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Updated: Jul 15, 2026
Conducting Respiratory Oscillometry in an Outpatient Setting
Published on: April 8, 2022
Assessment of bronchodilator responsiveness in preschool children using forced oscillations
Cindy Thamrin1, Catherine L Gangell, Kanokporn Udomittipong
1Telethon Institute for Child Health Research, P O Box 855, West Perth, WA 6872, Australia.
Insights
Forced oscillation technique (FOT) bronchodilator (BD) testing in preschool children is best assessed using relative changes to account for baseline lung function. Recommended limits for a positive BD response are -40% for resistance and 65% for reactance.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
Background:
- The forced oscillation technique (FOT) is suitable for assessing respiratory function in preschool children due to minimal cooperation requirements.
- Limited data exist on bronchodilator (BD) responses using FOT in healthy young children, hindering clinical application of BD testing in this demographic.
- This study investigated quantifying BD responses via FOT in healthy children and those with cystic fibrosis, neonatal chronic lung disease, and asthma/wheeze.
Purpose of the Study:
- To determine the optimal method for quantifying bronchodilator (BD) responses using the forced oscillation technique (FOT) in preschool children.
- To compare BD responses in healthy children versus those with common respiratory conditions.
Main Methods:
- Respiratory resistance and reactance were measured using a pseudorandom FOT signal (4-48 Hz) at 6, 8, and 10 Hz.
- Measurements were taken before and 15 minutes after salbutamol administration, with 3-5 acceptable readings per session.
- Bronchodilator responses were analyzed as both absolute and relative (percentage of baseline) changes.
Main Results:
- Significant BD responses were observed across all participant groups.
- Absolute BD responses correlated with baseline lung function within each group.
- Relative BD responses showed less dependence on baseline lung function and were independent of height in healthy children. Neonatal chronic lung disease patients exhibited strong baseline dependence.
- Bronchodilator responses in children with cystic fibrosis, asthma, or wheeze were comparable to those in healthy children.
Conclusions:
- Relative change is the recommended method for expressing BD responses via FOT in preschool children to normalize for baseline lung function.
- Proposed thresholds for a positive BD response are -40% for respiratory resistance and 65% for respiratory reactance.
Background:
The forced oscillation technique (FOT) requires minimal patient cooperation and is feasible in preschool children. Few data exist on respiratory function changes measured using FOT following inhaled bronchodilators (BD) in healthy young children, limiting the clinical applications of BD testing in this age group. A study was undertaken to determine the most appropriate method of quantifying BD responses using FOT in healthy young children and those with common respiratory conditions including cystic fibrosis, neonatal chronic lung disease and asthma and/or current wheeze.
Methods:
A pseudorandom FOT signal (4-48 Hz) was used to examine respiratory resistance and reactance at 6, 8 and 10 Hz; 3-5 acceptable measurements were made before and 15 min after the administration of salbutamol. The post-BD response was expressed in absolute and relative (percentage of baseline) terms.
Results:
Significant BD responses were seen in all groups. Absolute changes in BD responses were related to baseline lung function within each group. Relative changes in BD responses were less dependent on baseline lung function and were independent of height in healthy children. Those with neonatal chronic lung disease showed a strong baseline dependence in their responses. The BD response in children with cystic fibrosis, asthma or wheeze (based on both group mean data and number of responders) was not greater than in healthy children.
Conclusions:
The BD response assessed by the FOT in preschool children should be expressed as a relative change to account for the effect of baseline lung function. The limits for a positive BD response of -40% and 65% for respiratory resistance and reactance, respectively, are recommended.
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