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Background Pressure-controlled inverse inspiratory to expiratory ratio ventilation (PC-IRV) is thought to be beneficial for reducing the dead space volume. Objective To investigate the effects of PC-IRV on the components of dead space during robot-assisted laparoscopic radical prostatectomy (RLRP). Design A randomised crossover study of three different ventilator modes. Setting A single university hospital from September 2014 to April 2015. Patients Twenty consecutive study participants undergoing RLRP. Interventions Patients were ventilated sequentially with three different modes in random order for 30 min: volume control ventilation (VCV; inspiratory to expiratory ratio 0.5), pressure control ventilation (PCV; inspiratory to expiratory ratio 0.5) and PC-IRV. Inverse inspiratory to expiratory ratio was adjusted individually by observing the expiratory flow-time wave to prevent the risk of dynamic pulmonary hyperinflation. Main outcome measures The primary outcome included physiological dead space (VDphys), airway dead space (VDaw), alveolar dead space (VDalv) and shunt dead space (VDshunt). VDphys was calculated by Enghoff's method. We also analysed respiratory dead space (VDresp) and VDaw using a novel analytical method. Then, VDalv and VDshunt were calculated by VDalv = VDresp - VDaw and VDshunt = VDphys - VDresp, respectively. Results The VDphys/expired tidal volume (VTE) ratio in PC-IRV (29.2 ± 4.7%) was significantly reduced compared with that in VCV (43 ± 8.5%) and in PCV (35.9 ± 3.9%). The VDshunt/VTE in PC-IRV was significantly smaller than that in VCV and PCV. VDaw/VTE in PC-IRV was also significantly smaller than that in VCV but not that in PCV. There was no significant change in VDalv/VTE. Conclusion PC-IRV with the inspiratory to expiratory ratio individually adjusted by the expiratory flow-time wave decreased VDphys/VTE in patients undergoing RLRP. Trial registration University Hospital Medical Information Network in Japan 000014004.

Objective: Investigation of oxygenation and lung aeration during mechanical ventilation according to the open lung concept in patients with acute lung injury or acute respiratory distress syndrome. Design: Retrospective analysis. Setting: Surgical intensive care unit of a university hospital. Patients: We retrospectively identified 17 patients with acute lung injury/acute respiratory distress syndrome due to pulmonary contusion who had thoracic helical computed tomography scans before and after ventilation with the open lung concept. Interventions: Baseline ventilation consisted of low tidal volumes (≤6 mUkg) and positive end-expiratory pressure (PEEP; 5-17 cm H 2 O). We briefly applied high inspiratory pressures for opening up collapsed alveoli. External PEEP and intrinsic PEEP were combined to keep recruited lung units open. We generated intrinsic PEEP by pressure-cycled high-frequency inverse ratio ventilation (80 min -1 , inspiratory/expiratory ratio 2:1) and maintained our ventilatory strategy for 24 hrs. Then, after reducing total PEEP by decreasing respiratory rate, Pao 2 /Fio 2 ratio was reevaluated. If it remained >300 mm Hg, weaning was started. If not, previous ventilator settings were resumed for another 24 hrs after recruiting the lungs once again. Measurements and Main Results: Physiologic variables and ventilator settings were obtained from routine charts. Data from computed tomography before and after the open lung concept were analyzed for volumetric quantification of lung aeration and collapse. All results are presented as median and range. During baseline ventilation, PEEP was 10 (range, 5-17) cm H 2 O and after recruitment 21 (range, 18-26) cm H 2 O. Opening pressures were 65 (range, 50-80) cm H 2 O. After recruitment, Pao 2 /Fio 2 ratio was higher in all patients. Total lung volume increased from 2915 (range, 1952-4941) to 4247 (range, 2285-6355) mL and normally aerated volume from 1742 (range, 774-2941) to 2971 (range, 1270-5232) mL. Atelectasis decreased significantly from 604 (range, 147-1538) to 106 (range, 0-736) mL. Hyperinflation increased significantly from 5 (range, 0-188) to 62 (range, 1-424) mL, whereas poor aeration did not change substantially from 649 (range, 302-1292) to 757 (range, 350-1613) mL. No hemodynamic problems occurred. Conclusions: Lung recruitment increased arterial oxygenation, normally aerated lung volume, and total lung volume while decreasing the amount of collapsed tissue. These results indicate that the open lung concept is a reasonable mode of ventilation for patients with severe chest trauma.

