Goldberg P, Reissmann H, Maltais F, Ranieri M, Gottfried S B
Montreal Chest Hospital Centre, Québec, Canada.
Eur Respir J. 1995 Nov;8(11):1894-900. doi: 10.1183/09031936.95.08111894.
Dynamic hyperinflation and the development of intrinsic positive end-expiratory pressure (PEEPi) are commonly observed in patients with severe chronic obstructive pulmonary disease (COPD) in acute respiratory failure. Previous studies have shown that externally applied PEEP reduces PEEPi and its adverse effects in mechanically-ventilated COPD patients. 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 patients in acute hypercapnic respiratory failure. Ten COPD patients admitted to the intensive care unit in acute hypercapnic respiratory failure were studied. Inspiratory effort was measured by the tidal excursions of oesophageal (Poes) and transdiaphragmatic (Pdi) pressure. Inspiratory effort and both the pressure-time product for the diaphragm (integral of Pdi-dt) and for the inspiratory muscles (integral of Poes.dt) were measured during the application of 5, 7.5, and 10 cmH2O of CPAP. Dyspnoea, gas exchange and pattern of breathing were also assessed. Inspiratory effort and the pressure-time product both for the diaphragm and the inspiratory muscles fell significantly with CPAP in a dose-dependent fashion. Both the pattern of breathing and level of dyspnoea improved with CPAP. End-expiratory lung volume remained stable at the lower levels of CPAP, with only modest increases at the higher levels. Arterial oxygen tension (Pa,O2) and arterial carbon dioxide tension (Pa,CO2) either improved or remained stable with CPAP. We conclude that the noninvasive application of CPAP to spontaneously breathing patients with severe COPD in acute respiratory failure decreases inspiratory effort and dyspnoea whilst improving breathing pattern. It is conceivable that the early institution of CPAP in this setting may obviate the need for intubation and conventional mechanical ventilation.
动态肺过度充气和内源性呼气末正压（PEEPi）的形成在急性呼吸衰竭的重度慢性阻塞性肺疾病（COPD）患者中很常见。既往研究表明，外部施加的PEEP可降低机械通气的COPD患者的PEEPi及其不良影响。本研究的目的是确定不同水平的持续气道正压（CPAP）对一组急性高碳酸血症性呼吸衰竭的自主呼吸、未插管的COPD患者吸气努力程度、呼吸模式、气体交换和呼吸困难程度的影响。对10例因急性高碳酸血症性呼吸衰竭入住重症监护病房的COPD患者进行了研究。通过食管压力（Poes）和跨膈压力（Pdi）的潮气量变化来测量吸气努力。在施加5、7.5和10 cmH2O的CPAP期间，测量吸气努力以及膈肌的压力-时间乘积（Pdi-dt积分）和吸气肌的压力-时间乘积（Poes.dt积分）。还评估了呼吸困难、气体交换和呼吸模式。CPAP以剂量依赖的方式显著降低了吸气努力以及膈肌和吸气肌的压力-时间乘积。CPAP改善了呼吸模式和呼吸困难程度。在较低水平的CPAP时，呼气末肺容积保持稳定，在较高水平时仅有适度增加。CPAP使动脉血氧分压（Pa,O2）和动脉血二氧化碳分压（Pa,CO2）有所改善或保持稳定。我们得出结论，对急性呼吸衰竭的重度COPD自主呼吸患者无创应用CPAP可降低吸气努力和呼吸困难，同时改善呼吸模式。可以设想，在这种情况下早期应用CPAP可能避免插管和传统机械通气的需要。
