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Physiological Monitor System Disclosure Number: IPCOM000086183D
Original Publication Date: 1976-Aug-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 75K

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Dimmick, RF: AUTHOR [+2]


The system detects the onset of hypovolemic shock and helps to reduce the stress on the patient's physiological system induced by its occurrence.

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Physiological Monitor System

The system detects the onset of hypovolemic shock and helps to reduce the stress on the patient's physiological system induced by its occurrence.

Hypovolemic shock is caused by the removal of fluids from a patient's physiology at an excessive rate. The physiological system interprets this removal to mean that the patient is exsanguinating and, as a result, blood flow to the extremities is restricted in order to maintain the necessary supply to the vital organs. The external symptoms vary depending upon the patient, and the rate of fluid loss can produce a feeling of light headedness, nausea, vomiting and fainting. The accepted corrective technique in hemodialysis is to supply a volume replacement fluid in the form of normal saline, under a physician's care.

Because it is difficult to isolate, it is not known what the effects of the repeated stress due to hypovolemic shock are. However, it can be inferred that some proportion of the general physical deterioration of hemodialysis patients is caused by this form of shock. In fact, it is possible that, with some patients, a single or double massive occurrence, e.g., in an operating room environment, may sufficiently deteriorate the patient's physiology as to increase the recovery time, and thereby the length of the required stay in the hospital.

The accepted physiological system measurement of hypovolemic shock is a decrease in the patient's blood pressure. Since there is no way of noninvasively continuously measuring a patient's blood pressure, an attempt is made at inferring the onset of shock from (a) heart rate, (b) delay time between an electrical occurrence and its physical manifestation in an extremity, i.e., delay between the EKG R-wave and the pulse pressure wave, i.e., systolic time, and
(c) diastolic to systolic time.

Measurements indicate that some correlation exists. However, there are cases where a deviation could be interpreted as a shock onset when no patient complaint is forthcoming. Since the patients upon whom the measurements were made were, in general, long term hemodialysis patients, it is probable that some percentage would not complain about feeling light headed or slightly nauseous. A continuous blood pressure measurement could improve correlation.

A proposed system is shown in Fig. 1. This system adapts the instrumentation to a microcontroller, thereby incorporating the decision logic in a form which, with...