The acute respiratory distress syndrome occurs commonly in critical care. There is an increasing volume of clinical and experimental evidence that poor ventilatory technique that is injurious to the lungs can propagate the systemic inflammatory response and adversely affect mortality. Many ventilatory techniques have been hypothesized to 'protect' the lungs during mechanical ventilation, including tidal volume limitation, high positive end-expiratory pressure, pressure-controlled inverse ratio ventilation, and prone positioning. Experimental techniques include liquid ventilation, surfactant administration and extracorporeal gas exchange. Despite excellent rationale for their use, few techniques, apart from tidal volume limitation, have been shown to improve survival in randomized controlled trials.

OBJECTIVE To assess the possibility that acute respiratory distress syndrome (ARDS) of pulmonary and nonpulmonary origins represent two distinct syndromes. DESIGN Analysis of data collected prospectively from an inception cohort of 117 patients with ARDS. SETTING Adult intensive care unit (ICU), university/postgraduate hospital. MEASUREMENTS AND MAIN RESULTS Differences were sought in mortality and 6-month functional outcome between patients developing ARDS due to pulmonary (group 1) and nonpulmonary (group 2) pathology. Group 1 patients displayed a trend toward increased ICU and in-hospital mortality (42.1% vs. 23.2%, p = .10, and 47.4% vs. 27.9%, p = .11, respectively). No difference was found in ICU length of stay (46.3 +/- 4.9 vs. 39.0 +/- 4.8 days for groups 1 and 2, respectively) nor in duration of positive-pressure ventilation (26.2 +/- 4.3 vs. 20.6 +/- 3.2 days). However, the need for pressure-controlled inverse ratio ventilation was significantly greater in group 1 (16.9 +/- 3.2 vs. 9.1 +/- 1.3 days; p = .033). In survivors, reductions in total lung capacity at 6 months (68.1 +/- 4.6 vs. 61.8 +/- 4.6% predicted for groups 1 and 2, respectively; p = .4), accessible lung volume (74.4 +/- 4.4 vs. 68.9 +/- 4.9% predicted; p = .56), and forced expiratory volume (77.8 +/- 2.9 vs. 80.3 +/- 2.4% predicted; p = .57) did not differ between groups. Gas transfer coefficient was well preserved (84.5 +/- 4.6 vs. 86.6 +/- 4.7% predicted; p = .80). CONCLUSIONS These data suggest a trend toward higher mortality and ventilatory requirements in ARDS of direct etiology, generating a hypothesis worthy of further exploration.

Objective: Gastric intramucosal PCO 2 (PiCO 2 ) and pH (pHi) are currently used as indices of the adequacy of splanchnic perfusion and as end points to guide therapeutic intervention. However, little is known about their spontaneous variability over time. The present study was designed to define the magnitude of spontaneous variability of Picot and pHi in sedated medical intensive care unit (ICU) patients using an automated recirculating air tonometer and to test whether high-level positive end-expiratory pressure (PEEP) or inverse inspiratory/expiratory (I:E) ratio ventilation resulted in a greater variability than low PEEP with conventional I:E ratio ventilation. Design: Prospective study. Setting: Medical ICU in a tertiary medical center. Patients: Twenty-three acute respiratory failure patients. Interventions: After being sedated, patients were randomized to undergo pressure control ventilation at the following three settings: A, high PEEP (15 cm H 2 O) with conventional I:E ratio (1:2), and B, low PEEP (5 cm H 2 O) with inverse I:E ratio (2:1) alternately, and then C, low PEEP (5 cm H 2 O) with conventional I:E ratio (1:2). Each ventilation setting period lasted 1 hr. Measurements and Main Results: The Picot and pHi were measured at baseline (time 0), and at 15, 30, 45, and 60 mins thereafter. The corresponding coefficients of variation (CVs) of PiCO 2 for overall pooled group and settings A, B, and C were 4.0%, 4.4%, 3.4%, and 4.2%, respectively. The corresponding CVs of pHi for overall pooled group and settings A, B, and C were 0.36%, 0.37%, 0.33%, and 0.4%, respectively. Analysis of variance showed no significant difference in the CVs of Pi CO2 or pHi between the three settings. The 95% confidence interval is approximately ±8% variability for PiCO 2 and ±0.7% variability for pHi. Conclusions: In critically ill medical ICU patients with stable hemodynamics, the spontaneous variability of PiCO 2 or pHi are not substantial. High PEEP (15 cm H 2 O) and inverse ratio ventilation (2:1), which does not change the cardiac output or hemodynamics, does not contribute to increased spontaneous variability in Pi CO2 or pHi.

