COMPARISON OF OXYGEN COST OF BREATHING WITH PRESSURE-SUPPORT VENTILATION AND BIPHASIC INTERMITTENT POSITIVE AIRWAY PRESSURE VENTILATION

Objective: To assess the oxygen cost of breathing with either pressure -support ventilation (PSV) or biphasic intermittent positive airway pr essure ventilation (BIPAP), Design: Prospective, randomized, crossover study. Setting: Medical intensive care unit of a university hospital, Patients: Twenty clinically stable and spontaneously breathing patien ts after long-term mechanical ventilation. Interventions: Patients wer e randomized to start on either PSV or BIPAP, and measurements were pe rformed after an adaptation period of 30 mins, Immediately after, the ventilatory mode was changed and after another 30-min adaptation perio d, the same measurements were performed. Measurements and Main Results : Indirect calorimetry was performed during each ventilatory mode for a period of 30 mins, Oxygen consumption, energy expenditure, CO, produ ction, and respiratory quotient did not differ significantly between t he two ventilatory modes, regardless of the patients' randomization. T here were no statistically significant differences with regard to resp iratory rate, minute volume, and blood gas analysis. All patients tole rated both ventilatory modes without any signs of discomfort. Conclusi ons: Pressure support ventilation and BIPAP are both used for weaning patients gradually from the ventilator, BIPAP may be advantageous in p atients not breathing sufficiently with PSV, since no patient effort i s necessary with use of this ventilatory mode. (Crit Care Med 1998; 26 :1518-1522).