Does inspiratory muscle training affect expiratory muscle thickness in respiratory intensive care patients? A pilot randomized controlled study

Abstract

Background: This randomized controlled trial aimed to compare abdominal muscle thickness between intensive care patients and healthy controls, and to evaluate the impact of IMT on expiratory muscle thickness using ultrasound. Methods: In this single-blind randomized controlled trial, 20 post-extubation intensive care patients were randomly assigned to either an a conventional physiotherapy (CP) group or IMT + CP group. Both interventions were applied for five days. An additional 10 healthy individuals served as controls for comparison. Abdominal muscle thicknesses-including external oblique (EOA), internal oblique (IOA), transversus abdominis (TRA), and rectus abdominis (RA)-were measured using ultrasound. Maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP) were also recorded. Results: At baseline, healthy controls had significantly higher MIP, MIP% predicted, MEP, MEP% predicted, and RA muscle thickness compared to both patient groups (p < 0.05). Following intervention, both IMT and CP groups showed significant improvements in MIP (p < 0.05), but only the IMT group demonstrated significant increases in MEP, MEP% predicted, IOA, and RA muscle thickness (p < 0.05). The IMT group showed significantly greater improvements in MIP, MEP, IOA, and RA muscle thickness compared to the CP group (p < 0.05). Conclusion: Post-extubation IMT may improve not only inspiratory but also expiratory muscle strength and abdominal wall thickness. These findings suggest that IMT could support weaning processes in intensive care, although larger studies are needed.