title: Using venous blood gas analysis in the assessment of COPD exacerbations: a prospective cohort study.
abstract: BACKGROUND
  Identifying acute hypercapnic respiratory failure is crucial in the initial management of acute exacerbations of COPD. Guidelines recommend obtaining arterial blood samples but these are more difficult to obtain than venous. We assessed whether blood gas values derived from venous blood could replace arterial at initial assessment.
  
  
  METHODS
  Patients requiring hospital treatment for an exacerbation of COPD had paired arterial and venous samples taken. Bland-Altman analyses were performed to assess agreement between arterial and venous pH, CO2 and HCO3-. The relationship between SpO2 and SaO2 was assessed. The number of attempts and pain scores for each sample were measured.
  
  
  RESULTS
  234 patients were studied. There was good agreement between arterial and venous measures of pH and HC)3- (mean difference 0.03 and -0.04, limits of agreement -0.05 to 0.11 and -2.90 to 2.82, respectively), and between SaO2 and SpO2 (in patients with an SpO2 of >80%). Arterial sampling required more attempts and was more painful than venous (mean pain score 4 (IQR 2-5) and 1 (IQR 0-2), respectively, p<0.001).
  
  
  CONCLUSIONS
  Arterial sampling is more difficult and more painful than venous sampling. There is good agreement between pH and HCO3- values derived from venous and arterial blood, and between pulse oximetry and arterial blood gas oxygen saturations. These agreements could allow the initial assessment of COPD exacerbations to be based on venous blood gas analysis and pulse oximetry, simplifying the care pathway and improving the patient experience.
authors.affiliation: Division of Epidemiology, University of Nottingham, Nottingham, UK.
authors.forename: Tricia M
authors.initials: TM
authors.lastname: McKeever
authors.affiliation: Respiratory Research Unit, Division of Respiratory Medicine, University of Nottingham, Nottingham, UK.
authors.forename: Glenn
authors.initials: G
authors.lastname: Hearson
authors.affiliation: Medical Informatics, East Midlands Academic Health Sciences Network, Nottingham, UK.
authors.forename: Gemma
authors.initials: G
authors.lastname: Housley
authors.affiliation: Respiratory Research Unit, Division of Respiratory Medicine, University of Nottingham, Nottingham, UK.
authors.forename: Catherine
authors.initials: C
authors.lastname: Reynolds
authors.affiliation: Respiratory Medicine, Nottingham University Hospital Trust, Nottingham, UK.
authors.forename: William
authors.initials: W
authors.lastname: Kinnear
authors.affiliation: Respiratory Research Unit, Division of Respiratory Medicine, University of Nottingham, Nottingham, UK.
authors.forename: Tim W
authors.initials: TW
authors.lastname: Harrison
authors.affiliation: Emergency Medicine, Joseph Epstein Centre for Emergency Medicine Research, Western Health, St Albans, Victoria, Australia.
authors.forename: Anne-Maree
authors.initials: AM
authors.lastname: Kelly
authors.affiliation: Respiratory Research Unit, Division of Respiratory Medicine, University of Nottingham, Nottingham, UK Medical Informatics, East Midlands Academic Health Sciences Network, Nottingham, UK.
authors.forename: Dominick E
authors.initials: DE
authors.lastname: Shaw
mesh_terms: D000368:Aged; D001784:Blood Gas Analysis / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods*; D010100:Oxygen / Q000097:blood*; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood* / Q000175:diagnosis; D015203:Reproducibility of Results; D014680:Veins
chemical_list: D010100:Oxygen
keywords: COPD Exacerbations