Certified Hyperbaric Technologist (CHT) Examination — Questions and Answers

Question 1: What document governs the safe design and construction of pressure vessels for human occupancy (PVHO) in the US?

ASME PVHO-1 (Correct answer)
CMS Conditions of Participation
NFPA 99 Chapter 14
OSHA 29 CFR 1910

Correct answer: ASME PVHO-1

ASME PVHO-1 is the American Society of Mechanical Engineers standard specifically for pressure vessels designed to hold human occupants.

Question 2: In an acute crush injury, early HBO2 is used adjunctively to:

Increase swelling for better perfusion
Reduce edema and combat tissue hypoxia and ischemia-reperfusion injury (Correct answer)
Eliminate the need for antibiotics
Replace surgical fixation of fractures

Correct answer: Reduce edema and combat tissue hypoxia and ischemia-reperfusion injury

HBO2 reduces edema via vasoconstriction while maintaining oxygenation and limiting reperfusion injury.

Question 3: Which gas law explains the mechanical reduction in bubble volume that occurs during hyperbaric oxygen therapy for arterial gas embolism?

Henry's law
Charles's law
Boyle's law (Correct answer)
Dalton's law

Correct answer: Boyle's law

Boyle's law states that gas volume is inversely proportional to pressure, so increasing chamber pressure shrinks intravascular bubbles.

Question 4: Arterial gas embolism (AGE) most commonly occurs as a result of:

Pulmonary over-inflation with gas entering pulmonary veins during ascent (Correct answer)
Oxygen toxicity damaging pulmonary capillaries
Mechanical trauma to a joint space at depth
Nitrogen saturation exceeding tissue absorption limits

Correct answer: Pulmonary over-inflation with gas entering pulmonary veins during ascent

AGE results from pulmonary barotrauma during ascent; ruptured alveoli allow gas to enter pulmonary veins and reach the arterial circulation.

Question 5: A diabetic patient consistently experiences hypoglycemia after HBO treatments. The recommended action is to:

Increase insulin dosing before sessions
Check blood glucose before and after each treatment and coordinate with the treating physician (Correct answer)
Discontinue HBO therapy immediately
Administer glucose only after the session ends

Correct answer: Check blood glucose before and after each treatment and coordinate with the treating physician

HBO can lower blood glucose in diabetics; routine monitoring and physician coordination allow safe continuation of therapy.

Question 6: A patient reports a feeling of fullness and pain in the ears during compression. What is the most appropriate first action?

Stop or slow compression and coach equalization techniques (Correct answer)
Immediately abort and decompress fully
Continue compression to finish quickly
Increase compression rate to push past the discomfort

Correct answer: Stop or slow compression and coach equalization techniques

Halting or slowing compression and coaching maneuvers like swallowing or Valsalva allows middle ear equalization and prevents barotrauma.

Question 7: Compromised skin grafts and flaps benefit from HBO2 because oxygen:

Glues the graft to the wound bed
Prevents all infection without antibiotics
Replaces the need for vascular supply entirely
Supports marginally perfused tissue and reduces ischemia-reperfusion injury (Correct answer)

Correct answer: Supports marginally perfused tissue and reduces ischemia-reperfusion injury

HBO2 salvages compromised grafts/flaps by oxygenating marginal tissue and limiting reperfusion injury.

Question 8: What is the typical material used in the construction of monoplace hyperbaric chambers?

Glass
Plastic composite
Acrylic or steel (Correct answer)
Aluminum

Correct answer: Acrylic or steel

Monoplace hyperbaric chambers are typically constructed from either a clear acrylic cylinder or a robust steel shell with viewports. Acrylic provides excellent visibility and is strong enough for the pressures used, while steel offers superior durability and pressure resistance, especially for higher pressure applications. Both materials ensure the structural integrity and safety of the chamber.

Question 9: Cisplatin (a chemotherapy drug) combined with HBO is concerning because:

It directly inhibits oxygen binding to hemoglobin
It increases the risk of both renal toxicity and ototoxicity under hyperoxic conditions (Correct answer)
It prevents neovascularization stimulated by HBO
It lowers the pressure tolerance of the chamber equipment

Correct answer: It increases the risk of both renal toxicity and ototoxicity under hyperoxic conditions

Cisplatin's nephrotoxic and ototoxic effects can be exacerbated by the oxidative stress associated with HBO therapy.

Question 10: Which law is most directly associated with oxygen toxicity under pressure?

Henry’s Law (Correct answer)
Charles’s Law
Boyle’s Law
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 11: When using absolute temperature in gas law calculations, which scale is required?

Rankine only
Celsius
Fahrenheit
Kelvin (Correct answer)

Correct answer: Kelvin

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

Question 12: Archimedes' principle, relevant to chamber operations, describes which phenomenon?

