EVALUATION OF 5 SMALL TURBINE-TYPE RESPIROMETERS USED IN ADULT ANESTHESIA

Objective. The purpose of this study was to determine the accuracy of five rotating vane or turbine-type respirometers-fdE Magtrak Respirato ry Monitor, fdE Haloscale Standard Wright Respirometer, Micro-Medical Pocket Monitor II, and Ohmeda 5400 and 5410 Volume Monitors-which are marketed as suitable for measuring expired gas volume in anesthetized adult patients. Methods. The devices were tested for accuracy at simul ated minute ventilations ranging from 2.4 to 15 L/min with three gas m ixtures: air, air saturated with water vapor, and N2O/O2 (70:30). Resu lts. In the usual range for adult minute ventilation during general an esthesia with intermittent positive-pressure ventilation (5-12 L/min), all devices were on average accurate to within 12%. At the lowest min ute volume readings (2.4 L/min) all devices except the Pocket Monitor tended to have low readings. No significant differences in readings we re introduced by either saturation with water vapor or introduction of 70% N2O, except with ventilation below 4 L/min with both Ohmeda respi rometers. Conclusions. All monitors showed reasonable clinical accurac y in the usual adult minute ventilation range during general anesthesi a with intermittent positive-pressure ventilation (> 5 L/min) when use d to measure air, water vapor-saturated air, or N2O/O2 mixtures.