PADI - Professional Association of Diving Instructors Dive Physiology and Health Questions and Answers — Questions and Answers
Question 1: A diver surfaces from a 30-meter (100-foot) dive and within 10 minutes complains of extreme fatigue, dizziness, and a tingling sensation in their arms. Which of the following conditions is most likely responsible for these symptoms?
- Nitrogen Narcosis
- Decompression Sickness (DCS) (Correct answer)
- Oxygen Toxicity
- Lung Overexpansion Injury
Correct answer: Decompression Sickness (DCS)
Decompression Sickness (DCS), also known as 'the bends,' occurs when nitrogen absorbed by the body at depth comes out of solution and forms bubbles as pressure is reduced during ascent. Symptoms can include joint pain, dizziness, fatigue, and numbness or tingling. Nitrogen narcosis symptoms would have disappeared upon ascent. Oxygen toxicity is unlikely on a standard recreational air dive at this depth. A lung overexpansion injury would typically present with more immediate and severe respiratory or circulatory symptoms.
Question 2: Which of the following is the most effective and immediate field treatment for a diver exhibiting signs of Nitrogen Narcosis?
- Administering 100% oxygen at the surface.
- Immediately performing a recompression dive.
- Ascending to a shallower depth. (Correct answer)
- Monitoring the diver at their current depth.
Correct answer: Ascending to a shallower depth.
Nitrogen narcosis is caused by the increased partial pressure of nitrogen at depth, which has an anesthetic effect. The effects are temporary and are immediately reversible by ascending to a shallower depth where the partial pressure of nitrogen is lower. Administering oxygen is for decompression illness, and recompression dives are not a first-aid procedure. Monitoring at the current depth would not resolve the issue.
Question 3: Central Nervous System (CNS) Oxygen Toxicity is a risk primarily associated with diving with enriched air nitrox. Which acronym is commonly used to remember the signs and symptoms of CNS Oxygen Toxicity?
- RICE (Rest, Ice, Compression, Elevation)
- FAST (Face, Arms, Speech, Time)
- SAMPLE (Signs/Symptoms, Allergies, Medications, Past history, Last meal, Events)
- CONVENTID (Convulsions, Visual disturbances, Ear ringing, Nausea, Twitching, Irritability, Dizziness) (Correct answer)
Correct answer: CONVENTID (Convulsions, Visual disturbances, Ear ringing, Nausea, Twitching, Irritability, Dizziness)
The acronym CONVENTID is used to help divers remember the potential signs and symptoms of Central Nervous System (CNS) Oxygen Toxicity. These include Convulsions, Visual disturbances (like tunnel vision), Ear ringing, Nausea, Twitching (especially in facial muscles), Irritability, and Dizziness.
Question 4: A diver is having difficulty equalizing their ears during a rapid descent. To prevent a middle ear barotrauma, which is the most critical action to take?
- Forcefully attempt the Valsalva maneuver.
- Continue the descent while wiggling the jaw.
- Stop the descent, ascend slightly, and attempt to equalize again. (Correct answer)
- Tilt the head to one side and swallow hard.
Correct answer: Stop the descent, ascend slightly, and attempt to equalize again.
If a diver experiences difficulty equalizing, they should immediately stop their descent. The pressure differential may be too great to overcome. Ascending a few feet will reduce the ambient pressure, making it easier for the Eustachian tubes to open and allow equalization. Forceful equalization can cause injury. Continuing descent will worsen the pressure imbalance and increase the risk of barotrauma.
Question 5: What is the primary physiological reason a diver should never hold their breath while ascending on scuba?
- To prevent carbon dioxide buildup.
- To avoid nitrogen narcosis.
- To prevent a lung overexpansion injury. (Correct answer)
- To conserve air in the cylinder.
Correct answer: To prevent a lung overexpansion injury.
According to Boyle's Law, the volume of a gas is inversely proportional to the pressure. As a diver ascends, the ambient pressure decreases, causing the air in the lungs to expand. If the diver holds their breath, this expanding air can over-pressurize and rupture the lungs, leading to serious injuries like an arterial gas embolism (AGE), pneumothorax, or emphysema.
Question 6: A diver on a deep air dive begins to experience impaired judgment, a false sense of security, and difficulty concentrating. This diver is most likely experiencing:
- Hypothermia
- Decompression Sickness
- Nitrogen Narcosis (Correct answer)
- Oxygen Toxicity
Correct answer: Nitrogen Narcosis
Nitrogen narcosis, also known as 'raptures of the deep', is an altered state of mind caused by breathing nitrogen at high partial pressures. The symptoms are similar to alcohol intoxication and include impaired judgment, euphoria, overconfidence, and difficulty with cognitive tasks. These symptoms typically become apparent on dives deeper than 30 meters (100 feet).
PADI - Professional Association of Diving Instructors Dive Physiology and Health Questions and Answers
A diver surfaces from a 30-meter (100-foot) dive and within 10 minutes complains of extreme fatigue, dizziness, and a tingling sensation in their arms.
Which of the following conditions is most likely responsible for these symptoms?