Undersea Medicine. Michael Jacobs MD MPH Undersea Medical Officer Occupational/Preventive Medicine Physician Naval Hospital Great Lakes [email protected] Learning Objectives. Understand the scope of undersea medicine practice Understand basic principles of diving physiology
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P = Pressure
D = Depth
fsw = Feet of sea water
P (atm) = D (fsw) + 1
A rubber balloon with a volume of 1 cf at the surface is submerged to a depth of 33 fsw. What is the volume of the balloon now?
P1V1 = P2V2 P1 = atmospheric press.
1 atm x 1 cf = 2 atm x V2 V1 = volume at P1
0.5 cf = V2 P2 = press at 33 fsw
V2 = volume at 33 fsw
Sea Level 1 atm Vol=1
33 fsw 2 atm Vol=1/2
66 fsw 3 atm Vol=1/3
99 fsw 4 atm Vol=1/4
As a diver descends, atmospheric pressure increases and the volume of compressible tissues/gases decreases (e.g. gas bubbles, lung tissue)
(P = pressure, pP = partial pressure)
(F = % gas by volume)
pPO2 = 1 atm (0.21) = 0.21 atm
pPO2 = 4 atm (0.21) = 0.84 atm
As a diver descends, inspired gases are more soluble in blood
Example: At 66 fsw, pPN2 = 3 atm * 0.79 = 2.4 atm
Blood Diffusion Direction Tissue
pPN2 = 2.4 atm pPN2 = 0 atm
As a diver descends, inspired gases diffuse into tissues; as a diver ascends, gases diffuse out of tissues and into the blood
In 1900, a Royal Navy diver descended to 150 fsw in 40 minutes, spent 40 minutes at depth searching for a torpedo, and ascended to the surface in 20 minutes with no apparent difficulty. Ten minutes later he complained of abdominal pain and fainted. His breathing was labored, he was cyanotic, and he died after seven minutes. An autopsy the next day revealed the organs to be healthy, but gas was present in the liver, spleen, heart, cardiac veins, venous system, subcutaneous fat, and cerebral veins and ventricles. By present U.S. Navy Standard Air Decompression Tables, this diver should have had 174 minutes of decompression time before reaching the surface.
Diagnosis: Decompression Sickness (DCS)
*Bert P. Barometric pressure. Researches in experimental physiology. Bethesda, MD. Undersea Medical Society, 1878.
You and your dive buddy are out on the Great Barrier Reef. Your dive buddy is a novice diver on his first “real” diving trip. Your first dive is planned to a depth of 60 fsw for 45 minutes. Thirty-five minutes into your dive, your dive buddy points frantically toward a beautiful nine foot reef shark. After observing the shark for a few moments, you turn back to see your dive buddy swimming quickly for the surface. By the time you reach him on the surface, he is unconscious. The boat crew brings him on board and finds him unresponsive with a weak pulse. A review of your diving profile reveals that the dive was well within the decompression limits for a 60 ft dive. All other divers on the boat had no complications from their dives. What is the most likely diagnosis?
Diagnosis: Arterial Gas Embolism
*U.S. Navy Diving Manual Revision 4, March 2001