as) United States
`a2) Patent Application Publication 10) Pub. No.: US 2007/0271009 Al
`(43) Pub. Date: Nov. 22, 2007
`
`Conroy, JR.
`
`US 20070271009A1
`
`(54) SYSTEM AND METHOD FOR MONITORING
`PASSENGER OXYGEN SATURATION
`LEVELS AND ESTIMATING OXYGEN
`USAGE REQUIREMENTS
`
`(76)
`
`Inventor:
`
`John D. Conroy JR., Harrisburg, PA
`(US)
`
`Publication Classification
`
`(51)
`
`Int. CL
`(2006.01)
`G06F 17/00
`(2006.01)
`A62B 7/14
`(52) US. CMe
`cssccssscsssecsssessssessseestenssssessestenssee 701/10
`
`(57)
`
`ABSTRACT
`
`Correspondence Address:
`MCNEES WALLACE & NURICK LLC
`100 PINE STREET
`P.O. BOX 1166
`
`HARRISBURG,PA 17108-1166 (US)
`
`A device performs oxygen flight planning calculations for
`estimating oxygen usage. The device includes a storage
`device, an input device for inputting a knownflight param-
`eter value into the storage device, and an output device for
`outputting the known flight parameter value input by the
`input device. A logic device is configured to control the
`storage device,
`the input device,
`the output device and
`(21) Appl. No.:—11/764,615
`provide to the output device a further flight parameter. A
`value of the furtherflight parameteris calculable by the logic
`device from the known flight parameter value previously
`input into the storage device. Upon the further flight param-
`eter being selected by use of the input device, the logic
`device calculates the value of the further flight parameter
`and provides the value of the further flight parameter to the
`output device.
`
`(22)
`
`Filed:
`
`Jun. 18, 2007
`
`Related U.S. Application Data
`
`(62) Division of application No. 10/697,785, filed on Oct.
`30, 2003, now Pat. No. 7,246,620.
`
`SHUT OFF 02
`RESET 1st TIME
`REF DEACTIVATE
`ist, Sth WARNING
`
`CONFIRMATION
`READINGS?
`
`
`
`
`
`
`TRANSMIT DATA TO
`
`
`DATA STORAGE
`
`
`92
`START 1st TIME REF
`
`
`
`IF NOT ALREADY ON.
`
`
`
`EMERGENCY
`PROCEDURES INITIATED
`
`APPLE 1011
`
`APPLE 1011
`
`1
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 1 of 21
`
`US 2007/0271009 Al
`
`100
`
`90
`
`_ 80
`x
`
`70
`
`60
`50
`40
`30
`
`20
`
`10
`
`0
`
`0
`
`20
`
`60
`40
`PO. (TORR)
`OXYGEN DISSOCIATION CURVE
`
`80
`
`100
`|
`
`FIG-1
`
`= Oi
`
`se
`2
`Ww
`~
`Lid
`S
`“<
`©
`
`2
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 2 of 21
`
`US 2007/0271009 Al
`
`
`STORED
`
`
`PERSONALIZED
`DATA/FLIGHT DATA
`
`
`
`START CUMULATIVE
`CLOCK
`
`20
`
`ae
`
`)
`
`TAKE MONITORING
`DEVICE AND
`PRESSURE READINGS
`
`26
`
`(D)
`
`TRANSMIT SIGNAL
`TO LOGIC DEVICE
`
`32
`
`FIG-2A
`
`3
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 3 of 21
`
`US 2007/0271009 Al
`
`
`
`TRANSMIT DATA TO
`DATA STORAGE
`
`
`SHUT OFF 02
`
`SUFF.
`
` YES7SAQ9>
`RESET 1st TIME
`
`CONFIRMATION
`REF DEACTIVATE
`
`READINGS?
`
`ist, Sth WARNING
`
`
`(A)
`
`41
`
`
`
`YES
`
`ACTIVATE 1st WARNING
`
`50
`
`TRANSMIT DATA TO
`DATA STORAGE
`
`
`SUPPLY O9
`TO PASSENGER
`
`
`
`START ist TIME REF
`iF NOT ALREADY ON.
`
`
`93 94
`
`
`
`PASSENGER
`
` RESET 1st TIME REF
`DEACTIVATE 1st
`
`
`TIME REF?
`
`
`
`
`INITIATE Sth WARNING
`
`
`FIG-—2B
`
`YES
`
`EMERGENCY
`PROCEDURES INITIATED]
`
`|
`
`4
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 4 of 21
`
`US 2007/0271009 Al
`
`
`
`SUFF.
`
`
`
`CONFIRMATION
`ALT. > PERS.
`
`READINGS?
`DATA ALT.?
`
`
` 71
`
`ACTIVATE 3rd
`WARNING
`
`3rd WARNING
`OFF (IF ON)
`
`
`74
`Oo OFF 4th
`
`WARNING
`
`SUFF.
`
`OFF
`IS_ CABIN
`CONFIRMATION
`
`
`
`
`ALT.>12.5K?
`READINGS?
`RESET 2nd
`
`
`
`
`REC, TIME
`
`REF
`
`
`4th WARNING ON
`
`
`O> ON (ALL PASSENGERS)
`IS CABIN
`ALT.>14K?