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

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 13: What condition is HBOT commonly used to treat in diabetic patients?

Diabetic foot ulcers (Correct answer)
Hypoglycemia
Diabetic neuropathy
Diabetic retinopathy

Correct answer: Diabetic foot ulcers

Hyperbaric Oxygen Therapy (HBOT) is commonly used to treat diabetic foot ulcers because it delivers high concentrations of oxygen to compromised tissues. This increased oxygenation promotes wound healing, stimulates new blood vessel formation (angiogenesis), and enhances the body's ability to fight infection. For diabetic patients with poor circulation and chronic non-healing ulcers, HBOT can significantly improve outcomes by addressing the underlying hypoxia.

Question 14: What is 'flying DCS' (altitude DCS)?

DCS triggered by reduced atmospheric pressure during air travel after diving (Correct answer)
DCS limited to military aviators flying combat missions
DCS caused by breathing pressurized cabin air at altitude
Any DCS occurring aboard a pressurized aircraft

Correct answer: DCS triggered by reduced atmospheric pressure during air travel after diving

Flying after diving reduces ambient pressure, decreasing nitrogen solubility and precipitating bubble formation from residual dissolved nitrogen.

Question 15: The Marx protocol for osteoradionecrosis classically combines HBO2 with:

Staged surgical management based on treatment response (Correct answer)
A single dive only
Lifelong oral oxygen tablets
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 16: A patient on doxorubicin (Adriamycin) chemotherapy requires HBO. What is the primary concern?

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

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 17: Increased dissolved oxygen in plasma during HBOT is best explained by which law?

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

Correct answer: Henry's Law

Henry's Law explains greater oxygen partial pressure dissolves more oxygen directly into plasma.

Question 18: At 2 ATA, what is the partial pressure of oxygen in air (21% O2)?

0.21 ATA
2.0 ATA
0.42 ATA (Correct answer)
1.0 ATA

Correct answer: 0.42 ATA

Partial pressure = fraction x total pressure = 0.21 x 2 = 0.42 ATA.

Question 19: Gay-Lussac's Law states that at constant volume, gas pressure is proportional to what?

Surface area
Volume
Absolute temperature (Correct answer)
Gas solubility

Correct answer: Absolute temperature

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

Question 20: HBO therapy promotes angiogenesis in chronic wounds primarily through:

Direct mechanical pressure stretching capillary walls
Nitrogen supersaturation promoting vessel growth
Stimulating hypoxia-inducible factor (HIF) pathways during the post-treatment normoxic period (Correct answer)
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 21: HBO's vasoconstriction effect is clinically useful in which situation?

Reducing edema in crush injuries and compartment syndrome (Correct answer)
Controlling hemorrhage in surgical wounds
Preventing post-treatment hypotension
Lowering systemic blood pressure in hypertensive crisis

Correct answer: Reducing edema in crush injuries and compartment syndrome

HBO-induced vasoconstriction reduces edema and swelling in crush injuries while still delivering adequate oxygen via dissolved plasma O2.

Question 22: What is the most common complication of hyperbaric oxygen therapy?

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

Correct answer: Middle ear barotrauma

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

Question 23: What emergency procedure is used if a fire occurs inside a monoplace hyperbaric chamber?

Increase pressure to suppress the fire
Immediately decompress the chamber and remove the patient (Correct answer)
Seal all vents and wait for the fire to consume available oxygen
Inject water into the chamber

Correct answer: Immediately decompress the chamber and remove the patient

Fire in a monoplace chamber requires immediate decompression per emergency protocol while simultaneously notifying emergency services, as the enriched oxygen environment makes fire extremely dangerous and fast-spreading.

Question 24: Which safety feature is required for all hyperbaric chambers?

Battery backup system
Oxygen analyzer
Fire suppression system (Correct answer)
Ventilation fan

Correct answer: Fire suppression system

Due to the high oxygen concentration and increased pressure within hyperbaric chambers, there is an elevated risk of fire. Therefore, a robust fire suppression system, often involving a water deluge or other non-flammable agents, is a mandatory safety feature. This system is essential to quickly extinguish any potential fires and protect the lives of patients and staff.

Question 25: How does hyperbaric oxygen therapy enhance the action of antibiotics such as aminoglycosides?

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

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 26: Hyperoxia during HBO2 promotes wound healing partly by stimulating which process essential for new tissue?

Lymphatic drainage shutdown
Permanent vasodilation
Angiogenesis and fibroblast collagen synthesis (Correct answer)
Inhibition of growth factors

Correct answer: Angiogenesis and fibroblast collagen synthesis

Elevated oxygen tension drives angiogenesis and supports collagen production by fibroblasts.

Question 27: When a patient is receiving HBO for a gas-forming infection, which antibiotic class works synergistically with HBO against Clostridium species?

