HYPERBARIC MEDICINE (HBO) COMPREHENSIVE
EXAM PRACTICE QUESTIONSWITH CORRECT
ANSWERS & EXPLANATIONS
1. The term “ascent” means:
A. Increase in pressure
B. Decrease in pressure (decompression)
C. Constant ambient pressure
D. Oxygen toxicity
Answer: B. Decrease in pressure (decompression)
Explanation: Ascent refers to movement toward a lower pressure environment. In hyperbaric
and diving medicine, ascent results in decreasing ambient pressure. This pressure reduction
allows gases to come out of solution. Controlled ascent is critical to prevent decompression
sickness.
2. Which toxin produced by Clostridium perfringens is affected by hyperbaric oxygen
therapy?
A. Beta toxin
B. Gamma toxin
C. Alpha toxin
D. Theta toxin
Answer: C. Alpha toxin
Explanation: Alpha toxin is responsible for tissue destruction and hemolysis in gas gangrene.
Hyperbaric oxygen inhibits the production of this toxin. HBO also suppresses bacterial growth
and improves leukocyte function. This makes HBO an important adjunctive therapy.
3. The appropriate treatment for a hypoglycemic reaction is:
A. Administer insulin
B. Increase oxygen pressure
C. Feed the patient if conscious
D. Begin chamber decompression
Answer: C. Feed the patient if conscious
Explanation: Hypoglycemia requires prompt correction with glucose. If the patient is conscious
and able to swallow, oral carbohydrates are preferred. This prevents neurological damage.
Unconscious patients require IV glucose.
4. The proper response to complaints of ear pain during pressurization is to:
A. Continue compression
B. Increase compression rate
C. Stop compressing the chamber
,D. Decompress immediately
Answer: C. Stop compressing the chamber
Explanation: Ear pain during compression usually indicates failure to equalize middle ear
pressure. Stopping compression allows time for equalization. Continuing compression can cause
barotrauma. Patient coaching is essential.
5. HBOT treatment for exceptional blood loss anemia (EBLA) should occur:
A. Once daily
B. Every 48 hours
C. As often as necessary to reduce hypoxia symptoms
D. Only after transfusion
Answer: C. As often as necessary to reduce hypoxia symptoms
Explanation: EBLA compromises oxygen delivery due to low hemoglobin. HBO increases
dissolved oxygen in plasma. Treatments are based on symptom severity, not a fixed schedule.
This supports tissue oxygenation until recovery.
6. The UHMS guidelines primarily address:
A. Diving safety regulations
B. Chamber construction standards
C. Clinical practice of hyperbaric medicine
D. Military decompression tables
Answer: C. Clinical practice of hyperbaric medicine
Explanation: UHMS guidelines define approved clinical indications for HBO therapy. They are
evidence-based and widely accepted. These guidelines help standardize patient care. They do not
regulate chamber construction or military diving.
7. Which topical agent is recommended instead of mafenide acetate during HBO therapy?
A. Bacitracin
B. Betadine
C. Silvadene
D. Neosporin
Answer: C. Silvadene
Explanation: Mafenide acetate can interfere with oxygen delivery. Silvadene provides
antimicrobial coverage without affecting HBO therapy. It is safer for patients receiving
hyperbaric treatments. This substitution reduces complications.
8. The development of staged decompression was commissioned by the British Royal Navy
in the:
A. Late 1800s
B. Early 1900s
C. 1940s
D. 1970s
Answer: B. Early 1900s
Explanation: Early decompression research focused on preventing decompression sickness in
naval divers. The British Royal Navy led these efforts. Their work established staged ascent
procedures. These principles are still used today.
, 9. Mechanical compression of bubbles during HBO treatment for DCS theoretically:
A. Eliminates oxygen toxicity
B. Forces nitrogen back into solution
C. Increases embolism size
D. Stops circulation
Answer: B. Forces nitrogen back into solution
Explanation: Increased pressure reduces bubble size according to Boyle’s law. This forces
nitrogen back into solution. Reduced bubble size improves blood flow. HBO also accelerates
inert gas elimination.
10. Which of the following is NOT a system that allows humans to breathe air underwater?
A. SCUBA
B. Surface-supplied air
C. Pressurized habitat
D. Air balloons
Answer: D. Air balloons
Explanation: Valid underwater breathing systems include SCUBA and surface-supplied air.
Pressurized habitats also allow breathing underwater. Air balloons do not provide controlled
respiration. They are not a diving system.
11. Tissue damage caused by radiation usually requires exposure exceeding:
A. 1000 cGy
B. 3000 cGy
C. 5000 cGy
D. 800 cGy
Answer: C. 5000 cGy
Explanation: Radiation injury occurs when cellular repair mechanisms fail. Doses above 5000
cGy commonly cause tissue necrosis. HBO promotes angiogenesis in damaged tissue. This
improves wound healing.
12. To convert ATA to mmHg, you should:
A. Divide by 760
B. Multiply by 760
C. Multiply by 33
D. Add 14.7
Answer: B. Multiply by 760
Explanation: One atmosphere absolute equals 760 mmHg. Multiplication converts ATA to
mmHg. This conversion is essential in gas calculations. Accurate pressure measurement is
critical in HBO.
