Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Reexamination Certificate
1999-03-08
2001-06-19
Nguyen, Dinh X. (Department: 3738)
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
C128S205240, C128S204180, C600S021000
Reexamination Certificate
active
06247472
ABSTRACT:
BACKGROUND OF THE INVENTION
Several underlying principles are key to an understanding of the present invention.
It is theoretically possible to pump a volume of fluid such as ambient air into a chamber containing fluid at a second pressure such as a compressed gas chamber with the investment of a certain amount of work which work will be exactly equal to the amount of work which is produced by taking the same volume of fluid and reversing the process, that is, expanding that same quantity of gas from the second pressure to the first pressure.
As is known from thermodynamics, adding heat to the gas such as while it is in the pressurized chamber will produce an increment of increased work during the expansion with the amount of work produced during the expansion being a function of the amount of heat added, the pressure ratio, etc. The difference between the expansion work and the compression work may be used to overcome friction and provide a net work output if desired (expansion work less compression work less friction work). The friction work is the friction force times the distance moved by a mass experiencing that friction force.
From thermodynamics, greater compression ratios and greater heating of the compressed gas lead to better engines measured with respect to work output per unit fuel used, work output per unit weight, work output per unit volume occupied by the engine, etc. Thus, there has been no motivation to make a collapsible engine and more particularly, an engine wherein the heater for the compressed gas comprises a large flaccid walled airtight container.
Rolling diaphragm pumps and expansion motors can be almost frictionless with the friction on the order of 1% of the energy needed to compress a quantity of gas.
The embodiments disclosed herein which are heat engines are most closely related to the Brayton cycle which is more commonly embodied as a gas turbine engine.
The maintenance of life requires certain supplies and conditions such as oxygen, water, food and an acceptable environmental temperature. As is obvious, such supplies and conditions need not be available except locally such as oxygen in air provided to a SCUBA diver for respiration through his mouthpiece or a suitable temperature maintained next to his skin such as may be obtained by the use of a “wet suit”.
Mountain climbers climb mountains which are far from sources of resupply so that they must carry supplies with them, such supplies including food, fuel and, during high altitude climbs, bottled oxygen.
The following table suggests the atmospheric pressures (PSIA-lbf/in
2
Absolute) and water boiling points (temperatures) which might be expected at various altitudes:
Pressure
Altitude
Water
Pressure
Altitude
Water
(PSIA)
(ft)
B.P. (° F.)
(PSIA)
(ft)
B.P. (° F.)
4.5
29,000
157.8
5.0
26,421
162.2
5.5
24,085
166.3
6.0
21,951
170.1
6.5
19,989
173.6
7.0
18,173
176.9
7.5
16,481
179.9
8.0
14,898
182.9
8.5
13,412
185.6
9.0
12,012
188.3
9.5
10,686
190.9
10.0
9,428
193.2
10.5
8,232
195.2
11.0
7,092
11.5
6,001
12.0
4,598
12.5
3,958
13.5
2,071
(Note that daily weather conditions will provide some variation of these values.)
Respiration at High Altitude
With respect to respiration, the low pressure effects of living at high altitudes slow the thought processes, make a person more susceptible to frostbite, make sleep more difficult or impossible, interfere with digestion, bring on dehydration, headaches, fluid accumulation in the lungs, etc. These effects among others are collectively identified as being symptoms of “mountain sickness”.
Mountain sickness is a danger to persons living at high altitudes and can incapacitate or kill a person. Rarely, death can occur at altitudes as low as 5,000 feet above sea level. However, placing a person suffering from mountain sickness under increased air pressure for only a few hours will typically bring complete recovery.
Bottled oxygen is commonly used by mountain climbers climbing the higher peaks to increase the partial pressure of oxygen to counter the debilitation associated with high altitude and the ambient low partial pressure of oxygen but the bottle and oxygen represent heavy consumables. The gradual decline in physical ability which generally occurs as oxygen supplies are husbanded may tempt mountain climbers to make a precipitous “dash” for the peak before the bottled oxygen and physical reserves of strength and health are depleted even if conditions such as weather are marginal.
Portable hyperbaric apparatus has been available for several years for use by mountain climbers. Typically, the apparatus comprises a foot operated compressor and a flexible walled collapsible bag having a sealable opening through which a person may enter the bag. In use, a person suffering from mountain sickness enters the bag, the opening is sealed and a second mountain climber on the outside of the bag then operates the compressor whereby air is forced into the bag thereby introducing pressurized air into the bag which air is available for respiration by the bag's occupant. The pumped air inflates the bag and provides fresh air under pressure in the bag.
These bags are typically pressurized to 2 PSI above ambient. In these known portable hyperbaric bags or chambers which are now being used by mountain climbers, a pressure relief valve is used to vent air to the atmosphere. The work required to pressurize a bag is significant and stresses the climber who is manning the compressor. Thus, this apparatus is used only when a climber is ill and the apparatus is otherwise a dead weight for the mountain climbers to carry up and down a mountain. However, it is a needed dead weight since it may be absolutely necessary in an emergency.
Patents demonstrating the known prior art relating to portable hyperbaric apparatus such as is used by mountain climbers include: U.S. Pat. No. 4,974,829 to Gamow et al and U.S. Pat. No. 5,109,837 to Gamow.
The above table shows that a person in a portable hyperbaric pressure chamber at 29,000 ft altitude at 2 PSIA above ambient pressure would experience a pressure as if he were exposed to the ambient pressure at just under 20,000 ft. At about 24,100 ft in a chamber at 2 PSIA above ambient, a person would be at a pressure equivalent to the ambient pressure at about 16,500 ft altitude. A person at about 22,000 ft altitude would experience a pressure roughly equal to 14,300 ft which is about equal to the altitude of the base camp used for most climbs on Mt. Everest.
It would be desirable to allow a mountain climber to rest and/or sleep in a pressurized space using little or no effort on the part of the mountain climber or his fellows.
It would thus become possible to wait out a storm at relatively little and possibly no cost in bottled oxygen while maintaining physical strength and reserves. Mountain climbing would become safer since a dash for the top could be delayed until conditions are optimal. This delay would cost only time and only a slight decline in physical strength, health and supplies. Indeed, the physical strength and health of a climber could actually increase through rest during such a delay under many conditions.
Cooking under Pressurized Air
During mountain climbs, water is typically available from ice and snow on the mountain but must be melted at a cost in the fuel used to heat and melt the snow and/or ice. Hot prepared food is both nutritious and provides warmth and psychological benefits.
The fuel needed for a fire is often unavailable from the environment at higher altitudes such as above the “tree line”, and must be carried by the climber. Low ambient pressure and temperature both increase the amount of time and fuel needed for cooking since the boiling temperature of water (which sets the maximum temperature for many cooking processes) decreases with decreased ambient pressure as indicated in the above table.
Pressure cookers are known in art. In using such cookers, food and water is placed in the cooker which is then sealed and heated until the water is boiling whereupon the superatmosphe
LandOfFree
Method and apparatus for using readily available heat to... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for using readily available heat to..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for using readily available heat to... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2475191