Abstract: A method for detection of interference in impedance based monitoring of a subject by using a monitor is disclosed. The method comprising, connecting the subject to the monitor using one or more leads; and before current is applied to the subject, measuring voltage on the subject via at least one of the one or more leads and if any voltage is detected then the monitor indicates a warning. An impedance based monitor is disclosed, the monitor being connectable to a subject. The monitor is configured to measure voltage on the subject, before any current is applied to the subject, and if any voltage is detected then the monitor is configured to indicate a warning.

Abstract: A reflective SpO2 measurement system includes a light source that emits light of at least a first and second wavelengths, and one or more detection devices forming a close detector positioned at a first distance from the light source and a far detector positioned at a second distance from the light source, wherein the second distance is greater than the first. The SpO2 measurement system is configured to operate in a high power mode to determine a calibration factor based on the comparison of light reflections detected by the close detector and the far detector. The system is further configured to operate in a low power mode to generate a low intensity light pulse, and detect a close reflection of the low intensity light pulse with the close detector. An SpO2 is then determined based on the close reflection of the low intensity light pulse and the calibration factor.

Abstract: A reflective SpO2 measurement system includes a light source that emits light of at least a first and second wavelengths, and one or more detection devices forming a close detector positioned at a first distance from the light source and a far detector positioned at a second distance from the light source, wherein the second distance is greater than the first. The SpO2 measurement system is configured to operate in a high power mode to determine a calibration factor based on the comparison of light reflections detected by the close detector and the far detector. The system is further configured to operate in a low power mode to generate a low intensity light pulse, and detect a close reflection of the low intensity light pulse with the close detector. An SpO2 is then determined based on the close reflection of the low intensity light pulse and the calibration factor.

Abstract: A method for detection of interference in impedance based monitoring of a subject by using a monitor is disclosed. The method comprising, connecting the subject to the monitor using one or more leads; and before current is applied to the subject, measuring voltage on the subject via at least one of the one or more leads and if any voltage is detected then the monitor indicates a warning. An impedance based monitor is disclosed, the monitor being connectable to a subject. The monitor is configured to measure voltage on the subject, before any current is applied to the subject, and if any voltage is detected then the monitor is configured to indicate a warning.

Abstract: A mechanism for non-invasively monitoring blood characteristics of a subject is disclosed. To enable measurement of hemoglobin concentrations in a cost-effective way, a computational model is established that represents a relationship between a first variable indicative of total hemoglobin concentration and a set of variables that includes second variables indicative of light transmission through tissue and third variables indicative of concentration percentages of different hemoglobin species. In-vivo measurement signals are acquired from a subject and in-vivo values are determined for the second and third variables based on the in-vivo measurement signals. The first variable is then solved based on the in-vivo values of the second and third variables and the computational model.

Abstract: A method for monitoring degradation a physiological sensor connected to a patient monitor is disclosed. A patient monitor, a patient monitor system, a physiological sensor, and a computer program product are also disclosed. In order to get an early warning of an imminent breakage or wear out of a physiological sensor and to increase the life time of the sensor without compromising patient safety, history data is collected for at least one sensor feature parameter into a predetermined memory location, wherein the collected history data is indicative of past characteristics of the sensor. The history data is retrieved from the predetermined memory location when the physiological sensor is connected to a patient monitor and a degradation measure indicative of the degree of degradation of the physiological sensor is determined for the physiological sensor based on the history data.

Abstract: The invention relates to the determination of the clinical state of a subject. In order to bring about an uncomplicated method for monitoring the clinical state of a subject and for accomplishing a diagnostic scale, such as a nociception scale, on which a certain reading corresponds to the same level for all patients, a normalization transform is applied to a measurement signal containing physiological data obtained from a patient, whereby a normalized measurement signal having a predetermined value range is obtained. The normalization transform is dependent on predetermined history data, such as previous signal data of said measurement signal. A diagnostic index dependent on the normalized measurement signal is then formed, the diagnostic index serving as a measure of the clinical state of the patient. The diagnostic index may be formed based on one or more normalized measurement signals.

