Chest
Volume 111, Issue 6, June 1997, Pages 1519-1525
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Clinical Investigations: Pulmonary Function
Measurement of Respiratory Resistance in the Emergency Department: Feasibility in Young Children With Acute Asthma

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Objectives

To assess, in acutely ill asthmatic children, the feasibility of obtaining reproducible measurements of two independent lung function tests, namely spirometry and respiratory resistance, using the forced oscillation technique (Rfo).

Design/setting

A prospective observational study of 150 previously untrained children, aged 2 to 17 years, treated for acute asthma in a tertiary-care pediatric emergency department.

Measurements

Following a standardized physical examination, three measurements of respiratory resistance by forced oscillation were attempted at 8 Hz (Rfo8) and at 16 Hz (Rfo16), followed by spirometry, all using the same instrument (Custo Vit R; Custo Med; Munich, Germany).

Results

On the initial assessment, 98 (65%) children, aged 2 to 17 years, were able to reproducibly perform the Rfo8 measurement, 77 (51%) were able to reproducibly perform the Rfo16 measurement, while only 65 (43%) subjects managed to reliably perform spirometry. A notable proportion of preschool-aged children cooperated with the Rfo8 technique: 19% of 3-year-olds, 40% of 4-year-olds, and 83% of 5-year-olds. The superior success rate with Rfo8 as compared with spirometry was seen in all age groups but was most striking both in preschoolers (relative risk [RR] = 10.5; 95% confidence interval [CI], 8.0 to 13.8) and in children aged 6 to 9 years (RR=1.28; 95% CI, 1.18 to 1.39). Rfo8 values correlated significantly with clinical markers of asthma severity such as respiratory rate (r=0.38) and heart rate (r=0.23) as well as with FEV1 values (r2=0.73).

Conclusions

This study demonstrates the feasibility of obtaining reproducible measurements of respiratory resistance in a notable proportion of untrained, acutely ill, asthmatic children. The forced oscillation technique appears as an attractive alternative to objectively assess lung function in children too young or too ill to cooperate with spirometry.

Section snippets

Design

We conducted a cross-sectional study of children aged 2 to 17 years presenting with an asthma exacerbation to the ED of the Montreal Children's Hospital from April to November 1991. 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.

Subjects

Patients were eligible to participate if they had a clinical diagnosis of asthma confirmed by an emergency physician in accordance with the criteria of

Results

Of the 208 patients approached, 44 children were excluded because of the following: (1) the inability to perform the second assessment before discharge in 14 children, all of whom cooperated with Rfo; (2) exclusion criteria in 19 patients; and (3) the previous participation in this study of 11 subjects. The participation rate was 92% (150 subjects) for the remaining 164 eligible patients (Table 1). The median percent height-adjusted FEV1 and Rfo8 values22 were indicative of moderate obstruction

Discussion

Our study demonstrates that the technique of forced oscillation can be successfully used to measure respiratory resistance in previously untrained preschool children, aged 3 years and older, with an asthma exacerbation. In children aged 4 and 5 years, we observed the noticeable success rates of 40% and 83%, respectively, with the Rfo8 measurement, but only 0% and 17%, respectively, with spirometry. The high level of cooperation for Rfo8 was sustained in the 6- to 9-year-olds (76%) and the

Conclusion

With a substantial proportion of children aged 3 years or older cooperating reproducibly with the measurement of respiratory resistance by forced oscillation at 8 Hz, this technique is advantageous for objectively studying preschool-aged children in whom spirometry can seldom be reliably performed. Moreover, the Rfo8 allows the safe and objective evaluation of a significant proportion of the schoolaged patients who cannot reproducibly perform spirometry during an asthma exacerbation.

ACKNOWLEDGMENTS

We are indebted to Jacques Lauzon, BSc(N), for his diligent technical assistance and data collection; to Dr. David McGillivray, Director of the ED of the Montreal Children's Hospital, and to the ED medical and nursing staff for their collaboration.

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