Reference ranges for Mexican preschool-aged children using the forced oscillation technique.

INTRODUCTION Recently, multi-ethnic reference ranges for spirometry have been created for use worldwide. In comparison, forced oscillation technique (FOT) reference values are limited to specific equipment and study populations, with current FOT reference ranges created in a Caucasian population. We aimed to develop FOT reference ranges for preschool-aged Mexican children and to compare these with current FOT reference ranges. PATIENTS AND METHODS Respiratory resistance (Rrs) and reactance (Xrs) was measured in healthy Mexican children three to five years of age using commercial FOT equipment. The relationship between height and Rrs and Xrs was determined using regression analyses, taking into account age, weight, sex, and exposure to tobacco smoke. Reference equations were calculated for the Mexican children and Z-scores determined for Rrs and Xrs at 6 and 8Hz. A paired t-test assessed the difference in Z-scores between the Australian reference values and those created for the Mexican cohort. RESULTS FOT was successfully measured in 584 children. Height was a significant predictor of Rrs and Xrs at 6 and 8Hz (P<.05). Z-scores calculated using the Australian reference equations overestimated lung function in Mexican children for both Rrs and Xrs at 6 and 8Hz (P<.001). CONCLUSION The development of FOT reference ranges specific to Mexican preschool-aged children will allow for the correct interpretation of FOT measurements. This study also showed that current FOT reference ranges overestimate lung function in Mexican children. Highlighting, the importance of using ethnic appropriate reference ranges for interpreting lung function.