Abstract: A respiratory therapy apparatus that delivers a predetermined pulsed dose of a therapeutic gas to a patient upon inhalation of the patient. The system has separate conduits for the supply of the therapeutic gas at a high concentration and for the supply of a diluent gas. The therapeutic gas conduit has a control valve that is accurately controlled to open and close so as to deliver a precise dose of the high concentration therapeutic gas. The diluent gas conduit has means to ensure there is sufficient flow of diluent gas to ensure the said high concentration therapy gas is diluted to a safe concentration. A third conduit receives the gases from both the first and second conduits so that the gases are mixed together and administered to the patient. By this system, the therapeutic gas supply can be of a high, otherwise harmful, concentration and the therapeutic gas is diluted prior to introduction to the patient.

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 infant warming apparatus that functions both as an infant incubator as well as an infant warmer. The apparatus has a heater that moves vertically with respect to an infant support during the change in function between an infant incubator and infant warmer. A powered motive system, such as an electric motor, powers the movement of the heater between its upper and its lower positions. The heater also has a door or doors that are open when the heater is in it upper position so that the heater can direct energy toward the infant to warm the infant when acting as an infant warmer. When closed, the doors isolate the heater to prevent the inadvertent touching of the heater by the infant or attending personnel. A safety interlock system is provided that prevents the heater from being activated unless it is in its upper position and the door or doors are fully open.

Abstract: An apparatus and method for identifying one anesthetic agent contained in an anesthetic gas sample as the primary anesthetic agent and for identifying a second anesthetic agent as the secondary anesthetic agent is based on the use of minimum alveolar concentration (MAC). The primary agent is identified as the anesthetic agent which has the highest percent of its MAC at its measured volume concentration. The secondary agent is identified as the anesthetic agent which has the second highest percentage of its MAC at its measured volume concentration. Certain minimum threshold levels must be met before an anesthetic agent is identified either as the primary or secondary agent.

Abstract: A novel respiratory gas analyzer employs optical fibers to facilitate in-stream, multiple component infrared analysis. In one embodiment, the analyzer (10) includes an infrared source (12), entrance optics (14), a sample chamber (20), exit optics (24) and a detector assembly (28). One or both of the entrance optics (14) and exit optics (24) includes infrared optical fibers. In this manner, the source (12) and or detector assembly (28) can be located away from the patient (22) as may be desired. In addition, the fiber optic implementation reduces system complexity and optical alignment concerns.

Abstract: An infant incubator having a heating system that provides a flow of heated air into the infant compartment and which exhausts air from the infant compartment. A temperature sensor is located in the air inlet of the warm air into the infant compartment and another temperature sensor is located in the air outlet of the air from the infant compartment. The system thus monitors the temperature of the air to the infant compartment and the air from the infant compartment. By analyzing the temperatures from the inlet and the outlet the overall incubator heating system can be controlled and yet a further advantage is provided by using the temperature information to recognize a fault or deficiency in the incubator system.

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 photoplethysmographic measurement system is disclosed in which a fast-turn-off photodiode is used in order to minimize the effect of "bleed-through" voltages on the dark time (ambient) light determination. Particularly in photoplethysmographic instruments which utilize switched-gain preamplifiers the "bleed-through" of voltage which should be associated with the excitation of the photodiode by the emitter into the dark time or ambient light calculation will negatively impact the accuracy of blood analyte determination. A hardware method and a software method for determining whether a given photodiode has a sufficient decay time are also disclosed.

Abstract: A two piece probe having a universal probe end and an interconnect cable segment provides for the use of the universal probe end with a variety of different photoplethysmographic devices. The universal probe end includes a detector, a substrate for removably affixing the probe end to a patient, a window or aperture and a connector. The interconnect cable has a connector mated to the connector on the probe end for mechanical and electrical connection of the probe-end to the interconnect cable and the photoplethysmographic monitor. The connector end of the interconnect cable also houses a plurality of emitters which are directed through the window or aperture in the probe end in order to illuminate the patient. The interconnect cable also houses the resistors or other elements which identify the type of probe, monitor manufacturer or actual emitter wavelengths. Alternatively, the emitters may be housed in the main monitor and an optical fiber may be used to direct light to the patient.

