II. Epidemiology
- Recreational Scuba Incidence: 1 per 5-10,000 dives
- No-Decompression dives account for 50% of DCS cases
III. Pathophysiology
- Atmospheric Pressure at sea level: 14.7 psi (1 ATA or atmosphere absolute)
- Water Pressure Increase
- Water adds 1 ATA of pressure for every 33 feet (10 meters) of depth
- Total Pressure at Depth 33 feet: 2 ATA (29.4 psi)
- Total Pressure at Depth 66 feet: 3 ATA (44 psi)
- Total Pressure at Depth 99 feet: 4 ATA (58.8 psi)
- Henry's Law
- Describes relationship of gas solubility in liquids at Ambient pressure
- Compressed air contains inert gas (e.g. Nitrogen)
- As divers descend to higher water pressures, more nitrogen gas is dissolved in the blood stream
- As divers ascend to lower pressures, gradual off-gassing of nitrogen is required
- Rapid ascent (decompression) does not allow for adequate nitrogen off-gassing
- Insoluble nitrogen bubbles instead precipitate, resulting in Decompression Sickness
IV. Predisposing factors
- Dive logistics
- Deeper dive profile
- Increased rate of ascent
- Hypothermia
- Fatigue
- Advanced age
- Dehydration
- Alcohol intake
- Female gender
- Obesity
- Patent Foramen Ovale
V. Types of Decompression Sickness
- Type I Decompression Sickness (Constitutional DCS)
- Type II Decompression Sickness (Severe)
- Inner Ear DCS
- Neurologic DCS
- Cerebral DCS (30-40%)
- Spinal Cord DCS (50-60%)