Biomedical instrumentation & technology / Association for the Advancement of Medical Instrumentation
-
Biomed Instrum Technol · Sep 1989
Comparative StudyLower esophageal contractility: a technique for measuring depth of anesthesia.
Until recently, there has been no simple, accurate, reliable technique for monitoring depth of anesthesia during surgery. A system that measures lower esophageal contractility (LEC) has been designed for this purpose. The system consists of a monitor and a disposable esophageal probe equipped with provoking and measuring balloons. ⋯ Multiple-center clinical studies have shown that LEC correlates significantly (p less than 0.005) with concentrations of volatile anesthetic agents and patient responses to surgical stimulation. Closed-loop anesthetic techniques have been developed at several institutions based on LEC and hemodynamic parameters. Lower esophageal contractility has been shown to be an accurate monitor of anesthetic depth for a variety of surgical procedures and anesthetic techniques.
-
To aid in the development of rodent models of respiratory dysfunction, the authors evaluated the ability of noninvasive pulse oximetry (SpO2) to continuously monitor oxygen saturation (SaO2) in the rat. In initial studies, a pulse oxyimeter (Nellcor N-100) detected a fall in SaO2 during hypoxia induced by hypobaric decompression or decreasing fractions of inspired oxygen (FIO2). The disposable sensor was placed proximally on the tail. ⋯ The blood samples were analyzed with an IL 282 CO-Oximeter for SaO2 and then compared with pulse oximeter values of SaO2. Between saturations of 75% and 95%, the standard deviation (SD) for the difference between the CO-Oximeter and pulse oximeter measurements of SaO2 was +/-5.7%; however, below 70%, mean pulse oximeter estimates were higher than arterial values and the SD for the difference increased. It is concluded that pulse oximetry can detect trends in oxygenation over time in anesthetized and unanesthetized rats and that the accuracy of pulse oximetry is such that between 75% and 95% SaO2 agreement between pulse oximetry and arterial blood sample values of SaO2 is acceptable.
-
Biomed Instrum Technol · Jan 1989
Semiautomatic algorithm to remove resonance artifacts from the direct radial artery pressure.
Resonance artifacts introduced by the catheter-manometer system are removed from the direct radial artery pressure using a three-step algorithm. First, the fast-flush method is used to identify the natural frequency and damping coefficient of the monitoring system by digitizing and analyzing the pressure transient created by the flush. ⋯ Third, the algorithm predicts the undistorted radial artery pressure, removing the resonance artifacts by inverse-filtering the digitized monitored pressure waveform using the RLC circuit derived previously. The algorithm was implemented using a personal computer, but it could also be used without the computer by incorporating an analog-to-digital convertor and a microprocessor in the hemodynamic monitor.