Respiratory Physiology-oriented High-intensity Non-invasive Ventilation

Introduction: High-intensity non-invasive ventilation (HI-NIV) is a strategy aimed at maximumly improving PaCO₂. Most studies increased inspiratory positive airway pressure (IPAP) depending on patient9s maximum tolerance. However, excessive IPAP may result in lung hyperinflation, increased oxygen consumption, and ineffective work of breathing. Objectives: To establish respiratory physiology-oriented HI-NIV and investigate its physiological effect. Methods: Diaphragm electromyogram (EMGdi) and other respiratory physiological parameters were recorded through the esophageal electrode catheter during pressure titration process. (Fig1) IPAP was maximally increased when patient was at complete relaxation (EMGdi and negative esophageal pressure vibration were disappeared). The primary outcome was pressure–time product of diaphragm (PTPdi). Results: 12 stable hypercapnic COPD patients were recruited. The mean IPAPs in HI- and LI-NIV were 23.92±1.34 and 15±0cmH₂O respectively. Comparing with LI-NIV, PTPdi, EMGdi%max (The ratio of resting EMGdi to maximum inspiratory EMGdi), ΔPeso and tidal volume (Vt) in HI-NIV were well improved (PTPdi: -2.23±2.64 vs 4.23±2.00cmH2O·s; EMGdi%max: 5.15±1.44 vs 16.51±7.93%; ΔPeso: 8.23±3.61 vs -2.44±5.07cmH₂O; Vt: 783±114 vs 539±56ml; p all<0.001). No difference was found in respiratory rate. Conclusions: Respiratory physiology-oriented HI-NIV is an optimal individualized strategy in treatment of stable hypercapnic COPD.