This study investigated the effects of COVID-19 on respiratory muscles, particularly the diaphragm, in critically ill patients. Autopsy diaphragm specimens from 26 patients in the Netherlands that had been critically ill with COVID-19 (COVID-19-ICU) were compared with 8 diaphragm specimens from patients who had been critically ill without COVID-19. Both COVID-19-ICU patients and control patients received invasive mechanical ventilation and stayed in the ICU for comparable amounts of time. Compared to the control samples, diaphragm samples from COVID-19-ICU patients displayed increased expression of fibrosis pathways. Epimysial and perimysial fibrosis were 2-fold greater in COVID-19-ICU diaphragms compared to controls. The authors noted that the causal pathway between SARS-CoV-2 infection and diaphragm myopathy has not yet been established. They hypothesized that fibrosis of the diaphragm that is associated with COVID-19 might lead to ventilator complications, dyspnea, and fatigue in patients after their time in the ICU.