EFFICACY OF NONINVASIVE CPAP IN COPD WITH ACUTE RESPIRATORY-FAILURE

Dynamic hyperinflation and the development of intrinsic positive end-e xpiratory pressure (PEEPi) are commonly observed in patients with seve re chronic obstructive pulmonary disease (COPD) in acute respiratory f ailure, Previous studies have shown that externally applied PEEP reduc es PEEPi and its adverse effects in mechanically-ventilated COPD patie nts, The purpose of this study was to determine the effects of graded amounts of continuous positive airway pressure (CPAP) on the degree of inspiratory effort, pattern of breathing, gas exchange, and level of dyspnoea in a group of spontaneously breathing, nonintubated COPD pati ents in acute hypercapnic respiratory failure, Ten COPD patients admit ted to the intensive care unit in acute hypercapnic respiratory failur e were studied, Inspiratory effort was measured by the tidal excursion s of oesophageal (Poes) and transdiaphragmatic (Pdi) pressure, Inspira tory effort and both the pressure-time product for the diaphragm (inte gral Pdi-dt) and for the inspiratory muscles (integral Poes-dt) were m easured during the application of 5, 7.5, and 10 cmH(2)O of CPAP, Dysp noea, gas exchange and pattern of breathing were also assessed, Inspir atory effort and the pressure-time product both for the diaphragm and the inspiratory muscles fell significantly with CPAP in a dose-depende nt fashion, Both the pattern of breathing and level of dyspnoea improv ed with CPAP, End-expiratory lung volume remained stable at the lower levels of CPAP, with only modest increases at the higher levels, Arter ial oxygen tension (Pa,O-2) and arterial carbon dioxide tension (Pa,CO 2) either improved or remained stable with CPAP. We conclude that the noninvasive application of CPAP to spontaneously breathing patients wi th severe COPD in acute respiratory failure decreases inspiratory effo rt and dyspnoea whilst improving breathing pattern, It is conceivable that the early institution of CPAP in this setting may obviate the nee d for intubation and conventional mechanical ventilation.