 mm/mmHg, p < 0.001). At univariate/multivariable analysis, the TAPSE/PASP (HR: 0.026; 95%CI 0.01-0.579; p: 0.019) and PaO 2 /FIO 2 (HR: 0.988; 95%CI 0.988-0.998; p: 0.018) ratios were the only independent predictors of mortality, with ROC-determined cutoff values of 159 mmHg and 0.635 mm/mmHg, respectively., Conclusions: COVID-19 ARDS is associated with clinically relevant uncoupling of right ventricular function from the pulmonary circulation; bedside echocardiography of TAPSE/PASP adds to the prognostic relevance of PaO 2 /FIO 2 in ARDS on COVID-19.

Background: Whether respiratory physiology of COVID-19-induced respiratory failure is different from acute respiratory distress syndrome (ARDS) of other etiologies is unclear. We conducted a single-center study to describe respiratory mechanics and response to positive end-expiratory pressure (PEEP) in COVID-19 ARDS and to compare COVID-19 patients to matched-control subjects with ARDS from other causes., Methods: Thirty consecutive COVID-19 patients admitted to an intensive care unit in Rome, Italy, and fulfilling moderate-to-severe ARDS criteria were enrolled within 24 h from endotracheal intubation. Gas exchange, respiratory mechanics, and ventilatory ratio were measured at PEEP of 15 and 5 cmH 2 O. A single-breath derecruitment maneuver was performed to assess recruitability. After 1:1 matching based on PaO 2 /FiO 2 , FiO 2 , PEEP, and tidal volume, COVID-19 patients were compared to subjects affected by ARDS of other etiologies who underwent the same procedures in a previous study., Results: Thirty COVID-19 patients were successfully matched with 30 ARDS from other etiologies. At low PEEP, median [25th-75th percentiles] PaO 2 /FiO 2 in the two groups was 119 mmHg [101-142] and 116 mmHg [87-154]. Average compliance (41 ml/cmH 2 O [32-52] vs. 36 ml/cmH 2 O [27-42], p = 0.045) and ventilatory ratio (2.1 [1.7-2.3] vs. 1.6 [1.4-2.1], p = 0.032) were slightly higher in COVID-19 patients. Inter-individual variability (ratio of standard deviation to mean) of compliance was 36% in COVID-19 patients and 31% in other ARDS. In COVID-19 patients, PaO 2 /FiO 2 was linearly correlated with respiratory system compliance (r = 0.52 p = 0.003). High PEEP improved PaO 2 /FiO 2 in both cohorts, but more remarkably in COVID-19 patients (p = 0.005). Recruitability was not different between cohorts (p = 0.39) and was highly inter-individually variable (72% in COVID-19 patients and 64% in ARDS from other causes). In COVID-19 patients, recruitability was independent from oxygenation and respiratory mechanics changes due to PEEP., Conclusions: Early after establishment of mechanical ventilation, COVID-19 patients follow ARDS physiology, with compliance reduction related to the degree of hypoxemia, and inter-individually variable respiratory mechanics and recruitability. Physiological differences between ARDS from COVID-19 and other causes appear small.

Objectives: Severe cases of coronavirus disease 2019 develop the acute respiratory distress syndrome, requiring admission to the ICU. This study aimed to describe specific pathophysiological characteristics of acute respiratory distress syndrome from coronavirus disease 2019., Design: Prospective crossover physiologic study., Setting: ICU of a university-affiliated hospital from northern Italy dedicated to care of patients with confirmed diagnosis of coronavirus disease 2019., Patients: Ten intubated patients with acute respiratory distress syndrome and confirmed diagnosis of coronavirus disease 2019., Interventions: We performed a two-step positive end-expiratory pressure trial with change of 10 cm H2O in random order., Measurements and Main Results: At each positive end-expiratory pressure level, we assessed arterial blood gases, respiratory mechanics, ventilation inhomogeneity, and potential for lung recruitment by electrical impedance tomography. Potential for lung recruitment was assessed by the recently described recruitment to inflation ratio. In a subgroup of seven paralyzed patients, we also measured ventilation-perfusion mismatch at lower positive end-expiratory pressure by electrical impedance tomography. At higher positive end-expiratory pressure, respiratory mechanics did not change significantly: compliance remained relatively high with low driving pressure. Oxygenation and ventilation inhomogeneity improved but arterial CO2 increased despite unchanged respiratory rate and tidal volume. The recruitment to inflation ratio presented median value higher than previously reported in acute respiratory distress syndrome patients but with large variability (median, 0.79 [0.53-1.08]; range, 0.16-1.40). The FIO2 needed to obtain viable oxygenation at lower positive end-expiratory pressure was significantly correlated with the recruitment to inflation ratio (r = 0.603; p = 0.05). The ventilation-perfusion mismatch was elevated (median, 34% [32-45%] of lung units) and, in six out of seven patients, ventilated nonperfused units represented a much larger proportion than perfused nonventilated ones., Conclusions: In patients with acute respiratory distress syndrome from coronavirus disease 2019, potential for lung recruitment presents large variability, while elevated dead space fraction may be a specific pathophysiological trait. These findings may guide selection of personalized mechanical ventilation settings.