Abstract: A sensor, apparatus and method for non-invasively monitoring blood characteristics of a subject are disclosed. The sensor comprises an emitter unit configured to emit radiation through the tissue of the subject at a plurality of measurement wavelengths and a detector unit that comprises photo detectors. To achieve a simple sensor assembly, the photo detectors are together adapted to receive the radiation at the plurality of wavelengths and to produce in-vivo measurement signals corresponding to the plurality of measurement wavelengths, the in-vivo measurement signals being indicative of absorption caused by blood of the subject. Furthermore, the photo detectors are mounted so that optical paths from the emitter unit to the photo detectors are different, and the plurality of wavelengths are divided between the photo detectors so that two spectrally adjacent photo detectors have at least one common wavelength.

Abstract: A method for monitoring degradation a physiological sensor connected to a patient monitor is disclosed. A patient monitor, a patient monitor system, a physiological sensor, and a computer program product are also disclosed. In order to get an early warning of an imminent breakage or wear out of a physiological sensor and to increase the life time of the sensor without compromising patient safety, history data is collected for at least one sensor feature parameter into a predetermined memory location, wherein the collected history data is indicative of past characteristics of the sensor. The history data is retrieved from the predetermined memory location when the physiological sensor is connected to a patient monitor and a degradation measure indicative of the degree of degradation of the physiological sensor is determined for the physiological sensor based on the history data.

Abstract: The invention relates to the determination of the clinical state of a subject. A respective adaptive transform is applied to at least one measurement signal acquired from the subject, each adaptive transform being dependent on previously acquired history data, and a diagnostic index is formed, which is dependent on the transformed measurement signal(s) and serves as a measure of the clinical state of the subject. In order to reliably evaluate the clinical state of a subject on a fixed diagnostic scale during changes in the state of the subject, some or all of the previously acquired history data on which an adaptive transform is currently dependent is replaced with other previously acquired history data when a predetermined event is detected. The predetermined event is indicative of a change in the respective measurement signal, and the introduction of the said other previously acquired history data sets the transform ready for the change.

Abstract: Method and pulse oximeter system for determining blood characteristics of a subject are disclosed. A pulse oximeter sensor for collecting plethysmographic data is also disclosed. In order to reduce the power consumption, time instants of systolic rises are estimated in at least one plethysmographic waveform of a subject and light emitting elements of a sensor are controlled according to the estimated time instants, thereby to collect signal samples from a plurality of plethysmographic waveforms of the subject during the systolic rises. A desired blood parameter, typically oxygen saturation, is then defined based on the signal samples collected during the systolic rises.

Abstract: Provided is a method of calibrating a pulse oximeter, in which the effects caused by tissue of a subject can be taken into account. A detector output signal is measured when living tissue of the subject is present between emitters and the detector in a sensor. Nominal calibration and nominal calibration characteristics are read from a memory, whereupon values for the same nominal characteristics for the sensor on living tissue of the subject are established using the detector output signal. Then, changes in the nominal calibration characteristics induced by the living tissue are calculated and a subject-specific calibration is formed by correcting the nominal calibration with the changes. Finally, the hemoglobin fractions are solved using the corrected nominal calibration.

Abstract: A mechanism for non-invasively monitoring blood characteristics of a subject is disclosed. To enable measurement of hemoglobin concentrations in a cost-effective way, a computational model is established that represents a relationship between a first variable indicative of total hemoglobin concentration and a set of variables that includes second variables indicative of light transmission through tissue and third variables indicative of concentration percentages of different hemoglobin species. In-vivo measurement signals are acquired from a subject and in-vivo values are determined for the second and third variables based on the in-vivo measurement signals. The first variable is then solved based on the in-vivo values of the second and third variables and the computational model.

