Diving medicine
Background
- Scuba Diving
- See Scuba diving emergencies
- Underwater diving with the use of a compressed air cylinder, a regulator, a buoyancy compensator, and additional gear that generally includes a wetsuit, fins, mask, dive watch, weights.
- Requires certification, generally through PADI or NAUI
- Divers Alert Network, DAN emergency hotline phone number (919) 684-9111
- Free Diving
- Underwater diving without supplemental oxygen, dating back thousands of years to early shellfish divers. Additional gear may include weights, fins, suit, dive watch.
- Competitive extreme sport, with several sub-categories. Deepest "no limits" depth records for males (214m, 702ft), females (160m, 525ft)
- Snorkeling
- Usually surface or shallow water swimming with the use of a snorkel to allow continuous breathing while the face remains submerged. Often used in resorts or tropical areas.
- Rebreather Diving
- Tethered Diving
- Surface supplied gas supplied by a hose from a source or a diving bell.
- Most often used in commercial or military diving, often in settings with little to no visibility.
Diving Physiology
- Pascals Law applies to the diving body (without air filled areas such as lungs) states that the pressure applied to any part of the enclosed liquid will be transmitted equally in all directions through the liquid.
- Boyles Law applies to the diving body's air filled areas such as lungs, sinuses, middle ear, and states that the volume and pressure of a gas at a given temperature are inversely related.
- At 2 ATA (10m/33ft) a given gas would be 1/2 it's volume, at 3 ATA (20m/66ft) it would be 1/3 it's volume and so on.
- Dalton's Law applies to the total pressure of an ideal gas mixture being the sum of the partial pressures of each individual gas.
- Divers may used Enriched Air NITROX mixtures to proportionally increase partial pressures of oxygen and reduce partial pressures of nitrogen while diving.
- At extremes of depth, additional inert gasses such as helium in TRIMIX are used to further reduce partial pressures of both oxygen and nitrogen below toxic levels.
- Henry's Law applies to the dissolvability of gasses into fluids, including body tissues, being proportional to the partial pressure of the gas.
- The increased pressure at depth causes divers to breath their gas mix at increased pressure to defeat the external water pressure.
- Increased inhaled partial pressures of nitrogen increase risk of nitrogen narcosis, and dissolved nitrogen in tissues re-expanding in micro-bubbles on ascent is the essential cause of decompression sickness. This can affect divers at any depth, including commonly-seen recreational diving depths of 20m/60ft or less.
- Increased inhaled partial pressures of oxygen, generally beyond 1.4-1.6atm, increases risk of oxygen toxicity. This is typically not a substantial risk in common depths of recreational divers at 20m/60ft of depth or less, but can be for more advanced divers at deeper depths.
- The increased pressure at depth causes divers to breath their gas mix at increased pressure to defeat the external water pressure.
Clinical Features
Differential Diagnosis
Diving Emergencies
- Barotrauma of descent
- Otic barotrauma
- Pulmonary barotrauma
- Sinus barotrauma
- Mask squeeze
- Barodentalgia (trapped dental air causing squeeze)
- Barotrauma of ascent
- Pulmonary barotrauma (pulmonary overpressurization syndrome)
- Decompression sickness (DCS)
- Arterial gas embolism
- Alternobaric vertigo
- Facial baroparesis (Bells Palsy)
- At depth injuries
- Oxygen toxicity
- Nitrogen narcosis
- Hypothermia
- Contaminated gas mixture (e.g. CO toxicity)
- Caustic cocktail from rebreathing circuit
- Hypothermia
- Immersion pulmonary edema
- Marine toxins, envenomations, and bites
- Scuba diving emergencies
- Submersion injury (drowning and near-drowning)