`
`
`
` START 2nd TIME
`
`REF (IF OFF)
`
`
`
`
` IS
`2nd TIME
`
`REF > 30
`
`
`MIN?
`
`FIG-—2C
`
`5
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 5 of 21
`
`US 2007/0271009 Al
`
`STORED
`
`PERSONALIZED DATA/FLIGHT DATA
`
`ENCODE DATA
`
`START CUMULATIVE
`CLOCK
`
`20
`
`122
`
`lev
`
`(B)
`
`TAKE MONITORING
`DEVICE AND
`PRESSURE READINGS
`
`126
`
`(D)
`
`TRANSMIT SIGNAL
`TO LOGIC DEVICE
`
`32
`
`FIG—-3A
`
`6
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 6 of 21
`
`US 2007/0271009 A1
`
`
`
`TRANSMIT DATA TO
`DATA STORAGE
`
`
`
`SHUT OFF 02
`SUFF.
`
`
`YES/SA09>
`RESET 1st TIME
`CONFIRMATION
`
`
`REF DEACTIVATE
`
`READINGS?
`
`
`Ist, Sth WARNING
`
`
`
`(A)
`
`4i
`
`
`
`TO PASSENGER:
`
`
`SUPPLY O
`
`44
`
`YES
`
`ACTIVATE 1st WARNING
`
`150
`
`TRANSMIT DATA TO
`DATA STORAGE
`
`
`
`START ist TIME REF
`IF NOT ALREADY ON
`
`
`
`
`93
`
`
`RESET 1st TIME REF
`
`
`
`96
`
`95
`
` YES
` EMERGENCY
`PROCEDURES INITIATED
`
`7
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 7 of 21
`
`US 2007/0271009 Al
`
`162
`
`(C)
`
`65
`
`(D)
`
`
`
`
`SUFF.
` ALT. > PERS.
`
`
`CONFIRMATION
`DATA ALT.?
`READINGS?
`
`
`
`
`3rd WARNING
`
`OFF (IF ON)
`
`04
`Oo OFF 4th
`
`
`SUFF.
`WARNING
`
`
`
`IS CABIN
`CONFIRMATION
`OFF
`
`
`
`ALT.>12.5K?
`READINGS?
`RESET 2nd
`
`
`
`REC. TIME
`
`
` REF
`
`
`NO
`
`
`
`171
`
`ACTIVATE 3rd
`WARNING
`
`89
`
`
`
` IS CABIN
`YES! 0 ON (ALL PASSENGERS)
`
`
`ALT.>14K?
`
`4th WARNING ON
`
`
`
`
`
`IS
`
`2nd TIME
`
`REF > 30
`MIN?
`
`
`
`
`
`
`FIG-—3C
`
`8
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 8 of 21
`
`US 2007/0271009 Al
`
`
`STORED
`
`PERSONALIZED
`
`DATA/FLIGHT DATA
`
`
`ENCODE DATA
`
`START CUMULATIVE
`CLOCK
`
`325
`
`LOGIC DEVICE
`PROMPT FOR
`READINGS
`
`(B)
`
`TAKE MONITORING
`DEVICE AND
`
`PRESSURE READINGS
`
`20
`
`122
`
`127
`
`126
`
`(D)
`
`TRANSMIT SIGNAL
`TO LOGIC DEVICE
`
`32
`
`FIG—4A
`
`9
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 9 of 21
`
`US 2007/0271009 Al
`
`LOGIC DEVICE PROMPT
`
`FOR READINGS
`
`59
`(A)
`
`
`
`,
`TRANSMIT DATA TO
`
`
`
`SHUT OFF 02
`DATA STORAGE
`RESET ist TIME
`NO
`
`
`REF DEACTIVATE
`
`
`ist, Sth WARNING
` SUFF.
`CONFIRMATION
`
`
`
`
`©
`
`360
`
`Al
`
`SIGNAL TO A/C
`-_ COMPUTER
`
`READINGS?
`
`
`
`
`
`
`
`
`
`
`
`
`SIGNAL TO A/C
`COMPUTER
`
`ACTIVATE 1st WARNING
`
`SUPPLY O5
`TO PASSENGER
`
`RESET 1st TIME REF
`
`‘96
`
`INITIATE Sth WARNING
`
`EMERGENCY
`PROCEDURES INITIATED
`FIG—4B
`
`YES
`
`SIGNAL TO'A/C ~
`COMPUTER
`
`10
`
`10
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 10 of 21
`
`US 2007/0271009 Al
`
`
`
`
`
`
`
`SUFF.
`CABIN
`ALT. > PERS.
`CONFIRMATION
`
`
`
`READINGS?
`DATA ALT.?
`
`
`
`
`
`YES
`367
`
`. 366
`
`
`
`378
`
`
`
`
`ACTIVATE 3rd
`
`SIGNAL TO A/C
`WARNING
`
`
`
`
`COMPUTER
`O> OFF 4th
`
`74
`
`
`WARNING
`SUFF.
`
`
`
`
`IS_ CABIN
`CONFIRMATION
`OFF
`
`
`
`ALT.>12.5K?
`READINGS?
