The key COVID-19 findings in pulmonology, distilled into a clear, readable brief. The evidence is here whenever you want to go deeper.
INSIDE THIS MONITOR
33cited sources
10available findings
Study findings updated
AI-assisted evidence summary. For general information. These findings are not individual medical advice or a clinician endorsement.
THE SHORT VERSION
What’s worth knowing.
The key findings, what they mean, and the context that matters.
THE HEADLINE TAKEAWAY>90%
Most measured lung-function values were normal despite breathlessness
With breathless Long COVID, >90% of measured lung-function values were normal despite lower scores than controls. In a never-hospitalized subgroup, 14/109 (~13%) had a low lung gas-transfer measure (TLCO) and reduced xenon-MRI gas-exchange metrics.
The >90% describes measured values, not people; details of the controls are not available in this summary. The subgroup had otherwise unexplained breathlessness, and a pulmonary contribution was described as only potential.
See the evidence
Although breathless long-COVID participants had lower FEV1, FVC, TLCO, and KCO z-scores than controls, more than 90% of the measured values remained within the normal range.
>90%
Ng, Kher Lik et al.. Using hyperpolarised xenon magnetic resonance imaging to explore breathlessness in long COVID: results from the EXPLAIN study.. ERJ open research. 2026.
Among never-hospitalised long-COVID participants with otherwise unexplained breathlessness, approximately 13% had low TLCO and showed reduced xenon-MRI gas-exchange metrics and higher breathlessness scores, suggesting only a potential pulmonary contribution in this subgroup.
14/109 (~13%)
Ng, Kher Lik et al.. Using hyperpolarised xenon magnetic resonance imaging to explore breathlessness in long COVID: results from the EXPLAIN study.. ERJ open research. 2026.
Lung gas-transfer problems persisted at 3-year follow-up
36.6%
At 3-year follow-up, 36.6% of hospitalized COVID-19 convalescents had a persistent problem with lung gas transfer.
This prospective cohort was limited to hospitalized convalescents. No comparison group is identified in this summary, so it does not show how the frequency differs in other populations.
See the evidence
Persistent pulmonary diffusion dysfunction at 3-year follow-up among hospitalized COVID-19 convalescents
36.6%
Zhang, Zhijin et al.. Longitudinal profiling of upper respiratory tract microbiota and metabolome in hospitalized COVID-19 convalescents: a 3-year prospective cohort study.. Journal of translational medicine. 2026.
Several abnormalities remained in COVID-19 hospital survivors
At 12 months, the cohort reported impaired lung gas transfer, reduced distance on a six-minute walk test and fibrotic lung changes among hospitalized COVID-19 survivors.
The longitudinal cohort assessed 1-year outcomes in hospitalized survivors; the summary does not identify the basis of its percentage ranges.
See the evidence
Persistent DLCO Impairment at 12 Months
24-38%
Huang L, Yao Q, Gu X, et al. 1-year outcomes in hospital survivors with COVID-19: a longitudinal cohort study. Lancet. 2021;398(10302):747-758.
Clinic respiratory symptoms were frequent; lung function was generally preserved
At the first follow-up, 760/963 (79%) post-COVID clinic participants reported respiratory symptoms. Overall lung function was generally preserved, though a lung gas-transfer measure (DLCO) was lower in participants with respiratory symptoms than in those without.
Participants were followed up to 18 months. Symptoms at the first follow-up were associated with later symptom-group membership, but the odds ratio's reference group is not identified in this summary. Clinic recruitment limits prevalence generalization.
See the evidence
Prevalence of self-reported respiratory symptoms at the first follow-up among included participants recruited through a post-COVID clinic
760/963 (79%)
Hallberg, Carl et al.. Respiratory symptoms up to 18 months after COVID-19 - a longitudinal observational study.. Respiratory research. 2026.
Clinic respiratory symptoms were frequent; lung function was generally preserved
At the first follow-up, 760/963 (79%) post-COVID clinic participants reported respiratory symptoms. Overall lung function was generally preserved, though a lung gas-transfer measure (DLCO) was lower in participants with respiratory symptoms than in those without.
Participants were followed up to 18 months. Symptoms at the first follow-up were associated with later symptom-group membership, but the odds ratio's reference group is not identified in this summary. Clinic recruitment limits prevalence generalization.
Study details & original results
Hallberg, Carl et al.. Respiratory symptoms up to 18 months after COVID-19 - a longitudinal observational study.. Respiratory research. 2026.
