Certified Hyperbaric Technologist (CHT) Examination — Questions and Answers

Question 1: Which condition is considered an absolute contraindication to hyperbaric oxygen therapy?

Claustrophobia
Mild anemia
Untreated pneumothorax (Correct answer)
Controlled hypertension

Correct answer: Untreated pneumothorax

Untreated pneumothorax is the only absolute contraindication to HBO therapy because pressurization can cause tension pneumothorax.

Question 2: A balloon holds 10 L at 4 ATA. As it ascends to 1 ATA at constant temperature, what is the final volume?

20 L
40 L (Correct answer)
2.5 L
10 L

Correct answer: 40 L

By Boyle's Law, V2 = (4 x 10)/1 = 40 L.

Question 3: What clothing material is required for patients entering a hyperbaric chamber?

100% cotton (Correct answer)
Wool blend
Nylon
Polyester

Correct answer: 100% cotton

100% cotton is required because synthetic fabrics can generate static electricity and are more flammable in oxygen-enriched atmospheres.

Question 4: Why must temperature be controlled in a hyperbaric chamber?

Henry’s Law
Because of Boyle’s Law
Charles’s Law (Correct answer)
Due to Dalton’s Law

Correct answer: Charles’s Law

Charles’s Law states that for a fixed amount of gas at constant pressure, the volume is directly proportional to its absolute temperature. In a hyperbaric chamber, temperature fluctuations can affect gas volumes and pressures, impacting patient comfort and the precise delivery of therapeutic gases. Therefore, maintaining a stable temperature is essential for accurate and safe treatment delivery.

Question 5: Henry's law is the principle behind which therapeutic effect of HBO?

Mechanical compression of gas bubbles
Refraction of sound under pressure
Conduction of heat in the chamber
Increased oxygen dissolved directly into the blood plasma (Correct answer)

Correct answer: Increased oxygen dissolved directly into the blood plasma

Henry's law states gas dissolved in a liquid is proportional to its partial pressure, allowing far more oxygen to dissolve in plasma under HBO.

Question 6: After completion of hot work near hyperbaric oxygen systems, a fire watch must be maintained for a minimum of:

30 minutes (Correct answer)
Until the work area has fully cooled
15 minutes
60 minutes

Correct answer: 30 minutes

NFPA standards require a minimum 30-minute fire watch after hot work is completed to detect any smoldering that could ignite into a fire after workers leave.

Question 7: When a diver breathes compressed air at depth, which gas primarily dissolves into body tissues and causes decompression sickness risk?

Carbon dioxide
Nitrogen (Correct answer)
Helium
Oxygen

Correct answer: Nitrogen

Inert nitrogen dissolves into tissues under pressure and forms bubbles if ascent is too rapid.

Question 8: Which laboratory or bedside finding suggests a chronic wound is hypoxic and may need HBO2 evaluation?

Persistently low periwound TcPO2 that rises with oxygen challenge (Correct answer)
Elevated serum sodium
High platelet count alone
Normal capillary refill

Correct answer: Persistently low periwound TcPO2 that rises with oxygen challenge

Low TcPO2 that improves with an oxygen challenge indicates correctable tissue hypoxia.

Question 9: If chamber gas is 79% nitrogen at 3 ATA, what is the nitrogen partial pressure?

1.58 ATA
0.79 ATA
3.0 ATA
2.37 ATA (Correct answer)

Correct answer: 2.37 ATA

PN2 = 0.79 x 3 = 2.37 ATA.

Question 10: Visual changes (myopia) experienced by patients after multiple HBO treatments are:

Caused by retinal barotrauma
A sign of immediate CNS oxygen toxicity
Usually reversible within weeks to months after completing therapy (Correct answer)
Permanent and require corrective lens prescription

Correct answer: Usually reversible within weeks to months after completing therapy

HBO-induced myopia results from temporary lens changes and typically resolves within 6–8 weeks after completing treatments.

Question 11: Henry's Law describes which physical phenomenon relevant to hyperbaric therapy?

Light refraction in water
Heat transfer in gases
Amount of gas dissolved in a liquid is proportional to its partial pressure (Correct answer)
Gas volume changes with temperature

Correct answer: Amount of gas dissolved in a liquid is proportional to its partial pressure

Henry's Law states the quantity of gas dissolving in a liquid is proportional to its partial pressure.

Question 12: Dalton's law of partial pressures is most relevant to hyperbaric medicine because it explains:

How each gas in a mixture contributes its own partial pressure (Correct answer)
Why bubbles shrink under pressure
How temperature affects gas volume
How light bends through chamber windows

Correct answer: How each gas in a mixture contributes its own partial pressure

Dalton's law states the total pressure of a gas mixture equals the sum of each gas's partial pressure, key to dosing oxygen.

Question 13: Which symptom indicates possible pulmonary oxygen toxicity (Lorrain Smith effect) in a patient receiving multiple HBO sessions?

Sudden seizure at depth
Joint pain after decompression
Sinus pressure during compression
Substernal chest pain and cough between sessions (Correct answer)

Correct answer: Substernal chest pain and cough between sessions

Substernal burning chest pain and cough are hallmark symptoms of pulmonary oxygen toxicity from cumulative oxygen exposure.

Question 14: At 3 ATA breathing 100% oxygen, dissolved plasma oxygen rises enough to meet resting tissue needs even without hemoglobin. This principle supports treating:

Seasonal allergies
Severe anemia where blood transfusion is not possible (Correct answer)
Routine viral infections
Simple lacerations

Correct answer: Severe anemia where blood transfusion is not possible

HBO can supply tissue oxygen demands via dissolved plasma oxygen, a recognized indication for exceptional blood-loss anemia.

Question 15: A patient taking disulfiram (Antabuse) is scheduled for wound HBO2. The concern is that disulfiram may:

Have no relevance to HBO2
Block superoxide dismutase, impairing protection against oxygen toxicity (Correct answer)
Improve oxygen tolerance
Replace the need for compression

Correct answer: Block superoxide dismutase, impairing protection against oxygen toxicity

Disulfiram inhibits superoxide dismutase, theoretically increasing oxygen-toxicity vulnerability.

Question 16: A wound patient reports ear fullness and pain during compression. The technologist should first:

Immediately abort and decompress rapidly
Increase pressure faster to push through
Ignore it as normal
Slow or halt compression and coach equalization techniques (Correct answer)

Correct answer: Slow or halt compression and coach equalization techniques

Middle-ear barotrauma is managed by pausing compression and coaching equalization (e.g., Valsalva).