Purpose: Aim of this study was to evaluate the effect of acute respiratory distress syndrome (ARDS) duration on gas-exchange, respiratory mechanics, specific lung elastance and mechanical power., Materials and Methods: In a single center prospective study 28 ARDS patients (66.4 ± 10.0 years, BMI 23.6[21.3-28.8] kg/m 2 , PaO 2 /FiO 2 148.9[99.6-173.5]) who still presented ARDS criteria after 7-days of mechanical ventilation were studied in early and persistent phase of the disease (day-1 and after 7-days). Each patient underwent PEEP trial at 5-15 cmH 2 O in both phases., Results: At both PEEP levels the PaO 2 was similar in both phases (early: 70.7[65.1-84.4] vs 102.0[85.5-131.8] mmHg; persistent 70.7[63.0-76.2] vs 97.4[86.5-117.1] mmHg, 5-15 cmH 2 O respectively), the PaCO 2 was significantly higher in the persistent phase at both PEEP levels (early 50.6 ± 10.2 vs 52.1 ± 10.5 mmHg; persistent 57.7 ± 13.4 vs 56.9 ± 12.8 mmHg). Specific lung elastance was not different in the early compared to the persistent phase 12.5 ± 3.1 vs 12.2 ± 3.8 cmH 2 O. The mechanical power normalized for the functional residual capacity increased with PEEP and was similar in both phases (early 23.4[12.8-32.8] vs 34.3[25.3-47.9], persistent 16.3[10.9-24.1] vs 26.7[19.9-46.0] J/min/L, 5-15 cmH 2 O respectively)., Conclusions: The persistent phase of ARDS for 7-days did not affect the respiratory mechanics while significantly impaired the PaCO 2 exchange., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: The pressure-volume (P-V) curve has been suggested as a bedside tool to set mechanical ventilation; however, it reflects a global behavior of the lung without giving information on the regional mechanical properties. Regional P-V (PVr) curves derived from electrical impedance tomography (EIT) could provide valuable clinical information at bedside, being able to explore the regional mechanics of the lung. In the present study, we hypothesized that regional P-V curves would provide different information from those obtained from global P-V curves, both in terms of upper and lower inflection points. Therefore, we constructed pressure-volume curves for each pixel row from non-dependent to dependent lung regions of patients affected by acute hypoxemic respiratory failure (AHRF) and acute respiratory distress syndrome (ARDS)., Methods: We analyzed slow-inflation P-V maneuvers data from 12 mechanically ventilated patients. During the inflation, the pneumotachograph was used to record flow and airway pressure while the EIT signals were recorded digitally. From each maneuver, global respiratory system P-V curve (PVg) and PVr curves were obtained, each one corresponding to a pixel row within the EIT image. PVg and PVr curves were fitted using a sigmoidal equation, and the upper (UIP) and lower (LIP) inflection points for each curve were mathematically identified; LIP and UIP from PVg were respectively called LIPg and UIPg. From each measurement, the highest regional LIP (LIPr MAX ) and the lowest regional UIP (UIPr MIN ) were identified and the pressure difference between those two points was defined as linear driving pressure (ΔP LIN )., Results: A significant difference (p < 0.001) was found between LIPr MAX (15.8 [9.2-21.1] cmH 2 O) and LIPg (2.9 [2.2-8.9] cmH 2 O); in all measurements, the LIPr MAX was higher than the corresponding LIPg. We found a significant difference (p < 0.005) between UIPr MIN (30.1 [23.5-37.6] cmH 2 O) and UIPg (40.5 [34.2-45] cmH 2 O), the UIPr MIN always being lower than the corresponding UIPg. Median ΔP LIN was 12.6 [7.4-20.8] cmH 2 O and in 56% of cases was < 14 cmH 2 O., Conclusions: Regional inflection points derived by EIT show high variability reflecting lung heterogeneity. Regional P-V curves obtained by EIT could convey more sensitive information than global lung mechanics on the pressures within which all lung regions express linear compliance., Trial Registration: Clinicaltrials.gov, NCT02907840 . Registered on 20 September 2016.

