title: Randomized controlled trial of high concentration oxygen in suspected community-acquired pneumonia.
abstract: OBJECTIVE
  To determine whether high concentration oxygen increases the PaCO(2) in the treatment of community-acquired pneumonia.
  
  
  METHODS
  Randomized controlled clinical trial in which patients received high concentration oxygen (8 L/min via medium concentration mask) or titrated oxygen (to achieve oxygen saturations between 93 and 95%) for 60 minutes. Transcutaneous CO(2) (PtCO(2)) was measured at 0, 20, 40 and 60 minutes.
  
  
  METHODS
  The Emergency Departments at Wellington, Hutt and Kenepuru Hospitals.
  
  
  METHODS
  150 patients with suspected community-acquired pneumonia presenting to the Emergency Department. Patients with chronic obstructive pulmonary disease (COPD) or disorders associated with hypercapnic respiratory failure were excluded.
  
  
  METHODS
  The primary outcome variable was the proportion of patients with a rise in PtCO(2) ≥4 mmHg at 60 minutes. Secondary outcome variables included the proportion of patients with a rise in PtCO(2) ≥8 mmHg at 60 minutes.
  
  
  RESULTS
  The proportion of patients with a rise in PtCO(2) ≥4 mmHg at 60 minutes was greater in the high concentration oxygen group, 36/72 (50.0%) vs 11/75 (14.7%), relative risk (RR) 3.4 (95% CI 1.9 to 6.2), P < 0.001. The high concentration group had a greater proportion of patients with a rise in PtCO(2) ≥8 mmHg, 11/72 (15.3%) vs 2/75 (2.7%), RR 5.7 (95% CI 1.3 to 25.0), P = 0.007. Amongst the 74 patients with radiological confirmation of pneumonia, the high concentration group had a greater proportion with a rise in PtCO(2) ≥4 mmHg, 20/35 (57.1%) vs 5/39 (12.8%), RR 4.5 (95% CI 1.9 to 10.6) P < 0.001.
  
  
  CONCLUSIONS
  We conclude that high concentration oxygen therapy increases the PtCO(2) in patients presenting with suspected community-acquired pneumonia. This suggests that the potential increase in PaCO(2) with high concentration oxygen therapy is not limited to COPD, but may also occur in other respiratory disorders with abnormal gas exchange.
authors.affiliation: Medical Research Institute of New Zealand, Wellington 6242,  New Zealand.
authors.forename: Meme
authors.initials: M
authors.lastname: Wijesinghe
authors.forename: Kyle
authors.initials: K
authors.lastname: Perrin
authors.forename: Bridget
authors.initials: B
authors.lastname: Healy
authors.forename: Mark
authors.initials: M
authors.lastname: Weatherall
authors.forename: Richard
authors.initials: R
authors.lastname: Beasley
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001785:Blood Gas Monitoring, Transcutaneous / Q000379:methods; D002245:Carbon Dioxide / Q000097:blood*; D017714:Community-Acquired Infections / Q000175:diagnosis / Q000628:therapy*; D004636:Emergency Service, Hospital; D004638:Emergency Treatment / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009520:New Zealand; D010101:Oxygen Consumption / Q000502:physiology*; D010102:Oxygen Inhalation Therapy / Q000379:methods*; D010313:Partial Pressure; D011014:Pneumonia / Q000175:diagnosis / Q000628:therapy*; D018570:Risk Assessment; D012720:Severity of Illness Index; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide