Pressure controlled versus volume controlled ventilation with laryngeal mask airway.

STUDY OBJECTIVE To quantify the impact on peak airway pressure of pressure-controlled and volume-controlled ventilation during Laryngeal Mask Airway (LMA) use. DESIGN Prospective, crossover clinical study. SETTING University-affiliated hospital. PATIENTS 32 ASA physical status I and II patients undergoing general anesthesia with the LMA. INTERVENTIONS Patients were ventilated for three minutes both with pressure-controlled and volume-controlled ventilation, provided that tidal volume (V(T) ) and inspiratory time (It) were constant. MEASUREMENTS AND MAIN RESULTS The monitored parameters were electrocardiography, arterial blood pressure, pulse oximetry, capnography, neuromuscular transmission, airway pressure and flow, and concentration of ventilated vapors and gases. The actually delivered V(T) was similar with both types of ventilation (volume-controlled = 0.67 +/- 0.13 lt, pressure-controlled = 0.67 +/- 0.14 lt; p = 0.688). Peak airway pressure was lower during pressure-controlled ventilation (14.6 +/- 3.5 cmH(2)O) than during volume-controlled ventilation (16 +/- 4 cmH(2)O) (p < 0.001). Furthermore, we noted that the higher the airway pressure with volume-controlled ventilation, the greater was the reduction in airway pressure during pressure-controlled ventilation. CONCLUSIONS Pressure-controlled rather than volume-controlled ventilation can improve the effectiveness of mechanical ventilation in patients with high airway pressure.