Alterations in Respiratory and Limb Muscle Strength and Size in Patients With Sepsis Who Are Mechanically Ventilated

Abstract

Background Skeletal muscle wasting and weakness are common in patients with sepsis in the intensive care unit, although less is known about deficits in diaphragm and limb muscles when mechanical ventilation also is required. Objective The objective of this study was to concurrently investigate relative differences in both thickness and strength of respiratory and peripheral muscles during routine care. Design A prospective, cross-sectional study of 16 alert patients with sepsis and 16 people who were healthy (control group) was used. Methods Assessment was made of the diaphragm, upper arm, forearm, and thigh muscle thicknesses with the use of ultrasound; respiratory muscle strength by means of maximal inspiratory pressure; and isometric handgrip, elbow flexion, and knee extension forces with the use of portable dynamometry. To describe relative changes, data also were normalized to fat-free body mass (FFM) measured by bioelectrical impedance spectroscopy. Results Patients (9 men, 7 women; mean age=62 years, SD=17) were assessed after a median of 16 days (interquartile range=11–29) of intensive care unit admission. Patients' diaphragm thickness did not differ from that of the control group, even for a given FFM. When normalized to FFM, only the difference in patients' mid-thigh muscle size significantly deviated from that of the control group. Within the patient sample, all peripheral muscle groups were thinner compared with the diaphragm. Patients were significantly weaker than were the control group participants in all muscle groups, including for a given FFM. Within the critically ill group, limb weakness was greater than the already-significant respiratory muscle weakness. Limitations Volitional strength tests were applied such that successive measurements from earlier in the course of illness could not be reliably obtained. Conclusions When measured at bedside, survivors of sepsis and a period of mechanical ventilation may have respiratory muscle weakness without remarkable diaphragm wasting. Furthermore, deficits in peripheral muscle strength and size may exceed those in the diaphragm.