Fluoroquinolones (e.g., ciprofloxacin)
Macrolides (e.g., azithromycin)
Tetracyclines (e.g., doxycycline)
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 28: Which factor most commonly impairs chronic wound healing and is targeted by HBO2?

Too much collagen
Local tissue hypoxia (Correct answer)
Overactive angiogenesis
Excess oxygen in the wound bed

Correct answer: Local tissue hypoxia

Persistent local hypoxia stalls healing, and HBO2 directly corrects the oxygen deficit.

Question 29: What is the typical pressure used in hyperbaric oxygen therapy?

0.5 ATA
1.0 ATA
3.5 to 4.0 ATA
2.0 to 2.5 ATA (Correct answer)

Correct answer: 2.0 to 2.5 ATA

The typical pressure range for most hyperbaric oxygen therapy (HBOT) treatments is between 2.0 and 2.5 atmospheres absolute (ATA). This range is considered optimal for achieving significant therapeutic benefits, such as dramatically increasing dissolved oxygen in the blood, while simultaneously minimizing the risks of oxygen toxicity and barotrauma. Adhering to this range ensures both efficacy and patient safety.

Question 30: Why must petroleum-based products be prohibited inside an oxygen-rich monoplace chamber?

They are highly flammable in elevated oxygen (Correct answer)
They interfere with intercom signals
They raise the patient's blood pressure
They damage the acrylic shell

Correct answer: They are highly flammable in elevated oxygen

Petroleum products ignite readily in oxygen-enriched atmospheres, creating a fire hazard.

Question 31: How does the rate of fire spread in a hyperbaric oxygen environment compare to normal atmospheric air?

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

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 32: 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 33: USN Treatment Table 5 is used for:

CO poisoning with mild symptoms
All neurological DCS cases
AGE when Table 6 is unavailable
Mild DCS (Type I) with complete relief within 10 minutes at 60 fsw (Correct answer)

Correct answer: Mild DCS (Type I) with complete relief within 10 minutes at 60 fsw

Table 5 is a shorter table appropriate only when symptoms fully resolve quickly at 60 fsw and the presentation is Type I (non-neurological) DCS.

Question 34: In treating decompression sickness, the U.S. Navy Treatment Table 6 is most commonly initiated at what pressure?

2.8 ATA (60 fsw) (Correct answer)
1.5 ATA (16 fsw)
1.0 ATA (surface)
6.0 ATA (165 fsw)

Correct answer: 2.8 ATA (60 fsw)

Treatment Table 6 begins at 2.8 ATA, equivalent to 60 feet of seawater, on 100% oxygen.

Question 35: What is the primary purpose of a built-in breathing system (BIBS) in a multiplace chamber?

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

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 36: During chamber pressurization, the increase in temperature inside the chamber is caused by which gas law principle?

Dalton's partial pressures
Boyle's law expansion
Adiabatic compression heating (Correct answer)
Henry's law dissolution

Correct answer: Adiabatic compression heating

Compressing the gas rapidly releases heat through adiabatic compression, raising chamber temperature.

Question 37: When documenting a hyperbaric treatment adverse event, the technologist should:

Note the event only in the patient's billing record
Report only to the technologist supervisor without medical director notification
Record the event in the treatment log, complete an incident report, and notify the Medical Director promptly (Correct answer)
Delay documentation until the full course of treatment is completed

Correct answer: Record the event in the treatment log, complete an incident report, and notify the Medical Director promptly

Immediate and complete documentation of adverse events plus Medical Director notification are required for patient safety, quality review, and regulatory compliance.

Question 38: In a multiplace hyperbaric chamber, the inside attendant (tender) must:

Hold a physician's license to legally enter the chamber
Be a patient receiving concurrent HBO treatment
Monitor operations only from the external control panel
Be trained in HBO procedures and first aid and be capable of managing emergencies at pressure (Correct answer)

Correct answer: Be trained in HBO procedures and first aid and be capable of managing emergencies at pressure

Inside tenders must be trained hyperbaric professionals capable of responding to patient emergencies while at treatment pressure.

Question 39: A quality assurance (QA) review in a hyperbaric program should include regular audit of:

Staff scheduling and vacation logs
Vendor invoices for oxygen supply only
Only billing and reimbursement data
Adverse event rates, treatment interruptions, wound healing outcomes, and equipment maintenance compliance (Correct answer)

Correct answer: Adverse event rates, treatment interruptions, wound healing outcomes, and equipment maintenance compliance

Comprehensive QA reviews cover clinical outcomes, safety events, compliance metrics, and equipment records to drive continuous improvement.

