CN101460092B - Prediction of rapid symptomatic blood pressure decrease - Google Patents

Abstract

This invention relates to the prediction of a rapid symptomatic drop in blood pressure in a subject, for example, during medical treatment or when operating an aircraft. To achieve this, pulse shape parameters ( _PS ) of a peripheral body part (105) of the subject (P) are registered by a pulse oximeter (110), wherein the pulse oximeter (110) is adapted to detect changes in light response in the blood vessels. An initial pulse amplitude measurement is calculated based on the pulse shape parameters ( _PS ) received at a first moment. During measurement periods after the first moment, individual pulse amplitude measurements are calculated based on each of the multiple received pulse shape parameters ( _PS ). For each pulse amplitude measurement during the measurement period, it is further investigated whether the measurement meets the criteria relative to the initial pulse amplitude measurement. If the criteria are found to have been met, an alarm trigger signal (α) is generated.

Description

Prediction of rapid symptomatic blood pressure drop

technical field

The present invention generally relates to detecting the onset of a rapid (acute) symptomatic drop in a subject's blood pressure. In particular, the invention relates to an alarm device according to the preamble of claim 1 , a medical system according to claim 12 , a method according to the preamble of claim 13 , a computer program according to claim 23 and a medical system according to claim 24 . computer readable media. the

Background technique

There are now many situations where it is important to detect potential hypotension and, if possible, avoid its actual occurrence, for example when performing manual blood purification. The human body is made up of about 60% water - an important level for survival. While it is undoubtedly possible to supply the body with new water, draining excess water is a major problem for kidney patients. The normal job of the kidneys is to remove excess fluid, such as water, urea, and other waste products, from the blood. The urine produced is sent to the bladder and eventually leaves the body when you urinate. A second task of the kidneys is to regulate eg acid and base balance. As the kidneys are disturbed, so will most of the major body organs, a complication called uremia. If uremia is not treated, it will lead to death. Uremia can be treated with a kidney transplant, or several blood treatments outside or inside the body. the

During artificial blood purification such as extracorporeal blood therapy, patients often suffer from symptomatic hypotension, characterized by a drop in blood pressure with symptoms in the form of cramps, nausea, vomiting and sometimes fainting. Not only is this situation stressful for the patient, but it requires a great deal of attention from the staff monitoring the treatment. Therefore, it would be highly desirable to detect the onset of symptomatic hypotension and prevent its occurrence during such blood therapy. the

However, there are examples of other situations where predicting rapid symptomatic hypotension and, if possible, preventing its occurrence is life and death. For example fighter pilots are often subjected to forces that put the pilot at risk of passing out. However, operators of other types of vehicles, aircraft, and machines may also require similar monitoring to reduce risk to operators, other persons, and cargo of various materials. the

Published US Patent Application 2004/0254473 describes a laser blood flow meter and system for monitoring biological data of a person. The laser blood flow meter measures individual blood flows flowing in different quarters of a biological structure by irradiating a laser beam to the biological structure and detecting the resulting scattered beam. Based on the detected light, it is then determined whether the person to whom the biological structure belongs is in a serious condition. For example, such a determination may be based on a decrease in blood flow relative to a previously recorded criterion, a decrease in the amplitude of the blood flow waveform relative to a criterion, and an increase in heart rate. the

However, there is currently no solution that, on the one hand, provides a fast and reliable low blood pressure alert, and on the other hand is cost-effective and simple to implement. the

Contents of the invention

It is therefore an object of the present invention to alleviate the above-mentioned problems and thereby achieve an uncomplicated solution by means of which the onset of acute symptomatic blood pressure reduction can be detected at a point in time when any of its effects can still be avoided. the

According to an aspect of the invention, the object is achieved by the initially introduced alarm device, wherein the pulse recording means comprises a pulse oximeter adapted to register a pulse shape parameter based on a change in light response in at least one blood vessel of the subject. The control unit further comprises a processing unit adapted to calculate an initial pulse amplitude measure based on the pulse shape parameters received at the first instant and to store the initial pulse amplitude measure in a memory device associated with the control unit. During a measurement period after the first instant, the processing unit is adapted to calculate a respective pulse amplitude measurement based on each of the plurality of received pulse shape parameters. In addition, for each pulse amplitude during the measurement, the processing unit is adapted to investigate whether the measurement meets a decision criterion with respect to the initial pulse amplitude measurement. If such a criterion is found to be fulfilled, the processing unit is adapted to generate an alarm trigger signal. Accordingly, appropriate measures can be taken automatically and/or manually to avoid (or at least reduce the risk of) hypotension occurring. the

An important advantage of this design is that an early hypotension alert can be provided based on relatively small processing resources and a simple and cost-effective sensor. In addition, the sensors used are approved in the medical field and have a very well-installed functionality.

