The diaphragm is the main muscle of inspiration, and its dysfunction contributes to adverse clinical outcomes in critically ill patients. The authors of this article recently reported the infiltration of SARS-CoV-2, and the development of fibrosis, in the diaphragm of critically ill patients with COVID-19. In the current study, they aimed to characterise myofiber structure in the diaphragm of critically ill patients with COVID-19. Diaphragm muscle specimens were collected during autopsy from patients who died of COVID-19 in three academic medical centres in the Netherlands in April and May 2020 (n=27). Diaphragm myofiber gene expression was studied and structure and compared the findings obtained to those of deceased critically ill patients without COVID-19 (n=10). Myofibers of critically ill patients with COVID-19 showed on average larger cross-sectional area (slow-twitch myofibers: 2441±229 vs 1571±309 µm2; fast-twitch myofibers: 1966±209 vs 1225±222 µm2). Four critically ill patients with COVID-19 showed extremely large myofibers, which were splitting and contained many centralised nuclei. RNA-sequencing data revealed differentially expressed genes involved in muscle regeneration. The authors concluded that diaphragm of critically ill patients with COVID-19 has distinct myopathic features compared with critically ill patients without COVID-19, which may contribute to the ongoing dyspnoea and fatigue in the patients surviving COVID-19 infection.
Shi Z, Bogaards SJP, Conijn S, Onderwater Y, Espinosa P, Bink DI, van den Berg M, van de Locht M, Bugiani M, van der Hoeven H, Boon RA, Heunks L, Ottenheijm CAC. COVID-19 is associated with distinct myopathic features in the diaphragm of critically ill patients. BMJ Open Respir Res. 2021 Sep;8(1):e001052. doi: 10.1136/bmjresp-2021-001052.