title: Optimization of indirect pressure in order to temporize life-threatening haemorrhage: A simulation study.
abstract: BACKGROUND
  Minimizing haemorrhage using direct pressure is intuitive and widely taught. In contrast, this study examines the use of indirect-pressure, specifically external aortic compression (EAC). Indirect pressure has great potential for temporizing bleeds not amenable to direct tamponade i.e. abdominal-pelvic, junctional, and multi-site trauma. However, it is currently unclear how to optimize this technique.
  
  
  METHODS
  We designed a model of central vessel compression using the Malbrain intra-abdominal pressure monitor and digital weigh scale. Forty participants performed simulated external aortic compression on the ground, on a stretcher mattress, and with and without a backboard.
  
  
  RESULTS
  The greater the rescuer's bodyweight the greater was their mean compression (Pearson's correlation 0.93). Using one-hand, a mean of 28% participant bodyweight (95% CI, 26-30%) could be transmitted at sustainable effort, waist-height, and on a stretcher. A second compressing hand increased the percentage of rescuer bodyweight transmission 10-22% regardless of other factors (i.e. presence/absence or a backboard; rescuer position) (p<0.001). Adding a backboard increased transmission of rescuer bodyweight 7-15% (p<0.001). Lowering the patient from waist-height backboard to the floor increased transmission of rescuer bodyweight 4-9% (p<0.001). Kneeling on the model was the most efficient method and transmitted 11% more weight compared to two-handed maximal compression (p<0.001).
  
  
  CONCLUSIONS
  Efficacy is maximized with larger-weight rescuers who use both hands, position themselves atop victims, and compress on hard surfaces/backboards. Knee compression is most effective and least fatiguing, thus assisting rescuers of lower weight and lesser strength, where no hard surfaces exist (i.e. no available backboard or trauma on soft ground), or when lengthy compression is required (i.e. remote locations). Our work quantifies methods to optimize indirect pressure as a temporizing measure following life-threatening haemorrhage not amenable to direct compression, and while expediting compression devices or definitive treatment.
authors.affiliation: Trauma and Emergency Services, Royal Alexandra Hospital, 10240 Kingsway Avenue NW, Edmonton, Alberta, T5H3V9, Canada. Electronic address: matthew.douma@albertahealthservices.ca.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Douma
authors.affiliation: Shock Trauma Air Rescue Society, Canada; Emergency Services, Edmonton, Alberta Health Services, Canada. Electronic address: dodochartaigh@stars.ca.
authors.forename: Domhnall
authors.initials: D
authors.lastname: O'Dochartaigh
authors.affiliation: Neurosciences Intensive Care, University of Alberta, Canada. Electronic address: Peter.Brindley@albertahealthservices.ca.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Brindley
mesh_terms: D000007:Abdominal Injuries / Q000150:complications / Q000628:therapy*; D000328:Adult; D001012:Aorta, Abdominal / Q000293:injuries; D001835:Body Weight / Q000502:physiology*; D002170:Canada; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D002983:Clinical Competence / Q000592:standards; D018592:Cross-Over Studies; D004634:Emergency Medical Technicians / Q000592:standards; D004638:Emergency Treatment / Q000379:methods*; D005260:Female; D006470:Hemorrhage / Q000517:prevention & control*; D006489:Hemostatic Techniques; D006801:Humans; D007083:Iliac Artery / Q000293:injuries; D008297:Male; D008348:Manikins; D008875:Middle Aged; D011312:Pressure; D011446:Prospective Studies; D014950:Wounds, Penetrating / Q000150:complications / Q000628:therapy*; D055815:Young Adult
keywords: Compression; External aortic compression; Junctional trauma; Noncompressible haemorrhage