Purpose: Our aim was to evaluate the evolution of 20 patients with H1N1 pneumonia, focusing our attention on patients with severe clinical and radiological findings who developed post-acute respiratory distress syndrome (post-ARDS) pulmonary fibrosis., Materials and Methods: Twenty adult patients (nine women and 11 men; mean age 43.5 ± 16.4 years) with a diagnosis of H1N1 infection confirmed by pharyngeal swab came to our attention from September to November 2009 and were followed up until September 2010. All patients were hospitalised in consideration of the severity of clinical findings, and all underwent chest X-ray. Twelve of them underwent at least one computed tomography (CT) scan of the chest., Results: In 75% of cases (15/20), there was complete resolution of the clinical and radiological findings. Twenty-five percent of patients (5/20) developed acute respiratory distress syndrome (ARDS), which progressed to predominantly peripheral pulmonary fibrosis in 10% (2/20; one died and one had late-onset pulmonary fibrosis, documented on day 68). Moreover, in one patient with a CT diagnosis of pulmonary fibrosis, we observed progressive regression of radiological findings over 4 months of follow-up., Conclusions: In patients with H1N1 pneumonia, post-ARDS pulmonary fibrosis is not a rare complication. Therefore, a CT scan should be performed in all patients with severe clinical findings. Our study demonstrated that in these patients, fibrosis could present a different spatial distribution and a different temporal trend, with delayed late onset; moreover, in one case, the signs of interstitial lung disease partially regressed over time. Therefore, CT should be considered not only in the diagnostic stage, but also during the follow-up.

Purpose: Transfer of severely hypoxic patients is a high-risk procedure. Extracorporeal membrane oxygenation (ECMO) allows safe transport of these patients to tertiary care institutions. Our ECMO transportation program was instituted in 2004; here we report results after 5 years of activity., Methods: This is a clinical observational study. Criteria for ECMO center activation were: potentially reversibile respiratory failure, PaO₂ <50 mmHg with FiO₂ >0.6 for >12 hours, PEEP >5 cmH₂0, Lung Injury Score (LIS) ≥3 or respiratory acidosis with pH <7.2, no intracranial bleeding, and no absolute contraindication to anticoagulation. If eligible, a skilled crew applied ECMO at the referral hospital. Transportation was performed with a specially equipped ambulance., Results: Sixteen patients were possible candidates for ECMO transfer. Two patients were excluded while 14 (mean±SD, age 35.4±18.6, SOFA 8.4±3.7, Oxygenation Index 43.7±13.4) were transported to our institution (distance covered 102±114 km, global duration of transport 589±186 minutes). Two patients improved after iNO-trial and were transferred and subsequently managed without ECMO. The remaining 12 patients were transferred on veno-venous ECMO with extracorporeal blood flow 2.7±1 L·min⁻¹, gas flow 3.8±1.8 L·min⁻¹, and FiO₂ 1. Data were recorded 30 minutes before and 60 minutes after initiation of ECMO. ECMO improved PCO₂ (75±23 vs. 53±9 mmHg, p<0.01) thus improving pH (7.28±0.13 vs. 7.39±0.05, p<0.01) and allowing a reduction in respiratory rate (35±14 vs. 10±4 breaths/min, p<0.01), minute ventilation (10.1±3.8 vs. 3.7±1.7 L·min⁻¹, p<0.01), and mean airway pressure (26±6.5 vs. 22±5 cmH₂O, p<0.01). No major clinical or technical complications were observed., Conclusions: ECMO effectively enabled high-risk ground transfer of severely hypoxic patients.

Background: Venovenous extracorporeal membrane oxygenation (VV-ECMO) is used in refractory acute respiratory distress syndrome where lung recovery is the primary goal. For its achievement, adequate extracorporeal blood flow and a maximal separation between oxygenated (inflow) and deoxygenated (outflow) blood flow are essential for reducing the recirculation phenomenon. We introduce the χ-configuration, a new cannulation strategy for VV-ECMO., Patients and Methods: We report our experience with 30 VV-ECMO consecutive patients: in 16 patients (group NS) we applied the χ-configuration, which consists of a particular right atrial cannula arrangement and a self-made modified inflow cannula, consisting of an outflow multihole venous cannula that was inserted percutaneously through the right femoral vein, into the right atrium, just below on the superior vena cava, and a self-made modified curved inflow cannula (inserted percutaneously through the right internal jugular vein) that, in its terminal segment, permitted the tip to be positioned close to the tricuspid valve. In 14 patients (group C) we applied the standard femoro-jugular VV-ECMO 2-cannula setting. In both groups, efficacy of blood oxygenation was obtained by gas-blood analysis, by blood samples obtained at arterial, central venous, and pulmonary artery lines, and by ECMO inflow and outflow lines. The recirculation fraction was obtained by a specific bedside formula., Results: No differences were noted between groups regarding the pre-ECMO patient characteristics. No complications during cannulation were recorded. In group NS, on-ECMO time, post-ECMO mechanical ventilation time, and ECMO overall results were significantly better than in group C. During high-flow VV-ECMO, pulmonary and systemic arterial oxygen saturation and arterial oxygen tension were significantly higher in group NS, and blood recirculation fraction was significantly lower., Conclusions: Our data indicate that χ-configuration can be safe, feasible, and more effective than conventional VV-ECMO. It permits near complete drainage of the desaturated blood and a preferential oxygenated blood inflow toward the tricuspid valve, resulting in a significant reduction of recirculation, thereby improving the patient's oxygenation. Our innovative strategy reduces on-ECMO and post-ECMO mechanical ventilation time, gives a faster and better pulmonary recovery, improves survival, and can reduce hospital costs., (Copyright © 2011 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.)