13. To convert ATA to PSI, you should:
A. Multiply by 33
B. Divide by 14.7
C. Subtract 1 then multiply by 14.7
D. Add 760
Answer: C. Subtract 1 then multiply by 14.7
EXAM PRACTICE QUESTIONSWITH CORRECT
ANSWERS & EXPLANATIONS
1. The term “ascent” means:
A. Increase in pressure
B. Decrease in pressure (decompression)
C. Constant ambient pressure
D. Oxygen toxicity
Answer: B. Decrease in pressure (decompression)
Explanation: Ascent refers to movement toward a lower pressure environment. In hyperbaric
and diving medicine, ascent results in decreasing ambient pressure. This pressure reduction
allows gases to come out of solution. Controlled ascent is critical to prevent decompression
sickness.
2. Which toxin produced by Clostridium perfringens is affected by hyperbaric oxygen
therapy?
A. Beta toxin
B. Gamma toxin
C. Alpha toxin
D. Theta toxin
Answer: C. Alpha toxin
Explanation: Alpha toxin is responsible for tissue destruction and hemolysis in gas gangrene.
Hyperbaric oxygen inhibits the production of this toxin. HBO also suppresses bacterial growth
and improves leukocyte function. This makes HBO an important adjunctive therapy.
3. The appropriate treatment for a hypoglycemic reaction is:
A. Administer insulin
B. Increase oxygen pressure
C. Feed the patient if conscious
D. Begin chamber decompression
Answer: C. Feed the patient if conscious
Explanation: Hypoglycemia requires prompt correction with glucose. If the patient is conscious
and able to swallow, oral carbohydrates are preferred. This prevents neurological damage.
Unconscious patients require IV glucose.
4. The proper response to complaints of ear pain during pressurization is to:
A. Continue compression
B. Increase compression rate
C. Stop compressing the chamber
,D. Decompress immediately
Answer: C. Stop compressing the chamber
Explanation: Ear pain during compression usually indicates failure to equalize middle ear
pressure. Stopping compression allows time for equalization. Continuing compression can cause
barotrauma. Patient coaching is essential.
5. HBOT treatment for exceptional blood loss anemia (EBLA) should occur:
A. Once daily
B. Every 48 hours
C. As often as necessary to reduce hypoxia symptoms
D. Only after transfusion
Answer: C. As often as necessary to reduce hypoxia symptoms
Explanation: EBLA compromises oxygen delivery due to low hemoglobin. HBO increases
dissolved oxygen in plasma. Treatments are based on symptom severity, not a fixed schedule.
This supports tissue oxygenation until recovery.
6. The UHMS guidelines primarily address:
A. Diving safety regulations
B. Chamber construction standards
C. Clinical practice of hyperbaric medicine
D. Military decompression tables
Answer: C. Clinical practice of hyperbaric medicine
Explanation: UHMS guidelines define approved clinical indications for HBO therapy. They are
evidence-based and widely accepted. These guidelines help standardize patient care. They do not
regulate chamber construction or military diving.
7. Which topical agent is recommended instead of mafenide acetate during HBO therapy?
A. Bacitracin
B. Betadine
C. Silvadene
D. Neosporin
Answer: C. Silvadene
Explanation: Mafenide acetate can interfere with oxygen delivery. Silvadene provides
antimicrobial coverage without affecting HBO therapy. It is safer for patients receiving
hyperbaric treatments. This substitution reduces complications.
8. The development of staged decompression was commissioned by the British Royal Navy
in the:
A. Late 1800s
B. Early 1900s
C. 1940s
D. 1970s
Answer: B. Early 1900s
Explanation: Early decompression research focused on preventing decompression sickness in
naval divers. The British Royal Navy led these efforts. Their work established staged ascent
procedures. These principles are still used today.
, 9. Mechanical compression of bubbles during HBO treatment for DCS theoretically:
A. Eliminates oxygen toxicity
B. Forces nitrogen back into solution
C. Increases embolism size
D. Stops circulation
Answer: B. Forces nitrogen back into solution
Explanation: Increased pressure reduces bubble size according to Boyle’s law. This forces
nitrogen back into solution. Reduced bubble size improves blood flow. HBO also accelerates
inert gas elimination.
10. Which of the following is NOT a system that allows humans to breathe air underwater?
A. SCUBA
B. Surface-supplied air
C. Pressurized habitat
D. Air balloons
Answer: D. Air balloons
Explanation: Valid underwater breathing systems include SCUBA and surface-supplied air.
Pressurized habitats also allow breathing underwater. Air balloons do not provide controlled
respiration. They are not a diving system.
11. Tissue damage caused by radiation usually requires exposure exceeding:
A. 1000 cGy
B. 3000 cGy
C. 5000 cGy
D. 800 cGy
Answer: C. 5000 cGy
Explanation: Radiation injury occurs when cellular repair mechanisms fail. Doses above 5000
cGy commonly cause tissue necrosis. HBO promotes angiogenesis in damaged tissue. This
improves wound healing.
12. To convert ATA to mmHg, you should:
A. Divide by 760
B. Multiply by 760
C. Multiply by 33
D. Add 14.7
Answer: B. Multiply by 760
Explanation: One atmosphere absolute equals 760 mmHg. Multiplication converts ATA to
mmHg. This conversion is essential in gas calculations. Accurate pressure measurement is
critical in HBO.
13. To convert ATA to PSI, you should:
A. Multiply by 33
B. Divide by 14.7
C. Subtract 1 then multiply by 14.7
D. Add 760
Answer: C. Subtract 1 then multiply by 14.7
