Alterations in Respiratory Function Test Three Months after Hospitalisation for COVID-19 Pneumonia: Value of...

Three to four months after hospitalisation for COVID-19 pneumonia, the most frequently described alteration in respiratory function tests (RFTs) is decreased carbon monoxide transfer capacity (DL_CO).

This is a prospective cohort study that included patients hospitalised because of SARS-CoV-2 pneumonia, three months after their discharge. A clinical evaluation, analytical parameters, chest X-ray, six-minute walk test, spirometry and DL_CO-DL_NO analysis were performed. Demographic variables, comorbidities, and variables related to the severity of the admission were recorded.

Two hundred patients completed the study; 59.5% men, age 62 years, 15.5% admitted to the intensive care unit. The most frequent functional alteration, in 27% of patients, was in the DL_CO-DL_NO combination. This alteration was associated with age, male sex, degree of dyspnoea, poorer perception of health, and limited ability for physical effort. These patients also presented higher levels of D-Dimer and more residual radiological alterations. In 42% of the patients with diffusion alterations, only reduced DL_NO was presented, along with lower D-Dimer levels and less capillary volume involvement. The severity of the process was associated with the reduction in DL_CO-DL_NO.

The most sensitive RFT for the detection of the sequelae of COVID-19 pneumonia was the combined measurement of DL_CO-DL_NO and this factor was related to patient health status and their capacity for physical exertion. In 40% of these cases, there was only a reduction in DL_NO, a finding that may indicate less pulmonary vascular involvement.