Question 17: Which class of drugs lowers the CNS oxygen toxicity threshold when combined with HBO?

Beta blockers
Proton pump inhibitors
Tricyclic antidepressants (Correct answer)
ACE inhibitors

Correct answer: Tricyclic antidepressants

Tricyclic antidepressants lower the seizure threshold and can increase the likelihood of CNS oxygen toxicity during HBO therapy.

Question 18: Which of the following is a sign of middle ear barotrauma in a hyperbaric patient?

Ear pain and hearing loss during compression (Correct answer)
Skin mottling at depth
Nausea only after treatment
Chest tightness during decompression

Correct answer: Ear pain and hearing loss during compression

Middle ear barotrauma presents as ear pain and possible hearing loss during compression when the Eustachian tube fails to equalize pressure.

Question 19: How does the rate of fire spread in a hyperbaric oxygen environment compare to normal atmospheric air?

Faster due to enhanced oxidation at elevated partial pressures (Correct answer)
Unpredictably variable
The same rate
Slower due to increased pressure dampening combustion

Correct answer: Faster due to enhanced oxidation at elevated partial pressures

Elevated oxygen partial pressures accelerate oxidation, causing fires to spread significantly faster than in normal atmospheric air.

Question 20: In a monoplace chamber pressurized with 100% oxygen, how does the patient typically receive their treatment gas?

Through a tight-fitting aviator mask
Through an endotracheal tube only
By breathing the chamber atmosphere directly (Correct answer)
Via a built-in breathing system (BIBS) hood

Correct answer: By breathing the chamber atmosphere directly

In a monoplace oxygen chamber the patient breathes the surrounding 100% oxygen atmosphere directly.

Question 21: What is Dalton's Law of Partial Pressures?

Gas pressure depends only on container size
Gases of different densities separate in a mixture
The total pressure of a gas mixture equals the sum of the partial pressures of each component gas (Correct answer)
All gases exert equal pressure regardless of concentration

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 22: Which law is most directly associated with oxygen toxicity under pressure?

Boyle’s Law
Charles’s Law
Henry’s Law (Correct answer)
Dalton’s Law

Correct answer: Henry’s Law

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. In hyperbaric oxygen therapy, increased ambient pressure leads to more oxygen dissolving into the blood plasma. While this increased dissolved oxygen is therapeutic, excessively high partial pressures can lead to oxygen toxicity, making Henry's Law crucial for understanding this risk.

Question 23: A patient with a history of seizures is being treated. Which monitoring priority is most important?

Watching for early CNS oxygen toxicity signs (Correct answer)
Measuring urine output hourly
Checking pupil size every minute
Recording chamber humidity continuously

Correct answer: Watching for early CNS oxygen toxicity signs

Seizure-prone patients are at higher risk for oxygen-induced seizures, so early CNS toxicity monitoring is critical.

Question 24: What pre-treatment checks must a hyperbaric technologist perform before each treatment?

Verifying the chamber was used within the last week
Chamber integrity inspection, life support systems verification, fire suppression readiness, and communication systems test (Correct answer)
Reviewing the patient's insurance information
Only checking the patient's vital signs

Correct answer: Chamber integrity inspection, life support systems verification, fire suppression readiness, and communication systems test

Pre-treatment checks include chamber structural inspection, oxygen and air supply verification, BIBS function testing, fire suppression system check, communication system verification, emergency decompression readiness, and life support equipment calibration.

Question 25: In air (21% oxygen) at 3 ATA, what is the approximate partial pressure of oxygen?

1.0 ATA
0.63 ATA (Correct answer)
3.0 ATA
0.21 ATA

Correct answer: 0.63 ATA

Partial pressure equals fraction times total pressure: 0.21 multiplied by 3 ATA equals 0.63 ATA.

Question 26: Water vapor pressure in the alveoli (about 47 mmHg at body temperature) must be subtracted when calculating what?

Gauge pressure
Inspired or alveolar gas partial pressures (Correct answer)
Total chamber pressure
Gas molecular weight

Correct answer: Inspired or alveolar gas partial pressures

Alveolar gas calculations subtract water vapor pressure because inspired air becomes fully humidified in the lungs.

Question 27: During a hyperbaric treatment the chamber loses external power. The technologist should be prepared to:

Wait for power without intervention
Switch to backup/manual control and continue a controlled treatment or decompression (Correct answer)
Immediately blow the chamber to surface
Abandon the patient and evacuate

Correct answer: Switch to backup/manual control and continue a controlled treatment or decompression

Chambers have manual backup controls so a controlled decompression can continue safely during a power failure.

Question 28: Which of the following personal care products is specifically prohibited before hyperbaric treatment?

Water-based lubricating eye drops
Unscented cotton bandages
Saline wound rinse
Hair spray and petroleum-based lotions (Correct answer)

Correct answer: Hair spray and petroleum-based lotions

Hair spray and petroleum-based lotions are flammable and prohibited because they increase fire risk in the oxygen-enriched chamber environment.

Question 29: What is the purpose of the pressurization (compression) phase in hyperbaric treatment?

To remove oxygen from the chamber
To cool down the chamber temperature
To test the chamber for leaks
To gradually increase chamber pressure to the prescribed treatment depth while allowing the patient to equalize (Correct answer)

Correct answer: To gradually increase chamber pressure to the prescribed treatment depth while allowing the patient to equalize

Compression gradually increases chamber pressure to the prescribed depth at a controlled rate (typically 1-3 psi/minute), allowing patients to equalize middle ear and sinus pressures through swallowing, jaw movement, or Valsalva maneuver.

Question 30: How does hyperbaric oxygen therapy enhance the action of antibiotics such as aminoglycosides?

HBO directly kills bacteria without antibiotic assistance
HBO raises chamber temperature, activating antibiotic molecules
HBO reduces kidney clearance, increasing antibiotic serum levels
HBO increases oxygen tension in tissue, restoring the oxygen-dependent transport needed for antibiotic uptake (Correct answer)

Correct answer: HBO increases oxygen tension in tissue, restoring the oxygen-dependent transport needed for antibiotic uptake

Aminoglycosides require oxygen-dependent active transport into bacteria; HBO restores this mechanism in hypoxic infected tissue.

