Abstract: Apparatus and methods for non-invasively determining the cardiac output or pulmonary capillary blood flow of a patient using partial re-breathing techniques. The apparatus includes a substantially instantaneously adjustable deadspace volume for accommodating differences in sizes or breathing capacities of various patients. The apparatus may be constructed of inexpensive elements, including one or more two-way valves, which render the apparatus very simple to use and inexpensive so that the unit may be employed as a disposable product. The method of the invention includes estimating the cardiac output or pulmonary capillary blood flow of a patient based on partial pressure of alveolar CO2 rather than on the partial pressure of end tidal CO2, as previously practiced. A computer program for calculating the cardiac output or pulmonary capillary blood flow of a patient is also disclosed.

Abstract: A method of continuously, non-invasively determining the cardiac output of a patient. The method includes intermittently measuring the cardiac output, the volume of carbon dioxide exhaled by the patient per breath, and determining the arterial-venous gradient of the patient or a similar substantially constant value by dividing the volume of carbon dioxide exhaled by the measured cardiac output. The arterial-venous gradient or similar substantially constant value may then be employed to determine the cardiac output of the patient on a breath-by-breath basis. The carbon dioxide elimination, which is non-invasively measured as the volume of carbon dioxide exhaled by the patient per breath, is divided by the arterial-venous gradient or the substantially constant value to determine the cardiac output.

Abstract: A re-breathing method for determining pulmonary capillary blood flow that accounts for changes in the cardiac output or in the carbon dioxide content of the venous blood of a patient. The carbon dioxide elimination and partial pressure of end tidal carbon dioxide of the patient are non-invasively measured prior to re-breathing, during re-breathing, and after re-breathing. The carbon dioxide elimination and the carbon dioxide content of the alveolar blood of the patient at each of the before, during, and after re-breathing phases are then used to calculate the pulmonary capillary blood flow of the patient. A rate of change of carbon dioxide content of the venous blood of the patient may also be calculated and employed in calculating the pulmonary capillary blood flow of the patient.

Abstract: A re-breathing method for determining pulmonary capillary blood flow that accounts for changes in the carbon dioxide content of a patient. The carbon dioxide elimination and partial pressure of end tidal carbon dioxide of the patient are measured prior to re-breathing, during re-breathing, and after re-breathing. A rate of change of carbon dioxide content of the venous blood of the patient is then calculated. The rate of change is then employed in calculating the pulmonary capillary blood flow of the patient.

Abstract: A method of sampling one or more respiratory profile characteristics and monitoring a variety of respiratory profile parameters. The sampled respiratory characteristics include respiratory flow rate, respiratory pressure, and partial pressure of at least one constituent of a patient's respiration. The method detects patient breaths, determines whether each breath, is a spontaneous breath or a ventilator-induced breath, and calculates various respiratory profile parameters based on the sampled measurements. The method displays the respiratory profile parameters in graphic and numeric forms. Preferably, the method allows a user to select the displayed respiratory profile parameters.

Abstract: An oximetry sensor comprising a foam wrap member including a fastener, back film mounting member, LED assembly and photodiode connected to a cable, support rings for the LED assembly and photodiode, window film for the LED assembly and photodiode, and a top liner.

Abstract: An airway valve, method of operation and ventilator circuit including the valve. The airway valve includes an outer housing defining a primary passage including first and second coaxial primary passage portions mutually directly communicating within the housing, and first and second diversion passages extending transversely to the primary passage, each diversion passage being integral with the housing and opening onto a primary passage portion. The airway valve controls diversion of air flow between the first primary passage portion and the second primary passage portion into and through an enlarged volume defined by a re-breathing loop external to the housing via the first and second diversion passages. To selectively effect such diversion, an elliptical valve element is oriented within the housing at a 45.degree. angle to both the first primary passage portion and the first diversion passage and disposed on the end of an actuation shaft aligned with the first diversion passage.

Abstract: A method of sampling one or more respiratory profile characteristics and monitoring a variety of respiratory profile parameters. The sampled respiratory characteristics include respiratory flow rate, respiratory pressure, and partial pressure of at least one constituent of a patient's respiration. The method detects patient breaths, determines whether each breath is a spontaneous breath or a ventilator-induced breath, and calculates various respiratory profile parameters based on the sampled measurements. The method displays the respiratory profile parameters in graphic and numeric forms. Preferably, the method allows a user to select the displayed respiratory profile parameters.

Abstract: An airway valve for re-breathing, a ventilator circuit including same and a method of operating the airway valve. The airway valve includes a housing having first and second primary passages extending through the wall thereof and mutually directly communicating within the housing through a spring-biased valve assembly in the form of first and second diaphragms respectively and simultaneously movable in tandem within the housing into and out of contact with first and second valve seats on a valve body with which the first primary passage communicates. The valve assembly also controls diversion of air flow between the first primary passage and the second primary passage into and through an enlarged volume defined by a re-breathing loop external to the housing via first and second diversion passages, which also extend through the wall of the housing.

