A Correlative Study Of Air-trapping On Lung HRCT With Pulmonary Function Tests In Asthmatic Children

ObjectiveDetecting imaging findings of air trapping on end expiratory HRCT in asthmatic children,and analyzing the correlation between area of air trapping and measures of pulmonary function tests(PET)that reflect airway obstruction,e.g.FEV1,FEF_25-75%, etc.Materials and MethodsLung HRCT scans were abtained at end expiration in 21 asthmatic children,and on the same day or second day PET were performed.Two visible sections of air trapping were respectively chosen at the upper,middle and lower lung.The areas of air trapping were calculated manually by using a lucent grid.By the percentage of area of air trapping at the total area of the lung,the degree of air trapping was classified into three grades:gradeⅠ,＜5%;gradeⅡ,5%～25%;Ⅲ,＞25%.Then analyzing the correlation between the grades of air trapping and measures of pumonary function tests.Results1 The frequency of air trapping on end expiratory lung HRCT in asthmatic children,is very high,is 90.5%(19/21);2 Lower lobe is the most commonly occurred part of air trapping,is found 100%(19/19).3 The grades of air trapping had a significant correlation with measures of PET:FEV1,FEF_25-750%,FEF_50%(r=-0.565,P＜0.01; r=-0.499,P＜0.05;r=-0.521,P＜0.05).4 The data also indicates that the measures of PET of most subjects in this study is normal,i.e.FEV1>80%and FEF_25-75%＞70%,the percentage of the subjects whose PET is normal at all subjects is 76%(16/21).There is obvious air-trapping in Lung HRCT of asthmatic children whose PET is normal.Even though the grade of air trapping reach toⅡ,Ⅲgrade,PET may be normal.ConclusionAir trapping on on end expiratory lung HRCT can directly reflect heterogeneous distribution and degree of airway diseases;air trapping appears more earlier than abnormity of PET and has a more sensitivity than PET;Air trapping on on end expiratory lung HRCT can assess small airway function of asthmatic children,which is a useful tool which diagnoses and assesses asthma.