Diaphragm Muscle Weakness Might Explain Exertional Dyspnea Fifteen Months After Hospitalization for COVID-19

Dyspnea is often a persistent symptom after acute coronavirus disease 2019 (COVID-19), even if cardiac and pulmonary function are normal.This study investigated diaphragm muscle strength in patients after COVID-19 and its relationship to unexplained dyspnea on exertion.Fifty patients previously hospitalized with COVID-19 (14 female, age 58±12 years, half of whom were treated with mechanical ventilation and half who were treated outside the intensive care unit) were evaluated using pulmonary function testing, 6-minute walk test, echocardiography, twitch transdiaphragmatic pressure following cervical magnetic stimulation of the phrenic nerve roots, and diaphragm ultrasound. Diaphragm function data were compared with values from a healthy control group.Moderate or severe dyspnea on exertion was present at 15 months after hospital discharge in approximately two-thirds of patients. No significant pulmonary function or echocardiography abnormalities were detected. Twitch transdiaphragmatic pressure was significantly impaired in post-COVID-19 patients compared with controls, independent of initial disease severity (14±8 vs. 21±3 cmH2O in mechanically ventilated patients versus controls [p=0.02], and 15±8 vs. 21±3 cmH2O in non-ventilated patients versus controls [p=0.04]). There was a significant association between twitch transdiaphragmatic pressure and the severity of dyspnea on exertion (p=0.03).Diaphragm muscle weakness was present 15 months after hospitalization for COVID-19 even in patients who did not require mechanical ventilation, and this weakness was associated with dyspnea on exertion. The current study therefore identifies diaphragm muscle weakness as a correlate for persistent dyspnea in patients after COVID-19 in whom lung and cardiac function are normal. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/).