Figure 2.

EBC Ado was successfully measured in 36 healthy NS subjects (NS group), 28 healthy S subjects (S group), and 89 subjects with COPD (29 GOLD II, 29 GOLD III, 31 GOLD IV) and reported as ratios of Ado (nM) to urea (μM) to control for variable dilution of airway secretions. A, Ado to urea ratios differed among the cohorts and were elevated in subjects with COPD relative to NS. B, EBC Phe was measured from EBC from 26 NS group subjects, 29 S group subjects, and 78 subjects with COPD; the Phe to urea ratio (μM Phe to μM urea) was similar among all cohorts. C, Analysis of Ado to urea ratio with subjects with COPD divided by GOLD stage; cohorts differed by analysis of variance (ANOVA) with Ado to urea ratio elevated in GOLD III and GOLD IV subjects relative to NS group subjects. D, A modest correlation (r = −0.27, P = .002) was noted between EBC Ado to urea ratio and FEV₁ % predicted. *P < .05 by ANOVA, †P < .05 vs NS by linear contrast with Tukey-Kramer adjustment. Ado = adenosine; GOLD = Global Initiative for Chronic Obstructive Lung Disease; NS = nonsmoker; Phe = phenylalanine; S = smoker. See Figure 1 legend for expansion of other abbreviation.