Passive Cycling Limits Myofibrillar Protein Catabolism in Unconscious Patients: A Pilot Study

Abstract

Background: To test the effects of passive cycling on muscle protein metabolism in unconscious patients. Materials and Methods: Twenty-seven patients (age 61.0 ± 16.4 years) admitted for coma (n=21) or with respiratory insufficiency requiring prolonged sedation were randomized to standard care (n=8) or passive cycling (2×30 minutes/day for 7 days, n=7). Longer-duration cycling (2×60 minutes/day, n=6) or passive cycling plus a hypercaloric hyperprotein diet (n=6) were assessed in separate groups. Ultrasound, biochemical and electrophysiological data were collected for 7 days. The thicknesses of the rectus femoris and of the vastus intermedius were measured by ultrasound. Myofibrillar protein catabolism was assessed by the urine 3- methylhistidine/creatinine ratio (3MH/creat). Findings: Passive cycling was well tolerated and resulted in a faster decrease in 3MH/creat and a slightly less negative nitrogen balance than standard care. These changes were not influenced by a longer duration of passive cycling or by a hypercaloric hyperprotein diet. There were no differences in muscle thicknesses or electromyographic data between standard care and passive cycling groups. Conclusions: Passive cycling in comatose or sedated patients was associated with less myofibrillar proteolysis. If confirmed in larger trials, this approach could help to prevent the long-term muscular consequences of prolonged inactivity in critically ill patients.