Sonographic follow-up of diaphragm function in COVID-19: an exploratory study.

Introduction: Survivors of COVID-19 frequently endure chronic disabilities. We hypothesise that diaphragm function has a long recovery time after COVID-19 hospitalisation and may play a role in post-COVID-19 syndrome. The aim of this study was to assess diaphragm function during COVID-19 hospitalisation and during recovery. Methods: We conducted a prospective single-centre cohort study in 49 enrolled patients, of which 28 completed 1-year follow-up. Participants were evaluated for diaphragm function. Diaphragm function was assessed using ultrasound measuring of diaphragm thickening fraction (TF) within 24 h after admission, after 7 days of admission or at discharge, whichever came first, and 3 and 12 months after hospital admission. Results: Estimated mean TF increased from 0.56 (95% CI 0.46-0.66) on admission to 0.78 (95% CI 0.65-0.89) at discharge or 7 days after admission, to 1.05 (95% CI 0.83-1.26) 3 months after admission and to 1.54 (95% CI 1.31-1.76) 12 months after admission. The improvements from admission to discharge, 3 months and 12 months were all significant (linear mixed modelling; p=0.020, p<0.001 and p<0.001, respectively), and the improvement from discharge to 3-month follow-up was borderline significant (p<0.1). Conclusion: Diaphragm function was impaired during hospitalisation for COVID-19. During recovery in hospital and up to 1-year follow-up, diaphragm TF improved, suggesting a long recovery time of the diaphragm. Diaphragm ultrasound may be a valuable modality in the screening and follow-up of (post-)COVID-19 patients for diaphragm dysfunction.