Ventilatory pattern in respiratory failure arising from acute myocardial infarction. I. Respiratory and hemodynamic effects of IMV4 vs IPPV12 and PEEP0 vs PEEP10
Positive end-expiratory pressure of 10 cm H2O (PEEP10) was compared with zero end-expiratory pressure (PEEP0), and intermittent mandatory ventilation (IMV), 4/min, with intermittent positive pressure ventilation (IPPV), 12/min, in 9 patients with pulmonary edema due to acute myocardial infarction (AMI). Systemic and pulmonary arterial pressures, pulmonary capillary wedge pressure (PCWP) and CVP, cardiac output (CO) and blood gases were measured during these four experimental interventions, and related parameters calculated. Paco2 was 39.3 ± 0.9 torr during IMV4 and 36.2 ± 1.3 torr during IPPV12, and PCWP remained between 20–30 mm Hg throughout the study. The ventilatory pattern was changed at random order with the patient serving as his own control. Both Pao2 and Pao2/Fio2 and Vo2 increased while venous admixture (Qsp/Qt) decreased with PEEP10. Cardiac and stroke indices (CI, SI) and oxygen delivery were lower with IPPV12 than they were with IMV4. Both left and right ventricular stroke work (LVSW, RVSW) were higher on IMV4. A moderate PEEP level (up to 10 cm H2O) seems beneficial in post-AMI pulmonary edema and has no significant hemodynamic side effects. The results indicate that of the four alternatives studied, IMV4 with PEEP10 is a ventilatory pattern of choice in the respiratory management of these patients, but each individual patient may require precise titration of each modality to achieve the optimal result.