AT509551B1 - CIRCULAR DIVING UNIT WITH A MOUTHPIECE - Google Patents

Description

Austrian Patent Office AT 509 551 B1 2012-01-15

Description: The invention relates to a rebreather with a mouthpiece which is connected to a breathing gas circuit via an inhalation hose and an exhalation hose, wherein at least one gas sensor for measuring the partial pressure of a respiratory gas component is arranged in the respiratory gas circuit.

One differentiates between open diving equipment, semi-closed and closed rebreather devices.

Open diving devices have a Atemgasvorratsflasche, which is filled with compressed air or other breathing gas mixture, and a one- or two-stage pressure reducer, which reduces the pressure of the gas in the bottle to ambient pressure. The exhaled air is released into the surrounding water, but only a small part of the oxygen in the breathing gas is really consumed. Thus, about 3% of the inhaled gas is consumed at the water surface, while at a depth of, for example, 20 meters through the increased by two bar ambient pressure only a third of this value, ie 1% of the oxygen of the inspired gas is consumed. Thus, for a dive to a depth of twenty meters, one hundred times as much breathing gas has to be carried along as it actually consumes.

In order to circumvent the systemic, the respiratory gas consumption, low efficiency of open diving equipment, semi-closed and closed rebreathers are used. These devices are breathed in a cycle. The exhaled air is purified in rebreathers by means of a C02 absorber of carbon dioxide and re-enriched with oxygen. Furthermore, such devices are characterized by a one- or two-part counterlung, which can absorb the exhaled gas volume. With rebreathers, the efficiency of gas consumption can be increased up to 100%.

While in open diving equipment normally a gas is breathed with breathable oxygen content, semi-closed rebreathers the oxygen partial pressure (p02) is determined in the cycle of the amount of gas supplied and the metabolism of the diver. In electronically controlled closed devices, the oxygen partial pressure is kept at a certain level by means of a control loop. Electronically controlled closed rebreathers are known, for example, from the publications GB 2 404 593 A, US 2003/188744 A1 and WO 2005/107390 A2. In manually controlled closed rebreathers, the diver manually sets the oxygen supply and thus manually controls the oxygen partial pressure. In an electronically controlled closed cycle device, oxygen is usually metered in with an electromagnetic control valve. This solenoid valve is usually housed in the housing of the carbon dioxide filter. The actual control loop is implemented in one or - for redundancy reasons - in several microcontrollers. The oxygen partial pressure of the breathing gas must be within certain limits in order to be breathable. Generally, 0.16 bar is considered the lower limit and 1.6 bar the upper limit. An oxygen partial pressure below or above these limits is classified as life-threatening. It can be seen that a constant monitoring of the oxygen partial pressure is necessary for rebreathers. Closed units require p02 sensors for manual and / or electronically controlled regulation of the oxygen partial pressure in the breathing gas circuit. The p02 sensors used are usually electrochemical liquid-electrolyte sensors which have to be calibrated at the surface with air or 100% O 2 before the dive.

A correctly functioning p02 sensor for use in rebreathers has an output signal (current or voltage), which depends linearly only on the oxygen partial pressure in front of the membrane of the sensor.

However, pO 2 sensors designed as liquid electrolyte sensors are very error-prone. Typical errors that may occur are: 1/8 Austrian Patent Office AT 509 551 B1 2012-01-15 · Nonlinearity; Current limitation: in this case, the p02 sensor becomes non-linear from a certain oxygen partial pressure because the output current of the sensor (or output voltage) can not rise above a certain level due to an error. This results in too low sensor signals at high oxygen partial pressure; Faulty signals from one or more sensors or the Sensorignalverar processing; [0011] incorrect calibration; The susceptibility of the p02 sensors to failure is attempted with the redundant use of p02 sensors. Thus, in closed rebreathers usually 3 oxygen sensors are used. If one sensor fails and therefore its output signal differs from that of the other two, this is determined by comparing all three sensor signals with a "voting algorithm". detected, and this sensor is no longer used to control the p02 (see GB 2 404 593 A or WO 2004/112905 A1).

A faulty sensor can be determined. However, this method fails with the following errors: Failure of 2 sensors, which, however, have the same output signal; · Same nonlinearity of at least 2 sensors (> = 2 sensors from the same

Production batch, same age, equal conditions ...); · Same Stromlimitierung of at least 2 sensors.

An alternative is described in WO 2008/080948 A2. A calibration / validation device allows the flow of an oxygen sensor with a gas of known composition. Thus, a sensor can be easily checked for correct function.

In addition to the susceptibility to error 02 liquid electrolyte sensors have other disadvantages: Short life of about 1.5 years; · Can provide faulty signals at high humidity (condensation on the

Sensor membrane); Electrolyte can leak from the sensor housing; · Long response times (t90) of typically 6 s; Relatively large dimensions; The relatively long response time makes a regulation of the oxygen partial pressure relatively difficult. In a closed rebreather, the oxygen partial pressure is usually measured with oxygen partial pressure sensors and then with the aid of a control circuit (usually with a microcontroller) an electromagnetic control valve is activated, with which oxygen is supplied from a supply bottle to the circuit. In the worst case, this can temporarily lead to high oxygen partial pressure spikes in the circuit, which must be regarded as life-threatening, but are not recognized with the conventional sensors due to their long response time, since the long response time causes an averaging of the signal.

A carbon dioxide absorber (chemical filter, soda lime, carbon dioxide filter, scrubber) absorbs the exhaled carbon dioxide in a rebreather. A proper function of the carbon dioxide absorber is vital, since with an increase in the carbon dioxide content in circulation threatens carbon dioxide poisoning, which in turn is classified as life-threatening. The following faults may occur: respiratory limestone is defective 2/8 Austrian Patent Office AT 509 551 B1 2012-01-15 · Maximum absorption capacity has been reached, no further carbon dioxide can be taken up; ♦ The absorber is too cold and the chemical reaction takes place only insufficient; · Water has entered the circuit and thereby the soda lime was unusable; · Directional valves in the mouthpiece are defective - it comes to pendulum breathing and the

Carbon dioxide filter is not flowed through, so no carbon dioxide can be absorbed.

Many projects have dealt with the development of a CO2 sensor for rebreathers to detect a malfunction of the carbon dioxide filter and / or an increase of CO2 in the circuit. Optical C02 sensors are mostly based on the absorption of infrared light. However, due to the high humidity (condensing) in a rebreather, this method is not very reliable. It is known to arrange a moisture barrier or hydrophobic membrane to increase the reliability in front of the measuring cell of the infrared C02 sensor. Another way to increase the reliability of such C02 sensors is to increase the sensors / sensor element to a temperature greater than the gas temperature in the rebreather to preclude condensation. Furthermore, to check the function of the carbon dioxide absorber, the temperature of the carbon dioxide filter can be measured (US 2003/074154 A1).

DE 10 2007 039 124 A1 describes a device and a method for controlling and / or regulating a training and / or rehabilitation unit. In addition to a training and rehabilitation unit, a microcontroller and a brake or resistance arrangement, this device contains a sensor unit with a heatable electrochemical solid electrolyte sensor for determination of oxygen concentration and a further heatable electrochemical solid electrolyte sensor for determining the concentration of carbon dioxide.

[0033] In the article "Solid State Electrolyte Sensors for the Determination of Oxygen, Carbon Dioxide, and Total Flow Rates Associated to Respiration in Human Subjects", edited by S. Fasoulas; Executive Summary to the ESTEC Contract no. 15450/01 / NL / JS, CCN 1,2,3; Report No. ILR-RSN P 06-07, 13th October 2006 (available online at http://www.ibtk.de/project/rss/PR03-FR-Exec-Sum_17102006.pdf) the use of solid-state electrolytes for the determination of 02- and C02 concentrations, as well as other applications discussed and presented. Among other things, from this publication, an arrangement with built-in a pipe piece 02 and C02 sensors is known, wherein the pipe section is connected via a filter with a breathing mask. Thus, inhaling and exhaling through the same blank (Figure 35). The sensor electronics are housed in a separate housing.

A rebreather usually has an inhalation and an exhalation hose. In between, the mouthpiece is mounted, in which two directional valves are arranged. The main focus in the construction of rebreathers is, among other things, a construction of a mouthpiece in which the so-called dead space, which is understood as meaning the space between the directional valves and the bite piece, is minimized. This is important because otherwise there is a risk that the CO 2 content in the dead space increases. This is especially a problem when the diver is breathing very shallow. An integration of a piece of pipe, as described in said article, is disadvantageous in a diving device or an additional risk factor, because this would increase the dead space, especially taking into account that in cross-section diving devices, the cross sections of the gas supply and discharge approx. 15 cm2 in order to allow even at greater depths a minimal work of breathing (WOB = "work of breathing").

JP 2005 350 282 A, US Pat. No. 5,746,806 A and also US Pat. No. 5,071,453 A essentially disclose oxygen concentrators which, inter alia, also use a zirconia-solid electrolyte sensor. It is the object of the invention to avoid the mentioned sources of error in the partial pressure measurement of gas components in the respiratory gas.

According to the invention, this object is achieved in that the gas sensor is designed as a solid electrolyte sensor, wherein at least one solid electrolyte sensor is arranged in the mouthpiece. The solid-state electrolyte sensor can be embodied as 02 and / or as a CO 2 gas sensor.

Solid-state electrolyte sensors are based on special materials which are conductive for gas ions. Normally, however, these materials are conductive only at elevated temperatures (typically 500-700 ° C). Typical materials include zirconia and ceria for oxygen and nasicon for c02.

Potentiometric solid electrolyte sensors for oxygen have long been known, and are used, inter alia, in engine controls (lambda sensor) or in industrial combustion controls.

Conventional sensors such as e.g. used in a car, but have the disadvantage that they are relatively large, therefore, require a high electrical heating power (> 10Watt) and a reference measuring chamber with a reference gas is necessary (potentiometric sensors, Nernst potential). These disadvantages have not permitted the use of these sensors in rebreathers until today.

Miniaturized gas sensors are used inter alia for in-situ and bypass measurements of Ox, COx, H2, CxHy, NOx in medical and environmental engineering, e.g. used in the performance diagnostics of astronauts or for residual gas analysis in space (see http: // tu-dresden. de / die_tu_dresden / fakultaeten / fakultaet_maschinenwesen / ilr / rsn).

Thick-film miniature solid-state electrolyte sensors have the advantage of a long service life and a very fast response time. The actual sensor elements are available in the size 2.5x2.5x2mm3 and can be easily integrated into a rebreather. Due to the small design only low heat outputs (1-2 watts) are required, which allows conventional batteries or rechargeable batteries to operate for several hours.

The high operating temperature prevents condensation-related disturbances. The fast response time allows precise control of the oxygen partial pressure. The high response speed of less than 100 ms even allows to determine the heart rate, as the p02 / pC02 signal of the exhaled air is modulated with the heart rate.

The small dimensions allow integration of the gas sensors directly in the mouthpiece. Thus, the oxygen partial pressure of inhaled and exhaled gas can be detected separately. Favorable placement in the gas stream can also be used to measure the mass of the gas with these solid-state electrolyte sensors and thus deduce the minute volume of the diver and the respiratory rate. The high temporal resolution of the sensors allows a high-precision determination of small and short-term oxygen partial pressure changes.

By recording minute volume and respiratory rate, the load of the diver can be detected and this in turn can be used as an influencing factor for the decompression calculation.

Planar miniature solid-state electrolyte sensors for the partial pressure measurement of CO 2 and O 2 thus have the following properties: Very fast response time <100 ms; Operating temperature 650 ° C (02) and 550 ° C (C02). Due to the high operating temperature problems with high / condensing humidity can be excluded; · 02 sensor: unlimited life; 4/8 Austrian Patent Office AT 509 551 B1 2012-01-15 · C02 sensor: ~ 2000 operating hours; The 02 sensor is an amperometric sensor - thus no Referenzmesskam mer is necessary; · In the C02 sensor, a solid electrolyte reference is integrated, so this requires no

Reference chamber; Low operating costs; Sensors are very small (actual sensor element ~ 4mm2); The high response rate even allows to determine the heart rate, since the p02 / pC02 signal of the exhaled air is modulated with the heart rate.

