Study objectives: It has been demonstrated previously
that exhaled nitric oxide (eNO) is increased in steroid-naive
asthmatics and that inhaled steroids reduce eNO in these patients.
Cigarette smoking has also been reported to reduce the eNO in healthy
volunteers. Recently a correlation has been demonstrated between eNO
and airway hyperresponsiveness in steroid-naive, mild asthmatics. We
hypothesized that cigarette smoking would reduce the eNO level in
steroid-naive asthmatics and might, therefore, affect the correlation
between eNO and airway hyperresponsiveness.
Comparison of eNO in healthy smoking and nonsmoking volunteers with the
level of eNO in steroid-naive and steroid-treated asthmatics. Correlate
the eNO level with the provocative concentration of histamine
causing a 20% fall in FEV1 (PC20hist) in the
asthmatic smoking and nonsmoking patients.
University outpatient asthma clinic.
methods: eNO levels and PC20hist were measured in
three different asthmatic patient groups (group A = 29 steroid-naive,
nonsmoking asthmatics; group B = 19 steroid-treated, nonsmoking
asthmatics; and group C = 13 smoking, steroid-naive asthmatics) and
in two healthy volunteer groups (group D = 18 nonsmoking; and group
E = 16 smoking).
Results: eNO in group A was
significantly increased compared with the values in groups B and D
(21.8 ± 12.7, 12.8 ± 4.9, and 10.6 ± 2.2 parts per billion[
ppb], respectively). Cigarette smoking decreased eNO in healthy
volunteers (7.4 ± 1.8 ppb, group E) as well as in steroid-naive
asthmatics (12.7 ± 5.1 ppb, group C). There was a significant
correlation between eNO and PC20hist in group A
(r = −0.45, p < 0.05); this correlation was, however, lost in
both groups B and C.
Conclusion: Cigarette smoking and
inhaled steroids reduce the eNO in patients with mild asthma to a
comparable extent. Because the correlation between eNO and airway
hyperresponsiveness was lost in steroid-treated and smoking,
steroid-naive asthmatics, we question the value of eNO as a marker of
airway inflammation, at least in mild asthmatics who are already being
treated with inhaled steroids or who are currently