The Science Journal of the American Association for Respiratory Care

2007 OPEN FORUM Abstracts

BREATH ANALYSIS OF PROPORTIONAL ASSIST VENTILATION AND AUTOMATIC TUBE COMPENSATION.

S. Richey1, D. Grooms2


Background: Proportional Assist Ventilation (PAV) and Automatic Tube Compensation (ATC) are two forms of ventilatory assist that compensate for the flow-dependent resistance of the endotracheal tube. Additionally, PAV compensates for additional pathologic resistance. It was hypothesized that in a simulated spontaneous breathing model with low resistance, there would be only a modest difference in compensation between PAV 75% compensation & ATC 100% compensation.

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 Galileo Ventilator (Hamilton Medical, Reno, NV) using minimum settings to generate spontaneous breathing of a second test lung (spontaneous model) connected to a PB 840 ventilator (Tyco Healthcare, LLC). The Volume Control-CMV mode was used for the driving ventilator with the following settings: Vt = 530, Frequency = 14, I-time = 1.0 seconds, PEEP= +5, Peak flow = 51 Lpm delivered with a sinusoidal waveform pattern, which created a peak inspiratory flow at the proximal end of the E.T.T. of 18 lpm on the spontaneous model. Flow measurement was verified utilizing a Bicore monitoring device (Bicore Monitoring Systems, Irvine, CA). Test conditions consisted of a static compliance of 60 mL/cmH2O, & three stages of resistance changes 5.0, 7.5, & 9.3 cmH2O/L/sec. Breath Analysis consisted of capturing time and pressure data from the proximal end of the E.T.T. by utilizing the Galileo’s Auxiliary pressure port and Data Logger software (Hamilton Medical). The “Area Under the Curve” was calculated for each breath using the “linear trapezoidal rule”& the paired two sample t test was used to evaluate differences between the modalities using spreadsheet software (Excel, Microsoft, Redmond, WA).

Results: When comparing the area under the curve 75% PAV significantly provided a greater pressure compensation in the three resistive states over 100% ATC (p 0.02) (figure 1).

Conclusion: The findings of this study reveal that even in low resistive models 75% PAV provides greater compensation over 100% ATC.


Figure 1: Breath Analysis Comparing PAV with ATC in various resistive states. AUC= Area Under the Curve.
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