Abstract: The various gases in the blood stream are analyzed by a mass spectrometer coupled to the catheter having on its distal end a membrane that passes the gases but not the blood. A "carrier" gas, such as helium, introduced under a small pressure through a small tube within the catheter lumen and into the area behind the membrane will produce a viscous flow that greatly speeds the gases to the mass spectrometer. The carrier gas is extracted prior to its arrival at the mass spectrometer.

Abstract: Respiratory gas flow data is synchronously provided along with continuous samples of the gases for analysis by a medical mass spectrometer. The gas flow data is determined by use of the differential pressure across a resistive core in a sampling flowmeter and the flow value at any instant is registered by proportionately admitting a non-toxic gas that is foreign to the normal respiratory gases into the sampling inlet in a quantity controlled by the differential pressure. The quantity of foreign gas therefore represents flow and is drawn through the inlet tube in exact synchronism with its corresponding respiratory gas sample for analysis by the spectrometer. The generated signal representing the amount of foreign gas, hence the flow, may then be used with the signals representing concentration of the various gases in the corresponding respiratory gas sample to calculate various medical parameters, such as oxygen uptake, where the exact synchronism of these signals is important.

Abstract: Wet or saturated respiratory gas samples being monitored from one or more hospital patients are sufficiently dried for analysis by a medical mass spectrometer by a novel momentum separator in which the major part of the wet sample flows directly to an exhaust pump while a small sample for analysis is taken from the reverse angle tee connection in the momentum separator. This small sample containing water vapor, but without the heavier moisture droplets, is then heated to about 100.degree. C. to maintain the water in the vapor state prior to entering the spectrometer inlet leak.

Abstract: A flowmeter for accurately determining the rate of flow of a gas substantially independent of its molecular composition and also for determining a measure of the velocity of sound in that gas. The gas flows through a transducer assembly. Disposed in the transducer are two cylindrical transducers each capable of producing or responding to acoustic compressions in the gas. The transducers are alternately switched between transmitting and receiving with one transducer at a given instant being used to transmit and the other to receive. The phase difference between the transmitted and the received signal for two successive transmit-receive cycles are stored with the difference between two successive stored phase differences indicating the magnitude and the direction of fluid flow and the sum of the stored phase differences providing a measurement of the velocity sound in that gas.