Association between respiratory requirements during hospitalization for covid-19 and follow-up pfts

Introduction: The long-term effects of COVID-19 infection are an area of ongoing research. This study aims to describe the association between hospitalization-related factors and results of follow-up pulmonary function testing (PFT) within eight weeks of hospital discharge. Methods: We identified 138 patients referred to our COVID-19 Recovery Clinic who were hospitalized between July 2020 and March 2021, and who required supplemental oxygen during hospitalization. We abstracted patient demographic and clinical characteristics as well as follow-up PFT and six-minute walk testing (6MWT). Outcomes were stratified by total lung capacity (TLC) and diffusion capacity for carbon monoxide (DLCO) and compared using Fisher’s exact test. Results: The median age was 60 years, and the most common comorbidities were hypertension (58.7%), diabetes (34.1%), and obstructive sleep apnea (22.5%). Median hospital length of stay was 8 days with 69.1% admitted to the medical floor and 30.9% admitted to the intensive care unit. Chest imaging was abnormal on admission for 92.7%. The highest level of respiratory requirements during hospitalization was nasal cannula for 42.2%, high-flow blender for 37.2%, and mechanical ventilation for 20.6%. On follow-up testing in the COVID-19 Recovery Clinic, 57.6% had normal chest imaging with 26% showing interval improvement and 8.9% showing pulmonary fibrosis. When stratified by TLC, 68.2% had normal results, 17.3% had mild restriction, 9.1% had moderate restriction, and 5.5% had severe restriction. Of patients requiring only nasal cannula during hospitalization, 16.2% had abnormal TLC compared to 47.6% of those requiring mechanical ventilation (P = .003). When stratified by DLCO, 53.6% had normal results, 21.8% had mild impairment, 19.1% had moderate impairment, and 5.5% had severe impairment. Of patients requiring only nasal cannula during hospitalization, 13.6% had abnormal DLCO compared to 47.6% of those requiring mechanical ventilation (P = .026). Decreasing TLC and DLCO were associated with shorter distance on follow-up 6MWT (P = .032 and P < .001, respectively). Conclusions: Our findings suggest that higher respiratory requirements during hospitalization for COVID-19 were associated with abnormal TLC and DLCO on follow-up PFTs.