Question 40: A patient taking disulfiram (Antabuse) is scheduled for wound HBO2. The concern is that disulfiram may:

Have no relevance to HBO2
Improve oxygen tolerance
Block superoxide dismutase, impairing protection against oxygen toxicity (Correct answer)
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 41: What does Boyle's Law state and how does it apply to hyperbaric medicine?

Gases diffuse from low to high concentration
Gas pressure is directly proportional to temperature
Gas solubility increases with temperature
At constant temperature, gas volume is inversely proportional to pressure — explains barotrauma and why air spaces compress under pressure (Correct answer)

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 42: 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
Graham's Law
Gay-Lussac's Law (Correct answer)

Correct answer: Gay-Lussac's Law

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

Question 43: First aid for a suspected DCS or AGE victim before reaching a recompression chamber includes:

Immediate cold water immersion to slow bubble expansion
Rebreathing into a paper bag to raise CO2
Oral aspirin to prevent clotting around gas bubbles
100% normobaric oxygen, IV fluids, and supine positioning (Correct answer)

Correct answer: 100% normobaric oxygen, IV fluids, and supine positioning

High-flow 100% oxygen accelerates nitrogen washout from bubbles; fluids support circulation; supine positioning prevents orthostatic hypotension.

Question 44: What is Dalton's Law of Partial Pressures?

All gases exert equal pressure regardless of concentration
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)
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 45: If a fire ignites inside a monoplace hyperbaric chamber during a treatment, what is the FIRST priority action?

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

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 46: What role does transcutaneous oxygen measurement (TcPO2) play in HBO therapy?

It assesses tissue oxygenation to predict wound healing potential and patient selection for HBO (Correct answer)
It monitors the patient's blood pressure during treatment
It measures atmospheric oxygen levels in the chamber
It calibrates the oxygen delivery system

Correct answer: It assesses tissue oxygenation to predict wound healing potential and patient selection for HBO

TcPO2 measurements assess the oxygen level at the wound site, helping determine if the tissue is hypoxic and whether HBO therapy can adequately increase oxygen delivery to promote healing, guiding patient selection.

Question 47: The 'chokes' in decompression sickness refers to:

CNS DCS affecting the brainstem respiratory center
Pneumothorax following pulmonary over-inflation
Laryngospasm caused by aspiration during rapid ascent
Pulmonary DCS with chest pain, coughing, and respiratory distress from venous gas emboli in the lungs (Correct answer)

Correct answer: Pulmonary DCS with chest pain, coughing, and respiratory distress from venous gas emboli in the lungs

'Chokes' describes pulmonary venous gas embolism causing impaired gas exchange; it is a serious form of DCS requiring urgent recompression.

Question 48: What temperature change occurs inside a chamber during decompression?

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

Correct answer: Temperature cools due to gas expansion

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

Question 49: The UHMS-approved indications list is important for hyperbaric facilities because:

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

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 50: The primary accreditation body for clinical hyperbaric medicine programs in the United States is:

Joint Commission (TJC)
National Fire Protection Association (NFPA)
Undersea and Hyperbaric Medical Society (UHMS) (Correct answer)
American College of Surgeons (ACS)

Correct answer: Undersea and Hyperbaric Medical Society (UHMS)

UHMS provides the standards and accreditation process specifically designed for clinical hyperbaric medicine facilities in the US.

Question 51: What is the recommended HBO protocol for diabetic foot ulcers?

3.0 ATA for 120 minutes twice weekly
2.0-2.4 ATA for 90 minutes, 5 days per week for 20-40 treatments (Correct answer)
2.0 ATA for 15 minutes once weekly
1.0 ATA for 30 minutes daily

Correct answer: 2.0-2.4 ATA for 90 minutes, 5 days per week for 20-40 treatments

Diabetic foot ulcers typically require treatment at 2.0-2.4 ATA for 90 minutes per session, 5 days per week, with a treatment course of 20-40 sessions depending on wound response.

Question 52: What is the purpose of the pressurization (compression) phase in hyperbaric treatment?

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

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 53: The combined gas law incorporates the relationships among which three variables?

Partial pressure, solubility, depth
Pressure, volume, temperature (Correct answer)
Force, area, time
Mass, volume, density

Correct answer: Pressure, volume, temperature

The combined gas law links pressure, volume, and temperature of a fixed gas mass.

Question 54: Nitroglycerin patches worn during HBO present what risk?

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

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

By directly killing bone cells infected with bacteria
By reducing bone density to allow drainage
By heating the bone to sterilize the infection
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 56: Bleomycin chemotherapy is considered a relative contraindication for HBO because it:

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

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 57: Which condition is considered a contraindication to HBOT?