One of the many challenges in the management of the patient with adult respiratory distress syndrome is optimal application of mechanical ventilation. Pressure controlled-inverse ratio ventilation has surfaced as a possible alternative to conventional ventilation for patients affected by this condition. In pressure controlled-inverse ratio ventilation, the conventional inspiratory-to-expiratory ratio is reversed, allowing the inspiratory phase to lengthen with an accompanying increase in mean airway pressure. When carefully applied, mean airway pressure adjustments can be manipulated without increases in positive end-expiratory pressure and peak airway pressure, thus minimizing the risk of alveolar rupture and worsening of lung injury.

OBJECTIVES To investigate physiologic and outcome data in patients switched from volume-cycled conventional ratio ventilation to pressure-controlled inverse ratio ventilation that did not produce air trapping and intrinsic positive end-expiratory pressure (PEEP). SETTING Medical intensive care unit. DESIGN Retrospective analysis of crossover data and outcome. PATIENTS Fourteen patients with the adult respiratory distress syndrome who were receiving mechanical ventilation with volume-cycled, conventional ratio ventilation followed by pressure-controlled, inverse ratio ventilation. INTERVENTIONS Our approach to pressure-controlled, inverse ratio ventilation was to use tidal volumes and applied PEEP values comparable to those volumes and values used on volume-cycled, conventional ratio ventilation, use inspiratory times to increase mean airway pressure instead of additional applied PEEP, and avoid air trapping (intrinsic PEEP). MEASUREMENTS AND MAIN RESULTS With this approach, there was a reduction in peak airway pressure from 53 +/- 8.5 (SD) to 40 +/- 5.9 cm H2O (p < .01), and an increase in mean airway pressure from 20 +/- 3.9 to 30 +/- 5.2 cm H2O (p < .01). Tidal volume, mean inflation pressure, and compliance did not change. Oxygenation (PaO2) improved from 57 +/- 11.3 torr (7.6 +/- 1.5 kPa) to 94 +/- 40.2 torr (12.5 +/- 5.4 kPa) (p = .01) but the oxygenation index (mean airway pressure x FIO2 x 100/PaO2) did not change significantly (25.9 +/- 10.3 to 27.2 +/- 12.2). There was no significant change in PaCO2 or pH even though delivered minute ventilation decreased from 17.4 +/- 4.3 to 14.8 +/- 5.8 L/min (p = .02). Cardiac index slightly decreased, but hemodynamic values were otherwise stable. Only three of the 14 study patients survived. CONCLUSIONS These data demonstrate that oxygenation is primarily a function of mean airway pressure, and that longer inspiratory times can be used as an alternative to applied PEEP to increase this oxygenation. If no air trapping develops, lung inflation pressures and delivered volumes remain constant with this approach. Because the technique was used only in patients refractory to conventional techniques, the poor outcome is not surprising.

