Methacholine challenge in preschool children: methacholine-induced wheeze versus transcutaneous oximetry

Tracheal/chest auscultation for wheeze and transcutaneous oximetry have bot h been suggested as measures of outcome in bronchial provocation tests in y oung children. This study aimed to compare the sensitivity and safety of th ese two techniques as end-points for methacholine challenge in children age d <4 yrs. Seventy-two methacholine challenges were performed in 39 children aged <4 y rs with recurrent wheeze. Arterial oxygen saturation (Sa,O-2) and transcuta neous oxygen pressure tcPO(2) continuously, and the test was terminated whe n wheeze was heard or at Sa,O-2 <91%. tcPO(2) was not used as an end-point. Wheeze or desaturation occurred at less than or equal to 8 mg.mL(-1) methac holine in every test. One child had transient clinical cyanosis, but no oth er ill-effects were seen. Fifty-six tests (78%) were terminated for wheeze, seven (10%) for fall in Sa,O-2 and nine (12%) showed simultaneous response s in both parameters. Twenty-eight tests (39%) contained a fall in tcPO(2) >3 kPa but six of these also showed a significant rise. Fifty-three tests ( 75%) contained a fall in tcPO(2) >15%, but 20 of these also showed a signif icant rise. Tracheal/chest auscultation with Sa,Oz monitoring is a sensitive and relati vely safe end-point for bronchial challenges in preschool children, The err atic pattern of transcutaneous oxygen pressure response in some children ca sts doubt on its reliability as a proxy measure of bronchial obstruction.