Cardiopulmonary exercise test in patients with persistent dyspnea after COVID-19 disease
Authors: Borrego Rodriguez J , Berenguel Senen A , De Cabo Porras C , Gallango Brejano M , Gigante Miravalles E , Morante Perea C , Serrano Blanco A , Gadella Fernandez A , Martinez Camara A , Sanchez-Aguilera Sanchez-Paulete P , Lazaro Salvador M , Flores Hernan M , Lozano Lazaro M G , Arias Palomares M A , Rodriguez Padial L 
Published: October 2021

Abstract

Introduction
Persistent dyspnea in patients who have suffered from COVID-19 disease has become a constant in cardiology in recent months. Healther workers have been one of the population groups mainly affected during the pandemic. Chronic involvement by COVID-19 infection, such as dyspnea, is frequent, and so far, of unknown mechanism. CardioPulmonary Exercise Test (CPET) is currently the gold standard technique in the differential diagnosis of dyspnea. Therefore, CPET could be useful in the evaluation of patients after infection by the SARS-COV2 virus; a role still unknown in this context.

Objective
Evaluate the parameters obtained in CPET in patients who had suffered from COVID-19 disease and who presented persistent dyspnea.

Methods
We conducted a single-center and prospective study that included healthcare workers who suffered from COVID-19 disease with mild-moderate intensity symptoms, without the need for hospitalization, between March-December 2020 and who presented dyspnea on exertion at least 3 months after infection, in the absence of structural heart disease. An echo was performed, and a baseline spirometry followed by a CPET. Some of the variables collected such as VO2, OUES and PulseO2 have been quantified as a percentage (%) of the predicted according to predicted equations.

Results
64 healthy patients with an active baseline life (without exertional dyspnea prior to infection) were included. 7 patients were excluded for presenting previously unknown structural heart disease. Of the 57 patients (Figure 1), more than half had a functional capacity lower than predicted (50th percentile), highlighting, among the cardiovascular response variables, a peak VO2 of 79% (SD: 14.0%) of the predicted, denoting slightly depressed functional capacity. In addition, in this subgroup, a VO2 at the level of the first ventilatory threshold (VT1) of 51.1% (SD: 4.2%) is observed over the predicted value -value that is considered in the lower limits of normality-; and a PulseO2 (systolic volume reflex) and an OUES in normal ranges with respect to those predicted. In the total of the 57 patients, no alterations were observed in the ventilatory efficiency parameters with effort, nor in the baseline spirometry, nor in the breathing reserve (BR), nor in final oxygen saturation (SatO2).

Conclusion
CPET has made it possible to identify that more than half of the patients show a deterioration -at least slight- in functional capacity (the majority of which are women) reaffirming the value of this test. The combination of this pattern that we observed in our serie is usually seen in patients with physical deconditioning and/or obesity, and is secondary to alterations in the peripheral use of oxygen, mainly at the muscular level. Based on this, a direct or indirect potential myopathic effect of the virus cannot be ruled out as responsible for the deterioration of the functional class of patients after COVID-19 disease.

Funding Acknowledgement
Type of funding sources: None.