The Science Journal of the American Association for Respiratory Care

2007 OPEN FORUM Abstracts

A COMPARISON OF AUTOMATIC TUBE COMPENSATION AND PROPORTIONAL ASSIST VENTILATION UTILIZING A SIMULATED SPONTANEOUS BREATHING MODEL.

S. Richey1, D. Long2



Background: The purpose of this study was to assess the pressure compensation of ATC and PAV in various conditions.

Methods: A simulated spontaneous breathing model was utilized consisting of a dual chamber, Double TTL test lung (Michigan Instruments). One test lung (driving model) was powered by a PB 840 ventilator (PB 840, Tyco Healthcare, LLC.) using minimum settings to generate spontaneous breathing of a second test lung (spontaneous model) connected to another PB 840.The Assist Control Pressure Control (ACPC) mode was used for the driving ventilator with the following settings: PC of 8 cmH2O, RR 12 bpm, I-time of 1.0 second, PEEP 5. Rise time % setting was changed by 20% in 5 stages to simulate different peak inspiratory flow rates. Test conditions consisted of two models. Model 1: Low Static (added) resistance (~7 cmH20/L/sec) with variable compliances
Model 2: Low Static compliance (20ml/cmH20) with variable added resistances.
A 7.0 mm (inner diameter) endotracheal tube was used for “Tube type” and “Tube I.D.” settings for both modalities. Three different levels of compensation were assessed for each mode (ATC 90, 95,100%) and (PAV 65, 70, 75%). Compensation pressure was recorded with each change in rise time, compliance, and resistance.


Results:
Model 1: The amount of pressure compensation differed significantly between ATC & PAV when comparing all levels of compensation for compliance changes (p <0.05). Conversely, when comparing ATC 100% to PAV 75%, there was a modest difference in compensation pressure (p <0.11, Pearson correlation 0.91). Model 2: The amount of pressure compensation differed significantly between ATC & PAV when comparing all levels of compensation for resistive changes (p <0.01). Conversely, when comparing ATC to PAV in the low resistance state (2.5 cmH20), there was no difference in compensation pressure (Pearson correlation 1.00) (figure 1).


Conclusion: The findings of this study reveal that during low resistive conditions with variable compliance changes, ATC 100% and PAV 75% compensate virtually with the same pressure.

Comparison of pressure compensation during low resistive conditions.

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