A Retrospective Analysis of DLCO Changes in Post-Acute Sequelae of SARS-CoV-2 Infection

ABSTRACT

Rationale Over 350,000,000 people have had SARS-CoV-2 infection worldwide. COVID-19 poses many challenges in the management of patients causing a long-term and significant burden on the healthcare system. Understanding the long-term complications is a challenge that the healthcare community and patients will face. To our knowledge, this is one of the largest retrospective analyses with the aim to understand the functional lung sequelae of the disease. Methods: We retrospectively reviewed 782 survivors who had COVID-19 diagnosed by RT-PCR and followed up at an outpatient pulmonary clinic in Hartford, Connecticut, USA, from March 2020 to June 2021. Data included patient's age, sex, comorbidities, pulmonary function tests (PFT), the maximal requirement of low-flow oxygen (LF), high-flow nasal cannula (HFNC), non-invasive ventilation (NIV) and mechanical ventilation (MV). We performed an adjusted logistic regression model to evaluate if severity of disease according to maximal oxygen support is associated with DLCO<80% in follow-up. SPSS IBM was used for the statistical modeling. Results: Of the 782 patients evaluated, 314 patients had PFT results available post COVID-19 for analysis. The mean age was 58.9±14.5 years, and of the total number of patients, 200 were female (63.7%). Other demographics are as follows 156 (49.7%) were obese, 129 (41.2%) had asthma, 48 (15.3%) had COPD, 5 (1.6%) had Interstitial Lung Disease, 35 (11.1%) had anemia, 70 (22.3%) had diabetes mellitus, 164 (52.2%) had hypertension, 26 (8.3%) had heart failure. Only 14 (4.4%) required MV, 14 (4.5%) NIV, 29 (9.2%) HFNC, 94 (29.9%) LF and 153 (51.9%) remained on room air. Altered DLCO was seen in 107 patients (34.1%), 189 (60.1%) had normal DLCO, and 18 (5.7%) did not have DLCO, of which the latter were excluded from the analysis. Maximal oxygen support was associated with DLCO<80% on unadjusted analysis (p=0.003). However, it was not associated with DLCO<80% (p=0.2) when adjusted. Other variables associated with a higher risk of DLCO<80% were age (p<0.001) and COPD (p<0.028). Asthma was associated with lower risk of developing DLCO<80% (p<0.001). Conclusion: Patients with post-acute sequelae of SARS-CoV-2 infection can develop DLCO<80%, which may contribute to long-term symptoms. Altered DLCO was not associated with maximal oxygen support in the adjusted logistic regression analysis. However, this may be due to the low number of cases requiring MV or NIV, resulting in selection bias, given there was a higher mortality rate in patients requiring positive pressure ventilation. Additionally, age and COPD were correlated with DLCO<80%.