28 diciembre, 2021

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


Dyspnoea persists in many patients following COVID-19 infection.

COVID-19 patients with persistent dyspnoea have impaired spirometry and gas exchange.

COVID-19 patients with persistent dyspnoea have reduced exercise performance.


The purpose of this study was to examine the physiological mechanisms of persistent dyspnoea in COVID-19 survivors. Non-critical patients (n = 186) with varying degrees of COVID-19 severity reported persistent symptoms using a standardized questionnaire and underwent pulmonary function and 6-minute walk testing between 30 and 90 days following the onset of acute COVID-19 symptoms. Patients were divided into those with (n = 70) and without (n = 116) persistent dyspnoea. Patients with persistent dyspnoea had significantly lower FVC (p = 0.03), FEV1 (p = 0.04), DLCO (p = 0.01), 6-minute walk distance (% predicted, p = 0.03), and end-exercise oxygen saturation (p < 0.001), and higher Borg 0-10 ratings of dyspnoea and fatigue (both p < 0.001) compared to patients without persistent dyspnoea. We have shown that dyspnoea is a common persistent symptom across varying degrees of initial COVID-19 severity. Patients with persistent dyspnoea had greater restriction on spirometry, lower DLCO, reduced functional capacity, and increased exertional desaturation and symptoms. This suggests that there is a true physiological mechanism that may explain persistent dyspnoea after COVID-19.

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 (DLCO), 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), DLCO, and 6MWD compared to patients without persistent dyspnoea, suggesting a physiologic driver of this persistent symptom.

2. Material and methods

This study received ethical approval (#2020-024) from the Hospital Regional de Alta Especialidad de la Peninsula de Yucatan and all patients provided written informed consent. Non-critically ill patients who tested positive for SARS-CoV-2 based on real-time reverse transcriptase-polymerase chain reaction on nasal swabs were identified from hospital records and subsequently contacted to participate. COVID-19 severity was classified as mild (ambulatory without hypoxemia), moderate (ambulatory but requiring supplemental O2 of ≤5 L/min), or severe (hospitalized with O2 >5 L/min and in the prone position for at least 12 h per day but without invasive mechanical ventilation). Follow-up testing occurred between 30 and 90 days after the onset of acute COVID-19 symptoms. Following the administration of a standardized questionnaire to determine the presence or absence of persistent symptoms (see list in Table 1) (Carfi et al., 2020), participants completed spirometry, DLCO, and a 6-minute walk test (6MWT) according to recommended guidelines (Holland et al., 2014; MacIntyre et al., 2005; Miller et al., 2005) with data being expressed relative to predicted values (Enright and Sherrill, 1998; Hankinson et al., 1999; Stanojevic et al., 2017). Spirometry and DLCO were performed using calibrated equipment (Ultima PF™ Pulmonary Function System, Medical Graphics, UK or Easy One Pro®, ndd Medical Technologies, Switzerland). Peripheral oxygen saturation via finger oximetry (Masimo RAD 5; Masimo Corporation, USA) was measured throughout the 6MWT. Independent t-tests and Fisher’s Exact test were used where appropriate to compare groups with and without persistent dyspnoea and fatigue. A p-value <0.05 was considered statistically significant. Data are presented as mean ± SD unless otherwise specified.

Créditos: Comité científico Covid

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