According to a preferred embodiment of this aspect of the invention, the processing unit is adapted to consider the decision criterion as met if: the checked pulse amplitude measurement for a given pulse shape parameter is below a threshold calculated based on the initial pulse amplitude measurement; And a predetermined amount (eg, 50-100%) of the pulse amplitude measurements of the pulse shape parameter received during the test period after the pulse shape parameter is given is below the threshold. the

Preferably, the test period is a time interval selected from the range extending from about 3 minutes to about 15 minutes, and more preferably, the test period is about 5 minutes long. Thus, depending on the threshold, the predetermined amount of pulse amplitude measurements required to meet the decision criteria, and the selected test period length, a low blood pressure alarm that is robust and reliable over widely varying subjects and applications can be obtained. the

According to another preferred embodiment of this aspect of the invention, the processing unit is adapted to calculate the threshold by normalizing the initial pulse amplitude measurement and dividing the normalized initial pulse amplitude measurement by a predefined denominator It is a value selected from the range of about 1.2 to about 5, for example. Thus, by choosing the threshold, the algorithm can be calibrated with respect to the length of the test period to obtain the desired balance between early and false alarms. However, generally relatively large denominators require relatively short test periods, and vice versa. the

According to a further preferred embodiment of this aspect of the invention, the processing unit is adapted to calculate a pulse amplitude measure during the measurement for any received pulse shape parameter by dividing the original measure by an initial pulse amplitude measure representing the value that has been determined by Normalized initial pulse amplitude measurement divided by a predefined denominator. Thus, an unbiased comparison with the initial state can be made. the

According to other preferred embodiments of this aspect of the invention, the device comprises auxiliary recording means adapted to repeatedly register bioimpedance parameters representing the degree of capillary constriction of the subject. Additionally, the processing unit is adapted to receive bio-impedance parameters and to investigate whether the bio-impedance parameters meet auxiliary alarm criteria. Also when this criterion is met, the processing unit is adapted to generate an alarm trigger signal. Thus, a complementary hypotension detection means is provided, and thus a more reliable function. the

According to another preferred embodiment of this aspect of the invention, the device is adapted to predict a rapid symptomatic drop in blood pressure in a subject undergoing blood therapy. Here, the processing unit is adapted to calculate an initial pulse amplitude measure based on the pulse shape parameters received in the initial phase of the blood therapy. Therefore, hypotension detection is based on reference values that are relatively unaffected by treatment. This further enhances reliability. the

According to another aspect of the invention, the object is achieved by a medical system adapted to perform blood therapy of a subject. In addition to the above mentioned alarm means, the system comprises a dialysis machine adapted to perform extracorporeal blood therapy of the subject. Thus, blood therapy and hypotension monitoring can be implemented in parallel in a simple manner. the

According to another aspect of the invention, the object is achieved by the method introduced at the outset, wherein the registration of the pulse shape parameters involves pulse oximetry. Thereby, a pulse shape parameter is determined based on a change in light response in at least one blood vessel of the subject. Additionally, the method includes calculating an initial pulse amplitude measure based on the received pulse shape parameters at the first time instant, and storing the initial pulse amplitude measure in the storage device. During measurements after the first time instant, pulse amplitude measurements are calculated based on each of a plurality of received pulse shape parameters. For each pulse amplitude measurement in the measurement period, it is investigated whether the measurement meets the decision criteria relative to the initial pulse amplitude measurement, and if so, an alarm trigger is generated. the

The advantages of the method and its preferred embodiments are evident from the above description with reference to the proposed alarm device. the

According to other aspects of the invention, this object is achieved by a computer program directly loadable into the internal memory of a computer, said computer program comprising software for controlling the above proposed method when said program is run on a computer. the

