Small Airway Function And Its Related Influence Factors In Controlled Asthmatic Children

BackgroundBronchial asthma is the most common chronic respiratory disease in childhood.According to the three epidemiological survey by National Children Asthma Group shows that the prevalence of asthma in children increased year by year,which seriously affect the physical and mental health of children.Lung function testing is an important method to diagnose and evaluate the severity of asthma and control level.Forced expiratory lung function is the most widely used method of lung function testing.Clinical practice found that there was a certain degree of small airway dysfunction in no clinical symptom asthmatics with normal FEV1 and FEV1/FVC.Prospective studies have shown that small airway dysfunction were associated with acute asthma attacks,increased airway responsiveness,and poor asthma control,which affected the prognosis of asthmatic patients.In order to investigate the condition of small airway function and the related influence factors of small airway dysfunction in controlled asthmatic children,we performed forced expiratory lung function,this study can provide treatment reference for clinicians.ObjectivesTo investigate the condition of small airway function and the related influence factors of small airway dysfunction in controlled asthmatic children.MethodsChildren diagnosed with bronchial asthma and symptoms controlled,aged 5-14 years old,male or female were consecutively enrolled.Survey questionnaire was filled by investigators,including asthma symptoms in the past one month,medication using now,then conducted physical examination and lung function testing,a part of patients completed the bronchodilation testing.Data were analysised by the SPSS19.0 software.Results1.A total of 327 controlled asthmatic children were included in this study,255 patients had normal ventilatory function,accounting for 78%,72 patients had ventilatory dysfunction,accounting for 22%.224 patients had normal small airway function,31 patients had small airway dysfunction,accounting for 12% of the normal ventilatory function group,9.5% of the controlled asthmatic children.2.The lung function parameters of FVC,FEV1,FEV1/FVC were(99.3 ± 9.3)%,(101.8 ± 10.4)%,(87.1 ± 4.4)% in normal ventilation function group;(102.4 ± 9.3)%,(93.6 ± 8.6)%,(76.6 ± 3.0)% in ventilation dysfunction group;There were significant difference between the two groups(t = 0.014,0.001,0.001,P <0.05).3.The lung function parameters of FVC,FEV1,PEF,FEV1/FVC were(100% ± 9.4%)%,(103.4 ± 9.8)%,(104.0 ± 12.1)%,(87.7 ± 4.3)% in normal small airway function group;(93.6 ± 6.6)%,(90.4 ± 6.0)%,(92.4 ± 6.2)%,(82.6 ± 1.9)% in small airway dysfunction group;There were significant difference between the two groups(t =4.845,10.245,8.435,11.348,P <0.05).4.The level of FEF50,FEF75 and MMEF were(87.9 ± 20.2)%,(73.8 ± 27.9)% and(84.9±20.6)% in children with normal small airway function group;(62.8 ± 5.6)%,(51.9 ± 8.9)% and(62.7 ± 7.2)% in children with small airway dysfunction group.FEF75 had shown the lowest level and biggest variability.5.In small airway dysfunction group,10 patients had conducted bronchodilation testing,improvement of FEF50,FEF75 and MMEF were 41.1%,47.5%,41.3%,10(100%)patients retured to normal level.5(50%)of 10 patients were positive when the bronchodilation testing was based on the FEV1 improvement rate ?12%,8(80%)of 10 were positive when the bronchodilation testing was based on the MMEF improvement rate ?25%,There were no significant difference between the two positive rates(?2 = 0.879,P> 0.05).6.To analyze the influence factors related to small airway dysfunction in cotrolled asthmatic children,including gender,age,height,body weight,BMI,disease duration,allergic rhinitis,allergen,drug usage between two groups.Medication was divided into three categories: combination therapy(ICS + LABA + LTRA or ICS + LARA or ICS + LABA);single therapy(ICS or LTRA);no therapy.No significant difference was found in gender,BMI,atopy,disease duration,drug usage between two gropus(P>0.05).7.In normal small airway function group,there were 19 patients using ICS+LABA+LTRA,93 patients using ICS+LABA,18 patients using ICS+LTRA,34 patients using ICS alone,36 patients using LTRA alone,24 patients no using;In small airway dysfunction group,there were 5 patients using ICS+LABA+LTRA,13 patients using ICS+LABA,3 patients using ICS+LTRA,5 patients using ICS alone,4 patients using LTRA alone,1 patients no using.ICS + LABA was the highest in both groups,accounting for 42% of each group.Conclusions 1.In 5-14 controlled asthmatic children,one-fifth(22%)had ventilation dysfunction,nearly one-tenth(9.5%)had small airway dysfunction.2.FEF75 had shown the lowest level.3.After bronchodilation testing,the small airway parameters with a certain degree of reversibility,FEF50,FEF75,MMEF represented the small airway has improved significantly than FEV1 represented the large airway.4.Gender,BMI,atopy,disease duration,drug usage were not the influencing factors of small airway dysfunction.