Radiation injury
Pneumothorax (Correct answer)
Thermal burn
Diabetic foot ulcer

Correct answer: Pneumothorax

An untreated pneumothorax, or collapsed lung, is an absolute contraindication to hyperbaric oxygen therapy. The increased pressure during HBOT could cause the trapped air in the pleural space to expand further upon decompression, according to Boyle's Law. This expansion can lead to a tension pneumothorax, which is a life-threatening condition requiring immediate medical intervention.

Question 58: What does the term 'sea level equivalent' refer to during a hyperbaric treatment?

The maximum patient weight
A reference depth/pressure used to express treatment depth (Correct answer)
The oxygen flow rate
The chamber's altitude rating

Correct answer: A reference depth/pressure used to express treatment depth

Treatment pressures are commonly expressed as a depth equivalent referenced to sea level.

Question 59: Delayed radiation tissue injury such as osteoradionecrosis responds to HBO mainly because the therapy does what?

Eliminates the need for surgical reconstruction
Induces neovascularization in hypoxic irradiated tissue (Correct answer)
Reverses the patient's original malignancy
Removes residual radioactive material

Correct answer: Induces neovascularization in hypoxic irradiated tissue

HBO stimulates neovascularization in the hypocellular, hypovascular, hypoxic tissue characteristic of radiation injury.

Question 60: Which gas law best explains why nitrogen narcosis worsens as a diver or chamber occupant goes deeper?

Charles's Law
Boyle's Law
Henry's Law (Correct answer)
Graham'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 61: At what minimum oxygen concentration does a hyperbaric environment become significantly more hazardous for fire risk?

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

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 62: Which fire-suppression feature is required in most multiplace hyperbaric chambers?

A CO2 flooding system
A dry-chemical extinguisher only
A deluge water spray system (Correct answer)
No system is required

Correct answer: A deluge water spray system

Multiplace chambers are equipped with a deluge water spray system for rapid fire suppression.

Question 63: What clothing material is required for patients entering a hyperbaric chamber?

Nylon
100% cotton (Correct answer)
Polyester
Wool blend

Correct answer: 100% cotton

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

Question 64: 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
Remove the oxygen mask and protect the airway (Correct answer)
Increase pressure to abort the seizure

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 65: Why is fire risk a serious concern in hyperbaric environments?

High humidity ignites materials
Low temperatures cause sparks
Elevated oxygen partial pressure accelerates combustion (Correct answer)
Nitrogen becomes flammable

Correct answer: Elevated oxygen partial pressure accelerates combustion

Higher oxygen partial pressure causes materials to ignite more easily and burn faster.

Question 66: How does hyperbaric oxygen therapy promote wound healing?

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

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

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

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

HBO degrades insulin molecules in the bloodstream
HBO accelerates hepatic glucose production
HBO enhances glucose uptake and insulin sensitivity, potentially causing hypoglycemia (Correct answer)
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 69: Which of the following is an UHMS-approved indication for hyperbaric oxygen therapy?

Chronic fatigue syndrome
Generalized anxiety disorder
Crush injury and acute traumatic ischemia (Correct answer)
Autism spectrum disorder

Correct answer: Crush injury and acute traumatic ischemia

Crush injury and acute traumatic ischemia is an established UHMS-approved indication for adjunctive HBO.

Question 70: Why must compression and decompression rates be controlled rather than rapid?

To allow pressure equalization and prevent barotrauma (Correct answer)
To reduce electricity use
To keep the chamber clean
To save oxygen supply

Correct answer: To allow pressure equalization and prevent barotrauma

Controlled rates allow body air spaces to equalize, preventing barotrauma to ears and sinuses.

Question 71: In radiation-injured tissue, HBO promotes healing by:

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

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 72: A diabetic patient is scheduled for HBO therapy. What is a key pre-treatment safety check?

Withhold all insulin for 24 hours
Skip glucose monitoring entirely
Verify blood glucose level before and after treatment (Correct answer)
Double the morning insulin dose

Correct answer: Verify blood glucose level before and after treatment

HBO can lower blood glucose, so checking levels before and after prevents hypoglycemia during treatment.

Question 73: 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 74: Sinus squeeze (sinus barotrauma) is best prevented by:

Ensuring the patient is free of upper respiratory congestion before treatment (Correct answer)
Compressing more rapidly to reduce exposure time
Administering supplemental nitrogen
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 75: What is the standard operating pressure for most clinical hyperbaric treatments?

0.5 ATA
2.0-3.0 ATA (atmospheres absolute) (Correct answer)
5.0-6.0 ATA
1.0 ATA

Correct answer: 2.0-3.0 ATA (atmospheres absolute)

Most clinical hyperbaric oxygen treatments operate between 2.0-3.0 ATA, with 2.4 ATA being the most common pressure for wound healing and 2.8 ATA used for conditions like carbon monoxide poisoning.

Question 76: Which statement about HBO and anticoagulants (e.g., warfarin) is correct?

