Acinar effect of inhaled steroids evidenced by exhaled nitric oxide.

BACKGROUND: The effects of inhaled corticosteroids (ICSs) on distal lung inflammation, as assessed by alveolar nitric oxide concentration (C(A)NO), are a matter of debate. Recently, a theoretic study suggested that acinar airway obstruction that is relieved by ICS treatment and associated with a decrease in fraction of exhaled nitric oxide (FeNO) concentration might, paradoxically, increase C(A)NO. This increase could be a hallmark effect of ICSs at the acinar level.

OBJECTIVE: In the light of this new hypothesis, we studied changes in C(A)NO and FeNO after administration of ICSs.

METHODS: C(A)NO and FeNO were measured before and after ICS treatment of 38 steroid-naive patients with uncontrolled asthma who showed clinical improvement after ICS therapy.

RESULTS: The average FeNO decreased from 78.3 to 28.9 ppb (P < .001); C(A)NO decreased from 7.7 to 4.3 ppb (P = .009). In 14 subjects (low-slope group), slope (= ΔC(A)NO/ΔFeNO) values (Δ = post-ICS - pre-ICS value) were less than the 95% normal CI (average ΔFeNO = -32.7 ppb and average ΔC(A)NO= +2.9 ppb). In this group, baseline C(A)NO was abnormally low when FeNO was taken into account. In 11 subjects (the high-slope group), the slope was above the normal interval (average ΔFeNO = -42.5 ppb and average ΔC(A)NO = -14.7 ppb).

CONCLUSION: Opposite patterns (one that was predicted) can indicate peripheral actions of ICSs; this difference might account for conflicting data reported from studies using C(A)NO to determine the peripheral action of ICSs. We show that a low C(A)NO does not preclude distal inflammation.