According to another aspect of the present invention, the object is achieved by a computer readable medium having a program recorded thereon, where the program is for causing a computer to control the above proposed method. the

Other advantages, advantageous features and applications of the invention will be apparent from the following description and appended claims. the

Description of drawings

The invention will now be described more precisely by means of the preferred embodiment disclosed as examples and with reference to the accompanying drawings. the

Figure 1 shows a schematic diagram of an alarm device according to an embodiment of the present invention,

Figure 2 shows a block diagram of a medical system according to one embodiment of the present invention,

Figure 3a shows a graph of an example of blood pressure variables of a first subject during blood therapy,

Figure 3b shows a graph of how the proposed first subject's pulse amplitude measurement varies over time,

Figure 4a shows a graph of an example of blood pressure changes in a second subject during blood therapy,

Figure 4b shows a graph of how the proposed second subject's pulse amplitude measurement varies over time,

Figure 5a shows a graph of an example of a third subject's blood pressure variation during blood therapy,

Figure 5b shows a graph of how the pulse amplitude measurement of the proposed third subject changes over time, and

Fig. 6 shows a flowchart of a general method for predicting rapid symptomatic blood pressure reduction according to the present invention. the

Detailed ways

We first refer to FIG. 1 , which depicts an alarm device 100 for predicting a rapid symptomatic drop in blood pressure in a subject P, according to one embodiment of the present invention. Apparatus 100 includes pulse recording devices 110 and 115, and control unit 120, respectively. the

The pulse recording device has a pulse oximeter 110 and preferably a separate sensor unit 115 . This unit 115 includes at least one light source and at least one photodetector, by means of which a pulse signal S is registered, the pulse signal S depending on where the sensor unit 115 is connected to the subject P (for example, at the finger, tongue, ear lobe, nose tip or In other extremities, in its skin or in the skin of any other body part) to describe changes in the light response in at least one blood vessel in the peripheral body part 105 of the subject P. The change in photoresponse preferably reflects a change in absorption of light emitted from said at least one light source. However, light reflection and/or light transmission can be studied equally well. In any case, the pulse oximeter 110 is adapted to register the pulse shape parameter P _PS based on the pulse signal S .

The control unit 120 is adapted to receive and process the pulse shape parameter P _PS . Specifically, the control unit 120 comprises a processing unit 128 adapted to store the pulse shape parameter P _PS received at the first instant t ₁ in the storage device 123 . The storage means 123 are either included in the control unit 120 or connected thereto, eg via a cable or a wireless connection. In any case, the processing unit 128 is adapted to calculate an initial pulse amplitude measurement PM1 based on the values stored in the storage means 123 .

Figure 3b shows an initial pulse amplitude measurement PM1 on a first subject exposed to extracorporeal blood therapy. Preferably, the initial pulse amplitude measurement PM1 is derived not only from a single pulse shape parameter P _PS but also based on the average of a number of such parameters registered during the initial measurement. The graph in Figure 3b represents the time t in minutes along the horizontal axis and the pulse amplitude measurement PM along the vertical axis.

In accordance with the present invention, processing unit 128 may determine the pulse magnitude measurement PM via one or more of the following strategies. For example, the difference between the maximum and minimum values of the pulse shape parameter P _PS registered during the pulse stroke can be calculated. Alternatively, the envelope of the pulse shape parameter P _PS can be detected, eg by computing a Hilbert transform. The pulse amplitude measure PM may also be determined using root mean square (RMS) measurements based on the pulse shape parameter P _PS . However, this requires prior calibration of the parameter values to zero mean.

Figure 3a shows a graph of the systolic blood pressure variable BP _s and the diastolic blood pressure variable BP _D of a first subject during treatment in mmHg, respectively. Blood pressure BP varied throughout the course of treatment. However, as shown in Figure 3b, hypotension did not occur. Apart from a slight dip around 245 minutes during the treatment, the pulse amplitude measurement PM also remained relatively flat.

