Abstract: A compact and wearable metabolic analyzer transducer comprising a housing containing a plurality of analog sensors, an A/D converter, a microcontroller, and a power source operatively coupled thereto where the microcontroller is programmed to compute minute ventilation, O2 uptake, and CO2 production of a subject. The transducer and its contents are of a size and weight that can either be easily supported from a facemask worn by a subject or incorporated in a respiratory circuit. The measured values can be wirelessly transmitted or transmitted, via a cable, to a remote personal computer, a personal digital assistant (PDA), or other display devices such as digital watches or image projectors.

Abstract: A method for improving the performance of a galvanic fuel cell type oxygen sensor comprises providing a pressure equalization port leading to the interior of an inner core housing that contains the membrane, the electrolyte and the anode and cathode electrodes and hermetically sealing the sensor housing except for its sample inlet port and its sample outlet port. By connecting the same vacuum source to both the pressure equalization port and the sample outlet port, the device's membrane is less subject to movement or rupture as gas samples are drawn in via the sample inlet port. A technique for ensuring a hermetic seal is also described.

Abstract: A method for improving the performance of a galvanic fuel cell type oxygen sensor comprises providing a pressure equalization port leading to the interior of an inner core housing that contains the membrane, the electrolyte and the anode and cathode electrodes and hermetically sealing the sensor housing except for its sample inlet port and its sample outlet port. By connecting the same vacuum source to both the pressure equalization port and the sample outlet port, the device's membrane is less subject to movement or rupture as gas samples are drawn in via the sample inlet port. A technique for ensuring a hermetic seal is also described.

Abstract: A method of calibrating a metabolic analyzer incorporating an oxygen analyzer and a NDIR carbon dioxide analyzer in the field that does not require the use of gas cylinders containing gases of known concentration is described. In calibrating the CO2 detector, at the time of factory setup, the detector output for a gas of a known concentration is measured and stored in the memory of the metabolic analyzer's microprocessor, as is the detector output voltage when the IR source is dimmed by a known percentage. Subsequently, in the field, CO2 levels in ambient air and cell pressure are measured at two different flow rates through the sample chamber and the IR source is again dimmed by the same percentage as had been used at the time of factory setup. Based upon the resulting readings, both the zeroing and span adjustment factors can be computed.

Abstract: A method of calibrating a metabolic analyzer incorporating an oxygen analyzer and a NDIR carbon dioxide analyzer in the field that does not require the use of gas cylinders containing gases of known concentration is described. In calibrating the CO2 detector, at the time of factory setup, the detector output for a gas of a known concentration is measured and stored in the memory of the metabolic analyzer's microprocessor, as is the detector output voltage when the IR source is dimmed by a known percentage. Subsequently, in the field, CO2 levels in ambient air and cell pressure are measured at two different flow rates through the sample chamber and the IR source is again dimmed by the same percentage as had been used at the time of factory setup. Based upon the resulting readings, both the zeroing and span adjustment factors can be computed.

Abstract: A device for directly measuring a person's respiratory exchange ratio (RER) utilizes a Zn-air battery cell and a constant current load circuit as an O2 pump capable of drawing oxygen from expired air. A thermistor located in the flow path forms a leg of a bridge circuit whose output is proportional to oxygen concentration in the expired air and, therefore, to oxygen uptake. The thermistor flowmeter circuit utilizes the thermal conductivity differences between O2 and CO2 to provide a measure at the relative ratio of the two gases present.

Abstract: A device for directly measuring a person's respiratory exchange ratio (RER) utilizes a Zn-air battery cell and a constant current load circuit as an O2 pump capable of drawing oxygen from expired air. A thermistor located in the flow path forms a leg of a bridge circuit whose output is proportional to oxygen concentration in the expired air and, therefore, to oxygen uptake. The thermistor flowmeter circuit utilizes the thermal conductivity differences between O2 and CO2 to provide a measure at the relative ratio of the two gases present.

Abstract: A method for prescribing an exercise regimen for a particular subject to either maximize cardiovascular performance or to lose weight involves the use of a microprocessor-based cardiopulmonary exercise system to measure oxygen uptake and carbon dioxide production on a breath-by-breath basis. These measured quantities are used to calculate energy expenditure and a subject's respiratory exchange ratio from which a fat metabolization curve can be plotted. By examining the length of a plateau in the curve where the fat substrate utilization is maximized, and noting the average heart rate in this zone, a target heart rate for optimal weight loss is arrived at. If the goal of the exercise is cardiovascular improvement, the anaerobic threshold can readily be determined as the midpoint between maximal fat utilization and the maximum acceleration towards the point where the respiratory exchange ratio becomes equal to 1 or the fat metabolism goes to 0.

Abstract: A respiratory monitor apparatus comprises, in combination, a flexible mask fabricated from a stretchable fabric, such as spandex, that is designed to support a pneumotach flow measuring instrument in a way that does not require the instrument to be placed in the wearer's mouth, yet still remaining in fluid communication with the wearer's mouth and with little or no dead-space or leakage between the mask member and the wearer's face.

