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Short-term variations in oscillatory and spirometric lung function indices among school children
K L Timonen1, J T Randell, R O Salonen
1Unit of Environmental Epidemiology, National Public Health Institute Kuopio, Finland.
Insights
Respiratory resistance measured by forced oscillation technique (Rrs,FOT) shows greater variation than spirometry in children with chronic respiratory symptoms. However, Rrs,FOT is more sensitive for detecting short-term respiratory changes, despite lower day-to-day repeatability.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
- Diagnostic Techniques
Background:
- Chronic respiratory symptoms in children necessitate reliable lung function assessment.
- Forced oscillation technique (Rrs,FOT) offers an alternative to spirometry for measuring respiratory resistance.
- Understanding the variability of Rrs,FOT is crucial for its clinical application in pediatric respiratory monitoring.
Purpose of the Study:
- To compare the immediate, daily, and weekly variation of Rrs,FOT with spirometric indices in children aged 7-12 with chronic respiratory symptoms.
- To evaluate the sensitivity of Rrs,FOT and spirometry in detecting changes following an exercise challenge test.
Main Methods:
- Lung function measurements (Rrs,FOT and spirometry) were conducted on 19 children over 4 days across two consecutive weeks.
- Measurements were repeated three times daily at the same time.
- An exercise challenge test was performed on 12 children to assess dynamic changes in respiratory parameters.
Main Results:
- Intrasubject coefficients of variation (CoVs) for Rrs,FOT were generally larger than for spirometric indices, except for immediately repeated measurements.
- After applying a reliability index, immediate Rrs,FOT variation (9.1%) became comparable to airflow indices at specific lung volumes.
- Rrs,FOT demonstrated greater sensitivity to changes during the exercise challenge test compared to spirometry, but showed higher day-to-day (16.0%) and weekly variation.
Conclusions:
- While Rrs,FOT exhibits higher variability than most spirometric indices over days and weeks, its immediate measurement reliability is comparable.
- Rrs,FOT is a sensitive tool for detecting short-term functional changes in the pediatric respiratory system, particularly after exercise.
- The lower repeatability of Rrs,FOT over longer periods may limit its use in long-term follow-up studies of pediatric respiratory conditions.
Abstract:
The aim of this study was to compare immediate, daily and weekly variation in respiratory resistance measured by means of the forced oscillation technique (Rrs,FOT) to spirometric indices in 7-12 year old children with chronic respiratory symptoms. The lung function measurements were performed in 19 children on 4 days, i.e. two consecutive days during two consecutive weeks. On each day, the measurements were carried out at the same time of day and always repeated three times. In addition, Rrs,FOT and spirometric lung function indices were compared with an exercise challenge test in 12 children. Intrasubject coefficients of variation (CoVs) for Rrs,FOT were larger than those for spirometric indices. Only in the immediately repeated measurements was the CoV of maximal expiratory flow at 25% vital capacity larger than that of Rrs,FOT (16.6 vs 14.9%). At all time intervals, the smallest CoVs were observed in forced vital capacity (FVC) or in the ratio of forced expiratory volume in one second to FVC (2.0-2.6%). When excluding Rrs,FOT values which were not within 2 SD (0.11 kPa.L-1.s) of the differences between the immediately repeated measurements, the CoV of the immediately repeated measurements of Rrs,FOT was reduced to 9.1%, being smaller than that of maximal mid-expiratory flow (10.1%). However, even then the day-to-day variation in Rrs,FOT was clearly larger (16.0%) than those of the airflow indices at specified lung volumes (7.2-8.3%). This was also true for the weekly variation. In the exercise challenge test, there were larger changes in Rrs,FOT values than in the spirometric indices, but Rrs,FOT was the most sensitive index to detect changes in the respiratory system. In conclusion, the variation in Rrs,FOT values was larger than that of most spirometric indices. When a reliability index was applied, the immediate variation in Rrs,FOT values was comparable to those of the airflow indices at specified lung volumes. Rrs,FOT was also the most sensitive index in the exercise challenge test, and therefore it seems to be suitable for detection of short-term functional changes in the respiratory system. However, the relatively low repeatability of Rrs,FOT over days and weeks may limit its applicability to longer-term follow-ups.