`RESET 2nd
`
`
`
`REC. TIME
`
`
`REF
`
`
`
`Oo ON (ALL PASSENGERS)
`IS CABIN
`
`4th WARNING ON
`
`SIGNAL TO A/C |
`COMPUTER
`
`171
`
`SIGNAL TO A/C
`COMPUTER
`
`|
`
`3rd WARNING
`OFF (IF ON)
`
`SIGNAL TO A/C
`COMPUTER
`
`ALT.>14K?
`
`11
`
`11
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 11 of 21
`
`US 2007/0271009 A1
`
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`

`Patent Application Publication Nov. 22,2007 Sheet 12 of 21
`
`US 2007/0271009 Al
`
`BLOOD SATURATION
`MONITORING DEVICE
`
`CABIN PRESSURE ALTITUDE
`
`MONITORING DEVICE
`
`
`
`O, SUPPLY
`LOGIC DEVICE
`
` WARNING DEVICE
`
`MEMORY DEVICE
`
`
`
`FIG—6
`
`410
`
`404
`
`13
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 13 of 21
`
`US 2007/0271009 Al
`
`OUTPUT DEVICE
`
`SENSORS
`a
`
`INPUT DEVICE
`
`AIRCRAFT
`COMPUTER
`
`LOGIC DEVICE
`
`MEMORY
`DEVICE,
`
`WEATHER
`DATA
`
`WARNING
`DEVICE
`
`BLOOD SATURATION
`MONITORING DEVICE
`
`FIG-8
`
`14
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 14 of 21
`
`US 2007/0271009 Al
`
`INPUT KNOWN FLIGHT
`PARAMETERS
`
`
`
`
`REVISE
`
`KNOWN FLIGHT
`
`PARAMETERS
`
`450
`
`452
`
`(F)
`
`454
`
`456
`
`458
`
`460
`
`462
`
`NO
`
`OUTPUT LIST OF
`CALCULABLE PARAMETERS
`
`INPUT KNOWN SELECTED
`PARAMETERS
`
`CALCULATE SELECTED
`PARAMETERS
`
`OUTPUT CALCULATED
`PARAMETER
`
`
`
`
`
`15
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 15 of 21
`
`US 2007/0271009 Al
`
`FIG-9A
`
`—BAROMETRIC PRESSURE
`—OAT
`—CABIN TEMPERATURE
`—INDICATED ALTITUDE
`—PRESSURE ALTITUDE
`—DENSITY ALTITUDE
`
`—PRESSURE ALTITUDE
`—DENSITY ALTITUDE
`—CABIN DENSITY ALTITUDE
`—ALVEOLAR OXYGEN PRESSURES (PO.) OF:
`INDICATED ALTITUDE
`PRESSURE ALTITUDE
`DENSITY ALTITUDE
`
`520
`
`
`BLOOD MONITOR READING
`
`LEVEL
`
`;DISPLAYSAO,
`
`
`
`
`
`
`
`CABIN DENSITY ALTITUDE
` 030
`
`SA09>
`91%?
`
`ACTIVATE WARNING
`MESSAGE
`
`16
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 16 of 21
`
`US 2007/0271009 Al
`
`INPUT DESIRED FLIGHT PARAMETERS
`
`OUTPUT LIST OF REQUIRED FLIGHT
`PARAMETERS TO CALCULATE DESIRED FLIGHT
`PARAMETERS
`
`INPUT KNOWN PARAMETERS
`
`608
`
`MISSING
`PARA—
`METERS?
`
`YES
`PROMPT FOR MISSING PARAMETERS~~®1¢
`
`NO
`
` 610 ANY
`
`
`
`
`616
`
`624
`
`-|
`
`
`
`DEVICE
`
`SUPPLIES .
`
`MISSING
`
`
`‘PARAMETERS
`
`USER INPUTS PARAMETERS
`
`
`
`
`620
`
`TO FIG-11B
`
`FIG-11A
`
`17
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 17 of 21
`
`US 2007/0271009 Al
`
`FROM FIG-11A
`——.
`
`628
`
`YES
`
`NO
`
`CALCULATE DESIRED FLIGHT PARAMETERS/~
`
`OUTPUT DESIRED FLIGHT PARAMETERS
`
`632
`
`636
`
`640
`
`YES
`
`
`
`
`MODIFY
`ANY
`
`
`
`VALUES?
`
`
`644
`
`)
`
`FIG-11B
`
`18
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 18 of 21
`
`US 2007/0271009 Al
`
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`19
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`

`

`Patent Application Publication Nov. 22,2007 Sheet 19 of 21
`
`US 2007/0271009 Al
`
`SELECT TOTAL NUMBER OF PASSENGERS
`
`-'700
`
`SUBSTITUTE NAMES FOR EACH PASSENGER
`
`703
`
`706
`
`712
`
`
`
`
`
`DOES
`
`
`USER WISH TO
`
`FLIGHT DATA
`
`
`NO
`PROVIDE FLIGHT
`
`
`EXIST FOR
`
`DATA ESTIMATE
`
`PASSENGER
`
`
`
`FOR PASSENGER
`
`
`#9
`#?
`
`
`DEVICE INPUTS
`FLIGHT DATA FOR
`PASSENGER #
`
`
`INPUT PASSENGER
`
`PASSENGER #
`PASSENGER #
`
`
`INPUT PASSENGER
`FLIGHT DATA FOR
`
`FLIGHT DATA FOR
`
`#1o
`
`724
`
`
`
`
`
`ARE THERE
`ADDITIONAL
`PASSENGERS?
