Pulmonary function and functional capacity in COVID-19 survivors with persistent dyspnoea

1. Introduction

Emerging research shows a burden of chronic symptoms and reduced quality of life in coronavirus disease 2019 (COVID-19) survivors (Carfi et al., 2020; Wong et al., 2020). Approximately half of patients recovering from COVID-19 report chronic dyspnoea 2–3 months after infection (Carfi et al., 2020; Garrigues et al., 2020; Wong et al., 2020). Dyspnoea is an independent predictor of morbidity and mortality in the general population and is associated with reduced functional capacity and adverse health-related quality-of-life (Laviolette et al., 2014). This complex and multidimensional symptom can result in a downward spiral of activity avoidance, deconditioning, and ultimately the inability to perform basic activities of daily living (Moxham and Jolley, 2009). Whether COVID-19 survivors with persistent dyspnoea ultimately enter this downward spiral is unknown. More research is needed to understand the mechanisms of persistent dyspnoea in survivors of COVID-19 in order to improve patient management following infection.

A growing body of literature indicates the presence of racial and ethnic disparities in COVID-19-related infections and hospitalizations (Mackey et al., 2020; Ogedegbe et al., 2020). A recent systematic review concluded that Hispanic populations experience a disproportionate burden of severe COVID-19 and have increased mortality (Mackey et al., 2020). Racial and ethnic disparities may be at least partly attributable to the higher rates of comorbidities that worsen COVID-19 outcomes. Mexico has a high prevalence of chronic non-communicable diseases (Parra-Rodriguez et al., 2020), with diabetes, obesity, and the presence of more than one comorbidity all being independently associated with laboratory-confirmed COVID-19, need for hospitalization, and adverse outcomes (Giannouchos et al., 2020). Unfortunately, there is limited data on persistent COVID-19 symptoms, and particularly dyspnoea, in this population. Understanding differences in pulmonary function, comorbidities, and functional capacity between those with and without persistent dyspnoea may provide insight into the mechanisms of this symptom in individuals who are susceptible to the negative lasting effects of COVID-19. Accordingly, the purpose of this study was to compare spirometry, diffusing capacity of the lungs for carbon monoxide (D_LCO), and 6-minute walk distance (6MWD) in Mexican survivors of COVID-19 with and without persistent dyspnoea. We hypothesized that COVID-19 patients with persistent dyspnoea would have lower forced vital capacity (FVC), D_LCO, and 6MWD compared to patients without persistent dyspnoea, suggesting a physiologic driver of this persistent symptom.

2. Material and methods