IDC Dive Physiology & Medical Considerations 1 — Questions and Answers
Question 1: Which law explains why a diver's lungs can overexpand if they hold their breath during ascent?
- Henry's Law
- Dalton's Law
- Boyle's Law (Correct answer)
- Charles's Law
Correct answer: Boyle's Law
Boyle's Law states that as pressure decreases, gas volume increases proportionally, so a breath held during ascent will expand and can rupture lung tissue.
Question 2: Type II (serious) decompression sickness (DCS) is distinguished from Type I primarily by the involvement of:
- Joint and muscle pain only
- Skin mottling and itching
- The nervous system, lungs, or cardiovascular system (Correct answer)
- Lymphatic swelling
Correct answer: The nervous system, lungs, or cardiovascular system
Type II DCS involves serious neurological, pulmonary (chokes), or cardiovascular symptoms, while Type I is limited to pain and skin manifestations.
Question 3: A diver experiencing euphoria, impaired judgment, and slowed reaction time at depth is most likely suffering from:
- Oxygen toxicity
- Nitrogen narcosis (Correct answer)
- Carbon dioxide buildup
- Hypoglycemia
Correct answer: Nitrogen narcosis
Nitrogen narcosis, often called 'rapture of the deep,' causes narcotic effects similar to alcohol intoxication at depth due to elevated partial pressure of nitrogen.
Question 4: The primary recommended treatment for decompression sickness in the field before reaching a hyperbaric chamber is:
- Aspirin administration
- Immediate resubmersion to 9 meters
- 100% oxygen breathing (Correct answer)
- Controlled deep breathing exercises
Correct answer: 100% oxygen breathing
Breathing 100% oxygen at the surface accelerates nitrogen washout from tissues and helps reduce bubble size, making it the critical first aid for DCS.
Question 5: According to PADI standards, what is the maximum recommended ascent rate for recreational divers?
- 9 meters (30 feet) per minute (Correct answer)
- 18 meters (60 feet) per minute
- 5 meters (16 feet) per minute
- 25 meters (80 feet) per minute
Correct answer: 9 meters (30 feet) per minute
PADI recommends a maximum ascent rate of 9 meters (30 feet) per minute to allow adequate off-gassing and reduce decompression sickness risk.
Question 6: Which physiological law explains why a diver must breathe more gas molecules per breath at greater depths to fill their lungs?
- Boyle's Law
- Henry's Law
- Dalton's Law (Correct answer)
- Fick's Law
Correct answer: Dalton's Law
Dalton's Law of partial pressures explains that at depth, ambient pressure increases, so lungs must receive proportionally more gas molecules to maintain normal volume.
Question 7: A diver performing repetitive dives needs to account for residual nitrogen primarily because:
- Nitrogen changes the buoyancy of the diver
- Residual nitrogen from prior dives adds to nitrogen absorbed on subsequent dives (Correct answer)
- Nitrogen becomes toxic after multiple exposures
- Surface intervals eliminate all residual nitrogen
Correct answer: Residual nitrogen from prior dives adds to nitrogen absorbed on subsequent dives
Residual nitrogen remaining in tissues from previous dives adds to nitrogen absorbed during subsequent dives, increasing DCS risk if not accounted for in dive planning.
IDC Dive Physiology & Medical Considerations 1
Which law explains why a diver's lungs can overexpand if they hold their breath during ascent?