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Comparison of airway resistance and total respiratory system resistance in infants
C Springer1, D Vilozni, E Bar-Yishay
1Institute of Pulmonology, Hadassah University Hospital, Jerusalem, Israel.
Insights
Total respiratory system resistance (Rrs) closely estimates airway resistance (Raw) in healthy infants. However, Rrs may not accurately reflect dynamic Raw changes in infants with airway obstruction.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
Background:
- Airway resistance (Raw) is crucial for assessing respiratory health.
- Whole body plethysmography measures Raw throughout the respiratory cycle.
- Total respiratory system resistance (Rrs) is measured via relaxed expiration after end-inspiratory occlusion.
Purpose of the Study:
- To compare Raw and Rrs measurements in infants.
- To evaluate these methods in normal infants and those with varying airway obstruction.
Main Methods:
- Simultaneous measurement of Raw and Rrs in three infant groups: normal, congenital stridor, and wheezy.
- Analysis of measurements during different phases of the respiratory cycle.
Main Results:
- Rrs closely matched Raw in normal infants.
- Rrs approximated expiratory Raw in congenital stridor and inspiratory/early expiratory Raw in wheezy infants.
- Significant discrepancies between Raw and Rrs were observed during specific phases in obstructed airways.
Conclusions:
- Rrs is a reliable estimate of Raw in healthy infants and for early expiratory resistance in all infants.
- Rrs may not capture dynamic Raw changes or differentiate obstruction types in infants with airway compromise.
Abstract:
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.