• To understand how pe injuries occur is it essential to understand 3 physical laws that explain the effects of pressure on gases.

• The volume of gas in an enclosed space is inversely proportional to the pressure exerted on it.

• In effect, as pressure increases, volume decreases. An example would be a balloon.

• If a balloon were inside a chamber, as pressure increases the volume of the balloon decreases. Deflating the balloon. As the pressure inside the chamber decreases, the balloon size would expand, and the volume would increase.

References

1. Tibbles, P., & Edelsberg, J. S. (1996). Hyperbaric-Oxygen Therapy. New Eng J Med, 334, (25).

In thinking about SCUBA ping emergencies, realize that saltwater has a density and this density can be equated to pressure. As a per goes deeper and deeper the pressure increases. As Boyle’s Law states, the volume of air is therefore compressed. At 66 feet underwater, one liter of air would be compressed to 333 1/3rd mL.

• The total pressure of a mixture of gases is equal to the sum of the partial pressure of the inpidual gases.

• At greater depths under the sea the total pressure will increase but each inpidual gas will still account for the same proportion of that total pressure. For example, nitrogen 78%, oxygen 21%, and carbon dioxide less than 1%.

• Henry’s Law states that the amount of gas dissolved in a given volume of fluid is proportional to the pressure of the gas above it.

• This seems like high school physics all over again but this law has important implications for SCUBA pers.

• Lets review what happens to nitrogen and oxygen as a per descends.

• Both gases tend to dissolve in liquid (blood plasma) with the increased pressure of the water bearing down. Oxygen is used by the tissues in metabolism so little is left dissolved in the blood and tissues. Nitrogen is an inert gas and is not used by the body. Nitrogen dissolves.

• As the per descends, the nitrogen is dissolving in the blood and the tissues of the per’s body. When the per now ascends toward the surface (sea level) again the gases that were dissolved are now under less pressure and come out of the blood and tissues.

• Nitrogen is the main gas involved. If the ascent is too rapid, the nitrogen will come out of the blood and tissues as bubbles. You can think of it as unscrewing the top of a soda bottle too quickly. The gas rushes to form bubbles and rise out of the bottle.

1. On the surface
2. During descent
3. On the bottom
4. During ascent

1. Boating accidents
2. Entanglement of lines or in kelp beds
3. Fatigue
4. Cold injury producing shivering or blackout
5. Marine life – sharks, eels, man-o-war

• Barotrauma injuries occur at this phase of ping – “the squeeze.”

• Barotrauma is injury due to the pressure. To equilibrate pressure between the middle ear and the nasopharynx, a per needs a patent eustachian tube. Do not pe if you have an upper respiratory infection.

• Problems at this stage of ping can be:

1. Middle ear pain
2. Tinnitus – ringing in the ear
3. Dizziness
4. Hearing loss
5. Tympanic membrane (eardrum) rupture
6. Severe headaches around the frontal or maxillary sinuses

1. Barotrauma can occur again during ascent as pressures are changing.
2. Decompression illness or “the bends.” Divers going below 40 feet are required to do a staged ascent to prevent the nitrogen from forming bubbles. If the ascent is too rapid, nitrogen will form bubbles causing severe pain especially in the abdomen and in the joints. This is the bends.
3. Pulmonary over-pressure. Air compressed in the lungs expands and can rupture alveoli if not exhaled. This can happen if the per holds his or her breath during ascent.
4. Arterial gas embolism. An air bubble that enters the blood stream from a damaged lung.
5. Pneumomediastinum. Air (gas) that ruptures through the pleura of the lungs into the center of the chest putting pressure on major vessels and the heart.
6. Pneumothorax. Rupture of alveoli causing air (gas) to be in the space surrounding the lung placing pressure and collapsing the lung.

1. History is critical. At what phase of ping did the injury occur?
2. Timing of symptoms. When were symptoms first noted? This can help pinpoint whether the injury is related to ascent, descent, or at the bottom.
3. Type of breathing equipment used.
4. Garments warn. Is hypothermia an issue?
5. Parameters of the pe – The 3 D’s - depth, pes, duration.
6. What was the depth of the pe, the number of pes, and the duration of the pe/s?
7. Rate of ascent.
8. Was panic a factor? Did that cause the ascent to be too rapid?
9. Diver’s experience
10. Old injuries
11. Medications
12. Alcohol

References

1. Bledsoe, B. E., Porter, R. S., & Cherry, R. A. (2001). Paramedic Care: Principles & Practice. Upper Saddle River, NJ: Prentice-Hall, Inc. pp 528-536.
   
2. Rosen, P. et al. (1992). Emergency medicine concepts and clinical practice. St. Louis, MO: Mosby-Year Book Inc. pp. 985-993.

