Inspiratory Conductance does not vary with Height, Weight, Body Mass Index, Age, Sex or Spirometric Volumes in Healthy Adults.

Abstract

Introduction and objective: We previously showed that inspiratory conductance (IC) can be calculated from early inspiratory pressure fall and initial acceleration of the inspiratory air column. To characterize IC further we conducted a study to determine whether its value varies with height, weight, BMI, age, sex and lung volumes. Methods: We measured IC, height, weight, FEV1, FVC and PEFR in 147 healthy volunteers’ age 18-50 years. Results: During tidal breathing at rest the mean (SD) IC was 8.31 (3.15) L s-1 kPa-1. No significant correlation was found between IC and height (r=0.04), weight (r=0.142), BMI (r=0.058), FEV1 (r=0.275), FVC (r=0.019), PEFR (r=0.182) or age (r=0.017) and there was no significant difference between men and women. The same was found for IC measured during slow deep breathing and rapid breathing. Conclusion: IC is independent of age, sex, height, weight, BMI and spirometric lung volumes so there is no imperative to correct for those factors in an individual. Within-subject directional changes in IC within the context of a short clinical timeframe might be the best potential for clinical application.