title: Conservative oxygen therapy in mechanically ventilated patients following cardiac arrest: A retrospective nested cohort study.
abstract: BACKGROUND
  In mechanically ventilated (MV) cardiac arrest (CA) survivors admitted to the intensive care unit (ICU) avoidance of hypoxia is considered crucial. However, avoidance of hyperoxia may also be important. A conservative approach to oxygen therapy may reduce exposure to both.
  
  
  METHODS
  We evaluated the introduction of conservative oxygen therapy (target SpO2 88-92% using the lowest FiO2) during MV for resuscitated CA patients admitted to the ICU.
  
  
  RESULTS
  We studied 912 arterial blood gas (ABG) datasets: 448 ABGs from 50 'conventional' and 464 ABGs from 50 'conservative' oxygen therapy patients. Compared to the conventional group, conservative group patients had significantly lower PaO2 values and FiO2 exposure (p<0.001, respectively); more received MV in a spontaneous ventilation mode (18% vs 2%; p=0.001) and more were exposed to a FiO2 of 0.21 (19 vs 0 patients, p=0.001). Additionally, according to mean PaO2, more conservative group patients were classified as normoxaemic (36 vs 16 patients, p<0.01) and fewer as hyperoxaemic (14 vs 33 patients, p<0.01). Finally, ICU length of stay was significantly shorter for conservative group patients (p=0.04). There was no difference in the proportion of survivors discharged from hospital with good neurological outcome (14/23 vs 12/22 patients, p=0.67).
  
  
  CONCLUSIONS
  Our findings provide preliminary support for the feasibility and physiological safety of conservative oxygen therapy in patients admitted to ICU for MV support after cardiac arrest (Trial registration, NCT01684124).
authors.affiliation: Department of Intensive Care, Austin Hospital, Melbourne, Australia; School of Nursing and Midwifery, Faculty of Health, Deakin University, Melbourne, Australia; ANZIC-RC, Monash University, Victoria, Australia. Electronic address: glenn.eastwood@austin.org.au.
authors.forename: Glenn M
authors.initials: GM
authors.lastname: Eastwood
authors.affiliation: Department of Intensive Care, Austin Hospital, Melbourne, Australia; Department of Anesthesiology and Intensive Care, Osaka University Graduate School of Medicine, Suita, Osaka, Japan. Electronic address: aiko.tanaka@austin.org.au.
authors.forename: Aiko
authors.initials: A
authors.lastname: Tanaka
authors.affiliation: Department of Intensive Care, Austin Hospital, Melbourne, Australia. Electronic address: edve84@gmail.com.
authors.forename: Emilo Daniel Valenzuela
authors.initials: ED
authors.lastname: Espinoza
authors.affiliation: Department of Intensive Care, Austin Hospital, Melbourne, Australia. Electronic address: leah.peck@austin.org.au.
authors.forename: Leah
authors.initials: L
authors.lastname: Peck
authors.affiliation: Department of Intensive Care, Austin Hospital, Melbourne, Australia. Electronic address: helen.young@austin.org.au.
authors.forename: Helen
authors.initials: H
authors.lastname: Young
authors.affiliation: Department of Intensive Care, Austin Hospital, Melbourne, Australia; ANZIC-RC, Monash University, Victoria, Australia; Section of Anaesthesia and Intensive Care Medicine, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden. Electronic address: johan.martensson@austin.org.au.
authors.forename: Johan
authors.initials: J
authors.lastname: Mårtensson
authors.affiliation: Department of Intensive Care, Austin Hospital, Melbourne, Australia; Department of Nephrology, West China Medical School, West China Hospital, China. Electronic address: zhanglinglzy@163.com.
authors.forename: Ling
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Intensive Care, Austin Hospital, Melbourne, Australia; Department of Anesthesiology and Intensive Care, Osaka University Graduate School of Medicine, Suita, Osaka, Japan. Electronic address: neil.glassford@austin.org.au.
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Glassford
authors.affiliation: Department of Intensive Care, Austin Hospital, Melbourne, Australia. Electronic address: frank.yfh@gmail.com.
authors.forename: Yu-Feng Frank
authors.initials: YF
authors.lastname: Hsiao
authors.affiliation: Department of Nephrology, West China Medical School, West China Hospital, China. Electronic address: Suzuki-s@mtc.biglobe.ne.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Suzuki
authors.affiliation: Department of Intensive Care, Austin Hospital, Melbourne, Australia; ANZIC-RC, Monash University, Victoria, Australia. Electronic address: rinaldo.bellomo@austin.org.au.
authors.forename: Rinaldo
authors.initials: R
authors.lastname: Bellomo
mesh_terms: D000368:Aged; D015331:Cohort Studies; D000072700:Conservative Treatment; D005260:Female; D006323:Heart Arrest / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010102:Oxygen Inhalation Therapy; D012121:Respiration, Artificial; D012189:Retrospective Studies
keywords: Cardiac arrest; Intensive care; Mechanical ventilation; Mortality; Outcome; Oxygen