Intermittent mandatory ventilation (IMV): a primary ventilatory support mode.

Respiratory therapy should be directed at underlying pathophysiology, not symptomatology. Mechanical ventilation, oxygen, and CPAP should be administered to patients independently and in appropriate amounts. Removal of each of these therapeutic interventions should occur in a similar fashion. The method for determining optimal mechanical ventilation, oxygen concentration, and CPAP level is not unlike that recommended for many other therapeutic interventions. Each should be applied to achieve a predetermined goal, each should be continually reevaluated, and each should be withdrawn when indicated. Optimal CPAP should be applied to improve matching of ventilation and perfusion and to improve pulmonary mechanics so that the requirement for oxygen and mechanical ventilation is reduced. A reduction in inspired oxygen concentration may prevent absorption atelectasis and allow more rapid discontinuation of mechanical ventilation and CPAP. Minimal mechanical ventilatory support eliminates iatrogenic respiratory alkalosis and improves distribution of ventilation. This approach minimizes the detrimental effects of mechanical ventilatory support on acid-base balance and cardiovascular function and decreases the possibility of pulmonary barotrauma. Twelve years of prospective evaluation have demonstrated numerous advantages of IMV. This approach has simplified the management of patients with compromised respiratory function and has decreased morbidity and mortality (10).