Barotrauma

Basics

Description

Injury resulting from the expansion or contraction of gases in an enclosed anatomic space

Etiology

  • Tissue damage results when a gas-filled space does not equalize its pressure with external pressure
  • Boyle’s law: At a constant temperature, pressure (P) is inversely related to volume (V): P1V1 = P2V2:
    • As pressure increases, volume decreases, and vice versa
  • Volume changes are greatest in the few feet nearest the surface
  • Gas-filled cavities are subject to expansion/contraction when unable to equalize internal pressure with surrounding environment:
    • Cutaneous:
      • Air pockets in dive suit/mask expand and contract causing pressure differential with cutaneous vessels
    • Middle ear:
      • Most common type of barotrauma overall
      • Up to 80% of divers report experiencing at some point
      • Due to eustachian tube blockage or dysfunction (common causes: allergies, edema, upper respiratory infection)
      • Increasingly negative pressure gradient across tympanic membrane
    • Sinuses:
      • Negative pressure in sinus cavity causing tissue and vessel swelling
      • Frontal and maxillary sinuses most frequently involved
      • 2nd most common type of barotrauma overall
      • Risk factors include smoking, frequent upper respiratory tract infections, pollen allergy
    • Inner ear:
      • Increased cerebrospinal fluid pressure and middle ear pressure due to repetitive valsalva in attempt to equalize middle ear pressure without success
      • Increased pressure in inner ear may lead to round or oval window rupture and resulting fluid leak
      • Frequently associated with middle-ear barotrauma
    • GI:
      • Expansion of swallowed air in stomach
    • Pulmonary:
      • Gas trapped in lungs from holding breath, rapid ascent or compressed air dive expands causing alveolar distension and possible rupture
      • Risk of gas entry into vascular circulation (see “Arterial Gas Embolism”), interstitial and pleural spaces
      • Risk factors include COPD/asthma or other lung diseases with decreased lung compliance/increased lung volumes

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