Abstract: A method and apparatus for reducing the effects of noise on a system for measuring physiological parameters, such as, for example, a pulse oximeter. The method and apparatus of the invention take into account the physical limitations on various physiological parameters being monitored when weighting and averaging a series of measurements. Varying weights are assigned different measurements, measurements are rejected, and the averaging period is adjusted according to the reliability of the measurements. Similarly, calculated values derived from analyzing the measurements are also assigned varying weights and averaged over adjustable periods. More specifically, a general class of filters such as, for example, Kalman filters, is employed in processing the measurements and calculated values. The filters use mathematical models which describe how the physiological parameters change in time, and how these parameters relate to measurement in a noisy environment.

Abstract: A method and apparatus for reducing the effects of noise on a system for measuring physiological parameters, such as, for example, a pulse oximeter. The method and apparatus of the invention take into account the physical limitations on various physiological parameters being monitored when weighting and averaging a series of measurements. Varying weights are assigned different measurements, measurements are rejected, and the averaging period is adjusted according to the reliability of the measurements. Similarly, calculated values derived from analyzing the measurements are also assigned varying weights and averaged over adjustable periods. More specifically, a general class of filters such as, for example, Kalman filters, is employed in processing the measurements and calculated values. The filters use mathematical models which describe how the physiological parameters change in time, and how these parameters relate to measurement in a noisy environment.

Abstract: In a physiological monitor, a method and an apparatus for determining a patient's pulse rate using data corresponding to a plurality of wavelengths of electromagnetic energy transmitted through the tissue of the patient. The method includes tracking the pulse rate in the data using an adaptive comb filter, the data having signal portions corresponding to the pulse rate and signal portions corresponding to noise, periodically calculating a frequency power spectrum of one of the wavelengths, and using the frequency power spectrum in a pulse rate calculator to determine the pulse rate or to verify the pulse rate calculated by the pulse rate calculator.

Abstract: A method and apparatus for reducing the effects of noise on a system for measuring physiological parameters, such as, for example, a pulse oximeter. The method and apparatus of the invention take into account the physical limitations on various physiological parameters being monitored when weighting and averaging a series of measurements. Varying weights are assigned different measurements, measurements are rejected, and the averaging period is adjusted according to the reliability of the measurements. Similarly, calculated values derived from analyzing the measurements are also assigned varying weights and averaged over adjustable periods. More specifically, a general class of filters such as, for example, Kalman filters, is employed in processing the measurements and calculated values. The filters use mathematical models which describe how the physiological parameters change in time, and how these parameters relate to measurement in a noisy environment.

Abstract: A pulse oximeter sensor with a light source optimized for low oxygen saturation ranges and for maximizing the immunity to perturbation induced artifact. Preferably, a red and an infrared light source are used, with the red light source having a mean wavelength between 700-790 nm. The infrared light source can have a mean wavelength as in prior art devices used on patients with high saturation. The sensor of the present invention is further optimized by arranging the spacing between the light emitter and light detectors to minimize the sensitivity to perturbation induced artifact. The present invention optimizes the chosen wavelengths to achieve a closer matching of the absorption and scattering coefficient products for the red and IR light sources. This optimization gives robust readings in the presence of perturbation artifacts including force variations, tissue variations and variations in the oxygen saturation itself.

Abstract: A method and apparatus for reducing the effects of noise on a system for measuring physiological parameters, such as, for example, a pulse oximeter. The method and apparatus of the invention take into account the physical limitations on various physiological parameters being monitored when weighting and averaging a series of measurements. Varying weights are assigned different measurements, measurements are rejected, and the averaging period is adjusted according to the reliability of the measurements. Similarly, calculated values derived from analyzing the measurements are also assigned varying weights and averaged over adjustable periods. More specifically, a general class of filters such as, for example, Kalman filters, is employed in processing the measurements and calculated values. The filters use mathematical models which describe how the physiological parameters change in time, and how these parameters relate to measurement in a noisy environment.

Abstract: A pulse oximeter sensor with a light source optimized for low oxygen saturation ranges and for maximizing the immunity to perturbation induced artifact. Preferably, a red and an infrared light source are used, with the red light source having a mean wavelength between 700-790 nm. The infrared light source can have a mean wavelength as in prior art devices used on patients with high saturation. The sensor of the present invention is further optimized by arranging the spacing between the light emitter and light detectors to minimize the sensitivity to perturbation induced artifact. The present invention optimizes the chosen wavelengths to achieve a closer matching of the absorption and scattering coefficient products for the red and IR light sources. This optimization gives robust readings in the presence of perturbation artifacts including force variations, tissue variations and variations in the oxygen saturation itself.

Abstract: This invention provides apparatus for collecting parameter disturbance information from each connected apparatus which can disturb measuring vital signs, and broadcasting a message regarding the disturbance and a coordinating clock signal to all apparatus. Connected sensors susceptible to parameter disturbances identify them from the message and suppress their audible alarm during an interval given in the message. This eliminates false audible alarms caused by such disturbances. The disturbance interval can be extended for later disturbances unless it is a new source or disturbance type and the alarm is already suppressed. A brickwall timer limits the total maximum suppressed interval to a safe maximum. A recovery timer allows a sensor to recover from a parameter disturbance before responding to a subsequent one.

Abstract: Apparatus and method for the monitoring of physiological parameters of a patient through the use of optical systems which do not require direct physical contact with the patient. The method and apparatus relate primarily to pulse oximetry for monitoring of pulse rate and arterial blood oxygen saturation. However, the apparatus and method of this invention are applicable to any form of optical detection of the physiological parameters in which light of any wavelength, visible or invisible, is directed from a remote instrument into a patient at a first imaging site, and subsequently collected at a second site spaced from the first site.

Abstract: An improved fetal pulse oximeter sensor. The friction provided on the sensor head surface to engage the fetus is higher than the friction on the back side of the sensor head. Thus, any contact with a maternal surface by the back side of the sensor head is less likely to dislodge the sensor, since the maternal tissues will slide over the sensor head. The portion of the sensor surface in contact with the fetus' head will not move because of the increased friction. The increased friction can be achieved by using two different materials with different coefficients of friction, or by using a smooth surface on the back of the sensor head, and a rough surface on the sensor face.

Abstract: An apparatus of and method for measuring arterial blood oxygen saturation at a particular tissue level of interest. Visible and near infrared radiation is emitted into a patient at the measurement site using two different wavelengths. Detection at two different detection sites permits rejection of oxygen saturation at undesired tissue levels.

Abstract: A pulse oximeter which modifies the alarm condition when motion is detected. Basically, if the lack of a pulse is determined to be as a result of motion artifact, the generation of an alarm is postponed. In addition, the display indicates that motion is present and that the last reading is questionable due to the presence of motion. The invention also determines if motion artifact is present from the pulse oximeter detector signal itself. The ratio of the positive and negative peaks of the derivative of the pulse signal are compared to a motion/blood pulse threshold.

Abstract: This invention provides apparatus for collecting parameter disturbance information from each connected apparatus which can disturb measuring vital signs, and broadcasting a message regarding the disturbance and a coordinating clock signal to all apparatus. Connected sensors susceptible to parameter disturbances identify them from the message and suppress their audible alarm during an interval given in the message. This eliminates false audible alarms caused by such disturbances. The disturbance interval can be extended for later disturbances unless it is a new source or disturbance type and the alarm is already suppressed. A brickwall timer limits the total maximum suppressed interval to a safe maximum. A recovery timer allows a sensor to recover from a parameter disturbance before responding to a subsequent one.

Abstract: The present invention provides an encoding mechanism for a medical sensor which uses a modulated signal to provide the coded data to a remote analyzer. The modulated signal could be, for instance, a pulse width modulated signal or a frequency modulated signal. This signal is amplitude independent and thus provides a significant amount of noise immunity.

Abstract: An apparatus and method for sensing respiratory motion to detect sleep apnea and the like. An acoustic pulse stimulator or generator located on one side of a body sends impulses through the body to impinge on one or more sensors on the opposite side of the body. Because time delay between transmitter and receiver is determined by distance, and because distance is directly related to breathing motions of the body, measurement of the time delay will have a direct correspondence to breathing motions.

Abstract: The present invention provides a method and apparatus for adapting to noise sources affecting a pulse oximeter. Various available frequencies are evaluated to determine their respective noise levels and one is selected to act as the operating demultiplexer frequency. During normal operation of the pulse oximeter, the various available demultiplexer frequencies are periodically scanned to determine which has the lowest associated noise. The noise level associated with the operating frequency is used to determine the signal-to-noise ratio of the pulse oximeter signals and thereby qualify certain signals from the pulse oximeter. Those pulses associated with a signal-to-noise ratio below a predetermined threshold are rejected and excluded from use in calculating blood oxygen saturation.

Abstract: An apparatus of and method for measuring arterial blood oxygen saturation at a particular tissue level of interest. Visible and near infrared radiation are emitted into a patient at the measurement site using two different wavelengths. Detection at two different detection sites permits rejection of oxygen saturation at undesired tissue levels.

Abstract: A network or telemetry system which allows virtual services at the application or presentation layer to communicate with other virtual services without regard to the physical interconnections. Each message, called a parcel, includes the information to be transmitted along with a virtual address header. The parcel is provided to a gateway, which inserts the parcel without modification into a packet with address information for the physical through session layers in the packet header. The packet is then transmitted to another network node, which receives and delivers the unmodified parcel to the addressed destination virtual service. A number of parcels from the same or different virtual services can be packed into a single packet for transmission from the gateway in cases where these parcels are all directed to virtual services at the same destination node.

Abstract: A conformable sensor which uses a flexible substrate, preferably a polyester strip is disclosed. The emitter and detector are mounted on one portion of the strip with conductive traces connecting to them. The second portion of the strip is folded over to cover the emitter and detector and traces, with openings for the emitter and detector. A conductive coating is applied to the strip to provide shielding from electromagnetic interference. Preferably, a second portion of the strip, which folds over the first portion, also has a Faraday shield covering the opening over the detector. The detector and emitter semiconductor chip die (rather than use encapsulated chips) may be mounted directly on the polyester strip so that it is in contact with one of the conductive traces.

Abstract: A method and apparatus for improving the calculation of oxygen saturation and other blood constituents by non-invasive pulse oximeters. The method and apparatus permit more accurate determination of blood flow by collecting time-measures of the absorption signal at two or more wavelengths and processing the collected time-measure to obtain composite pulsatile flow data from which artifacts have been filtered. The processing may occur in the time domain or in the frequency domain. In the preferred time domain embodiment, successive portions of periodic information are weighted and added together in synchrony to obtain the composite pulse information. In the preferred frequency domain embodiment, the time-measure is Fourier transformed into its spectral components to form the composite information.