Control device for a monitor supervising a patient

Abstract

Involved is a system in which bodily conditions of the patient, such as his blood pressure, heartbeat, or the like, are electronically monitored. The monitor is required to result in the administration, preferably by intravenous injection, of a drug to the patient to correct any change in the supervised patient's condition indicating an emergency situation. The within invention is a control for the monitor providing two important safeguards. The first safeguard is that there will be an adequate refractory period, i.e., time for the drug to take effect, between administered doses to the patient. The second safeguard is that the medication dosage will not be administered to the patient until there is some assurance that the bodily function change which occurs in the patient is of an emergency nature, rather than merely an insignificant change which corrects itself without medication.

Description

The present invention relates generally to the use of an electronic monitor to supervise the bodily functions, such as blood pressure, heartbeat, and the like, of a patient, and to initiate an intravenous injection or other appropriate means of delivering to the patient an appropriate drug to correct any change in said supervised condition. More particularly, the invention relates to a control device for the monitor which provides important medical safeguards for the operation of the monitor.

A typical prior art patient-supervising monitor does little more than energize a light or operate a sound alarm which prompts the hospital staff to take whatever medical action is required to correct an emergency situation of the patient. The doctor or nurse then intravenously injects appropriate medication using a conventional syringe. Although automatic syringe devices are available, such as those of U.S. Pat. Nos. 3,456,649 and 3,623,474, these are seldom used. Yet, their use could result in more preciseness in the dosages administered, in greater promptness of administration, and other such benefits that accrue when using automatic, rather than manually, operated eqipment or devices. Undoubtedly, the minimal use of automatic syringe devices in conjunction with patient-supervising monitors is because there is insufficient control by the latter of the former to guarantee the safety of the patient.

Broadly, it is an object of the present invention to provide an improved control for a patient-supervising monitor overcoming the foregoing and other shortcomings of the prior art. Specifically, it is an object to impose safeguards on the operation of the monitor such that it does not cause an intravenous administration of a drug unless there is an actual emergency situation involving the patient, and following said initial administration, the succeeding dosage occurs only after the lapse of an appropriate refractory period, i.e., a period during which the administered drug causes the effect desired on the patient.

A control for a patient-supervising monitor demonstrating objects and advantages of the present invention includes a timer electrically connected to continuously receive from the monitor an input signal for a time interval that is of a duration to minimize any false indication of an emergency situation, and only thereafter transmits a signal resulting in the administration of a correcting drug. Also after the transmission of said signal, said timer is rendered incapable of sending a successive signal until the lapse of another time interval, which is selected in relation to the refractory period for the medication involved.

The above brief description, as well as further objects, features and advantages of the present invention, will be more fully appreciated by reference to the following detailed description of a presently preferred, but nonetheless illustrative embodiment in accordance with the present invention, when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 diagramatically illustrates the functions that are performed by the control device hereof for a monitor which is in supervising relation to a patient; and

FIG. 2 is a circuit diagram which illustrates details of said control device.

FIG. 1 diagramatically illustrates a system in which bodily functions of a patient 10, such as his blood pressure, the functioning of his heart, and the like, are supervised by a monitor 12. That is, in a well understood manner, monitor 12, which may be any one of several commercially available electronic units, is appropriately connected in supervising relation to the patient 10 so that if there is, for example, a sudden irregularity in the heartbeat of the patient 10, an appropriate signal 14 is transmitted to the monitor 12. In response to the signal input 14, the monitor 12, in turn, produces a signal 16, which in most instances is of an electronic nature such as a pulse at a specified voltage. Heretofore, the pulse or signal 16 did no more than energize a light or a sound alarm which prompted the hospital staff to take whatever action was required to correct the emergency situation of the patient 10. In the example given, i.e., an irregular heartbeat, a doctor or nurse might administer lidocaine or other such drug in an effort to regulate the patient's heartbeat. The administration of this drug in most instances would be by a conventional syringe. However, it could also be administered by an automatic syringe 18, preferably one having the construction and mode of operation of that described in U.S. application Ser. No. 375,955, filed July 2, 1973, entitled "Medication Injection Device." While the foregoing is preferred, use can also be made of a medication-administering device 18 of the general type and class described in U.S. Pat. Nos. 3,456,649 and 3,623,474. For present purposes it suffices to note that the device 18 is operated by an appropriate electronic signal or pulse 20 which commences its operation during which the device 18 causes an intravenous injection of medicine, such as the previously noted drug lidocaine, which corrects the emergency situation of the patient.

