The Science Journal of the American Association for Respiratory Care
Background: Electronic and mechanical miniaturization has made it possible to compress what was once a large ICU ventilator into a laptop-sized, portable ventilator. With its internal battery and miniature blower, it is self-contained, except for an oxygen source necessary only to deliver FIO2 above .21. Our objective was to evaluate the LTV for accuracy of volume delivery under varied patient loads and power source conditions. The ventilator was tested under the following power source conditions: 1) A/C power, 2) battery fully charged, 3) battery 50% depleted, and 4) with the battery ?empty,? a warning that the battery is at its lowest charge level, with less than 10 min. of use left before a complete shutdown. A Vt change of less than 10% across all conditions was considered acceptable.
Methods: The LTV was set to deliver a Vt of .700L to a test lung (TTL Michigan Instruments) under various combinations of compliance and airway resistance and powered under different conditions (see table). A VenTrack 1550 (Novametrix Inc.) was connected at the airway to measure delivered tidal volume and monitor airway pressure. Three sample readings were averaged for each of the test situations. The ventilator was allowed to stabilize for 60 sec. before readings were taken.
Results: The largest average Vt .728L was under ?Baseline conditions?. The lowest average Vt .660L was under the highest test lung load with ?Battery Empty? conditions. Conclusion: The difference in Vt due to changes in power supply conditions are between 3% and 5%. The difference in Vt due to changes in test lung load are between 3% and 6%. Some of this can be accounted for in the ventilator circuit compliance. A situation in which all of the worst conditions were to occur are not only highly unlikely, but still causes less than a 10% change. Under all conditions tested, there was a minimal effect on ventilator output. We find the effect to be clinically insignificant.
(See Original for Figure)