Chest
Volume 113, Issue 5, May 1998, Pages 1322-1328
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Clinical Investigations: Miscellaneous
Pediatric Reference Values for Respiratory Resistance Measured by Forced Oscillation

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Objectives

To determine, in North American children, reference values for respiratory resistance measurements by the forced oscillation (Rfo) technique and to examine whether sitting height, as index of truncal length, is a better determinant of resistance, less influenced by race and gender, than standing height.

Design/setting

A prospective cross-sectional study of healthy nonobese children, carefully selected for absence of atopy, exposure to tobacco smoke, and recent upper respiratory tract infection.

Measurements

Three measurements of respiratory resistance by forced oscillation were obtained at the fixed frequencies of 8 Hz (Rfo8), 12 Hz (Rfo12), and at 16 Hz (Rfo16) using the Custo Vit R (Custo Med GMBH; Munich, Germany). In cooperative children, routine spirometry (FEV1, FVC, and peak expiratory flow rate [PEFR]) was also performed.

Results

We recruited 217 healthy children aged 3 to 17 years. Reproducible measurements of Rfo8 were obtained for 206 children, Rfo12 for 197 children, and Rfo16 for 209 children. Normal FEV1, FVC, and PEFR values were documented in all 69 subjects who were able to reproducibly cooperate with spirometry. Multiple linear regression identified measurements of either sitting or standing height as the best, and equally strong, determinants of respiratory resistance at all three frequencies. Gender and race were not important factors once either sitting or standing height measurement was considered. Our regression equations at 8 Hz are comparable to published reference values obtained at fixed frequencies of 6, 8, and 10 Hz using other instruments. However, in comparison to our results, prior values tended to underestimate resistance in the shortest children or to overestimate it in the tallest ones. Our regression equation for Rfo12 is similar to the only previously published one, while no reference values at 16 Hz were available for comparison.

Conclusions

Height is the best predictor for total respiratory resistance at 8, 12, and 16 Hz in children aged ≥3 years. Use of sitting height does not appear to be a stronger determinant of resistance than standing height.

Section snippets

MATERIALS AND METHODS

We conducted a cross-sectional study of patients and/or accompanying siblings, aged 3 to 17 years, who presented to the orthopedic clinic or the surgical emergency department of the Montreal Children Hospital, Patients were accrued over two consecutive summers. The protocol was reviewed and approved by the Institutional Review Board and informed consent for participation in the study was obtained from parents or guardians.

RESULTS

During the study period, 1,725 children were screened using the self-administered questionnaire. Of these, 1,443 subjects were excluded because of the following nonmutually exclusive reasons: (1) family history of wheezing or asthma (52%, n = 819); (2) personal history of wheezing or asthma (33%, n=566); (3) personal history of rhinitis or eczema (39%, n=672); and (4) active or passive smoking (59%, n=1,025). Of the remaining 282 subjects, 52 were not approached due to practical reasons such as

DISCUSSION

In this group of 217 carefully selected healthy children, Rfo was closely related to (standing or sitting) height, with 65 to 72% of the variance explained by either stature measurement. After log transformation of height and resistance, neither gender and race were important predictors of resistance. Furthermore, sitting height was not a significantly better predictor of resistance than standing height.

This study presents reference values for Rfo8, Rfo12, and Rfo16 with 5th and 95th

ACKNOWLEDGMENT

We are indebted to the many patients, registration personnel, and the two research nurses (Jacques Lauzon and Francine Proulx) at the Montreal Children's Hospital whose collaboration made this study possible. We thank Michele Gibbon for her data processing, Marie-Claude Guertin for biostatistical assistance, and Judy Fuoco for manuscript preparation.

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  • Cited by (0)

    Supported by the McGill University-Montreal Children's Hospital Research Institute and the Medical Research Council (MRC) of Canada.

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