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October 16-20, 2010 San Diego, CA Home Abstract Archive Search Abstracts 2010 Session Grid 2010 Meeting Website Policy Statements ASA Website Feedback 
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A1456
October 21, 2009 9:00 AM - 11:00 AM Room Area F |
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| Adaptive Pressure Control: Tidal Volume Variance during Simulated Bariatric Laparoscopic Surgery | |||||||||||||||||||||
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* Kirby S. Richey, B.S., R.R.T. Sentara Health System, Norfolk, Virginia |
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Background: Adaptive Pressure Control (APC) is a new modality in regards to anesthesia ventilation. The mode delivers a pressure control breath that maintains a minimum tidal volume (Vt) at the lowest possible pressure, independently of changes in pulmonary mechanics. Additionally, this mode has been marketed to be utilized during laparoscopic procedures, in which pulmonary compliance decrease due to pneumoperitoneum, resulting in peak inspiratory pressure increases by 17% to 109%.
Objective: To investigate Vt consistency and latency of Vt adaptation during inflation and deflation of pneumoperitoneum. Methods: An interactive mathematical model and two anesthesia machines: Apollo and the Aysis 7900 Smart Vent were evaluated. Phase 1 An interactive spread sheet was programmed with validated equations, percent compliance change associated with pneumoperitoneum, device algorithm characteristics, and patient variables: ideal body weight- 71 kg, target Vt- 12 ml/kg, compliance-60. Once the patient variables were entered, the ventilator variables were set as follows: frequency-10, Vt- 850. These values were selected to match settings during general anesthesia. Phase 2 The two devices were alternatively connected (figure 1) a test lung with the following ventilator settings: frequency- 10, Vt- 850, PEEP- 5, I: E ratio- 1:2.[figure1]Ventilator settings remained constant throughout test scenarios. Volume measurement was verified using a “Bicore” monitoring device which was located at the Y-piece of the ventilator circuit. Test Conditions- consisted of a static resistance of 5 and switching the compliance to simulate inflation and deflation of a pneumoperitoneum of 15 mmHg. Measurement of exhaled Vt was continuous and documented at three intervals: baseline, inflation, and deflation. Each test series was administered five times, and mean values of the measurements were calculated. The two sample t test was used to identify differences. A of p value < 0.05 was considered to be statistically significant Results Phase 1 (figure 2) shows example of model output.[figure2]During inflation the Vt decrease was ∼40%; during deflation the Vt overshoot was ∼60% greater than the target Vt. Phase 2 During the inflation phase there was a significant difference in the Vt delivery between the two devices (p= 0.01), however during deflation and equalization periods the Vt variance was insignificant (p=0.33).[table1] From Proceedings of the 2009 Annual Meeting of the American Society Anesthesiologists. |
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Figure 1
 Figure 2  |