RESUMO
Objective:To observe the physiological effect of bi-level positive airway pressure (BiPAP) ventilation among stable chronic obstructive pulmonary disease (COPD) patients.Methods:This was a small sample size, exploratory, interventional study. A total of 10 outpatients with stable COPD were included from Department of Pulmonary and Critical Care Medicine of Zhujiang Hospital, Southern Medical University between January 2018 and December 2018. The BiPAP mode of noninvasive mechanical ventilation was adopted. The inspiratory positive airway pressure was gradually increased from 10 cmH 2O (1 cmH 2O=0.098 kPa) to 24 cmH 2O, and each time by 2 cmH 2O. The expiratory positive airway pressure remained unchanged at 4 cmH 2O. Baseline and test data were collected before and during the ventilation for comparison, including total respiratory cycle time (T tot), inspiratory time (T i), inspiratory time (T e), inspiratory tidal volume (V Ti); mouth pressure (P mo), esophageal pressure (P eso), transdiaphragmatic pressure (P di), esophageal pressure time product (PTP es), diaphragm pressure time product (PTP di), root mean square of electromyography of diaphragm (RMS), V e/RMS, inspiratory capacity (IC), the change in end-expiratory lung volume (ΔEELV) and dynamic PEEPi (PEEPi dyn). Results:All the 10 patients completed the trial. Compared to calm breathing, V Ti, V e, P mo, IC, ΔEELV score and V e/RMS increased significantly with increasing pressure levels (all P<0.05); T e only increased significantly at 20-22 cmH 2O pressure levels compared to calm breathing ( P<0.05). P di, PTP es, PTP di, RMS and RMS/RMS max decreased significantly with increasing levels (all P<0.05). PTP es and PTP di converged to 0 and no longer showed significant changes after the 18 cmH 2O pressure level. RMS and RMS/RMS max flattened out at pressure level greater than 16 cmH 2O. T i/T tot only significantly decreased at the 20 cmH 2O pressure level compared to calm breathing. PEEPi dyn showed a tendency to decrease and then increase with increasing pressure levels. Conclusion:BiPAP ventilation, at appropriate pressure levels, significantly relieves pulmonary ventilation disorders and reduces the load of respiratory muscle in patients with stable COPD.