IDC Dive Physiology & Medical Considerations 2 — Questions and Answers
Question 1: Middle ear squeeze (barotrauma) during descent is most directly caused by:
- Overexertion during the dive
- Failure to equalize pressure in the middle ear space (Correct answer)
- Breathing contaminated air
- Rapid nitrogen absorption
Correct answer: Failure to equalize pressure in the middle ear space
Middle ear squeeze occurs when a diver fails to equalize the air space in the middle ear to match increasing ambient pressure during descent, creating a pressure differential that damages tissue.
Question 2: A diver who ascends too rapidly may develop arterial gas embolism (AGE). Which symptom would most strongly suggest AGE rather than DCS?
- Gradual onset of joint pain hours after the dive
- Sudden loss of consciousness or neurological symptoms immediately upon surfacing (Correct answer)
- Skin marbling and itching 30 minutes post-dive
- Fatigue and mild headache the following day
Correct answer: Sudden loss of consciousness or neurological symptoms immediately upon surfacing
AGE typically presents immediately upon or within minutes of surfacing with sudden, severe neurological symptoms because air bubbles enter the arterial circulation and can travel to the brain.
Question 3: Which medical condition is an absolute contraindication to recreational scuba diving?
- Controlled mild asthma
- Spontaneous pneumothorax (history of) (Correct answer)
- Well-controlled Type 2 diabetes
- Mild claustrophobia
Correct answer: Spontaneous pneumothorax (history of)
A history of spontaneous pneumothorax is an absolute contraindication because it indicates lung tissue susceptibility to rupture, making lung overexpansion injury highly likely during ascent.
Question 4: The Valsalva maneuver is used by divers to equalize ear pressure. A potential risk of performing it too forcefully is:
- Nitrogen narcosis
- Inner ear barotrauma or round window rupture (Correct answer)
- Oxygen toxicity
- Carbon monoxide poisoning
Correct answer: Inner ear barotrauma or round window rupture
Forceful Valsalva can rupture the round or oval window of the inner ear, causing permanent hearing loss or vertigo.
Question 5: Carbon monoxide (CO) contamination in a scuba cylinder is most commonly caused by:
- Using the wrong nitrox blend
- Improper positioning of the compressor intake near exhaust fumes (Correct answer)
- Failure to perform a pre-dive equipment check
- Using an aluminum rather than steel cylinder
Correct answer: Improper positioning of the compressor intake near exhaust fumes
CO enters the air supply when a compressor intake is positioned near engine exhaust fumes, allowing combustion byproducts to be compressed into the tank.
Question 6: A reverse block most commonly occurs to a diver who:
- Descends too quickly without equalizing
- Has congestion during ascent that traps expanding gas in a sinus or ear space (Correct answer)
- Breathes from a low-pressure cylinder
- Skips the safety stop
Correct answer: Has congestion during ascent that traps expanding gas in a sinus or ear space
A reverse block happens when congestion or mucus prevents expanding gas from escaping a body air space during ascent, causing pain or injury as ambient pressure decreases.
Question 7: Hypothermia in divers is primarily caused by:
- Breathing cold compressed air
- Excessive heat loss from the body to surrounding water (Correct answer)
- Nitrogen narcosis side effects
- Overexertion at depth
Correct answer: Excessive heat loss from the body to surrounding water
Water conducts heat away from the body approximately 25 times faster than air, causing hypothermia when thermal protection is inadequate for water temperature.
IDC Dive Physiology & Medical Considerations 2
Middle ear squeeze (barotrauma) during descent is most directly caused by: