title: Acute severe asthma: performance of ventilator at simulated altitude.
abstract: OBJECTIVE
  Exacerbation of asthma can be seen during air transport. Severe patients, not responding to conventional therapy, require ventilator support. We evaluated the performance of two transport ventilators, built with turbine technology, the T-birdVSO2 and the LTV-1000, for use during aeromedical evacuation of acute severe asthma. We have assessed the ability of both the ventilators to deliver to an acute severe asthma model a tidal volume (Vt) set at different simulated altitudes, by changing the ambient air pressure.
  
  
  METHODS
  The simulated cabin altitudes were 1500, 2500, and 3000 m (decompression chamber). Vt was set at 700 and 400 ml in an acute severe asthma lung model. Comparisons of the preset with the actual measured values were accomplished using a t-test.
  
  
  RESULTS
  Comparisons between the actual delivered Vt and set Vt showed a significant difference starting at 1500 m for both the ventilators. The T-birdVSO2 showed a decrease in the volume delivered, with a negative variation of more than 10% compared with the Vt set. The LTV-1000 showed mostly an increase in the volume delivered. The delivered Vt remained within 10% of the set Vt.
  
  
  CONCLUSIONS
  The accuracy of Vt delivery was superior with the LTV-1000 than with the T-birdVSO2, but the higher delivered Vt of the LTV-1000 are likely to be more harmful than lower delivered Vt of the T-birdVSO2.
authors.affiliation: Department of Anesthesia and Intensive Care, Military Hospital Val-de-Grace, 74 Boulevard de Port Royal, Paris, France. jeanpierre.tourtier@free.fr
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Tourtier
authors.forename: Emma
authors.initials: E
authors.lastname: Forsans
authors.forename: Thomas
authors.initials: T
authors.lastname: Leclerc
authors.forename: Nicolas
authors.initials: N
authors.lastname: Libert
authors.forename: Solange
authors.initials: S
authors.lastname: Ramsang
authors.forename: Karim
authors.initials: K
authors.lastname: Tazarourte
authors.forename: Michel
authors.initials: M
authors.lastname: Man
authors.forename: Marc
authors.initials: M
authors.lastname: Borne
mesh_terms: D017732:Air Ambulances; D000531:Altitude; D001249:Asthma / Q000175:diagnosis / Q000628:therapy*; D003664:Decompression; D018450:Disease Progression; D004867:Equipment Design; D004869:Equipment Safety; D006801:Humans; D008954:Models, Biological; D011175:Positive-Pressure Respiration; D013990:Tidal Volume; D012122:Ventilators, Mechanical