Implications of Airway Resistance and Conductance on the Respiratory Rate in individuals With Various Nutritional States Exposed To Exercise

Purpose: To determine how airway resistance (RAW) and airway conductance (GAW) affect inspiratory time (iT) and expiratory time (eT) in subjects with different nutritional states using the step test.
Methods: Forty-eight participants were recruited and divided into three groups: 16 normal weight (NW), 16 overweight (OW), and 16 obese (OB). A lung function test and anthropometric evaluation were performed. iT and eT were measured using a sonographic device before and after the step test.
Results: Body Mass Index (BMI) and Body Fat Percentage (BF%) were significantly higher (P< 0.0001; P< 0.0001, respectively) in OB group. RAW was significantly higher in the OB group (P=0.004), and GAW (P=0.004) was significantly lower in the same group. At rest, the Respiratory Rate (RR) was significantly higher in OB group (P< 0.05), while iT and eT showed no significant differences. On the other hand, after the step test, eT was significantly lower (P=0.016), with the multiple linear regression model being the best predictor of post-exercise eT, including BF%/GAW and BF%/sGAW (explained variability of 15.7% and 14.6%, respectively).
Conclusion: Nutritional status can significantly impact lung function; at rest, there was a decrease in lung volumes and an increase in RR in OB subjects. In addition, there was a significant decrease in eT of OB subjects post-exercise. Finally, a significant relationship of BF%/GAW and BF%/sGAW with post-exercise eT was noted.

Keywords: airway resistance, airway conductance, respiratory time, nutritional states