Abstract: A signal processor which acquires a first signal, including a first desired signal portion and a first undesired signal portion, and a second signal, including a second desired signal portion and a second undesired signal portion, wherein the first and second desired signal portions are correlated. The signals may be acquired by propagating energy through a medium and measuring an attenuated signal after transmission or reflection. Alternatively, the signals may be acquired by measuring energy generated by the medium. A processor of the present invention generates a noise reference signal that is a combination of the undesired signal portions and is correlated to both the first and second undesired signal portions. The noise reference signal is then used to remove the undesired portion of each of the first and second measured signals.

Abstract: A method and device for measurement of a level of at least one blood constituent. The device includes a light source and a light detector proximate the surface of an organ. The device also includes a pair of adjustable gain amplifiers and a processor/controller connected within a processing unit. The processing unit operates to separate an AC signal component from a DC signal component. The light source includes at least one light emitting unit. Preferably, the light source alternatingly emits light at two different wavelength ranges and normalizes the AC and DC output signals corresponding with the intensity of the light reflected from the organ and calculates a ratio of the normalized signals for each wavelength range. The device may determine the level of the blood constituent and may also use this level for monitoring and/or to activate an alarm when the level falls outside a predetermined range.

Abstract: A signal processor which acquires a first signal, including a first desired signal portion and a first undesired signal portion, and a second signal, including a second desired signal portion and a second undesired signal portion, wherein the first and second desired signal portions are correlated. The signals may be acquired by propagating energy through a medium and measuring an attenuated signal after transmission or reflection. Alternatively, the signals may be acquired by measuring energy generated by the medium. A processor of the present invention generates a noise reference signal which is a combination of only the undesired signal portions and is correlated to both the first and second undesired signal portions. The noise reference signal is then used to remove the undesired portion of each of the first and second measured signals via an adaptive noise canceler, preferably of the joint process estimator type.

Abstract: An intelligent, rule-based processor provides recognition of individual pulses in a pulse oximeter-derived photo-plethysmograph waveform. Pulse recognition occurs in two stages. The first stage identifies candidate pulses in the plethysmograph waveform. The candidate pulse stage identifies points in the waveform representing peaks and valleys corresponding to an idealized triangular wave model of the waveform pulses. At this stage, waveform features that do not correspond to this model are removed, including the characteristic dicrotic notch. The second stage applies a plethysmograph model to the candidate pulses and decides which pulses satisfies this model. This is done by first calculating certain pulse features and then applying different checks to identify physiologically acceptable features.

Abstract: A red light and an infrared light which are emitted from a light emitting portion 2 are transmitted through a fingertip 4 of a subject and are converted into electric signals by a light receiving portion 3. The respective signals are separated and amplified and are then sent to a CPU 8. In the CPU 8, the input signals are divided into D.C. components DC1 and DC2 and A.C. components AC1 and AC2, changes &Dgr;A1=(AC/DC) 1 and &Dgr;A2=(AC/DC)2 in an absorbance are calculated, high frequency components thereof are extracted, a mutual ratio &PSgr; is calculated, and a noise removing waveform is calculated based thereon. Based on the noise removing waveform, a pulse wave is detected, a pulse rate is calculated, a display wave form is calculated and an oxygen saturation is calculated. These are displayed through a display unit 11.

Abstract: An improved pulse oximeter is disclosed. The pulse oximeter includes audio signal generation means, controlled by algorithms in a processing element which continuously transform the signals from the sensor into signal quality information. This information is converted into an audio signal and annunciated for the operator's use in guiding sensor placement. This signal quality information is available even in the absence of successful computation of pulse rate and/or oxygen saturation level. It furthermore can reflect signal quality changes that may be too subtle to be reflected in the typical numerical representation of pulse rate and oxygen saturation trend. The audio representation of the signal quality can further be modulated to convey other system and/or physiological status and alerts.

Abstract: A method for determining an arterial blood oxygen saturation level according to this invention includes measuring the light transmittance through tissue of light of a first wavelength and a second wavelength. A steady-state component of the measured light transmission is used to select an appropriate calibration curve. A pulsatile component of the measured light transmission is used to determine the arterial blood oxygen saturation level using the selected calibration curve. An oximetry system is also provided.

Abstract: An apparatus and method is disclosed which allows the non-invasive monitoring of a subject's carboxyhemoglobin level, thereby allowing the detection of possible carbon monoxide poisoning. The subject breathes oxygen to saturate his blood hemoglobin and eliminate reduced hemoglobin, thus allowing the detection and differentiation between oxy- and carboxyhemoglobin by modification of a conventional pulse oximeter. Preferably the device works in two modes. The first mode is a conventional pulse oximeter capable of determining the level of oxy-hemoglobin in the subject's arterial blood. Upon the achievement of certain criteria the preferred embodiment of the inventive device would switch to a second mode, in which mode the device would be capable of determining carboxyhemoglobin levels. Alternatively, carboxyhemoglobin can be measured using two devices and two different pairs of wavelengths transilluminating two different body parts.

