Functional Capacity in Patients Who Recovered from Mild COVID-19 with Exertional Dyspnea

Background: Post mild COVID-19 dyspnea is poorly understood. We assessed physiologic limitations in these patients. Methods: Patients with post mild COVID-19 dyspnea (group A) were compared (pulmonary function tests, 6-min walk test (6MWT), echocardiography and cardiopulmonary exercise test (CPET)) to post moderate/severe COVID-19 (group B) and to CPET and spirometry of patients with unexplained dyspnea (group C). Results: The study included 36 patients (13 in A, 9 in B and 14 in C). Diffusion capacity was lower in group B compared to group A (64 ± 8 vs. 85 ± 9% predicted, p = 0.014). 6MWT was normal and similar in both patient groups. Oxygen uptake was higher in group A compared to groups B and C (108 ± 14 vs. 92 ± 13 and 91 ± 23% predicted, p = 0.013, 0.03, respectively). O(2) pulse was normal in all three groups but significantly higher in the mild group compared to the control group. Breathing reserve was low/borderline in 2/13 patients in the mild group, 2/9 in the moderate/severe group and 3/14 in the control group (NS). Conclusions: Patients with post mild COVID-19 dyspnea had normal CPET, similar to patients with unexplained dyspnea. Other mechanisms should be investigated and the added value of CPET to patients with post mild COVID-19 dyspnea is questionable.