title: Evaluation of transport ventilators at mild simulated altitude: a bench study in a hypobaric chamber.
abstract: BACKGROUND
  Previous studies on ventilators used for air transport showed significant effects of altitude, in particular with regard to accuracy of the tidal volume (VT) and breathing frequency. The aim of the study was to evaluate transport ventilators under hypobaric conditions.
  
  
  METHODS
  We conducted a bench study of 6 transport ventilators in a Comex hypobaric chamber to simulate mild altitude (1,500 m [4,920 feet] and 2,500 m [8,200 feet]). The ventilators were connected to a test lung to evaluate their accuracy: (1) to deliver a set VT under normal resistance and compliance conditions at F(IO2) = 0.6 and 1, (2) to establish a set PEEP (0, 5, 10, and 15 cm H2O), and (3) to establish a set inspiratory pressure in pressure controlled mode, (4) at a F(IO2) setting, and (5) and at a frequency setting.
  
  
  RESULTS
  Four ventilators kept an average relative error in VT of < 10% without effect of altitude. The Medumat ventilator was affected by the altitude only at F(IO2) = 1. The Osiris 3 ventilator had > 40% error even at 1,500 m. We found no change in frequency as a function of altitude for any ventilators studied. No clinically important differences were found between all altitudes with the PEEP or inspiratory pressure setting. Although F(IO2) was affected by altitude, the average error did not exceed 11%, and it is unclear whether this fact is an experimental artifact.
  
  
  CONCLUSIONS
  We have shown that most of the new transport ventilators tested require no setting adjustment at moderate altitude and are as safe at altitude as at sea level under normal respiratory conditions. Older technologies still deliver more volume with altitude in volumetric mode.
authors: Salah
authors: S
authors: Boussen
authors: Mathieu
authors: M
authors: Coulange
authors: Marc
authors: M
authors: Fournier
authors: Marc
authors: M
authors: Gainnier
authors: Pierre
authors: P
authors: Michelet
authors: Christophe
authors: C
authors: Micoli
authors: Lionel
authors: L
authors: Negrel
mesh_terms: D017732:Air Ambulances; D000531:Altitude; D001273:Atmosphere Exposure Chambers; D001274:Atmospheric Pressure; D019544:Equipment Failure Analysis; D006801:Humans; D008954:Models, Biological; D056152:Respiratory Rate; D013990:Tidal Volume; D012122:Ventilators, Mechanical