Warfarin is an absolute contraindication to HBO
No interaction exists between HBO and anticoagulants
HBO may enhance anticoagulant effects, requiring INR monitoring (Correct answer)
HBO neutralizes anticoagulants, requiring dose increases

Correct answer: HBO may enhance anticoagulant effects, requiring INR monitoring

HBO can affect platelet function and coagulation pathways, necessitating careful INR monitoring in patients on anticoagulants.

Question 77: Which symptom indicates possible pulmonary oxygen toxicity (Lorrain Smith effect) in a patient receiving multiple HBO sessions?

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

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 78: Necrotizing soft tissue infection treated with HBO2 benefits because elevated oxygen tension:

Lowers tissue oxygen further
Replaces emergency surgical debridement
Is bactericidal/bacteriostatic to anaerobes and supports host defenses (Correct answer)
Feeds anaerobic bacteria

Correct answer: Is bactericidal/bacteriostatic to anaerobes and supports host defenses

High oxygen inhibits anaerobes and enhances leukocyte and antibiotic activity in necrotizing infections.

Question 79: What distinguishes spinal DCS from AGE clinically?

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

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 80: Which physiologic mechanism most directly explains how HBO2 therapy improves healing in a hypoxic wound?

Increased dissolved oxygen in plasma driving diffusion into ischemic tissue (Correct answer)
Stimulation of red blood cell agglutination
Direct antibiotic delivery to bacteria
Reduced systemic blood pressure

Correct answer: Increased dissolved oxygen in plasma driving diffusion into ischemic tissue

HBO2 dramatically raises plasma-dissolved oxygen, steepening the diffusion gradient into hypoxic tissue.

Question 81: The 'D10' endpoint in DCS treatment refers to:

No residual symptoms at the end of the hyperbaric treatment table (Correct answer)
10 minutes of oxygen breathing at final decompression stop
Reduction of symptoms by at least 10% over baseline
Completion of 10 consecutive treatment sessions

Correct answer: No residual symptoms at the end of the hyperbaric treatment table

The treatment goal is complete symptom resolution; 'D10' is shorthand for the desired endpoint of total clinical resolution before surfacing.

Question 82: 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 83: Why are air breaks often incorporated into longer wound-treatment dives?

To recharge the patient's hemoglobin
To reduce the risk of oxygen toxicity while maintaining therapy (Correct answer)
To cool the chamber down
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 84: 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 average of the individual gas pressures
The product of the individual gas pressures
The pressure of the most abundant gas

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

Dalton's Law: total pressure is the sum of each gas's partial pressure.

Question 85: Which statement about methylprednisolone and HBO therapy is most accurate?

Steroids increase the effectiveness of HBO at lower pressures
Corticosteroids are required to prevent oxygen toxicity during HBO
Corticosteroids may blunt the angiogenic and wound healing benefits of HBO (Correct answer)
No clinically relevant interaction exists between corticosteroids and HBO

Correct answer: Corticosteroids may blunt the angiogenic and wound healing benefits of HBO

Corticosteroids suppress inflammation and may impair the fibroblast proliferation and angiogenesis that HBO therapy aims to promote.

Question 86: Which medication taken by a patient increases the risk of CNS oxygen toxicity during HBO?

Atorvastatin
Disulfiram (Antabuse) (Correct answer)
Metformin
Lisinopril

Correct answer: Disulfiram (Antabuse)

Disulfiram lowers the seizure threshold and is associated with increased CNS oxygen toxicity risk during HBO therapy.

Question 87: As ambient pressure increases, what happens to the density of breathing gas?

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

Correct answer: Density increases

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

Question 88: Which type of hyperbaric chamber allows multiple patients to be treated at once?

Soft chamber
Monoplace chamber
Acrylic chamber
Multiplace chamber (Correct answer)

Correct answer: Multiplace chamber

A multiplace hyperbaric chamber is specifically designed to accommodate several patients simultaneously, along with medical staff. These chambers are typically pressurized with compressed air, and patients breathe 100% oxygen through individual hoods or masks. This setup allows for continuous monitoring and direct intervention by attendants inside the chamber, enhancing patient care and safety.

Question 89: Why are petroleum-based products strictly prohibited inside hyperbaric chambers?

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

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 90: What is the primary reason patients are grounded inside a hyperbaric chamber?

To improve oxygen absorption
To prevent static electricity discharge that could ignite a fire (Correct answer)
To stabilize blood pressure
To reduce claustrophobia

Correct answer: To prevent static electricity discharge that could ignite a fire

Grounding dissipates static charges that could create a spark in the oxygen-rich environment.

Question 91: 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 standard pressure for all treatments
It is the maximum safe treatment pressure
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.

Question 92: When should HBO therapy be discontinued for a non-healing wound?