In accordance with the present invention, there is provided a control device, or so-called interface unit, generally designated 22, for the monitor 12. Specifically, device 22 controls the manner in which the monitor 12 actuates the automatic medication-administering device 18 to correct emergency situations of the patient 10. Using the previously noted assumed situation in which monitor 12 senses a heartbeat irregularity in the patient 10, which, in turn, calls for the administration of lidocaine, there are two requisites or conditions which should be imposed in any system involving the monitor 12 in order for said system to be medically sound. It is these two conditions which are imposed by the interface control device 22 of the present invention on the monitor 12, all as will now be fully explained.

The actual time in which the medication is delivered to the patient 10 by the automatic syringe 18 may be only a matter of minutes. However, it may be medically necessary after the delivery of this medication that another dosage not be delivered for a much longer period of time in order to allow the administered dosage to have the necessary effect on the patient's body and bodily functions. Thus, in the case of an irregular heartbeat, it is generally understood that successive dosages of lidocaine should have an intervening interval, known as the refractory period, of approximately 20 minutes. As will be described in greater detail subsequently herein, it is therefore one function of the control device 22 that after operation of the medication-administering device 18, that said operation be followed by a refractory period of any selected interval before a successive operation can occur. As noted, a refractory interval of 20 minutes would be proper for the drug lidocaine. However, in a situation where the patient is in an acute hypertensive condition, and the monitor 12 is supervising the blood pressure of the patient 10, a change in the patient's blood pressure would indicate an emergency situation for which an appropriate drug would be administered, and that drug may further be required to be continuously administered until there is a favorable change in the blood pressure condition of the patient. Thus, in this instance the refractory period is zero.

In addition to proper allowance for a refractory period, it is necessary that the control device or interface 22 hereof also be capable of eliminating or minimizing any false indication of an emergency situation involving the patient 10. For example, in a case where the monitor 12 is supervising the blood pressure of a patient 10, a mere change in the position of the patient, from a prone to a sitting-up position, could cause a momentary change in the patient's blood pressure. This change, however, is not medically significant and consequently should not, in a properly functioning system, initiate any corrective action, i.e., it should not result in the commencement of the device 18 insofar as the delivery of drugs by it to the patient. In a manner which will be described in detail subsequently, it is therefore another important function of the control device 22 hereof to minimize the occurrence of any false indications of an emergency situation involving the patient 10.

The interface or control device 22 hereof includes a selected voltage generator 24, a first timer 26, a second timer 28, and a control unit 30 which is operated by the second timer and exercises control over the operation of the first timer 26. The manner in which the foregoing components of the interface 22 operate will become apparent as the description proceeds.

The selected voltage generator 24, as the name implies, functions by emitting an electronic signal 32 of any selected specific voltage, such as for example, 5 volts. The five-volt pulse 32 is emitted continuously by the generator 24 as long as the generator receives an input signal 16. It should be noted that the signal 32 is at a selected five volts even though the input signal 16 is at a greater or lesser voltage. This functioning of the generator 24 is readily understood and can be readily obtained from any number of commercially available generators which emit an output signal at any selected voltage. One such commercially available model used with good results in accordance with the present invention is that available from Signetics, Inc., of Sunnyvale, Calif. This model advantageously utilizes a zenor diode voltage clipping circuit and a Schmidt trigger to produce the five volt output signal 32 for as long as there is an input signal 16 to the generator.