• Abdominal pain
• Joint pain
• Fatigue
• Paresthesias
• Paralysis
• Shock
• Weakness
• Breathing difficulties

• Assess ABC’s
• CPR if needed.
• 100% O2 by non-rebreather if conscious; otherwise intubate.
• Place patient in supine position.
• IV fluids – NS or Lactated Ringer’s. IV fluid should be in collapsible plastic bags. No glass. (glass can break in the chamber)
• Any catheters should be filled with saline not air.
• Rapid transport to nearest ER or facility with hyperbaric oxygen chamber. The longer recompression therapy is delayed the higher the morbidity.
• If transported by un-pressurized helicopter, the pilot should fly as low as possible or cabin pressure should be maintained at sea level.
• Contact the Diver’s Alert Network if unsure of the nearest location of a recompression chamber.

References

1. Bledsoe, B. E., Porter, R. S., & Cherry, R. A. (2001). Paramedic Care: Principles & Practice. Upper Saddle River, NJ: Prentice-Hall, Inc. pp 528-536.
2. Rosen, P. et al. (1992). Emergency medicine concepts and clinical practice. St. Louis, MO: Mosby-Year Book Inc. pp. 985-993.

Arterial Gas Embolism (AGE) is caused by pressure building up in the lungs and subsequent alveoli rupture allowing an air bubble to enter the circulation. Once in the circulation, the air embolism can obstruct blood flow leading to ischemia, infarct and stroke. The onset can occur within 2 to 10 minutes of ascent.

References

1. Bledsoe, B. E., Porter, R. S., & Cherry, R. A. (2001). Paramedic Care: Principles & Practice. Upper Saddle River, NJ: Prentice-Hall, Inc. pp 528-536.

• Sharp tearing pain
• Focal neurological deficits
• Confusion
• Vertigo
• Loss of consciousness
• Visual disturbances

References

1. Bledsoe, B. E., Porter, R. S., & Cherry, R. A. (2001). Paramedic Care: Principles & Practice. Upper Saddle River, NJ: Prentice-Hall, Inc. pp 528-536.
2. Rosen, P. et al. (1992). Emergency medicine concepts and clinical practice. St. Louis, MO: Mosby-Year Book Inc. pp. 985-993.

• Treat AGE as with decompression illness.
• Place patient in lateral decubitus/Trendelenburg position to minimize the chance the air embolism will go to the heart or brain.
• Again, rapid transport to recompression chamber by pressurized aircraft or low altitude flying.

References

1.  Rosen, P. et al. (1992). Emergency medicine concepts and clinical practice. St. Louis, MO: Mosby-Year Book Inc. pp. 985-993.

• 100% O2 via non-rebreather
• IV lactate Ringer’s or normal saline
• Rapid transport

• Simply return to shallow depth. This resolves on ascent. To avoid this problem in deep pes a mixture of oxygen and helium is used. Helium does not cause the anesthetic effect of nitrogen.

• Since treatment of many pe related injuries includes hyperbaric oxygen therapy (HBO) lets review the basics of this treatment.
  
  
• HBO is indicated for other reasons besides SCUBA emergencies and decompression illness.
  
  
• The remainder of this lecture will briefly review the fundamentals of HBO and its clinical applications.

References

1. Bledsoe, B. E., Porter, R. S., & Cherry, R. A. (2001). Paramedic Care: Principles & Practice. Upper Saddle River, NJ: Prentice-Hall, Inc. pp 528-536.
2. Richardson, D. (1999). Open Water Diver Manual PADI. Santa Margarita, CA: International PADI, Inc.

• Breathing 100% oxygen intermittently while in a pressurized environment.
• It can be compared to scuba ping without the water.

• Mask
• Hood
• Endotracheal tube
• Or ambient air depending on the type of hyperbaric chamber used.

• Is pressurized with 100% oxygen, not air.
• Size allows only one adult or possibly 2 children to occupy the chamber.
• Advantage is that it does not require a health care attendant (i.e.; physician, nurse, RRT, or EMT) to accompany the patient.
• Disadvantage is the there is no “hands on” contact.

• Pressurized with air.
• Patient breathes 100% oxygen via hood, mask, or endotracheal tube.
• Two or more patients, depending on the size of the chamber, plus a health care attendant can be treated at one time.
• Advantage - allows for a hands on ICU environment.
• Disadvantage -A full complement of staff is required.
• The attendants are exposed to a pressurized environment while accompanying the patient(s), therefore exposing them to a risk of decompression sickness.

• The number of monoplace chambers exceeds the number of multiplace chambers in the United States.

• Remember, the patient breathes 100% oxygen while under pressure, therefore increasing the oxygen content of blood by increasing tissue oxygen tensions via the plasma and hemoglobin.
• Help produce small blood vessels known as capillaries.
• It can also act as an antibiotic against certain organisms that thrive on low oxygen levels.
• Thought to increases cell production quicker.

• Normal arterial oxygen (paO2) levels in the body are 80mmHg-100mmHg. HBO can allow the body to increase its oxygen uptake to a maximum of 2183mmHg during a treatment.

• This effect is used for indications such as carbon monoxide poisoning, cyanide poisoning, burns, severe anemia, gas gangrene, crush Injury, compartment syndrome, other acute traumatic Ischemia and adjunctive therapy for enhancement of healing in selected problem wounds.

