The application and effects of noninvasive AVAPS ventilation on respiratory mechanics in patients with COPD associated respiratory failure

Objective To compare the effects of two noninvasive positive pressure ventilation (NIPPV) patterns, average volume assured pressure support (AVAPS)and conventional pressure support ventilation (PSV), on respiratorymechanics in patients with chronic obstructive pulmonary disease(COPD) associated chronic respiratory failure. Methods Thirty- six COPD patients with chronic respiratory failure [mean age (65 ±4) years old] were ventilated by a face mask. The respiratory mechanics were estimated byusingrun awayapproach duringproportional assisted ventilation (PAV). Ventilatory parameters were measured at 30 min after different pattern ventilation. Results In these 36 patients, the average resistance (Rrs) was (1.100 ±0.147) kPa/ (L.s)[(11.2 ±1.5) cmH2O/(L.s)], elastance (Ers) was (2.338 ±0.216) kPa/L[(23.8 ±2.2) cmH2O/L]. Compared with PSV, the peak inspiratory pressure (PIP) and tidal volume (VT) were slight increasd/ while respiratory rate (RR) and minute volume (MV) was lower than that in AVAPSventilation (all P 0.05). In AVAPS pattern, rapid shallowbreathing index (RSBI) was markedly decreased 33 ±4 than that in PSV 42 ±5(P 0.05), but the precentage of acceptable VT (450 ～550 ml) was obviously increased 68 % ±10 % than that in PSV 44 % ±9 %(P 0.05). Conclusion The AVAPS is a new mechanical ventilatory technique using dual control theory. It adjusts automatically the pressure support level to provide a more constant tidal volume to the patient and the patient's work for breathing(WOB)might be reduced.