Effects and significance of methacholine bronchial provocation tests and salbutamol bronchial dilation test on measurements of fractional exhaled nitric oxide in patients with asthma

Abstract

To study the effects and significance of methacholine (Mch) bronchial provocation tests and salbutamol bronchial dilation test on measurements of fractional exhaled nitric oxide (FeNO) in patients with asthma. This was a prospective study conducted between November 2014 and August 2015. A total of 135 patients with asthma visiting the respiratory clinic of Zhujiang Hospital were enrolled. The patients received either Mch bronchial provocation test or salbutamol bronchial dilation test based on their FEV1/FVC values and cooperative degree. Mch bronchial provocation test was performed by using Astograph Jupiter-21 (Astograh group) or APS-Pro airway reaction testing apparatus (APS group), and salbutamol bronchial dilation test was performed by using Jaeger spirometer (Dilation group). We compared the differences between FeNO values measured before examinations (Pre-FeNO) and 5 min after completion of these examinations (Post-FeNO). The geometric mean of Pre-FeNO and Post-FeNO was 28.07 ppb and 24.08 ppb respectively in the Astograh group, with a significant decrease of the FeNO value after the examination (Z=-3.093, P=0.002). A significant difference between Pre-FeNO and Post-FeNO was found in patients who had positive provocation results in the Astograh group (Z=-2.787, P=0.005), but not in the patients with negative results (Z=-1.355, P=0.176). The geometric mean of FeNO in the APS group decreased significantly from 27.95 ppb to 23.15 ppb after the examination was completed (Z=-5.170, P=0.000); both in patients with positive saline or Mch provocation results and in patients with negative provocation results, the differences between Pre-FeNO and Post-FeNO in the APS group being significant (Z=-2.705, -3.709, -2.371, P=0.002, 0.000, 0.018). No difference of FeNO change(ΔFeNO) was observed between the 2 Mch bronchial provocation test groups (U<918.000, P=0.117). The geometric mean of Pre-FeNO was 36.74 ppb and that of Post-FeNO was 34.79 ppb in the Dilation group; the difference being not significant (Z=-1.281, P=0.200). Our results confirm that salbutamol bronchial dilation test has minor effect on the measurement of FeNO, but Mch bronchial provocation tests can significantly decrease measured FeNO value in patients with asthma, and therefore Post-FeNO values should be interpreted with caution.