Comparison of FEV1 and transcutaneous oxygen tension in the measurement of airway responsiveness to methacholine.

The measurement of airway responsiveness in preschool children is hampered by the fact that most tests of airway caliber are difficult to carry out at a young age. Patient cooperation is only needed to a limited extent when transcutaneous oxygen tension (PtcO2) is used as an indicator of airway obstruction following bronchial provocation. In 51 children, aged 6-14 years with asthma we have measured PtcO2 and forced expiratory volume in 1 second (FEV1) concurrently after bronchial provocation, using increasing doses of methacholine administered with a De Villbiss 646 nebulizer and a French-Rosenthal dosimeter. The shapes of the dose-response curves to PtcO2 and FEV1 show a close similarity. After methacholine challenge, the decrease in PtcO2 correlates highly with the decrease in FEV1. We conclude that in children a 20% decrease in PtcO2 can be used as a sensitive indicator of airway narrowing after methacholine challenge.