Certified Hyperbaric Technologist Test Hyperbaric Physics Fundamentals 1 — Questions and Answers
Question 1: What does Boyle's Law state and how does it apply to hyperbaric medicine?
- At constant temperature, gas volume is inversely proportional to pressure — explains barotrauma and why air spaces compress under pressure (Correct answer)
- Gas pressure is directly proportional to temperature
- Gases diffuse from low to high concentration
- Gas solubility increases with temperature
Correct answer: At constant temperature, gas volume is inversely proportional to pressure — explains barotrauma and why air spaces compress under pressure
Boyle's Law (PV=k) states that gas volume decreases proportionally as pressure increases at constant temperature, explaining why middle ear spaces, sinuses, and lungs compress during descent and expand during ascent.
Question 2: What does Henry's Law state and why is it important in HBO therapy?
- Gas dissolved in a liquid is proportional to the partial pressure of that gas — explains how HBO increases dissolved oxygen in blood (Correct answer)
- Gases always rise to the surface of liquids
- All gases dissolve equally in water
- Gas temperature determines its solubility
Correct answer: Gas dissolved in a liquid is proportional to the partial pressure of that gas — explains how HBO increases dissolved oxygen in blood
Henry's Law states that the amount of gas dissolved in a liquid is directly proportional to the partial pressure of that gas above the liquid, explaining how breathing oxygen at elevated pressures dramatically increases dissolved oxygen in plasma.
Question 3: What is Dalton's Law of Partial Pressures?
- The total pressure of a gas mixture equals the sum of the partial pressures of each component gas (Correct answer)
- Gases of different densities separate in a mixture
- All gases exert equal pressure regardless of concentration
- Gas pressure depends only on container size
Correct answer: The total pressure of a gas mixture equals the sum of the partial pressures of each component gas
Dalton's Law states that each gas in a mixture exerts pressure independently, and the total pressure equals the sum of all partial pressures. At 3 ATA breathing 100% O2, the PO2 is 3.0 ATA × 1.0 = 3.0 ATA (2,280 mmHg).
Question 4: What is oxygen toxicity and what are its two forms?
- Harmful effects from excessive oxygen: CNS toxicity (seizures) at high pressures and pulmonary toxicity from prolonged exposure (Correct answer)
- Lack of oxygen in the blood
- Allergic reaction to oxygen masks
- Dehydration caused by breathing dry oxygen
Correct answer: Harmful effects from excessive oxygen: CNS toxicity (seizures) at high pressures and pulmonary toxicity from prolonged exposure
CNS oxygen toxicity (Paul Bert effect) occurs at high partial pressures (typically >2.0 ATA PO2) causing seizures, while pulmonary toxicity (Lorrain Smith effect) results from prolonged breathing of elevated oxygen, causing lung inflammation.
Question 5: How does gauge pressure differ from absolute pressure in hyperbaric medicine?
- Gauge measures pressure above atmospheric; absolute includes atmospheric pressure (gauge + 1 ATA at sea level) (Correct answer)
- They are always equal
- Absolute pressure is always lower than gauge
- Gauge pressure is used only in metric systems
Correct answer: Gauge measures pressure above atmospheric; absolute includes atmospheric pressure (gauge + 1 ATA at sea level)
Gauge pressure (psig) measures pressure above atmospheric baseline, while absolute pressure (psia or ATA) includes atmospheric pressure. At sea level: 1 ATA absolute = 0 psig. At 2 ATA: gauge is 14.7 psig.
Question 6: What is the significance of 1.3 ATA in hyperbaric medicine?
- It is the minimum pressure defined by UHMS for hyperbaric oxygen therapy — below this is not considered HBO (Correct answer)
- It is the maximum safe treatment pressure
- It is the standard pressure for all treatments
- It has no special significance
Correct answer: It is the minimum pressure defined by UHMS for hyperbaric oxygen therapy — below this is not considered HBO
The Undersea and Hyperbaric Medical Society defines HBO as breathing 100% oxygen at a pressure of at least 1.3 ATA. Treatment below this threshold is not considered true hyperbaric oxygen therapy.
Certified Hyperbaric Technologist Test Hyperbaric Physics Fundamentals 1
What does Boyle's Law state and how does it apply to hyperbaric medicine?