SYSTEM COMPRISING A CLOSED-CIRCUIT RESPIRATOR AND A MONITORING DEVICE THEREFOR

Abstract

A system includes a closed-circuit respirator (1) with a breathing mask (2), a closed breathing circuit, which leads from the breathing mask via an exhalation tube (3), a lime cartridge (4) for binding CO.sub.2, a spring-loaded breathing bag (5) and an inhalation tube (7) to the breathing mask. A pressurized oxygen tank (11) is connected to the circuit via a constant dispensing unit (8) and to the breathing bag via a minimum flow control valve (9), which opens upon a collapse of the breathing bag (lack of breathing gas in the circuit) and fills the breathing bag from the oxygen tank. A pressure sensor (12) detects the pressure in the oxygen tank. A constant dispensing unit introduces oxygen with a volume lower than a mean oxygen volume demand. A monitoring device (13-15) calculates a quantity of oxygen consumed and still remaining from the detected pressure and an initial pressure value.

Claims

1. A system comprising: a closed-circuit respirator and a monitoring device therefor, the closed-circuit respirator comprising: a breathing mask; an exhalation tube; an inhalation tube; a closed breathing circuit connected to the breathing mask via the exhalation tube and the inhalation tube, the breathing circuit having a breathing lime cartridge for binding CO.sub.2, a spring-loaded breathing bag; an oxygen tank containing pressurized oxygen; a constant dispensing unit, the oxygen tank being connected to the closed breathing circuit via the constant dispensing unit; a minimum flow control valve, the oxygen tank being connected to the breathing bag via a minimum flow control valve, wherein the minimum flow control valve is configured to open in response to a collapse of the breathing bag because of lack of breathing gas in the closed breathing circuit and to fill the breathing bag with oxygen from the oxygen tank until the breathing bag is filled; and a pressure sensor for detecting the pressure in the oxygen tank, wherein the constant dispensing unit is configured to introduce oxygen into the closed breathing circuit with a low basic volume flow, which is lower than a mean oxygen volume demand of an unstressed person, and the monitoring device is configured to calculate a quantity of oxygen consumed by breathing by the user of the device and a quantity of oxygen still remaining in the oxygen tank from a current pressure value delivered by the pressure sensor and an initial pressure value of the pressurized oxygen in the oxygen tank at a beginning of use.

2. A system in accordance with claim 1, wherein the monitoring device is configured to calculate a current oxygen consumption per unit of time from the volume curve of the oxygen consumedVO.sub.2(t)the change in oxygen volume as a function of time, from the slope of said curve.

3. A system in accordance with claim 2, wherein the monitoring device is configured to calculate a predicted remaining service life from the current oxygen consumption and the quantity of oxygen still remaining in the oxygen tank.

4. A system in accordance with claim 2, wherein the monitoring device is configured to compare the basic volume flow with the current oxygen consumption and to reduce the basic volume flow by acting on the constant dispensing unit when the basic volume flow is not lower than the current oxygen consumption by a preset threshold criterion.

5. A system in accordance with claim 1, wherein the monitoring device is configured to calculate the work performed by the user of the device, Q(t)=Q.sub.0.Math.VO.sub.2(t) (wherein Q.sub.0 is a physiological parameter, determined in advance, of an energy equivalent with a value of about 20.2 kJ/L(O.sub.2)) or the metabolic output performed from the volume of the oxygen consumed by the respirator user during the mission, VO.sub.2(t) up to a time t.

6. A system in accordance with claim 5, wherein the monitoring device is configured to calculate the mechanical output performed by the respirator user from the metabolic output performed up to a point in time.

7. A system in accordance with claim 1, wherein the monitoring device is configured to calculate from the volume of the oxygen consumed by the respirator user during the mission up to a time t the volume of CO.sub.2 produced by the respirator user up to that time, VCO.sub.2(t)=RQ.Math.VO2(t), wherein RQ, as a respiratory equivalent, is a factor determined empirically in advance.

8. A system in accordance with claim 7, wherein the monitoring device is configured to calculate from a CO.sub.2 volume produced by the respirator user up to a time t, VCO.sub.2(t), the quantity of breathing lime consumed up to that time for binding this volume of CO.sub.2 or the quantity of breathing lime still remaining thereafter in the breathing lime cartridge.

9. A system in accordance with claim 5, wherein the monitoring device is configured to perform the calculations of consumed oxygen VO.sub.2(t), the work performed Q(t), the carbon dioxide produced VCO.sub.2(t) or the quantity of breathing lime consumed over the entire mission up to the current time t as a whole over continuous partial time intervals up to the time t repeatedly, or continuously in real time as current values.

10. A system in accordance with claim 1, further comprising a breathing gas cooler in the closed breathing circuit upstream of the breathing lime cartridge and in front of the breathing mask.

11. A system in accordance with claim 1, wherein the monitoring device is configured to calculate a physiological strain rate of the respirator user from current values of the oxygen consumption of the respirator user or from values of the oxygen consumption of the respirator user averaged over a time interval reaching up to the current time or from values for carbon dioxide production or respiratory minute volume, which values were derived therefrom.