Abstract: A portable apparatus for measuring the thoracic lung volume of a patient without enclosing the patient in a sealed chamber, comprising first and second impedance belts, a flow meter, shutter and a microprocessor-based controller. The flow meter includes pressure transducers for measuring the change in volume and pressure as the patient respires therethrough. The change in thoracic cage volume of the patient's lungs is directly correlated with the change of impedance in the belts. The thoracic lung volume is then determined from a measured barometric pressure, the measured change in pressure and the measured volume change in the thoracic cage volume utilizing a correction factor to determine the thoracic cage volume.

Abstract: A system for real time, breath by breath sampling of a patient receiving up to 100 percent oxygen to determine nutritional requirements of the patient through indirect calorimetry includes a pneumotach member for measuring the volume rate of flow of inspired and expired gas flow at the patient/endotracheal tube/ventilator connection. A sample line extends from the pneumotach to a gas analyzer which measures the percent concentration of constituent respiratory gases in the expired gas flow. A flowmeter is coupled to the gas analyzer for determining the volume flow rate of the expiratory gas flow through the sample line. A microprocessor control samples the analog electrical signals from the gas analyzer, the flow meter and the pneumotach in a predetermined sequence, dynamically compensating for variations in gas flow rate.

Abstract: A method and apparatus is described for preventing contamination of a gas analyzer of respiratory gas exchange analyzing equipment due to a patient's saliva. The method involves determining a resistance value of the inspired respiratory gas flow in a sample line leading to the gas analyzer. This is determined by calculating the absolute pressure in the line at the gas analyzer. The pressure difference from atmospheric pressure is then divided by the sample flow rate to obtain a resistance value. A microprocessor in the equipment compares the calculated resistance of the flow with a previously stored reference threshold resistance. If the calculated resistance exceeds the predetermined threshold, the microprocessor sends a signal to a vacuum pump used to draw the respiratory gases through the gas analyzer. The vacuum pump is immediately shut down when the calculated resistance exceeds the predetermined resistance threshold and, hence, any saliva in the sample line is not drawn into the gas analyzer.

Abstract: A method is described for dynamically calibrating a flowmeter used in cardiopulmonary performance analyzing equipment which takes into account the ambient conditions at the test site in terms of relative humidity, barometric pressure and temperature. At the time of factory calibration, a density factor is computed and stored in a nonvolatile memory along with a calibration factor obtained by passing a known volume of gas at a known relative humidity, temperature and pressure through a pneumotach mouthpiece in a predetermined time span. When the system is being used in the field to evaluate a patient, a new density factor is computed that takes into account the relative humidity, barometric pressure and temperature at the test site and this new density factor along with the density factor previously computed and stored at factory calibration are used to compute a new flow calibration factor for use in obtaining an accurate flow parameter from the system flowmeter.

Abstract: The gas sample line in a cardlopulmonary performance analyzing system is designed to include a flow sensor for measuring the rate of flow of the gas sample being drawn and is used to adjust the initial transit time value measured at the time of system calibration for a known value of flow in arriving at a new or current transit time value at the time that a test is actually being performed on a patient. This dynamically compensates the transit time for variations in the sample flow rate, thus providing a system with accuracy that is not dependent upon maintaining constant sample flow rates.

Abstract: A disposable pneumotachograph flowmeter comprises first and second tubular mouthpiece members which, when juxtaposed relative to one another, sandwich a fabric screen made from a hydrophobic material therebetween. The screen may comprise a woven fabric formed from expanded PTFE fibers or, alternatively, may be a non-woven mat of polyester fibers. Because of the properties of the screen material, it does not become clogged and occluded with moisture particles during use.

Abstract: A single-use, disposable, elastomeric patient valve has a pair of one-way check valves disposed in the cross-piece portion thereof to create a barrier against patient infection. The check valves prevent contamination by a first patient of the reusable demand valve portion as he or she exhales into the patient valve and prevents the inhalation of possibly infected materials into the lungs, via the sampling chamber and associated tubing coupling same to the patient valve.

Abstract: A method for testing/calibrating a system for performing single-breath carbon monoxide lung diffusing capacity measurements. By simulating a patient's lungs using a precision syringe for drawing a preanalysis gas mixture through the equipment (inspiration) and a modified scuba regulator valve or a solenoid valve with a purge button to simulate the expiration of a postanalysis gas through the system into a sampling chamber, the DL.sub.co measuring system performance can be assessed as a whole rather than as a collection of individual components.

Abstract: A method for optimizing either fat utilization or cardiovascular performance during an exercise regimen includes the steps of using a cardiovascular exercise system to measure a subject's respiratory exchange ratio on a breath-by-breath basis and also locating the subject's anaerobic threshold. By locating a fat burning point as the point where the RER is a minimum less than 0.90 at a time when oxygen uptake is less than 55 percent of the peak oxygen uptake and then correlating that fat burning point with the existing heart rate, a fat burning zone can be established by taking that heart rate and adding and subtracting 10 percent from it. The work rate at the target heart rate can also be used to determine the zone. For enhanced cardiovascular performance training, the heart rate existing at the subject's anaerobic threshold is determined and it is set as the lower boundary for a zone whose upper boundary is that value plus 20 percent.