Sensitivity of bronchial responsiveness measurements in young infants.

OBJECTIVES There is limited evidence on the preferred methods for evaluating lung function in infancy. The objective of this study was to compare sensitivity and repeatability of indexes of lung function in young infants during induced airway obstruction. METHODS The study population consisted of 402 infants (median age, 6 weeks). Forced flow-volume measurements were obtained by the raised volume rapid thoracoabdominal compression technique and were compared with indexes of tidal breathing, measurements of transcutaneous oxygen (Ptco(2)), and auscultation during methacholine challenge testing. RESULTS Ptco(2) was the most sensitive parameter to detect increasing airway obstruction during methacholine challenge, followed by forced expiratory volume at 0.5 s (FEV(0.5)). Both were superior to other indexes of forced spirometry as well as tidal breathing indexes and auscultation. Coefficients of variations for Ptco(2) and FEV(0.5) were 4% and 7%, respectively. CONCLUSIONS Ptco(2) and FEV(0.5) are the most sensitive parameters for measurement of bronchial responsiveness in young infants. Measurements of baseline lung function should preferably be made using FEV(0.5.) Measurements of bronchial responsiveness are best assessed using Ptco(2), which may be performed in nonsedated infants and improve feasibility of future studies on lung function in infancy.