0071643192.pdf

ENVIRONMENTAL EMERGENCIES

PATHOPHYSIOLOGY

■ Increasing dive depth →increased ambient pressure →↓volume of tank

air (Boyle’s law) and ↑partial pressure of nitrogen in inspired tank air →

increased nitrogen dissolved in blood (Henry’s law) →symptoms.

SYMPTOMS/EXAM

■ Altered behavior

■ Poor judgment

■ Hallucinations and loss of consciousness

TREATMENT

■ Ascend slowly with assistance.

■ Slow ascent is essential to prevent ascent dysbarism (see below).

■ Use mixtures with less nitrogen in the inspired tank for dives >100 ft.

OXYGENTOXICITY

Results from breathing elevated partial pressures of O 2 for extended periods of

time; primarily affects the CNS and lungs

SYMPTOMS/EXAM

■ Tunnel or blurred vision

■ Nausea/vomiting

■ Dizziness and paresthesias

■ Twitching, seizures

TREATMENT

■ Ascend slowly with assistance.

■ Slow ascent is essential to prevent ascent dysbarism (see below).

Ascent Dysbarism

ASCENTBAROTRAUMA

Ascent barotrauma is caused by expansion of gas on ascent from diving.

PATHOPHYSIOLOGY

■ ↓In ambient pressure →↑in size of air-filled spaces.

■ Failure of air to passively exit middle ear due to blocked eustacian tube →

alternobaric vertigo.

■ Breath-holding during ascent →air dissects into pulmonary tissue (sub-

cutaneous emphysema to pneumomediastinum to pneumothorax).

SYMPTOMS/EXAM

■ Alternobaric vertigo

■ Ear pain and possible TM rupture

■ Severe but transient nystagmus and vertigo

■ Nausea/vomiting may occur.

■ Transient hearing loss

■ Pulmonary barotrauma

■ Shortness of breath

■ Hemoptysis

■ Chest pain