CHS Hyperbaric Medicine Principles & Physiology 2 — Questions and Answers
Question 1: According to Henry's Law, what happens to the amount of gas dissolved in a liquid when pressure is doubled?
- The dissolved gas amount decreases by half
- The dissolved gas amount doubles (Correct answer)
- The dissolved gas amount remains unchanged
- The dissolved gas amount quadruples
Correct answer: The dissolved gas amount doubles
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.
Question 2: At 2.0 ATA, a patient breathes 100% oxygen. What is the approximate partial pressure of oxygen (PO2)?
- 0.21 ATA
- 1.0 ATA
- 2.0 ATA (Correct answer)
- 2.5 ATA
Correct answer: 2.0 ATA
Breathing 100% oxygen at 2.0 ATA yields a PO2 of 2.0 ATA (2.0 × 1.0 = 2.0 ATA).
Question 3: Which physiological mechanism primarily accounts for the anti-ischemic benefit of hyperbaric oxygen in crush injuries?
- Increased erythrocyte production
- Reduction of compartment syndrome edema via vasoconstriction (Correct answer)
- Stimulation of platelet aggregation
- Increased cardiac output
Correct answer: Reduction of compartment syndrome edema via vasoconstriction
HBO2-induced vasoconstriction reduces edema in injured compartments while still delivering elevated dissolved oxygen to hypoxic tissues.
Question 4: The Krogh cylinder model of oxygen transport describes which physiological concept?
- Diffusion of oxygen from a capillary to surrounding tissue over a finite radius (Correct answer)
- Oxygen binding to hemoglobin in the pulmonary capillaries
- Venous admixture during hyperbaric treatment
- Arteriovenous oxygen difference at altitude
Correct answer: Diffusion of oxygen from a capillary to surrounding tissue over a finite radius
The Krogh cylinder model illustrates how oxygen diffuses radially from a capillary into a surrounding cylinder of tissue, defining the critical tissue radius.
Question 5: What is the term for the pressure at which nitrogen narcosis first becomes noticeable in most divers breathing air?
- 1.5 ATA
- 2.0 ATA
- 3.0 ATA (Correct answer)
- 4.0 ATA
Correct answer: 3.0 ATA
Nitrogen narcosis typically begins to impair cognitive function at approximately 3.0 ATA (equivalent to about 66 feet of seawater) when breathing compressed air.
Question 6: In hyperbaric oxygen therapy, which pulmonary complication results from prolonged high-dose oxygen exposure and is characterized by progressive alveolar damage?
- Absorption atelectasis
- Oxygen-induced pulmonary toxicity (Lorrain Smith effect) (Correct answer)
- Spontaneous pneumothorax
- Pulmonary barotrauma
Correct answer: Oxygen-induced pulmonary toxicity (Lorrain Smith effect)
The Lorrain Smith effect describes pulmonary oxygen toxicity caused by prolonged high partial pressures of oxygen, leading to inflammation and alveolar damage.
Question 7: Which formula correctly expresses absolute pressure (ATA) for a diver at depth D in feet of seawater?
- ATA = D / 33
- ATA = 1 + (D / 33) (Correct answer)
- ATA = D × 33
- ATA = 1 + (D / 14.7)
Correct answer: ATA = 1 + (D / 33)
Absolute pressure in ATA equals 1 (surface atmospheric pressure) plus the gauge pressure, where each 33 feet of seawater adds 1 ATA.
CHS Hyperbaric Medicine Principles & Physiology 2
According to Henry's Law, what happens to the amount of gas dissolved in a liquid when pressure is doubled?