Cardiovascular Test Station Pressurometer Interface System

Abstract

A pressurometer interface circuit operative to provide serial, binary data representative of patient pulse rate and patient systolic and diastolic blood pressures. In response to automatic inflation and deflation of a cuff the interface circuit receives in parallel a plurality of bilevel signals, each associated with a given cuff pressure and indicating whether a Korotkoff sound response is detected at the cuff pressure. The bilevel signals are converted, for efficient data communication, to serial binary coded data representative of the boundaries of the range of pressures during which Korotkoff sounds are exhibited. Further binary data is generated indicating patient pulse rate as interpreted from the Korotkoff sounds during deflation.

Description

FIELD OF THE INVENTION

This invention relates to electronically automated medical examination of patients and in particular to data interfacing for pressurometer testing.

BACKGROUND OF THE INVENTION

Modern medical examination procedures are placing increasing reliance upon electronics for gathering the response of patients to a variety of new and traditional patient tests. One of the traditional tests being performed electronically today is the reading of patient pulse rate and blood pressure. Several units are commercially available, such as the Avionics Research Products, Pressurometer Model 1900, which provide a visual display of the correlation between patient blood pressure and the existence of patient Korotkoff sounds. Korotkoff sounds are noise generated by blood flowing through vessels which are partially constricted in response to the degree of inflation of an inflatable cuff wrapped around a patient's extremity. Patient systolic and diastolic pressure levels, the medically significant parameters of a patient's blood pressure, are indicated by the largest and smallest pressures for which Korotkoff sounds are detected by the pressurometer.

While such a pressurometer greatly simplifies the task of obtaining patient blood pressure data, manual reading of the pressurometer scales and manual recording of pressure data is still required. This additional work reduces the efficiency of blood pressure testing and increases its cost as well as the chance of error. A need clearly exists for an electronic system capable of directly converting pressurometer output format into machine readable binary signals representative of patient diastolic and systolic pressure. At the same time, significant efficiency in medical data taking can be gained if patient pulse rate can be determined during the blood pressure test to avoid the necessity of connecting additional apparatus to the patient to sample this pulse rate. Finally, since pressurometer data may have to be transmitted over a distance through a data link, data should be presented to the data link in a form allowing for efficient communication.

SUMMARY OF THE INVENTION

An interface circuit is provided operative with available pressurometer units of the type which correlate patient blood pressure with the presence of Korotkoff sounds, the interface circuit providing, in serial bit form, binary coded signals representing patient diastolic and systolic blood pressures and patient pulse rate for subsequent machine data processing.

In pressurometers of the type indicated, a plurality of selectively illuminated lamps are provided with each lamp corresponding to a particular patient blood pressure level. The pressurometer is operative to cycle an inflatable cuff through an inflation and deflation sequence and during deflation the selectively illuminated lamps are lighted in response to detection of Korotkoff sounds at the patient pressure level corresponding to each lamp.

Also during cuff deflation detected Korotkoff sounds are pulse shaped and encoded into a uniquely recognizable serial, binary sequence and conveyed to a station console and associated central processor in real time sequence to indicate patient pulse rate.

After complete deflation and evacuation of the cuff, the interface circuit switches to a blood pressure mode in which the status of the pressurometer lamps are sequentially sampled to enable the generation of binary coded signals representing diastolic and systolic pressure levels. The interface circuit performs this function by sequentially sampling the status of each lamp and detecting the existence of a different lamp status between adjacent pressure levels, indicative of a transition between Korotkoff sounds and no Korotkoff sounds at the corresponding pressure level. Upon the detection of a lamp status transition, the identity of a lamp adjacent the transition is automatically read out in serial binary form and conveyed to the central processing unit via the test station console.

