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 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: 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: 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: 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.

Abstract: The respiratory gas analyzer (10), in one embodiment, is used for in-stream analysis of a patient breathing circuit (12). The analyzer includes a source (12) of infrared illumination, a modulator (28) for modulating the infrared illumination on a wavelength dependent basis to yield a modulated signal, a transmitter/detector unit (32) for transmitting the modulated signal through the breathing circuit (12) and detecting the transmitted signal, and a processing unit (34) for determining composition information regarding a sample under analysis based on the detected, modulated signal. The modulator (28) may include, for example, a Michelson interferometer for transforming the illumination into a frequency domain signal. The modulated signal allows for use of a compact detector system at the respiratory circuit interface. In addition, infrared fiber optics can be utilized to minimize instrumentation/optics at the interface.

Abstract: The gas sample identification apparatus transmits at least one beam of light of predefined frequency band through a gas sample present in a gas sampling chamber. The presence and concentration of various agents in the gas sample are determined by a linear variable filter that selectively passes the light beam transmitted through the gas sample chamber to an array of detectors. The detectors are positioned to receive only a narrow passband component of the light beam. The output signals from the array of detectors is processed by a multivariate statistical processor to accurately identify both the presence and concentration of one or more agents contained in the gas sample.

Abstract: The present invention is directed to an oximeter sensor to measure the oxygen content of a patient's blood. The sensor can include a lead frame having different thicknesses, a sensor housing being molded from a common thermoplastic resin, and rib members in the housing for inhibiting shorting between adjacent traces of the lead frame. The present invention further includes a process for forming the sensor.