Lung diffusion capacity impairment common among COVID-19 survivors

Impairment of lung diffusion capacity, which correlated with severity of disease, appeared to be the most common lung function abnormality among a series of patients who recovered from COVID-19 in China, according to a research letter published in the European Respiratory Journal.

“Persistent impairment of pulmonary function and exercise capacity have been known to last for months or even years in the recovered survivors with other coronavirus pneumonia (severe acute respiratory syndrome/SARS and Middle East respiratory syndrome/MERS). However, until now, there is no report in regard to pulmonary function in discharged COVID-19 survivors,” the researchers wrote.

From Feb. 5 to March 17, the researchers recruited 110 patients with COVID-19 who were hospitalized and subsequently discharged from the Guangzhou Eighth People’s Hospital in China. Using WHO interim guidance as well as guidance from China, 24 patients were categorized as having mild illness, 67 had pneumonia and 19 had severe pneumonia. Those with critical illness were excluded from the study.

Of the patients evaluated, the mean age was 49.1 years, 50% were women and 40% had at least one underlying comorbidity, including 23.6% with hypertension and 8.2% with diabetes. Only three patients had chronic respiratory diseases, including one patient with asthma, one with chronic bronchitis and one with bronchiectasis.

Spirometry and pulmonary diffusion capacity tests were administered on the day of or 1 day before hospital discharge. Results revealed anomalies in diffusing capacity of the lungs for carbon monoxide, or DLCO, in 47.2% of cases, total lung capacity in 25% of cases, FEV₁ in 13.6% of cases, FVC in 9.1% of cases, ratio of FEV₁ to FVC in 4.5% of cases and small airway function in 7.3% of cases.

Notably, the researchers found that impaired DLCO differed according to disease severity, with 30.4% of patients with mild illness, 42.4% with pneumonia and 84.2% with severe pneumonia (P < .05) demonstrating impaired DLCO. The DLCO percent predicted also declined with worsening disease, according to the data.

“This trend of the gradual decrease in level of DLCO among patients was identical with the varying degree of severity,” they wrote. “For about half (25/51) of the DLCO-impaired patients, the DLCO corrected for alveolar volume (DLCO/VA) was still within the normal range, which might indicate that DLCO decrease was more than the DLCO/VA in recovered subjects.”

The researchers also noted that the value of total lung capacity percent predicted in patients with severe pneumonia was less than that in patients with pneumonia or mild illness, which may signal a higher impairment of lung volume in severe cases.

“Our study firstly reveals that, in discharged survivors with COVID-19, impairment of diffusion capacity is the most common abnormality of lung function followed by restrictive ventilatory defect, which are both associated with the severity of the disease,” they wrote. “Pulmonary function test (not only spirometry, but also diffusion capacity) should be considered to perform in routine clinical follow-up for certain recovered survivors, especially in severe cases. Long-term studies are needed to address whether these defects are persistent.” – by Melissa Foster

Disclosures: The authors report no relevant financial disclosures.