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The Utility of the Forced Oscillation Technique (FOT) in Assessing Bronchodilator Responsiveness in Patients with Asthma FREE TO VIEW

Michael J. Akerman, MD, FACP; Venkata A. Yalamanchili, MD; Vaidehi Kaza, MD; Jeremy Weedon, MD; Albert E. Heurich, MD; Makito Yaegashi, MD*
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State University of New York, Health Science Center of Brook, Brooklyn, NY


Chest. 2004;126(4_MeetingAbstracts):796S. doi:10.1378/chest.126.4_MeetingAbstracts.796S
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PURPOSE:  To address the utility of the forced oscillation technique (FOT) in assessing bronchodilator responsiveness compared with FEV1 and PEF.

METHODS:  In 126 patients with clinical history of asthma, the following measures were obtained three times each, before and after two doses of pirbuterol 0.2mg inhalation. FOT measures: *the respiratory resistance at 5 Hz (R5) and at 20 Hz (R20), *R5-R20, *the total respiratory resistance (Rrs) *the total respiratory conductance (Grs). Spirometric measures: *FEV1 *peak expiratory flow (PEF) with spirometry. These measures were transformed into dimentionless subject-specific effect-size “d-scores” by dividing them by the estimated pooled within-subject standard deviation.

RESULTS:  Descriptive statistics for mean raw scores, delta scores and d-scores are presented in Table 1Table 1

Descriptive statistics for FOT measurement and FEV1 before and after pirbuterol

MeasureVariableMeanSDMin.Max.p value (vs FEV1)FEV1 (L)Baseline Post-drugΔd1.90 2.10 0.20 1.830.64 0.68 0.25 2.270.50 0.55 -0.73 -6.724.18 4.01 0.96 8.90N/AGrs (L·s-1 kPa-1)Baseline Post-drugΔd1.79 2.18 0.39 2.640.53 0.65 0.43 2.900.93 1.15 -0.74 -4.943.82 4.17 1.68 11.27p=0.0063R5 (kPa·L-1·s)Baseline Post-drugΔd0.78 0.62 -0.16 2.520.25 0.20 0.16 2.440.31 0.27 -0.62 -5.311.60 1.31 0.35 9.55p=0.0095Rrs (kPa·L-1·s)Baseline Post-drugΔd0.60 0.50 -0.10 2.560.16 0.14 0.11 2.660.26 0.24 -0.37 -6.131.08 0.87 0.25 9.08p=0.0102. The mean effect size among these measures were different between measures[omnibus test of difference, p<0.0001]. Post-hoc test analysis indicated that Grs,Rrs,R5 are most sensitive for changing in response to pirputrol inhalation, and that PEF & R5-R20 are least sensitive. [Tukey p<0.0001 in all cases]. The pattern of unadjusted p-values (p < 0.05) suggests three homogeneous sets of measures for sensitivity to change after pirputerol. In descending order of sensitivity they are: Grs, Rrs and R5; FEV1 and R20; and R5-R20 and PEF.

CONCLUSION:  Several forced oscillation measures, namely Grs, Rrs and R5, are very sensitive for detecting bronchodilator response in patients with asthma.

CLINICAL IMPLICATIONS:  Measurement of forced oscillation may be useful to detect bronchodilator response in asthmatic patients.

DISCLOSURE:  M. Yaegashi, None.

Wednesday, October 27, 2004

12:30 PM - 2:00 PM




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