DESCRIPTION OF THE DRAWINGS

These and other features of the invention will be more fully understood by reference to the following detailed description of a preferred embodiment, presented for purposes of illustration and not by way of limitation and to the accompanying drawings of which:

FIG. 1 is a pictorial view of a pressurometer interface circuit in a cardiovascular test station; and

FIG. 2 is a partial schematic and partial block diagram of an interface circuit according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the realm of medical science the taking of patient blood pressure information is achieved by strapping an inflatable cuff around a patient's arm, or other extremity, and inflating the cuff to the point where the circulation of arterial blood flow in vessels is inhibited. Cuff pressure is then reduced at a slow, controlled rate until the attending physician detects, through the use of a stethoscope, the presence of Korotkoff sounds indicating the beginning of blood flow through the constricted blood vessels. The pressure at which Korotkoff sounds are first noticed is known as the systolic blood pressure level. With further cuff deflation, a pressure is reached where Korotkoff sounds are last noticed, and this pressure is termed the diastolic pressure level.

Referring now to FIG. 1, there is shown a cardiovascular test station set up for measuring patient blood pressure and pulse rate and utilizing a pressurometer interface circuit 12 according to the invention. In the example of FIG. 1, a patient 14 has an inflatable cuff 16 wrapped around his arm and connected to a pressurometer 18 of the type exemplified by Avionics Research Products, Pressurometer Model 1900. A pressure pump and a release valve, not shown, within the pressurometer 18, are connected through pneumatic tubing 20 to the cuff 16. Within the cuff 16 a detector 22 senses blood vessel Korotkoff sounds and conducts electrical representations thereof over a line 24 to the pressurometer 18.

In operation, the pressurometer 18 is automatically, or manually, cycled to provide inflation pressure to the cuff 16, pressurizing it to a point where all blood flow through the vessels of the arm is eliminated. The pressurometer 18 then deflates the cuff 16 at a predetermined rate until the cuff is exhausted.

During deflation of the cuff 16, detection circuitry within the pressurometer 18 samples the signal on line 24 for the existence of Korotkoff sounds at predetermined pressure levels, and if a Korotkoff sound is detected at that pressure level a corresponding lamp, of a set of lamps 26 on the face of the pressurometer 18, is illuminated. After an inflation and deflation cycle has been completed by the pressurometer 18, a series of lamps in the set 26 will be illuminated denoting the range of patient blood pressures during which Korotkoff sounds were detected.

By appropriate connection within the pressurometer 18, a plurality of electrical lines 28 are provided from the pressurometer 18 to the interface circuit 12, with each line carrying a signal representative of the status of a corresponding lamp in the set 26. Additionally, a signal representative of the detected Korotkoff sounds is conducted from the pressurometer 18 over a line 30 to the interface circuit 12, a signal indicating that the cuff is deflating is fed to the interface over line 31, and a signal indicating cuff exhaustion is provided from the pressurometer 18 over a line 32 to the interface circuit 12.

The pressurometer interface circuit 12 converts the plurality of inputs containing pulse rate and pressure information into serial data and conveys it, via a single line 34, through a data link 35, to a cardiovascular station console 36. The data link 35 may include substantial distance and it is, therefore, an economic benefit that data is in serial bit form and only necessitates a single data line 34. Supervisory and clock signals are provided by preferably a single line 38 from the console 36 to the interface circuit 12.

Referring to FIG. 2, and the more detailed description of the interface circuit 21, the plurality of lamp condition lines 28 are conducted to an attenuator and inverter circuit 40 which provides signal level normalization of the lamp status signals through a plurality of corresponding voltage dividers 42 and transistor driving circuits 44 in order to match level requirements for the interface circuit 12. The plurality of normalized lamp condition signals are bunched in groups of, for example, six signals, each group leading into one of a plurality of primary multiplexer circuits 46 through 56. An output from each primary multiplexer 46-56 is conducted to a secondary multiplexer circuit 58 along with an end of test signal. The output of the secondary multiplexer 58 is conducted to a sample and temporary hold circuit 60 and to one input of an exclusive OR gate 62. The output of the sample and hold circuit 60 is conducted to a second input of the exclusive OR gate 62. The output of the exclusive OR gate 62 is conducted to a junction circuit 64 which in turn passes the signal of gate 62 to a gate 66 that feeds the data line 34 to the test station console 36 via data link 35.

