Classifications

• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62B—DEVICES, APPARATUS OR METHODS FOR LIFE-SAVING
  • A62B7/00—Respiratory apparatus
  • A62B7/14—Respiratory apparatus for high-altitude aircraft
• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62B—DEVICES, APPARATUS OR METHODS FOR LIFE-SAVING
  • A62B9/00—Component parts for respiratory or breathing apparatus
  • A62B9/006—Indicators or warning devices, e.g. of low pressure, contamination
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
  • B64D10/00—Flight suits
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
  • B64D2231/00—Emergency oxygen systems
  • B64D2231/02—Supply or distribution systems

Definitions

• the present invention relates to a breathing mask for aircraft demand regulator and a dilution regulation method for protecting the occupant (passengers and/or crewmembers) of an aircraft against the risks associated with high altitude depressurization and/or smoke and fume in the cabin.
• the invention relates to the adjustment of the respiratory gas supplied to a user to satisfy the needs of the user, using a source of breathable gas supplying pure oxygen (oxygen cylinder, chemical generator or liquid oxygen converter) or gas highly enriched in oxygen such as an on-board oxygen generator system (OBOGS).
• a source of breathable gas supplying pure oxygen (oxygen cylinder, chemical generator or liquid oxygen converter) or gas highly enriched in oxygen such as an on-board oxygen generator system (OBOGS).
• OOGS on-board oxygen generator system
• the demand regulators shall deliver a respiratory gas which is a mixture of dilution gas (generally ambient air) and breathable gas depending of cabin altitude.
• a respiratory gas which is a mixture of dilution gas (generally ambient air) and breathable gas depending of cabin altitude.
• the cabin altitude reaches a value close to the aircraft altitude.
• the pressure value of the cabin is often referred to as the cabin altitude.
• Cabin altitude is defined as the altitude corresponding to the pressurized atmosphere maintained within the cabin. This value differs from the aircraft altitude which is its actual physical altitude. Correspondence between pressure and conventional altitude are defined in tables.
• the minimum rate of oxygen in the respiratory gas according to the cabin altitude is set for civil aviation by the Federal Aviation Regulations (FAR).
• FAR Federal Aviation Regulations
• PaO 2 is a difficult datum to measure on the opposite SaO 2 may be easily measure using a pulse oximeter. But once the PaO 2 reaches 80 hPa the curve is almost flat, indicating there is little change in saturation above this point. This is not a problem for passenger hypoxic protection where the targeted PaO 2 level is below 80 hPa but this is not adapted for accurate crewmember hypoxic protection where the targeted PaO 2 level is around 100 hPa.
• the purpose of this invention is to provide a demand regulator which is reliable, quite cheap, simple to settle and supplies an oxygen rate in compliance with the minimum required while being close to the minimum required.
• the invention provides a method for protecting aircraft occupant comprising the steps of:
• a respiratory gas including a mixture of breathable gas and dilution gas to the user
• the measurement of the oxygen partial pressure in the exhalation gas gives a quite good reliable estimation of the oxygen partial pressure in the alveoli PAO 2 .
• This physiological parameter which expresses the oxygen partial pressure in the lung is close to the partial pressure in the arterial blood P a O 2 when the cabin altitude is high.
• PAO 2 for adjusting the rate of oxygen in the in the respiratory gas by controlling the dilution valve take into account the physiology of the user which may differ between users. This allows a more accurate delivering of oxygen according to physiological need and regulation constraints. So, the risk of hypoxia of the aircraft occupant (in particular pilot or crewmember) and the consumption of oxygen can be reduced.
• rate, fraction, percentage or concentration are different words referring to quite the same feature.
• the method preferably comprises adjusting (regulating in closed loop) the rate of oxygen in the respiratory gas in accordance with the partial pressure or rate of oxygen or carbon dioxide in the exhalation gas.
• the method preferably comprises:
• the method further comprises:
• partial pressure or rate of oxygen and carbon dioxide in exhalation gas generated by the user enables to further optimise the consumption in oxygen, in particular by increasing the rate of oxygen in the respiratory gas when the carbon dioxide partial pressure PCO 2 in the exhalation gas decreases under a determined threshold.