• BCLS
• IV
• Debridement if indicated
• Wound care if indicated

• Air or Gas Embolism
• Carbon Monoxide Poisoning and Smoke Inhalation
• Cyanide Poisoning
• Clostridial Myonecrosis (Gas Gangrene)
• Crush Injury, Compartment Syndrome and other Acute Traumatic Ischemia
• Decompression Sickness

• Central line insertion
• O.R. procedure such as coronary arterial bypass graft
• Other procedures

• Collapsed lung
• Scuba ping
• Swimming
• Oral Sex

• Decreases size of air/gas embolism as pressure increases in chamber
• Hyper oxygenate hypoxic tissues

• Gasoline
• Propane
• Natural gas
• Oil
• Wood
• Coal

• Decrease the half life of carboxyhemoglobin levels. This means faster clearing of carbon monoxide.
• Hyper-oxygenates hypoxic tissues

• A toxin that thrives in arterial levels of 300 mmHg or less
• Spreads 1 – 6 inches an hour

• Effects of HBO on Clostridial Myonecrosis
  • Hyper-oxygenate hypoxic tissues

• Acute insult to tissues leading to hypoxia caused by trauma and/or circumferential constriction of tissues
  
  
• Effects of HBO on Crush Injury, Compartment Syndrome and other Acute Traumatic Ischemia
  • Hyper-oxygenate hypoxic tissues

• Nitrogen bubble formation that can develop in areas such as blood stream, spinal fluid, joint areas, inner ear and others

• Found in SCUBA pers, attendants in the hyperbaric environment or High Altitude Flying

• Can occur even after the per is out of the water, especially if flying within 12 hours of the pe

• Effects of HBO on Decompression Sickness
  • Decreases size of air/gas embolism as pressure increases in chamber
  • Hyper-oxygenate hypoxic tissues

• Can be transported by car, ambulance, helicopter, or plane UNLESS PATIENT IS DIAGNOSED WITH DECOMPRESSION SICKNESS OR AIR/GAS EMBOLISM!

• Increase in altitude will decrease barometric pressure therefore increasing bubble size and increasing symptoms

• Can only be transported in surface transportation, low altitude helicopter or in a pressurized aircraft which does not exceed a cabin atmosphere of 800 feet of altitude. Commerical airline flights are not rated for transport since they exceed this cabin atmosphere.

• A nonprofit organization associated with Duke University Medical Center that has ability to refer SCUBA pers and other people in need of a hyperbaric chamber facility.

• www.persalertnetwork.org

• Dan’s Diving Emergency Hotline can be reached 24 hours a day, 365 days a year at (919) 684-4DAN or you can call collect at (919) 684-8111.

• Professional organization including physicians, nurses, respiratory therapist, pers and other groups

• Reviews scientific literature

• Recommends guidelines for use of HBOT

• www.UHMS.org

• Professional organization which includes nurses.

• Reviews scientific literature.

• Recommends nursing guidelines for use of HBOT.

• www.hyperbaricnurses.com

In conclusion, hyperbaric medicine is being utilized to help both improve and save lives of patients diagnosed with these diseases/conditions. As research continues in this field, advances will be made to understand more fully the potential of hyperbaric oxygen therapy.

References

1. Davis, JC and TK Hunt. Hyperbaric Oxygen Therapy. Undersea Medical Society, Bethesda, 1977.
2. Kindwall, E. Hyperbaric Medicine Practice. Best Publishing Company, Flagstaff, 1994.
3. Shilling, C and C Carlston, et all. The Physician’s Guide to Diving Medicine. Undersea Hyperbaric Medical Society, Bethesda, 1984.

1. Davis, J. C. & Hunt, T. K. (1977). Hyperbaric Oxygen Therapy. Undersea Medical Society, Bethesda, MD.
2. Kindwall, E. (1994). Hyperbaric Medicine Practice Best Publishing Company, Flagstaff.
3. Shilling, C. & Carlston, C. (1984). The Physician's Guide to Diving Medicine . Undersea Hyperbaric Medical Society, Bethesda, MD.
4. Rosen, P. (1992). Emergency Medicine Concepts and Clinical Practice. Mosby Year Book, St. Louis, MO.
5. Richardson, D. (1999). Open Water Dive Manual. International PADI, Inc., Santa Margarita, CA.
6. Tibbles, P. & Edelsberg, J. S. (1996). Hyperbaric-Oxygen Therapy. New England Journal of Medicine, 334,25.
7. An Overview of Hyperbaric Medicine. Patient Care, July 15, 2000.
8. Ernst, A. & Zibrak, J. D. Carbon Monoxide Poisoning. New England Journal of Medicine, 339, 22.
9. Bledsoe, B. E., Porter, R. S. & Cherry, R. A. (2001). Paramedic Care: Priniples and Practice Medical Emergencies. Prentice-Hall Inc., Upper Saddle River, NJ.
10. Good Pressure: What you need to know about hyperbaric chambers. (November/December 1999). Alert Diver: The Magazine of Divers Alert Network.