Abstract: An oximetry sensor comprising a foam wrap member including a fastener, back film mounting member, LED assembly and photodiode connected to a cable, support rings for the LED assembly and photodiode, window film for the LED assembly and photodiode, and a top liner.

Abstract: A method of calculating the carbon dioxide elimination of a patient that includes counteracting any inaccuracy or inconsistency in respiratory flow measurements that may be caused by "noise", such as is attributable to respiratory circuit leaks, signal drift, a non-unity respiratory quotient, or another respiratory flow error-inducing factor. The method includes monitoring the respiratory flow and carbon dioxide of the patient during at least a portion of both inspiration and expiration; calculating an inspiratory tidal volume, an inspiratory volume averaged carbon dioxide fraction, an expiratory tidal volume, and an expiratory volume averaged carbon dioxide fraction; and selecting a tidal volume to replace at least one of the inspiratory tidal volume and the expiratory tidal volume. The carbon dioxide elimination of the patient is then calculated with the select tidal volume, the inspiratory volume averaged carbon dioxide fraction, and the expiratory volume averaged carbon dioxide fraction.

Abstract: A method of non-invasively estimating the intrapulmonary shunt in a patient. The method includes non-invasively measuring respiratory flow, respiratory carbon dioxide content, and arterial blood oxygen content. A re-breathing process is employed to facilitate an estimate of the patient's pulmonary capillary blood flow. Any inaccuracies of the arterial blood oxygen content are corrected to provide a substantially accurate arterial blood oxygen content measurement. The respiratory flow and carbon dioxide content and arterial blood oxygen content measurements, and the pulmonary capillary blood flow estimate are employed to estimate an intrapulmonary shunt of the patient. The invention also includes a method of determining the total cardiac output of the patient which considers the estimated intrapulmonary shunt.

Abstract: An oximetry sensor comprising a wrap member including a fastener and adhesive member and an LED assembly and photodiode connected to a cable.

Abstract: An oximetry sensor comprising a foam wrap member including a fastener, back film mounting member, LED assembly and photodiode connected to a cable, support rings for the LED assembly and photodiode, window film for the LED assembly and photodiode, and a top liner.

Abstract: A non-invasive system and procedure for deriving the blood gas content for a patient. The system measures the carbon dioxide concentration of the expiratory breath relative to volume. This data is then processed to derive arterial blood gas levels of carbon dioxide. If data sampling is in the time domain, the processing shifts the data from the time domain to the volume domain. The processing also iteratively assesses the significance of numerous variables. The resulting relationship provides a fast and accurate measure of blood gas content for both healthy and diseased lung patients.

Abstract: A transducer for nondispersive infrared radiation (NDIR) gas analysis and a passive device for verifying the calibration of the transducer. The calibration verification device can be mounted on a cable by which the transducer is attached to an associated signal processing-control-display unit (SPCDU) or monitor. Calibration parameters for the transducer are stored in a plug at the monitor end of the cable. The transducer includes an integrated subassembly of an infrared radiation source unit, an infrared radiation detector unit, and a flex connector and may be employed with an airway adapter preferably maintained by a thick film heating element at an above-dewpoint temperature to ascertain the concentration of a specie potentially present in gases flowing through the adapter. The transducer may also be employed for other purposes.

Abstract: Gas analyzer systems which include: (1) a transducer for outputting a signal indicative of the concentration of a specified gas in a sample which may contain that gas, and (2) an airway adapter or cuvette with a flow passage for confining the sample to a particular path traversing the transducer. The cuvettes feature radiant energy transmitting windows which are flush mounted in apertures on opposite sides of the cuvette flow passage and are fabricated from a polymer such as biaxially oriented polypropylene which is malleable, yet resistant to wrinkling, warping, and other forms of distortion. Retainer rings keep the windows flat and distortion free with an accurately reproducible spacing between the windows.

Abstract: Infrared radiation emitter units for gas analyzers and other applications. The emitter has a substrate with a film of electrically resistive, emissive material on one of its surfaces. The emitter is so mounted on an emitter unit base that it can freely expand as the emitter heats up. A lead frame commutator, employed to electrically connect the emitter to an external power source, also facilitates the assembly of the unit. A component with a plated, parabolic surface collimates and focuses into an appropriate beam the energy generated by the emitter.

Abstract: Power supplies for generating a stream of electrical pulses in which successive pulses have opposite polarities. The pulses are formed and outputted from pulse generating circuitry which has two complementary pairs of MOSFETs arranged in an H-bridge configuration. Other major components of the power supply are voltage regulators for supplying positive and negative operating pulses with selected, precisely controlled voltages to the driver and watchdog circuits for disenabling the pulse outputting circuitry if: the frequency of the operating pulses deviate from a selected range, the widths of the operating pulses exceed a selected maximum, extraneous pulses are present, or the voltage of the operating pulses falls below or exceeds selected maximums. In one important application, the power supply is employed to drive the emitter of an infrared radiation source.