Respiratory mechanical and cardio-vascular changes during non invasive ventilation in stable COPD patients with chronic hypercapnic respiratory failure: High intensity ventilation vs low intensity ventilation

In a subgroup of stable COPD patients with chronic hypercapnic respiratory failure (HRF) the use of conventional NPPV (Li-NPPV), can improve pulmonary function, gas exchange, and health related quality of life. High-intensity positive pressure ventilation (Hi-NPPV) with higher IPAP (28 cmH20) and respiratory rate (20/min) were recently adopted in order to achieve maximal PaCO2 reduction and has been shown to better improve diurnal blood gas during spontaneous breathing (SB), compared to Li-NPPV. NPPV can provoke alterations in intrapleural pressure and lung volume, which influence the cardio-vascular performance. Our study evaluates the respiratory mechanical (RM) and cardio-vascular (CV) effects of Li-NPPV and HI-NPPV, in 15 stable COPD patients with HRF. We measured the RM and blood gas parameters, in addition non-invasive measurement of CV parameters was performed. The data were reported as mean ±SD, and where compared with repeated measures ANOVA. Significant (sgn) increases were observed in pleural pressure, decrease in tans-diaphragmatic pressure and minute diaphragmatic pressure-time product (SB: 323±149; Li-NPPV: 132±139; Hi-NPPV: 40±69 cmH2O·s/min). The PaCO2 showed a sgn. decrease and the pH a sign. increase during either modalities of NPPV. Significant reduction were detected in arterial blood pressure, stroke volume, cardiac output (SB: 5.5±1.14; NPPV: 4,7±0.98; Hi-NPPV: 4.00±0.96 l/min) and oxygen transport. The long-term effects of this RM and CV changes are uncertain, accordingly further long-term studies are needed to determine its effect on survival.