Lung function recovery in COVID-19 pneumonia patients slows down over time

Spontaneous recovery of lung function after COVID-19-related pneumonia may seem faster at first but occurs more slowly thereafter over a 6-month period, likely as a result of the different degree of severity of the disease, according to a study.

The researchers assessed lung function in 40 patients with COVID-19 pneumonia. They obtained spirometry measurements including lung volumes, mainly total lung capacity (TLC) and lung diffusion capacity for carbon monoxide (DLCO) at 3 months after hospital discharge. Patients who had restrictive ventilatory defect or impaired DLCO or both underwent re-evaluation at 6 months using global spirometry and high-resolution computed tomography scan of the chest.

Nineteen (48 percent) patients had normal pulmonary functional tests, while 21 (52 percent) showed residual lung function abnormalities at 3 months after hospital discharge. Among patients with lung function abnormalities, four (19 percent) had loss of lung volume only as evidenced by TLC reduction (group 1), 13 (62 percent) had reduced TLC and DLCO (group 2), and four (19 percent) had isolated reduction in DLCO (group 3).

At the 6-month follow-up, all patients in group 1 improved, although only one achieved normalization of TLC. In group 2, while TLC and DLCO increased significantly (p<0.01), only three patients reached normal values. In group 3, DLCO improved for most patients and normalized in 50 percent.

An internal-built chest high-resolution computed tomography scan severity score at 6 months was significantly associated with TLC (p<0.01) and DLCO (p<0.01).

The findings show the utility of pulmonary function tests for detecting the presence and nature of the residual lung damage after COVID-19-related pneumonia and for monitoring its natural course. The researchers stressed that patients who most likely will not recover at 6 months (and perhaps even better at 3 months) should be identified and treated accordingly to maximize the potential recovery of their pulmonary function.