During the measurement after the first instant _t1 (ie here starting from t=0), the processing unit 128 is adapted to calculate a respective pulse amplitude measurement PM based on each of a plurality of received pulse shape parameters P _PS . For each pulse amplitude measurement PM in the measurement period, the processing unit 128 is further adapted to investigate whether the measurement PM meets a decision criterion relative to the initial pulse amplitude measurement PM1. If such a decision criterion is found to have been met, the processing unit 128 is adapted to generate an alarm trigger signal a. It is assumed in turn that the alarm trigger signal α causes alarm A to be triggered in the alarm unit 125 of the control unit 120 itself, and/or in an external unit that receives the alarm trigger signal α. The pulse amplitude measurement PM and decision criteria will be described in detail below with reference to FIGS. 4 , 5 and 6 .

Fig. 2 shows a block diagram of a medical system 200 for performing blood therapy of a subject P according to one embodiment of the present invention. For this purpose, the system 200 comprises a dialysis machine 210 which may be adapted to perform extracorporeal blood therapy of the subject P, i.e. the machine 210 is adapted to withdraw contaminated blood _βC from the subject P and return purified blood _βP to the subject p. The system 200 also includes the above-mentioned alarm device 100 for predicting any rapid drop in blood pressure that is potentially unhealthy for the subject P. Thus, while purifying the subject P's blood, the alarm device 100 monitors his/her risk for the occurrence of acute symptomatic hypotension. In the event of an alarm signal α, monitoring staff can be informed and/or the dialysis machine can be controlled to adjust its treatment parameters in order to avoid a hypotensive situation. This adjustment is characterized by a feedback signal α from alarm device 100 to dialysis machine 210 .

Preferably, the control unit 120 (see FIG. 1 ) in the alarm device 100 is adapted to predict a rapid symptomatic drop in blood pressure in a subject P on the basis of an initial pulse amplitude measurement PM1 obtained from a time when the subject was relatively unaffected by the subject. The pulse shape parameter P _PS received during the initial phase of blood therapy when the therapy influences is calculated.

Returning now to Figure 4a, it can be seen that the graph legend shows a graph of how systolic blood pressure BP _S and diastolic blood pressure BP _D vary in mmHg per second during extracorporeal blood therapy. At time point t _h around 145 minutes into the treatment, the subject suffers from acute symptomatic hypotension. This event was predicted by a rapid decrease in BP in both systolic BP _S and diastolic BP _D.

With further reference to Fig. 4b, we will now explain how the proposed pulse magnitude measure PM and threshold T are calculated according to an embodiment of the present invention, and how the solution of these parameters is used to predict hypotensive events. the

The processing unit 128 of Fig. 1 is adapted to investigate whether a decision criterion is fulfilled with respect to the pulse shape parameter P _PS received during the measurement period. In this example, the measurement period starts at t=0 and continues throughout the time interval covered by the graphs of Figures 4a and 4b.

The processing unit 128 of the control unit 120 preferably calculates the threshold T as follows. First, the initial pulse amplitude measurement PM1 obtained at time t ₁ (ie here t=0) is normalized. In this example PM1=1, but technically any other reference value is conceivable. The normalized value is then divided by a predefined denominator, which can be any number between 1.2 and 5, such as 2. Therefore, the threshold T is obtained. Thus, assuming a predefined denominator of 2, T becomes 0.5, as shown in Figure 4b by the dashed line. During the measurement period after t1, the processing unit 128 calculates for each received pulse shape parameter P by dividing the original pulse amplitude measurement PM1 (which is derived from the pulse shape parameter P _PS received at the first time instant _t1 ) by the original pulse amplitude measurement PM1. _PS calculates the normalized pulse amplitude measurement PM. Thus, a pulse amplitude measurement PM representing a pulse amplitude greater than that of the pulse shape parameter P _PS received at the first instant _t1 results in a pulse amplitude measurement PM > 1, whereas conversely, a pulse amplitude measurement PM > ₁ representing the pulse shape received at the first instant t1 The smaller pulse amplitude measurement PM of the pulse amplitude of the parameter P _PS results in a pulse amplitude measurement PM<1.

When the pulse amplitude measurement PM has been obtained, the processing unit 128 considers that the above-mentioned criterion will be reached if:

(a) the checked pulse amplitude measurement PM for a given pulse shape parameter is below the threshold T; and

(b) The pulse amplitude measurement PM is below the threshold T for a predetermined amount of pulse shape parameter P _PS received during the test period τ after the pulse shape parameter is given.

