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Methacholine challenge in pre-school children--which outcome measure?
J Kivastik1, A-M Gibson, R A Primhak
1Academic Unit of Child Health, University of Sheffield, Western Bank, S10 2TH Sheffield, UK. Jana.Kivastik@ut.ee
Insights
Interrupter resistance and transcutaneous oximetry offer objective measures for methacholine challenges in preschool children. These methods may detect bronchial hyper-responsiveness earlier than traditional assessments.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
- Allergy and Immunology
Background:
- Pediatric asthma diagnosis often relies on subjective assessments.
- Standardized methacholine challenges are crucial for diagnosing bronchial hyper-responsiveness.
- Objective outcome measures are needed for methacholine challenges in young children.
Purpose of the Study:
- To evaluate interrupter resistance (Rint) and transcutaneous oximetry as objective outcome measures.
- To assess the utility of these measures in a tripling-dose methacholine (Mch) challenge protocol.
- To compare Rint and transcutaneous oximetry with traditional auscultation in preschool children.
Main Methods:
- 57 children aged 3-6 years underwent a Mch challenge with increasing doses.
- Rint was measured at baseline and post-Mch inhalation.
- Oxygen saturation (SaO2) and transcutaneous oxygen pressure (tcpO2) were monitored.
- Challenge termination criteria included wheeze, SaO2 < 91%, or persistent cough (PCW).
Main Results:
- Adequate Rint measurements were obtained in 78% of children.
- Complete tcpO2 data was achieved in 76% of children.
- Significant changes in Rint or tcpO2 often preceded the clinical endpoint (PCW).
Conclusions:
- Rint and tcpO2 provide objective, less subjective measures for Mch challenges.
- These methods may detect bronchial hyper-responsiveness at lower Mch doses.
- While feasible in many, Rint and tcpO2 are not universally applicable in all preschool children.
Abstract:
The aim of our study was to evaluate the utility of interrupter resistance (R(int)), transcutaneous oximetry and auscultation as outcome measures for a recently suggested tripling-dose methacholine (Mch) challenge in pre-school children. We studied 57 children aged 3-6 years. R(int) was measured at baseline and after each Mch dose. Oxygen saturation (SaO(2)) and transcutaneous oxygen pressure (tcpO(2)) were monitored during the challenge. Mch concentrations of 0.22, 0.66, 2.0, 6.0 and 18.0 mg/ml were nebulised during tidal breathing. The challenge was terminated if there was wheeze, SaO(2) below 91% or persistent cough; this final Mch dose was considered as PCW. Nine healthy children, 17 with cough and 25 with wheeze performed the study up to the point of PCW or all five Mch inhalations. If a change of 20% of predicted R(int) or termination by wheeze, desaturation or cough is taken as a completed test, then 39 out of 51 children (78%) had adequate R(int) measurements on each occasions from start to completion. The success rate for tcpO(2) measurements was similar: 38 out of 51 (76%) had complete tcpO(2) data until a 15% fall of tcpO(2) or clinical endpoint was reached. Using the above-mentioned cut-off levels significant change in R(int) or tcpO(2) preceded PCW in most of the cases. Both R(int) and tcpO(2) measurements may allow detection of bronchial hyper-responsiveness at lower Mch doses and also provide a less subjective measure, but will not be feasible in all children.
