ORIGINAL RESEARCH article
Front. Physiol.
Sec. Respiratory Physiology and Pathophysiology
Interrogating Pulmonary Diffusing Capacity in Long COVID: Insights from DLCO and DLNO Testing
Provisionally accepted
Jordan Kimberly Parks1*
Bruce D Johnson2
Meredith Gail Shea1
Chul-Ho Kim2
Jessica I Johnston2Alex Carlson2Jesse Schwartz2
Courtney Wheatley-Guy1- 1Mayo Clinic Arizona, Scottsdale, United States
- 2Mayo Clinic Minnesota, Rochester, United States
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Abstract Introduction: The lingering respiratory effects of COVID-19, particularly in patients with Long COVID, remain poorly understood, prompting a comprehensive evaluation of lung function in this population. Methods: Simultaneous measurements of diffusion capacity of the lungs for carbon monoxide (DLCO) and nitric oxide (DLNO), chest computed tomography (CT), lung ultrasound and questionnaires were collected in 74 subjects. Participants were categorized into two groups: those that have no lingering symptoms (NS, n=37) and those still struggling with symptoms after initial infection, the disease known as Long COVID (LC, n=37). Results: DLCO and DLNO were significantly lower in the LC group compared to the NS group (LC vs. NS, DLCO: 25.94±7.65 vs. 21.71±6.35 ml/min/mmHg, p=0.009; DLNO: 148.5±35.6 vs. 126.6±32.2 ml/min/mmHg, p=0.006). Pulmonary capillary blood volume (Vc) was also significantly lower in the LC group (43.38±13.87, 70.79±17.77, p=0.003; LC vs. NS, respectively). Alveolar volume (VA) is significantly lower in the LC group (LC vs. NS, 5.06±1.17 v. 5.95±1.16, p=0.004). There was no significant difference between groups for surface area of the lungs available for gas exchange by resistance to gas transfer across the alveolar-capillary membrane (DM) between groups (LC vs. NS, 208.63±97.3, 223.0±93.47 ml/min/mmHg, p=0.54). These findings indicate that Vc is the driving factor of decreased DLCO. CT findings and lung ultrasound showed no differences between the two groups for lung fluid (p=0.525; p=0.298). Conclusion: These findings suggest that a lack of volume available for perfusion could be problematic for these patients and as such requires further investigation for clinical management of these patients.
Keywords: Long Covid, COVID, Diffusion capacities for CO and NO, Alveolar volume, Membrane conductance
Received: 14 Oct 2025; Accepted: 10 Nov 2025.
Copyright: © 2025 Parks, Johnson, Shea, Kim, Johnston, Carlson, Schwartz and Wheatley-Guy. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Jordan Kimberly Parks, parks.jordan@mayo.edu
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