• the method preferably comprises:
• the method further has the following steps:
• said coherence equation is:
• P A O 2 F
• PAO 2 is the oxygen partial pressure sensed in the exhalation gas
• PB is the barometric pressure in the aircraft
• R is a constant between 0.1 and 1 .2 corresponding to respiratory quotient.
• the method further comprises sensing the partial pressure of carbon dioxide in the exhalation gas.
• a breathable gas supply line to be connected to a source of breathable gas and supplying a flow chamber with breathable gas
• a dilution gas supply line to be connected to a source of dilution gas and supplying the flow chamber with dilution gas
• FIG. 1 represents the arterial blood saturation in accordance with the partial pressure of oxygen in the arterial blood
• FIG. 2 shows a breathing mask comprising a flow chamber
• FIG. 7 represents a second embodiment of a sensing device in accordance with the invention.
• FIG. 1 1 represents a step of a method according to the invention using the sensing device of the fifth embodiment
• the exhalation line 18 is in communication directly or through the respiratory chamber 9 with the respiratory gas supply line 16. Therefore, the gas supply line 16, the respiratory chamber 9 and the exhalation line 18 define a flow chamber 30 without separation.
• the gaseous content of the first gas mixture 32 being different from the second gas mixture 34, the second gas mixture 34 disturbs the measurement of the characteristic of the gaseous content of the first gas mixture 32.
• the first gas mixture and the second gas mixture may content the same constituents (at least some identical constituents), and only differ in the percentage of some of the constituents (in particular percentage of oxygen, carbon dioxide and steam).
• the oxygen sensor providing measurement 42c is not appropriate. So, the shorter the response time of the gas sensor is, the more accurate the measurement is. But, a gas sensor with a short time response is generally more expensive than a sensor with a longer time response, and sometimes a gas sensor with a time response satisfying for a particular application does not exist.
• the shutter 50 is movable between an active position in which it closes the passage 66 and an inactive position in which it is away from the passage 66.
• the flow direction sensor 38 includes in particular a pressure sensor, a pressure gauge sensor, a pressure differential sensor, thermistances, a sensor of the state of a check valve or a piezo sensor device comprising a flexible sheet and detecting the direction of the curvature of the flexible sheet.
• the oxygen sensor 42 comprises a pumping plate 44, a first disk of solid ionic conductor 45, a common plate 46, a second disk of solid ionic conductor 47 and a sensing plate 48.
• the pumping plate 44, the common plate 46 and the sensing plate 48 are electrodes preferably made of platinum films.
• the ionic conductors 45, 47 define solid electrolyte. They are preferably made in dioxide zirconium suitably adapted for the conduction of ions of oxygen O 2 .
• the oxygen sensor 42 may be placed either in the respiratory chamber 9, in the respiratory gas supply line 16 or in the exhalation line 18, and of any of the first to fourth embodiment described above.
• a pressurisation phase 26 corresponds to a phase of pumping current i equal to -Ip. So, the partial pressure in Oxygen PO2 in the sensing chamber 40 increases and the Nerst voltage Vs between the sensing plate 48 and the common plate 46 decreases.
• the transportation of the oxygen through the ionic conductor 45 during the pressurisation phase 26 creates a pressure drop in the buffer chamber 41 .
• the low porosity of the external filter 49 limits the entry of the ambient gas into the sensor and is responsible of the main delay (high response time) in the oxygen partial pressure measurement.
• an evacuation phase 28 is achieved.
• the pumping current i is preferably lower than during the evacuation phase 28 of the measurement period 52, i.e. lower than Ip. Therefore, the evacuation phase 28 of the period without measurement 54 lasts during all the period without measurement 54 or at least more than half of the period without measurement 54.
• the control device 60 determines the fraction of oxygen in the respiratory gas 62 and the oxygen partial pressure in the exhalation gas 64.
• the dilution adjusting device 24 adjusts the rate of oxygen in the respiratory gas 62 in accordance with the oxygen partial pressure PO2 or rate of oxygen in the exhalation gas 64, sensed by the oxygen sensor 42 of one of the sensing devices 100 above described.
