Impaired Respiratory Function Post COVID-19 Associated With ICU Treatment

Impairments in respiratory function and exercise capacity are common post COVID-19 pneumonia, especially among those who required intensive care unit (ICU) treatment, according to study findings published in BMJ Open Respiratory Research.

Investigators assessed the relationship between COVID-19 illness severity and dyspnea, exercise capacity, spirometry results, and gas exchange measures after disease recovery among adult patients in Iceland who tested positive for SARS-CoV-2 from February 2020 to April 2021.

All COVID-19 survivors with an oxygen saturation level of at least 94% who were discharged to independent living were offered a clinical follow-up visit focused on respiratory care. During the follow-up, the participants underwent the 6-minute walk test (6MWT), spirometry and diffusion capacity of carbon monoxide (DLCO) measurement, and a computed tomography (CT) scan of the chest without an intravenous contrast agent.

The analysis included 164 patients who were categorized by treatment level they had required when infected with COVID-19: 32 had never been admitted to hospital; 103 were admitted to hospital but not the ICU; and 29 had been in the ICU. Their mean age was 60 years, and 45% were female. Most were admitted to a general hospital ward (63%), 18% were admitted to an ICU, and about 20% required ambulatory follow-up only. A majority of participants (74%) had an imaging abnormality at follow-up (CT score of >0), with a median score of 5 (interquartile range [IQR], 0-10).

Participants in the 3 different treatment level groups showed significant differences in the percentage of predicted distance on 6MWT (P = .0003), the FVC percentage (P = .016), FEV1/FVC ratio (P = .01), the DLCO percentage of predicted (P = 5×10−6), and oxygen saturation after the 6MWT (P = .003), but not for the percentage of predicted FEV1 (P = .53).

Respiratory-focused follow-up for survivors COVID-19 pneumonia should be aimed at survivors of the most severe illness and those with extensive long-term radiologic changes.

Investigators also performed regression analyses to determine the association between treatment levels and pulmonary outcomes. The researchers found that patients receiving ICU treatment had shorter 6MWT distance (β = −14% of predicted, P =.0001) and lower DLCO (β = −20% of predicted, P <.0001) than patients receiving ambulatory care. Intensive care treatment also was associated with decreased oxygen saturation after 6MWT (β = −2.1% of predicted, P =.004).

In regression analyses of associations between CT severity scores at follow-up (with a higher severity score indicating greater anatomic involvement from disease) and pulmonary outcomes, the researchers found that higher follow-up CT scores were associated with decreased distance in the 6MWT (β per point in CT score = −0.82% of predicted, P <.0001), FVC decrease (β = −0.46% of predicted, P =.02), an increase in FEV1/FVC ratio (β = 0.26%, P =.04), a decrease in DLCO (β = −1.1% of predicted, P <.0001), and decreased oxygen saturation after 6MWT (β = −0.11%, P =.004), regardless of modeling method. CT scores were not associated with dyspnea, which was measured using the modified Medical Research Council (mMRC) scale.

Study limitations include: (1) some associations, including those of mMRC score with treatment levels and FEV1/FVC with imaging changes, barely met the threshold for statistical significance; (2) possible residual confounding; (3) respiratory symptoms were estimated with the mMRC scale; (4) some changes may have resulted from reverse causation; and (5) some data were obtained from unvaccinated participants before the emergence of viral variants.

“Respiratory-focused follow-up for survivors COVID-19 pneumonia should be aimed at survivors of the most severe illness and those with extensive long-term radiologic changes,” the researchers concluded.

This article originally appeared on Pulmonology Advisor


Axelsson GT, Halldorsson AB, Jonsson HM, et al. Respiratory function and CT abnormalities among survivors of COVID-19 pneumonia: a nationwide follow-up study. BMJ Open Respir Res. 2022;9(1):e001347. doi: 10.1136/bmjresp-2022-001347