Abstract: A method of increasing the shelf life of a reversible calorimetric device for indicating carbon dioxide is disclosed, which method comprises placing said device together with at least one non-toxic pH-lowering gas in a gas-tight wrapping or casing. A package is also disclosed which is prepared by means of said method. The invention also relates to the use of a non-toxic pH-lowering gas for increasing the shelf life of a device of the above mentioned type.

Abstract: A device for determining the depth of anaesthesia of a patient, the device including an optical measuring means (1) for measuring on a part (2) of the patient an optical parameter such as transmission or reflection, which is influenced by the circulation of the blood through this part of the patient's body, and to produce an electric signal which varies in accord with this parameter. This signal is related to the periodic variations in the blood-pressure of the patient and thus has a frequency which coincides with the heart frequency of the patient and a maximum amplitude and a minimum amplitude which are related respectively to the systolic and diastolic blood-pressure of the patient. The signal is applied to signal processing circuits (3) which determine the variation in the period of the signal (.DELTA.(R-R)) and the variation in its maximum amplitude (.DELTA.P.sub.max) or minimum amplitude (.DELTA.P.sub.min) or in the difference between its maximum and minimum amplitudes (.DELTA.(P.sub.max -P.sub.

Abstract: Apparatus for measuring the oxygen uptake of a person connected to a respirator (23) includes a closed container (1) of variable volume. The container (1) can be connected to the respiratory passages of the person, via an inspiration line (2) and an expiration line (3), so that the person can inspire from and expire to the container (1). One of the lines incorporates a carbon dioxide absorber (19) for removing carbon dioxide from the respiratory gas. Means (17,18) are provided for monitoring the volume of the container (1), and controllable means (8,9,10) are found for supplying pure oxygen gas to the container (1). The oxygen-gas supply means (8,9,10) are so controlled by the means (17,18) monitoring the volume of the bellows (1) that the volume of the bellows at a given predetermined point in the breathing cycle of the person connected to the apparatus is held substantially unchanged. Means are also provided for determining the amount of oxygen gas supplied to the container (1) herewith.

Abstract: Apparatus for determining the proportion of a given gas component in a gas mixture, comprising a piezoelectric crystal provided with a surface layer containing a substance capable of selectively and reversibly adsorbing said gas component, and being so arranged that the gas mixture can be brought into contact with said surface layer. The crystal is incorporated in an oscillator circuit which produces an output signal representing the oscillating frequency of the crystal, and therewith the proportion of the given gas component in the gas mixture. For compensating the temperature dependency of the surface-layer adsorption of the relevant gas component, a thermistor (R.sub.T) is arranged to be influenced by the same temperature variations as the piezoelectric crystal. Further, the output signal (S) of the oscillator circuit is connected to the input of an amplifying circuit, which incorporates the thermistor (R.sub.