Reference should now be made to the circuit diagram of FIG. 2 in order to better understand how the first timer 26 utilizes the 5 volt signal input 32 to achieve the two essential operating conditions for the system previously alluded to. Timer 26 includes a variable resistor 34 and a capacitor 36, the latter being deemed fully charged when the voltage across its plates reaches the value of nearly five volts of the input signal 32. It is helpful at this point in the description to refer to a mechanical analogy in regard to the operation of the timer 26. Specifically, electron flow or current may be analogized to a flowing stream, the variable resistor 34 to a valve which regulates the amount of fluid which is permitted to flow past a constriction, and the capacitor 36 to a container or receptacle having a specified volume. Thus, depending on the setting of the variable resistor 34, there will be a certain current flow 32 through the resistor 34 that will take a specified amount of time to "fill" the capacitor 36, or to impress the rated 5 volt charge on this component. It is only after this interval of time has elapsed, that the timer 26 will produce an output signal 38 of 5 volts which ultimately results in the operation of the automatic syringe 18 in a manner which will soon be described. From what has been described thus far, however, it should be readily appreciated how the timer 26 imposes a time interval between the input of the signal 32 into the timer 26 and the generation therefrom of an output signal 38. As a consequence, the timer 26 is effective in minimizing operation of the medication-administering device 18 except when required to rectify or correct a real emergency situation involving the patient 10. Specifically, the variable resistor 34 is set at that setting which requires an appropriate time interval before the signal 38 is produced by the timer 26, and this contributes to eliminating any false indications of emergency. What this actual time interval is will depend on the bodily function being supervised by the monitor 12 and the medical situation that the patient finds himself in. For example, if it is the blood pressure that is being supervised by the monitor 12, a change in this condition which occurs only for a short duration is probably symptomatic of the patient merely changing his bed position, i.e., getting up from a prone position, rather than an emergency situation requiring the administration of a correcting drug. Thus, by setting the resistor 34 so that the intervening time interval is three minutes that a continuous signal 32 must be received by timer 26 before it produces an output signal 38 this imposed condition will, for all practical purposes, eliminate any false indications of a patient emergency situation.

Reference should now be made again to FIG. 1 for a continuation of the description of the mode of operation of the interface 22. Assuming that the signal 32 input into the first timer 26 is for a duration which is symptomatic of an emergency condition in the patient 10, this will result, in the manner just described, in the generation by timer 26 of an output signal 38 which is transmitted to the second timer 28. Timer 28 may be any one of several commercially available electronic timers, one such suitable timer being available from RCA, of Harrison, N.J. Upon the receipt of the input signal 38 by the timer 28, three events occur. The first is the generation by the timer 28 of the previously noted signal 20 which is transmitted to the medication-administering device 18 and which results in its dose-delivering operation. Typically, this might be achieved in a comparatively short interval, such as 2 minutes. Simultaneously with this, the second timer 28 also commences its own timing operation. In the example given, the interval of this operation is 20 minutes or the equivalent of the refractory period for the drug lidocaine which it was assumed was being administered by the device 18 to the patient 10. A third event required of the timer 28 is to impose an operating condition on the system which, in effect, renders it impossible for another output signal 38 to be transmitted to the timer 28. This must be prevented for the 20 minute refractory period, since any output signal 38 correspondingly results in signal 20 causing operation of the device 18. To achieve this functioning in the timer 28, it is provided that in response to the input to it of the signal 38 that timer 28 emit an electronic signal or pulse 40 which is transmitted to the control 30 for the first timer 26. Referring to FIG. 2, it is shown that the first timer control 30 is, in effect, a short circuit consisting essentially of a transistor, or as shown a triac 42 which is connected in short circuit relation to the capacitor 36. Signal 40 is transmitted to the biasing plate of the triac 42 and is effective in placing it in charging condition, thereby completing the connection of circuit 44 to ground and resulting in an alternate path for the electronic flow of the signal 32 exiting from the variable resistor 34. As generally understood, under these circumstances it is not possible to charge the capacitor 36, and therefore another output signal 38 will not be generated by the first timer 26 until the signal 40 from the second timer is discontinued. Naturally, signal 40 is continued for the duration of the refractory period for the drug being administered to the patient 10, and thus the first timer 26 is rendered inoperative for said refractory period. In this way, the interface or control device 22 imposes a time interval, corresponding to the refractory period for the medication involved, between successive generations by the first timer 26 of signals 38.

