| Apparatus and method for determining a physiological condition -> Monitor Keywords |
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Apparatus and method for determining a physiological conditionRelated Patent Categories: Surgery, Diagnostic Testing, Via Monitoring A Plurality Of Physiological Data, E.g., Pulse And Blood PressureApparatus and method for determining a physiological condition description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060281980, Apparatus and method for determining a physiological condition. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] This invention relates to the detection of a physiological condition, such as hypoglycaemia, in a patient. More particularly, the invention relates to an apparatus for detecting a physiological condition in a person, and to a method of alerting a patient to the risk of the presence of a physiological condition. BACKGROUND OF THE INVENTION [0002] One of the most frequent complications experienced by patients suffering from insulin dependant diabetes mellitus is the phenomenon of hypoglycaemia. [0003] Hypoglycaemia is a physiological condition where the blood glucose level of the patient decreases below a certain value. Blood glucose levels below approx. 2.5 mmol/L may give rise to serious symptoms and may potentially even become dangerous for a diabetic patient, in particular, if the patient does not become aware of the condition, e.g. because the patient is sleeping or preoccupied with another activity, e.g. driving a car. [0004] Already during the onset of hypoglycaemia more moderate drops of the blood glucose level, e.g. below approximately 3.8 mmol/L glucagon, cause epinephrine, growth hormone, and cortisol to be released, resulting in symptoms such as rise in pulse, lowering of the variability of the heart rate and increased perspiration. [0005] Hence, there is a strong desire to allow for a monitoring of a patient to avoid an undetected occurrence of hypoglycaemia. Even though glucose meters which only require small blood samples exist, frequent measurements of the glucose level in blood samples taken from the patient are painful and not suited for a continuous monitoring. [0006] U.S. Pat. No. 4,509,531 discloses a non-invasive watch-like monitoring device that measures body temperature and skin resistance. In the event of either a predetermined change in galvanic skin resistance or a predetermined change in peripheral skin temperature an alarm is generated which can waken a sleeper wearing the monitoring device. [0007] Another watch-like device that uses perspiration and a drop in skin temperature to detect hypoglycaemia is the Sleep Sentry by Diabetes Sentry Products Inc. Studies for this device have shown that, when hypoglycaemia was confirmed to be present, the alarm was generated about 90% of the time, thereby leaving about 10% of the occurrences undetected. Furthermore, it is not uncommon for patients to experience a false alarm. [0008] Hence, in the light of the above prior art devices it is desirable to increase the reliability of the hypoglycaemia detection. [0009] International patent application WO 02/069798 discloses a method of determining the presence of a physiological condition in a person where the person's skin impedance, heart rate, QT interval and mean or peak frequency of the .alpha. wave are measured. The measured input data are fed into a multilayer feedforward neural network which is trained to calculate the patient's blood glucose status. The neural network is trained using the back-propagation algorithm in which synaptic strengths are systematically modified so that the response of the network approximates the blood glucose status of the patient with increasing accuracy. [0010] It is a problem of the above prior art system that the actual performance of the neural network can only be assessed based on statistical methods. Hence, an explicit validation of the output for all possible sets of input data is unfeasible. However, since such a system is used in a medical context, it is desirable to provide a system with a reliability which may be systematically validated over the entire range of measured sensor values. [0011] It is a further problem of the above prior art method that the back-propagation algorithm is time-consuming. SUMMARY OF THE INVENTION [0012] It is an object of the present invention to provide an apparatus for detecting a physiological condition in a person with a high reliability and a performance that can systematically be validated. [0013] The above and other objects are achieved by an apparatus for detecting a physiological condition in a person, the apparatus comprising [0014] processing means adapted to receive at least two physiological parameters, and to determine, from the received physiological parameters, a result signal indicative of the presence or onset of said physiological condition; and [0015] output means for generating an output indicative of the result signal; [0016] wherein the apparatus comprises storage means for storing a look-up table comprising a plurality of entries, each entry corresponding to a pre-calculated probability of the presence or onset of said physiological condition, the pre-calculated probabilities being determined by means of a mathematical process from previously monitored physiological parameters; and [0017] the processing means is adapted to process the received at least two physiological parameters to identify one of the plurality of entries of the look-up table, and to determine said result signal from the identified entry of the look-up table. [0018] Consequently, by providing a look-up table such that any combination of sellnsor inputs is associated with one entry in the look-up table, and by using a suitable mathematical process such as a reinforcement learning algorithm to update the table values, an improved apparatus for detecting a physiological condition is provided. [0019] In particular, it is an advantage that the entries stored in the look-up table may systematically be validated. Since any combination of inputs is associated with an entry in the look-up table, the output generated by the device for any combination of inputs may easily be validated. Furthermore, as the entries correspond to pre-calculated probabilities of the presence of said physiological condition that are determined by means of a mathematical process from previously monitored physiological parameters, a high reliability of the detection of the physiological condition is achieved. [0020] Furthermore, is an advantage that the look-up table provides a direct indication of the probability of the presence or onset of said physiological condition indexed by the input parameters. Hence, the calculation/evaluation of complex physiological models or predictions of future blood glucose levels during operation is avoided, thereby providing a simple and reliable system. [0021] It has been realised by the inventors that a high degree of reliability may be achieved with look-up tables of moderate sizes, thereby allowing an easy and systematic validation of all entries of the look-up table. For small look-up tables, a validation may even be performed manually. [0022] In particular, it is an advantage that the apparatus automatically detects nightly hypoglycaemia for diabetic patients, sufficiently early for the patient to handle the problem himself/herself. In one embodiment, the physiological parameters are received as corresponding one or more sensor signals. For example, a patient may wear a set of sensors during the night. The sensor signals may be sent to a receiver of a central unit via a wireless connection. This central unit receives the signals, analyses them and sounds an acoustic alarm, if the analysis shows that the patient experiences a hypoglycaemia or is on the way to one. [0023] It is a further advantage that the detection may be based on measurements of several secondary effects rather than a direct measurement of blood glucose. Continue reading about Apparatus and method for determining a physiological condition... Full patent description for Apparatus and method for determining a physiological condition Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Apparatus and method for determining a physiological condition patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. 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