Abstract
Background About one third of long COVID patients reports breathlessness and fatigue even during activities of daily living. We hypothesized that abnormalities of combined lung diffusing capacity for nitric oxide (DLNO) and carbon monoxide (DLCO) at rest or after mild exercise are associated with breathlessness in patients with long COVID.
Methods Single-breath combined DLNO and DLCO were measured at rest and immediately after a short bout of treadmill exercise simulating ordinary walking in 32 Caucasian patients with long COVID and dyspnea at rest. Twenty subjects served as a control group.
Results At rest, combined DLNO, DLCO, and alveolar volume (VA) were significantly lower in long COVID than in controls, with DLNO and DLCO being below the limits of normal in 69% and 41% of cases, respectively. Mean values of DLNO/VA and DLCO/VA in long COVID patients were less than controls yet, in only 22% and 12% of long COVID patients the values of DLNO/VA and DLCO/VA were below the limits of normal. After treadmill, DLNO, DLNO/DLCO, VA and heart rate increased significantly without differences between groups. DLNO remained below the limit of normal in 47% of long COVID.
Conclusion These data suggest localized discrete loss of lung units in about half of long COVID patients, not completely explained by loss of VA or of alveolar-capillary recruitment during exercise.
Footnotes
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- Received July 20, 2022.
- Accepted October 20, 2022.
- Copyright ©The authors 2022
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