Device for the analysis of an anesthesia ventilation gas as well as anesthesia ventilator

Abstract

A device analyzes an anesthesia ventilation gas with an infrared radiation source and includes a gas cuvette, a Fabry-Perot interferometer with a band pass filter function, adjustable with respect to a central transmission wavelength as a function of a control signal, a detector providing a measured signal and a computing and control unit providing the control signal and detecting the measured signal. The computing and control unit is configured to actuate the Fabry-Perot interferometer in a first operating mode by the control signal such that the central transmission wavelength scans a predefined wavelength range, to detect a presence in the ventilation gas sample potential types of anesthetic gases based on the measured signal. In a second operating mode, the control unit controls the central transmission wavelength within a subrange of the predefined wavelength range and determines a plurality of concentration values at consecutive times for detected types of anesthetic gases.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of priority under 35 U.S.C. §119 of German Application 10 2016 009 366.8 filed Aug. 3, 2016, the entire contents of which are incorporated herein by reference.FIELD OF THE INVENTION[0002]The invention relates to a device that analyzes an anesthesia ventilation gas with an infrared radiation source and includes a gas cuvette arranged in a measuring path for receiving a ventilation gas sample of the anesthesia ventilation gas and further relates to an anesthesia ventilator (also known as an anesthesia respirator) with such as device.BACKGROUND OF THE INVENTION[0003]The anesthetic gas components and the types of anesthetic gas that are contained in an anesthesia ventilation gas and the respective percentages at which these are contained in the anesthesia ventilation gas fed to the patient and in the gas exhaled by the patient represent essential information for an anesthesiologist in the course of the anes...

AI Technical Summary

Benefits of technology

[0035]The device is preferably configured such that the device further has a data interface, wherein the computing and control unit is configured to provide the concentration values at the data interface. This configuration is advantageous, because it makes it possible to provide the concentration values in the form of a data signal for additional devices.

[0037]The device is preferably configured such that the gas port is configured for connection to a Y-piece of a ventilation tube. This configuration is advantageous, because a measurement is now possible in the vicinity of the Y-piece, so that the measuring accuracy relative to an exhaled gas of a patient is increased.

[0039]The device is preferably configured such that the computing and control unit is configured to receive input data of an input unit and further to select the maximum duration of the second operating mode as a function of the input data. This embodiment is advantageous, because an anesthesiologist can determine himself, by presetting the input data, how often a testing of the composition of the anesthesia ventilation gas consisting of different types of anesthetic gases is performed by the device in the first operating mode. The patient is possibly in an anesthesia phase of the anesthesia ventilation, during which the anesthesiologist does not expect any change or any essential change in the composition of the anesthesia ventilation gas. By making corresponding inputs, he can then increase the duration of the second operating mode, in which the temporal resolution of the concentration value determination is lower than in the second operating mode.

[0040]The device is preferably configured such that the computing and control unit is configured to modulate the amplitude of the infrared radiation source according to a modulation frequency in the second operating mode by means of an additional control signal, wherein the computing and control unit selects the modulation frequency as a function of the types of anesthetic gas detected as being present from the first operating mode. This configuration is advantageous, because interference effects due to equisignal components can be reduced by means of an amplitude modulation of the infrared radiation source and a lock-in analysis of the measured signal by means of a lock-in amplifier on the detector side. If an amplitude modulation of the infrared radiation source is carried out with a certain modulation frequency, this modulation frequency must be selected to be high enough for a minimum number of signal periods to reach the detector at a certain measuring wavelength or central wavelength of the band pass filter function; if the central transmission wavelength is changed over time, as it happens in the first operating mode due to the scan over the predefined wavelength range, this corresponds to a frequency change or frequency modulation of the central wavelength. The greater the change over time in the central wavelength, the greater is the corresponding frequency modulation and the higher must be the frequency of the amplitude modulation of the infrared radiation source. For example, a measurement may only be necessary at a single wavelength in the case in which only a single type of anesthetic gas was detected in the first operating mode, and the modulation frequency can then be selected at a lower value at this measuring wavelength than when then central transmission wavelength is changed greatly over time for scanning three wavelengths, which would require a higher modulation frequency for the amplitude modulation of the radiation source. The lower the modulation frequency for the amplitude modulation, the greater will be the signal-to-noise ratio of the detected or received signal at the detector. Consequently, if only one measuring wavelength or only one central transmission wavelength is necessary for only one detected type of anesthetic gas, the modulation frequency for the amplitude modulation can then be selected to be lower than when a change is necessary over time in the central transmission wavelength for the measurement at different measuring wavelengths for a plurality of types of anesthetic gases.

Problems solved by technology

Therefore, the anesthetic gas-measuring device does not necessarily know what kinds of types of anesthetic gas are present in the anesthesia ventilation gas, because this depends on the selection made by the anesthesiologist or it depends on the phase of the anesthesia ventilation.

Consequently, if an anesthetic gas-measuring device shall be able to perform a concentration measurement for different combinations of the five types of anesthetic gas shown in FIGS. 1 and 2, it is sometimes insufficient to have the measuring wavelengths λ1, λ2, λ3 from FIG. 1 as fixed wavelengths in respect to the two types of anesthetic gas shown there for the absorbance measurement, because these measuring wavelengths could be unsuitable, for example, for a measurement of one or more types of anesthetic gas from FIG. 2.

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