Conventional and high frequency controlled mechanical ventilation in patients with left ventricular dysfunction and pulmonary edema.

The cardiopulmonary effects of conventional controlled mechanical ventilation (CMV), high frequency controlled mechanical ventilation (HFV), and intermittent mandatory ventilation (IMV) were compared in nine patients with ischemic left ventricular dysfunction and pulmonary edema. Ventilatory support during IMV and CMV was adjusted by changing the ventilator rate while tidal volume was maintained at 12 ml/kg. HFV was produced at a frequency of 100 cycles/min and an I/E ratio of 1:2. End-expiratory airway pressure and inspired oxygen concentration were maintained constant. The three ventilatory modes produced similar mean airway, transpulmonary, and intra-thoracic pressures. Mechanical control of respiration required hyperventilation during both CMV and HFV. Arterial blood oxygenation, heart rate, vascular pressures, cardiac output, and myocardial ischemia were unaffected by the changes in ventilation. Decreased arteriovenous oxygen content difference (p less than 0.05) and increased mixed venous oxygen content (p less than 0.05) suggested improved systemic blood flow during IMV. Controlled ventilation by conventional means or with a high frequency technique had no detectable advantage over partial ventilatory support with IMV during cardiopulmonary failure stabilized with vasoactive therapy and continuous positive airway pressure.