Question 31: HBO therapy promotes angiogenesis in chronic wounds primarily through:

Direct mechanical pressure stretching capillary walls
Stimulating hypoxia-inducible factor (HIF) pathways during the post-treatment normoxic period (Correct answer)
Nitrogen supersaturation promoting vessel growth
Reducing inflammatory cytokines that inhibit vascular growth

Correct answer: Stimulating hypoxia-inducible factor (HIF) pathways during the post-treatment normoxic period

The oscillation between hyperoxia during treatment and relative hypoxia between sessions activates HIF-1α, driving VEGF-mediated angiogenesis.

Question 32: What is the mechanism by which HBO helps treat carbon monoxide poisoning?

It converts carboxyhemoglobin directly to oxyhemoglobin through chamber pressure
It replaces red blood cells damaged by CO exposure
It accelerates dissociation of CO from hemoglobin by increasing dissolved oxygen (Correct answer)
It neutralizes CO molecules in the bloodstream chemically

Correct answer: It accelerates dissociation of CO from hemoglobin by increasing dissolved oxygen

At 3 ATA with 100% O2, the half-life of CO-Hb is reduced from ~5 hours (room air) to ~20 minutes by competitively displacing CO.

Question 33: Type I decompression sickness (DCS) is characterized by:

Pulmonary over-inflation and pneumothorax only
Joint pain, skin mottling, or lymphatic symptoms without neurological involvement (Correct answer)
Arterial gas embolism with retinal involvement
Paralysis, unconsciousness, or cardiopulmonary compromise

Correct answer: Joint pain, skin mottling, or lymphatic symptoms without neurological involvement

Type I DCS involves musculoskeletal, skin, and lymphatic symptoms; Type II involves more serious neurological or cardiopulmonary manifestations.

Question 34: What is the function of a chamber's overboard dump (exhaust) system?

Add humidity to the chamber
Pressurize the chamber faster
Vent exhaled oxygen safely outside to prevent buildup (Correct answer)
Filter incoming air

Correct answer: Vent exhaled oxygen safely outside to prevent buildup

The overboard dump routes exhaled oxygen from BIBS masks outside the chamber to avoid oxygen accumulation.

Question 35: The 'hot work permit' protocol in hyperbaric facilities is required before:

Heating blankets for patient comfort
Welding, cutting, or grinding near oxygen systems (Correct answer)
Running high-temperature autoclaves nearby
Treating patients with burns

Correct answer: Welding, cutting, or grinding near oxygen systems

Hot work permits are required before welding, cutting, or grinding near hyperbaric oxygen systems because these activities generate sparks near flammable oxygen-rich environments.

Question 36: Oxygen toxicity risk in hyperbaric therapy is driven primarily by which factor?

Inspired oxygen partial pressure and exposure time (Correct answer)
Total chamber volume
Nitrogen molecular weight
Ambient temperature

Correct answer: Inspired oxygen partial pressure and exposure time

Oxygen toxicity depends on the oxygen partial pressure and duration of exposure, not the percentage alone.

Question 37: Repeated daily HBO2 sessions improve wound bed quality largely by establishing:

A durable oxygen gradient that drives fibroblast and capillary growth over weeks (Correct answer)
Instant complete closure after one dive
Permanent saturation that never declines
A bacterial biofilm protective layer

Correct answer: A durable oxygen gradient that drives fibroblast and capillary growth over weeks

Cumulative daily exposures build a lasting oxygen gradient supporting fibroblast and capillary proliferation.

Question 38: After any significant in-chamber emergency, the appropriate final step for the technologist is to:

Disable the safety systems for convenience
Immediately restart treatment without inspection
Discard all records to reduce liability
Document the event thoroughly and report it per facility safety protocol (Correct answer)

Correct answer: Document the event thoroughly and report it per facility safety protocol

Accurate documentation and reporting support patient safety, equipment inspection, and quality improvement.

Question 39: Static electricity buildup in hyperbaric chambers can best be reduced by:

Using synthetic materials for patient gowns
Using plastic medical equipment inside the chamber
Grounding the patient and chamber to a common reference point (Correct answer)
Increasing treatment pressure

Correct answer: Grounding the patient and chamber to a common reference point

Proper grounding of the patient and chamber to a common electrical reference dissipates static charge before it can create an ignition spark.

Question 40: What temperature change occurs inside a chamber during decompression?

No change occurs
Temperature cools due to gas expansion (Correct answer)
Temperature becomes unstable then doubles
Temperature rises sharply

Correct answer: Temperature cools due to gas expansion

Expanding gas during decompression absorbs energy, cooling the chamber atmosphere.

Question 41: What is the significance of 1.3 ATA in hyperbaric medicine?

It is the standard pressure for all treatments
It has no special significance
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

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.

Question 42: What is the partial pressure of oxygen when breathing 100% oxygen at 2.4 ATA?

0.21 ATA
2.4 ATA (Correct answer)
4.8 ATA
1.0 ATA

Correct answer: 2.4 ATA

With 100% oxygen the partial pressure equals the total pressure, so it is 2.4 ATA.

Question 43: When a patient must wear a hospital gown inside a monoplace hyperbaric chamber, the gown should be:

Laundered with standard fabric softener to reduce static
100% cotton without any synthetic fabric or dyes (Correct answer)
Any color as long as it is clean
Flame-retardant treated polyester

Correct answer: 100% cotton without any synthetic fabric or dyes

Gowns must be 100% cotton without synthetic additives because cotton minimizes static buildup and is less flammable than synthetic materials in the oxygen-pressurized chamber.

Question 44: Before each wound-care dive, blood glucose monitoring is important in diabetic patients because HBO2 can:

Have no effect on glucose
Lower blood glucose and precipitate hypoglycemia (Correct answer)
Permanently cure diabetes
Raise glucose to dangerous highs

Correct answer: Lower blood glucose and precipitate hypoglycemia

HBO2 tends to lower blood glucose, so pre- and post-dive monitoring prevents hypoglycemia.

Question 45: In a chronic refractory wound, HBO2 is best described as:

A purely diagnostic procedure
Adjunctive therapy combined with standard wound care (Correct answer)
Effective only for acute trauma
A standalone cure replacing debridement and offloading

Correct answer: Adjunctive therapy combined with standard wound care

HBO2 is adjunctive and must accompany debridement, offloading, infection control, and good wound care.

Question 46: As ambient pressure increases, what happens to the density of breathing gas?

Density increases (Correct answer)
Density stays constant
Density decreases
Density becomes zero

Correct answer: Density increases

Higher pressure packs gas molecules closer together, increasing gas density.

Question 47: If a fire ignites inside a monoplace hyperbaric chamber during a treatment, what is the FIRST priority action?

