The Science Journal of the American Association for Respiratory Care

2008 OPEN FORUM Abstracts


Thomas Blakeman1, Dario Rodriquez2, Richard Branson1

Background: Resource planning is essential to success during patient transport. Mechanically ventilated patients should have adequate oxygen supplies to ensure the transport is completed without incident. The LTV-1000 ventilator utilizes a program to calculate oxygen cylinder duration. We evaluated the accuracy of this algorithm in a laboratory setting.

Methods: The LTV-100 was attached to one chamber of a dual-chambered Michigan Instruments Training Test Lung. Lung compliance was set at 0.04L/cmH2O and resistance was 5.0cm H2O/L/s. Each test began with a full E type oxygen cylinder. The same calibrated regulator was used for all the tests. Beginning cylinder pressures ranged from 2000-2100 psi. We evaluated seven combinations of ventilator settings. With each setting, the tidal volume was 0.5L and the inspiratory time was 1.0 seconds. Data are shown in the table. The last two tests were done to simulate patient triggering. A lift bar was placed between the test lung chambers such that a driving ventilator simulated spontaneous breathing. For the first of these tests, the settings of the test ventilator were; volume-controlled ventilation, assist control mode, respiratory rate of 10/min, PEEP of 0 cm/H2O, FiO2 of 1.0. The settings of the driving ventilator were identical except the respiratory rate was set at 20/min. Before each test, the cylinder duration calculator program was accessed on the LTV-1000. Cylinder size and pressure were entered, and the program calculated the cylinder duration based on the settings. For the next test, the settings of both ventilators were identical to the previous test, with the exception being that the driving ventilator started assisting while the test was in progress. When triggering was initiated, the cylinder pressure was entered into the program and the new calculation was made.

Results: For each test, the ventilator algorithm underestimated cylinder duration by 26%�5%. The range across the seven conditions was 6-40 minutes. The largest time difference was at a FiO2 of 0.6 and 0.4, which were 21 minutes and 40 minutes respectively.

Conclusion: Cylinder duration estimated by the LTV-1000 averages 26% shorter than actual cylinder duration. Clinicians should be aware of these differences when calculating oxygen requirements for transport.

*peak pressure setting was 13cmH2O #Simulated patient triggering of 20 breaths/minute