According to one embodiment of the invention, the predetermined quantity is a value representing approximately 50% to approximately 100% of the pulse amplitude measurement PM of the pulse shape parameter P _PS received during the test period τ. The predetermined quantity may represent all pulse amplitude measurements PM of the pulse shape parameters P _PS received during the test period τ. However, in order to avoid being interrupted by a single pulse amplitude measurement PM above the threshold T, it may be advantageous to assign the predetermined amount to correspond to less than 100%. Alternatively, the second threshold may be assigned to be slightly above threshold T, and processing unit 128 may employ a hysteresis algorithm such that once the pulse amplitude measurement PM falls below threshold T, if during the test period τ expires at If the pulse amplitude measurement PM does not exceed the second threshold, it is considered that the determination standard is met.

In the example shown in Figure 4b, the pulse amplitude measurement PM falls below the threshold T for the first time around t=128 minutes. Here, we assume that the aforementioned predetermined amount is 100%, and that the test period τ is 5 minutes long. Thus, the test period τ ends around t=133 minutes. However, at this point in time the pulse magnitude measurement PM exceeds the threshold T again. Therefore, the processing unit 128 will not generate an alarm trigger signal. the

At around t=135 minutes, the pulse amplitude measurement PM returns to a level below the threshold T, while the pulse amplitude measurement PM remains below the threshold T for longer than the test period τ (here 5 minutes). Thus, at the end of the test period τ (ie at approximately t=140 minutes), the processing unit generates an alarm trigger signal α. So until t=t _h when hypotension occurs, there are about 5 minutes left. Thus, with the aid of the alarm trigger signal α, appropriate manual and/or automatic hypotension prevention actions can already be carried out within the expected time. It is even more advantageous if the processing unit 128 is adapted to generate an attention signal (eg lighting a yellow light on the unit) any time the pulse amplitude measurement PM falls below the threshold T. Thus, any supervising staff member can obtain the earliest possible indication that acute symptomatic hypotension may be present and thus require additional attention from the subject. If at the end when the pulse amplitude measurement PM rises beyond the threshold T, the judgment criterion has not been reached, then the attention signal is invalid.

Of course, test period τ lengths other than 5 minutes are also conceivable according to the invention. In practice, the test period τ may represent any time interval selected from a range extending from about 3 minutes to about 15 minutes. The length of τ during the test is a design parameter chosen to achieve the desired balance between stability and reliability. Preferably, the selection of the test period T is performed in conjunction with the above-mentioned predefined denominator. That is, for a given balance between early hypotension alerts and false alerts, a relatively large denominator requires a relatively short test period, and vice versa. the

In addition, if, in the example of FIG. 4b, the predetermined amount of pulse amplitude measurement PM below the threshold T required to meet the decision criterion has been selected as a value less than 100%, such as 60%, then the alarm trigger signal α is already at Generated upon expiration of the first test period τ (ie, t = 133 minutes or so). the

Similar to Figures 4a and 4b, Figures 5a and 5b respectively show graphs illustrating changes in blood pressure and corresponding changes in pulse amplitude measurements of a third subject during extracorporeal blood therapy. the

In this example, the subject suffers two acute symptomatic hypotensive episodes at t = t _h1 (around 155 minutes during treatment) and t = t _h2 (around 178 minutes during treatment). In order to facilitate comparison with the above example, we have also chosen here to normalize the initial pulse amplitude measurement PM1 obtained at _t1 (t=0) to 1, choosing a threshold T=0.5 (i.e., a predefined denominator of 2 ), and set the length of the test period τ to 5 minutes. Additionally, if all pulse amplitude measurements PM of the pulse shape parameters P _PS received during the test period τ fall below the threshold T, we consider the criterion to have been met.

As is evident in the graph in Fig. 5b, given these parameter values, the processing unit 128 will be at t = t _α1 (around 145 minutes during treatment) and t = t _α2 (around 171 minutes during treatment) respectively. An alarm trigger signal α is generated at . A prediction of the occurrence of a hypotensive event is thus provided approximately 7 to 10 minutes in advance.

