Effects of biphasic positive airway pressure in patients with chronic obstructive pulmonary disease

Biphasic positive airway pressure (BiPAP) is a ventilatory mode in which tw o pressure levels (higher (Phigh) and lower (Plow)) acting as continuous po sitive airway pressure (CPAP) alternate at preset time intervals. BiPAP com bines pressure-controlled ventilation with unrestricted spontaneous breathi ng, BiPAP has not yet been evaluated in patients with chronic obstructive p ulmonary disease (COPD). Therefore, the effects of BiPAP (15 cmH(2)O Phigh and 5 cmH(2)O Plow) press ure support (PS; 15 cmH(2)O and positive end-expiratory pressure (PEEP)5 cm H2O) and CPAP (5 cmH(2)O) on respiratory mechanics in COPD patients were co mpared. Twenty-one COPD patients were supported in randomized order with Bi PAP, PS and CPAP. Pressure-time product (PTP), work of breathing (WOB), cha nge in oesophageal pressure (Delta Poes), mouth occlusion pressure (P0.1), intrinsic PEEP (PEEPi). tension time index (TTI), respiratory frequency, an d tidal volume (VT) were measured. During BiAP, the COPD patients showed a significantly higher PTP, WOB, Delt a Poes, P0.1, TTI and PEEPi than during PS, Comparing the Plow phases of Bi PAP and CPAP, the breaths during the Plow phases of BiPAP had a lower VT an d a greater WOB and PTP due to a higher PEEPi than on CPAP alone. In conclusion, biphasic positive airway pressure carries the risk of increa sed work of breathing in spontaneously breathing chronic obstructive pulmon ary disease patients. Pressure support is superior for reducing their respi ratory muscle effort.