Calibration of seven ICU ventilators for mechanical ventilation with helium-oxygen mixtures

The study evaluated seven intensive care unit (ICU) ventilators (Veolar FT, Galileo, Evita 2, Evita 4, Servo 900C, Servo 300, Nellcor Puritan Bennett 7200 Series) with helium-oxygen (HeO2), using a lung model, to develop corr ection factors for the safe use of HeO2. A 70:28 helium-O-2 mixture (heliox ) replaced air and combined with O-2 (HeO2). Theoretical impact of HeO2 on inspiratory valves and gas mixing was computed. True fraction of inspired o xygen (Ro,del) was compared with fraction of inspired oxygen (FIo2) set on the ventilator (FI(o2)set). True tidal volume (VTdel) was compared with VT set on the ventilator (VTset) in volume control and with control VTdel at F Io2 1.0 in pressure control. FI(o2)del minimally exceeded FI(o2)set (less t han or equal to 5%) except with the 7200 Series (FI(o2)del > FI(o2)set by 1 25%). In volume control, with the Veolar FT, Galileo, Evita 2, and Servo 90 0C, VTdel > VTset, with the 7200 Series VTdel < VTset (linear relationship, magnitude of discrepancy inversely related to FI(o2)set). With the Evita 4 , VTdel > VTset (nonlinear relationship), whereas with the Servo 300 VTdel = VTset. In pressure control, VTdel was identical to control measurements, except with the 7200 Series (ventilator malfunction). Correction factors we re developed that can be applied to most ventilators.