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Hyperbaric Chamber: How does it work?

Discussion in 'Ask Dr. Decompression' started by TMHeimer, Nov 8, 2018.

  1. TMHeimer

    TMHeimer Divemaster

    # of Dives: 500 - 999
    Location: Dartmouth,NS,Canada(Eastern Passage-Atlantic)
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    I of course understand much about DCS, and it's causes. And about atms/water pressure, how a reg works to deliver gas at the ambient pressure, etc. -- tissue loading, M Values, etc.
    Hyperbaric Chamber--- In layman's terms, how do they simulate that? Exactly what do they do to increase or decrease the pressure inside the chamber? Force in/let out more air?
     
  2. northernone

    northernone IDC Staff Instructor Staff Member

    # of Dives: 1,000 - 2,499
    Location: Currently: Cozumel, from Canada
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    Exactly right. Basically sitting inside a giant scuba tank being slowly filled with compressed gas and than slowly vented to reduce the pressure at a controlled rate.
     
  3. TMHeimer

    TMHeimer Divemaster

    # of Dives: 500 - 999
    Location: Dartmouth,NS,Canada(Eastern Passage-Atlantic)
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    Thanks. That's kinda what I figured. If you're in there, do you feel the air being forced in? Does it come from several vents, or some kind of osmosis through the walls?
     
  4. northernone

    northernone IDC Staff Instructor Staff Member

    # of Dives: 1,000 - 2,499
    Location: Currently: Cozumel, from Canada
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    There are hoses in the chamber wall coming from outside where the high pressure gas is regulated and the flow is controlled. There's the hiss of a valve as the air flows in... It also gets hot when the pressure increases and cold as the pressure is bled off.

    You need to equalize just like diving... Or, come to think of it, an airplane with a pressurized cabin feels somewhat similar. I was looking around YouTube for a good video but was unable to find one.

    Chamber tours are available too.

    Cameron
     
  5. TMHeimer

    TMHeimer Divemaster

    # of Dives: 500 - 999
    Location: Dartmouth,NS,Canada(Eastern Passage-Atlantic)
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    Thanks again.
     
  6. JamesBon92007

    JamesBon92007 Loggerhead Turtle

    # of Dives: 2,500 - 4,999
    Location: Southern California...too far from the ocean
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    @northernone You make that sound like personal experience. I rather hope it wasn't.

    I've sat next to the one on Cozumel on Calle 6 N a few times while my girlfriend was visiting the doctor and to me it looks like it only has one inlet. There's an intercom and a whole bunch of gauges and valves which make it appear that it's not all that simple to operate, but the principle is simple enough.

    Chamber Calle 6 N.jpg
     
  7. Duke Dive Medicine

    Duke Dive Medicine Medical Moderator Staff Member

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    They're pretty simple once you break the functions down. Some multiplace chambers run directly from a compressor/volume tank, and some (like the ones at Duke) are supplied from HP flasks that are charged as needed. There's typically a primary air supply and exhaust valve for each lock, and also a secondary air supply for each. Oxygen for the BIBS (built-in breathing system) masks or oxygen head tents is supplied through separate plumbing. The one in the photo that @JamesBon92007 looks like a twin-lock deck decompression chamber like you'd find on a commercial diving station. Locks are really chambers within the chamber. If you looked in the hatch at the end you'd see another hatch about 1/4-1/3 of the way back; that's the inner lock hatch. Chambers like that are typically operated with the inner lock at pressure and the outer lock on the surface so that supplies and personnel can be locked in if necessary. Many chambers have a medical lock (basically a small air lock) for sending in supplies.

    The chamber simulates the pressure of diving. The function of diving gear is to deliver gas at a pressure that allows the diver to inflate his or her lungs against the ambient water pressure, so the pressure of the gas the diver is breathing is essentially the same as the ambient water pressure. A person in a chamber that's pressurized to a depth equivalent of 60 feet of sea water (2.82 atmospheres of pressure, or 26.7 psi gauge) is breathing gas at the same pressure that a diver at 60 feet would be breathing.

    Chamber treatment for DCS does a couple of things. First, the increased pressure in the chamber will cause any remaining bubbles in the diver's body to shrink, which will improve circulation to the affected area. The diver breathes oxygen for most of the treatment, which dissolves oxygen into the plasma by the same principle that causes inert gas to dissolve in the body: Henry's Law. Oxygen that's dissolved in the plasma is carried to tissues when the plasma leaks out of the capillaries (this is physiologically normal, it's what your lymphatic system is for). Since there's so much more oxygen in the plasma, it penetrates deeper into the tissues.

    Hyperbaric oxygen has other physiologic effects: the reactive oxygen species ("free radicals") produced in hyperbaric hyperoxia will basically scavenge nitric oxide, which is an endogenous vasodilator - this produces net vasoconstriction, which can help with inflammation. It also interrupts the inflammatory cascade by interfering with beta-2 integrin, which is a protein that helps white blood cells bind to the walls of the blood vessels in areas of inflammation. In people with chronically poor circulation (diabetes, radiation tissue damage), the burst of oxygen activates the body's own system for growing new capillaries.

    Hope this helps!

    Best regards,
    DDM
     
  8. Johnoly

    Johnoly Solo Diver

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    It's a very narrow tube and they wheel you inside. There's a big guy dressed all in white and as soon as the door closes it's sound proof, HOT and almost no windows. He straps your arms to the gurney, pulls out some files and tells you he's from the IRS. For the next 5 hours you try to explain all that cash you spent on dive gear and gentlemen's clubs on remote islands. Your whole body is trembling with fear and no escape. This releases the so-called bubbles and you will say ANYTHING just to get away from there so they won't tell your wife. And that's why everyone says they feel so much better once out of the chamber. I read about it on the internet!!
     
    TONY CHANEY and JamesBon92007 like this.
  9. tech_diver

    tech_diver Dive Equipment Manufacturer

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    In Nasa's Neutral Buoyancy Lab across from their Deco chamber, they also have a 'hypobaric' chamber. A chamber where they can subject people to sudden drops in ambient pressure as training for a sudden loss of pressure in an aircraft or spacecraft. It's like the opposite of a hyperbaric chamber.
     
  10. Akimbo

    Akimbo Lift to Freedom Volunteer Staff Member ScubaBoard Supporter

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    Here is an image of a double lock (2-compartment) chamber with very nearly the minimum controls:

    full.jpg

    The color code shows the basic systems:
    • Black = air supply for pressurizing (descending) and ventilation
    • Silver = exhaust for depressurizing (ascending) and ventilation
    • Green = Oxygen supply for BIBS masks (Built-In Breathing System)
    • Yellow = depth monitoring (pressure gauges calibrated in feet and/or meters of sea water)
    Some jurisdictions require overboard dump BIBS masks which makes it easier to prevent high Oxygen concentrations/fire hazards. That requires another vent/exhaust valve for each lock. Here is a cross-section drawing of a typical double lock chamber.

    full.jpg
     

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