`
`
`
`
`721
`
`NO
`
`_
`INPUT NUMBER OF
`LEGS OF FLIGHT
`
`
`
`
`
`
`
`INPUT PARTICULARS
`OF LEGS NUMBER:
`~ALTITUDE
`—DISTANCE
`OR
`—ALTITUDE
`2 LOCATIONS
`
`
`
`
`
`
`
`
`
`
`FIG-13A
`
`727
`
`TO FIG-13B
`
`20
`
`20
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 20 of 21
`
`US 2007/0271009 Al
`
`FIG-13B
`
`FROM FIG-13A4
`
`740
`
`730
`
`YES<<
`
`NO
`
`INPUT AIRCRAFT
`MODEL INFO
`
`73
`
`1
`
`733
`
`
`
`ADD/
`REMOVE
`
`PASSENGERS?
`
`
`
`INDICATE
`
` CALCULATE OXYGEN
`~-ADD/REMOVE
`
`—PASSENGER #
`EACH LEG
`
`
`
`
`REQUIREMENTS FOR
`
`OUTPUT REQUIREMENTS
`—EACH PASSENGER #
`—CUMULATIVE OXYGEN REQ.
`
`
`
`744,
`
`INPUT PASSENGER
`NUMBER
`
`
`
`
`
`748
`
`NO
`
`
`“USER WISH TO
`PROVIDE FLIGHT
`
`_ DATA ESTIMATE
`
`FOR PASSENGER
`DEVICE INPUTS
`
` #?
`PASSENGER #
`FLIGHT DATA FOR
`YES
`
`745
`
`TO FIG-13C
`
`21
`
`21
`
`

`

`Patent Application Publication Nov. 22,2007 Sheet 21 of 21
`
`US 2007/0271009 Al
`
`FROM FIG-—13B
`
`Vol
`
`INPUT FLIGHT DATA
`PASSENGER NUMBER
`
`YES
`
`
`
`
`MODIFY
`ADDITIONAL
`
`
`PASSENGER
`
`
`NUMBERS?
`
` (O04
`
`NO
`
`779
`
`
`
`797
`
`
`MODIFY
`
`LEGS OF
`
`FLIGHT?
`
`
`Ne
`
`INPUT LEG NUMBER
`
`772
`
`DISPLAY CURRENT LEG
`
`NUMBER PARTICULARS
`
`
` MODIFY
`
`
`ALTITUDE
`OR
` 766
`
`DISTANCE/
`LOCATION?
`
`NO
`
`
`
`UPDATE
`YES
`
`FLIGHT
`
`PARAMETERS?
`
`
`ror EACH LEG
`
`
`OUTPUT OXYGEN
`REQUIREMENTS
`
`CALCULATE OXYGEN
`REQUIREMENTS FOR
`EACH LEG
`
`769
`
`NO
`
`FIG-13C
`
`22
`
`22
`
`

`

`US 2007/0271009 Al
`
`Nov. 22, 2007
`
`SYSTEM AND METHOD FOR MONITORING
`PASSENGER OXYGEN SATURATION LEVELS
`AND ESTIMATING OXYGEN USAGE
`REQUIREMENTS
`
`FIELD OF THE INVENTION
`
`[0001] This invention relates to a system for monitoring
`oxygen saturation levels of and estimating oxygen usage
`requirements for aircraft passengers and crew, and more
`particularly, to avoiding hypoxemia in aircraft passengers
`and crew traveling in high performance unpressurized air-
`craft by monitoring oxygen saturation levels of and estimat-
`ing oxygen usage requirements for the passengers and crew.
`
`BACKGROUND OF THE INVENTION
`
`[0002] Ascent to altitude by use of airborne craft was
`initially achieved by hot air balloon. The first passengers
`carried beneath the Mongolfier brothers balloon during a
`1782 flight were a duck, a rooster and a sheep,as the effects
`of flight for a person were unknown. At least one hundred
`years later, the physiological effects due to unpressurized
`high altitude flying remained largely unknown. In 1875, a
`three man balloon crew first employed a supplemental
`oxygen source consisting of three goatskin bags connected
`to a centered wash bottle providing 72 percent oxygen
`totaling 440 liters. The balloon flight reached 28,000 feet in
`altitude. While attempting to conserve oxygen during the
`flight, the three men were overcome by a euphoric torpor
`induced by lack of oxygen, resulting in the deaths of two of
`the men. The survivor later recorded that when convinced of
`
`the need of oxygen, he was powerless to raise his arms,
`unable to raise the mouthpiece of the oxygen containerto his
`lips, and though within easy reach, the oxygen which would
`have saved the lives of his companions went unused. An
`insufficiency of oxygen in the blood is defined as hypox-
`emia, while an insufficiency of oxygen in the bodytissue is
`defined as hypoxia.
`
`[0003] To address the adverse effects of in-flight oxygen
`deficiency, oxygen distribution systems were incorporated
`into aircraft. Pre-World WarII pipe stem oxygen distribution
`systemswerelater replaced by pressure clearance systemsat
`the end of the conflict. Soon after, constant flow masks were
`made available in general aviation. While initial commercial
`air transport in the United States in the 1930’s did notraise
`a significant risk of hypoxia because of low flight altitudes,
`by the 1940’s to 1960’s, the service ceiling of commercial
`aircraft was at 40,000.
