Effects of respiratory mechanics in weaning patients with chronic obstructive pulmonary disease during proportional assist ventilation

Abstract

Objective To evaluate the effects of proportional assist ventilation (PAV) and pressure support ventilation (PSV) on ventilate parameters of patients with chronic obstructive pulmonary disease (COPD) combined with respiratory failure.Methods Fifteen intubated stable patients recovering from acute exacerbation of COPD combined with respiratory failure were randomized to receive PAV or PSV support 60 min and then crossed over to alternative mode.Respiratory mechanics including respiratory systemelastic resistance and airway resistance were monitored by least square fitting (LSF) methed.During PAV support.the ratio of volume assist (VA) and flow assist (FA) level wag 80%.The ventilate parameters and arterialblood gas at different ventilate condition was observed.Results Compared with low level PSV (PS 10 cm H2O,1 cm H2O=0.098 kPa,PS10),tidal volume in high level PSV (PS 15 cm H2O,PS15) and PAV was significantly increased [(443±12)ml vs(532±34)ml,(464±23)ml,P<0.05].There was no difference in respiratory rate and peak inspiratory pressure between PAV and PS10.Airway occlusion pressure and time product of triggering was d()reased from (5.70±0.25)cm H2O to (4.53±0.25)cm H2O and (0.42±0.04) cm H2O to (0.32±0.03)cm H2O(P<0.05),PaO2/FiO2 ratio and PaCO2 was also significantly improved after PAV supported compared with PS10,and similar with PS15.The rapid shallow breath index at PAV was similar with PS10.Condusion As a positive feedback system,PAV seems more efficacious than low level of PSV in decreasing the work of breathing during the inspiratory phase,resulting in fewer patient-ventilator asynchronism,and it may be beneficial for weaning. Key words: Pulmonary disease,chronic obstructive; Pressure proportional ventilation; Pressure support ventilation; Weaning