Key result
The VE/VCO2 intercept was significantly correlated with worsening static and dynamic lung hyperinflation and airflow limitation in COPD, emerging as a useful index of ventilatory inefficiency.
Why the study?
Relationships between the minute ventilation vs. carbon dioxide output intercept, lung hyperinflation, and airflow limitation in COPD were unknown.
Does the V̇E/V̇CO2 intercept correlate with lung hyperinflation and airflow limitation in patients with COPD?
Observational (n=67)
No
Does the V̇E/V̇CO2 intercept correlate with lung hyperinflation and airflow limitation in patients with COPD?
Effect estimate: r=0.588
p-value: p=<0.001
The V̇E/V̇CO2 intercept is a useful index of ventilatory inefficiency that correlates well with worsening static and dynamic lung hyperinflation and airflow limitation across the severity spectrum of COPD.
May support VE/VCO2 intercept as marker of ventilatory inefficiency in COPD; hypothesis-generating and requires prospective validation before clinical adoption.
Abstract Background: Ventilatory inefficiency is known to be a contributor to exercise intolerance in chronic obstructive pulmonary disease (COPD). The intercept of the minute ventilation (V̇E) vs. carbon dioxide output (V̇CO₂) plot is a key ventilator inefficiency parameter. However, its relationships with lung hyperinflation (LH) and airflow limitation are not known. This study aimed to evaluate the correlations between the V̇E/V̇CO₂ intercept and LH in COPD to determine its utility as an index of functional impairment.Methods: We conducted a retrospective analysis of data from 53 COPD patients and 14 healthy controls performed incremental cardiopulmonary exercise tests and resting pulmonary function. Ventilatory inefficiency was represented by parameters reflecting the V̇E/V̇CO₂ nadir and slope (linear region), and intercept of the V̇E/V̇CO₂ plot. Their correlations with measures of LH and airflow limitation were evaluated.Results: Compared to the control, the slope (30.58±3.62) and intercept (4.85±1.11) higher in COPDstages1-2, leading to a higher nadir (31.47±4.47) (p<0.05). Despite an even higher intercept in COPDstages3-4 (7.16±1.41), the slope diminished with disease progression (from 30.58±3.62 in COPDstages1-2 to 28.36±4.58 in COPDstages3-4). Compared to the V̇E/V̇CO₂ nadir and V̇E/V̇CO₂ slope, the intercept was better correlated with peak V̇E/maximal voluntary ventilation (MVV) (r=0.489, p<0.001) and peak V̇O₂/watt (r=0.354, p=0.003). The intercept was also significantly correlated with RV/TLC (r=0.588, p<0.001), IC/TLC (r=-0.574, p<0.001), peak VT/TLC (r=-0.585, p<0.001); and airflow limitation forced expiratory volume in 1s (FEV₁) % predicted (r=-0.606, p<0.001) and FEV₁/forced vital capacity (FVC) (r=-0.629, p<0.001).Conclusion: V̇E/V̇CO₂intercept was consistently better correlated with worsening static and dynamic lung hyperinflation and airflow limitation in COPD. V̇E/V̇CO₂ intercept emerged as a useful index of ventilatory inefficiency across the severity spectrum of COPD patients.
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Wang et al. (2020) conducted an observational in Chronic obstructive pulmonary disease (n=67). Chronic obstructive pulmonary disease vs. Healthy controls was evaluated on Correlation between VE/VCO2 intercept and static lung hyperinflation (RV/TLC) (r=0.588, p=<0.001). The VE/VCO2 intercept was significantly correlated with worsening static and dynamic lung hyperinflation and airflow limitation in COPD, emerging as a useful index of ventilatory inefficiency.
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