A Comparison of Synchronized and Non-synchronized Intermittent Mandatory Ventilation

Abstract

Intermittent mandatory ventilation (IMV), a commonly used form of mechanical ventilation, allows patients to breathe spontaneously between mechanical breaths. A recent suggestion is that mechanically synchronizing mandatory and spontaneous breaths might be better than traditional, time-cycled IMV. We compared numerous cardiorespiratory variables of 35 consecutive patients during IMV and synchronized IMV (SIMV). Cardiac and stroke indices, oxygen consumption, blood pressure, pulmonary artery and pulmonary artery occlusion pressures, systemic and pulmonary arteriolar resistances, arterial pH, PCO2, PO2, and intrapulmonary physiologic shunt fraction did not vary significantly during either IMV or SIMV, regardless of the patient's cardiopulmonary status. Pulmonary barotrauma did not occur in any patient during either ventilatory mode. We were unable to confirm that mechanically synchronizing spontaneous and mechanical ventilation has any physiologic advantage.