From the foregoing description, it should be readily appreciated that the interface or control device 22 thus contributes to a system, involving a monitor 12 which supervises the bodily functions of a patient 10, two important and significant safeguards. The first safeguard is that there will be an adequate refractory period between administered doses to the patient. The second safeguard is that the medication dosage will not be administered to the patient until there is some assurance that the condition which occurs in the patient requiring said medication is of a sufficient duration to indicate an emergency medical situation, rather than merely a temporary change in the supervised bodily function which is of a non-emergency status.

A latitude of modification, change and substitution is intended in the foregoing disclosure, and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

Claims

What is claimed is:

1. In a system including a monitor operatively arranged to supervise the blood pressure and like conditions of a patient and in response to changes in said supervised conditions to operate a medication-administering device for said patient, a control device for said monitor comprising means for generating a selected voltage signal in response to a signl input thereto from said monitor, a first timer electrically connected to continuously receive said selected voltage signal as an input thereto for a time interval necessary to charge a capacitor to the value of said selected voltage, means operated by said first timer when said capacitor thereof achieves said voltage charge to start the operation of said medication-administering device, and a second timer operated simultaneously with said medication-administering device for a selected time interval and effective to prevent any successive operation of said first timer until completion of said selected time interval, whereby an initial medication dosage is delivered to said patient by said medication-administering device only after the lapse of said time interval of said first timer so as to minimize any false indication of an emergency situation and a succeeding dosage is delivered only after the lapse of said time interval of said second timer which is selected in relation to the refractory period for the medication involved.

2. An improved control device for a patient-supervising monitor as defined in claim 1 including means for selectively varying the time intervals of operation of said first and second timers independently of each other.

3. An improved control device for a patient-supervising monitor as defined in claim 2 wherein said second timer operates a circuit in shorting relation to said capacitor of said first timer to prevent any successive operation of said first timer until completion of the interval of timing operation of said second timer.

4. An improved control device for a patient-supervising monitor as defined in claim 3 wherein said simultaneous operation of said second timer and of said medication-administering device is initiated by an electronic pulse transmitted from said first timer to said second timer, said transmitted pulse being used by said second timer to initiate its own operation and also that of said medication-administering device.

5. An improved control device for a patient-supervising monitor as defined in claim 4 wherein said transmitted pulse to said second timer is also used by said component to commence said operation of said shorting circuit for the capacitor of said first timer.

6. In a system including a monitor operatively arranged to supervise the blood pressure and like conditions of a patient and in response to changes in said supervised conditions to operate a medication-administering device for said patient, a control device for said monitor comprising means for generating a selected voltage signal in response to a signal input thereto from said monitor, a first timer electrically connected to continuously receive said selected voltage signal as an input thereto for a selected time interval preparatory to emitting a control signal, means operated by said control signal of said first timer to start the operation of said medication-administering device, and a second timer operated simultaneously with said medication-administering device for a selected time interval and effective to prevent any successive operation of said first timer until completion of said selected time interval, whereby an intitial medication dosage is delivered to said patient by said medication-administering device only after the lapse of said time interval of said first timer so as to minimize any false indication of an emergency situation and a succeeding dosage is delivered only after the lapse of said time interval of said second timer which is selected in relation to the refractory period for the medication involved.

7. An improved control device for a patient-supervising monitor as defined in claim 6 wherein said first timer includes a capacitor and is electrically connected to continuously receive said selected voltage signal as an input thereto for a time interval necessary to charge said capacitor to the value of said selected voltage before emitting said control signal.

8. An improved control device for a patient-supervising monitor as defined in claim 7 wherein said second timer operates a circuit in shorting relation to said capacitor of said first timer to prevent any successive operation of said first timer until completion of the interval of timing operation of said second timer.