Call the fire department
Have the patient attempt to extinguish the flame
Begin immediate emergency decompression (Correct answer)
Activate the external fire suppression system

Correct answer: Begin immediate emergency decompression

Immediate emergency decompression is the first priority to rapidly reduce the oxygen-enriched atmosphere and allow the patient to exit the chamber.

Question 48: What is the primary purpose of a built-in breathing system (BIBS) in a multiplace chamber?

Provide emergency lighting
Cool the chamber atmosphere
Deliver 100% oxygen to the patient while the chamber is air-pressurized (Correct answer)
Equalize ear pressure automatically

Correct answer: Deliver 100% oxygen to the patient while the chamber is air-pressurized

BIBS masks deliver treatment oxygen to patients while the multiplace chamber itself remains pressurized with air.

Question 49: Before a patient is cleared for HBO therapy, a pre-treatment assessment must include:

Only a signed consent form
Medical history, physical exam, contraindication screening, and physician order (Correct answer)
A blood oxygen saturation reading at rest only
Insurance pre-authorization only

Correct answer: Medical history, physical exam, contraindication screening, and physician order

Thorough pre-treatment screening identifies contraindications and optimizes patient safety before initiating hyperbaric treatment.

Question 50: Which NFPA standard is the primary reference for fire safety requirements in hyperbaric facilities?

NFPA 99 (Health Care Facilities Code) (Correct answer)
NFPA 101 (Life Safety Code)
NFPA 13 (Sprinkler Systems)
NFPA 70 (National Electrical Code)

Correct answer: NFPA 99 (Health Care Facilities Code)

NFPA 99, the Health Care Facilities Code, specifically addresses hyperbaric chamber safety requirements including fire prevention, suppression, and equipment standards.

Question 51: Why must IV fluid bags be vented or use special administration sets during hyperbaric treatment?

They will freeze
Pressure changes affect gas in the bag and alter flow rates (Correct answer)
Oxygen destroys the plastic
They become radioactive

Correct answer: Pressure changes affect gas in the bag and alter flow rates

Air in IV bags compresses and expands with pressure, so venting maintains accurate, safe fluid delivery.

Question 52: Nitroglycerin patches worn during HBO present what risk?

They interact with HBO to cause severe hypotension
They may ignite or burn in the oxygen-enriched atmosphere (Correct answer)
They absorb excess oxygen, reducing therapeutic benefit
They are impermeable under pressure and deliver no medication

Correct answer: They may ignite or burn in the oxygen-enriched atmosphere

Transdermal nitroglycerin patches contain flammable materials and must be removed before HBO to prevent fire risk in the oxygen-enriched environment.

Question 53: Antineoplastic drug doxorubicin (Adriamycin) is a relative contraindication to HBO because:

It inactivates the enzymes that metabolize oxygen radicals
It sequesters in fatty tissue and is released dangerously under pressure
It causes cardiac dysrhythmias specifically triggered by hyperoxia
It acts as a free radical generator that synergizes with oxygen toxicity in the lungs (Correct answer)

Correct answer: It acts as a free radical generator that synergizes with oxygen toxicity in the lungs

Doxorubicin generates reactive oxygen species, and combined with hyperbaric oxygen, the cumulative free radical load can cause severe pulmonary toxicity.

Question 54: When should HBO therapy be discontinued for a non-healing wound?

After exactly 5 treatments regardless of progress
Only when the patient requests to stop
If no measurable wound improvement is observed after 15-20 treatments (Correct answer)
Never — treatment should continue indefinitely

Correct answer: If no measurable wound improvement is observed after 15-20 treatments

If a wound shows no measurable improvement (reduction in size, improved granulation tissue, decreased drainage) after 15-20 treatments, the case should be reviewed, as continuing HBO without demonstrated benefit is not warranted.

Question 55: What distinguishes spinal DCS from AGE clinically?

AGE affects only the lower extremities; DCS affects only the brain
Both have identical onset timing and cannot be clinically distinguished
Spinal DCS typically has a slower onset minutes to hours after surfacing, while AGE presents within seconds to minutes (Correct answer)
Spinal DCS always includes unconsciousness; AGE does not

Correct answer: Spinal DCS typically has a slower onset minutes to hours after surfacing, while AGE presents within seconds to minutes

AGE causes near-immediate neurological deficits due to arterial occlusion; spinal DCS develops more gradually as nitrogen bubbles form in spinal cord tissues.

Question 56: The purpose of oxygen breathing during decompression stops in USN treatment tables is to:

Accelerate inert gas (nitrogen) elimination and reduce total treatment time (Correct answer)
Prevent oxygen toxicity by maintaining high oxygen tension
Neutralize any residual CO from prior treatment
Allow the inside tender to breathe air without decompression obligation

Correct answer: Accelerate inert gas (nitrogen) elimination and reduce total treatment time

Breathing 100% oxygen during decompression stops maximizes the diffusion gradient for nitrogen elimination, shortening the required stop times.

Question 57: Topical oxygen therapy differs from systemic HBO2 wound treatment in that topical oxygen:

Is the standard definition of HBO2
Raises plasma oxygen throughout the body
Applies oxygen only to the wound surface without systemic pressurization (Correct answer)
Pressurizes the whole body to 2.5 ATA

Correct answer: Applies oxygen only to the wound surface without systemic pressurization

Topical oxygen treats only the wound surface and is not equivalent to whole-body hyperbaric oxygen therapy.

Question 58: Why must hollow rigid air spaces in equipment be vented during compression?

To equalize pressure and prevent implosion or damage (Correct answer)
To increase oxygen content
To prevent freezing
To reduce humidity

Correct answer: To equalize pressure and prevent implosion or damage

Rigid air spaces must equalize to avoid pressure-related implosion or barotrauma to equipment.

Question 59: Which cleaning agent is appropriate for use on hyperbaric chamber components and oxygen delivery equipment?

Oxygen-compatible (oxygen-clean) cleaners only (Correct answer)
Any commercial multi-surface cleaner
Petroleum-based solvent degreasers
Standard isopropyl alcohol (70%)

Correct answer: Oxygen-compatible (oxygen-clean) cleaners only

Only oxygen-compatible cleaners may be used because residual petroleum-based or flammable solvents on oxygen system components dramatically increase fire risk.

Question 60: What is the mechanism by which HBO therapy helps treat chronic refractory osteomyelitis?

By directly killing bone cells infected with bacteria
By heating the bone to sterilize the infection
By reducing bone density to allow drainage
By increasing oxygen delivery to infected bone, enhancing antibiotic effectiveness and white blood cell bactericidal activity (Correct answer)

Correct answer: By increasing oxygen delivery to infected bone, enhancing antibiotic effectiveness and white blood cell bactericidal activity

HBO increases oxygen tension in infected bone tissue, which enhances neutrophil killing activity (which requires oxygen), potentiates certain antibiotics, stimulates osteoclast and osteoblast activity, and promotes new bone formation.

Question 61: According to Boyle's Law, what happens to the volume of a fixed mass of gas as pressure increases at constant temperature?

Volume decreases inversely (Correct answer)
Volume doubles
Volume stays the same
Volume increases proportionally

Correct answer: Volume decreases inversely

Boyle's Law states that volume is inversely proportional to pressure at constant temperature.

Question 62: Which of the following best describes the role of the standby/outside technologist during an in-chamber emergency?

Document only after the event ends
Enter the chamber and abandon the controls
Shut down all systems immediately
Operate controls, manage gas and communication, and coordinate the response from outside (Correct answer)

Correct answer: Operate controls, manage gas and communication, and coordinate the response from outside

The outside operator manages the chamber controls, gas supply, and team communication throughout an emergency.

Question 63: Archimedes' principle, relevant to chamber operations, describes which phenomenon?

Light refraction
Heat transfer rate
Buoyant force equal to weight of displaced fluid (Correct answer)
Gas solubility in liquids

Correct answer: Buoyant force equal to weight of displaced fluid

Archimedes' principle states a submerged object experiences buoyant force equal to the displaced fluid's weight.

Question 64: When using absolute temperature in gas law calculations, which scale is required?

Kelvin (Correct answer)
Rankine only
Celsius
Fahrenheit

Correct answer: Kelvin

Gas laws require absolute temperature, measured in Kelvin, to be accurate.

Question 65: Maintaining a controlled, slow ascent rate at the end of treatment primarily helps to prevent:

Hypoglycemia
Ear infection
Oxygen toxicity
Pulmonary barotrauma and decompression issues (Correct answer)

Correct answer: Pulmonary barotrauma and decompression issues

A controlled ascent allows expanding gas to vent safely, preventing lung overexpansion and barotrauma.

Question 66: What is the role of the hyperbaric technician during pressurization?

Monitors chamber pressure and patient safety (Correct answer)
Performs surgical procedures
Administers anesthesia
Adjusts medication doses

Correct answer: Monitors chamber pressure and patient safety

During pressurization, the hyperbaric technician is responsible for meticulously monitoring the chamber's pressure gauges to ensure a controlled and safe ascent to the prescribed treatment depth. Simultaneously, they observe patients for any signs of discomfort, barotrauma, or adverse reactions, ready to intervene or adjust the treatment as needed. This vigilance is crucial for patient safety and effective therapy.

Question 67: What rating must electrical equipment used inside a hyperbaric chamber carry?

Battery-powered rating only
High-voltage industrial rating
Standard commercial grade (UL listed)
Intrinsically safe or explosion-proof rated (Correct answer)

Correct answer: Intrinsically safe or explosion-proof rated

Equipment used inside hyperbaric chambers must be intrinsically safe or explosion-proof to prevent sparks or arcing that could ignite the oxygen-enriched atmosphere.

Question 68: What is the absolute pressure at 66 feet of seawater?

5 ATA
4 ATA
3 ATA (Correct answer)
2 ATA

Correct answer: 3 ATA

66 feet adds 2 atmospheres of water plus 1 atmosphere at surface, equaling 3 ATA.

Question 69: Why are air breaks often incorporated into longer wound-treatment dives?

To cool the chamber down
To reduce the risk of oxygen toxicity while maintaining therapy (Correct answer)
To recharge the patient's hemoglobin
To let the patient eat during treatment

Correct answer: To reduce the risk of oxygen toxicity while maintaining therapy

Periodic air breaks lower cumulative oxygen exposure, reducing toxicity risk during extended protocols.

Question 70: Hyperoxic vasoconstriction is therapeutically useful in edematous wounds because it:

Stops all blood flow permanently
Reduces tissue swelling without causing hypoxia, due to high plasma O2 (Correct answer)
Increases capillary leak
Causes profound tissue ischemia

Correct answer: Reduces tissue swelling without causing hypoxia, due to high plasma O2

HBO2 constricts vessels to cut edema while the high dissolved O2 keeps tissue oxygenated.

Question 71: The Marx protocol for osteoradionecrosis classically combines HBO2 with:

Lifelong oral oxygen tablets
Staged surgical management based on treatment response (Correct answer)
A single dive only
Avoidance of all surgery

Correct answer: Staged surgical management based on treatment response

The Marx protocol stages surgical intervention according to the patient's response to HBO2.

Question 72: What US Navy Treatment Table is most commonly used for decompression sickness?

US Navy Treatment Table 1
US Navy Treatment Table 6 (Correct answer)
US Navy Treatment Table 9
US Navy Treatment Table 3

Correct answer: US Navy Treatment Table 6

US Navy Treatment Table 6 is the most commonly used protocol for treating decompression sickness, starting at 2.8 ATA (60 fsw) with oxygen breathing periods, total treatment time approximately 4 hours 45 minutes.

Question 73: Bleomycin chemotherapy is considered a relative contraindication for HBO because it:

Increases CNS seizure risk at therapeutic pressures
Causes chamber material degradation
Sensitizes the lungs to oxygen toxicity (Correct answer)
Crosses the blood-brain barrier more rapidly under pressure

Correct answer: Sensitizes the lungs to oxygen toxicity

Bleomycin causes pulmonary fibrosis, and HBO can exacerbate this by increasing oxidative stress in already damaged lung tissue.

Question 74: Before a treatment, why must the technologist verify there are no petroleum-based products on the patient?

They are flammable in an oxygen-enriched environment (Correct answer)
They reduce oxygen absorption
They interfere with monitors
They cause ear pain

Correct answer: They are flammable in an oxygen-enriched environment

Petroleum-based lotions, makeup, and hair products are flammable and prohibited near pure oxygen.

Question 75: A scuba diver surfaces too rapidly and develops joint pain and skin mottling. This presentation is consistent with:

Nitrogen narcosis at depth
Carbon monoxide poisoning
Simple muscle strain
Decompression sickness (the bends) (Correct answer)

Correct answer: Decompression sickness (the bends)

Rapid ascent allows dissolved nitrogen to form bubbles in tissues, producing the joint pain and skin signs of DCS.

Question 76: Which item is strictly prohibited inside a monoplace hyperbaric chamber due to fire risk?