Background Pressure-controlled (PCV) and pressure-controlled inverse ratio ventilation (PCIRV) have been proposed instead of volume-controlled conventional ratio ventilation (VC) with positive end-expiratory pressure (PEEP) for patients with adult respiratory distress syndrome (ARDS). The advantages advocated with the use of PCIRV are to decrease airway pressures and to improve gas exchange. However, most studies did not compare PCIRV and VC while keeping both the level of ventilation and end-expiratory alveolar pressure (total-PEEP) constant. Methods Nine patients with moderate to severe ARDS (lung injury score 2.83 +/- 0.18) had their lungs ventilated with VC, PCV with a conventional ratio (I:E 1:2; PC 1/2), and PCIRV (I:E 2:1 and 3:1; PC 2/1 and PC 3/1, respectively). Ventilator settings were adjusted to keep tidal volume, respiratory rate, FIo2, and total-PEEP constant in every mode. With each mode, a complete set of ventilatory, hemodynamic, and gas exchange parameters was obtained after 30 min. Results In PC 3/1, the data obtained could not be strictly compared to the other modes because total-PEEP was higher despite external-PEEP being set at zero. For the other modes (VC, PC 1/2, and PC 2/1), despite differences in peak airway pressures, no difference was noted for end-inspiratory and end-expiratory static airway pressures (which better reflect alveolar pressures) nor for lung and respiratory system compliance. Arterial oxygenation deteriorated slightly with PC 2/1 despite a higher mean airway pressure, whereas alveolar ventilation tended to be slightly, but not significantly, improved (lower PaCo2). A decrease in systolic and mean arterial pressure also was observed with PC 2/1 without other significant hemodynamic change. Conclusions In this prospective controlled study, no short-term beneficial effect of PCV or PCIRV could be demonstrated over conventional VC with PEEP in patients with ARDS.

This article reviews adult respiratory distress syndrome as it is associated with multiple organ dysfunction and systemic inflammatory response. The pathophysiology of adult respiratory distress syndrome is discussed and related to the clinical presentation. Included in the clinical presentation is a discussion of respiratory and hemodynamic alterations, lung mechanics, and oxygen delivery and consumption alterations. Conventional therapeutic modalities for treatment of adult respiratory distress syndrome are reviewed in addition to new ventilatory approaches. New approaches to ventilation and oxygenation included in this article are pressure control ventilation, inverse ratio ventilation, permissive hypercapnia, and extracorporeal therapy. New pharmacologic therapy for the treatment of adult respiratory distress syndrome is also reviewed in this article.

OBJECTIVE The aim of this study was to estimate the agreement between superior vena caval pressure (SVCP) and femoroiliac venous pressure (FIVP) measurements by using short (

OBJECTIVE To present the first documented case report of myopathy persisting for >48 hrs in a patient treated with cisatracurium and concomitant high-dose corticosteroids. DESIGN Anecdotal observations in one patient. SETTING Medical-respiratory intensive care unit (ICU) at a tertiary care, university teaching hospital. PATIENT A 45-yr-old female admitted status for post-bilateral total knee replacement complicated by aspiration pneumonitis and acute respiratory distress syndrome (ARDS). INTERVENTIONS The patient required pressure control ventilation and sedation with midazolam and fentanyl infusions. On ICU day 2, the patient was placed on inverse ratio ventilation and paralyzed with cisatracurium. On ICU day 6, methylprednisolone 125 mg i.v. every 6 hrs was initiated for fibroproliferative ARDS. On ICU day 11, methylprednisolone was reduced to 60 mg i.v. every 6 hrs and tapered over several weeks. Cisatracurium infusion rates ranged from 6.3 to 10.5 microg/kg/min, with an average of 8.0 microg/kg/min. MEASUREMENTS AND MAIN RESULTS Train-of-Four was assessed before initiation of therapy and every 4 hrs, thereafter. Train-of-Four values were maintained from 1 to 4 throughout therapy and a value of 4 was recorded when therapy was discontinued. On day 13, neuromuscular blocking agent therapy was discontinued, but severe proximal and distal muscle weakness was observed bilaterally. Creatinine kinase concentrations on 3 and 13 days after discontinuation of the paralytic agent were 181 and 96 units/L, respectively. On day 24, the patient moved her fingertips. On ICU day 30, the patient was weaned from the mechanical ventilator. The patient was transferred to the ward on day 33. Extensive rehabilitation with physical and occupational therapy was required for several months. CONCLUSION Clinicians should remember that irrespective of chemical structural, neuromuscular blocking agents might produce prolonged paralysis in predisposed patients.

Mechanical ventilation with different ratios of inspiratory to expiratory times (I:E ratio) and levels of positive end-expiratory pressure (PEEP) were applied to 9 dogs after the aspiration of fresh water and then were compared. The dogs were ventilated with an I:E ratio of 2:1 with 0 PEEP; an I:E r

We successfully employed inverse ratio ventilation on a 6-year-old multiple trauma victim with severe adult respiratory distress syndrome after conventional ventilation modes using volume ventilation with high positive peak inspiratory pressure and PEEP had failed to improve oxygenation.