Diminished respiratory muscle endurance persists after cardiac transplantation

Although maximal sustainable ventilatory capacity was reduced in CHF and transplant patients, it is important to emphasize that the work performed by these patients may not be similar to that of the normal subjects. External work performed by both groups was identical, although the internal work was different. Increased work of breathing in patients may be the mechanism producing the apparent diminished endurance. Indeed, the major limitation of this study is failure to measure the work of breathing. In patients with CHF, an elevated work of breathing is well described. Although pulmonary hypertension rapidly resolves after transplantation, chronic fibrotic pulmonary parenchymal changes may occur which could lead to decreased lung compliance and an increased work of breathing. Most probably, it is a combination of both increased work of breathing and decreased endurance that leads to the reduction in maximal sustainable ventilatory capacity in these patients.