Chest
Volume 94, Issue 4, October 1988, Pages 779-781
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Airway Pressure Release Ventilation (APRV): A Human Trial

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After operative coronary revascularization, 14 consenting adults received conventional positive pressure ventilation (PPV). When they were hemodynamically stable, data were collected during PPV and then during airway pressure release ventilation (APRV). During APRV, airway pressure (Paw) was reduced periodically at the lowest frequency which produced normal PaCO2. As anesthesia resolved, the rate of APRV breaths was decreased until patients breathed only with CPAP. During PPV and APRV, pHa, PaO/FIO2, and hemodynamic variables were similar. All patients were weaned from APRV without complication. Optimal ventilator design for patients with acute lung injury would provide CPAP as a primary intervention and secondarily would augment alveolar ventilation. The APRV supported oxygenation and ventilation in patients with mild acute lung injury, yet with much lower peak airway pressure than produced by PPV. (Chest 1988; 94:779-81)

Section snippets

METHODS

After institutional approval, 14 consenting patients received radial arterial cannulae and balloon-tipped, flow-directed pulmonary artery catheters before cardiac revascularization operations. General anesthesia was induced with an intravenous infusion of fentanyl, 50 to 100 μg/kg or sufentanil, 10 μg/kg. Pancuronium bromide, 0.1 mg/kg, provided muscle relaxation. Postoperatively, ventilation was controlled with a tidal volume of 12 ml/kg delivered at a rate sufficient to maintain pHa between

RESULTS

While patients were paralyzed and apneic, PPV and APRV supported ventilation and arterial oxygenation equally successfully in all cases. Mean arterial PO2, PCO2, pH, and PaO2/FIO2 did not differ when apneic patints were ventilated with PPV or APRV (Table 1).

Mechanical ventilatory rate and minute ventilation were similar during APRV and PPV while patients were apneic. However, mean peak Paw was greater during PPV (38 ± 6 cm H2O) (mean ± SD) than during APRV (11 ± 2 cm H2O) (p<0.0001). Measured

DISCUSSION

Cardiopulmonary bypass results in mild acute lung injury by increasing lung water,3, 4 reducing lung volume, and creating mismatching of ventilation and perfusion.5, 6 After cardiopulmonary bypass, CPAP effects an increase in lung volume, lung compliance, and PaO2.6 Patients who receive narcotic-oxygen anesthesia require full ventilatory support in the immediate postoperative period, and partial ventilatory support thereafter, while narcosis and muscle relaxation resolve. Thus, patients who

ACKNOWLEDGMENTS

The authors wish to thank Michael Hodges for assistance with statistical analyses and Nancy Hatch for secretarial assistance.

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Manuscript received December 28; revision accepted March 8.

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