100% cotton hospital gown
Petroleum-based lip balm (Correct answer)
Cotton bed linens
Grounded copper bracelet

Correct answer: Petroleum-based lip balm

Petroleum-based products are flammable and forbidden in the oxygen-enriched chamber environment.

Question 77: How does hyperbaric oxygen therapy promote wound healing?

By reducing blood flow to the wound area
By increasing tissue oxygen levels to stimulate angiogenesis, fibroblast proliferation, and white blood cell function (Correct answer)
By physically compressing the wound closed
By killing all bacteria through oxygen toxicity

Correct answer: By increasing tissue oxygen levels to stimulate angiogenesis, fibroblast proliferation, and white blood cell function

HBO therapy dramatically increases dissolved oxygen in plasma, promoting new blood vessel formation (angiogenesis), enhancing fibroblast collagen production, improving neutrophil bacterial killing, and reducing edema through vasoconstriction.

Question 78: What is the gauge pressure at 33 feet of seawater?

0 ATA
3 ATA
1 ATA (Correct answer)
2 ATA

Correct answer: 1 ATA

Gauge pressure excludes the 1 ATA surface pressure, so 33 feet reads 1 ATA gauge.

Question 79: When a patient is receiving HBO for a gas-forming infection, which antibiotic class works synergistically with HBO against Clostridium species?

Macrolides (e.g., azithromycin)
Tetracyclines (e.g., doxycycline)
Fluoroquinolones (e.g., ciprofloxacin)
Penicillins (e.g., ampicillin) (Correct answer)

Correct answer: Penicillins (e.g., ampicillin)

Penicillins are the cornerstone antibiotic against Clostridium; HBO synergizes by creating a high-oxygen environment directly hostile to these anaerobes.

Question 80: Why does a sealed rigid gas cylinder show increased pressure when moved from a cold storage room into a warm chamber?

Boyle's Law
Henry's Law
Gay-Lussac's Law (Correct answer)
Graham's Law

Correct answer: Gay-Lussac's Law

Gay-Lussac's Law states pressure is directly proportional to absolute temperature at constant volume.

Question 81: NFPA 99 classifies hyperbaric chambers into which categories based on size and use?

Level 1, 2, or 3
Class A, B, or C (Correct answer)
Category 1, 2, or 3
Type I, II, or III

Correct answer: Class A, B, or C

NFPA 99 classifies hyperbaric chambers as Class A (multiplace, treating multiple patients) and Class B (monoplace, treating one patient at a time).

Question 82: What is the maximum allowable oxygen concentration inside a Class A (multiplace) hyperbaric chamber atmosphere to minimize fire risk?

21%
50%
30%
23.5% (Correct answer)

Correct answer: 23.5%

Multiplace chamber oxygen should be kept at or below 23.5% to reduce the risk of fire.

Question 83: A patient with a fever before HBO treatment poses an increased risk of which complication?

CNS oxygen toxicity seizure (Correct answer)
Permanent deafness
Middle ear infection only
Reduced wound healing

Correct answer: CNS oxygen toxicity seizure

Fever lowers the seizure threshold, increasing susceptibility to CNS oxygen toxicity, so treatment may be delayed.

Question 84: During decompression (ascent), gas trapped in body cavities will:

Expand (Correct answer)
Liquefy
Stay the same
Contract

Correct answer: Expand

Per Boyle's law, as pressure decreases on ascent, trapped gas volume increases (expands).

Question 85: Why should insulin-dependent diabetics have their insulin dosing evaluated before a course of HBO treatments?

HBO degrades insulin molecules in the bloodstream
HBO enhances glucose uptake and insulin sensitivity, potentially causing hypoglycemia (Correct answer)
HBO accelerates hepatic glucose production
HBO increases glucagon secretion throughout the session

Correct answer: HBO enhances glucose uptake and insulin sensitivity, potentially causing hypoglycemia

HBO increases insulin sensitivity and promotes cellular glucose uptake, which can lower blood glucose significantly in diabetic patients.

Question 86: The term 'ATA' stands for which of the following?

Air Tension Average
Ambient Treatment Atmosphere
Atmospheres Absolute (Correct answer)
Absolute Temperature Adjustment

Correct answer: Atmospheres Absolute

ATA means Atmospheres Absolute, the total pressure including atmospheric pressure.

Question 87: For a patient on the chemotherapy drug doxorubicin, the technologist should be aware that HBO2 may:

Convert it into a wound dressing
Completely neutralize the drug
Potentiate the drug's cytotoxic and cardiotoxic effects (Correct answer)
Have no documented interaction concern

Correct answer: Potentiate the drug's cytotoxic and cardiotoxic effects

Doxorubicin is a recognized HBO2 interaction concern due to enhanced toxicity.

Question 88: Reversible myopia (temporary worsening of nearsightedness) after multiple HBO sessions is attributed to:

Permanent retinal detachment
Increased intracranial pressure
Oxygen-induced changes in the lens of the eye (Correct answer)
Optic nerve transection

Correct answer: Oxygen-induced changes in the lens of the eye

Prolonged HBO can cause reversible lens changes producing transient myopia that usually resolves after treatment ends.

Question 89: Which environmental parameter must be continuously monitored inside an oxygen-rich chamber to prevent fire?

Humidity only
Nitrogen partial pressure
Carbon dioxide only
Oxygen concentration (Correct answer)

Correct answer: Oxygen concentration

Oxygen concentration is monitored because elevated levels dramatically increase fire risk.

Question 90: Which gas law best explains why nitrogen narcosis worsens as a diver or chamber occupant goes deeper?

Graham's Law
Boyle's Law
Henry's Law (Correct answer)
Charles's Law

Correct answer: Henry's Law

Henry's Law states the amount of gas dissolved in tissue rises with partial pressure, increasing nitrogen's narcotic effect.

Question 91: The UHMS-approved indications list is important for hyperbaric facilities because:

It sets the maximum chamber operating pressure allowed by law
It lists only unapproved experimental uses of HBO
It replaces individual physician judgment in all treatment decisions
It defines reimbursable diagnoses and guides clinical decision-making for appropriate HBO use (Correct answer)

Correct answer: It defines reimbursable diagnoses and guides clinical decision-making for appropriate HBO use

The UHMS indication list is used by CMS and insurers for reimbursement eligibility and guides clinicians on evidence-based use of HBO.

Question 92: Why are petroleum-based products strictly prohibited inside hyperbaric chambers?

