von Gruenewaldt, Anna; Nylander, Eva; Hedman, Kristofer.

Physiological Reports. 10(4):e15197, 2022 02.

Reduced exercise capacity and several limiting symptoms during exercise
have been reported following severe acute respiratory syndrome
coronavirus-2 (SARS-CoV-2) infection. From clinical observations, we
hypothesized that an abnormal breathing pattern (BrP) during exercise may
be common in these patients and related to reduced exercise capacity. We
aimed to (a) evaluate a method to classify the BrP as normal/abnormal or
borderline in terms of inter-rater agreement; (b) determine the occurrence
of an abnormal BrP in patients with post-COVID; and (c) compare
characteristics of post-COVID patients with normal and abnormal BrP. In a
retrospective, cross-sectional study of patients referred for CPET due to
post-COVID April 2020-April 2021, we selected subjects without a history
of intensive care and with available medical records. Three raters
independently categorized patients’ BrP as normal, abnormal, or
borderline, using four traditional CPET plots (respiratory exchange ratio,
tidal volume over ventilation, ventilatory equivalent for oxygen, and
ventilation over time). Out of 20 patients (11 male), 10 were categorized
as having a normal, 7 an abnormal, and three a borderline BrP. Inter-rater
agreement was good (Fleiss’ kappa: 0.66 [0.66-0.67]). Subjects with an
abnormal BrP had lower peak ventilation, lower exercise capacity, similar
ventilatory efficiency and a similar level of dyspnea at peak exercise, as
did subjects with a normal BrP. Patients’ BrP was possible to classify
with good agreement between observers. A third of patients had an abnormal
BrP, associated with lower exercise capacity, which could possibly explain
exercise related symptoms in some patients with post-COVID syndrome.