Regression equations of respiratory impedance of Indian adults measured by forced oscillation technique

Background: Forced oscillation technique (FOT) is a technique to measure the mechanical properties of the lung. The present study was aimed to develop regression equations of within- and whole-breath respiratory impedance (Zrs) of healthy Indian adults. Methods: Total 323 adults were sequentially screened. Smokers, individuals with respiratory symptoms or diseases, and unable to perform acceptable FOT were excluded. Within- and whole-breath resistance (Rrs) and reactance (Xrs) were measured at 5, 11, and 19 Hz by Resmon Pro (R) Full device. The regression equations of within- and whole-breath Rrs and Xrs were generated separately for men and women by multiple linear regression models. Results: The FOT data of 253 individuals (122 men) aged 18-81 years were included in the analysis. The magnitudes of whole-breath Rrs at 5 Hz (4.53 +/- 1.05 cmH(2)O/L/s in women vs. 3.26 +/- 1.05 cmH(2)O/L/s in men; P = 0.000) and whole-breath Xrs at 5 Hz (-1.23 +/- 0.66 cmH(2)O/L/s in women vs. -1.00 +/- 0.54 cmH(2)O/L/s in men; P = 0.003) of women were significantly of higher magnitude as compared to men. The standing height was the best determinant of Zrs, followed by body weight; the effect of age was negligible and was observed in men only. The magnitudes of both Rrs and Xrs decrease with an increase in standing height of both men and women. Conclusions: The present study provides regression equations of within- and whole-breath respiratory impedance of Indian adults.