International journal of clinical monitoring and computing
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Int J Clin Monit Comput · Jan 1987
Historical ArticlePulse oximetry: historical review and Ohmeda functional analysis.
Oximetry relies on the detection of the spectral properties of oxygenated and reduced hemoglobin. In vitro bench analysis capabilities have spurred the desire to accomplish accurate in vivo measurement through various techniques. The 1930-40s were a particularly active period for oximetry culminating in the development of pulse oximeters in the 1970s. ⋯ Arterial oxygen saturation readings are derived from the ratio of pulse-added signals of red and infrared light energy passed through tissue. Data manipulation that includes empirically derived constants produces numerical data that is clinically useful. A photo-plethysmographic waveform display of actual oximeter signal closes the loop between man and machine.
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Int J Clin Monit Comput · Jan 1987
Closed-loop control of blood pressure, ventilation, and anesthesia delivery.
Closed-loop control systems have been in use for over 4,000 years, yet applications in medicine have developed only recently. When compared with manual control, closed-loop controllers for blood pressure, ventilation, and anesthesia delivery provide more rapid and more precise control of mean pressure, end-tidal CO2, and end-tidal anesthetic concentrations. ⋯ It must be remembered however, that the best anesthesiologist may perform better than the controller, particularly in his ability to anticipate clinical events which effect control. Although the convenience, precision of control, and immunity to distractions are reason enough to further pursue their development, their final application to clinical care will depend on the inclusion of appropriate safeguards and supervisory software algorithms to protect the systems from failure.
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Computers are beginning to appear in the operating room and intensive care units. At this time most computers are reserved for complex cases. However, it is now possible to discern what role the computer may play in the future, for routine cases. An outline of a conceivable integrated computerized system in anesthesia is presented.
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The place of computerization in intravenous anaesthesia delivery: Although total intravenous anaesthesia may have advantages over inhalational anaesthesia in certain circumstances, it has drawbacks from the point of view of feedback control. The ideal agent is not available, although di-isopropylphenol holds promise. There is an undefinable end-point. ⋯ The anaesthetist is still required for, amongst other things, specifying the desired depth of anaesthesia and varying it during the operation, and for responding to unforeseen crises. It may be hoped that, by liberating the anaesthetist from those tasks which can be automated, more time can be devoted to patient monitoring and other aspects of anaesthetic care, thereby improving patient safety. There is an undoubted place for computerized delivery of anaesthesia in teaching (particularly teaching pharmacokinetic principles) and in research (for standardization of anaesthetic depth).
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To address the problem of auditory alarms on anaesthesia monitoring and delivery devices whose signal is masked by the noises of other operating room equipment, a set of signals having the characteristics of spectral richness, frequency modulation, and temporal patterning were electronically generated, and were tested for detectability against operating room equipment noises in a laboratory setting. A set of signals was identified which can, under these circumstances, be detected with at least 93% accuracy at -24 dB signal-to-noise ratio.