Effects of Inverse Ratio Ventilation versus  Positive End-expiratory Pressure on Gas Exchange and Gastric Intramucosal Pco2and pH under Constant Mean Airway Pressure in Acute Respiratory Distress Syndrome

2001 ◽  
Vol 95 (5) ◽  
pp. 1182-1188 ◽  
Author(s):  
Chung-Chi Huang ◽  
Mei-Ju Shih ◽  
Ying-Huang Tsai ◽  
Yu-Chen Chang ◽  
Thomas C. Y. Tsao ◽  
...  
Keyword(s):  
Acute Respiratory Distress Syndrome ◽  
Gas Exchange ◽  
Respiratory Distress Syndrome ◽  
Respiratory Distress ◽  
Airway Pressure ◽  
Distress Syndrome ◽  
Positive End Expiratory Pressure ◽  
Mean Airway Pressure ◽  
Inverse Ratio Ventilation ◽  
Pressure Controlled

Background In patients with acute respiratory distress syndrome, whether inverse ratio ventilation differs from high positive end-expiratory pressure (PEEP) for gas exchange under a similar mean airway pressure has not been adequately examined. The authors used arterial oxygenation, gastric intramucosal partial pressure of carbon dioxide (PiCO(2)), and pH (pHi) to assess whether pressure-controlled inverse ratio ventilation (PC-IRV) offers more benefits than pressure-controlled ventilation (PCV) with PEEP. Methods Seventeen acute respiratory distress syndrome patients were enrolled and underwent mechanical ventilation with a PCV inspiratory-to-expiratory ratio of 1:2, followed by PC-IRV 1:1 initially. Then, they were randomly assigned to receive PC-IRV 2:1, then 4:1 or 4:1, and then 2:1, alternately. The baseline setting of PCV 1:2 was repeated between the settings of PC-IRV 2:1 and 4:1. Mean airway pressure and tidal volume were kept constant by adjusting the levels of peak inspiratory pressure and applied PEEP. In each ventilatory mode, hemodynamics, pulmonary mechanics, arterial and mixed venous blood gas analysis, PiCO(2), and pHi were measured after a 1-h period of stabilization. Results With a constant mean airway pressure, PC-IRV 2:1 and 4:1 decreased arterial and mixed venous oxygenation as compared with baseline PCV 1:2. Neither the global oxygenation indices with oxygen delivery and uptake nor PiCO(2) and pHi were improved by PC-IRV. During PC-IRV, applied PEEP was lower, and auto-PEEP was higher. Conclusion When substituting inverse ratio ventilation for applied PEEP to keep mean airway pressure constant, PC-IRV does not contribute more to better gas exchange and gastric intramucosal PiCO(2) and pHi than does PCV 1:2 for acute respiratory distress syndrome patients, regardless of the inspiratory-to-expiratory ratios.

Cardiorespiratory Effects of Positive End-expiratory Pressure during Progressive Tidal Volume Reduction (Permissive Hypercapnia) in Patients with Acute Respiratory Distress Syndrome

1995 ◽  
Vol 83 (4) ◽  
pp. 710-720. ◽  
Author(s):  
V. Marco Ranieri ◽  
Luciana Mascia ◽  
Tommaso Fiore ◽  
Francesco Bruno ◽  
Antonio Brienza ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Acute Respiratory Distress Syndrome ◽  
Gas Exchange ◽  
Respiratory Distress Syndrome ◽  
Respiratory Distress ◽  
Tidal Volume ◽  
Distress Syndrome ◽  
Alveolar Recruitment ◽  
Permissive Hypercapnia ◽  
Positive End Expiratory Pressure

Background In patients with acute respiratory distress syndrome (ARDS), the ventilatory approach is based on tidal volume (VT) of 10-15 ml/kg and positive end-expiratory pressure (PEEP). To avoid further pulmonary injury, decreasing VT and allowing PaCO2 to increase (permissive hypercapnia) has been suggested. Effects of 10 cmH2O of PEEP on respiratory mechanics, hemodynamics, and gas exchange were compared during mechanical ventilation with conventional (10-15 ml/kg) and low (5-8 ml/kg) VT. Methods Nine sedated and paralyzed patients were studied. VT was decreased gradually (50 ml every 20-30 min). Static volume-pressure (V-P) curves, hemodynamics, and gas exchange were measured. Results During mechanical ventilation with conventional VT, V-P curves on PEEP 0 (ZEEP) exhibited an upward convexity in six patients reflecting a progressive reduction in compliance with inflating volume, whereas PEEP resulted in a volume displacement along the flat part of this curve. After VT reduction, V-P curves in the same patients showed an upward concavity, reflecting progressive alveolar recruitment with inflating volume, and application of PEEP resulted in alveolar recruitment. The other three patients showed a V-P curve with an upward concavity; VT reduction increased this concavity, and application of PEEP induced greater alveolar recruitment than during conventional VT. With PEEP, cardiac index decreased by, respectively, 31% during conventional VT and 11% during low VT (P < 0.01); PaO2 increased by 32% and 71% (P < 0.01), respectively, whereas right-to-left venous admixture (Qs/Qt) decreased by 11% and 40%, respectively (P < 0.01). The greatest values of PaO2, static compliance, and oxygen delivery and the lowest values of Qs/Qt (best PEEP) were obtained during application of PEEP with low VT (P < 0.01). Conclusions Although PEEP induced alveolar hyperinflation in most patients during mechanical ventilation with conventional VT, at low VT, there appeared to be a significant alveolar collapse, and PEEP was able to expand these units, improving gas exchange and hemodynamics.

