Effects of nasal pressure support on ventilation and inspiratory work in normocapnic and hypercapnic patients with stable COPD.

OBJECTIVES To assess and compare the effect of nasal continuous positive airway pressure (nCPAP), inspiratory pressure support (PSV), and bilevel positive airway pressure (biPAP) on ventilatory parameters and inspiratory work (WOB) in normocapnic and hypercapnic patients with stable COPD. METHODS While administering nasal pressure support to 10 normocapnic and 10 hypercapnic patients with COPD, we measured airflow and volume with a pneumotachograph as well as esophageal and gastric pressures under nCPAP, PSV, and biPAP conditions. RESULTS nCPAP had no influence on ventilatory parameters but decreased WOB and transdiaphragmatic work (Wdi) at 10 cm H(2)O of pressure in both groups. With PSV and biPAP, ventilatory parameters increased proportionally to the inspiratory applied pressure. WOB and Wdi decreased significantly in both groups while increasing the pressure support. A similar decrease was observed during biPAP proportionally to the level of pressure support. The diaphragmatic pressure-time product decreased similarly in both groups during PSV and biPAP. CONCLUSION The ventilatory response under nCPAP, PSV, and biPAP conditions is similar in hypercapnic and normocapnic patients with stable COPD; PSV and biPAP increase ventilatory parameters and improve Wdi. On the contrary, nCPAP improves WOB but does not increase ventilatory parameters.