Comparison of airway resistance and total respiratory system resistance in infants

Am Rev Respir Dis. 1993 Oct;148(4 Pt 1):1008-12. doi: 10.1164/ajrccm/148.4_Pt_1.1008.


Airway resistance (Raw) can be measured throughout the respiratory cycle by whole body plethysmography. Total resistance of the respiratory system (Rrs) can be measured from the relaxed expiration that follows end inspiratory occlusion. The purpose of this study was to compare the two methods in normal infants and in infants with airway obstruction of different types and severity. Fifteen infants with essentially normal lungs aged 24.6 +/- 18.0 (SD) wk, nine infants with congenital stridor aged 36.0 +/- 17.3 wk, and eleven wheezy infants aged 20.1 +/- 11.3 wk had simultaneous measurements of Raw and Rrs. Rrs was similar to Raw both during inspiration and expiration in the normal infants, to all expiratory Raw in those with congenital stridor, and to all inspiratory and early expiratory Raw in the wheezy infants. Raw was markedly and significantly higher than Rrs during mid and late inspiration in infants with congenital stridor and during late expiration in the wheezy infants. We conclude that Rrs is a good estimate of Raw in normal infants and of early expiratory Raw in all infants. In infants with airway obstruction, Rrs does not reveal the dynamic changes in Raw during tidal breathing, nor can it differentiate between infants with upper and lower airway obstruction.

Publication types

  • Comparative Study

MeSH terms

  • Airway Resistance*
  • Analysis of Variance
  • Apnea / epidemiology
  • Apnea / physiopathology
  • Female
  • Humans
  • Infant
  • Linear Models
  • Male
  • Plethysmography, Whole Body / methods
  • Plethysmography, Whole Body / statistics & numerical data
  • Recurrence
  • Reference Values
  • Respiratory Function Tests / methods
  • Respiratory Function Tests / statistics & numerical data
  • Respiratory Physiological Phenomena*
  • Respiratory Sounds / physiopathology