Medium-term impact of COVID-19 on pulmonary function, functional capacity and quality of life

Abstract

Background: Coronavirus disease 2019 (COVID-19) has spread worldwide, having a dramatic impact on healthcare systems. The aim of this study is to evaluate mid-term clinical impact of COVID-19 on respiratory function.

Methods: 379 patients were evaluated 4 months after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnosis. Patients were divided in two groups based on the presence of pneumonia during COVID-19. Clinical conditions, quality of life, symptomatology, 6-min walk test, pulmonary function test with spirometry and diffusing capacity of the lung for carbon monoxide were analysed. Data were compared to clinical evolution during COVID-19 (development of acute respiratory distress syndrome, need of invasive mechanical ventilation, partial oxygen saturation (S _pO2 )/inspiratory oxygen fraction (F _IO2 ) ratio and pneumonia severity index (PSI)).

Results: After a median 135 days, 260 (68.6%) out of 379 patients referred at least one symptom. Patients who developed pneumonia during COVID-19 showed lower S _pO2 at rest (p<0.001), S _pO2 during 6-min walk test (p<0.001), total lung capacity (p<0.001), airway occlusion pressure after 0.1 s (P _0.1) (p=0.02), P _0.1/maximal inspiratory pressure ratio (p=0.005) and higher Borg category-ratio scale (p=0.006) and modified Medical Research Council breathlessness scale (p=0.003), compared to patients without pneumonia. S _pO2 /F _IO2 ratio and PSI during SARS-CoV-2 pneumonia were directly associated with mid-term alteration of S _pO2 at rest (p<0.001) and during 6-min walk test (p<0.001), residual volume (p<0.001), total lung capacity (p<0.001 and p=0.003, respectively) and forced vital capacity (p=0.004 and p=0.03, respectively).

Conclusion: Lung damage during COVID-19 correlates to the reduction of pulmonary function 4 months after acute infection.

FIGURE 1

Scatter plot showing significant correlation between partial oxygen saturation (S_pO2)/inspiratory oxygen fraction (F_IO2) ratio during severe acute respiratory syndrome coronavirus 2 disease and pulmonary function and 6-min walk test (6MWT) parameters. TLC: total lung capacity; RV: residual volume; FVC: forced vital capacity; MEP: maximal expiratory pressure.

FIGURE 2

Scatter plot showing significant correlation between time since diagnosis and a) 6-min walk distance (6MWD) and b) diffusing capacity of the lung for carbon monoxide (D_LCO)/alveolar volume (V_A) ratio.