title: Changes in oxygenation in mechanically ventilated critically ill patients following hyperbaric treatment.
abstract: BACKGROUND
  Some ventilated intensive care unit (ICU) patients may experience reduced oxygenation following hyperbaric oxygen treatment (HBOT).
  
  
  METHODS
  In a prospective, single-centre, observational study, we documented changes in oxygenation and the need for associated changes in ventilator settings in 25 consecutive, mechanically ventilated ICU patients immediately post-treatment and 1, 2, 3 and 6 hours following 61 HBOT sessions. The primary outcome measure of oxygenation was the ratio of arterial partial pressure of oxygen (P(a)O2) against the level of inspired oxygen (F(i)O2), P(a)O2/F(i)O2.
  
  
  RESULTS
  Following HBOT, the P(a)O2/F(i)O2 ratio decreased by 27% on return to ICU (P < 0.001, 95% confidence intervals (CI) 20.6 to 34.2); 22% at 1 hour post-HBOT (P < 0.001, 95% CI 15.1 to 28.6); and 8% at 2 hours post (P = 0.03, 95% CI 0.8 to 14.4). The ratio showed no significant differences from pre-HBOT at 3 and 6 hours post-HBOT. P(a)O2/F(i)O2 ratio changes necessitated adjustments to ventilation parameters upon return to ICU following 30 of 61 HBOT sessions in 17 out of the 25 patients. The most common ventilation parameter altered was F(i)O2 (n = 20), increased by a mean of +0.17 (95% CI 0.11 to 0.23) above baseline for two hours following HBOT.
  
  
  CONCLUSIONS
  Following HBOT, oxygenation is reduced in a majority of mechanically ventilated ICU patients and requires temporary alterations to mechanical ventilation settings. Further study to identify predictive characteristics and to determine causation for those at risk of needing ventilation alterations is required.
authors.affiliation: Hyperbaric Unit, Alfred Hospital, Melbourne, Australia. g.bingham@alfred.org.au
authors.forename: Gordon
authors.initials: G
authors.lastname: Bingham
authors.forename: Ian
authors.initials: I
authors.lastname: Millar
authors.forename: Susan
authors.initials: S
authors.lastname: Koch
authors.forename: Eldho
authors.initials: E
authors.lastname: Paul
authors.forename: Dinesh
authors.initials: D
authors.lastname: Varma
authors.forename: David
authors.initials: D
authors.lastname: Pilcher
mesh_terms: D000328:Adult; D000368:Aged; D019069:Cell Respiration; D016001:Confidence Intervals; D016638:Critical Illness / Q000628:therapy*; D005260:Female; D006801:Humans; D006931:Hyperbaric Oxygenation / Q000379:methods*; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology*; D010313:Partial Pressure; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000379:methods* / Q000592:standards; D013997:Time Factors
chemical_list: D010100:Oxygen