Assessment of oxygen consumption from standard E cylinders by fluidic, turbine, and compressor style portable mechanical ventilators

Background

Gas consumption of portable ventilators is an important variable when considering ventilation in mass casualty events. We evaluated the oxygen consumption from standard E cylinders of fluidic (IC-2A; BioMed Devices, CT, USA), turbine (LTV-1000; Pulmonetic Systems, MN, USA), and compressor (Impact 754; Impact Instrumentation, NJ, USA) style transport ventilators.

Methods

Each ventilator was connected to a Training Test Lung (TTL) (Michigan Instruments, MI, USA) in Assist Control (A/C) with tidal volume (VT) 750 ml at a rate of 12 breaths per minute (bpm), providing a minute ventilation (VE) of 9.0 l/min. The positive end expiratory pressure (PEEP) was set at 0 and 10 cmH₂O, and the fraction of inspired oxygen (FiO₂) at 1.0 and 0.5. Ventilators used either compressed gas (IC-2A) or electricity (LTV-1000 and Impact 754) as power sources. All oxygen sources were standard E cylinders beginning with 2200 psi (680 l) connected to ventilators with standard regulators. Ventilators were connected to TTL by manufacturer-provided corrugated tubing. FiO₂ and VE were continuously monitored during each run and the time of operation was recorded. Three runs were conducted at each ventilator setting. The time of operation was recorded and the ventilator oxygen consumption was calculated.

Results

Each run delivered 9 l VE on A/C ventilation to the TTL. With FiO₂ 1.0 and PEEP 0 cmH₂O, times to complete E cylinder gas consumption for the IC-2A, LTV-1000, and Impact 754 ventilators, respectively, were 34.3 (± 1.2), 43.3 (± 0.6), and 69.0 (±1.7) min. With FiO₂ 1.0 and PEEP 10 cmH₂O, run times were 34.0 (± 1.0), 41.8 (± 1.6), and 69.3 (± 1.2) min. For the LTV-1000 and the Impact 754 with FiO₂ 0.5 and PEEP 0 cmH₂O, respective run times were 105.8 (± 13.0), and 144 (± 11.6) min. For each run the oxygen consumption in addition to the delivered VE for the IC-2A, LTV-1000, and Impact 754 was 10.8 (± 0.7), 6.7 (± 0.2), and0.9 (± 0.2) l/min with FiO₂ 1.0 and PEEP 0 cmH₂O, and was 11.0 (± 0.6), 7.3 (± 0.6), and 0.8 (± 0.2) l/min with FiO₂ 1.0 and PEEP 10 cmH₂O. For the LTV-1000 and Impact 754, oxygen consumption was 3.2 (± 0.8) and 1.4 (± 0.4) l/min on settings of FiO₂ 0.5 and PEEP 0 cmH₂O.

Conclusions

Our initial runs to assess E cylinder oxygen consumption of various types of ventilators demonstrate that fluidic and turbine style ventilators consume more oxygen than compressor style ventilators. The turbine ventilator tested uses a continuous flow of 10 l/min, which is gas inefficient. PEEP has little effect on oxygen consumption. Use of the internal air sourceand lower FiO₂ significantly increased the length of operationfrom an E cylinder. If oxygen E cylinders are a scarce resource, our data suggest that compressor style transport ventilators may currently be the transport ventilators of choice.