摘要:

Errors in measurement of exhaled gas volume, mixed expired oxygen and carbon dioxide concentrations, and inspired oxygen concentration and the presence of exhaled anesthetic agents cause errors in on-line calculated oxygen uptake that increase geometrically with increasing inspired oxygen concentration. No one has quantified the decrease in the magnitude of the error that might be realized if directly measured nitrogen concentration were included in the calculation. We used a computer model to evaluate this improvement, assuming an oxygen uptake of 200 ml/min and normal ventilatory parameters. Using a Monte Carlo technique, we generated 100 sets of data points, with random errors averaging 0.5% around the expected gas concentrations, and compared the accuracy of oxygen uptake calculated with and without inclusion of directly measured inspired and expired nitrogen concentrations. When the inspired oxygen fractions were 0.2, 0.5, and 0.8, the calculated oxygen uptakes ·% standard deviation were 200·4.3, 200·12, and 196·21 when directly measured nitrogen was includedversus200·3.5, 196·16, and 205·71 when it was not. The procedure was repeated, assuming 50 ml/min of anesthetic excretion and the calculated oxygen uptakes were 200·4.6, 202·12, and 195·17versus212·3.8, 251·17, and 398·64. Including direct measurement of inhaled and exhaled concentrations of nitrogen or another insoluble inert tracer gas allows accurate measurement of oxygen uptake, even in the presence of exhaled anesthetic gases. It also decreases the error in oxygen uptake determination by a factor of nearly six when the inhaled oxygen fraction is 0.8.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The authors demonstrated that soda lime will adsorb enflurane or isoflurane as a function of the water content of the soda lime. Various volumes of liquid enflurane or isoflurane were placed in an equilibration flask containing fresh (15% water by weight) or dried soda lime and the vapor phase anesthetic concentrations plotted. When dry soda lime was used, the plot of concentration as a function of volume of liquid added was biphasic: initially flat and then rising linearly. This is qualitatively similar to data reported previously for halothane. The authors hypothesize that drying soda lime produces a molecular sieve-like structure, as adsorption is greatest for molecules with small carbon chain lengths and kinetic diameters, or with structural characteristics such as cis/trans isomerism, which effectively reduce molecular size.

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1985

数据来源: OVID