Effects of partial ventilatory support modalities on respiratory function in severe hypoxemic lung injury.
OBJECTIVE
The early phase of acute respiratory distress syndrome (ARDS) is characterized by impaired respiratory mechanics, ventilation-perfusion mismatch, and severe hypoxemia. Partial ventilatory support can effectively unload the respiratory workload and improve pulmonary gas exchange with less hemodynamic compromise. The partial ventilatory support mode most indicated in early phases of ARDS has not been determined. This study compares the effects of assisted ventilatory techniques on breathing pattern, gas exchange, hemodynamic function, and respiratory effort with those of controlled mechanical ventilation in similarly sedated subjects.


METHODS
Prospectively randomized crossover animal study.


METHODS
Animal research laboratory.


METHODS
Eleven anesthetized and mechanically ventilated pigs.


METHODS
Acute lung injury was induced by lung lavage. Pressure-controlled ventilation (PCV), pressure-controlled assisted ventilation (P-ACV), bilevel positive airway pressure (BIPAP), and pressure support ventilation (PSV) with equal airway pressures and sedation were applied in random order.


RESULTS
Gas exchange, respiratory effort, and hemodynamic function were measured, and ventilation-perfusion distributions were calculated by multiple inert-gas-elimination techniques. The results revealed that partial ventilatory support was superior to PCV in maintaining adequate oxygenation and hemodynamic function with reduced sedation. The effects of P-ACV, BIPAP, and PSV were comparable with respect to gas exchange and hemodynamic function, except for a more pronounced reduction in shunt during BIPAP. P-ACV and PSV were superior to BIPAP to reduce respiratory drive and work of breathing. PSV affected the pattern of breathing and deadspace to a greater degree than did P-ACV.


CONCLUSIONS
In acute lung injury, P-ACV preserves oxygenation and hemodynamic function with less respiratory effort compared with BIPAP and reduces the need for sedation compared with PCV.
Henzler
Dietrich
D
Department of Anesthesiology, Aachen University Hospital, Germany. mail@d-henzler.de
Pelosi
Paolo
P
Bensberg
Ralf
R
Dembinski
Rolf
R
Quintel
Michael
M
Pielen
Veronica
V
Rossaint
Rolf
R
Kuhlen
Ralf
R
D000818:Animals; D004195:Disease Models, Animal; D000860:Hypoxia / Q000150:complications*; D011175:Positive-Pressure Respiration / Q000379:methods*; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D011669:Pulmonary Wedge Pressure / Q000502:physiology; D011897:Random Allocation; D012128:Respiratory Distress Syndrome / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy*; D015656:Respiratory Mechanics / Q000502:physiology*; D013552:Swine; D016896:Treatment Outcome