They damage chamber viewport seals
They are highly flammable in oxygen-enriched environments (Correct answer)
They emit toxic fumes during pressurization
They interfere with pressure gauges

Correct answer: They are highly flammable in oxygen-enriched environments

Petroleum-based products are highly flammable and their ignition risk increases dramatically in the oxygen-enriched atmosphere of a hyperbaric chamber.

Question 93: Which type of fire suppression system is most commonly installed in multiplace hyperbaric chambers?

Dry chemical extinguisher system
Water deluge system (Correct answer)
Halon gas suppression
CO2 total flooding system

Correct answer: Water deluge system

Water deluge systems are preferred in multiplace chambers because they rapidly cool and suppress fires without creating toxic atmospheres harmful to patients and staff inside.

Question 94: Which factor presents the GREATEST increase in fire risk within a hyperbaric chamber?

Increased chamber depth (pressure)
Patient age over 65
Elevated oxygen partial pressure (Correct answer)
Extended treatment duration beyond 90 minutes

Correct answer: Elevated oxygen partial pressure

Elevated oxygen partial pressure is the primary fire risk factor because it dramatically lowers the ignition threshold and accelerates combustion of ordinary materials.

Question 95: Sinus squeeze (sinus barotrauma) is best prevented by:

Administering supplemental nitrogen
Compressing more rapidly to reduce exposure time
Ensuring the patient is free of upper respiratory congestion before treatment (Correct answer)
Having the patient hold their breath during descent

Correct answer: Ensuring the patient is free of upper respiratory congestion before treatment

Sinus barotrauma occurs when blocked sinuses cannot equalize; treating or deferring patients with congestion prevents this complication.

Question 96: What should the technologist do if grounding of the chamber and equipment is found to be inadequate?

Lower the oxygen level only
Increase humidity to compensate
Proceed and monitor closely
Correct the grounding before treatment due to static fire risk (Correct answer)

Correct answer: Correct the grounding before treatment due to static fire risk

Proper grounding dissipates static charge; treatment should not proceed until grounding is verified safe.

Question 97: What is the recommended action if a patient becomes claustrophobic during treatment?

Pause treatment and provide reassurance (Correct answer)
Increase chamber pressure
Ignore the anxiety
Turn off chamber lighting

Correct answer: Pause treatment and provide reassurance

Claustrophobia can be a significant challenge for patients in the confined space of a hyperbaric chamber. If a patient experiences claustrophobia, the recommended action is to pause the treatment and provide reassurance. This allows the patient to regain composure, helps alleviate their anxiety, and ensures their comfort and ability to safely continue the therapy, prioritizing their well-being.

Question 98: Which material is most commonly used for the viewing windows of a monoplace chamber?

Tempered soda-lime glass
Polycarbonate film
Acrylic (PMMA) (Correct answer)
Borosilicate glass

Correct answer: Acrylic (PMMA)

Monoplace chamber shells and windows are typically made of clear acrylic for strength and visibility.

Question 99: Per NFPA 55, bulk oxygen storage cylinders must be kept a minimum of how far from combustible materials?

20 feet (Correct answer)
5 feet
25 feet
10 feet

Correct answer: 20 feet

NFPA 55 requires a minimum separation of 20 feet between bulk oxygen storage and any combustible or flammable materials to reduce fire risk.

Question 100: Dalton's Law of partial pressures states that the total pressure of a gas mixture equals what?

The sum of the partial pressures of each gas (Correct answer)
The product of the gas concentrations
The average of all gas pressures
The pressure of the heaviest gas

Correct answer: The sum of the partial pressures of each gas

Dalton's Law states total pressure equals the sum of each component gas's partial pressure.

Question 101: What is the rationale for using HBO in cyanide poisoning?

HBO increases liver metabolism of cyanide compounds
HBO neutralizes cyanide by oxidizing it to cyanate at high pressure
HBO reverses CN binding to hemoglobin
HBO provides dissolved plasma oxygen that bypasses cytochrome oxidase inhibition by cyanide (Correct answer)

Correct answer: HBO provides dissolved plasma oxygen that bypasses cytochrome oxidase inhibition by cyanide

Since cyanide blocks cytochrome oxidase, dissolved plasma oxygen from HBO can supply tissue needs without passing through the blocked mitochondrial chain.

Question 102: A monoplace hyperbaric chamber primarily uses which gas for pressurization?

Helium-oxygen mixture
Nitrogen-oxygen mixture
100% oxygen (Correct answer)
Air

Correct answer: 100% oxygen

Monoplace chambers are pressurized with 100% oxygen, which is why fire prevention is even more critical in monoplace units than in multiplace chambers.

Question 103: A patient becomes unresponsive at depth with no palpable pulse. After starting CPR, the chamber team should decompress at a rate that:

Matches the original compression rate exactly
Balances rapid access to the patient against the risk of pulmonary barotrauma (Correct answer)
Is as fast as mechanically possible regardless of risk
Holds depth indefinitely

Correct answer: Balances rapid access to the patient against the risk of pulmonary barotrauma

Emergency decompression must be expedited yet controlled to avoid causing barotrauma to occupants.

Question 104: At what minimum oxygen concentration does a hyperbaric environment become significantly more hazardous for fire risk?

23.5% (Correct answer)
25%
21%
28%

Correct answer: 23.5%

NFPA 99 designates 23.5% as the threshold above which an oxygen-enriched atmosphere exists, substantially increasing flammability of materials.

Question 105: What is the most common complication of hyperbaric oxygen therapy?

Arterial gas embolism
Pulmonary barotrauma
CNS oxygen toxicity seizure
Middle ear barotrauma (Correct answer)

Correct answer: Middle ear barotrauma

Middle ear barotrauma is the most common complication of HBO therapy due to Eustachian tube dysfunction during pressurization.

Question 106: A patient inside a monoplace chamber develops a tonic-clonic seizure consistent with CNS oxygen toxicity. What is the FIRST action the technologist should take?

Maintain depth and wait for the seizure to subside before decompressing (Correct answer)
Increase chamber oxygen to saturate tissues
Begin a rapid emergency decompression immediately
Open the chamber door at depth to ventilate

Correct answer: Maintain depth and wait for the seizure to subside before decompressing

Decompressing during the tonic phase risks pulmonary barotrauma and arterial gas embolism, so depth is held until the seizure resolves.

Question 107: Which condition results from a trapped gas pocket expanding in the lungs during rapid ascent?

Pulmonary barotrauma (Correct answer)
Oxygen toxicity
Nitrogen narcosis
Hypercapnia

Correct answer: Pulmonary barotrauma

Boyle's Law expansion of trapped lung gas during ascent can cause pulmonary barotrauma.

