title: Relationship between peripheral airway function and patient-reported outcomes in COPD: a cross-sectional study.
abstract: BACKGROUND
  Health status, dyspnea and psychological status are important clinical outcomes in chronic obstructive pulmonary disease (COPD). However, forced expiratory volume in one second (FEV1) measured by spirometry, the standard measurement of airflow limitation, has only a weak relationship with these outcomes in COPD. Recently, in addition to spirometry, impulse oscillometry (IOS) measuring lung resistance (R) and reactance (X) is increasingly being used to assess pulmonary functional impairment.
  
  
  METHODS
  We aimed to identify relationships between IOS measurements and patient-reported outcomes in 65 outpatients with stable COPD. We performed pulmonary function testing, IOS, high-resolution computed tomography (CT), and assessment of health status using the St. George's Respiratory Questionnaire (SGRQ), dyspnea using the Medical Research Council (MRC) scale and psychological status using the Hospital Anxiety and Depression Scale (HADS). We then investigated the relationships between these parameters. For the IOS measurements, we used lung resistance at 5 and 20 Hz (R5 and R20, respectively) and reactance at 5 Hz (X5). Because R5 and R20 are regarded as reflecting total and proximal airway resistance, respectively, the fall in resistance from R5 to R20 (R5-R20) was used as a surrogate for the resistance of peripheral airways. X5 was also considered to represent peripheral airway abnormalities.
  
  
  RESULTS
  R5-R20 and X5 were significantly correlated with the SGRQ and the MRC. These correlation coefficients were greater than when using other objective measurements of pulmonary function, R20 on the IOS and CT instead of R5-R20 and X5. Multiple regression analyses showed that R5-R20 or X5 most significantly accounted for the SGRQ and MRC scores.
  
  
  CONCLUSIONS
  IOS measurements, especially indices of peripheral airway function, are significantly correlated with health status and dyspnea in patients with COPD. Therefore, in addition to its simplicity and non-invasiveness, IOS may be a useful clinical tool not only for detecting pulmonary functional impairment, but also to some extent at least estimating the patient's quality of daily life and well-being.
authors.affiliation: Department of Respiratory Care and Sleep Control Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Akane
authors.initials: A
authors.lastname: Haruna
authors.forename: Toru
authors.initials: T
authors.lastname: Oga
authors.forename: Shigeo
authors.initials: S
authors.lastname: Muro
authors.forename: Tadashi
authors.initials: T
authors.lastname: Ohara
authors.forename: Susumu
authors.initials: S
authors.lastname: Sato
authors.forename: Satoshi
authors.initials: S
authors.lastname: Marumo
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kinose
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Terada
authors.forename: Michiyoshi
authors.initials: M
authors.lastname: Nishioka
authors.forename: Emiko
authors.initials: E
authors.lastname: Ogawa
authors.forename: Yuma
authors.initials: Y
authors.lastname: Hoshino
authors.forename: Toyohiro
authors.initials: T
authors.lastname: Hirai
authors.forename: Kazuo
authors.initials: K
authors.lastname: Chin
authors.forename: Michiaki
authors.initials: M
authors.lastname: Mishima
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001007:Anxiety / Q000523:psychology; D003430:Cross-Sectional Studies; D003863:Depression / Q000523:psychology; D004417:Dyspnea / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000523:psychology; D005541:Forced Expiratory Volume; D006304:Health Status; D006801:Humans; D008170:Lung Compliance; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000523:psychology; D012044:Regression Analysis; D012129:Respiratory Function Tests; D013147:Spirometry; D011795:Surveys and Questionnaires; D014057:Tomography, X-Ray Computed