STEM

THE SCIENCE OF THEHYPERBARIC CHAMBER

 Brief history of the Hyperbaric Chamber in the Cayman Islands

After fundraising and generous donations by Cayman businesses, a reconditioned

hyperbaric chamber was bought in the U.S. and placed in a hut behind Cayman Clinic in

1972. It was run by the British Sub-aqua Club. It is now in a room at the Hospital near the

Forensic Science lab and the Morgue.

 THE HYPERBARIC CHAMBERA few years ago

 THE HYPERBARIC CHAMBERFrom Right

 THE HYPERBARIC CHAMBERFrom Left

 THE HYPERBARIC CHAMBER

 THE HYPERBARIC CHAMBERLooking Inside

 THE HYPERBARIC CHAMBERInside looking Out

Dive Physics THE GAS LAWS

Most Important to the Hyperbaric Chamber

Boyle’s LawBoyle’s Law

Dalton’s Law of Partial PressureDalton’s Law of Partial Pressure

Henry’s LawHenry’s Law

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THE GAS LAWS - Pressure

Pressure = force per unit area

The Gas Laws refer to absolute pressure (Pabs). We are subject to a pressure at the surface because of the weight of 10 miles of air above us. The pressure at the surface is l atmosphere (l atm).A pressure gauge is made to read zero at the surface despite the weight of the atmosphere, and therefore reads pressure extra to the already existing atmospheric pressure. Each 33ft, or 10 meters of water, exert the same pressure as atmospheric air at sea level.

(Continued on next slide)

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THE GAS LAWS - Pressurecontinued

Absolute pressure refers to Gauge pressure +1 atm. ie the total pressure including atmospheric

Examplethe gauge pressure 99 ft below the surface of the sea is 3 atm due to the weight of the water. However the absolute pressure is 4 atm, due to the combined effect of the water plus the weight of the atmosphere pressing down on the surface of the water. Pabs = Pg+ 1 atm

THE GAS LAWS – PressureCompressor Room and Pressure Tanks

THE GAS LAWS – Pressure Gauge on Chamber

Pressure Units

1 atmosphere (atm) at sea level is (approximately) = 1 kg per square cm (1 kg/cm2) (1 bar) = 14.7 pounds per square inch (p.s.i.) = 760mm of mercury (torr) = 29.92in Hg = 101,300 (Newtons per square meter) (pascals) (Pa) = 33ft of sea water

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Boyles Law: -The volume of a fixed mass of gas at a constant temperature varies inversely as the (absolute) pressure. P x V = Constant (As the pressure goes up the volume

goes down & vice-versa.)

P1 x Vl = P2 x V2

If a diver fills his lungs and then holds his breath while he ascends, the volume of his lungs will expand until either he decides to breathe out or the lungs rupture (embolism).

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DepthDepth PressurePressure

0’0’

Gas VolumeGas Volume

1 atm1 atm FullFull

33’33’ 2 atm2 atm ½ full½ full

66’66’ 3 atm3 atm 11//33 full full

99’99’ 4 atm4 atm ¼ full¼ full

132’132’ 5 atm5 atm 11//55 full full

QUESTIONA diver ascends from 132 ft to 99ft while holding his breath.

If his lungs contained 4 litres of air at 132ft, what is the volume at 99ft?

P2xV2 = P1xV1 (Boyles Law)V2= P1xV1 / P2 = 5atm ab x 4/ 4atm abs= 5 litres

A trainee diver at 33ft shoots to the surface while holding his breath. If his lungs held 4 litres at 33 ft what is the volume at

the surface.P2xV2=P1xV1

V2=P1xV1 / P2 = 2atm x 4 / 1atm = 8 litres.Both divers ascended 33ft, which one is most likely to suffer

an embolism?

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DALTONS LAW. Dalton’s Law is a concept that states that the total pressure exerted by a mixture of gases is the sum of

the partial pressures that each gas would exert if it alone filled the container.

Air at the surface contains 21% oxygen and 79% nitrogen (Including the 1% of other gases with the nitrogen).

air at the surface(1atm) = ppO2 0.21 atm +ppN2 0.79 atmair at 33 fsw(2atm) = ppO2 0.42 atm + ppN2 l.58 atm

The importance of Daltons Law to divers and the Chamber is that the beneficial/toxic effect of gases is dependent on their

partial pressures, not the total pressure of the gas mixture that contains them.

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HENRY’S LAWHenry’s Law of solubility states that the amount of gas

absorbed by a particular liquid is proportional to the partial pressure of the gas .

E.g. If you triple the absolute pressure then the amount of gas absorbed by the liquid will be tripled. ppN in air at a

pressure of 66ft of seawater = 3 x .79=2.37 atmTherefore the divers blood would eventually contain three times the amount of nitrogen at sixty six feet than it does

at the surface.

 HYPERBARIC OXYGEN TREATMENTS

Dive relatedArterial Gas EmbolismDecompression Sickness

Other TreatmentsWound HealingRestoration of Circulation (Advanced

Diabetes) Skin GraftsCarbon Monoxide Poisoning

 HYPERBARIC OXYGEN TREATMENTS

1. Arterial Gas EmbolismCaused by over-expansion of alveolar tissue resulting from gas trapped in the lung expanding on ascent and subsequent entry of gas bubbles into the bloodstream.

 HYPERBARIC OXYGEN TREATMENTS

2. Decompression SicknessCaused by rapid reduction of environmental pressure resulting in Nitrogen (previously dissolved in the body tissues) being released as bubbles in the blood stream.

