Analysis Of Pulmonary Function Indexes And Target Heart Rate Arrival And Maintenance Time During Exercise Challenge Test In Asthmatic And Suspected Asthmatic Children

Objective:To analyze the variation of pulmonary function indexes with time,the effect of target heart rate arrival and maintenance time on the decline rates of pulmonary function indexes and the application of small airway parameters decline rates in children’s exercise challenge test（ECT）.Methods:A retrospective analysis was conducted on 60 cases of asthma and suspected asthma children treated in Children’s Hospital Affiliated to Chongqing Medical University from November 2016 to September 2020.All the children successfully completed bicycle ergometer ECT.A decrease of≥10%in forced expiratory volume in one second（FEV₁）was considered as positive test.The basic data and pulmonary function data before and after the test were collected.The variation of pulmonary function indexes with time was analyzed.Children were divided into two groups according to their target heart rate arrival time≤4min and>4min.And they were also divided into two groups according to their target heart rate maintenance time≥4min and<4min.The differences in the decline rates of pulmonary function indexes were analyzed in the two groups.The relationship between small airway parameters decline rates and FEV₁decline rate was analyzed,and the receiver operating characteristic（ROC）curves were used for diagnostic experimental evaluation of ECT result.Results:1.Comparison of basic data between ECT positive and negative group:A total of 60 subjects aged 6 to 15 years were included in this study,including 11（18.33%）in the ECT positive group and 49（81.67%）in the negative group.There were no statistically significant differences in age,gender,height,weight,BMI,target heart rate arrival time,total exercise time and adverse reactions between the positive group and the negative group（all P>0.05）.The maintenance time of target heart rate in the positive group was significantly longer than that in the negative group,with statistical significance（P<0.05）.2.Comparison of lung function indexes between ECT positive and negative group:There were no statistically significant differences in the basic values of FVC,FEV₁,PEF,FEF₂₅,FEF₅₀,FEF₇₅ and MMEF between the positive and the negative group（all P>0.05）.The decline rates of FVC,FEV₁,PEF,FEF₂₅,FEF₅₀,FEF₇₅and MMEF in the positive group were significantly higher than those in the negative group,with statistical significance（all P<0.05）.3.The variation of pulmonary function indexes after exercise:55 cases（91.67%）reached the maximum decrease rate of FEV₁ within 15 minutes after exercise,and the number of children with the maximum decrease rate of FEV₁ gradually decreased with time.The pulmonary function indexes decreased in different degrees after exercise,and gradually recovered after 20min.4.Target heart rate arrival and maintenance time and the decline rates of lung function indexes:Among the 60 cases,26 cases（43.33%）had a target heart rate arrival time≤4min,25 cases（41.67%）had a target heart rate maintenance time≥4min,and 12 cases（20%）had a target heart rate arrival time≤4min and a target heart rate maintenance time≥4min.The decline rates of FVC,FEV₁,PEF and FEF₂₅ in the target heart rate maintenance time≥4min group were higher than those in the target heart rate maintenance time<4min group,the difference was statistically significant（P<0.05）.5.Correlation between the decline rates of small airway parameters and the decline rate of FEV₁:The decline rates of FEF₅₀,FEF₇₅ and MMEF were positively correlated with the decline rate of FEV₁（r=0.711,0.772,0.849,all P<0.001）.6.ROC analysis:The areas under the curves of FEF₅₀,FEF₇₅ and MMEF decline rates for a positive ECT were 0.926,0.955 and 0.985respectively（all P<0.001）,optimal cutoff values were 21.00%（with sensitivity 0.818,specificity 0.878）,29.50%（with sensitivity 0.818,specificity 1.000）and 17.50%（with sensitivity 0.909,specificity 0.980）.Conclusion:During children’s ECT,the large airway and the small airway have different degrees of contraction after exercise,and gradually recover after 20 minutes.The target heart rate maintenance time can affect the contraction of the large airway.The decline rates of small airway parameters are positively correlated with the decline rate of FEV₁.The decline rates of small airway parameters have a good predictive value for ECT results.When reviewing the reports,pediatricians should pay attention to whether the guidelines have been met,such as the target heart rate maintenance time,and pay attention to small airway parameters decline rates,in order to evaluate the reliability and applicability of the results,so as to make a more reasonable clinical diagnosis and treatment plan.