Sonographic evaluation of diaphragmatic function in critically ill patients on non-invasive ventilation and invasive mechanical ventilation

Background: Diaphragmatic dysfunction develops early during ventilatory support and delays liberation. Ultrasonography allows repeated bedside assessment, but data comparing non-invasive with invasive ventilation remain limited. Aims and Objectives: The aim of the study was to compare serial sonographic measures of diaphragmatic function between the two modes and relate them to recovery. Materials and Methods: One hundred and fourteen critically ill adults were enrolled over 24 months: 57 on non-invasive ventilation (Group 1) and 57 on invasive ventilation (Group 2). Diaphragmatic thickness, thickening fraction and excursion were measured on days 0, 3, 5 and 7. Analysis used the Chi-square test, unpaired t-test and a parsimonious binary logistic regression restricted to day 0 parameters and group. Results: Baseline variables were comparable. Thickening fraction was higher in Group 1 at every time point, reaching 43.74% versus 29.14% on day 7 (P<0.001). Excursion was similar until day 5, after which it was greater in Group 1 (P=0.002). Thickness rose in Group 1 and fell in Group 2 (day 7: 1.99 vs. 1.43 mm, P<0.001). Functional improvement occurred in 57.9% of Group 1 against 29.8% of Group 2 (P=0.003); stay was shorter (P=0.008). On multivariable analysis, day 0 thickening fraction (odds ratio [OR] 1.12, 95% confidence interval [95% CI] 1.05–1.20) and non-invasive support (OR 2.57, 95% CI 1.03–6.40) independently predicted improvement; excursion and thickness did not. Conclusion: Diaphragmatic function was better preserved during non-invasive support. Baseline thickening fraction independently predicted recovery, so a single admission scan may have prognostic value. Without baseline severity scoring, these associations cannot be interpreted causally.