CHT (Hyperbaric) Practice Questions (2026) — Free Sample Questions with Answers

Answer: C

Begin decompression at once to the surface: Decompressing during the seizure risks pulmonary barotrauma and arterial gas embolism because the glottis may be closed.

Give a breath-hold coaching cue and continue: A seizing patient cannot follow instructions, and oxygen must be removed.

Remove the oxygen, protect the patient, hold depth: Correct. Removing the oxygen source (switching to chamber air) ends the stimulus; protect the patient from injury and maintain depth until the seizure ends and breathing is regular, then decompress per protocol.

Increase chamber pressure to stop the seizure: Higher pressure raises the PO2 and worsens CNS oxygen toxicity.

CNS oxygen toxicity seizure: remove O2, protect from injury, do not decompress during the tonic-clonic phase; decompress only once breathing is normal.

Answer: B

79.2 fsw: This multiplies 2.4 × 33, treating absolute pressure as if it were all water pressure and forgetting to subtract the 1 atm at the surface.

46.2 fsw: Correct. Depth = (ATA − 1) × 33 = 1.4 × 33 = 46.2 fsw.

20.6 fsw: 20.6 is the gauge pressure in psi (1.4 × 14.7), not the depth in feet.

33.0 fsw: 33 fsw equals 2.0 ATA, not 2.4 ATA.

fsw = (ATA − 1) × 33; ATA = fsw/33 + 1. One atmosphere = 33 fsw = 14.7 psi = 760 mm Hg.

Answer: B

Petroleum residue lowers gas analyzer accuracy: Analyzer accuracy is not the main concern; the hazard is ignition.

Hydrocarbons can ignite in high-pressure oxygen: Correct. Oils and greases ignite readily in oxygen-enriched, high-pressure conditions, especially with heat from rapid (adiabatic) compression when a valve is opened quickly.

Lubricants block the gas line filters: Filter clogging is a maintenance issue, not the reason for oxygen-clean standards.

Petroleum products corrode brass fittings: Corrosion is not the principal risk; fire is.

Oxygen systems must be oxygen-clean, use only approved lubricants, and valves should be opened slowly to limit heat of compression.

Answer: B

Wait until the ears hurt, then clear them: Waiting for pain means a pressure gradient has already formed; clearing becomes harder.

Clear early and often from the start of compression: Correct. Gentle, frequent equalization (swallowing, yawning, jaw movement or a gentle Valsalva) from the start of compression keeps middle-ear pressure matched.

Equalize only during the return to the surface: Squeeze occurs during compression; on decompression the expanding gas usually vents passively.

Use a forceful Valsalva maneuver held for 10 seconds: Forceful, prolonged Valsalva can injure the inner ear and should be avoided.

Teach patients to equalize gently, early and often during compression and to signal at once if they cannot clear.

Answer: C

33 fsw (2.0 ATA): 33 fsw is not the TT6 treatment depth; it is a common depth for clinical wound-healing protocols.

45 fsw (2.4 ATA): 45 fsw (2.4 ATA) is used for many routine HBOT protocols, not TT6.

60 fsw (2.8 ATA): Correct. Treatment Table 6 begins at 60 fsw (2.8 ATA) with 20-minute oxygen periods separated by 5-minute air breaks, then continues at 30 fsw.

165 fsw (6.0 ATA): 165 fsw is the initial depth of Treatment Table 6A (air/nitrox), not TT6.

USN TT6: oxygen at 60 fsw (2.8 ATA) with air breaks, then 30 fsw (1.9 ATA); it is the standard table for DCS and arterial gas embolism.

Answer: A

An alcohol-free, facility-approved product: Correct. The CHT standards specify alcohol-free approved hand-hygiene products because alcohol residue and vapor are flammable in an oxygen-enriched environment.

A 70% alcohol gel left to dry briefly: Alcohol-based products add flammable vapor and residue near an oxygen-rich atmosphere.

A petroleum-based moisturizing lotion: Petroleum products are prohibited fire hazards and do not provide hand hygiene.

No hand hygiene if gloves are worn: Gloves do not replace hand hygiene before and after patient contact.

In hyperbaric areas, use alcohol-free approved hand-hygiene products and approved disinfectants, mindful of chemical off-gassing in the chamber.