Optimal Mean Airway Pressure during High-frequency Oscillation

2001 ◽  
Vol 94 (5) ◽  
pp. 862-869 ◽  
Author(s):  
Sven Goddon ◽  
Yuji Fujino ◽  
Jonathan M. Hromi ◽  
Robert M. Kacmarek
Keyword(s):  
Acute Respiratory Distress Syndrome ◽  
Respiratory Distress Syndrome ◽  
High Frequency ◽  
Airway Pressure ◽  
Distress Syndrome ◽  
High Frequency Oscillation ◽  
Positive End Expiratory Pressure ◽  
Mean Airway Pressure ◽  
Frequency Oscillation ◽  
Initial Injury

Background A number of groups have recommended setting positive end-expiratory pressure during conventional mechanical ventilation in adults at 2 cm H2O above the lower corner pressure (P(CL)) of the inspiratory pressure-volume (P-V) curve of the respiratory system. No equivalent recommendations for the setting of the mean airway pressure (Paw) during high-frequency oscillation (HFO) exist. The authors questioned if the Paw resulting in the best oxygenation without hemodynamic compromise during HFO is related to the static P-V curve in a large animal model of acute respiratory distress syndrome. Methods Saline lung lavage was performed in seven sheep (28+/-5 kg, mean +/- SD) until the arterial oxygen partial pressure/fraction of inspired oxygen ratio decreased to 85+/-27 mmHg at a positive end-expiratory pressure of 5 cm H2O (initial injury). The PCL (20+/-1 cm H2O) on the inflation limb and the point of maximum curvature change (PMC; 26+/-1 cm H2O) on the deflation limb of the static P-V curve were determined. The sheep were subjected to four 1-h cycles of HFO at different levels of Paw (P(CL) + 2, + 6, + 10, + 14 cm H2O), applied in random order. Each cycle was preceded by a recruitment maneuver at a sustained Paw of 50 cm H2O for 60 s. Results High-frequency oscillation with a Paw of 6 cm H2O above P(CL) (P(CL) + 6) resulted in a significant improvement in oxygenation (P < 0.01 vs. initial injury). No further improvement in oxygenation was observed with higher Paw, but cardiac output decreased, pulmonary vascular resistance increased, and oxygen delivery decreased at Paw greater than P(CL) + 6. The PMC on the deflation limb of the P-V curve was equal to the P(CL) + 6 (r = 0.77, P < 0.05). Conclusion In this model of acute respiratory distress syndrome, optimal Paw during HFO is equal to P(CL) + 6, which correlates with the PMC.

Sigh Improves Gas Exchange and Lung Volume in Patients with Acute Respiratory Distress Syndrome Undergoing Pressure Support Ventilation

2002 ◽  
Vol 96 (4) ◽  
pp. 788-794 ◽  
Author(s):  
Nicoló Patroniti ◽  
Giuseppe Foti ◽  
Barbara Cortinovis ◽  
Elena Maggioni ◽  
Luca M. Bigatello ◽  
...  
Keyword(s):  
Acute Respiratory Distress Syndrome ◽  
Gas Exchange ◽  
Respiratory Distress Syndrome ◽  
Respiratory Distress ◽  
Lung Volume ◽  
Pressure Support Ventilation ◽  
Airway Pressure ◽  
Pressure Support ◽  
Distress Syndrome ◽  
Support Ventilation

Background The aim of our study was to assess the effect of periodic hyperinflations (sighs) during pressure support ventilation (PSV) on lung volume, gas exchange, and respiratory pattern in patients with early acute respiratory distress syndrome (ARDS). Methods Thirteen patients undergoing PSV were enrolled. The study comprised 3 steps: baseline 1, sigh, and baseline 2, of 1 h each. During baseline 1 and baseline 2, patients underwent PSV. Sighs were administered once per minute by adding to baseline PSV a 3- to 5-s continuous positive airway pressure (CPAP) period, set at a level 20% higher than the peak airway pressure of the PSV breaths or at least 35 cm H2O. Mean airway pressure was kept constant by reducing the positive end-expiratory pressure (PEEP) during the sigh period as required. At the end of each study period, arterial blood gas tensions, air flow and pressures traces, end-expiratory lung volume (EELV), compliance of respiratory system (Crs), and ventilatory parameters were recorded. Results Pao2 improved (P < 0.001) from baseline 1 (91.4 +/- 27.4 mmHg) to sigh (133 +/- 42.5 mmHg), without changes of Paco2. EELV increased (P < 0.01) from baseline 1 (1,242 +/- 507 ml) to sigh (1,377 +/- 484 ml). Crs improved (P < 0.01) from baseline 1 (40.2 +/- 12.5 ml/cm H2O) to sigh (45.1 +/- 15.3 ml/cm H2O). Tidal volume of pressure-supported breaths and the airway occlusion pressure (P0.1) decreased (P < 0.01) during the sigh period. There were no significant differences between baselines 1 and 2 for all parameters. Conclusions The addition of 1 sigh per minute during PSV in patients with early ARDS improved gas exchange and lung volume and decreased the respiratory drive.

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