Abstract: In order to provide a non-invasive and continuous concentration measurement with the technology of standard pulse oximeters, an a priori relationship is created, through an in-vivo tissue model including a nominal estimate of a tissue parameter indicative of the concentration of a blood substance. The a priori relationship is indicative of the effect of tissue on in-vivo measurement signals at a plurality of wavelengths, the in-vivo measurement signals being indicative of absorption caused by pulsed arterial blood. In-vivo measurement signals are acquired from in-vivo tissue at the plurality of wavelengths and a specific value of the tissue parameter is determined based on the a priori relationship, the specific value being such that it yields the effect of the in-vivo tissue on the in-vivo measurement signals consistent for the plurality of wavelengths. The specific value then represents the concentration of the substance in the blood.

Abstract: A measuring apparatus, a physiological sensor, and an interface unit for determining blood parameters of a subject are disclosed. The sensor comprises an emitter unit comprising a first plurality of emitter elements configured to emit radiation at a second plurality of wavelengths and a detector unit configured to receive radiation generated by the emitter elements and transmitted through the tissue of the subject, wherein the detector unit is further configured to produce electric measurement signals indicative of absorption caused by the blood of the subject. The sensor or the interface unit is provided with a memory that stores emitter activation information for at least a third plurality of wavelengths, thereby to enable a monitoring unit operably connectable to the physiological sensor to employ a combination of wavelengths selected from the third plurality of wavelengths, wherein the third plurality is equal to or smaller than the second plurality.

Abstract: A calibration method for an apparatus for non-invasively monitoring blood characteristics of a subject is disclosed. The apparatus is provided with a computational model representing a relationship between in-vivo measurement signals obtained from the subject and the blood characteristics. The providing includes employing at least one tissue property variable in the computational model, in which the at least one tissue property variable is indicative of absorption and scattering characteristics of the subject's tissue. An arrangement for determining blood characteristics of a subject and a sensor for the arrangement are also disclosed.

Abstract: A method and apparatus for monitoring fluid balance status of a subject are disclosed. A hemoglobin measure indicative of hemoglobin concentration in the blood of a subject and at least one physiological parameter responsive to blood volume changes in the subject are determined and concurrent behavior of the hemoglobin measure and the at least one physiological parameter is indicated to a user, thereby to give an indication of fluid balance status of the subject. The cause and/or reliability of the fluid balance status may also be indicated.

Abstract: A sensor, apparatus and method for non-invasively monitoring blood characteristics of a subject are disclosed. The sensor comprises an emitter unit configured to emit radiation through the tissue of the subject at a plurality of measurement wavelengths and a detector unit that comprises photo detectors. To achieve a simple sensor assembly, the photo detectors are together adapted to receive the radiation at the plurality of wavelengths and to produce in-vivo measurement signals corresponding to the plurality of measurement wavelengths, the in-vivo measurement signals being indicative of absorption caused by blood of the subject. Furthermore, the photo detectors are mounted so that optical paths from the emitter unit to the photo detectors are different, and the plurality of wavelengths are divided between the photo detectors so that two spectrally adjacent photo detectors have at least one common wavelength.

Abstract: Method and pulse oximeter system for determining blood characteristics of a subject are disclosed. A pulse oximeter sensor for collecting plethysmographic data is also disclosed. In order to reduce the power consumption, time instants of systolic rises are estimated in at least one plethysmographic waveform of a subject and light emitting elements of a sensor are controlled according to the estimated time instants, thereby to collect signal samples from a plurality of plethysmographic waveforms of the subject during the systolic rises. A desired blood parameter, typically oxygen saturation, is then defined based on the signal samples collected during the systolic rises.

Abstract: The invention relates to the determination of the anesthetic state of a patient. In order to achieve a mechanism that enables establishment and maintenance of balanced anesthesia, values are established for a set of diagnostic indices. The set includes at least two diagnostic indices of which a first diagnostic index is indicative of the level of hypnosis and a second diagnostic index of the level of nociception in the patient. The combination of the at least two index values obtained is employed for indicating the anesthetic state of the patient. The combination of the at least two index values may further be employed to control the administration of drugs to the patient.