Korean J Asthma Allergy Clin Immunol.  2005 Jun;25(2):130-136.

Clinical Usefulness of Impulse Oscillometry in Estimation of the Reversibility of Airway Obstruction in Adult Asthmatics

Abstract

BACKGROUND
Although spirometry is the gold standard, it is not feasible to determine airway reversbility in normal or mild obstructive asthmatics. Impulse oscillometry (IOS) is a method to measure airway resistance over a wide range of frequency without active cooperation. This study evaluates IOS in estimation of airway reversibility in adult asthmatics. METHOD: We studied 142 patients with mild to moderate asthma and 27 with non-asthmatics who had respiratory symptoms. Among 142 asthma patients, reversibility of airway obstruction was confirmed by spirometry in 68 patients (FEV1 Rev+ ; mean FEV1 81.4+/-14.0%) and the remaining 74 patients who did not meet the FEV1 criteria of reversibility were diagnosed as asthma by methacholine challenge test or sputum eosinophilia (Mch/Eos+; mean FEV1 88.1+/-12.7%) Measurement of FEV1, resistance and reactance at various frequencies were performed before and after inhalation of beta2 bronchodilator in all groups. RESULT: When the FEV1% predicted and IOS parameters were measured in each group, R5 (airway resistance at 5 Hz)% was the parameter that showed the largest difference among groups. The baseline predicted values of FEV1% and R5% were associated in FEV1 Rev+ patients (r=-0.448, P<.01), but not in Mch/Eos+ patients (r=-0.211, P=.07) and non-asthmatics (r=-0.271, P=.172). Changes of R5 after inhalation of beta2 bronchodilator was higher in Mch/Eos+ patients than in non-asthmatics. (-0.120+/-0.149 kPa/L/ sec vs. -0.042+/-0.041 kPa/L/sec, P<.01). We set the R5 criteria of reversibility using the changes of absolute units as the mean+/-2 SD changes in non-asthmatics (-0.123 kPas/L/sec). 37.8% of Mch/Eos+ patients met the R5 reversibility criteria. If Mch/Eos+ patients were stratified by the baseline value of R5%, 58.1% of the patients with increased baseline R5% (>100%) met the R5 reversibility criteria. CONCLUSION: We concluded that IOS parameters can be a supplementary tool in the estimation of airway reversibility in adult asthmatics.

MeSH Terms

Adult*
Airway Obstruction*
Airway Resistance
Asthma
Eosinophilia
Humans
Inhalation
Methacholine Chloride
Oscillometry*
Spirometry
Sputum
Methacholine Chloride