By employing an O 2 and a C 2 O solid electrolyte sensor in a rebreather, the following advantages are obtained: [0059] [0061] [0062] [0064] [0065] 0066] [0074] [0074] [0074] [0074] [0074] [0074] [0074] High operational safety, since the sensors are very robust and error-resistant; • Because the sensors are very small, they can also be integrated directly into the mouthpiece of a rebreather; • Since the sensors have a very short response time (<100ms), o the oxygen partial pressure in the system can be better and more accurately controlled; o measure differences in the gas composition of inhaled and exhaled gas (when integrated in the mouthpiece); o This allows conclusions about the oxygen metabolism of the diver. • Because the sensors are kept at high temperature, they can be used as gas mass flow meters. By appropriate placement of the sensors in the gas flow, the gas flow can be measured (inhalation and exhalation volume, minute volume), which allows: o conclusion on the activity of the diver (stress, high physical stress, ...); o Determining if the diver is breathing at all, and how fast-which, in turn, can be used as input to the controller. • The following can be checked with a C02 sensor: o Correct function of the C02 filter; o Correct operation of the directional valves in the rebreather (if the directional valves are damaged, this can quickly lead to a local C02 increase (C02.-buildup) o conclusions on the metabolism of the diver (high physical stress, stress, ...) o Checking the oxygen sensor: Normally, the difference between the oxygen partial pressure of the inhaled and expired gases should be approximately equal to the difference in the partial pressure of carbon dioxide.

The large number of advantages thus allows o an optimized control of the oxygen supply; o Recording of physiological data (metabolism, tidal volume, minute volume, respiratory rate, O 2 content in inhaled and exhaled gas, CO 2 in exhaled gas) - this can be used • to check the oxygen control; • find influence in the decompression calculation (important point); O Increased safety of the system by different sensor systems (02, C02 and mass flow sensor) Electronic circuits are necessary for controlling and reading out the sensors. These usually consist of a microcontroller that takes over the heating control and an analogue circuit, which typically consists of amplification and analogue filters. With today's technology, such a circuit can be highly miniaturized, so that the entire electronics requires less than 1-2 cm3 of space. Such a small circuit can easily be placed directly next to the sensors in the mouthpiece.

Using miniaturized solenoid valves, the control valve for oxygen feed into the breathing circuit can also be integrated directly into the mouthpiece.

Thus, together with a miniaturized electronic control unit, the complete control circuit of the rebreather can be integrated in the mouthpiece.

By integrating the complete control electronics and the control valve in the mouthpiece, there are numerous advantages: o no long cables and thus signal distortions caused because sensors,

Solenoid valve, electronics and power supply (battery) are integrated directly next to each other; O cost-effective design; O The mouthpiece contains all the electronics. Rebreathers without electronic control can be easily upgraded by replacing the original mouthpiece with the fully integrated mouthpiece. [0084] The invention will be explained in more detail below with reference to the figures.

FIG. 1 shows a known rebreather and FIG. 2 shows a part of a rebreather according to the invention. [0087] FIG.

Fig. 1 shows a closed rebreather according to the prior art. The diver exhales through the bite piece 19 connected to the mouthpiece 1 via the exhalation hose 2 into the exhalation counterlung 4. In C02 filter 7 ("scrubber"), carbon dioxide is chemically absorbed from the exhaled air. The respiratory gas then passes into the inhalation region 5. Via the bite piece 19 of the mouthpiece 1 and the inhalation hose 3, the respiratory gas is inhaled again. In order to replace the consumed oxygen, fresh 02 gas is supplied to the breathing gas circuit from an oxygen storage bottle 11 via an electromagnetic control valve 9, which is usually accommodated in the housing of the CO 2 filter 7. A pressure reducer 12 reduces the cylinder pressure to a pressure of typically 7-10 bar. The storage bottle 11 contains pure oxygen 02. In addition to the electromagnetic control valve 9, the control circuit also has a microcontroller 10 and one to four oxygen sensors 8, via which the oxygen partial pressure p02 in the breathing gas cycle is measured. Dive relevant data are displayed on a display 15. If the partial pressure of oxygen drops below a certain value, then pure oxygen 02 is added to the respiratory gas cycle via the electromagnetic control valve 9. When diving, the breathing gas is compressed in the breathing gas circulation. To compensate for the pressure-related loss of volume, diluent gas from a supply bottle 13 is supplied to the breathing gas circuit 26 via a manual valve 16 or an automatic valve. Via the two pressure reducers 12, 14, the cylinder pressure is reduced to typically 8-10 bar above atmospheric pressure. Excess gas can escape through a pressure relief valve 6.