• oxygen sensors currently available can provide directly either the oxygen partial pressure or the rate of oxygen, and that oxygen partial pressure PO2 is equal to the rate of oxygen multiplied by the barometric pressure sensed by the cabin altitude sensor 71 .
• the dilution valve 23 is preferably controlled in closed loop with a Proportional Integral Derivative (PID) controller included in the control device 60, in order to adjust the oxygen partial pressure PO2 in the exhalation gas 64 sensed by the oxygen sensor 42 in accordance with the cabin altitude sensed by the cabin altitude sensor 71 , optionally in accordance with the aircraft altitude sensed by the aircraft altitude sensor 72 and preferably in accordance with the carbon dioxide partial pressure PCO2 in the exhalation gas 64 sensed by the carbon dioxide sensor 68.
• PID Proportional Integral Derivative
• the rate of oxygen in the respiratory gas 62 has to be increased when the carbon dioxide partial pressure PCO 2 in the exhalation gas 64 decreases under a determined threshold.
• PAO 2 for adjusting the rate of oxygen in the in the respiratory gas 62 by controlling the dilution valve take into account the physiology of the user which may differ between users. This allows a more accurate delivering of oxygen according to physiological need and regulation constraints. So, the risk of hypoxia of the aircraft occupant (in particular pilot or crewmember) and the consumption of oxygen can be reduced.
• the content of respiratory gas delivered by the dilution adjusting device 24, 38, 42, 60 is diluted inside the lung capacity.
• the dynamic of the dilution adjusting device 24, 38, 42, 60 using a close loop control may be very slow (around 0.1 Hz). Consequently this will simplify dilution valve 23 and the oxygen sensor 42.
• the adjusting device 24 and in particular dilution valve may be advantageously replaced by at least one more sophisticated adjusting device such as disclosed in the patent application PCT/IB201 1 /000772 incorporated herein by reference.
• the control device determines coherence between the fraction of oxygen in the respiratory gas 62 and the oxygen partial pressure in the exhalation gas 64.
• the control device 60 determines the fraction of oxygen in the respiratory gas 62 and the oxygen partial pressure in the exhalation gas 64.
• PB is the barometric pressure in the cabin 1 0 of the aircraft
• R is a constant corresponding to respiratory quotient.
• the partial pressure of oxygen in the alveolar gas may be approximated to partial pressure of oxygen in the exhalation gas 64.
• the partial pressure of carbon dioxide PACO 2 in the exhalation gas 64 is preferably sensed by the carbon dioxide sensor 68. Otherwise, the partial pressure of carbon dioxide PACO 2 may be replaced by a constant close to 53 hPa, as it is generally quite close to this value.
• the partial pressure of water PAH 2 O is in the exhalation gas 64 may be replaced by a constant close to 63 hPa at the temperature of the alveolar gas (estimated to 37°C).
• alveolar gas equation may be simplified into a following coherence equation:
• Failure is determined by comparison with a range value with a ratio between the measured value and the value estimated (partial pressure of oxygen in the in the exhalation gas 64 or the rate of oxygen in the respiratory gas 62) by the coherence equation. In case of failure determined a warning alarm is activated.
• the partial pressure of oxygen in the exhalation gas 64 is sensed with the same gas (oxygen) sensor 42 as the oxygen sensor 42 which enables the control device 60 to determine the rate of oxygen in the respiratory gas 62 by sensing the partial pressure of oxygen in the respiratory gas 62.
• oxygen oxygen

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• Health & Medical Sciences (AREA)
• Pulmonology (AREA)
• General Health & Medical Sciences (AREA)
• Business, Economics & Management (AREA)
• Emergency Management (AREA)
• Engineering & Computer Science (AREA)
• Aviation & Aerospace Engineering (AREA)
• Respiratory Apparatuses And Protective Means (AREA)

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Citations (11)

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• 2011
  • 2011-09-01 BR BR112013021766A patent/BR112013021766B1/pt active IP Right Grant
  • 2011-09-01 CA CA2827253A patent/CA2827253A1/en not_active Abandoned
  • 2011-09-01 WO PCT/EP2011/065158 patent/WO2012116764A1/en active Application Filing
  • 2011-09-01 EP EP11758429.2A patent/EP2680926A1/en not_active Withdrawn

Patent Citations (11)

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