Prevalence of self-reported respiratory symptoms at the first follow-up among included participants recruited through a post-COVID clinic
760/963 (79%)
DLCO in participants with versus without respiratory symptoms; overall lung function was generally preserved
DLCO 79% vs 84%; adjusted p < 0.05
Association between respiratory symptoms at the first follow-up and belonging to the respiratory symptom group at the second follow-up
Most measured lung-function values were normal despite breathlessness
>90%
With breathless Long COVID, >90% of measured lung-function values were normal despite lower scores than controls. In a never-hospitalized subgroup, 14/109 (~13%) had a low lung gas-transfer measure (TLCO) and reduced xenon-MRI gas-exchange metrics.
The >90% describes measured values, not people; details of the controls are not available in this summary. The subgroup had otherwise unexplained breathlessness, and a pulmonary contribution was described as only potential.
Study details & original results
Ng, Kher Lik et al.. Using hyperpolarised xenon magnetic resonance imaging to explore breathlessness in long COVID: results from the EXPLAIN study.. ERJ open research. 2026.
Although breathless long-COVID participants had lower FEV1, FVC, TLCO, and KCO z-scores than controls, more than 90% of the measured values remained within the normal range.
>90%
Among never-hospitalised long-COVID participants with otherwise unexplained breathlessness, approximately 13% had low TLCO and showed reduced xenon-MRI gas-exchange metrics and higher breathlessness scores, suggesting only a potential pulmonary contribution in this subgroup.
Lung gas-transfer problems persisted at 3-year follow-up
36.6%
At 3-year follow-up, 36.6% of hospitalized COVID-19 convalescents had a persistent problem with lung gas transfer.
This prospective cohort was limited to hospitalized convalescents. No comparison group is identified in this summary, so it does not show how the frequency differs in other populations.
Study details & original results
Zhang, Zhijin et al.. Longitudinal profiling of upper respiratory tract microbiota and metabolome in hospitalized COVID-19 convalescents: a 3-year prospective cohort study.. Journal of translational medicine. 2026.
Persistent pulmonary diffusion dysfunction at 3-year follow-up among hospitalized COVID-19 convalescents
Ng, Kher Lik et al.. Using hyperpolarised xenon magnetic resonance imaging to explore breathlessness in long COVID: results from the EXPLAIN study.. ERJ open research. 2026.
Among never-hospitalised long-COVID participants with otherwise unexplained breathlessness, approximately 13% had low TLCO and showed reduced xenon-MRI gas-exchange metrics and higher breathlessness scores, suggesting only a potential pulmonary contribution in this subgroup.
Although breathless long-COVID participants had lower FEV1, FVC, TLCO, and KCO z-scores than controls, more than 90% of the measured values remained within the normal range.
Zhang, Zhijin et al.. Longitudinal profiling of upper respiratory tract microbiota and metabolome in hospitalized COVID-19 convalescents: a 3-year prospective cohort study.. Journal of translational medicine. 2026.
PHOSP-COVID Collaborative Group. Clinical characteristics with inflammation profiling of long COVID and association with 1-year recovery following hospitalisation in the UK: a prospective observational study. Lancet Respiratory Medicine. 2022;10(8):761-775.
Browse the 33 original sourcesThe complete bibliography behind this monitor.
[1]
Torres-Castro R, Vasconcello-Castillo L, Alsina-Restoy X, et al. Respiratory function in patients post-infection by COVID-19: a systematic review and meta-analysis. Pulmonology. 2021;27(4):328-337.
Suh YJ, Hong H, Ohana M, et al. Pulmonary embolism and deep vein thrombosis in COVID-19: A systematic review and meta-analysis. Radiology. 2021;298(2):E70-E80.
Jenner WJ, Gober IM, Engleton E, et al. Pulmonary embolism and COVID-19: Meta-analysis of risk assessment tools. European Respiratory Journal. 2021;58(2):2100169.
Fernandez-de-las-Penas C, Palacios-Cena D, Gomez-Mayordomo V, et al. Prevalence of post-COVID-19 symptoms in hospitalized and non-hospitalized COVID-19 survivors: A systematic review and meta-analysis. European Journal of Internal Medicine. 2021;92:55-70.
Fabbri L, Moss S, Khan FA, et al. Parenchymal lung abnormalities following hospitalisation for COVID-19 and viral pneumonitis: a systematic review and meta-analysis. Thorax. 2023;78(2):191-201.
Huang C, Huang L, Wang Y, et al. 6-month consequences of COVID-19 in patients discharged from hospital: a cohort study. Lancet. 2021;397(10270):220-232.
