Am J Med Public Health | Volume 5, Issue 1 | Research Article | Open Access

Persistent Reduction of Lung Capillary Blood Volume as the Major “Deep Lung” Disorder Underlying Respiratory Long-COVID Syndrome

Negro RD1*, Turco P1 and Povero M2

1National Centre for Respiratory Pharmacoeconomics and Pharmacoepidemiology - CESFAR, Italy
2AdRes Health Economics and Outcome Research, Italy

*Correspondance to: Roberto Dal Negro 

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Background: Long-COVID syndrome is the persistency of symptoms of the original SARS-CoV-2 infection. Dyspnea frequently lasts for several weeks/months (the Respiratory Long-COVID Syndrome). Impairment of lung alveolar and capillary structures are related to dyspnea duration. Aim: To compare subjects recovered from COVID Pneumonia (HOSP), subjects who only suffered Pauci-Symptomatic SARS-CoV-2 infection (PS), and Healthy Controls (HC) by lung function and dyspnea scores. Methods: mMRC scores, spirometric parameters, usual DLCO, and single-breath simultaneous NO (sDLNO) and CO (sDLCO) diffusion were assessed in: 40 HOSP subjects still complaining dyspnea 16 weeks after discharge (19 mMRC<1, 21 mMRC>1); 35 PS (five no-vax) complaining long-lasting dyspnea, and 28 HC. Comparison among groups was conducted by ANOVA test. Results: The sensitivity of spirometric parameters and usual DLCO was low in discriminating the groups (all p=ns). Only sDLNO and sDLCO, their ratio (sDLNO/sDLCO), and the volume of lung of capillary blood (Vc) discriminated the groups with high significancy (p<0.05 in almost all comparisons). PS and HOSP patients with low mMRC seem to be similar spirometric profiles (p>0.20). The five no-vax PS subjects showed higher microvascular impairment. Conclusion: The impairment of capillary lung volume proves the major pathogenetic sequela of SARS-CoV-2 inflammatory aggression underlying respiratory Long-COVID syndrome. Longlasting dyspnea acts as the predicting clinical sign in these cases. Only simultaneous measures of sDLNO/sDLCO ratio and Vc allow to detect and grading with high sensitivity/specificity the microvascular impairment otherwise undetectable in respiratory Long-COVID syndrome. The protecting role of vaccination should be focused also from this point of view.


Long-COVID syndrome; Lung function; Lung capillary blood volume; Dyspnea; Simultaneous single-breath DLCO and DLNO measurement; Lung diffusion


Negro RD, Turco P, Povero M. Persistent Reduction of Lung Capillary Blood Volume as the Major “Deep Lung” Disorder Underlying Respiratory Long-COVID Syndrome. Am J Med Public Health. 2024; 5(1): 1059..

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