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Regression Equations of Respiratory Impedance Measured by Forced Oscillation Technique for Indian Children

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To develop regression equations of within and whole-breath respiratory impedance for Indian children aged 5 to 17 y.


A prospective cross-sectional study was carried out in 5 to 17 y old school children of Bhopal, India. Healthy children were identified by physical examination and by administering questionnaire. The respiratory system resistance (Rrs) and reactance (Xrs) were measured at frequency of 5, 11, and 19 Hz by forced oscillation technique (FOT). The regression equations of within and whole-breath Rrs and Xrs were developed separately for boys and girls by multiple linear regression models.


Total 336 children were recruited and data of 320 healthy children (boys – 159), standing height of 146.1 ± 16.6 cm and body mass index of 17.2 ± 2.9 kg/m2 were included in the analysis. The mean respiratory system resistance at 5 Hz (R5) and respiratory system reactance at 5 Hz (X5) of the children, irrespective of gender were 5.46 ± 2.10 cmH2O/L/s and − 1.43 ± 0.85 cmH2O/L/s respectively. Boys of age 16 y and older had significantly smaller Rrs as compared to girls of corresponding age (p < 0.05). The standing height of children had the highest predictive power, followed by age in the regression model. With an increase in standing height, the magnitude of both Rrs and Xrs values of children decrease. The bodyweight of children had a negligible contribution to the regression models.


The regression equations of within- and whole-breath Rrs and Xrs of Indian children aged 5 to 17 y are presented for the first time. The R5 values of Indian children were comparable to children of other ethnicities.

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The authors would like to thank Indian Council of Medical Research for funding. They also thank their staff Mr. Gagan Deep Singh Kushwah, Mr. Dharmendra Dharwey, Mr. Mohd Qmar Khan and Gagan Dhaneshwar for their contribution in collecting the data.

Author information

SD designed the study, made the protocol and drafted the final manuscript. NB helped to collect the data and RRT helped in analysis. All authors contributed to the finalization of the manuscript. SD is the guarantor for this article.

Correspondence to Sajal De.

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Indian Council of Medical Research.

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De, S., Banerjee, N. & Tiwari, R.R. Regression Equations of Respiratory Impedance Measured by Forced Oscillation Technique for Indian Children. Indian J Pediatr 87, 192–199 (2020).

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  • Forced oscillation technique
  • Within-breath
  • Whole-breath
  • Respiratory impedance
  • Regression equations
  • Children