Wu X, Liu X, Zhou Y, et al. 3-month, 6-month, 9-month, and 12-month respiratory outcomes in patients following COVID-19-related hospitalisation: a prospective study. Lancet Respiratory Medicine. 2021;9(7):747-754.
Evans RA, McAuley H, Harrison EM, et al. Physical, cognitive, and mental health impacts of COVID-19 after hospitalisation (PHOSP-COVID): a UK multicentre, prospective cohort study. Lancet Respiratory Medicine. 2021;9(11):1275-1287.
PHOSP-COVID Collaborative Group. Clinical characteristics with inflammation profiling of long COVID and association with 1-year recovery following hospitalisation in the UK: a prospective observational study. Lancet Respiratory Medicine. 2022;10(8):761-775.
Shah AS, Wong AW, Hague CJ, et al. A prospective study of 12-week respiratory outcomes in COVID-19-related hospitalisations. Thorax. 2021;76(4):402-404.
Guler SA, Ebner L, Aubry-Beigelman C, et al. Pulmonary function and radiological features 4 months after COVID-19: first results from the national prospective observational Swiss COVID-19 lung study. European Respiratory Journal. 2021;57(4):2003690.
Vijayakumar B, Tonkin J, Engelen A, et al. CT lung abnormalities after COVID-19 at 3 months and 1 year after hospital discharge. Radiology. 2022;303(2):444-454.
Shi H, Han X, Jiang N, et al. Radiological findings from 81 patients with COVID-19 pneumonia in Wuhan, China: a descriptive study. Lancet Infectious Diseases. 2020;20(4):425-434.
Ackermann M, Verleden SE, Kuehnel M, et al. Pulmonary vascular endothelialitis, thrombosis, and angiogenesis in Covid-19. New England Journal of Medicine. 2020;383(2):120-128.
George PM, Wells AU, Jenkins RG. Pulmonary fibrosis and COVID-19: the potential role for antifibrotic therapy. Lancet Respiratory Medicine. 2020;8(8):807-815.
Helms J, Tacquard C, Severac F, et al. High risk of thrombosis in patients with severe SARS-CoV-2 infection: a multicenter prospective cohort study. Intensive Care Medicine. 2020;46(6):1089-1098.
Singh I, Joseph P, Heerdt PM, et al. Persistent exertional intolerance after COVID-19: Insights from invasive cardiopulmonary exercise testing. Chest. 2022;161(1):54-63.
Townsend L, Dowds J, O'Brien K, et al. Persistent poor health after COVID-19 is not associated with respiratory complications or initial disease severity. Annals of the American Thoracic Society. 2021;18(6):997-1003.
Liu K, Zhang W, Yang Y, et al. Respiratory rehabilitation in elderly patients with COVID-19: A randomized controlled study. Complementary Therapies in Clinical Practice. 2020;39:101166.
ATTACC Investigators, ACTIV-4a Investigators, REMAP-CAP Investigators. Therapeutic anticoagulation with heparin in noncritically ill patients with Covid-19. New England Journal of Medicine. 2021;385(9):790-802.
British Thoracic Society. BTS Guidance on Respiratory Follow Up of Patients with a Clinico-Radiological Diagnosis of COVID-19 Pneumonia. Version 3.0. 2021.
Original source link unavailable
[27]
European Respiratory Society. ERS Statement on Long COVID Follow-up. European Respiratory Journal. 2022.
Burnham EL, Hyzy RC, Paine R, et al. Chest CT features are associated with poorer quality of life in acute lung injury survivors. Critical Care Medicine. 2013;41(2):445-456.
Hui DS, Wong KT, Ko FW, et al. The 1-year impact of severe acute respiratory syndrome on pulmonary function, exercise capacity, and quality of life in a cohort of survivors. Chest. 2005;128(4):2247-2261.
Zhang, Zhijin et al.. Longitudinal profiling of upper respiratory tract microbiota and metabolome in hospitalized COVID-19 convalescents: a 3-year prospective cohort study.. Journal of translational medicine. 2026.
Ng, Kher Lik et al.. Using hyperpolarised xenon magnetic resonance imaging to explore breathlessness in long COVID: results from the EXPLAIN study.. ERJ open research. 2026.
This is an AI-assisted evidence summary, not a clinician endorsement. Read each original paper for its complete methods, population and limitations. Different studies can ask different questions and report different kinds of results.
Dates marked “added” describe when a finding entered this monitor, not when the study was published or clinically reviewed. Personal health and treatment decisions belong in a conversation with a qualified clinician.