A Self-Calibrating Blood-Pressure Monitoring System

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MONITORING during surgical procedures has become standard practice, particularly during operations on the heart and the vascular system. Initially, the electrocardiogram alone was monitored; it gave useful information relative to the development of arrhythmias but few other data of clinical value. Monitoring the electroencephalogram may be helpful in determining at any particular moment the level of anesthesia and the adequacy of cerebral blood flow.

A notable decrease in arterial blood pressure may occur during anesthesia, without the development of clinical signs of hypotension or abnormality in the electrocardiogram or in the electroencephalogram. Although the anesthesiologist periodically records the arterial pressure indirectly, a continuous record is highly advantageous because changes in pressure may be sudden and critical. Under some circumstances, induced hypotension may be utilized to facilitate surgical procedures; during the hypotensive phase the arterial blood pressure may be difficult or impossible to determine by the indirect method. Strain gauges and other transducers have been used to record the arterial pressure directly. The level of pressure must be determined by reference to a calibration, and recording must be done on paper. This method of recording requires the presence of trained personnel. A need for a method of recording the arterial blood pressure continuously and displaying it instantaneously without reference to previous calibration has become apparent. It should be possible to display the record on the screen of a cathode-ray oscillograph.

We are reporting the development of a measuring and monitoring system in which a number of pressures are sequentially sampled by. . .



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