[Physiologic response to proportional assist ventilation in patients with acute exacerbation of chronic obstructive pulmonary disease].

OBJECTIVE: To investigate the effect of different assist levels during proportional assist ventilation (PAV) on patients with acute exacerbation of chronic obstructive pulmonary disease (COPD). METHODS: Nine patients with acute exacerbation of COPD received different levels of assist ventilation during PAV. The change of inspiratory muscle effort and breathing pattern of the patients were observed. RESULTS: (1) The average tidal volume (V(T)), minute ventilation (V.(E)) and respiratory frequency (RR) were slightly higher during PAV, as compared to spontaneous breathing (SB). The change of breathing pattern of the patients was not significant at different assist levels during PAV. (2) The transdiaphragmatic pressure (Pdi), the pressure-time product (PTP) and work of breathing (Wi) reduced significantly during PAV as compared with SB (differently reduced 8.36 cm H2O, 11.49 cm H2O.s(-1).L(-1) and 0.53 J/L). The change in Pdi, PTP and Wi was small among different levels during PAV. (3) Dyspnea was improved during PAV. CONCLUSIONS: The present study confirms the feasibility of noninvasive ventilation PAV in treating patients with acute exacerbation of COPD. Based on the patient's assessment, the ventilatory support level which the patients could comfortably tolerate was (57 +/- 11)%. noninvasive ventilation PAV set at a level of comfort determined by the patient can unload inspiratory muscles; at the comfortable level of ventilatory support, Wi, Pdi and PTP decreased by 57%, 72% and 65% respectively. It also improved breathing pattern and dypnea.