Evaluation of Ventilators Used During Transport of Critically Ill Patients: A Bench Study

The study referenced here and available for download (PDF) here used the Michigan Instruments Dual Adult TTL to test several emergency and transport ventilators over their range of operation.

The TTL was able to simulate various respiratory conditions with decreased or increased compliance and resistance. The TTL was also used to simulate spontaneous breathing patients, using one lung as the “driver” and one as the spontaneous breather. This allowed the investigators to evaluate the responsiveness of the ventilators to patient effort. In Summary: applying realistic loads and forces on these ventilators revealed important differences, including significant weaknesses in the performance of some models.

Originally published in RESPIRATORY CARE • NOVEMBER 2013 VOL 58 NO 11

Evaluation of Ventilators Used During Transport of Critically Ill Patients: A Bench Study

by Salah Boussen PhD MD, Marc Gainnier PhD MD, and Pierre Michelet PhD MD

OBJECTIVE: To evaluate the most recent transport ventilators’ operational performance regarding volume delivery in controlled mode, trigger function, and the quality of pressurization in pressure support mode.

METHODS: Eight recent transport ventilators were included in a bench study in order to evaluate their accuracy to deliver a set tidal volume under normal resistance and compliance conditions, ARDS conditions, and obstructive conditions. The performance of the triggering system was assessed by the measure of the decrease in pressure and the time delay required to open the inspiratory valve. The quality of pressurization was obtained by computing the integral of the pressure-time curve for the first 300 ms and 500 ms after the onset of inspiration.

RESULTS: For the targeted tidal volumes of 300, 500, and 800 mL the errors ranged from –3% to 48%, –7% to 18%, and –5% to 25% in the normal conditions, – 4% to 27%, –2% to 35%, and –3% to 35% in the ARDS conditions, and 4% to 53%, 6% to 30%, and 30% to 28% in the obstructive conditions. In pressure support mode the pressure drop range was 0.4 –1.7 cm H2O, the trigger delay range was 68 –198 ms, and the pressurization performance (percent of ideal pressurization, as measured by pressure-time product at 300 ms and 500 ms) ranges were –9% to 44% at 300 ms and 6%– 66% at 500 ms (P < .01).

CONCLUSIONS: There were important differences in the performance of the tested ventilators. The most recent turbine ventilators outperformed the pneumatic ventilators. The best performers among the turbine ventilators proved comparable to modern ICU ventilators. Key words: mechanical ventilation; transport ventilator; bench study; ICU patient transport; pressure support ventilation; inspiratory trigger; ventilator performances.

[Respir Care 2013;58(11): 1911–1922. © 2013 Daedalus Enterprises]

Download the full study here: http://rc.rcjournal.com/content/respcare/58/11/1911.full.pdf