Association between respiratory impedance measured by forced oscillation technique and exacerbations in patients with COPD

International Journal of Chronic Obstructive Pulmonary Disease, Dec 2017

Association between respiratory impedance measured by forced oscillation technique and exacerbations in patients with COPD Hitomi Yamagami, Akihiko Tanaka, Yasunari Kishino, Hatsuko Mikuni, Tomoko Kawahara, Shin Ohta, Mayumi Yamamoto, Shintaro Suzuki, Tsukasa Ohnishi, Hironori Sagara Division of Respiratory Medicine and Allergology, Department of Medicine, School of Medicine, Showa University, Tokyo, Japan Background: It is well known that increased airflow limitation as measured by spirometry is associated with the risk of exacerbation in patients with COPD. The forced oscillation technique (FOT) is a noninvasive method used to assess respiratory impedance (resistance and reactance) with minimal patient cooperation required. The clinical utility of the FOT in assessing the risk of exacerbations of COPD is yet to be determined. We examined the relationship between respiratory impedance as measured by FOT and exacerbations in patients with COPD. Materials and methods: Among 310 patients with COPD (Global Initiative for Chronic Obstructive Lung Disease stages I–IV) who presented at the outpatient clinic of the Showa University Hospital from September 2014 through January 2015, 119 were collected and assigned into 2 groups according to their history of exacerbation: exacerbators and nonexacerbators. Respiratory resistance components and respiratory reactance components, as measured by FOT, were compared between the two groups. Results: Exacerbators were significantly older and had a higher white blood cell count than nonexacerbators. Resistance at 20 Hz, reactance at 5 Hz (X5), resonant frequency (Fres), and area of low reactance (ALX) differed significantly between the two groups. In addition, among patients with stage II COPD, there were significant differences in X5, Fres, and ALX between the two groups despite no significant differences in respiratory function as assessed by spirometry. Finally, receiver operating characteristic curve analysis revealed that the reactance components rather than the resistance components were associated with the risk of exacerbation. Conclusion: There were significant differences in respiratory impedance between exacerbators and nonexacerbators in patients with moderate COPD. FOT is a promising tool for assessing future exacerbations in patients with COPD. Keywords: forced oscillation technique, respiratory system resistance and reactance, spirometry

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Association between respiratory impedance measured by forced oscillation technique and exacerbations in patients with COPD

International Journal of COPD association between respiratory impedance measured by forced oscillation technique and exacerbations in patients with COPD 0 Division of r espiratory Medicine and allergology, Department of Medicine, school of Medicine, showa University , Tokyo , Japan froedm lsonue lnodow rsnope PowerdbyTCPDF(ww.tcpdf.org) hitomi Yamagami akihiko Tanaka Yasunari Kishino hatsuko Mikuni Tomoko Kawahara shin Ohta Mayumi Yamamoto shintaro suzuki Tsukasa Ohnishi hironori sagara Background: It is well known that increased airflow limitation as measured by spirometry is associated with the risk of exacerbation in patients with COPD. The forced oscillation technique (FOT) is a noninvasive method used to assess respiratory impedance (resistance and reactance) with minimal patient cooperation required. The clinical utility of the FOT in assessing the risk of exacerbations of COPD is yet to be determined. We examined the relationship between respiratory impedance as measured by FOT and exacerbations in patients with COPD. Materials and methods: Among 310 patients with COPD (Global Initiative for Chronic Obstructive Lung Disease stages I-IV) who presented at the outpatient clinic of the Showa University Hospital from September 2014 through January 2015, 119 were collected and assigned into 2 groups according to their history of exacerbation: exacerbators and nonexacerbators. Respiratory resistance components and respiratory reactance components, as measured by FOT, were compared between the two groups. Results: Exacerbators were significantly older and had a higher white blood cell count than nonexacerbators. Resistance at 20 Hz, reactance at 5 Hz (X5), resonant frequency (Fres), and area of low reactance (ALX) differed significantly between the two groups. In addition, among patients with stage II COPD, there were significant differences in X5, Fres, and ALX between the two groups despite no significant differences in respiratory function as assessed by spirometry. Finally, receiver operating characteristic curve analysis revealed that the reactance components rather than the resistance components were associated with the risk of exacerbation. Conclusion: There were significant differences in respiratory impedance between exacerbators and nonexacerbators in patients with moderate COPD. FOT is a promising tool for assessing future exacerbations in patients with COPD. - sae roF e s i D y r a n o m l u P e v it c u tr s b O c i n o r h C f o l a n r u o J l a n o it a n tr e n I 8 1 0 2 l u J 2 1 n o 7 0 2 . 6 4 . 9 5 . 7 3 y b / m o c . s s e r p e v o d . w w w / / : s p t th .y Among clinical parameters, a history of frequent exacerbations in the previous year is the most important and independent predictor of exacerbation in the following year.9 Identification of risk factors for exacerbation of COPD is clinically important because it enables adequate precautionary measures, such as pharmacologic therapy and vaccine, in patients predisposed to COPD exacerbation. The forced oscillation technique (FOT) is a noninvasive procedure that measures lung mechanics using sinusoidal sound waves at two or three different frequencies simultaneously. FOT parameters of respiratory system resistance (Rrs) and respiratory system reactance (Xrs) were measured by the application of a sine wave of airflow to the mouth at the resonant frequency of the respiratory system according to the principle established by Fisher et al.10 Rrs components include the resistance at 5 Hz (R5), the resistance at 20 Hz (R20), and the difference between R5 and R20 (R5−R20). Xrs components include the reactance at 5 Hz (X5), the froedm lsonue tdhifefreerseonncaesntbfertewqeueennciyns(pFirreasto),raynadntdheexapreiraatoofrlyowXrrsea(ΔctXanrsc)e, lnodoadw lrsnopea t(iAoLnaXl )p.uFlOmTonraerpyrefusenncttsioannteaslttesrbneactiavuesemoofdiatlsitsyentosictiovnitvyeninsae roF detecting peripheral airway obstruction. In addition, it can be ise performed independent of the patient’s efforts with minimal ryD need for their cooperation.11,12 Therefore, FOT can be used ona in elderly patients and those with physical and cognitive luPm limitations, and it would be helpful for these patients if FOT itve can detect exacerbations of COPD. trcsu The utility of FOT has been reported most frequently in bO relation to asthma and COPD. Respiratory impedance (Rrs icon and Xrs) in patients with COPD is generally correlated with lfrhoaC (GGloObLaDl)Instiatigaitnigv,eclfaosrsiCfihedroanciccorOdbinsgtrtuoctthiveedeLgurenegoDfaiisrewaasey n r u o J l a n o it a n tr e n I obstruction.13 Moreover, FOT can detect the pharmacologic effects of bronchodilators on small airways in patients with COPD despite an absence of change in forced expiratory volume in 1 second (FEV1).14 ΔXrs, particularly ΔX5, can be used for discrimination between COPD and asthma15,16 or for detection of expiratory flow limitation (EFL) that indicates dynamic hyperinflation in COPD.17,18 In a p (...truncated)


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Hitomi Yamagami, Akihiko Tanaka, Yasunari Kishino, Hatsuko Mikuni, Tomoko Kawahara, Shin Ohta, Mayumi Yamamoto, Shintaro Suzuki, Tsukasa Ohnishi, Hironori Sagara. Association between respiratory impedance measured by forced oscillation technique and exacerbations in patients with COPD, International Journal of Chronic Obstructive Pulmonary Disease, 2017, pp. 79-89, DOI: 10.2147/COPD.S146669