Defining a phenotype of severe COPD patients who develop chronic hypercapnia

Renzo Boersma; Jens T Bakker; Maaike de Vries; Tim Raveling; Dirk-Jan Slebos; Peter J Wijkstra; Jorine E Hartman; Marieke L Duiverman

doi:10.1016/j.rmed.2024.107850

Defining a phenotype of severe COPD patients who develop chronic hypercapnia

Respir Med. 2024 Nov-Dec:234:107850. doi: 10.1016/j.rmed.2024.107850. Epub 2024 Oct 31.

Authors

Renzo Boersma¹, Jens T Bakker², Maaike de Vries³, Tim Raveling², Dirk-Jan Slebos², Peter J Wijkstra², Jorine E Hartman², Marieke L Duiverman²

Affiliations

¹ University of Groningen, University Medical Center Groningen, Department of Pulmonary Diseases, Groningen, the Netherlands; University of Groningen, University Medical Center Groningen, Groningen Research Institute for Asthma and COPD (GRIAC), Groningen, the Netherlands. Electronic address: r.boersma@umcg.nl.
² University of Groningen, University Medical Center Groningen, Department of Pulmonary Diseases, Groningen, the Netherlands; University of Groningen, University Medical Center Groningen, Groningen Research Institute for Asthma and COPD (GRIAC), Groningen, the Netherlands.
³ University of Groningen, University Medical Center Groningen, Groningen Research Institute for Asthma and COPD (GRIAC), Groningen, the Netherlands; University of Groningen, University Medical Center Groningen, Department of Epidemiology, Groningen, the Netherlands.

PMID: 39488255
DOI: 10.1016/j.rmed.2024.107850

Abstract

Introduction: Chronic hypercapnia, defined by elevated blood CO₂ levels, is a serious complication most prevalent in severe COPD. It negatively impacts quality of life, increases hospitalization rates, and elevates mortality risks. However, not all severe COPD patients develop chronic hypercapnia, and its underlying mechanisms remain unclear. Identifying clinical and pathophysiological predictors of hypercapnia is essential for tailored treatment strategies. This study investigates the relationship between hypercapnia and patient characteristics, lung function, and CT scan features to identify potential therapeutic targets.

Methods: This cross-sectional study included 1526 COPD patients from three cohorts: a standard care cohort and two research cohorts (NCT04023409; NCT03053973). Data collected included demographic and clinical information, blood gases, lung function (FEV₁, FVC, TLC, RV, DLCOc), and high-resolution CT scans (lung volumes, air trapping, emphysema scores, airway wall thickness (Pi10), and diaphragm indices).

Results: Hypercapnia prevalence increased with COPD severity. Hypercapnic patients were older, more likely to smoke, and had more comorbidities. They exhibited lower FEV₁ and FVC, and higher RV/TLC ratios, with CT scans showing lower emphysema scores and greater Pi10. Multivariate analysis identified lower PaO₂, FEV₁% predicted, and emphysema scores, along with higher RV/TLC ratios and NT-proBNP levels, as independent predictors of PaCO₂, collectively explaining 46.3 % of the variance.

Conclusion: COPD patients with chronic hypercapnia are characterized by higher smoking rates, lower PaO₂ levels, poorer lung function, less emphysema, and increased airway pathology. These findings underscore the multifactorial nature of hypercapnia in COPD, highlighting the need for personalized therapeutic strategies targeting these factors to improve outcomes.

Keywords: COPD; Computed tomography; Emphysema; Hypercapnia; Lung function.

MeSH terms

Aged
Chronic Disease
Cohort Studies
Cross-Sectional Studies
Female
Forced Expiratory Volume
Humans
Hypercapnia* / etiology
Hypercapnia* / physiopathology
Lung / diagnostic imaging
Lung / physiopathology
Male
Middle Aged
Phenotype*
Prevalence
Pulmonary Disease, Chronic Obstructive* / complications
Pulmonary Disease, Chronic Obstructive* / diagnostic imaging
Pulmonary Disease, Chronic Obstructive* / physiopathology
Respiratory Function Tests
Severity of Illness Index*
Smoking / adverse effects
Smoking / epidemiology
Tomography, X-Ray Computed