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October 19, 2009
2:00 PM - 4:00 PM
Room Area M
Battery Duration with Mechanical Ventilation in a Field Anesthesia Machine
  **   Anthony Giberman, B.S., Dale F. Szpisjak, M.D., M.P.H., Richard R. Kyle, M.S.
Anesthesiology, Uniformed Services University of the Health Sciences, Bethesda, Maryland
Introduction: The Magellan-2200 Model-2 (Oceanic Medical Products, Inc., Atchison, KS) is a field anesthesia machine (FAM) with an electronic controlled, pneumatically powered ventilator. Compressed air for fresh gas flow (FGF) and ventilator power can be supplied by the compPAC air compressor (Smiths Medical International, Kent, England) which contains a rechargeable battery. Knowledge of ventilator performance as the battery discharges affects patient safety, especially when electrical infrastructure is unreliable. The goal of this study was to determine battery duration and ventilator performance in mechanical lung models with high (HC) and low (LC) pulmonary compliance.

Methods: The FAM was assembled and an adult, semi-closed, circle breathing system was attached. Compressed air for FGF and pneumatic power to the ventilator was supplied by the compPAC air compressor. The model 3700 linear pneumotach (Hans Rudolph, Kansas City, MO) was attached between the circuit Y-piece and VentAid TTL® calibrated test lung (Michigan Instruments, Grand Rapids, MI). Respiratory data were recorded with the RSS 100HR Research Pneumotach after calibration with a 3-L syringe. The battery was fully charged overnight before each data collection period. Two lung compliances were tested: HC = 100 mL/cm H 2 O and LC = 20 mL/cm H 2 O. Target respiratory parameters were V T = 750 (±25) mL, RR = 10 bpm, and FGF = 1 L/min. Control limits(1) were determined from the first 200 minutes of battery power. The upper and lower control limits were mean V T ± 3 SD, respectively. There were 4 runs for each compliance. RR and V T were recorded each minute and breath, respectively. Battery depletion occurred when the 5 consecutive V T data points were below the lower control limit. Groups were compared with the independent samples t -test. P < 0.05 accepted as significant.

Results: Battery duration was less in the HC group compared with the LC group [220.5 (± 3.7) v. 213.8 (± 1.5) min, P = 0.015].[figure1][figure2]The difference in the HC and LC V T for the first 200 minutes (steady state) was clinically insignificant [742 (± 6) v. 743 (± 7) mL, respectively]. The difference in the RR for the HC and LC groups at steady state was also clinically insignificant [10.2 (±0.7) v. 10.3 (±0.7) bpm, respectively].

Conclusion: Battery duration when ventilating a LC lung model was 221 minutes and 7 minutes more than in the HC lung model. Using this ventilator for a maximum of 3 hours (starting with a fully charged compPAC battery) provides a safety factor of > 30 minutes in both HC and LC lungs.

Reference: 1. Albright SA, Winston W, Zappe CJ. Statistical Process Control. In: Data analysis and decision making with Microsoft excel. Pacific Grove: Brooks/Cole 1999:499-550.

From Proceedings of the 2009 Annual Meeting of the American Society Anesthesiologists.
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