The measurement of exhaled gas nitric oxide (FeNO) has safe, non-invasive, simple, repetitive characteristics which is widely used in the assessment of airway inflammation in asthmatic patients, but the determination of FeNO is affected by a variety of factors, among which living environment factors exposure may have a close relationship to FeNO level, whereas there are few studies on the impact of exposure of living environment factors on the level of FeNO.

To analyze the effect of exposure to living environment factors on the level of exhaled nitric oxide (FeNO) in patients with bronchial asthma in non acute attack period, so as to improve the efficacy of clinicians in using FeNO to manage asthma.

A total of 109 patients with bronchial asthma in non acute attack period who visited the Respiratory Department Outpatient of the Second Affiliated Hospital of Guangzhou Medical University from July 2018 to June 2020 were included as the study subjects, the data were collected through a questionnaire survey, and the questionnaire information mainly included general information (gender, age, height, body mass) , living environment factors (including smoking history, whether family members smoked at home, allergy history, location of residence, the distance between the residence and the main road with large traffic volume, whether there were factories around the residence, floors of residential buildings, length of residence building, frequency of washing and drying bed sheets, quilt covers/pillow cases, curtain materials at home, potted plants at home, whether the trash can in the home was cleaned regularly, whether kept pets at home, whether there were cockroaches at home and whether kitchen waste was disposed of the same day, whether there were plush toys at home) and the inspection data of FeNO collected. Patients with bronchial asthma were divided into 3 groups according to FeNO level: there were 47 cases in the FeNO low level group (FeNO<25 ppb) , 35 cases in the FeNO medium level group (25 ppb≤FeNO≤50 ppb) and 27 cases in the FeNO high level group (FeNO>50 ppb) . Ordinal multiple classification logistic regression analysis was used to explore the environmental factors affecting the FeNO value level measurement.

There was no significant difference in gender, age, height and body mass among the three groups (P>0.05) . There was no significant difference among the three groups in floors of residential buildings, length of residence, frequency of washing and drying bed sheets, quilt covers/pillow cases, curtain materials at home, potted plants at home, whether the trash can in the home was cleaned regularly, whether there were cockroaches at home and whether kitchen waste was disposed of the same day, whether there were plush toys at home (P>0.05) ; There were statistically significant differences in smoking history, whether family members smoked at home, allergy history, location of residence, the distance between the residence and the main road with large traffic volume, whether there were factories around the residence, and whether there were pets at home (P<0.05) . Those with a history of smoking were 0.332 (P=0.022) times more likely to have one grade higher FeNO levels compared to those without; Family member smoking at home was 0.345 (P=0.014) times more likely to have one grade higher FeNO level compared to those not smoking at home; Compared with those without pets at home, those who kept pets at home were 0.327 (P=0.014) times more likely to have one grade higher FeNO level; Those with a history of allergy were 4.076 (P=0.003) times more likely to have one grade higher FeNO levels compared to those without; Those whose place of residence was the center of the city were 3. 908 (P = 0.006) times more likely to have one grade higher FeNO level compared with those whose place of residence was suburban; The probability of having one grade higher FeNO level were 2.689 (P=0.018) times higher in those whose place of residence was near the main tract versus those whose place of residence was far from the main tract; Those with a factory around their place of residence were 2.740 (P=0.032) times more likely to have one grade higher FeNO level compared with those without a factory around their place of residence.

The determination of FeNO value level used in daily management of asthma is obviously affected by exposure factors of living environment, especially tobacco exposure, allergies, keeping pets and place of residence, and needs to be differentiated clinically for relevant patients.