Question 108: A wound fails to improve after numerous HBO2 sessions and TcPO2 stays low even in-chamber. This suggests:

More dives will always eventually work
The tissue may be non-responsive, warranting reassessment of the treatment plan (Correct answer)
The chamber pressure is irrelevant
Oxygen has reached toxic wound levels

Correct answer: The tissue may be non-responsive, warranting reassessment of the treatment plan

Persistently low in-chamber TcPO2 with no improvement indicates poor response and the need to reassess.

Question 109: Which combined relationship is expressed by the general gas law equation P1V1/T1 = P2V2/T2?

Only Boyle's Law
Boyle's, Charles's, and Gay-Lussac's Laws combined (Correct answer)
Dalton's and Henry's Laws
Henry's and Graham's Laws

Correct answer: Boyle's, Charles's, and Gay-Lussac's Laws combined

The combined gas law unifies Boyle's, Charles's, and Gay-Lussac's relationships into one equation.

Question 110: Which of the following is considered a potential ignition source inside a hyperbaric chamber?

Distilled water
Cotton patient gown
Static electrical discharge (Correct answer)
Silicone-based sealant

Correct answer: Static electrical discharge

Static electrical discharge can produce sparks capable of igniting flammable materials or gases in an oxygen-enriched hyperbaric atmosphere.

Question 111: A patient on doxorubicin (Adriamycin) chemotherapy requires HBO. What is the primary concern?

Reduced wound healing response
Decreased chamber pressure tolerance
Increased pulmonary oxygen toxicity risk (Correct answer)
Elevated CNS seizure threshold

Correct answer: Increased pulmonary oxygen toxicity risk

Doxorubicin combined with HBO significantly increases the risk of pulmonary oxygen toxicity and is a relative contraindication.

Question 112: As absolute pressure increases, the density of a breathing gas does what?

Becomes zero
Increases proportionally (Correct answer)
Stays constant
Decreases proportionally

Correct answer: Increases proportionally

Gas density rises in direct proportion to absolute pressure, which increases breathing resistance at depth.

Question 113: Hyperbaric oxygen enhances the killing of anaerobic bacteria by:

Activating neutrophil chemotaxis independent of oxygen levels
Reducing nutrient availability in the wound bed
Raising tissue oxygen levels toxic to obligate anaerobes that lack antioxidant enzymes (Correct answer)
Physically crushing bacterial cell walls under pressure

Correct answer: Raising tissue oxygen levels toxic to obligate anaerobes that lack antioxidant enzymes

Obligate anaerobes cannot neutralize reactive oxygen species generated under hyperoxia, making high pO2 directly bactericidal.

Question 114: Why is humidity control important inside hyperbaric chambers?

It changes the oxygen percentage reading to zero
It alters Boyle's law
High humidity affects patient comfort and static while low humidity increases static risk (Correct answer)
It eliminates the need for grounding

Correct answer: High humidity affects patient comfort and static while low humidity increases static risk

Humidity influences patient comfort and static electricity, both relevant to safety in the chamber.

Question 115: A relative contraindication to HBO due to risk of pulmonary oxygen toxicity and air trapping is:

A history of appendectomy
Mild seasonal allergies
Well-controlled hypothyroidism
Severe chronic obstructive pulmonary disease with bleb formation (Correct answer)

Correct answer: Severe chronic obstructive pulmonary disease with bleb formation

Bullous COPD raises the risk of air trapping and barotrauma, making it a relative contraindication requiring caution.

Question 116: In radiation-injured tissue, HBO promotes healing by:

Increasing radiation-damaged cell apoptosis to allow regrowth
Directly destroying residual radiation particles
Stimulating stem cell mobilization and angiogenesis in hypoxic tissue (Correct answer)
Reducing fibrosis by compressing scar tissue under pressure

Correct answer: Stimulating stem cell mobilization and angiogenesis in hypoxic tissue

HBO mobilizes CD34+ stem cells from bone marrow and stimulates VEGF-driven angiogenesis in the hypoxic, avascular post-radiation tissue.

Question 117: The 'air break' technique used during HBO sessions is intended to:

Test patient tolerance to pressure changes
Reduce the risk of oxygen toxicity by interrupting continuous oxygen exposure (Correct answer)
Provide room air to maintain nitrogen balance
Allow chamber pressure to stabilize at depth

Correct answer: Reduce the risk of oxygen toxicity by interrupting continuous oxygen exposure

Air breaks involve breathing room air for short periods to reduce cumulative oxygen dose and lower the risk of pulmonary and CNS toxicity.

Question 118: How does HBO therapy treat decompression sickness (the bends)?

By administering anti-inflammatory medications under pressure
By removing all gas from the blood
By reducing bubble size through increased pressure and promoting inert gas elimination through oxygen breathing (Correct answer)
By lowering the patient's body temperature

Correct answer: By reducing bubble size through increased pressure and promoting inert gas elimination through oxygen breathing

HBO treats DCS by recompression (Boyle's law reduces bubble volume), followed by gradual decompression while breathing 100% oxygen to create a gradient that promotes nitrogen elimination from tissues and bubbles.

Question 119: A patient experiences a tonic-clonic seizure at 2.4 ATA during HBO. The immediate action is to:

Immediately decompress the chamber
Administer anticonvulsants through the chamber port
Increase pressure to abort the seizure
Remove the oxygen mask and protect the airway (Correct answer)

Correct answer: Remove the oxygen mask and protect the airway

Removing the oxygen mask stops further O2 delivery; the seizure typically self-terminates, and rapid decompression during a seizure risks pulmonary barotrauma.

Question 120: A sealed flexible bag holds 6 L of gas at the surface (1 ATA). At 3 ATA in a hyperbaric chamber, what is its approximate volume, assuming constant temperature?

6 L
2 L (Correct answer)
18 L
12 L

Correct answer: 2 L

Boyle's Law gives V2 = (P1V1)/P2 = (1 x 6)/3 = 2 L.

Certified Hyperbaric Technologist (CHT) Examination

The CHT exam, administered by the National Board of Diving and Hyperbaric Medical Technology (NBDHMT), tests competency in hyperbaric oxygen therapy including physiology, gas systems, chamber operations, clinical skills, and infection control. Candidates must demonstrate the knowledge required to safely operate hyperbaric chambers and care for patients undergoing hyperbaric oxygen therapy.

Questions

35 min

Time Limit

70%

To Pass

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