title: Oxygen therapy for acute myocardial infarction.
abstract: BACKGROUND
  Oxygen (O₂) is widely used in people with acute myocardial infarction (AMI) although it has been suggested it may do more harm than good. Previous systematic reviews have concluded that there was insufficient evidence to know whether oxygen reduced, increased or had no effect on heart ischaemia or infarct size, as did our original Cochrane review on this topic in 2010. The wide dissemination of the lack of evidence to support this widely-used intervention since 2010 may stimulate the needed trials of oxygen therapy, and it is therefore important that this review is updated regularly.
  
  
  OBJECTIVE
  To review the evidence from randomised controlled trials to establish whether routine use of inhaled oxygen in acute myocardial infarction (AMI) improves patient-centred outcomes, in particular pain and death.
  
  
  METHODS
  The following bibliographic databases were searched last in July 2012: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library), MEDLINE (OVID), EMBASE (OVID), CINAHL (EBSCO) and Web of Science (ISI). LILACS (Latin American and Caribbean Health Sciences Literature) and PASCAL were last searched in May 2013. We also contacted experts to identify any studies. We applied no language restrictions.
  
  
  METHODS
  Randomised controlled trials of people with suspected or proven AMI (ST-segment elevation myocardial infarction (STEMI) or non-STEMI), less than 24 hours after onset, in which the intervention was inhaled oxygen (at normal pressure) compared to air and regardless of cotherapies provided these were the same in both arms of the trial.
  
  
  METHODS
  Two authors independently reviewed the titles and abstracts of identified studies to see if they met the inclusion criteria, and independently undertook the data extraction. The quality of studies and the risk of bias were assessed according to guidance in the Cochrane Handbook. The primary outcomes were death, pain and complications. The measure of effect used was the risk ratio (RR) with a 95% confidence interval (CI).
  
  
  RESULTS
  The updated search identified one new trial. In total, four trials involving 430 participants were included and 17 deaths occurred. The pooled RR of death was 2.05 (95% CI 0.75 to 5.58) in an intention-to-treat analysis and 2.11 (95% CI 0.78 to 5.68) in participants with confirmed AMI. While suggestive of harm, the small number of deaths recorded means that this could be a chance occurrence. Pain was measured by analgesic use. The pooled RR for the use of analgesics was 0.97 (95% CI 0.78 to 1.20).
  
  
  CONCLUSIONS
  There is no conclusive evidence from randomised controlled trials to support the routine use of inhaled oxygen in people with AMI. A definitive randomised controlled trial is urgently required, given the mismatch between trial evidence suggestive of possible harm from routine oxygen use and recommendations for its use in clinical practice guidelines.
authors: Department of Cardiology & CASP Spain, Hospital General Universitario de Alicante, Pintor Baeza 12, Alicante, Alicante, Spain, 03010.
authors: Juan B
authors: JB
authors: Cabello
authors: Amanda
authors: A
authors: Burls
authors: José I
authors: JI
authors: Emparanza
authors: Susan
authors: S
authors: Bayliss
authors: Tom
authors: T
authors: Quinn
mesh_terms: D000388:Air; D000700:Analgesics / Q000627:therapeutic use; D006801:Humans; D009203:Myocardial Infarction / Q000401:mortality / Q000628:therapy*; D010102:Oxygen Inhalation Therapy / Q000009:adverse effects / Q000401:mortality; D016032:Randomized Controlled Trials as Topic
chemical_list: D000700:Analgesics