Abstract: A gas analyzer is provided which is particularly suited for making transcutaneous measurement of the CO.sub.2 concentration in the blood.In accordance with one embodiment of the invention, sample gases from the body are circulated in a cavity of the device. A rotating wheel in the cavity includes two reference cells and a sample cell which are sequentially rotated into the optical path between a source and a detector. Three signals are thereby provided which may be combined to give an output indication of the CO.sub.2 concentration in the body fluids. In a preferred embodiment, the sample cell is an "inverted cell" being in open communication with the sample gas circulating in the device so that the gas in the sample cell is a portion of the circulating gas which also surrounds the two reference cells. An output indication is thereby obtained which is insensitive to contaminants in the sample.

Abstract: The concentration (and thus the partial pressure) of certain gases, such as carbon dioxide and oxygen and the pH (hydrogen ion concentration) in arterial blood are determined without the need for contacting the blood by first stripping off the top dry skin layer forming a "window" of small size. A small chamber is sealed to the skin around the window and the absorption in the chamber of electro-magnetic radiation of particular wavelengths resulting from the constituent of interest is noted as a measurement from which the concentration of that constituent in arterial blood is calculated. Specific embodiments of such electro-optical measuring chambers are described for measuring concentration of various specific constituents in arterial blood.

Abstract: A gas analyzer is provided which is particularly suited for making transcutaneous measurement of the CO.sub.2 concentration in the blood.In accordance with one embodiment of the invention, sample gases from the body are circulated in a cavity of the device. A rotating wheel in the cavity includes two reference cells and a sample cell which are sequentially rotated into the optical path between a source and a detector. Three signals are thereby provided which may be combined to give an output indication of the CO.sub.2 concentration in the body fluids. In a preferred embodiment, the sample cell is an "inverted cell" being in open communication with the sample gas circulating in the device so that the gas in the sample cell is a portion of the circulating gas which also surrounds the two reference cells. An output indication is thereby obtained which is insensitive to contaminants in the sample.