0071643192.pdf

ENVIRONMENTAL EMERGENCIES

Descent Dysbarism

Descent dysbarism can occur in any air-filled space in the body (see Table 13.13).
Overall, middle ear squeeze is the most common manifestation.

PATHOPHYSIOLOGY

■ ↑dive depth →increased ambient pressure and “squeeze” (barotrauma)
of air-filled spaces in body →symptoms if body unable to equalize
pressures.

TREATMENT

■ Depends on location and severity of injuries
■ Most injuries respond to conservative therapy (rest) alone.
■ Prophylactic antibiotics if ruptured TM
■ Oral steroids if 7th nerve palsy
■ Topical nasal decongestants for ear and sinus squeeze
■ Recompression therapy is notindicated.
■ No further diving (until injuries have healed)

Dysbarism at Depth

NITROGENNARCOSIS

Nitrogen narcosis occurs when scuba tank air (containing nitrogen and O 2 ) is
breathed at depth. Symptoms of nitrogen narcosis typically occur after the
diver has descended to ≥100 ft.

TABLE 13.13. Descent Dysbarism

LOCATION OF

“SQUEEZE”UNDERLYINGCAUSE SYMPTOMS

External ear Obstruction of external ear Ear pain

canal (noear plugs!)

Middle ear External pressure on TM not Ear pain

equalized by eustacian tube Hearing loss

TM rupture →nystagmus and vertigo

Seventh nerve palsy

Inner ear Transmission of middle ear Ear pain

pressure→rupture of round Hearing loss

window Severe nystagmus and vertigo →

ataxia and vomiting

Sinus Obstruction of sinus ostia Facial pain

Epistaxis

Lung Holding breath during descent Shortness of breath

Hemoptysis

Pulmonary edema

Equipment Tight-fitting mask or wet suit Petechiae