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Published on: December 19, 2020
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Long-term alveolar-capillary diffusion impairments after severe SARS-CoV-2 pneumonia
Laura Pini1,2, Jordan Giordani1, Guido Levi1,3
1Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy.
Annals of Medicine
|March 28, 2025
Summary
Persistent COVID-19 lung issues are common. This study found vascular problems, not membrane damage, cause long-term impaired lung diffusing capacity for carbon monoxide (DLCO).
Area of Science:
- Pulmonology
- Respiratory Medicine
- Critical Care Medicine
Background:
- Persistent respiratory symptoms and impaired gas exchange are common sequelae in patients recovering from COVID-19 pneumonia.
- Standard lung function tests like DLCO and KCO cannot reliably differentiate between alveolar membrane dysfunction and vascular abnormalities.
- Characterizing persistent diffusion impairment in post-ICU patients with prior SARS-CoV-2 pneumonia and reduced DLCO is crucial for understanding long-term respiratory sequelae.
Purpose of the Study:
- To characterize persistent diffusion impairment in post-intensive care unit (ICU) patients following COVID-19 pneumonia.
- To differentiate between alveolar-capillary membrane (DmCO) and pulmonary capillary blood volume (Vc) alterations contributing to reduced DLCO.
- To investigate the underlying mechanisms of persistent diffusion impairment using a combined DLNO and DLCO assessment.
Main Methods:
- Patients with prior SARS-CoV-2 pneumonia and reduced DLCO underwent serial spirometry and 6-minute walking tests post-hospital discharge.
- A combined Lung Diffusing Capacity for Nitric Oxide (DLNO) and DLCO assessment was performed at 18-24 months if DLCO remained impaired.
- This assessment aimed to differentiate alterations in alveolar-capillary membrane (DmCO) and pulmonary capillary blood volume (Vc).
Main Results:
- Among 20 patients with persistent DLCO reduction, 3 had obstructive, 6 had restrictive ventilatory patterns, and 12 had low KCO.
- The DLNO/DLCO ratio exceeded 113.5% predicted in all patients, indicating a specific pattern of diffusion impairment.
- Pulmonary capillary blood volume (Vc) was reduced in 16 patients, while the alveolar-capillary membrane (DmCO) was impaired in 7.
Conclusions:
- Persistent DLCO reduction in post-COVID-19 patients is predominantly driven by pulmonary vascular dysfunction (Vc reduction).
- Alveolar membrane (DmCO) alterations are less prominent, with Vc reduction being the primary contributor to long-term diffusion impairment.
- The elevated DLNO/DLCO ratio highlights the significant vascular component in persistent post-COVID-19 respiratory sequelae.
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