Scuba diving emergencies

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Background

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.
Boyle's Law
  • 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.
Dalton's Law
  • 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.

Clinical Features

Differential Diagnosis

Diving Emergencies

Water-related injuries

Evaluation

Management

Barotrauma of Descent

  • Gradual Ascent, avoidance of diving deeper if experiencing pain
  • Decongestants for sinus pain
  • Antibiotic ear drops for TM rupture (choose a formulation such as ofloxacin suspension that is safe in the middle ear)

Barotrauma of Ascent

  • Gradual ascent, safety stops imperative
  • Pulmonary barotrauma may manifest in many ways[1]
    • Local pulmonary injury and pneumomediastinum require supportive care only
    • Treat Pneumothorax according to severity, does not require recompression on its own
    • If any of the above conditions present with altered mental status, presume arterial gas embolism and recompress the patient
    • Arterial gas embolism is the most dreaded complication of diving. It can manifest in many ways depending on where the emboli travel (i.e. stroke, seizure, acute myocardial infarction, or arrythmia. The treatment is immediate hyperbaric oxygen therapy.
    • Decompression sickness (aka the bends) is due to the gas (usually nitrogen) coming out of solution in the blood and tissues secondary to too rapid of an ascent/depressurization. It can present with a myriad of findings, but the most common systems affected are neurologic and musculoskeletal. Those suspected to have this condition should be referred for urgent hyperbaric therapy.

At Depth Injuries

  • Oxygen Toxicity usually results from high ppO2 at several atmospheres of water pressure; though FiO2 is fixed by the gas mixture the diver selects in common, open-circuit diving, the ppO2 varies with depth due to the effects of Dalton's Law and increased pressure delivered by the regulator to defeat external water pressure. Risk of oxygen toxicity rises above 1.4atm ppO2 and even more sharply above 1.6atm ppO2.
    • It can cause pulmonary injury manifesting as chest pain, pleurisy, or even pulmonary edema/hemorrhage. It can also cause CNS pathology manifesting as nausea, auditory changes, convulsions, sweating, twitching, or tunnel vision. Treatment for any of these injuries is ascent and inhalation of lower ppO2 at decreased pressure. More severe presentations of pulmonary injury may require intubation.
  • Nitrogen Narcosis results from inhaling nitrogen containing gas mixtures at high pressures (specialized gas mixtures exist for work at depth that have decreased amounts of nitrogen). It manifests as altered mental status. Treatment is gradual ascent.
  • Hypothermia: re-warm
  • Carbon Monoxide Toxicity: see main section; oxygen, consider hyperbaric therapy
  • Caustic Cocktail: supportive

Disposition

  • Many divers carry insurance covering diving accidents and related medical problems, including costs of transfer for hyperbarics, through the Divers Alert Network - a worldwide, non-profit cooperative dedicated to dive safety. Coverage for transfer costs may require DAN arrange the transfer. Expert consultation over the phone, similar to Poison Control, may also be available. Whether or not you can confirm the patient has such coverage, and unless your facility has hyperbaric treatment available in-house, you should consider contacting them:
    • Divers Alert Network 24/7 hotline - +1-919-684-9111

See Also

References

  1. ↑ Diving Medicine, Karen B. Van Hoesen and Michael A. Lang, Auerbach's Wilderness Medicine, Chapter 71, 1583-1618.e6
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