`
`[0004] Each person has a different oxygen requirement
`and adaptation to altitude, and those requirements change on
`a daily, or more accurately, an hourly basis based upon
`fatigue, diet, hydration level, stress and other personal
`factors. Increasesin altitude likewise increase the associated
`
`adverse effects, including changesin visual acuity, psycho-
`motor performance and situational awareness. As altitudes
`increase above 10,000 feet and critically above 15,000 feet,
`the time of useful consciousness (TUC) decreases at 15,000
`feet to 15-20 minutes. As expected, there is a difference in
`the physical fitness standards between commercial/military
`pilots and general aviation pilots and passengers.
`
`[0005] The Federal Aviation Administration (FAA), mind-
`ful of the adverse effects to passengers and crew ofaircraft
`operating at altitude, has developed regulations concerning
`
`the availability and use of sustenance and supplemental
`breathing oxygen. These regulations are divided into the
`following classifications: air transport, on-demand opera-
`tions and general aviation. The regulations relating to gen-
`eral aviation are discussed herein. The term “passengers” or
`“occupants” as used herein may also include the pilot and
`crew ofthe aircraft. The term “subject” as used herein may
`refer to any person in theaircraft. The current regulations are
`based on rules initially established by empirical data and
`experience of the Civil Aviation Administration (CAA).
`
`[0006] Requirements for general aviation supplemental
`oxygen is provided in 14 CFR 91.211 as cited in the Federal
`Register dated Aug. 23, 2001. While this regulation provides
`for aircraft having pressurized and unpressurized cabins,
`most of the single engine piston powered general aviation
`aircraft used underPart 91 of the regulations employ unpres-
`surized cabins, which is the primary focus herein. 14 CFR
`91.211 provides that supplemental oxygen shall be provided
`to a required minimum flight crew above cabin pressure
`altitudes of 12,500 feet, mean sea level (MSL), up to and
`including 14,000 feet MSL if the durationoftheflight at that
`altitude is more than 30 minutes. Cabin pressure altitude is
`calculated by taking a pressure measurement
`inside the
`aircraft cabin and converting that pressure to an altitude,
`preferably by a device that performs this calculation auto-
`matically. At cabin pressure altitudes above 14,000 feet
`MSL,the required flight crew must be provided with and use
`supplemental oxygen. MSLaltitude is the atmospheric pres-
`sure either directly measured by weather stations at sea level
`or empirically determined from the weatherstation pressure
`and temperature readings collected by weather stations not
`at sea level. At cabin pressure altitudes above 15,000 feet
`MSL,supplemental oxygen must be provided to each occu-
`pant of the aircraft. In other words, FAA regulations do not
`require providing supplemental oxygen to occupants (pas-
`senger that are not required flight crew) below 15,000 feet
`MSL.
`
`It is noted that other FAA regulations underTitle
`[0007]
`14, such as Parts 121 and 135, relate to air transport and
`on-demand operations, which specify different, more strin-
`gent altitude requirements with respect
`to supplemental
`oxygenusefor pilots. In other words, the altitudes triggering
`the requirements for supplemental oxygen are greater for
`general aviation use. For example, 14 CFR 135.89 provides
`that the minimum altitude is 10,000 feet MSL instead of
`12,500 feet MSLforthepilotor flight crew. The time for the
`required crew to use supplemental oxygen is the same 30
`minute duration. As a result, many pilots may be lulled into
`believing that the time they spend at higher altitude is of
`little concern and to “push the envelope,” accepting higher
`altitudes when filing flight plans or maximizing the opera-
`tional capabilities of their turbocharged piston powered
`engines without the use of supplemental oxygen. This mis-
`guided thinking has often concluded tragically. Flying at
`altitudes as low as 5,000 feet can affect certain individuals,
`particularly at night. It is estimated that pilot error is the
`primary cause of about 74 percent of all general aviation
`accidents. To understand how the present invention utilizes
`generally accepted clinical standards for hypoxemia, which
`can be easily and reliably determined and applied to help
`prevent hypoxia, a brief summary of human oxygen physi-
`ology is provided below.
`
`23
`
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`

`US 2007/0271009 Al
`
`Nov. 22, 2007
`
`[0008] Oxygen that is inspired through the mouth or nose
`proceeds down the trachea and into the main bronchi,
`flowing out into primary and secondary bronchi and then
`into the alveolar air units. The space between the mouth and
`the alveolar units is “dead space” because there is no air
`exchange in these tubes. In other words, that portion of air
`previously inspired only reaching this dead spaceretains its
`oxygen content and may again be inspired for air exchange.
`Oxygen and carbon dioxide exchanged in the alveolus is
`dependent on the diffusion capacity, which can be affected
`by age and chronic disease.
