title: Resistance and reactance in oscillation lung function reflect basal lung function and bronchial hyperresponsiveness respectively.
abstract: OBJECTIVE
  Currently there are few data available regarding the use of impulse oscillometry parameters to assess airflow obstruction during standardized methacholine challenge testing.
  
  
  METHODS
  Methacholine challenge tests were performed using impulse oscillometry and conventional spirometry in 64 healthy and 39 asthmatic children, in order to determine airway resistance (R) and reactance (X) at frequencies of 5-35 Hz, as well as FEV(1).
  
  
  RESULTS
  Baseline R and X were significantly different between the healthy and asthmatic children, with the most discriminating parameter being resistance at 5 Hz (R5). In asthmatic children BHR was well demonstrated by FEV(1), X5 and X10, but not by R5. However, when the actual R5 values obtained in this study were compared with the predicted values, there appeared to be differences in the lung function measures that corresponded to varying methacholine concentrations. In addition, the PC20_FEV(1) and PC70_X5 were significantly more sensitive than other parameters for methacholine challenge testing.
  
  
  CONCLUSIONS
  Measuring resistance at 5 Hz using impulse oscillometry facilitates significant differentiation of baseline lung function between asthmatic and healthy children. Additionally, X may be a suitable replacement for PC20 in methacholine challenge testing.
authors.affiliation: Department of Pediatrics, CHA University School of Medicine, Seongnam, Korea.
authors.forename: Hyeong Yoon
authors.initials: HY
authors.lastname: Kim
authors.forename: Yun Ho
authors.initials: YH
authors.lastname: Shin
authors.forename: Da Woon
authors.initials: DW
authors.lastname: Jung
authors.forename: Hye Mi
authors.initials: HM
authors.lastname: Jee
authors.forename: Hye Won
authors.initials: HW
authors.lastname: Park
authors.forename: Man Yong
authors.initials: MY
authors.lastname: Han
mesh_terms: D000403:Airway Resistance / Q000502:physiology*; D001249:Asthma / Q000139:chemically induced / Q000503:physiopathology*; D016535:Bronchial Hyperreactivity / Q000139:chemically induced / Q000503:physiopathology*; D016085:Bronchoconstrictor Agents / Q000009:adverse effects; D016022:Case-Control Studies; D002648:Child; D004305:Dose-Response Relationship, Drug; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D016210:Methacholine Chloride / Q000009:adverse effects; D009991:Oscillometry; D013147:Spirometry
chemical_list: D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride