Abstract: A method and apparatus is disclosed for determining airway resistance and lung compliance using an electrical circuit model wherein at least one component parameter is non-linear. The system non-intrusively obtains pressure and flow data signals from a pressure transducer and a laminar flow element without interrupting or interfering with normal breathing and gas supply to a patient. An invariant exponential is determined empirically based on physical characteristics of the airway. The non-linear airway resistance and lung compliance can then be calculated based on the sensed flow rate, gas pressure, a calculated gas volume, and the invariant exponential using linear techniques. The resulting airway resistance can be normalized to a standard reporting flow rate value. The system is particularly useful in anesthesia applications, but is also useful in any breathing system where fresh gas is supplied constantly from a gas source other than a ventilator.

Abstract: An emergency oxygen system that provides a flow of oxygen to the patient undergoing anesthesia in the event of a detected fault in the overall supply and mixing system of the anesthesia system. The normal design of such supply and mixing systems for an anesthesia system provides oxygen and at least one other gas that are mixed together in a desired proportion to be provided to a vaporizer and then to the anesthesia system as fresh gas. In the present system, a processor continuously monitors the output flows from those proportioning mixing valves. When the processor determines that those flows from the proportioning valves are off by a predetermined amount, indicative of a fault in the system, the processor immediately shuts off the supply of any gases other than oxygen and also provides a flow of oxygen to a bypass line that bypasses the oxygen proportioning valve, thus assuring a supply of oxygen to the patient despite the fault.

Abstract: An improved method and apparatus for the photoplethysmographic monitoring of blood analyte parameters, specifically oxyhemoglobin, deoxyhemoglobin (reduced hemoglobin), carboxyhemoglobin and, in addition, in a four emitter apparatus, methemoglobin, uses a plurality of beams of light having different spectral contents to trans-illuminate the tissue of a patient. The apparatus and method require the application of an emitter set comprised of four emitters. The emitters may be LED's or laser diodes. In the three analyte system the center wavelength of the emitters must fall within three specific bands. In the four emitter system (capable of measuring methemoglobin) the center wavelength of the emitters in the emitter set must fall within four predetermined bands and the emitters having the two lowest center wavelengths must be at least 5 nanometers apart.

Abstract: The present invention is directed to an improved CCD utilizing a potential gradient along the lengths of the various channels of the CCD during charge transfer to cause generated electrical charge to migrate along the length of the channel to a summing well. The potential gradient is formed by biasing the opposing ends of the electrodes overlying the lengths of the various channels with different voltages.

Abstract: An anesthesia delivery system having a means of determining the functioning of its gas mixer, vaporizer and analyzers, their accuracies and other characteristics by comparing, at high flow conditions, the input of oxygen concentration and agent concentration set by a clinician and delivered by the system, the input from a feedback respiratory analyzer of the inspired O.sub.2 and agent concentrations and the input of a monitor analyzer that determines the O.sub.2 and agent concentrations in the patient circuit. A CPU compares the three sets of input data to make various determinations since, at high flow conditions, all of the three sets of data should be consistent. Thus the CPU can determine from a comparison, whether one set of data is indicative of a faulty device, can provide a bias adjustment if an analyzer is merely off in its readings or carry out other safety and corrective functions based on comparing the three data inputs.

Abstract: An improved photoplethysmographic measurement system is disclosed in which a portion of a time division multiplexed (TDM) signal represents an ambient light level, and other TDM signal portions represent detected levels of two or more centered wavelengths of transmitted light. The ambient and detected light portions of the signal are simultaneously applied to the inputs of an instrumentation amplifier(s) so as to produce a continuous output voltage that is proportional to a difference in voltage between the ambient and detected light portions of a TDM signal. Such an approach provides for ambient light level subtraction with reduced noise and componentry.

Abstract: An adjustable pressure limiting valve having a non-linear biasing means. The valve has a movable valve member that can be moved to an open position by a predetermined pressure and a closed position on a valve seat. A rotating control knob is rotated by the user to adjust the bias acting against the movable valve member toward the closed position to, in turn, set the pressure at which the valve opens. A rotating cylindrical drum rotates along with the control knob and has a helical groove formed in its exterior and a pair of fixed pins that ride in the helical groove. When the cylindrical drum is rotated, the fixed pins riding in the helical grove cause the cylindrical drum to move along its longitudinal axis to compress or decompress a spring acting against the movable valve member. The pitch of the helical groove is designed so as to create a non-linear relationship between the rotational movement of the control knob and the longitudinal movement of the cylindrical drum.

Abstract: A photodetector is used to monitor contamination of optical elements within an optical system. The photodetector is aligned to detect nonspecular/diffuse reflections attributable to surface irregularities of particulate matter residing on the surfaces of the optical elements within the system. An increase in the intensity of the nonspecular reflections corresponds to increased levels of contamination on the surface of the optical element. An electronic detector circuit performs signal processing on the photodetector output signal and generates an output signal corresponding to the contamination level. In another aspect of the invention, the photodetector circuit is incorporated into a Raman gas analysis system.

Abstract: A patient probe disconnect alarm where the patient probe is provided with a vacuum that is formed in a chamber between the patient probe and the skin of the infant. The level of vacuum is monitored within the chamber and whenever the level of vacuum lessens beyond a predetermined vacuum level, the monitor senses a probe disconnect and provides an alert to the user that there is a loss of integrity in the probe affixation to the infant.

Abstract: The present invention is directed to a pulse oximeter sensor and an attached flexible carrier for measuring the oxygen saturation of a patient's blood. The carrier includes a compressible material, such as foam, for contacting the patient's skin and the sensor that applies a substantially uniform pressure to the skin.

Abstract: A mechanism for aligning the elements of an optical system is disclosed. One aspect of the present invention is an alignment mechanism which includes lead screws placed on opposite corners of the elements to be aligned. The elements are provided with threaded holes of different pitch, and the lead screw is provided with threads of the same unequal pitches as the elements, thereby forming a differential lead screw. The threads include a locking thread which assures a positive lock between the lead screw and the elements to be aligned and eliminates backlash between them. Another aspect of the present invention is an interference fit mechanism which is provided by the employment of a slightly-oversized flexible boss which mates with a cavity. The boss is provided with a thin outer wall capable of flexing when the boss is inserted into the cavity. Yet another aspect of the present invention includes a wobble plate comprising a spherical socket and housing.

Abstract: The device for producing a display from monitored data functions to read, store, encode, and integrate monitored data of at least one data type from at least one monitoring device so that the related or unrelated datum is comprehensible at a glance by a user. Encoding data of a particular data type produces a color indicia and a graphic indicia that are the basic integration components. Integrating indicia of at least one data type produces a single superimposed and/or multidimensional image capable of portraying a present and historical data combination reflecting the monitored data's relative value at some point in time.

Abstract: An ultrasonic transducer is disclosed for emitting an ultrasonic wave radially inward. The transducer is constructed with a strip of piezoelectric material laminated with a pair of electrically conductive metal layers that are conductively isolated from one another. In a preferred embodiment, the strip of piezoelectric material is formed in a cylindrical shape and with continuous sinusoidal ripples along the circumference. The sinusoidal ripples are designed to emit a specific wave length of a desired frequency. The radius of the sinusoidal wave is based on material characteristics and the desired resonance frequency. The invention discloses various methods and apparatus for constructing and maintaining the transducer sinusoidal shape. One method includes attachment of a pair of rigid end caps on the laminated piezoelectric material, and another discloses weaving the laminated piezoelectric material through a nonconductive mesh cage, and yet another includes adhesively attaching the transducer to a housing.

Abstract: A photoplethysmographic measurement device that utilizes wavelength division multiplexing is provided. Signals from multiple light emitters are combined into a single multiplexed light signal in a test unit before being delivered to a physically separated probe head attached to a test subject. The probe then causes the single multiplexed signal to be transmitted through a tissue under test on the test subject, after which it is processed to determine a blood analyte level of the test subject. By combining the light signals into a single multiplexed signal before delivering the signals to the probe, a single light guide, such as a single optical fiber, can be used to deliver the signals to the probe, thereby reducing system implementation cost and increasing the flexibility of the probe cable. In addition, the invention allows the signals from the light emitters to be directed into the test subject from a single point source, which can significantly increase measurement accuracy.

Abstract: A two-stage statistical calibration and measurement method and system is disclosed for performing photoplethysmographic measurement of blood analyte concentrations. Concentrations in a tissue sample of MetHb, O.sub.2 Hb, RHb and COHb are estimated by first estimating a concentration of MetHb (in a first stage) and subsequently, if the concentration of MetHb is within a predetermined range, then the estimated concentration of MetHb is assumed to be accurate and this estimated concentration of MetHb is utilized as a "known value" in determining the concentrations of the remaining analytes O.sub.2 Hb, RHb and COHb (in a second stage). That is, by eliminating one "unknown" from the system of equations, these remaining analytes can be calculated with increased accuracy. Each stage is performed using data obtained by transmitting light through the tissue sample (typically a finger or earlobe). The transmitted light is generated by four discrete light emitters, each emitter having a distinct spectral content.

Abstract: A heated humidifier for an infant incubator wherein the water in the water reservoir is heated by an active heater located above the surface of the water and a heat exchanger that transfers heat from the active heater and which extends downwardly to a point beneath the water surface to heat the water. In the preferred embodiment, the heat exchanger is an extruded member in the shape of an I-beam to transfer the heat from an electric heater above the surface of the water to heat the volume of water in the reservoir to create water vapor.

Abstract: A system for automatically refilling the patient breathing circuit of an anesthesia system wherein the system detects the existence of a large leak in the patient breathing system and reduces the flow of the fresh gas to the patient circuit to minimize the amount of gas that is vented to the atmosphere. As the leak is corrected, the system automatically detects that the leak has been alleviated and increases the fresh gas flow to a high flow to refill the patient breathing circuit in a rapid time. Upon refill, the system detects that the circuit and the system has been refilled and automatically reduces the fresh gas flow back to a lower level desired by the clinician to maintain the anesthesia. The fresh gas flow used to refill the patient circuit is the same composition of gases and anesthetic agent as initially set by the clinician.

Abstract: This apparatus places the laser diode light source in the connector affixed to the distal end of the cable, proximate to the patient. The disposable portion of the probe simply consists of the apparatus required to affix the probe to the patient's appendage and the mating portion of the connector that interconnects with the cable. The disposable portion of the probe can be a minimalistic design since all the expensive elements are located in the medical monitoring instrument or the cable connector.

Abstract: An improved method and apparatus for the photoplethysmographic monitoring of blood analyte parameters, specifically oxyhemoglobin, deoxyhemoglobin (reduced hemoglobin), carboxyhemoglobin and methemoglobin, uses a plurality of beams of light having different spectral contents to trans-illuminate the tissue of a patient. Received light is measured and the normalized differential absorption is used in a forward calibration equation to generate estimated relative blood analyte concentration values. Error in the blood analyte concentration values is minimized by applying constraints to the estimated analytes. Specifically, the constraints require that all relative analyte concentration values are greater than or equal to zero and sum to one hundred percent.

Abstract: The present invention is directed to a charge coupled device in which, during the shifting interval, the charge storage pixels are biased with an electrical potential greater than the absolute value of the CCD inversion potential and, during the charge integration interval, the charge storage pixels are biased with an electrical potential that is less than the CCD inversion potential. In this manner, the present invention substantially reduces error attributable to impact ionization or dark current.