Medical technology manufacturers' view of a European data exchange.
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Equipment and Supplies↗
Biomedical subjects
C F Wallroth
Publications and source records attributed to C F Wallroth.
Refractive indices for volatile anesthetic gases: equipment and method for calibrating vaporizers and monitors.
OBJECTIVE: The objective of our study was to establish the refractive indices and the virial coefficients of the volatile anesthetic vapors. These indices and coefficients will allow refractometry to be used by manufacturers to produce accurate calibration, without requiring expensive high-precision calibration gases. METHODS: We used a precision refractometer to measure the refractive indices for five volatile anesthetic vapors. We prepared our calibration gases by mixing a gravimetrically calibrated amount of liquid agent with a constant gas flow. RESULTS: The refractive indices for the volatile anesthetic vapors are 1,603.2 for halothane, 1,540.4 for enflurane, 1,563.3 for isoflurane, 1,538.3 for sevoflurane, and 1,211.7 for desflurane. The maximum theoretical error in our measurements, due to all sensors and all uncertainty in our measurement of apparatus and physical constants, is +/- 0.56% of the reading (+/- 0.70% for desflurane). CONCLUSIONS: If refractometry replaced calibration gases in cylinders, as a calibration standard, manufacturers might avoid errors that now occur because calibration gases manufactured by numerous companies seem to differ. We propose that our values serve as an interim database.
Anesthesia, Inhalation↗
Standard gases used to calibrate anesthetic vapor analyzers: are they stable?
OBJECTIVE: Gas cylinders containing volatile anesthetic vapors often are used to calibrate anesthetic agent analyzers. Differences seen between manufacturers in device calibration may be the result of error in the preparation of these calibration standards or drift in their concentration. METHODS: We measured the stability of 29 calibration gases in 2-L aluminum cylinders over a 15-month period. We also measured the stability of 18 gases in 1-L aluminum mini bottles. RESULTS: We found an average change of less than 0.02 vol% in the concentration of volatile anesthetic vapors for the 2-L aluminum cylinders containing 1.0 vol%. The maximum change was 0.04 vol%. For the 2-L cylinders, the manufacturer's certified concentration was 0.03 to 0.09 vol% higher than the concentration we measured on receipt. For the mini bottles, we found an average change of less than 0.04 vol% during a 6-month period; the maximum change was 0.06 vol%. The maximum change in 12 months was 0.14 vol%. CONCLUSIONS: Our results indicate that calibration gases containing volatile anesthetic vapors appear to be stable when stored in suitable cylinders. Aluminum cylinders sealed with a stop-cock seem to be suitable. In contrast, mini bottles seem to be less stable, probably due to the sealing construction. The difference of up to 0.09 vol% between our measurement of vapor concentration and the manufacturer's certified concentration may result from adsorption on surfaces in the cylinders after preparation or may reflect differences in calibration technique.
Anesthetics↗
Closed-loop control for anesthesia breathing systems.
Numerous medical applications of closed-loop control have been developed over the past 40 years. For the patient breathing system, appropriate sensors are available. Feedback controllers have been developed and tested. Gas and vapor delivery devices seem ready for use. With the sensors, controllers, and delivery devices developed and tested, it seems likely that closed-loop control will be an integral part of future anesthesia workstations. The convenience and improved stability and response time will be important advantages in future anesthesia delivery systems.
Algorithms↗
Technical conception for an anesthesia system with electronic metering of gases and vapors.
The technical conception for an anesthesia system will be presented, which is designed to measure and to meter anesthetic gases and anesthetic vapor under computer control. By these means the oxygen supply and anesthetic vapor supply to the patient can be automated, which should allow to improve the patient's safety during anesthesia. In order to meet these objectives novel systems for measurement and metering of gases and anesthetic vapors have to be developed. Prototypes of these components will be described and a first design proposal for the anesthesia system will be presented.
Anesthesia, Inhalation↗