Abstract: In a method for operating a magnetic resonance tomography system having a shim coil arrangement and a gradient coil arrangement, in which, in order to generate an image dataset of a region of an examination subject to be imaged, at least the region that is to be imaged is borne in an imaging volume of the system, an initial shim adjustment procedure is carried out, a change (if it occurs) in the position of the imaged region in relation to the imaging volume is detected, and a current in the shim coil arrangement is modified dependent on the detected position change.

Abstract: A signal processor which acquires a first signal, including a first desired signal portion and a first undesired signal portion, and a second signal, including a second desired signal portion and a second undesired signal portion, wherein the first and second desired signal portions are correlated. The signals may be acquired by propagating energy through a medium and measuring an attenuated signal after transmission or reflection. Alternatively, the signals may be acquired by measuring energy generated by the medium. A processor of the present invention generates a noise reference signal which is a combination of only the undesired signal portions and is correlated to both the first and second undesired signal portions. The noise reference signal is then used to remove the undesired portion of each of the first and second measured signals via an adaptive noise canceler, preferably of the joint process estimator type.

Abstract: In a method for the non-invasive determination of the oxygen saturation in tissue supplied with blood, the tissue is irradiated with red and infrared light and the DC and AC components of the emerging light are measured. During a first time interval, a calibration factor k is determined from the DC and AC components of the emerging light. During a second time interval, the oxygen saturation in the tissue is computed progressively from the DC components of the emerging light and the determined calibration factor k.

Abstract: A blood-constituent concentration measuring instrument capable of accurately measuring concentrations of the constituent parts of blood without invading tissue. Light source means (1) emits measuring light (S) to a living organism (2). The measuring light (S) consists of a plurality of wavelength components different from one another. Straight-advance light discrimination means (3) extracts a straight-advance light component or a scattered light component close thereto from light scattered at the living organism (2). Then, extinction-index change detection means (4) detects an extinction index change in straight-advance light component or the scattered light component extracted by the straight-advance light discrimination means (4). Calculation means (5) calculates concentrations of the constituent parts of the blood, based on the extinction index change for each wavelength component of the measuring light.

Abstract: A clamping device for use in a surgical retractor support includes a first clamp member for clamping a first retractor support. The first clamp member has a first opening that is disposed along a longitudinal axis of the first retractor support for receiving the first retractor support. A pin disposed within the clamp member has a cam surface for acting on the first retractor support member. A handle operable with the pin for moving the cam surface between a first nonlocking position and a second locking position for locking the first retractor support member from movement. Preferably a wedge section is positioned between the cam surface and the first retractor support such that the wedge section frictionally engages the first retractor support when the cam surface is in the second locking position. The clamping device also has a second clamp member for clamping a second retractor support.

Abstract: A pulse oximeter has several processing channels for measurement signals which are measured during the switched-on phase of transmission diodes and which are used to determine the oxygen saturation (SpO.sub.2) of a patient. An additional measurement channel processes an ambient light signal which was measured while the transmission diodes were switched off or their intensity modified, in the same way and thus provides a measure of the spectral composition of the ambient light interference. A useful-to-noise-signal ratio (NSV) is derived from the ambient light signal and a measurement signal, which represents a measure of the signal quality and which can be compared with threshold values (G), where an alarm is triggered if the value falls below the threshold values.

Abstract: A compact pulse oximetry system and method which separates the combined signal into its respective AC and DC components. By separating the signal into AC and DC components, a smaller order bit A/D converter may be used while still maintaining signal accuracy. Instead of using the combined signal to calculate the oxygen saturation content, the system microprocessor computes the Ratio of Ratios using the derivative of the separated AC component of the diffused signal to calculate the oxygen saturation of the measured fluid. To calculate the Ratio of Ratios, a ratio of the derivative value of the separated AC component is used. Instead of taking a single sample between the peak and valley of the signal, the oximeter system samples each value. To decrease the effect of system noise, a linear regression is performed over each sample.

Abstract: The invention relates to apparatus for testing a pulsed light oximeter, such as a non-invasive oximeter which emits pulses of red and infrared light. A light sensor produces an electrical pulse signal representative of light flashes emitted by the oximeter, and a signal generator produces a plurality of absorbance signals representative of the optical absorbance of an anatomical part at the wavelength of each light flash. A signal selector responds to time interval, duration and amplitude features of the electrical pulse signal, or to electrical signals produced by the oximeter itself, and thereby selects one of the plurality of absorbance signals to produce a selected absorbance signal. The selected absorbance signal is converted to light and conveyed to the oximeter to simulate the effect of the anatomical part on the light flashes emitted by the oximeter.

Abstract: The quantitative determination of various materials in highly scattering media such as living tissue may be determined in an external, photometric manner by the use of a plurality of light sources positioned at differing distances from a sensor. The light from said sources is amplitude modulated, and, in accordance with conventional frequency domain fluorometry or phosphorimetry techniques, the gain of the sensor is modulated at a frequency different from the frequency of the light modulation. Data may be acquired from each of the light sources at differing distances at a frequency which is the difference between the two frequencies described above. From these sets of data from each individual light source, curves may be constructed, and the slopes used to quantitatively determine the amount of certain materials present, for example glucose, oxyhemoglobin and deoxyhemoglobin in living tissue.