Key result
In patients with mild COPD, the RV/TLC ratio was the only significant predictor of resistance loop opening, with an odds ratio of 1.157.
Why the study?
Do non-linear parameters of specific resistance loops characterize and differentiate obstructive airways diseases in patients with asthma and COPD?
Cross-Sectional (n=134)
No
Do non-linear parameters of specific resistance loops characterize and differentiate obstructive airways diseases in patients with asthma and COPD?
Odds Ratio: 1.157 (95% CI 1.064–1.267)
p-value: p=0.0006
New non-linear parameters of specific resistance loops, such as roundness, can differentiate COPD from healthy and asthmatic subjects and correlate with hyperinflation.
Should not yet change resistance loop assessment in mild COPD; leaves open non-linear parameters for differentiating obstructive diseases.
Specific resistance loops appear in different shapes influenced by different resistive properties of the airways, yet their descriptive ability is compressed to a single parameter - its slope. We aimed to develop new parameters reflecting the various shapes of the loop and to explore their potential in the characterisation of obstructive airways diseases. Our study included 134 subjects: Healthy controls ( N = 22), Asthma with non-obstructive lung function ( N = 22) and COPD of all disease stages ( N = 90). Different shapes were described by geometrical and second-order transfer function parameters. Our parameters demonstrated no difference between asthma and healthy controls groups, but were significantly different ( p < 0.0001) from the patients with COPD. Grouping mild COPD subjects by an open or not-open shape of the resistance loop revealed significant differences of loop parameters and classical lung function parameters. Multiple logistic regression indicated RV/TLC as the only predictor of loop opening with OR = 1.157, 95% CI (1.064–1.267), p -value = 0.0006 and R 2 = 0.35. Inducing airway narrowing in asthma gave equal shape measures as in COPD non-openers, but with a decreased slope ( p < 0.0001). This study introduces new parameters calculated from the resistance loops which may correlate with different phenotypes of obstructive airways diseases.
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Topalovic et al. (2017) conducted a cross-sectional in Obstructive airways diseases (Asthma, COPD) (n=134). RV/TLC ratio was evaluated on Predictor of resistance loop opening in mild COPD (OR 1.157, 95% CI 1.064-1.267, p=0.0006). In patients with mild COPD, the RV/TLC ratio was the only significant predictor of resistance loop opening, with an odds ratio of 1.157.
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