title: Ventilation through a small-bore catheter: optimizing expiratory ventilation assistance.
abstract: BACKGROUND
  Emergency ventilation through a small-bore transtracheal catheter can be lifesaving in a 'cannot intubate, cannot ventilate' situation. Ejectors, capable of creating suction by the Bernoulli principle, have been proposed to facilitate expiration through small-bore catheters. In this bench study, we compared a novel, purpose-built ventilation ejector (DE 5) with a previously proposed, modified industrial ejector (SBP 07).
  
  
  METHODS
  The generated insufflation pressures, suction pressures in static and dynamic situations, and also suction capacities and entrainment ratios of the SBP 07 and the DE 5 were determined. The DE 5 was also tested in a lung simulator with a simulated complete upper airway obstruction. Inspiratory and expiratory times through a transtracheal catheter were measured at various flow rates and achievable minute volumes were calculated.
  
  
  RESULTS
  In a static situation, the SBP 07 showed a more negative pressure build-up compared with the DE 5. However, in a dynamic situation, the DE 5 generated a more negative pressure, resulting in a higher suction capacity. Employment of the DE 5 at a flow rate of 18 litre min(-1) allowed a minute volume through the transtracheal catheter of up to 8.27 litre min(-1) at a compliance of 100 ml cm H(2)O(-1). The efficiency of the DE 5 depended on the flow rate of the driving gas and the compliance of the lung simulator.
  
  
  CONCLUSIONS
  In laboratory tests, the DE 5 is an optimized ventilation ejector suitable for applying expiratory ventilation assistance. Further research may confirm the clinical applicability as a portable emergency ventilator for use with small-bore catheters.
authors.affiliation: Department of Anaesthesia, Maastricht University Medical Centre, PO Box 5800, 6202 AZ Maastricht, The Netherlands. a.hamaekers@mumc.nl
authors.forename: A E W
authors.initials: AE
authors.lastname: Hamaekers
authors.forename: P A J
authors.initials: PA
authors.lastname: Borg
authors.forename: T
authors.initials: T
authors.lastname: Götz
authors.forename: D
authors.initials: D
authors.lastname: Enk
mesh_terms: D000399:Air Pressure; D000402:Airway Obstruction / Q000628:therapy*; D000403:Airway Resistance / Q000502:physiology; D003413:Cricoid Cartilage / Q000601:surgery; D004630:Emergencies; D004867:Equipment Design; D045853:Exhalation / Q000502:physiology; D006611:High-Frequency Jet Ventilation / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D007327:Insufflation / Q000295:instrumentation; D013396:Suction; D013957:Thyroid Cartilage / Q000601:surgery; D012122:Ventilators, Mechanical