title: Spirometry and impulse oscillometry (IOS) for detection of respiratory abnormalities in metropolitan firefighters.
abstract: OBJECTIVE
  As firefighters are at increased risk of adverse health effects, periodic examination of their respiratory health is important. The objective of this study was to establish whether the use of impulse oscillometry (IOS) reveals respiratory abnormalities in metropolitan firefighters that go undetected during routine respiratory health screening by spirometry and assessment of respiratory symptoms.
  
  
  METHODS
  This was a cross-sectional analysis of spirometry, IOS and questionnaire data from 488 male firefighters. Abnormal spirometry was defined as FEV(1), FEV(1)/FVC and/or FEF(50) below the lower limit of normal. Abnormal IOS was defined as resistance at 5 Hz (R5), frequency dependence of resistance (DeltaR5-R20) and/or reactance area (AX) above the upper limit of normal. Respiratory symptoms, smoking history, exposures and medical history were assessed. Data were analysed using logistic and linear regression models.
  
  
  RESULTS
  The mean age of the firefighters was 43.8 (SD 8.4) years. There were 123 (25%) former smokers and 50 (10%) current smokers. Abnormal spirometry was detected in 12%, abnormal IOS in 9% and respiratory symptoms in 20% of firefighters. Current smoking was associated with all IOS parameters (OR for R5 = 3.1, OR for DeltaR5-R20 = 7.7, OR for AX = 4.3), and with FEF(50) (OR = 9.1), chronic productive cough (OR = 4.0) and breathlessness (OR = 5.4) (P < 0.05 for all). Exposure during firefighting duties was associated with chronic productive cough (OR = 2.6), but not with spirometry or IOS parameters. Interaction terms in the linear regression models indicated associations between smoking and DeltaR5-R20, and also between smoking and AX, in the lowest and second lowest quartiles of spirometry parameters.
  
  
  CONCLUSIONS
  Application of IOS for the assessment of respiratory health in firefighters identified airways dysfunction in some individuals, even when spirometry values were within the normal range and there were no respiratory symptoms.
authors.affiliation: Department of General Practice, School of Population Health & Clinical Practice, The University of Adelaide, Adelaide, South Australia, Australia. tjaarda.schermer@adelaide.edu.au
authors.forename: Tjard
authors.initials: T
authors.lastname: Schermer
authors.forename: Winifred
authors.initials: W
authors.lastname: Malbon
authors.forename: Wendy
authors.initials: W
authors.lastname: Newbury
authors.forename: Christine
authors.initials: C
authors.lastname: Holton
authors.forename: Michael
authors.initials: M
authors.lastname: Smith
authors.forename: Michael
authors.initials: M
authors.lastname: Morgan
authors.forename: Alan
authors.initials: A
authors.lastname: Crockett
mesh_terms: D000328:Adult; D000403:Airway Resistance; D003371:Cough / Q000175:diagnosis; D003430:Cross-Sectional Studies; D042241:Early Diagnosis; D005390:Fires; D006801:Humans; D008171:Lung Diseases / Q000175:diagnosis* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000175:diagnosis* / Q000209:etiology; D009991:Oscillometry / Q000379:methods*; D012907:Smoking / Q000009:adverse effects; D013147:Spirometry / Q000379:methods*