Returning momentarily to Figure 3b, we see that the pulse amplitude measure PM never falls below the threshold T (here 0.5). Therefore, in this case, the processing unit 128 will not generate any alarm trigger signal a. the

Now we return to Figure 1. According to one embodiment of the invention, the device 100 comprises auxiliary recording means 130 adapted to repeatedly register a bioimpedance parameter P _BI representing the degree of capillary constriction of the subject P. In this embodiment, the processing unit 128 is further adapted to receive the bio-impedance parameter P _BI and to investigate whether the parameter P _BI meets the auxiliary alarm criterion. If this criterion is found to be fulfilled, the processing unit 128 is adapted to generate an alarm trigger signal a. Thus, the performance and reliability of the device 100 is improved. In order to further improve the usability of the device 100, it is preferred if the auxiliary recording means 130 are adapted to determine a bioimpedance parameter substantially independent of the subject P's capillary constriction. Thus, the auxiliary recording means 130 may register absolute body temperature, changes in body temperature and/or the amount of sweat on the subject P, while the processing unit is adapted to test the auxiliary alarm criteria against one or more of these parameters.

To summarize, a general method for predicting rapid symptomatic blood pressure reduction in a subject according to the present invention will be described below with reference to the flowchart in FIG. 6 . the

A first step 610 investigates whether pulse shape parameters have been received for peripheral body parts of the subject. If no such parameters have been received, the program loops back and stays at step 610. However, if pulse shape parameters have been received, then step 620 follows, which calculates an initial pulse amplitude measurement based on the pulse shape parameters received at the first time instant. It is assumed here that a pulse shape parameter has been registered by pulse oximetry, wherein the pulse shape parameter is determined based on a change in light absorption in at least one blood vessel of the subject. the

A subsequent step 630 stores the initial pulse amplitude measurement in a memory device. Thereafter, a measurement period follows in which step 640 calculates individual pulse amplitude measurements based on each received pulse shape parameter. Additionally, for each pulse amplitude measurement in the measurement period, step 650 following step 640 investigates whether the pulse amplitude measurement met a decision criterion relative to the initial pulse amplitude measurement. If the decision criterion is found not to have been met, and assuming the measurement period is still valid, the program loops back to step 640 . the

However, if in step 650 the criterion is found to have been met, then step 660 follows which causes an alarm trigger to be generated. Thereafter, the procedure may end, or loop back to step 640 (assuming the measurement period is still active). Preferably, the deactivation during the measurement is in response to manual intervention, such as pressing a reset button. That is, the measurement period is thus directly restarted (or actually maintained) even if the measurement may have been forced to be interrupted, for example because the sensor unit 115 has fallen off the main body P. In this case, the sensor unit 115 can simply be reconnected, after which the measurement continues.

All the processing steps and any subroutines of the steps described above with reference to FIG. 6 can be controlled by a programmed computer device. In addition, although the embodiments of the invention described above with reference to the accompanying drawings include computer equipment and programs executed in computer equipment, the invention therefore also extends to computer programs, especially on or on a carrier suitable for putting the invention into practice. computer program in . The program may be in the form of source code, object code, code intermediate source and object code eg in partially compiled form, or in any other form suitable for implementing a program according to the invention. A carrier may be any entity or device capable of carrying a program. For example, the carrier may comprise a storage medium such as flash memory, ROM (Read Only Memory) such as CD (Compact Disc) or semiconductor ROM, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory) memory), or a magnetic recording medium such as a floppy disk or a hard disk. Additionally, the carrier may be a transmittable carrier, such as an electrical or optical signal that may be transmitted via electrical or optical cable or by radio or by other means. When the program is embedded in a signal that can be directly transmitted through a cable or other device or device, the carrier may be constituted by such a cable or device or device. Alternatively, the carrier may be an integrated circuit in which the program is embedded, and the integrated circuit is suitable for executing the relevant program or used for the execution of the relevant program. the

The term "comprising/comprising" used in this specification is used to describe the stated features, integers, steps or components presented. However, the term does not exclude the presence or addition of one or more other features, integers, steps or components or combinations thereof. the

The invention is not limited to the embodiments presented in the figures but can be varied freely within the scope of the claims.