`[0009] Ventilation and oxygen supplied for aerobic cellu-
`lar respiration, is accomplished in the alveolar units which
`diffuses oxygen across the pulmonary membrane into cap-
`illary beds, the diffused oxygen in the alveolar units passing
`through the pulmonary cells into the pulmonary venules then
`into the pulmonary vein. Pressurized carbon dioxide (PCO,)
`from the body flows from the pulmonary artery into the
`capillaries,
`then to the alveolar unit, where it similarly
`diffuses through the pulmonary membraneandis expired as
`a waste gas. The volume of air moved through the pulmo-
`nary units is known as minute ventilation with vital capacity
`being the total volume of the lung.
`[0010] The actual air that we breathe is a combination of
`different gases at various pressures P. The pressure of
`oxygen (PO,) is 159.1 torr in dry air, 149.2 torr in moist
`tracheal air at 37° C., 104 torr in the alveolar gas unit, 100
`torr in arterial blood and 40 torr in mixed venous blood out
`
`of a total 760 torr at standard conditions. Thus, PO, as used
`herein may be defined to refer to the oxygen pressure level
`corresponding to ambient, trachealor alveolar as appropriate
`to apply or calculate other physiologic parameters. In addi-
`tion to PO,, the partial pressures of CO, and H,O and N,are
`necessary to calculate the total and partial pressures of gases
`acting on the pilot (FIG. 5). The term torr refers to the
`pressure required to support a column of mercury 1 mm high
`under standard conditions, that is, standard density of mer-
`cury and standard acceleration of gravity. These conditions
`are at 0° C. and 45° latitude with acceleration of gravity is
`980.6 cm/sec”, torr is a synonym for “mm/Hg”. An impor-
`tant constant to remember is the partial pressure of water
`vapor, for the trachea will always have a PH,O of47 torr as
`inspired air will be saturated with water vapor as soon asit
`is inspired. Therefore only 760 torr—47 torr or 713 torr of
`pressure is available for the sum of pressures of oxygen,
`carbon dioxide and nitrogen at standard conditions of 0° C.
`and 45° latitude. Water vapor pressures increase with tem-
`perature, for example 20° C. has PH,O of 17.5 torr while 37°
`C. has PH,O of47 torr. The PO, of moist inspired air in the
`trachea is actually 149 torr, which is 20.93% of 713 torr.
`While the trachea will always have a PH,O of 47 torr, what
`of the environment from whichthe inspired gases are drawn
`into the airway of the pilot of an unpressurized aircraft at
`10,000 feet MSL? Astheaircraft climbs, the partial pressure
`of O, and the temperature will fall with increasing altitude.
`Althoughair vents of the aircraft cabin are open to the cooler
`outside environment at
`increased altitude,
`typically the
`aircraft cabin air that is inspired bythe aircraft passengers is
`heated and maintained at an elevated temperature for pas-
`senger comfort. Concomitantly, the ground barometric pres-
`sure and temperature will change as the aircraft navigates a
`course. These changes alter the baseline assumptions in
`actualpartial pressure of gasesat the indicated altitudes (IA)
`of the aircraft. In a pressurized aircraft such as a commercial
`
`transport aircraft pressurized at 4,000-8,000 feet MSL, a
`constant cabin temperature and a cabin pressure can be
`maintained. Over the time of a cross-country flight with
`decreased cabin pressure, the pilot and passenger(s) will
`notice lower extremity edema from lower cabin pressure
`relative to sea level.
`
`[0011] For purposes herein, the pilot lung alveolar gas
`compartmentis a critical volume. During respiration pilots
`expire CO, and absorb O, gases. The quantity (CO, ml
`excreted/ml O, absorbed) is the respiratory ratio R which
`gives a mean estimate of PO, and PCO,over time. The mean
`alveolar O, (PAO,) at sea level and 37° C., is defined in
`equation 1
`
`PAO) = FIO2(713) — PACO>| FIO) +
`
`
`1-FIO,
`
`where FIO, is the fraction of inspired O, (percent), and
`PACO,
`is the mean alveolar CO,. Recall
`that
`the total
`pressure of all alveolar gases at sea level is 760 torr. Pilot
`lung volumesandactual cabin altitudes will be discussed in
`additional detail below. As the altitude increases, the FIO,
`remains relatively constant at 21%, the PAO, decreases as
`the barometric pressure decreases with altitude (at 18,000
`feet MSL; 50% of atmospheric pressure at sea level
`is
`absent). Therefore, the partial pressures of all gases decrease
`with increasing altitude. As hypoxemiais defined as the lack
`of adequate oxygen supply in the blood, individual pilot
`hypoxemia can occurat an altitude where the oxygen supply
`for the individual pilot is inadequate forthe pilot physiologic
`oxygen demand. The key factor is not a specific aircraft
`altitude MSL but rather the oxygen demandofthe pilot. The
`diffusion capacity of the gases varies with the individual,
`dependent on the current status of the health of the pilot’s
`lung alveolus. The oxygen diffuses from the alveolus to the
`venuecapillary into the blood serum andthen is absorbed by
`the red cell and stored there for transport in the body.
`
`[0012] The componentsof the oxygen transport system are
`comprised of cardiac output of the heart (CO), the hemo-
`globin concentration of the blood (Hb), oxygen red cell
`saturation of the red blood cells (SAO,) for arterial circu-
`lation, (SVO,) for venous circulation, and the oxygen con-
`sumption of the body (VO,,). Oxygen saturation is defined as
`the percentage of oxygen bound hemoglobin to the total
`amount of hemoglobin available. Oxygen saturation in the
`blood may be measured by a co-oximeter in the pulmonary
`laboratory.
