Assessment of respiratory function and exercise tolerance at 4-6 months after COVID-19 infection in patients with pneumonia of different severity

Background: The evaluation of COVID-19 systemic consequences is a wide research field in which respiratory function assessment has a pivotal role. However, the available data in the literature are still sparse and need further strengthening. Aim: To assess respiratory function 4-6 months after hospital discharge based on lung disease severity in patients who overcome COVID-19 pneumonia. Methods: Patients hospitalised either in the Internal Medicine Department (IMD) for moderate to severe disease or in the Intensive Care Unit (ICU) for critical disease underwent spirometry with maximal flow-volume curve, lung volumes, lung diffusion capacity (DLCO ) and six-minute walking test (6-MWT). Results: Eighty-eight patients were analysed: 40 from the IMD and 48 from the ICU. In both cohorts, there was a greater prevalence of male patients. In the IMD cohort, 38% of patients showed at least one altered respiratory parameter, while 62% in the ICU cohort did so (P < 0.05). Total lung capacity (TLC) and DLCO were the most frequently altered parameters: 15% and 33% from IMD versus 33% and 56% from ICU, respectively (P < 0.05). In IMD patients, 5% had only restrictive deficit, 22% had only lung diffusion impairment and 10% had both. In ICU patients, 6% had only restrictive deficit, 29% had only lung diffusion impairment and 27% had both (P < 0.05). ICU patients showed a higher frequency of abnormal 6-MWT (P < 0.05). Conclusion: Lung function tests and 6-MWT are highly informative tools for monitoring the negative consequences of COVID-19 pneumonia, which were more frequent and more complex in patients discharged from ICU.