The supervisory signal on line 38 from the console 36 comprises a clock signal conducted, through an amplifier 67, to a binary counter 68 that counts through a plurality of steps in a predetermined count including one step for each of the lamps in the pressurometer 18 and at least one additional step for control purposes. A further counter 70 receives the clock signal on line 38 and provides a binary count through a predetermined number of steps for each step of the counter 68. The binary states of the counter 70 are fed in parallel to an address multiplexer 72 along with the binary states, in parallel, from the counter 68. The binary states of the counter 68 are also applied to the primary multiplexers 46 through 56 and to the secondary multiplexer 58. The counter 68 has a reset and enable signal provided to it over line 32.

When appropriately reset and enabled, the counter 68 operates to count through the steps of its predetermined count in response to the clock signal on line 38. Each of the primary multiplexers 46 through 56 is adapted to recognize a predetermined binary state in the count of counter 68 in an exclusive range for each primary multiplexer and to provide an output signal representative of the one of its inputs which corresponds to the particular binary state of the counter 68. The secondary multiplexer 58 is adapted to recognize the exclusive ranges of binary states from the counter 68 and provide at its output a signal representative of the signal input thereto from the particular one of the primary multiplexers in the corresponding exclusive range of binary states recognized. In this fashion the primary multiplexers 46 through 56 and the secondary multiplexers 58 operate as a single pole multiple throw switch cycling in correspondence with the states of the counter 68 to sample each of the plurality of inputs to the primary multiplexers and to provide at an output of the secondary multiplexer a signal representing the status of the input sampled.

The output of the multiplexer 58 is sampled by the sample and hold circuit 60 and held for the duration of one step in the counter 68 such that its output is representative of the condition of the lamp previously sampled. The exclusive OR gate 62 receives as inputs the current and previously sampled lamp conditions and provides an output indicating when its two inputs differ. The two inputs differ in response to a transition between lighted and unlighted lamps and correspondingly a transition between the existence of Korotkoff sounds and non-existence of Korotkoff sounds.

The output of the exclusive OR gate 62, indicating this transition, is conducted through the junction circuit 64 to the gate 66 where it causes the gate 66 to respond to and pass the signal from the address multiplexer 72. The address multiplexer 72 operates to provide, as its output to the gate 66, a sequence of binary signals representative of the state of the counter 68 at the time of detected transition. The counter 70 effects the sampling of the state of the counter 68 by causing the multiplexer 72 to sample each of the binary states of counter 68 in correspondence with the count of the counter 70. The output of the multiplexer 72, in response to a transition, comprises an initial bit of predetermined information followed by binary signals indicating the state of binary counter 68. The output of the sample and hold circuit 60 is also applied to the multiplexer 72 which encodes that signal in the last bit of data provided from the multiplexer.

The end of test signal applied to secondary multiplexer 58 causes detection of an artificial transition beyond the pressure range of the pressurometer and thus produces a signal which is communicated to the console 36 to indicate the completion of a test. The console 36 operating with a central processing unit or computer 74 recognizes the end of test address and operates to preclude further testing for that patient unless an override is activated. The interface can be signaled to stop testing, by, for example, removing the clock signal.

The Korotkoff sounds and the cuff deflation and exhaustion status signals from the pressurometer 18 are applied respectively over lines 30, 31 and 32 to the circuits of FIG. 2. The Korotkoff sounds on line 31 are applied to a gate 82. The cuff deflation signal on line 31 is applied to a detector 84 which provides an enable signal to gate 82 when the cuff is in the deflation portion of an inflation-deflation cycle. The Korotkoff sounds are conducted from gate 82 during deflation only, to eliminate noise interference from rapid inflation, and applied to a pulse shaper circuit 86 which also receives the clock signal and produces an output pulse of appropriate shape to reflect patient pulse which it represents synchronized with the clock signal on line 38. This signal is conducted to junction circuit 64 and thence to gate 66. The signal from multiplexer 72 to gate 66 is normally at an enable level and thus permits passage of the clocked pulse signals through gate 66 to console 36 to indicate patient pulse.