`
`Invasive medical oxygen moniters or oximeters,
`[0013]
`such as those originally manufactured by Oximetrix Inc., of
`Mountain View, Calif., may include a catheter, an optical
`module and a digital processor. The catheter, such as a
`pulmonary artery catheter typically includes a balloon on a
`distal tip for flow-directed placement, and a proximal lumen,
`whichis a thermistor similar to a standard pulmonary artery
`thermodilution catheter, and two optical fibers. One fiber
`transmitslight from the optical moduleto the distal tip of the
`catheter while the second fiber returns the reflected light
`from the distal tip back to the optical module. The Oximetrix
`optical module contains three light emitting diodes (LED’s)
`that illuminate, via one optical fiber, the blood flowing past
`the catheter tip. Light reflected from the blood is returned
`
`24
`
`24
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`

`US 2007/0271009 Al
`
`Nov. 22, 2007
`
`through the second fiber and directed into a solid state
`photodiode detector within the optical module. The module
`converts the light intensity levels into electrical signals for
`transmission to the processor. The digital processor com-
`putes percent of oxygen saturation values based on the
`electrical signals transmitted and received from the optical
`module. These values are continuously displayed in numeri-
`cal form by LED and are recordedbythe processor’s built-in
`strip recorder. Later models have LED display only but
`functionally are the same unit.
`
`hemostasis with normal hemoglobin cardiac output, and
`adequate oxygenation there should be sufficient oxygen
`content in the blood and this content will be transported to
`peripheral
`tissues for consumption. Provided below are
`some equations relating to the oxygen transport system.
`
`Equations of the Oxygen Transport System
`
`(0017]
`
`1.
`
`Oxygen Saturation (%)
`[0014] Oximeters have been used under clinical condi-
`tions, especially for monitoring oxygen saturation levels of
`HBO,
`SQ) = ——2
`«100
`critically ill patients. However, catheters, such as Opticath®
`?~Hb + HBO}
`catheters which are used with Oximetrix oxygen monitors,
`are invasive as the catheter must be inserted inside the
`
`pulmonary artery. Alternately, oxygen saturation may also
`be measured transcutaneously using infrared light in pulse
`oximetry units. Pulse oximeters similarly employ an LED
`and photosensor placed on opposite sides of arterioles
`located in a subject’s tissue that can be transilluminated. In
`other words, pulse oximeters may be positioned over a
`narrow portion of a subject’s anatomy, such asa finger or ear
`lobe. Typically,
`the pulse oximeter “clips” over opposed
`sides of the end of an appendage, such as an index finger.
`Pulse oximeters have many advantages over Opticath®
`catheters. They are noninvasive, as the subject’s skin is not
`pierced, require no calibration, provide nearly instantaneous
`readings, rarely provide false negative information, require
`no routine maintenance, and are relatively inexpensive to
`purchase. These units are accurate in normal physiologic
`states, although in clinical situations of hypoprofusion and
`hypothermia the transcutaneous oxygen saturation measure-
`ments are inaccurate. Oxygen saturation measured in a
`pulmonary artery by either direct blood measurement (blood
`gas studies) or fiber-optic pulmonary artery catheter (co-
`oximetry) or pulse oximetry is generally accurate within 2%
`of the actual value.
`
`[0018] Arterial (SAO,) 91%-97%
`
`[0019] Venous (SVO,) 60%-75%
`
`2. Oxygen Content (CO,) (mL O,/100 mL blood=
`[0020]
`vol %)arterial (2% O,, dissolve)+(98%/O, Hb saturated)
`
`[0021] Arterial
`
`[0022] CAO,=(PO,x0.0031)+(Hbx1.38xSAO,)
`
`[0023] CAO,=(100 torrx0.0031)+(15 9x1.38x0.97)
`
`[0024] CAO,=0.3420.1
`
`[0025] CAO,=20.4 vol. %
`
`[0026] Venous
`
`[0027] CVO,=(PVO,x0.0031)+(Hbx1.38xSVO,)
`
`[0028] CVO,=(40 torrx0.0031)+(15 2x1.38x0.75)
`
`[0029] CVO,=0.12+15.52
`
`[0030] CVO,=15.64 vol. %
`
`[0031]
`
`3. Oxygen Transport (O,T)(mL O./min)
`
`[0032] Arterial: O,TA=COxCAO,x10
`
`[0033] Venous: O,TV=CVO,x10
`
`[0034]
`
`4. Oxygen Consumption (VO,)(mL O,/min)
`
`[0035] VO,=COxHbx1.38 (SAO,-SVO,)x10
`
`[0036] VO,=5 L/minx15 gx1.38 (0.97-0.75)x10
`
`[0037] VO,=228 mL/min
`
`[0038]
`
`5. Cardiac Output (L/min)
`
`[0015] Co-oximetry and pulse oximetry provide measure-
`ments of hemoglobin saturation. Molecular oxygen is car-
`ried within the hemoglobin molecule to tissues in the body,
`the oxygen carrying capacity possibly varying over time in
`response to changing health and/or environmental condi-
`tions. Normal hemoglobin carries 98% of the oxygen within
`the hemoglobin molecule with approximately 2% of the
`oxygen in the blood serum. This, however, can change
`significantly in diseases
`such as_
`sickle-cell
`anemia
`(AbSS>50%) in which there is abnormal sickling of the
`hemoglobin molecule and decrease in oxygen carrying capa-
`bility. This can be aggravated in periods of hypotension and
`dehydration even in sickle cell trait (HbSS<50%). Oxygen
`cos—2
`~ CAO, — CVO;
`transport
`(OT) occurs best at hemoglobin values of
`40-43%. At hematocrit values greater than 50%, the result is
`increased viscosity and sluggishness of the blood, whereas
`hematocrit values less than 40% havethe result of decreased
`hemoglobin and therefore less molecular oxygen saturation,
`a result of anemia. Oxygen contentrelates to the ability of
`the subject to adjust to physiologic stress.
