title: Prone positioning in hypoxemic respiratory failure: meta-analysis of randomized controlled trials.
abstract: OBJECTIVE
  Prone positioning is used to improve oxygenation in patients with hypoxemic respiratory failure (HRF). However, its role in clinical practice is not yet clearly defined. The aim of this meta-analysis was to assess the effect of prone positioning on relevant clinical outcomes, such as intensive care unit (ICU) and hospital mortality, days of mechanical ventilation, length of stay, incidence of ventilator-associated pneumonia (VAP) and pneumothorax, and associated complications.
  
  
  METHODS
  We used literature search of MEDLINE, Current Contents, and Cochrane Central Register of Controlled Trials. We focused only on randomized controlled trials reporting clinical outcomes in adult patients with HRF. Four trials met our inclusion criteria, including 662 patients randomized to prone ventilation and 609 patients to supine ventilation.
  
  
  RESULTS
  The pooled odds ratio (OR) for the ICU mortality in the intention-to-treat analysis was 0.97 (95% confidence interval [CI], 0.77-1.22), for the comparison between prone and supine ventilated patients. Interestingly, the pooled OR for the ICU mortality in the selected group of the more severely ill patients favored prone positioning (OR, 0.34; 95% CI, 0.18-0.66). The duration of mechanical ventilation and the incidence of pneumothorax were not different between the 2 groups. The incidence of VAP was lower but not statistically significant in patients treated with prone positioning (OR, 0.81; 95% CI, 0.61-1.10). However, prone positioning was associated with a higher risk of pressure sores (OR, 1.49; 95% CI, 1.17-1.89) and a trend for more complications related to the endotracheal tube (OR, 1.30; 95% CI, 0.94-1.80).
  
  
  CONCLUSIONS
  Despite the inherent limitations of the meta-analytic approach, it seems that prone positioning has no discernible effect on mortality in patients with HRF. It may decrease the incidence of VAP at the expense of more pressure sores and complications related to the endotracheal tube. However, a subgroup of the most severely ill patients may benefit most from this intervention.
authors.affiliation: 2nd Critical Care Department, University of Athens Medical School, Attiko University Hospital, Athens 12462, Greece. petkop@ath.forthnet.gr
authors.forename: Petros
authors.initials: P
authors.lastname: Kopterides
authors.forename: Ilias I
authors.initials: II
authors.lastname: Siempos
authors.forename: Apostolos
authors.initials: A
authors.lastname: Armaganidis
mesh_terms: D000328:Adult; D003422:Critical Care / Q000379:methods*; D055317:Evidence-Based Practice; D017052:Hospital Mortality; D006801:Humans; D000860:Hypoxia / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D015994:Incidence; D007902:Length of Stay; D018579:Patient Selection; D053717:Pneumonia, Ventilator-Associated / Q000453:epidemiology / Q000209:etiology; D011030:Pneumothorax / Q000453:epidemiology / Q000209:etiology; D003668:Pressure Ulcer / Q000453:epidemiology / Q000209:etiology; D016684:Prone Position / Q000502:physiology; D016032:Randomized Controlled Trials as Topic; D012107:Research Design; D012121:Respiration, Artificial / Q000009:adverse effects / Q000379:methods; D012128:Respiratory Distress Syndrome / Q000401:mortality / Q000628:therapy; D012131:Respiratory Insufficiency / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D015656:Respiratory Mechanics; D012449:Safety; D016683:Supine Position / Q000502:physiology; D013990:Tidal Volume; D016896:Treatment Outcome