Long-term lung function trajectories in Swedish COVID-19 ICU survivors: a two-year follow-up study

Introduction Longitudinal studies of lung function following COVID-19 remain limited. This study examined lung function in COVID-19 patients for two years after discharge from an intensive care unit (ICU).Methods Patients treated for COVID-19 in Uppsala ICU (mean 11.1 days) were assessed at four months, one year, and two years post-discharge. Lung function tests included spirometry, diffusing capacity for carbon monoxide (DLco), and body plethysmography. Logistic regression adjusted for age, sex, and body mass index (BMI) assessed the association between impaired DLco and patients’ characteristics.Result A total of 104 patients (32% female, with a mean age of 60 years) participated in four months follow-up, 40 in one year follow-up, and 21 in two years follow-up after discharge. Impaired DLco was observed in 50%, 58%, and 33% of patients at four months, one year, and two years, respectively. A comparison showed that DLco% predicted declined from four months to one year (mean 79.0, SD 14.7, to 74.3, SD 15.7; p< 0.001), then improved between one and two years (p< 0.001). Forced vital capacity (FVC) % predicted improved between four months and one year (p < 0.001) and between one and two years (p = 0.004). Forced expiratory volume during the first second (FEV1) % predicted improved only between four months and one year (p = 0.002). Total lung capacity improved between the one- and two-year follow-ups (p = 0.006). Impaired DLco at four months was significantly associated with age ≥60 years (adjusted odds ratios, 95% confidence interval: 6.73 (2.64-17.12), mechanical ventilation (4.74 (1.82-12.34), longer ICU stay (5.84 (2.13-16.01), minimum lymphocyte count at ICU (0.19 (0.04-0.83), and FVC % predicted (0.93 (0.89-0.96)) and FEV1 % predicted (0.93 (0.89-0.97)).Conclusion Despite recovery between one and two years, one-third of patients exhibited impaired DLco two years after critical COVID-19, highlighting the need for pulmonary follow-up to address persistent lung function deficits.