Pathophysiology of Weaning-Associated Respiratory Failure

Abstract

Weaning of a small proportion of patients receiving mechanical ventilatory support from mechanical ventilation poses a challenge to the clinician in charge of their care. In general, the etiology of unsuccessful weaning is related to the incomplete resolution of the underlying illness that dictates the need for ventilatory support, the development of ventilator-associated complications, or new problems. The cause of weaning failure is multi-factorial (Jubran and Tobin 1997; Vassilakopoulos et al. 1998), and an isolated factor can rarely be defined. Regardless of the etiologies, the fundamental derangement underlying weaning-associated respiratory failure is a decrease in respiratory neuromuscular capacity (Table 9.1) and an excessive load to the respiratory system (Table 9.2), particularly the respiratory muscles (Tobin et al. 1998). The pattern of breathing in these patients is generally rapid and shallow (Jubran and Tobin 1997). The best method for determining the interplay among the factors involved in weaning failure is an experimental design, with the patients acting as their own control during both failed and successful trials. The two most recent studies which have met the above criterion (Vassilakopoulos et al. 1998, Capdevila et al. 1998) will be the basis of this review article.

Supported by the Department of Veterans Affairs Medical Research Service