The cuff exhaustion signal on line 32 is fed to counters 68 and 70 and resets the counters 68 and 70. Prior to exhaustion, this signal by application to counters 68 and 70 prevents counter operation and thus inhibits system operation but after cuff exhaustion by resetting counters 68 and 70 enables the system operation described above and thereby causes the lamps of the pressurometer 18 to be sampled and read out through gate 66.

As shown in FIG. 1 and FIG. 2 the console 36 is a central control system for a cardiovascular station which includes a manual or automatic tonometer 90 and a manual or automatic electrocardiograph 92 communicating with the console 36 to provide patient data in response to control signals. All tests are conveniently performed with the patient in a horizontal position. As shown in FIG. 2 the central processing unit 74 is operative in conjunction with the console 36 to receive patient data and perform appropriate calculations thereon to provide indicia of patient cardiovascular condition. In response to data on patient blood pressure and pulse rate, the console 36 communicates this data to the central processing unit 74 which, after calculation of blood systolic and diastolic pressures and pulse rate, returns this information to the console for presentation on a display 96. An enter button 98 is provided on the console 36 to cause the central processing unit 74 to record the displayed data as part of the patient's medical information in response to activation of the entry button 98 when the test operator is satisfied with the appearance of the data. A repeat button 100 is provided to enable recycling of the test if the data is unsatisfactory. When the button 100 is depressed, the clock signal is reapplied and the test is recycled in response to activation of a cycle button on the pressurometer.

Having described a preferred embodiment of the present invention, it will occur to those skilled in the art that modifications and alterations can be made to the specific disclosure while accomplishing the spirit of the invention. It is accordingly intended to limit the scope of the invention only as indicated in the following claims.

Claims

What is claimed is:

1. A pressurometer interface circuit operative to provide patient diastolic and systolic pressure data from a pressurometer of the type having a cyclically inflatable cuff and a plurality of bilevel signals, each associated with a particular cuff pressure, and being in one of the two levels in response to the presence of Korotkoff sounds at the corresponding cuff pressure and in the second of the two levels in response to the absence of Korotkoff sounds at the corresponding pressure, said interface circuit comprising:

means for receiving said plurality of bilevel signals;

means for sequentially sampling the level of each of said received bilevel signals to provide a sequence of sampled signals each representing a corresponding bilevel signal;

said sampling means including means for providing an indication of which of said bilevel signals is sampled;

means for detecting a difference in signal level of adjacent signals in said sequence of sampled signals; and

means responsive to detection of a difference in signal level for generating an address signal in serial bit form to represent the sampled, adjacent bilevel signals detected as different, thereby to provide output indicia of said patient diastolic and systolic pressure data.

2. The pressurometer interface circuit of claim 1 further comprising:

means for adjusting the signal level of said received plurality of bilevel signals to a predetermined range of levels compatible with said interface circuit.

3. The pressurometer interface circuit of claim 1 further including:

means responsive to deflation of the pressurometer cuff for generating pulses coincident with patient Korotkoff sounds; and

means responsive to cuff exhaustion for inhibiting the generation of said pulses and for enabling sampling by said sampling means of said plurality of bilevel signals.

4. In combination with a pressurometer interface circuit of the type claimed in claim 1 further apparatus including:

means for transmitting said generated serial bit form address signal;

a test station console for receiving said address signal; and

a central computation facility in communication with said console for data processing of said address signal as received by said console to provide diastolic and systolic pressure data;

said console, in association with said central computation facility, having means responsive to said diastolic and systolic pressure data from said central computation facility for displaying said data at said console;

said console further having means for causing said central computation facility to record said diastolic and said systolic pressure data in response to activation thereof.

5. The apparatus and pressurometer interface circuit of claim 4 further including means for causing recycling of said interface and pressurometer for additional testing in response to activation thereof.

6. The pressurometer interface circuit of claim 1 wherein said sampling means further includes:

a multiplexer system receiving said plurality of adjusted, bilevel signals at parallel inputs thereof; and

a counter operating at a predetermined frequency to count through a predetermined number of steps;

said multiplexer system operating in response to the counting of said counter to provide at an output of said multiplexer system said sequence of sampled signals;

each step in the count of said counter causing said multiplexer to provide at the output thereof one signal of said sequence of sampled signals in correspondence with that step in the count.

