Within- and between-day variability of respiratory impedance, using impulse oscillometry in adolescent asthmatics
Related Experiment Video
Updated: Sep 29, 2026
Conducting Respiratory Oscillometry in an Outpatient Setting
Published on: April 8, 2022
Michael D Goldman1, Rick Carter, Robert Klein
1Clinical Trials Unit, Charles R. Drew University of Medicine and Science, Los Angeles, California 90034, USA. mdg@ucla.edu
Insights
Impulse oscillometry (IOS) detects day-to-day changes in asthmatic children
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
- Medical Technology
Background:
- Asthma management requires sensitive tools to monitor airway changes.
- Spirometry is standard, but impulse oscillometry (IOS) may offer greater sensitivity.
- Assessing respiratory impedance via IOS can provide insights into airway mechanics.
Purpose of the Study:
- To evaluate impulse oscillometry (IOS) for assessing respiratory impedance in stable asthmatic children over three days.
- To compare inspiratory and expiratory forced oscillation (FO) parameters.
- To determine the effect of cheek support on IOS measurements.
Main Methods:
- Clinically stable asthmatic children underwent twice-daily IOS testing for three consecutive days.
- Measurements included respiratory resistance (R) and reactance (X) with and without cheek support.
- Statistical analyses (ANOVA, regression) were used to compare techniques and identify significant differences.
Main Results:
- IOS indices, including inspiratory resistance (R5) and frequency dependence of resistance (R5-R15), showed significant day-to-day variability.
- Spirometric indices remained unchanged across the study period.
- Inspiratory resistance was consistently lower than expiratory resistance (P < 0.0001).
- Cheek support minimally affected IOS measurements below 15 Hz.
Conclusions:
- IOS is a sensitive method for detecting subtle changes in bronchomotor tone in asthmatic adolescents.
- Inspiratory R5, R5-R15, and reactance area (AX) are valuable IOS metrics.
- IOS is a practical tool for quantifying respiratory mechanics, with potential for asthma management.
Abstract:
The objectives of the present study were to: 1) assess spirometric indices and respiratory impedance with forced oscillation (FO), using impulse oscillometry (IOS) in clinically stable asthmatic children over 3 consecutive days; 2) assess FO reactance (X), using an integrated index and resistance (R) separately during inspiration and expiration; and 3) assess effects on FO of hand support of cheeks vs. no hand support. Our hypotheses were: 1) because of increased sensitivity, IOS manifests day-to-day variability not demonstrable by spirometry; 2) IOS R during expiration exceeds that during inspiration; and 3) hand support of cheeks affects IOS R and X only minimally. We obtained triplicate twice-daily measures of IOS R and X in asthmatic adolescents at summer camp, in a convenience sample of children willing, with parental permission, to undergo repeated testing on consecutive days. Subjects received all medications between 6:30-7:30 AM, and were bronchodilated at time of testing. Subjects underwent IOS tests without hand support of cheeks, followed by tests with both hands supporting cheeks. ANOVA and regression analyses were used to discern technique differences.Significant differences in IOS inspiratory R5, R5 - R15 (frequency dependence of R), and low frequency reactance area (AX) occurred across 3 days, but spirometric indices were unchanged. Inspiratory R at 5 Hz (R5) was significantly smaller than expiratory R5 (P < 0.0001). ANOVA revealed no significant differences between hand and facial muscle cheek support for IOS R and X below 15 Hz, but significant differences occurred above 15 Hz. In conclusion, inspiratory R5, R5 - R15, and AX are sensitive measures for detecting changes in bronchomotor tone in adolescent asthmatic subjects, while expiratory R5 may be influenced by additional factors. Manual support of cheeks does not appear to affect IOS indices of peripheral airway obstruction in adolescent asthmatics. IOS is a practical method for quantifying respiratory mechanics, and its potential role in disease management warrants further study.
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