Diaphragm dysfunction in severe COVID-19 as determined by neuromuscular ultrasound

Abstract

Many survivors from severe coronavirus disease 2019 (COVID-19) suffer from persistent dyspnea and fatigue long after resolution of the active infection. In a cohort of 21 consecutive severe post-COVID-19 survivors admitted to an inpatient rehabilitation hospital, 16 (76%) of them had at least one sonographic abnormality of diaphragm muscle structure or function. This corresponded to a significant reduction in diaphragm muscle contractility as represented by thickening ratio (muscle thickness at maximal inspiration/end-expiration) for the post-COVID-19 compared to non-COVID-19 cohorts. These findings may shed new light on neuromuscular respiratory dysfunction as a contributor to prolonged functional impairments after hospitalization for post-COVID-19.

FIGURE 1

Technique for neuromuscular ultrasound examination of hemi‐diaphragm. Top panel, thickness of diaphragm at end inspiration or total lung capacity (0.40 cm). Bottom panel, thickness of diaphragm at maximal expiration, or functional residual capacity (0.19 cm) with descending lung denoted by yellow asterisks. The diaphragm thickening ratio was calculated as 2.11 (0.40 cm/0.19 cm)

FIGURE 2

Sonographic diaphragm muscle comparisons in survivors of COVID‐19 that require inpatient rehabilitation as compared to controls. The more affected side of the two hemidiaphragms was plotted and compared between non‐COVID patients (blue) and COVID‐19 patients (red). Left panel, the diaphragm muscle thickness at end expiration was not statistically significant, p = 0.15. Right panel, the diaphragm muscle thickening ratio (i.e., contractility) was significantly reduced in the COVID‐19 cohort compared to non‐COVID cohort, p = 0.0004). The dotted horizontal lines indicate lower limit of normal for each parameter