Comparison of five bilevel pressure ventilators in patients with chronic ventilatory failure - A physiologic study

Objective: To compare patient-ventilator interaction and comfort in patients with chronic ventilatory failure (CVF) who are undergoing noninvasive positive-pressure ventilation with five different commercial bilevel pressure home ventilators. Also, we wanted to evaluate the short-term effects of the five ventilators on physiologic variables, namely, breathing patterns and inspiratory muscles. Design: Randomized, controlled physiologic study. Setting: Pulmonary division of a rehabilitation institution. Patients: Twenty-eight patients with CVF due to COPD (17 patients) and restrictive chest wall diseases (11 patients). Measurements: Sensation of comfort, breathing patterns and minute ventilation ((V) over dot E), respiratory muscles and mechanics, and patient-ventilator interaction during both unassisted and assisted ventilation with the five ventilators applied randomly. Results: The five ventilators showed different flow and pressure waveforms. The level of comfort was somehow different among the studied ventilators. When compared to unassisted ventilation, all ventilators induced a significant increase in (V) over dot E (p < 0.01) without any significant difference among ventilators. Use of the five ventilators resulted in significant differences in peak airway opening pressure (Pao,peak) but not in mean airway opening pressure computed over a period of 1 ruin (PTPao,min), and in a duty cycle. Ineffective efforts (IEs) were similar among the studied ventilators. In comparison with unassisted ventilation, all ventilators induced significant reductions in inspiratory muscle effort (p < 0.001). No significant relationship was found between level of comfort and PTPao,min, Pao,peak, or the number of IEs. Conclusions: In stable, awake patients with CVF, all of the studied ventilators were well-tolerated, although with a great intersubject variability in comfort, and performed well in terms of improvement in (V) over dot E and inspiratory muscle unloading, thus fulfilling the aims of mechanical ventilation. This effect was obtained with similar levels of PTPao,min, despite the fact that Pao,peak was different among some ventilators. The number of IEs was similar among the studied ventilators.