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

Abstract

Methacholine challenge in preschool children: methacholine-induced wheeze versus transcutaneous oximetry. S.C. Yong, C.M. Smith, R. Wach, M. Kurian, R.A. Primhak. # ERS Journals Ltd 1999. ABSTRACT: Tracheal/chest auscultation for wheeze and transcutaneous oximetry have both been suggested as measures of outcome in bronchial provocation tests in young children. This study aimed to compare the sensitivity and safety of these two techniques as end-points for methacholine challenge in children aged <4 yrs.Seventy-two methacholine challenges were performed in 39 children aged <4 yrs with recurrent wheeze. Arterial oxygen saturation (Sa,O 2 ) and transcutaneous oxygen pressure tcPO 2 continuously, and the test was terminated when wheeze was heard or at Sa,O 2 <91%. tcPO 2 was not used as an end-point.Wheeze or desaturation occurred at #8 mg . mL -1 methacholine in every test. One child had transient clinical cyanosis, but no other 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 responses 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 significant rise.Tracheal/chest auscultation with Sa,O 2 monitoring is a sensitive and relatively safe end-point for bronchial challenges in preschool children. The erratic pattern of transcutaneous oxygen pressure response in some children casts doubt on its reliability as a proxy measure of bronchial obstruction. Eur Respir J 1999; 14: 1175±1178. The measurement of bronchial responsiveness in preschool children is a potentially useful clinical and research tool, but it is hampered by the fact that lung function measurement in preschool children is technically difficult without sedation. Several indirect methods have been used to assess bronchial responsiveness to methacholine challenge in this age group. Tracheal or chest auscultation can be used to measure the provocative concentration of methacholine which induces audible wheeze (PCW) [1,2]. This technique does not require full co-operation of the children, and it has been demonstrated in older children that the value for PCW was similar to that causing a 20% fall in forced expiratory volume in one second (FEV1) [2]. Other authors have favoured measuring the transcutaneous oxygen tension (tcPO 2 ), arguing that it is effort independent, reliable and repeatable and is superior to tracheal auscultation [3±5]. The methodology of the study by WILSON et al. [4] involved cessation of challenge when tcPO 2 fell by 20%, which may have censored the PCW data.As part of a dose-ranging study of inhaled salmeterol in preschool children [6], the current study set out to reevaluate these two challenge endpoints. The aim of the study was to compare the sensitivity and safety of using audible wheeze and tcPO 2 in a methacholine challenge in children <4 yrs of age. Methods SubjectsChildren aged <4...

Early detection of airway obstruction by impulse oscillometry system in methacholine challenge testing in preschool children

“…The percent change, z score, and DRS of FEV 1 were statistically different between groups, but the IOS test showed no significant difference except for DRS result ( (Figure 1). Moreover, DRS of Rrs 5 and Xrs 5 were strongly correlated with each other (r=0.911, P<0.001). …”

“…We therefore used the dose-response slope, 22,23 PC 80 _Xrs 5 8,23,24 and PC 40 _Rrs 5 14,25,26 to compare bronchial hyperresponsiveness in our EOT + and EOT − groups. PC 80 _Xrs 5 and PC 40 _Rrs 5 positive means that the rate of change in the last step from baseline decreased by 80% or more in reactance and increased by 40% or more in resistance when measuring with IOS. The method of calculating DRS is briefly described as follows.…”

“…All parameters demonstrated significant changes when compared with the previous step (P<0.001). Using ROC curves, we determined the relationship between the sensitivity and specificity in the percent change of Xrs 5 and Rrs 5 for predicting of PC 80 _Xrs 5 and PC 40 _Rrs 5 (Figure 4). The AUC of Xrs 5 (0.837, 95% CI 0.765-0.909) was larger than that for Rrs 5 (0.812, 95% CI 0.744-0.879).…”

“…The end point of a challenge for the EOT positive group (EOT + ) was defined as one or more of the following: (a) audible wheeze over the chest or trachea (provocation concentration of wheezing; PCW + ); (b) oxygen saturation below 91% (provocation concentration of saturation; PCS + ); or (c) respiratory symptoms such as persistent cough, shortness of breath, or tachypnea for which the children were unable to sustain the test (provocation concentration of respiratory symptoms; PCr + ). 4,5 Subjects were defined as EOT negative (EOT − ) if they reached a methacholine concentration of 16 mg/mL without developing these manifestations. Each subject inhaledsolution for 1 minute using a nebulizer (DeVilbiss Health Care Inc., Somerset, PA) and a facemask, continuing every 5 minutes until the maximum concentration or end point was reached.…”

“…22,23 We obtained the cumulative dose at each level expressed in micromoles as 0.014, 0.072, 0.302, 1.222, and 4.901 mmol, respectively, which were obtained using the molecular weight of methacholine chloride (195.7 g/mol). The slope was defined as log (percent change in X/last cumulative dose), where X represents Rrs 5 , Xrs 5 , and FEV 1 .…”