Tobin M J, Jubran A, Hines E
Division of Pulmonary and Critical Care Medicine, Loyola University of Chicago Stritch School of Medicine, Maywood, Illinois.
Schweiz Med Wochenschr. 1994 Nov 26;124(47):2139-45.
Weaning patients from mechanical ventilation constitutes a major portion of the workload in an intensive care unit, as over 40% of total ventilator time is consumed by the weaning process. Several pathophysiological mechanisms may be responsible for weaning failure, but the precise role of each is incompletely understood. Patients who fail a weaning trial commonly develop hypercapnia, which appears to be due to decreased tidal volume rather than a primary decrease in respiratory drive. Respiratory muscle performance is impaired as a result of dynamic hyperinflation and paradoxic motion of the rib cage and abdomen. Worsening of pulmonary mechanics will cause further embarrassment of the respiratory muscles. However, the clinical importance of respiratory muscle fatigue remains unclear. Afferent stimuli arising in the lung parenchyma, respiratory muscles, or as a consequence of impaired gas exchange will be transmitted to the respiratory control centers and result in severe dyspnea in patients who fail a weaning trial.
使患者脱离机械通气是重症监护病房工作量的主要部分，因为撤机过程消耗了总通气时间的40%以上。几种病理生理机制可能导致撤机失败，但每种机制的确切作用尚未完全明确。撤机试验失败的患者通常会出现高碳酸血症，这似乎是由于潮气量减少而非呼吸驱动力的原发性降低所致。由于动态肺过度充气以及胸廓和腹部的反常运动，呼吸肌功能受损。肺力学的恶化将进一步使呼吸肌窘迫。然而，呼吸肌疲劳的临床重要性仍不清楚。肺实质、呼吸肌产生的传入刺激或气体交换受损的结果将被传递到呼吸控制中心，并导致撤机试验失败的患者出现严重呼吸困难。