7. The pressurometer interface circuit of claim 1 wherein said address signal generating means includes means for providing an indication in said address signal of the level of one said adjacent, different bilevel signals.

8. The pressurometer interface circuit of claim 1 wherein said sampling means includes means for providing a signal of a predetermined level in said sequence to indicate the end of said sequence.

9. An interface circuit operative in association with a blood pressurometer of the type having a blood flow restricting inflatable cuff cyclable through an inflate and deflate sequence and adapted to sense the Korotkoff sounds during at least a portion of the sequence, said pressurometer further including a plurality of two display state elements each associated with a particular pressure in a range of pressures for said cuff, said pressurometer adapted to cause each of said two state elements to change from a first display state to a second display state in response to the existence of said Korotkoff sounds at the corresponding pressure level of each said element during deflation of said cuff, said interface circuit comprising:

means for sensing the state of each of said plurality of two state elements;

means for developing a plurality of bilevel signals, each representative of the sensed state of a corresponding two state element;

means for adjusting each said bilevel signal in signal level to a predetermined data logic scheme;

multiplexer means for receiving each of said plurality of bilevel signals on one of a plurality of parallel inputs;

a binary counter operative to count at a predetermined rate through a predetermined number of binary steps;

said multiplexer means being operative in response to the count of said counter to provide as an output signal, a signal representative of the level of an input to said receiving means corresponding to the count of said counter in order to provide at the output of said multiplexer means a sequence of signals representative of the signal level at each of said plurality of parallel inputs to said multiplexer means;

means for sampling and retaining for approximately one step of said counter each signal in said sequence of signals at the output of said multiplexer means;

means for comparing each signal in the sequence of signals from said multiplexer means with the signal retained by said sampling and retaining means;

said comparing means providing an indication of a difference between adjacent signals at the output of said multiplexer means; and

means for generating a signal representative of the count of said binary counter coincidental with the indication by said comparing means of different adjacent signals in said sequence.

10. The interface circuit of claim 9 further including:

means for sensing Korotkoff sound signals from said pressurometer;

means for producing a signal representative of said sensed Korotkoff sound signals;

means for sensing the state of inflation of said cuff by said pressurometer;

means for enabling the production of said signals representative of Korotkoff sound signals only during relatively noise free portions of an inflate-deflate cycle; and

means for inhibiting said counter whenever said sensed cuff status indicates partial or complete cuff inflation;

said counter being operative in response to said sensed cuff status to commence counting at a predetermined count whenever said cuff status signal indicates cuff exhaustion after an inflate-deflate cycle.

11. The interface circuit of claim 10 further including:

means for indicating the inflation status of said cuff;

means responsive to the indicated deflation of said cuff and the sensed Korotkoff sounds for producing patient pulse signals in serial bit form; and

means for alternatively transmitting said generated and said produced signals.

12. The interface circuit of claim 9 wherein said generating means further includes:

second multiplexer means for receiving the binary states of said counter;

a second counter counting at a predetermined higher rate than the first mentioned counter;

said second multiplexer means including means responsive to the count sequence of said second counter for providing as an output a sequence of signals representative of the binary states of said first counter as applied to said second multiplexer means.

13. The interface circuit of claim 9 further including means for causing said generating means to generate an end of sequence signal when said binary counter has counted through said predetermined number of binary steps.

14. The interface circuit of claim 9 having apparatus associated therewith including:

a serial bit data link

means for applying said generated signal to said data link;

control means for recovering said generated signal from said data link and for applying a supervisory signal to said data link;

said interface circuit including means for recovering said supervisory signal from said data link and for applying said recovered supervisory signal to control said binary counter;

said control means having means for determining and displaying patient cardiovascular data in response to said recovered generated signal and further including means having first and second states to record said data in said first state and to enable, with said supervisory signal, said interface circuit to generate further signals in said second state.

15. The interface circuit and apparatus of claim 14 further including:

a tonometer test unit; and

an electrocardiograph test unit;

means for interconnecting said units with said control means for processing received test information.