Hemodynamic Effects of External Continuous Negative Pressure Ventilation Compared with Those of Continuous Positive Pressure Ventilation in Dogs with Acute Lung Injury

Patients with noncardiogenic pulmonary edema requiring ventilatory assistance are usually supported with CPPV using positive end-expiratory pressure (PEEP), but CPPV requires endotracheal intubation and may decrease cardiac output (T). The purpose of this study was to examine thoracoabdominal continuous negative pressure ventilation (CNPV) using external negative end-expiratory pressure (NEEP). The effects on gas exchange and hemodynamics were compared with those of CPPV with PEEP, with the premise that CNPV might sustain venous return and Improve T.In 6 supine, anesthetized and paralyzed dogs with oleic-acid-induced pulmonary edema, 30 min of CNPV was alternated twice with 30 min of CPPV. Positive and negative pressure ventilation were carefully matched for fractional inspired oxygen concentration (FlO2 = 0.56), breathing frequency, and tidal volume. In addition, we matched the increase in AFRC obtained with the constant distending pressures produced by both modes of ventilation. An average of −9 cm H2O ...