The Science Journal of the American Association for Respiratory Care

2008 OPEN FORUM Abstracts


Teresa A. Volsko1, Robert L. Chatburn2, Nick Coniglio3

Background: Several portable ventilators with different operational characteristics are stockpiled and designated for emergency use.

Objective: The objective of this study was to evaluate the trigger characteristics during pressure support ventilation and effects of changing load (decreasing lung compliance and increasing airways resistance) on tidal volume delivery during volume controlled ventilation. We hypothesize that there would be performance differences among ventilator brands.

Methods: The Impact Univent 750, Viasys LTV 1000 and Newport HT-50 ventilators were connected to an ASL 5000 lung simulator (IngMar Medical Inc). A passive model was used to test stability of tidal volume delivery. Each ventilator was set to volume controlled continuous mandatory ventilation (VC-CMV) at a frequency of 15/min with a 1.0 second inspiratory time and a PEEP of 5 cmH2O. Set tidal volume was 500 mL or 1000 mL with normal load (compliance 75 mL/cm H2O, resistance 6 H2O/L/sec) and high load (compliance 40 mL/cm H2O, resistance 15.0 cm H2O/L/sec). Tidal volume delivery error was defined as 100% x (delivered volume - set volume)/set volume. To determine trigger performance during continuous spontaneous ventilation, we used an active lung model with a normal load and frequency of 15 breaths/min, PEEP of 5 cmH2O and a Pressure Support of 15 cm H2O above baseline. Differences in mean values were evaluated using one-way ANOVA. Statistical significance was set at p<0.05.

Results: The results are shown in Table 1. Tidal volume delivery was different among brands for the same Pressure Support settings. There were no differences in trigger variables but expiratory resistance was higher in the LTV 1000. There were no differences in tidal volume delivery error.

Conclusion: Stockpiled portable ventilators vary in some of their performance characteristics. Therapists must be aware of these differences in order to initiate and manage patients on portable mechanical ventilators.