title: Oxygen saturations less than 92% are associated with major adverse events in outpatients with pneumonia: a population-based cohort study.
abstract: BACKGROUND
  patients with hypoxemia (blood oxygen saturation <90%) are usually hospitalized, although validated criteria (eg, the Pneumonia Severity Index [PSI]) suggest outpatient treatment is safe. We sought evidence to support or refute the practice.
  
  
  METHODS
  all patients in Edmonton, Alberta, Canada with pneumonia assessed at any of 7 emergency departments (EDs) and then discharged were enrolled in a population-based cohort study. The independent variable of interest was oxygen saturation; the outcome was the composite endpoint of 30-day mortality or hospitalization.
  
  
  RESULTS
  the study evaluated 2923 individuals with pneumonia who were treated as outpatients at any of 7 EDs. The patients' mean age (standard deviation [SD])was 52 (20) years; 47% were women; 74% were low risk (PSI Class I-II). The mean blood oxygen saturation (SD) was 95% (3%); 126 patients (4%) had blood oxygen saturations <90%, and 201 patients (7%) had blood oxygen saturations of 90%-92%. Over 30 days, 39 patients (1%) died and 252 (9%) reached the composite endpoint. Compared with patients with higher blood oxygen saturations, those discharged with saturations <90% had significantly (P < .001) higher rates of 30-day mortality (7 [6%] vs 32 [1%]), hospitalization (23 [18%] vs 201 [7%]), and composite endpoints (27 [21%] vs 225 [8%]). Blood oxygen saturation <90% was independently associated with 30-day mortality or hospitalization (adjusted odds ratio (OR), 1.7; 95% confidence interval (CI) 1.1-2.8; P = .032). If the saturation threshold for hospitalization was 92%, then there was no association with adverse events (adjusted OR 1.1, 95% CI 0.8-1.7, P = .48). Raising the admission threshold to 92% entails 1 additional hospitalization for every 14 patients discharged.
  
  
  CONCLUSIONS
  among outpatients with pneumonia, oxygen saturations <90% were associated with increased morbidity and mortality. Our results indicate a hospital admission threshold of <92% would be safer and clinically better justified.
authors.affiliation: Department of Medicine, Faculty of Medicine and Dentistry, School of Public Health, University of Alberta, Edmonton, Alberta, Canada. me2.majumdar@ualberta.ca
authors.forename: Sumit R
authors.initials: SR
authors.lastname: Majumdar
authors.forename: Dean T
authors.initials: DT
authors.lastname: Eurich
authors.forename: John-Michael
authors.initials: JM
authors.lastname: Gamble
authors.forename: A
authors.initials: A
authors.lastname: Senthilselvan
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Marrie
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000416:Alberta / Q000453:epidemiology; D000553:Ambulatory Care / Q000379:methods*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000188:drug therapy / Q000453:epidemiology* / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D010045:Outpatients; D010100:Oxygen / Q000097:blood / Q000627:therapeutic use*; D011014:Pneumonia / Q000188:drug therapy / Q000453:epidemiology* / Q000401:mortality*; D016896:Treatment Outcome
chemical_list: D010100:Oxygen