Claims (12)

1. an alert device (100) is used to predict that the quick symptomatic blood pressure in the main body (P) reduces, and this equipment comprises:

Pulse recording equipment (110; 115), be suitable for registering repeatedly pulse shape parameter (P in the peripheral body part (105) of described main body (P) _PS) and

Control unit (120) is suitable for receiving described pulse shape (P _PS) parameter, investigate described pulse shape parameter (P _PS) whether reach alarm criteria, and if, alarm (A) is started, it is characterized in that, described pulse recording equipment comprises pulse blood oxygen instrument (110), and it is suitable for registering described pulse shape parameter (P based on the light response variations at least one blood vessel of described main body (P) _PS), and described control unit (120) comprises processing unit (128), described processing unit is suitable for: based on the first moment (t ₁) pulse shape parameter (P that receives _PS) calculating initial pulse magnitude measure value (PM1),

Described initial pulse magnitude measure value (PM1) is stored in the storage device (123) relevant with described control unit (120),

At the described first moment (t ₁) during afterwards the measurement, based on a plurality of pulse shape parameter (P that receive _PS) in each calculate each pulse magnitude measures value (PM),

For each the pulse magnitude measures value (PM) in during the described measurement, investigate described each pulse magnitude measures value (PM) and whether reach criterion with respect to described initial pulse magnitude measure value (PM1), and if,

Produce alarm trigger signal (α).

2. equipment according to claim 1 is characterized in that, described processing unit (128) is suitable for described criterion is considered as reaching, if:

The checked pulse magnitude measures value (PM) of given pulse shape parameter is lower than the threshold values (T) that calculates based on described initial pulse magnitude measure value (PM1); And

Described pulse shape parameter (the P of the scheduled volume that after described given pulse shape parameter, in test period (τ), receives _PS) described pulse magnitude measures value (PM) be lower than described threshold values (T).

3. equipment according to claim 2 is characterized in that, described scheduled volume is the described pulse shape parameter (P that receives in the described test period of expression (τ) _PS) whole 50% to 100% value of described pulse magnitude measures value (PM).

4. equipment according to claim 2 is characterized in that, described scheduled volume is represented the described pulse shape parameter (P that receives in the described test period (τ) _PS) whole described pulse magnitude measures value (PM).

5. according to each described equipment in the claim 2 to 4, it is characterized in that described test period (τ) is the interval of selecting from extended to 15 minutes scope in 3 minutes.

6. equipment according to claim 5 is characterized in that, described test period (τ) approximately be 5 minutes long.

7. according to each described equipment in the claim 2 to 4, it is characterized in that described processing unit (128) is suitable for calculating described threshold values (T) by following method:

The described initial pulse magnitude measure value of normalization (PM1) and

Remove described normalized initial pulse magnitude measure value with predefined denominator.

8. equipment according to claim 7 is characterized in that, is the pulse shape parameter (P that receives by removing original amplitude measurements with described initial pulse magnitude measure value (PM1) during described processing unit (128) is suitable for during described measurement _PS) calculating pulse magnitude measures value (PM1).

9. equipment according to claim 7 is characterized in that, described predefined denominator is to extend to the value of selecting 5 the scope from 1.2.

10. according to each described equipment in the claim 2 to 4, it is characterized in that described equipment comprises:

ARU auxiliary recorder unit (130) is suitable for registering repeatedly the bio-impedance parameter (P of the blood capillary shrinkage degree of the described main body of expression (P) _BI) and

Described processing unit (128) is further adapted for and receives described bio-impedance parameter (P _BI), investigate described bio-impedance parameter (P _BI) whether reach the auxiliary alarm standard, and if then produce described alarm trigger signal (α).

11. according to each described equipment in the claim 2 to 4, it is characterized in that, described equipment is suitable for predicting that the quick symptomatic blood pressure in the main body (P) that stands haemodialysis reduces, and described processing unit (128) is suitable for the pulse shape parameter (P that receives in the baseline based on described haemodialysis _PS) calculate described initial pulse magnitude measure value (PM1).

12. a medical system (200) is suitable for main body (P) is carried out haemodialysis, wherein this system comprises:

Dialysis machine (210), be suitable for to described main body (P) carry out extracorporeal blood treatment and

Require the described alert device of each claim (100) in 1 to 11 according to aforesaid right.

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