PADI Dive Physiology and Health 4 — Questions and Answers
Question 1: Arterial gas embolism (AGE) is most likely caused by:
- Breathing air at depth for too long
- Holding the breath during ascent, causing lung over-expansion (Correct answer)
- Ascending faster than 18 m/min
- Nitrogen supersaturation in tissues
Correct answer: Holding the breath during ascent, causing lung over-expansion
Holding the breath during ascent traps expanding air that can rupture alveoli and allow gas bubbles into the arterial circulation.
Question 2: A diver surfaces unconscious immediately after a rapid ascent. The most likely diagnosis is:
- Type I DCS
- Nitrogen narcosis
- Arterial gas embolism (Correct answer)
- Carbon dioxide toxicity
Correct answer: Arterial gas embolism
Immediate unconsciousness upon or shortly after surfacing strongly suggests arterial gas embolism from pulmonary barotrauma.
Question 3: Which lung condition makes a diver particularly susceptible to pulmonary barotrauma?
- Mild dehydration
- Air trapping from asthma or lung cysts (Correct answer)
- Low cardiovascular fitness
- Night blindness
Correct answer: Air trapping from asthma or lung cysts
Conditions that trap air in localized lung areas (e.g., asthma, cysts) prevent equalization of pressure during ascent, risking rupture.
Question 4: Mediastinal emphysema after diving refers to air trapped in the:
- Middle ear
- Joint spaces
- Mediastinum (chest cavity around the heart) (Correct answer)
- Abdominal cavity
Correct answer: Mediastinum (chest cavity around the heart)
Mediastinal emphysema is a type of pulmonary barotrauma where air escapes into the chest cavity surrounding the heart and major vessels.
Question 5: Subcutaneous emphysema from diving barotrauma is characterized by:
- Joint swelling
- Crackling sensation under the skin of the neck and chest (Correct answer)
- Skin mottling from DCS bubbles
- Itching and rash
Correct answer: Crackling sensation under the skin of the neck and chest
Air escaping into subcutaneous tissues causes a distinctive crackling (crepitus) felt when the skin of the neck or chest is touched.
Question 6: Which statement about pneumothorax in diving is correct?
- It is caused by middle ear squeeze
- It occurs when air escapes into the pleural space between lung and chest wall (Correct answer)
- It only affects divers with sinusitis
- It is caused by saltwater inhalation
Correct answer: It occurs when air escapes into the pleural space between lung and chest wall
Pneumothorax occurs when ruptured alveoli allow air to enter the pleural space, collapsing the lung, and is a serious diving barotrauma.
Question 7: What is the recommended treatment for arterial gas embolism?
- Aspirin and lying flat on deck
- Immediate recompression in a hyperbaric chamber with 100% O2 (Correct answer)
- Resubmersion to equalize pressure
- Surface oxygen for 24 hours only
Correct answer: Immediate recompression in a hyperbaric chamber with 100% O2
Recompression in a hyperbaric chamber reduces bubble size and restores circulation, and is the definitive treatment for AGE.
PADI Dive Physiology and Health 4
Arterial gas embolism (AGE) is most likely caused by: