LAUSR

Introduction Critical illness myopathy is a disabling condition that develops in critically ill patients and presents as diffuse muscle weakness and failure to wean from mechanical ventilation. Muscle Velocity Recovery Cycles (MVRC) enable in vivo assessment of muscle membrane properties. We aimed in this study to examine whether MVRC may detect changes in patients with delayed wean from mechanical ventilation. Methods Six patients (mean age: 52.4 ± 5.8) with failure to wean from mechanical ventilation and 24 healthy controls (mean age: 53.2 ± 3.2) were prospectively included. In addition to conventional nerve conduction studies (NCS) and electromyography, all patients were examined by MVRC in the anterior tibial muscle using Qtrac-software. MVRC parameters consisted of muscle relative refractory period (MRRP) and early and late supernormality after 1, 2 or 5 conditioning stimuli. Results Motor NCS of peroneal and tibial and sensory NCS of sural nerves were normal. None of the patients had spontaneous activity and quantitative motor unit potential analysis was normal. MRRP was significantly prolonged in patients (5.9 ± 0.7) compared to healthy controls (3.6 ± 0.09), and early supernormality was lower in patients than healthy controls after 2 (5.1 ± 1.1 vs 11.3 ± 0.4) and 5 (4.6 ± 1.1 vs 13.5 ± 0.4) conditioning stimuli. Similarly, late supernormality was decreased in patients compared to healthy controls after 1 (2.4 ± 0.5 vs 3.9 ± 0.2), 2 (1.4 ± 0.4 vs 2.8 ± 0.1) and 5 (3.1 ± 0.8 vs 7.9 ± 0.2) conditioning stimuli (t test, p  Conclusion Changes in MVRC in patients with failure to wean from mechanical ventilation may suggest critical illness myopathy in these patients. MVRC may detect changes in the muscle membrane before spontaneous activity and motor unit potential changes are seen. Future studies with larger patient groups and follow-up examinations are needed.