 TYPES OF DECOMPRESSION SICKNESS

Type I DCSJoint pain and skin bends only. Caused by the physical effects of he bubbles and immune reaction on the tissues.

 TYPES OF DECOMPRESSION SICKNESS

Type II DCSTypically due to bubbles in the nerve tissue of the spinal cord or brain, causing a wide range of neurological problems.

 TYPES OF DECOMPRESSION SICKNESS

The ChokesNitrogen bubble froth in the blood in right side of heart and/or in the lungs. The heart compresses the bubbles rather than pumping the blood. Bubbles in the alveoli capillaries prevent gas exchange and result in extreme shortness of breath.

BENEFITS OF  HIGH ppO2

Normally people at sea level breatheNormally people at sea level breatheoxygen at a partial pressure of 0.21atmoxygen at a partial pressure of 0.21atm

In the hyperbaric chamber at 60ft the patient isIn the hyperbaric chamber at 60ft the patient isbreathing pure oxygen at a pressure of almost 3 atmbreathing pure oxygen at a pressure of almost 3 atm

Next 2 slides – places where higherNext 2 slides – places where higherthan normal ppO2 is availablethan normal ppO2 is available

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To Combat Pressure reduction in Aircraft at AltitudeTo Combat Pressure reduction in Aircraft at AltitudePassengers breathe pure oxygen in order to remain consciousPassengers breathe pure oxygen in order to remain conscious

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To Reduce Chance of Decompression SicknessTo Reduce Chance of Decompression SicknessDivers can breathe nitrox,Divers can breathe nitrox,

a mixture of 32% Oxygen and 68% Nitrogena mixture of 32% Oxygen and 68% Nitrogen

HYPERBARIC OXYGENPure Oxygen is used as well as pressure in hyperbaric treatments.

1. It reduces the amount of nitrogen taken into the lungs during breathing to zero, thus speeding up the release of dissolved nitrogen from the blood into the lungs.

HYPERBARIC OXYGEN

2. The high partial pressure of oxygen in the lungs means there is far more oxygen dissolved in the blood plasma than usual. Despite the patient’s reduced circulation this allows more oxygen to reach the tissues and so promotes healing and reduces swelling.

OXYGEN CYLINDERS

OXYGEN MASKS

PROBLEMS WITH  HIGH ppO2

1. Breathing a high ppO1. Breathing a high ppO22 for an extended for an extended

period can lead to Oxygen Toxicity – this affects theperiod can lead to Oxygen Toxicity – this affects the brain and causes a convulsion similar to an epilectic fit.brain and causes a convulsion similar to an epilectic fit. In the chamber the patient is on pure oxygen for 20 minuteIn the chamber the patient is on pure oxygen for 20 minute periods followed by a 5 minute air break.periods followed by a 5 minute air break.

Next slide – Table 6 – Decompression Sickness showing airNext slide – Table 6 – Decompression Sickness showing air breaksbreaks

CLOCKS – INNER LOCK

CLOCKS – OUTER LOCK

OTHERCYLINDERS

PROBLEMS WITH  HIGH ppO2

2. The high ppO2. The high ppO22 in the chamber is a serious fire hazard. in the chamber is a serious fire hazard.

Oxygen sometimes leaks from patients mask, increasingOxygen sometimes leaks from patients mask, increasing % O% O22 in Inner Lock in Inner Lock

Flammable materials, including paper, avoided.Flammable materials, including paper, avoided. No equipment or material that could cause a spark isNo equipment or material that could cause a spark is allowed inside. The air supplied to chamber is very dryallowed inside. The air supplied to chamber is very dry so increases the risk of sparks from static electricity.so increases the risk of sparks from static electricity. Chamber has “fire wands” and a high pressure sprinklerChamber has “fire wands” and a high pressure sprinkler system.system. There is an oxygen analyzer on the exhaust air, set toThere is an oxygen analyzer on the exhaust air, set to alarm when the oxygen level reaches 24%.alarm when the oxygen level reaches 24%.

Next slides – fire wands. Oxygen analyzerNext slides – fire wands. Oxygen analyzer

FIRE WANDFIRE WAND

OXYGEN ANALYZEROXYGEN ANALYZER

BANNED ITEMSBANNED ITEMS

LIGHTS ARE EXTERNALLIGHTS ARE EXTERNAL

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QUESTIONS?QUESTIONS?

THE ENDTHE END

INTERESTED IN BEING INTERESTED IN BEING ONON

THE CHAMBER TEAM?THE CHAMBER TEAM?

Call John ElliotCall John Elliot91611989161198

Or Ann ElliottOr Ann Elliott91619579161957

To find out when the nextTo find out when the nexttraining course will be training course will be

offeredoffered

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Diving physics questions

1) A gauge reads a pressure of 3 atmospheres. What is the actual pressure? ……………………2) Why must you never hold your breath as you ascend in the chamber? ______________________ 3) A balloon is blown up in the chamber. What will happen to the size of this balloon when you ascend? _________________________________________4) What will happen to the volume of the liquid in a drinking water bottle during ascent?

The General Gas LawA combination of Boyles Law and Charles Law leads

to the General Gas Law: P1 xVl = P2xV2 = a constant

T1 T2If you heat a fixed volume of gas the pressure will go

up. If you leave a dive tank already filled to a high pressure out in the sun, then the pressure will rise

until...If you reduce the volume, and try to keep the temperature constant, the pressure will go up.

WHENEVER YOU USE THE GAS,LAWS YOU MUST USE ABSOLUTE PRESSURE AND

KELVIN DEGREES (otherwise it won’t work!)