Physiological effects of alveolar, tracheal, and “standard” pressure supports

Abstract

Pressure support (PS) is characterized by a pressure plateau, which is usually generated at the ventilator level (PSvent). We have built a PS device in which the pressure plateau can be obtained at the upper airway level (PSaw) or at the alveolar level (PSA). The effect of these different PS modes was evaluated in seven healthy men during air breathing and 5% CO2breathing. Minute ventilation during air breathing was higher with PSA than with PSaw and lower with PSvent (16 ± 3, 14 ± 3, and 11 ± 2 l/min, respectively). By contrast, there were no significant differences in minute ventilation during 5% CO2 breathing (25 ± 5, 27 ± 7, and 23 ± 5 l/min, respectively). The esophageal pressure-time product per minute was lower with PSA than with PSaw and PSvent during air breathing (29 ± 26, 44 ± 44, and 48 ± 30 cmH2O ⋅ s, respectively) and 5% CO2breathing (97 ± 40, 145 ± 62, and 220 ± 41 cmH2O ⋅ s, respectively). In conclusion, during PS, moving the inspiratory pressure plateau from the ventilator to the alveolar level reduces pressure output, particularly at high ventilation levels.