Post COVID exertional dyspnea linked to diaphragm muscle weakness

A new study conducted by Binaya Regmi and team has revealed that even in patients who did not require mechanical breathing 15 months after hospitalization for COVID-19, diaphragm muscle weakening was evident, and this weakness was related with dyspnea on exercise. The findings of this study were published in American Journal Of Respiratory and Critical Care Medicine.

Even if cardiac and pulmonary function are good, dyspnea is a common long-term symptom of acute coronavirus illness (COVID-19). As a result, this study was carried out to assess diaphragm muscle strength in COVID-19 patients and its association to unexplained dyspnea on exercise.

Fifty patients with COVID-19 who had previously been hospitalized were evaluated using pulmonary function testing, 6-minute walk test, twitch transdiaphragmatic pressure post cervical magnetic stimulation of the phrenic nerve roots, echocardiography, and diaphragm ultrasound (14 female, age 58 12 yr, half of whom were treated with mechanical ventilation, and half of whom were treated outside the ICU). Data from diaphragm function were compared to results from a healthy control group.

The key findings of this study were:

1. At 15 months following hospital release, about two-thirds of patients had moderate or severe dyspnea on exercise.

2. There were no substantial pulmonary function or echocardiography abnormalities found.

3. Twitch transdiaphragmatic pressure was significantly lower in COVID-19 patients compared to controls, regardless of initial disease severity (14 8 vs. 21 3 cm H2O in mechanically ventilated patients vs. controls [P = 0.02], and 15 8 vs. 21 3 cm H2O in non-ventilated patients vs. controls [P = 0.04]).

4. There was a significant relationship (P = 0.03) between twitch transdiaphragmatic pressure and the degree of dyspnea on exercise.

In conclusion, this study found a pathophysiological cause, diaphragm muscle weakening, underpinning otherwise unexplained exertional dyspnea in COVID-19 patients who had previously been hospitalized. More study is needed to investigate if particular therapy targeting diaphragm muscle weakness, such as inspiratory muscle training, might be a helpful intervention in individuals with protracted COVID to alleviate exertional dyspnea.

Reference:

Regmi, B., Friedrich, J., Jörn, B., Senol, M., Giannoni, A., Boentert, M., Daher, A., Dreher, M., & Spiesshoefer, J. (2023). Diaphragm Muscle Weakness Might Explain Exertional Dyspnea 15 Months after Hospitalization for COVID-19. In American Journal of Respiratory and Critical Care Medicine (Vol. 207, Issue 8, pp. 1012–1021). American Thoracic Society. https://doi.org/10.1164/rccm.202206-1243oc