PT  - JOURNAL ARTICLE
AU  - Hisatoshi Hijikata
AU  - Masaya Takemura
AU  - Norihisa Takeda
AU  - Kensuke Fukumitsu
AU  - Hiroya Ichikawa
AU  - Takamitsu Asano
AU  - Takehiro Uemura
AU  - Osamu Takakuwa
AU  - Hirotsugu Ohkubo
AU  - Ken Maeno
AU  - Yutaka Ito
AU  - Tetsuya Oguri
AU  - Atsushi Nakamura
AU  - Akio Niiimi
TI  - Airway hyperresponsiveness (AHR) of small airways assessed by impulse oscillation (IOS) in adult asthma
AID  - 10.1183/13993003.congress-2015.PA5083
DP  - 2015 Sep 01
TA  - European Respiratory Journal
PG  - PA5083
VI  - 46
IP  - suppl 59
4099  - http://erj.ersjournals.com/content/46/suppl_59/PA5083.short
4100  - http://erj.ersjournals.com/content/46/suppl_59/PA5083.full
SO  - Eur Respir J2015 Sep 01; 46
AB  - Background: Small airways are likely involved in asthma, but whether small airways disease play relevant roles in specific asthma phenotypes is unknown. Only a few studies addressed AHR of small airways by using IOS in adult asthma.Purpose: To investigate AHR of small airways with a use of IOS and its relation to clinical and functional features.Method: Among stable asthmatics referred to our clinic from Aug 2013 to Jan 2015, 19 patients (mean age 44 yrs; 13 males; 7 taking inhaled steroid) who showed AHR to methacholine (Mch) at a prescreening and gave informed consent to the study were enrolled. They underwent IOS followed by spirometry at baseline and after inhalations of saline and doubling Mch concentrations (0.039 to 20 mg/ml) until FEV1 fell by 20%.Result: IOS indices R5 (respiratory resistance at 5 Hz) and R20 (that at 20 Hz) significantly increased after the final Mch dose of each patient. R5, an index of total airways resistance, increased by 88±41% (ΔR5), while R20, that of large airways resistance, changed by 25±21% (ΔR20). We classified patients by the ΔR20/ΔR5 ratio; in patients with the ratio of < 0.7 (peripheral AHR dominant group; n=10), the baseline FEV1/FVC (%), FEV1, FEF25 and FEF25-75 (% pred. for each), and the prevalence of subjects who coughed during Mch test were significantly lower, and the prevalence of smoking history was marginally higher than in patients with the ratio of > 0.7 (central AHR dominant group; n=9). Asthma duration and severity, history of childhood asthma, and exhaled nitric oxide levels did not differ.Conclusion: Asthma phenotype with small airways-dominant AHR likely exist, but larger studies are needed for further exploration.