Effects of SARS-CoV-2 Infection on Pulmonary Function Tests and Exercise Tolerance

Introduction: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been shown to cause long-term pulmonary sequelae. Objects: The aim of this study was to evaluate the consequences of the SARS-CoV-2 infection on pulmonary function and on the 6-min walk test related to the severity of the disease. Methods: A cross-sectional study was conducted at the "Policlinico Tor Vergata" Academic Hospital (Rome, Italy), including 75 patients evaluated in post-COVID clinics at the Respiratory Units between November 2020 and September 2021. Complete pulmonary function tests, 6-min walk tests and persistence of symptoms were performed. Results: Of the 75 subjects, 23 had mild, 16 moderate, 26 severe and 10 very severe COVID-19, classified according to WHO. Very severe patients had a lower FVC (100 ± 10%pr) compared to the other groups (116 ± 16%pr, 116 ± 13%pr, 122 ± 20%pr from mild to severe; p < 0.05) and a lower TLC (94 ± 13%pr) compared to the others (102 ± 10%pr, 108 ± 15%pr, 108 ± 12%pr from mild to severe; p < 0.05). DLco and DLco/VA were similar among groups. At the 6MWT, distance, rest and nadir SpO2 were similar among groups, but all groups presented a significant decrease in SpO2 from rest to nadir (Rest SpO2: 97.0 ± 1.0% vs. Nadir SpO2: 93.6 ± 2.7%, p < 0.01). A positive correlation was found between desaturation and delta SpO2 (rest-nadir) (R: 0.29, p < 0.05) and the Distance Desaturation Product (R: 0.39, p < 0.01). Conclusions: These results showed that, although the PFTs are within the normal range, there is still a mild restrictive spirometric pattern after six months in very severe subjects. Moreover, the only persistent pathological sequalae of SARS-CoV-2 infection were a mild desaturation at 6MWT, despite the severity of the infection.