Abstract: A novel process is disclosed for continually or periodically correcting gas spectrometer measurements for wavelength calibration drift without interrupting the gas measurement process. The spectrometer employs certain calibration vectors for use in obtaining single component information based on a composite measurement for a multi-component gas sample. A calibration vector can be provided for each component of interest as well as an average spectrum and other spectra as desired. These calibration vectors are used to selectively compensate for spectral interference between the multiple components so as to effectively isolate and measure a selected spectral characteristic for a particular component of interest. Temperature changes and attendant variations in spectrometer dimensions or other temperature related factors can degrade measurement performance.

Abstract: A gas spectrometer is provided having an enhanced capability for maintaining initial calibration conditions therewithin. The gas spectrometer is particularly apt for respiratory gas analysis applications and includes a housing assembly that defines an internal containment area(s), within which a radiation source, optical assembly, sample gas assembly and radiation detection assembly are positioned. A gas removal assembly is provided for removing one or more undesired gas component types from within the internal containment area during field use. The gas removal assembly is selectively retractable from the housing assembly to permit periodic servicing (e.g., replacement of CO.sub.2 absorbent) without requiring disassembly or recalibration of the spectrometer.

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: A gas spectrometer is provided for the monitoring of the maintenance of desired calibration conditions. The inventive method and apparatus is particularly apt for use in respiratory gas spectrometers. Monitoring may be achieved by first establishing calibration condition values obtained by passing radiation beams through a reference gas chamber and purged, sample gas chambers upon initial calibration. Subsequently, e.g. after the spectrometer has been utilized in the field, corresponding test condition values are obtained by passing radiation beams through the same reference gas chamber and purged, sample gas chambers. Comparisons utilizing the calibrated condition values and test condition values can be made to monitor calibration variances (e.g. variances, in optical pathway conditions and depletion of the radiation source(s) utilized in the gas spectrometer).

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: A standoff for mounting two or more printed circuit boards to a chassis in which one keyhole cut printed circuit board may be slidably mounted on the keyhole mount of the standoff and a second printed circuit board may be mounted on the top portion of the standoff spaced away from the first printed circuit board. The second printed circuit board may be affixed to the standoff by either a screw mount, snap lock mount, adhesive, bolt and nut, clamp or other method.

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 radiation source assembly is provided that is particularly apt for use in an anesthetic gas monitoring device (e.g., a gas spectrometer) to enhance maintenance of initial calibration conditions therewithin. In one embodiment a respiratory gas spectrometer includes a containment assembly that defines an internal containment area(s) within which a ceramic radiation source, an optical assembly, a sample gas assembly, and a radiation detection assembly are positioned. The radiation source assembly is provided for positioning and supporting the ceramic radiation source relative to the optical assembly within an internal containment area of the gas monitor. The radiation source assembly provides for enhanced sealing between the ceramic radiation source and adjoining componentry. The radiation source assembly is selectively retractable from the containment assembly to permit periodic servicing (e.g., replacement of the radiation source) without requiring disassembly of the gas spectrometer.

Abstract: The improved pulse oximeter preprocesses the sets of red and infrared signals received from the probe to remove ambient light, to remove noise, and to de-exponeniate the signals. The linearity of the processed red and infrared signals allows the use of statistical techniques such as linear regression and linear correlation to fit a best fit straight line to the set of pairs of processed red and infrared data points and to measure the goodness of the straight line fit to these data points. The result of this analysis is a linear regression slope and a goodness of fit correlation coefficient. The correlation coefficient is a measure of the linearity of the input data points and, if less than a predetermined threshold, it indicates that a distorted signal has been received from the probe. This permits the pulse oximeter to detect probe off conditions and/or motion in the patient.