Skeletal muscle dysfunction in lung transplantation

Abstract

Patients with chronic lung disease have decreased exercise capacity due to reduced maximal oxygen utilization (VO2max). Interestingly, this exercise abnormality is found to persist despite marked improvement of ventilatory function after organ transplantation. 1 Lands LC, Smountas AA, Messiano J, et al. Maximal exercise capacity and peripheral skeletal muscle function following lung transplantation. Am Rev Respir Crit Care Med 1995;A523. Google Scholar , 2 Myioshi S Trulock E.P Schaefers H Hsieh C Patterson G.A Cooper J.D Cardiopulmonary exercise testing after single and double lung transplantation. Chest. 1990; 97: 1130-1136 Crossref PubMed Scopus (76) Google Scholar , 3 Schwaiblmair M, Dienemann H, Kolbe T, Vogelmeier C, Reichart B and Munich Lung Transplant Group. Cardiopulmonary exercise responses before and after lung transplantation. Am Rev Respir Crit Care Med 1996;A828. Google Scholar A growing number of observations have suggested a dysfunction in skeletal muscle oxidative metabolism as an important contributor to reductions in VO2max in both groups (chronic lung disease and lung transplant recipients). These findings may represent the persistence of an ongoing abnormality not improved by recovery of pulmonary function. Other concomitant factors resulting in exercise limitation have been the subject of investigations. Some of these are the effects of prolonged physical deconditioning, muscular aging and permanent damage secondary to muscle disuse or immobilization by altering muscle fiber types and functioning. Abnormalities in oxygen handling and transportation may also be involved, such as changes in muscular capillary distribution, oxygen flow or transport to the mitochondria or its utilization by oxidative enzymatic mechanisms. Side effects of immunosuppressants, steroids and cytotoxic medications could also be involved in many different steps of these processes. It also appears that skeletal muscle abnormalities and associated contributing factors may be seen in other chronic diseases, such as heart failure and renal insufficiency.