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

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 93: Which fire-safety practice is essential during wound HBO2 in an oxygen-enriched chamber?

Using only synthetic blankets that spark
Prohibiting petroleum-based products and static-generating materials (Correct answer)
Allowing patients to bring lighters for comfort
Permitting electronic heating pads inside

Correct answer: Prohibiting petroleum-based products and static-generating materials

Oxygen-rich environments demand removal of petroleum products and ignition/static sources to prevent fire.

Question 94: What is the absolute pressure at 66 feet of seawater?

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

Correct answer: 3 ATA

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

Question 95: What happens to gas volume when a patient ascends rapidly from depth?

Volume increases (Correct answer)
Volume evaporates
Volume decreases
Volume stays the same

Correct answer: Volume increases

According to Boyle's Law, as external pressure decreases, the volume of a gas increases. When a patient ascends rapidly from depth, the surrounding pressure drops, causing any gas trapped in body cavities (like lungs, sinuses, or middle ear) to expand. This expansion can lead to barotrauma if not properly managed, highlighting the importance of controlled ascent.

Question 96: Which of the following is a sign of middle ear barotrauma in a hyperbaric patient?

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

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

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

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

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

Question 98: What does Henry's Law state and why is it important in HBO therapy?

Gas temperature determines its solubility
Gases always rise to the surface of liquids
All gases dissolve equally in water
Gas dissolved in a liquid is proportional to the partial pressure of that gas — explains how HBO increases dissolved oxygen in blood (Correct answer)

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 99: Delayed radiation injury (soft tissue radionecrosis) responds to HBO2 primarily because the therapy:

Destroys residual tumor cells
Eliminates the need for surgical debridement
Reverses the original radiation dose
Induces neovascularization in irradiated, hypovascular tissue (Correct answer)

Correct answer: Induces neovascularization in irradiated, hypovascular tissue

HBO2 stimulates angiogenesis in the hypoxic, hypocellular, hypovascular irradiated tissue bed.

Question 100: What is delayed radiation injury and how does HBO therapy treat it?

Immediate skin burns from radiation treatment
Progressive tissue damage from prior radiation therapy, treated by HBO-stimulated angiogenesis in damaged tissue (Correct answer)
Radiation exposure from the hyperbaric chamber
A side effect of HBO therapy itself

Correct answer: Progressive tissue damage from prior radiation therapy, treated by HBO-stimulated angiogenesis in damaged tissue

Delayed radiation injury (osteoradionecrosis, soft tissue radionecrosis) results from progressive vascular damage in previously irradiated tissue. HBO stimulates new blood vessel growth in the damaged tissue, restoring blood supply and healing capacity.

Question 101: Why does HBO2 enhance leukocyte killing of bacteria in an infected wound?

It removes all moisture from the wound
It blocks white cell migration
Oxygen-dependent respiratory burst requires adequate tissue O2 (Correct answer)
It cools the tissue to slow bacteria

Correct answer: Oxygen-dependent respiratory burst requires adequate tissue O2

Neutrophil oxidative (respiratory) burst killing is oxygen-dependent and restored by raising tissue O2.

Question 102: A wound fails to improve after numerous HBO2 sessions and TcPO2 stays low even in-chamber. This suggests:

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

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

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

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 104: Which approved garment material is acceptable for a patient entering the chamber?

100% cotton gown (Correct answer)
Synthetic nylon athletic wear
Wool sweater
Polyester blend pajamas

Correct answer: 100% cotton gown

Only 100% cotton garments are permitted because synthetics can generate static and are more flammable.

Question 105: After a successful Table 6 treatment for DCS, the patient should be advised to:

Avoid flying or diving for a minimum of 72 hours and follow up with a diving physician (Correct answer)
Increase hydration only and return to full activity immediately
Resume normal diving within 24 hours if asymptomatic
Complete 30 days of daily HBO treatments as a follow-up

Correct answer: Avoid flying or diving for a minimum of 72 hours and follow up with a diving physician

Residual microbubbles and tissue injury require adequate surface interval before pressure exposure; 72 hours minimum and physician clearance are standard recommendations.

Question 106: What is the primary physiological effect of hyperbaric oxygen therapy?

Reduces red blood cell count
Increases plasma oxygen concentration (Correct answer)
Reduces heart rate
Increases blood glucose levels

Correct answer: Increases plasma oxygen concentration

The primary physiological effect of hyperbaric oxygen therapy is to significantly increase the partial pressure of oxygen in the blood plasma. Under increased atmospheric pressure, more oxygen dissolves directly into the plasma, allowing it to reach tissues that may be poorly perfused or hypoxic, independent of hemoglobin binding. This enhanced oxygen delivery is central to its therapeutic benefits.