Objective: The pressure-volume (P/V) curve has been proposed as a tool to adjust the ventilatory settings in cases of acute respiratory distress syndrome (ARDS). The aim of this study was to test the influence of P/V tracing methodology on the presence and value of the upper inflection point (UIP)., Methods: In 13 medical ARDS patients, the interruption and the automated low flow inflation methods were compared while the patients were ventilated at conventional (10-12 ml/kg) and at low (5-6 ml/kg) tidal volume (Vt). Two levels of inspiratory flow and insufflation time were used (3 and 6 s)., Results: No significant difference in UIP was found between the static and the dynamic methods, whatever the flow used. At Vt 10-12 ml/kg, the static and dynamic UIPs were 22.4 +/- 4.4 cmH(2)O and 22.1 +/- 4.5 cmH(2)O ( p = 0.86), respectively; at Vt of 5-6 ml/kg, the static and dynamic UIPs were 26.6 +/- 4.1 cmH(2)O and 25.5 +/- 5 cmH(2)O ( p = 0.34), respectively. Significant differences in UIP were found, in the static and dynamic conditions, between the two levels of Vt ( p < 0.005): it was lower with the higher Vt, suggesting that UIP is dependent on previous tidal alveolar recruitment., Conclusion: Interruption and continuous flow techniques gave similar results, but the previous Vt influences the pressure value of the UIP.

Prone position was initially introduced in healthy anesthetized and paralyzed subjects for surgical specific reasons. Then, it was used during acute respiratory failure to improve gas exchange. The interest on prone position during ALI/ARDS progressively increased, even if the mechanisms leading to a respiratory improvement are not yet completely understood. In normal subjects, during anesthesia and paralysis, prone position determines a more homogeneous distribution of the gravitational gradient of alveolar inflation, a ventilation distributed towards the non dependent lung regions and a reverse of the gravitational distribution of regional perfusion, even if factors other than gravity are involved. Moreover, prone position causes, both in healthy subject and in obese patients, an improvement in oxygenation and in functional residual capacity without affecting respiratory system, lung and chest wall compliance. In ALI/ARDS patients, prone position lead to a reverse of the alveolar inflation and ventilation distribution, due to the reverse of hydrostatic pressure overlying lung parenchyma, the reverse of heart weight, and the changes in chest wall shape and mechanical properties. Little data are available for the modifications in regional lung perfusion. The possible mechanisms involved in oxygenation improvement during prone position in ALI/ARDS patients are: 1) increased lung volumes; 2) redistribution of lung perfusion; 3) recruitment of dorsal spaces with more homogeneous ventilation and perfusion distribution. From a clinical point of view, prone position seems to be a very promising treatment for ALI/ARDS, even if its use is not yet a standard clinical practice. We have recently finished a randomized-controlled trial in order to investigate the clinical impact of this procedure. In the preliminary phase of the study performed in 35 Italian Intensive Care Units, we studied, from 1996 to 1998, 73 patients with a PaO2/FiO2 of 123 +/- 42 and a SAPS (Simplified Acute Physiology Score) of 38 +/- 11. After the first hour of prone positioning, the PaO2/FiO2 ratio of 76% of the patients had increased by more than 20 mmHg (responder) with a mean increase of 78 +/- 53 mmHg. The proportion of responders increased to 85% after 6 hours of prone positioning. The incidence of maneuver-related complications and severe and life-threatening complications was extremely rare. The overall mortality at ICU discharge was 51% and the ICU stay was similar in survivors and non survivors (17.8 +/- 11.6 vs 17.8 +/- 11.4 days).