Fig. 2 shows a simple embodiment of the invention. The integrated mouthpiece 1 is connected via a breathing tube 3 and an exhalation hose 2 to the breathing gas circuit 26. The two directional valves - inhalation valve 18 and exhalation valve 17 - specify the gas flow direction. With 19 the actual rubber bite piece is designated, which is the 6/8

Claims (8)

Austrian Patent Office AT 509 551 B1 2012-01-15 Diver holding his teeth. The O 2 sensor 20 and the CO sensor 21 are designed as solid electrolyte sensors and mounted in the cavity of the mouthpiece 1 between the directional valves 17, 18. By means of a control valve 23 formed by a miniature solenoid valve, which replaces the control valve 9 of FIG. 1, oxygen can be supplied to the breathing gas circuit 26 via an opening 27 from an oxygen storage bottle and an oxygen supply line 24 which are not shown in FIG. The feed into the breathing gas circuit 26 takes place after the exhalation valve 17 in order to guarantee a good mixing and at the same time to avoid short-term peak increases in the oxygen partial pressure in the inhaled gas. The control of the control valve 23 via an electronic control unit 22 via a waterproof cable 25, a display unit and an external battery power can be connected. The electronic control unit 22 and the control valve 23 are water and pressure-tight integrated in the mouthpiece 1. In the context of the invention, further options can be provided. Thus, a disc or roller-like closure for the bite piece may be integrated into the mouthpiece 1 in the event that the diver removes the bite piece 19 from the mouth. Furthermore, it is conceivable to integrate a switching roller in the mouthpiece 1, which allows switching from closed circuit to open circuit. In this case, a so-called second stage (low-pressure stage) of an open dipping system is expediently integrated into the mouthpiece 1. The second stage can also act as an auto diluent control valve in closed mode. 1. Rebreather with a mouthpiece (1) which is connected via a inhalation hose (3) and an exhalation hose (2) to a breathing gas circuit (26), wherein in the breathing gas circuit (26) at least one gas sensor for measuring the partial pressure of a respiratory gas component is arranged , characterized in that the gas sensor is designed as a solid electrolyte sensor, wherein at least one solid electrolyte sensor in the mouthpiece (1) is arranged. 2. Rebreather according to claim 1, characterized in that at least one solid electrolyte sensor is designed as an O 2 sensor (20). 3. Rebreather according to claim 1 or 2, characterized in that at least one solid electrolyte sensor is designed as a C02 sensor (21). 4. rebreather according to one of claims 1 to 3, with at least one in the breathing gas circuit (26) via an electrical control valve (23) opening oxygen supply line (24), characterized in that preferably designed as Minimagnetventil electrical control valve (23) in the mouthpiece ( 1) is arranged. 5. rebreather according to claim 4, characterized in that the oxygen supply line (24) in the mouthpiece (1) in the breathing gas circuit (26), preferably in the exhalation hose (2) downstream of an exhalation valve (17), opens. 6. Rebreather according to one of claims 1 to 5, characterized in that an electronic control unit (22) connected to the gas sensor and / or to the electrical control valve (23) is integrated in the mouthpiece (1). 7. rebreather according to claim 6, characterized in that the electronic control unit (22) is connected to an external display unit and / or an external power source. 8. Rebreather according to one of claims 1 to 7, characterized in that at least one battery for powering the electronic control unit (22) in the mouthpiece (1) is arranged. For this 1 sheet drawings. 7.8