Journal of clinical monitoring
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Our objective was to study the effect of the temperature of the anesthetic gas mixture (AGM) on esophageal temperature measurements made in children whose tracheas had been intubated for anesthesia. We also sought to establish the optimal site for the temperature sensor in the esophagus and to find a way to accurately place the sensor. ⋯ We conclude that best results are obtained when care is taken to place the thermistor in the lower quarter of the esophagus. (We provide a simple formula for calculating this placement in pediatric patients of varying ages.) Placing the probe by acoustic criteria cannot consistently be relied on to provide good thermometry.
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This second article in a 2-part series on the operation of principal components within Narkomed anesthesia systems describes the function and compensation mechanisms of the Dräger 19.n vaporizer, the operating principles of the anesthesia ventilator-electronic, the structure and mechanics of the pressure limit control, and the 3 basic monitoring systems built into the anesthesia system. Part II of this series builds on the data published in part I (J Clin Monit 1992;8:295-307).
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Pulse oximeters are known to be inaccurate in the presence of elevated concentrations of carboxyhemoglobin and methemoglobin. This paper attempts to alleviate some of the confusion that exists between fractional and functional saturation, and to clarify the comparison of each with SpO2. A series of theoretical relationships between pulse oximeter reading (SpO2) and actual oxygen saturation (both fractional and functional) is derived using simple absorption theory. ⋯ This consists of a blood circuit containing a model finger, capable of simulating the pulsatile transmission signals through a real finger. Theoretical predictions and experimental results are compared and are found to agree well in the presence of carboxyhemoglobin, but less well with methemoglobin. Possible reasons are discussed.
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The objective of this study was to evaluate the effect of positive end-expiratory pressure (PEEP) on capnography. ⋯ These results demonstrated that absence of gas flow immediately after the application of PEEP may transiently abolish a capnogram when the lung volume increases.