Cardiopulmonary abnormalities in severe acute respiratory failure

Serial cardiopulmonary variables were recorded over 4 days in 23 children with severe acute respiratory failure. In all patients, pulmonary artery catheters were inserted within 24 hours of the diagnosis of respiratory failure, and all required greater than 10 cm H2O positive end-expiratory pressure to achieve adequate oxygenation. Eight patients died (35% mortality). Evaluation of systemic hemodynamic variables indicated that survivors had higher blood pressures than nonsurvivors, although neither group was in the hypotensive range. Systemic vascular resistance was lower in the nonsurvivors. Cardiac function as evaluated by cardiac index, right ventricular stroke work index, and left ventricular stroke work index was similar in both groups. Survivors demonstrated elevations in mean pulmonary artery pressure and pulmonary vascular resistance during the first 36 hours, with gradual improvement thereafter. In contrast, pulmonary artery pressure and resistance increased progressively in patients who died. Intrapulmonary shunt fractions remained high in the nonsurvivors despite the use of up to 25 cm H2O PEEP. Cardiac function and oxygen delivery were well maintained in both groups despite the high levels of PEEP.