2005 OPEN FORUM Abstracts
THE RESPONSE OF DUAL CONTROL MODES TO CHANGES IN COMPLIANCE AND RESISTANCE.
Mike Troxell, PhD, RRT and Craig P. Black, PhD, RRT, The University of Toledo.
Background: Pressure regulated volume control (PRVC) is a mode of ventilation that combines volume ventilation and pressure ventilation into one mode to minimize the potential for volutrauma and barotrauma. This mode may be used to ventilate adult, pediatric, and, neonatal patients. Different manufacturers have included forms of this sophisticated dual-control mode of ventilation on their microprocessor controlled ventilators. Though there are slight differences in the way these manufacturers approach the delivery of the guaranteed volume, pressure cycled mechanical breath both accomplish the same objective. The purpose of this bench study was to use lung models to compare pressure, flow dynamics and the effect of the transition from inspiration to expiration with changing compliance and resistance in the Servo 300 pressure regulated volume control (PRVC) and the Puritan-Bennett 840 Volume Control plus (VC+) modes. In a second evaluation, a spontaneous breathing lung model (IngMar Medical ASL 5000) was used to evaluate the trigger function of the two ventilator modes. The hypothesis is that there are differences in these manufacturers dual-control modes of ventilation.
Methods: Each ventilator was connected to a Michigan Instruments Lung Simulator with settings and modes as described below. Ventilator settings remained constant as changes in test lung resistance and compliance were made.
Results: Both ventilators responded in a similar manner to changes in resistance and compliance with no significant differences in volumes and pressures. There was a significant difference in response time, however.
Conclusion: PRVC and VC+ respond the same to changes in compliance and resistance, and PRVC has a slightly faster response time with the settings used in this evaluation.
Response to test lung changes in compliance and resistance:
| Ventilator with mode | Compliance | Resistor | Peak Pressure | Mean Pressure | Exhaled Vt | I time |
| PB 840/ VC+ | 0.02L/cmH20 | Rp 7.7 | 28 cmH20 | 6.9cmH20 | 500 ml | 1.0 sec |
| Servo300/PRVC | 0.02L/cmH20 | Rp 7.7 | 29 cmH20 | 8.0 cmH20 | 500 ml | 1.0 sec |
| PB 840/ VC+ | 0.02L/cmH20 | Rp 3.9 | 32cmH20 | 6.9 cmH20 | 500 ml | 1.0 sec |
| Servo300/PRVC | 0.02L/cmH20 | Rp 3.9 | 31 cmH20 | 8.0 cmH20 | 515 ml | 1.0 sec |
| PB 840/ VC+ | 0.05L/cmH20 | Rp 3.9 | 13 cmH20 | 5.3 cmH20 | 500 ml | 1.0 sec |
| Servo300/PRVC | 0.05L/cmH20 | Rp 3.9 | 14 cmH20 | 5.0 cmH20 | 500 ml | 1.0 sec |
| PB 840/ VC+ | 0.01L/cmH20 | Rp 3.9 | 50 cmH20 | 11.0cmH20 | 533 ml | 1.0 sec |
| Servo300/PRVC | 0.01L/cmH20 | Rp 3.9 | 51 cmH20 | 13.0cmH20 | 493 ml | 1.0 sec |
Both ventilators were set at a respiratory rate of 10 bpm with set Vt = 500, with flow trigger.
Response Time comparison using ASL 5000 spontaneous breathing simulator:
| Test lung: | Inspiratory work | Expiratory work | Trigger time |
| PB 840/ VC+ | 665 mj | 195 mj | 225.68 ms |
| Servo 300/PRVC | 477 mj | 259 mj | 182.82 ms |
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