Description of the oxygen concentration delivered using different combinations of oxygen reservoir volumes and supplemental oxygen flow rates with the Ohmeda Universal Portable Anesthesia Complete draw-over vaporizer system

The Ohmeda Universal Portable Anesthesia Complete system is used in austere conditions where oxygen resources are limited and must be conserved. The purpose of this study was to describe the concentration of oxygen delivered with different combinations of seven oxygen reservoir volumes and four oxygen flow rates. The Medical Education Technologies Incorporated Human Patient Simulator reproduced human physiological tidal volumes of four simulated patients of different weights based upon a typical soldier's weight. Using least squares multiple nonlinear regression, a formula for the curves of the oxygen concentrations was developed. The analysis, across the different patient weights, showed no appreciable increase in oxygen concentration beyond a reservoir volume of 260 mL. Our findings suggest the current standard universal portable anesthesia complete reservoir may not provide optimal oxygen delivery, therefore, we recommend the current reservoir volume be increased from 130 to 260 mL.