The Science Journal of the American Association for Respiratory Care

2008 OPEN FORUM Abstracts


Thomas C. Blakeman1, Richard D. Branson1

Background: In the event of power failure, intensive care unit (ICU) ventilators have an internal back-up battery to continue operation. A reliable back-up battery is necessary to ensure patient safety in the event of power failure. We evaluated the variability in battery life of two ICU ventilator models used at our institution.

Methods: We randomly selected 6 Draeger Evita XL and 4 Siemens Servo 300 ventilators for the tests. Regularly scheduled preventive maintenance was performed by biomedical engineering every 6 months on all ventilators. The internal battery is changed every 2 years in the Evita XL and every 3 years in the Servo 300. Each ventilator taken from respiratory care department stock had an operational verification procedure performed and was ready for clinical use. The ventilators were connected to AC power and allowed to charge per manufacturer instructions. For each test, the ventilator was attached to one chamber of a Michigan Instruments Training Test Lung. Lung compliance was set at 0.04 L/cmH2O and resistance at 5.0 cm H2O/L/s. Each ventilator was tested on the same settings in assist/control mode. The respiratory rate was 20 breaths/min, tidal volume was 500 ml, FIO2 was 0.6, inspiratory time was 1 second, and PEEP was 5 cmH2O. A minimum of 2 tests were done with each ventilator. The data (± SD) are shown below.

Results: The battery life range across all ventilators was 5-69 minutes. One of each ventilator model shut off without warning after 5 minutes of operation. Preventive maintenance was performed on all ventilators within the previous three months. All but one of the Evita XL ventilators had the battery changed at the last preventive maintenance. The one that was not changed had the shortest battery duration (5 min). The battery in this ventilator had been in service for 15 months. The Servo 300 with the shortest battery duration (5 min) had been in service for 7 months. Two other Servo 300 ventilator batteries had been in service for 25 months. One had a battery life of 34 ± 2.8 minutes, the other had a battery life of 68 ± 1.4 minutes.

Conclusion: Back-up battery life of ICU ventilators vary widely even among the same ventilator models. Despite regular preventive maintenance, battery performance may still be much less than predicted. Clinicians must be aware of the potential differences in back-up battery life in the event of power failure.