Question 107: Hydration is recommended as an adjunct in DCS treatment primarily because:

It dilutes dissolved nitrogen in the bloodstream directly
It reduces blood viscosity and supports tissue perfusion impaired by gas bubbles (Correct answer)
It counteracts oxygen toxicity at cellular level
It prevents post-recompression seizures

Correct answer: It reduces blood viscosity and supports tissue perfusion impaired by gas bubbles

Adequate hydration combats the hemoconcentration and impaired microcirculation caused by gas bubble-induced vascular injury.

Question 108: What are the symptoms of acute arterial gas embolism (AGE)?

Sudden neurological symptoms (stroke-like), loss of consciousness, or cardiac arrest within minutes of surfacing (Correct answer)
Gradual joint pain developing over 24 hours
Only respiratory symptoms like coughing
Mild skin itching and fatigue

Correct answer: Sudden neurological symptoms (stroke-like), loss of consciousness, or cardiac arrest within minutes of surfacing

AGE presents with sudden, dramatic neurological symptoms (seizures, paralysis, visual disturbances, confusion, loss of consciousness) typically within minutes of surfacing from a dive, caused by gas bubbles entering the arterial circulation.

Question 109: The role of the Hyperbaric Technologist during a monoplace chamber treatment primarily includes:

Performing wound debridement during pressurization
Administering IV medications directly through the chamber hull
Conducting biopsies while the patient is at depth
Monitoring patient condition, managing chamber pressure and gas supply, and responding to emergencies (Correct answer)

Correct answer: Monitoring patient condition, managing chamber pressure and gas supply, and responding to emergencies

The technologist manages all operational aspects of the treatment — pressure, gas supply, patient monitoring — from outside the chamber.

Question 110: Which patient condition would require special attention before hyperbaric treatment?

Sinus congestion (Correct answer)
Mild headache
Muscle soreness
Joint stiffness

Correct answer: Sinus congestion

Sinus congestion requires special attention before hyperbaric treatment because trapped air within congested sinuses can lead to severe pain and barotrauma during changes in chamber pressure. Patients must be able to equalize pressure in their sinuses and ears to prevent injury. Significant congestion may necessitate deferring treatment or using decongestants to ensure safe pressure equalization and prevent complications.

Question 111: In a monoplace chamber pressurized with 100% oxygen, how does the patient typically receive their treatment gas?

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

Correct answer: By breathing the chamber atmosphere directly

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

Question 112: Charles's Law relates gas volume to which variable at constant pressure?

Density
Partial pressure
Mass
Absolute temperature (Correct answer)

Correct answer: Absolute temperature

Charles's Law states gas volume is directly proportional to absolute temperature at constant pressure.

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

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

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: What is the role of HBO in treating gas gangrene (clostridial myonecrosis)?

HBO replaces surgical debridement entirely
HBO inhibits toxin production, kills anaerobic bacteria through oxygen toxicity, and enhances antibiotic effectiveness (Correct answer)
HBO has no effect on gas gangrene
HBO only provides pain relief for gas gangrene

Correct answer: HBO inhibits toxin production, kills anaerobic bacteria through oxygen toxicity, and enhances antibiotic effectiveness

HBO therapy in gas gangrene inhibits alpha-toxin production, is directly bactericidal to Clostridium perfringens (an obligate anaerobe), enhances WBC function, and supports antibiotic therapy, used as an adjunct to surgery.

Question 115: Which of the following is considered a potential ignition source inside a hyperbaric chamber?

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

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 116: What is a critical safety rule for patients before entering a hyperbaric chamber?

Apply lotion before entering
Wear cotton clothes
Keep cell phones on hand
Remove all flammable items (Correct answer)

Correct answer: Remove all flammable items

Hyperbaric chambers operate with high concentrations of oxygen, which significantly increases the risk of fire. Removing all flammable items, including synthetic clothing, electronic devices, and petroleum-based products, is a critical safety rule. This measure is essential to prevent ignition and ensure patient safety in the oxygen-rich environment of the chamber, where even a small spark can lead to a catastrophic fire.

Question 117: Static electricity buildup in hyperbaric chambers can best be reduced by:

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

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 118: Approximately how much does ambient pressure increase for every 33 feet of seawater depth?

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

Correct answer: 1 ATA

Each 33 fsw adds approximately 1 ATA to ambient pressure.

Question 119: How does HBO therapy treat decompression sickness (the bends)?

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 administering anti-inflammatory medications under pressure
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 120: Why does the temperature inside a hyperbaric chamber rise during compression?

Electrical heaters activate
Compression of gas releases heat (adiabatic heating) (Correct answer)
Oxygen reacts with metal
Friction of the door seals

Correct answer: Compression of gas releases heat (adiabatic heating)

Compressing gas rapidly raises its temperature through adiabatic heating.

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.

120

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120 min

Time Limit

70%

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