Gelb, AF; George, SC; Fraser, C; Taylor, CF; Camacho, F
RATIONALE: There is a paucity of data evaluating changes in exhaled nitric oxide (FeNO) after correction for axial NO back diffusion in healthy, non-smoking subjects of varying age, and with normal spirometry.
METHODS: Exhaled NO was measured at 50, 100, 150, and 200 mL/s; and large airway NO flux (J`awNO,nL/s) and peripheral airway/alveolar NO (CANO,ppb) was calculated using a two-compartment model (Tsoukias NM, GeorgeSC. JAP1998;85:653-666) that corrected for axial NO back diffusion (Condorelli P et al. JAP2007;102:417-425).
RESULTS: In 54 normals (26M), age 52±21yr (mean±SD), FeNO at 50mL/s was 21(13-27)ppb (median, 1-3 interquartile), and Spearman correlation with age 14-80yr was 0.36,p=0.01. Corrected J`awNO was 1.5(0.8-2.0)nL/s and Spearman correlation with age 0.15, p=0.3. Corrected CANO was 1.9(0.7-4.3)ppb and Spearman correlation with age was 0.4, p=0.004, and with piece-wise linear fit r^2=0.23, p=0.001. Normal subjects were divided into 3 age groups: Y=younger, n=14, age 22±7yr (mean±SD); M=middle, n=17, age 51±13yr; and O=older, n=23, age 70±7yr. In Group Y, corrected CANO was 1.5±1.6ppb (mean±SD); in Group M, CANO 2.6±2.4ppb; and in Group O, CANO 3.5±2.9ppb and for difference between age groups, ANOVA on Ranks= 0.4. Logarithmic transformation of CANO versus age yielded r^2=0.12, p=0.01. In Group Y, FeNO was 15±8ppb; in Group M, FeNO was 20±11ppb; and in Group O, FeNO was 25±11ppb and for difference between age groups ANOVA= 0.03. In group Y, corrected J`awNO was 1.2±0.7nL/s; in Group M, J`awNO was 1.4±1.0nL/s; and in Group O, J`awNO was 1.7±0.9nL/s and for difference between age groups ANOVA= 0.1.
CONCLUSION: In non-smoking, healthy subjects with normal spirometry, FeNO at 50mL/s,ppb and corrected CANO,ppb correlate mildly with increasing age between 14 to 80yr, whereas corrected J`awNO,nL/s correlates poorly.