`
`[0016] The driving force in the oxygen transport system is
`the heart and resultant cardiac output (CO). The cardiac
`output is typically about 5.0 liters per minute, with maxi-
`mums up to about 15.0 liters per minute during exercise.
`However, cardiac output can drastically fall to about 1.0 or
`2.0 liters per minute in states of heart failure. In normal
`
`PVO, =
`PO, =
`P50 =
`
`Hb =
`Het =
`ODC =
`
`25
`
`List of Abbreviations
`
`mixed venous oxygen mm Hg (31-40) (torr)
`arterial oxygen tension mm Hg (60-100) (torr)
`partial pressure mm Hg of oxygen at 50% saturation of
`hemoglobin molecule (26.6 torr)
`hemoglobin (g/dL)
`hematocrit (%)
`oxygen dissociation curve
`
`25
`
`

`

`US 2007/0271009 Al
`
`Nov. 22, 2007
`
`-continued
`
`List of Abbreviations
`
`CVO,=
`CAO, =
`VO=
`Ccl=
`CO=
`SAO, =
`SVO, =
`SO, =
`OjTA =
`O,TV =
`0.0031 =
`1.38 =
`10 =
`
`venous oxygen content mL O,/100 mL blood
`arterial oxygen content mL O,/100 mL blood
`oxygen consumption
`cardiac index (1/min/SA)
`cardiac output (1/min)
`arterial oxygen saturation (91-97) (%)
`mixed venous oxygen saturation (60-75) (%)
`oxygen saturation
`oxygen transport (arterial)
`oxygen transport (venous)
`diffusing capacity coefficent of plasma O
`mL of O, per gram of hemoglobin
`conversion factor to mL/100 mL blood
`
`[0039] Oxygen saturation is determined by the biochem-
`istry of the red blood cell, factors such as 2-3-DPG,redcell
`pH and temperature, and actual hemoglobin values can be
`plotted in oxygen pressure torr versus oxygen saturation
`with a hemoglobin saturation curve, also referred as the
`oxygen disassociation curve (ODC), also referred as the
`hemoglobin disassociation curve, as illustrated in FIG. 1.
`P-50 is defined as 26.6 torr at 50% oxygen saturation. The
`ODC is affected by temperature, pH, hemoglobin value,
`2-3-DPG, and ambient
`temperature and pressure (ATP)
`levels. These factors all affect erythrocytic functions and
`compensate for variation in body homostasis. In hyperven-
`tilation, the increased flow of oxygenresults in acidic blood
`serum levels (lower pH), higher body temperature and
`higher 2-3-DPG environments. Corresponding oxygen
`unloading results in alkaline blood serum levels (higher pH),
`lower body temperature, and lower 2-3-DPG levels. A
`decrease in hemoglobin would decrease the overall ODC
`curve.In essence, the respiratory function of the hemoglobin
`molecule is similar to the respiratory function of the lung.
`On the ODC curve the oxygen saturation value is between
`about 91% and about 97%, corresponding to oxygen torr
`between about 60% and 100%. While there is a wide
`gradient of torr,
`there is a small difference in oxygen
`saturation in oxygen returning to the heart, venous SVO,.
`Referring to FIG. 1, normal SVO, values of 60-75% satu-
`ration correspondto a range of 31-40 torr. The mixed venous
`oxygen saturation of blood at the right atrium in the heart
`would not be measuredin flight, however, oxygen saturation
`by pulse oximetry can easily be measured in flight.
`
`[0040] The P50, the value of serum PO,torr at 50% Hb
`saturation can be affected by temperature, as defined by
`equation 2
`P507=26.6x 106-473T=temp ° C. Pilot [2]
`
`or by acid base balance in terms of pH, as defined by
`equation 3
`
`P50py = 26.6 x 10048 (PH-74)
`where
`
`H=6.10+L
`pee
`
`LHCO;]
`276.030 / PCOa]
`
`[3]
`
`and these values will shift the hemoglobular disassociation
`curve (ODC)right (higher temperature or lower pH)orleft
`
`26
`
`(lower temperature and higher pH). A left shifted curve
`increases P50 and O,saturation.
`
`[0041] The ODCcanbecalculated by the Aberman tech-
`nique provided in equation 4 where:
`
`f=7
`ODC 0;Sat = » Ky, + 1 (PO, —27.5)/(PO2 + 27.5)!
`f=0
`
`and estimates of oxygen need can be calculated with mea-
`sured SAO, and expired CO, (EC