Lung function response to cold air challenge in asthmatic and healthy children of 2-5 years of age

The aim of the study was to assess feasibility, sensitivity, specificity, p redictive value, and repeatability of cold, dry air challenge (CACh) as a d iagnostic test for asthma in young children 2 to 5 yr of age. Response to a 4-min single-step isocapnic CACh was measured in 38 asthmatics and 29 cont rol subjects. Specific airway resistance (sRaw) by whole body plethysmograp hy was the primary outcome. In addition, lung function was measured as resp iratory resistance by the interrupter technique (Rint) and respiratory resi stance and reactance at 5 Hz (Rrs5, Xrs5) by the impulse oscillation techni que. At baseline, lung function measures differed significantly between ast hmatics and healthy control subjects. CACh was readily performed in young c hildren. Response was expressed as change from baseline in numbers of withi n-subject standard deviation (SDw). Hyperresponsiveness defined as change i n lung function of more than 3 SDw was detected by sRaw in 26 of 38 asthmat ics versus 2 of 29 control subjects, by Rint in 12 of 38 asthmatics versus 1 of 29 control subjects, by Xrs5 in 9 of 38 asthmatics versus zero of 29 c ontrol subjects and by Rrs5 in 7 of 38 asthmatics versus 1 of 29 control su bjects. Thus sRaw had the highest sensitivity (68%). Specificity ranged fro m 93 to 100%. The correlation coefficient between sRaw responses to CACh re peated within 8 wk was 96%. In conclusion, CACh is feasible in young childr en age 2 to 5 yr. Whole body plethysmography (sRaw) was superior in separat ing asthmatics from healthy control subjects. Change in sRaw in response to CACh may be used as a diagnostic test for asthma in young children.