12. A system in accordance with claim 11, wherein the monitoring device is configured to calculate the physiological strain rate of the respirator user from current values of the oxygen consumption of the respirator user or from values of the oxygen consumption of the respirator user which were averaged over a time interval reaching up to the current time or from values derived therefrom for carbon dioxide production or respiratory minute volume by relating the current value to the corresponding 100% of short-term performance capacity of persons in good physical condition, which 100% value was determined in advance.

13. A system in accordance with claim 11, further comprising sensors for detecting ambient temperature or ambient humidity or both ambient temperature and ambient humidity and wherein the monitoring device is configured to include the detected ambient temperature or the ambient humidity or both the ambient temperature and the ambient humidity in the calculation of the physiological strain rate.

14. A system in accordance with claim 11, wherein the monitoring device is configured to have information on the clothing of the respirator user concerning heat or moisture permeability or both heat and moisture permeability ready in the stored form and the monitoring device is configured to include the information pertaining to the clothing concerning heat or moisture permeability or both heat and moisture permeability in the calculation of the physiological strain rate.

15. A system in accordance with claim 11, wherein the monitoring device is configured to have information on the presence of a breathing gas cooler and on the cooling capacity thereof ready in a stored form and that the monitoring device is configured to include the information concerning breathing gas cooling in the calculation of the physiological strain rate.

16. A system in accordance with claim 1, wherein the monitoring device is integrated in the closed-circuit respirator and the closed-circuit respirator is configured to communicate the results of the monitoring device to the respirator user via visual, acoustic or tactile display units.

17. A system in accordance with claim 16, wherein the closed-circuit respirator is equipped with a radio transmission unit in order to be able to transmit the results of the monitoring device to a remotely located receiver.

18. A system in accordance with claim 1, wherein the monitoring device is a device, separate from the closed-circuit respirator and that the closed-circuit respirator is provided with a radio unit connected to the pressure sensor, with which the pressure values of the pressurized oxygen contained in the oxygen tank can be transmitted to the monitoring device.

19. A system in accordance with claim 18, wherein the monitoring device is provided with visual or acoustic display units in order to display the values determined by the monitoring device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In the drawings:

[0050] FIG. 1 shows a schematic block diagram of a closed-circuit respirator with monitoring device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] Referring to the drawings, the closed-circuit respirator 1 with the monitoring device has a breathing mask 2, from which the closed breathing circuit leads farther first through an exhalation tube 3 to a breathing lime cartridge 4 as a CO.sub.2 absorber. The counter-lung is established by means of a spring-loaded breathing bag 5 and the breathing gas flows through the breathing bag 5 and farther to a breathing gas cooler 6, in which the breathing gas heated in the breathing lime cartridge 4 is cooled again. The closed breathing circuit then closes via an inhalation tube 7, which leads back to the breathing mask 2. The breathing gas cooler may be present, as it is in this exemplary embodiment, but it is not necessary for the present invention.

[0052] Oxygen is dispensed constantly in the inhalation line via a constant dispensing unit 8. If the quantity of oxygen fed is not sufficient or breathing gas is lost due to leakage, the spring-loaded breathing bag 5 collapses and actuates a minimum flow control valve 9, which makes oxygen available with a high volume flow and rapidly refills the breathing bag 5. If less oxygen is consumed than is fed via the constant dispensing unit 8, the breathing bag 5 is filled to a greater extent and presses against a maximum flow control valve 10, which releases excess breathing gas into the surrounding area in front of the breathing lime cartridge. However, the constant dispensing unit is set up in the system according to the present invention such that the oxygen volume flow being fed is below the oxygen consumption of an unstressed person with certainty, so that more oxygen must be sent from time to time into the breathing bag 5 via the minimum flow control valve in order to feed a sufficient quantity of oxygen. It is thus ensured in any case that the oxygen fed from the oxygen tank 11 will be respirated and not released into the surrounding area.

[0053] The constant dispensing unit 8 and the minimum flow control valve 9 are supplied from the oxygen tank 11, which is connected to a pressure sensor 12.

[0054] The monitoring device is composed of the components with the reference numbers 13 through 15. The measured values of the pressure sensor 12 are recorded in an analysis unit 13 over time and the time curve of the oxygen consumption is calculated from this. Different data, such as, e.g., the current oxygen pressure, current oxygen consumption and remaining available service life at constant consumption, can be displayed via a display 14. The data can be sent to the mission command via a radio unit 15 and received there in a receiving unit 16 and displayed in an analysis unit 17. The current pressures, current oxygen consumption and remaining available use time can likewise be displayed in the analysis unit 17 in the mission command. These values may also be represented in the form of trends. In addition, important indications of the physiological and thermal stress of the respirator user can also be communicated there to the head of operations, for example, in the form of a traffic light. For example, the physical strain may be displayed with a color code (traffic light). The light is green in case of a low physiological strain, yellow at medium strain and red at high strain, when this mission must be expected to lead to a high thermal stress or even to exhaustion and the mission must be interrupted and the respirator user must leave the hazardous area. All these represent important pieces of information for both the respirator user himself/herself and for the responsible head of operations. This information can be detected with the system according to the present invention, because the total amount of oxygen released from the oxygen tank 11 into the closed breathing circuit is respirated in this system and the quantity of respirated oxygen can thus be detected by measuring the pressure drop and can be calculated, and further data, such as CO.sub.2 production, breathing lime consumption, etc., can then be derived from this.

[0055] While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.