CHS Hyperbaric Medicine Principles & Physiology 3 — Questions and Answers
Question 1: Which cell type is most responsible for the angiogenic response stimulated by hyperbaric oxygen therapy in wound healing?
- Neutrophils
- Endothelial cells (Correct answer)
- Mast cells
- Osteoclasts
Correct answer: Endothelial cells
HBO2 upregulates vascular endothelial growth factor (VEGF) in endothelial cells, driving neovascularization in hypoxic wound tissue.
Question 2: Boyle's Law is most directly applied when calculating the risk of which hyperbaric injury?
- Oxygen toxicity
- Decompression sickness
- Pulmonary barotrauma during ascent (Correct answer)
- Nitrogen narcosis
Correct answer: Pulmonary barotrauma during ascent
Boyle's Law (P1V1 = P2V2) explains gas expansion during ascent; if a diver breath-holds, expanding lung gas can cause pulmonary barotrauma.
Question 3: What is the primary reason hyperbaric oxygen is effective in carbon monoxide poisoning beyond simply displacing CO from hemoglobin?
- It stimulates the Haldane effect to increase CO binding
- It accelerates CO dissociation from intracellular myoglobin and cytochrome oxidase (Correct answer)
- It increases 2,3-DPG levels
- It causes therapeutic hypothermia
Correct answer: It accelerates CO dissociation from intracellular myoglobin and cytochrome oxidase
HBO2 accelerates CO dissociation from mitochondrial cytochrome oxidase and myoglobin, restoring cellular respiration beyond what normobaric oxygen achieves.
Question 4: During a hyperbaric treatment at 2.4 ATA breathing 100% O2, what approximate dissolved oxygen (mL O2/dL blood) is present in plasma alone?
- 0.3 mL/dL
- 3.0 mL/dL
- 6.0 mL/dL (Correct answer)
- 20 mL/dL
Correct answer: 6.0 mL/dL
At 2.4 ATA with 100% O2, PO2 ≈ 1,800 mmHg; using the solubility coefficient (~0.003 mL/dL/mmHg), dissolved O2 ≈ 5.4–6.0 mL/dL, sufficient to meet resting tissue needs.
Question 5: Which decompression sickness symptom pattern is classified as Type II (serious) DCS?
- Joint pain only in the elbow
- Skin mottling (cutis marmorata) without neurological symptoms
- Spinal cord or cerebral deficits (Correct answer)
- Ear pain and mild dizziness
Correct answer: Spinal cord or cerebral deficits
Type II DCS involves serious manifestations including neurological symptoms such as spinal cord or cerebral involvement, versus Type I which involves musculoskeletal or skin symptoms only.
Question 6: What is the physiological basis for using hyperbaric oxygen to treat gas gangrene (clostridial myonecrosis)?
- Oxygen directly kills Clostridium by disrupting their cell membranes via oxidative burst
- High tissue PO2 inhibits the alpha toxin production of obligate anaerobic Clostridium species (Correct answer)
- Pressure mechanically disrupts bacterial cell walls
- HBO2 stimulates macrophage phagocytosis of Clostridium spores
Correct answer: High tissue PO2 inhibits the alpha toxin production of obligate anaerobic Clostridium species
Clostridium perfringens is an obligate anaerobe; elevated tissue PO2 from HBO2 inhibits toxin production and bacterial growth, halting disease progression.
Question 7: The oxygen window (inherent unsaturation) is important in decompression theory because it:
- Prevents nitrogen from dissolving into blood at depth
- Creates a pressure gradient that facilitates inert gas elimination (Correct answer)
- Causes bubble formation during rapid ascent
- Increases the rate of oxygen toxicity seizures
Correct answer: Creates a pressure gradient that facilitates inert gas elimination
The oxygen window refers to the partial pressure 'vacancy' created by oxygen metabolism, providing a gradient that drives inert gas out of tissues during decompression.
CHS Hyperbaric Medicine Principles & Physiology 3
Which cell type is most responsible for the angiogenic response stimulated by hyperbaric oxygen therapy in wound healing?