• R L Tobia and R J Fischer.
• BOC Group Technical Center, Murray Hill, NJ 07974.
• Resp Care. 1994 Mar 1; 39 (3): 195-203.

BackgroundA prototype demand-flow medical ventilator for intensive care unit (ICU) applications has been developed with the ability to maintain continuous pressure regulation of proximal airway pressure during both inspiratory and expiratory respiratory phases. The performance of this system was investigated in laboratory tests of continuous positive airway pressure (CPAP) mode, a ventilatory mode in which airway pressure regulation is strongly challenged.Materials & MethodsComparative tests of the pressure-regulating ventilator (PRV) prototype and a Puritan-Bennett 7200a (PB7200a) ventilator were made in three performance categories: pressure-volume product error, peak pressure error during inspiration, and peak pressure error during expiration. Testing was performed on a Bio-Tek VT-2 test lung modified to simulate spontaneous breathing, at CPAP levels of 0, 10, and 20 cm H2O. Results were obtained at a lung compliance of 50 mL/cm H2O and at three parabolic airway resistance levels (Rp10, Rp20, and Rp50 cm H2O.L-2.s2 per ANSI Z79.7-1976).ResultsThe PRV prototype achieved reductions in pressure-volume product error of more than 0.111 joules (43%) for all test conditions, relative to the PB7200a. Peak pressure errors were reduced by at least 4.0 cm H2O (55%) during inspiration and 4.9 cm H2O (38%) during expiration.ConclusionsAn ICU ventilator utilizing continuous regulation of proximal airway pressure has been shown to provide statistically significant improvements in CPAP performance relative to the PB7200a in laboratory tests. Further testing will be required to quantify the clinical significance of these results.

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