CHT Hyperbaric Chamber Operations & Safety 3 — Questions and Answers
Question 1: What is the maximum allowable oxygen concentration in a multiplace chamber breathing air, per NFPA 99 guidelines?
- 21%
- 23.5% (Correct answer)
- 25%
- 30%
Correct answer: 23.5%
NFPA 99 sets 23.5% as the oxygen-enriched atmosphere threshold; chamber ambient O2 must be maintained below this level to reduce fire risk.
Question 2: A CHT notices the chamber's oxygen analyzer reads 25% during a multiplace treatment. What is the priority action?
- Continue treatment and note the reading in the log
- Increase ventilation rate to purge excess oxygen (Correct answer)
- Immediately abort treatment and evacuate patients
- Switch patients from masks to hood systems
Correct answer: Increase ventilation rate to purge excess oxygen
Elevated chamber O2 above 23.5% creates an oxygen-enriched fire hazard; increasing ventilation to purge excess O2 is the correct first response.
Question 3: Which U.S. Navy Treatment Table is most commonly used for AGE (arterial gas embolism) in a clinical hyperbaric facility?
- Table 5
- Table 6
- Table 6A (Correct answer)
- Table 9
Correct answer: Table 6A
U.S. Navy Treatment Table 6A is the standard table for arterial gas embolism, reaching 60 fsw with oxygen and air breathing cycles.
Question 4: What does the term 'fsw' represent in hyperbaric medicine?
- Feet of salt water — a unit of pressure depth (Correct answer)
- Frequency spectrum width
- Flow standard waveform
- Full surface withdrawal
Correct answer: Feet of salt water — a unit of pressure depth
fsw stands for feet of sea water, a common depth/pressure unit in U.S. hyperbaric practice; 33 fsw = 1 ATA gauge pressure.
Question 5: Why must petroleum-based lubricants NEVER be used on oxygen-system fittings in a hyperbaric chamber?
- They corrode brass fittings at high pressure
- They can ignite explosively when exposed to high-pressure oxygen (Correct answer)
- They outgas and raise chamber CO2 levels
- They degrade the PVHO acrylic viewports
Correct answer: They can ignite explosively when exposed to high-pressure oxygen
Petroleum-based lubricants are highly combustible and can spontaneously ignite upon contact with high-pressure oxygen, causing catastrophic fire or explosion.
Question 6: A hyperbaric technician is logging the treatment profile. Which parameter must be recorded at a minimum every 5 minutes during a dive?
- Patient heart rate
- Chamber depth/pressure (Correct answer)
- Oxygen flow rate
- Ventilation purge volume
Correct answer: Chamber depth/pressure
Chamber depth/pressure is the critical parameter that must be logged at regular intervals (typically every 5 minutes) to create a verifiable treatment record.
Question 7: What is the function of the oxygen flush valve on a monoplace hyperbaric chamber?
- It rapidly increases oxygen flow to compensate for a patient's high consumption
- It purges carbon dioxide buildup from the chamber atmosphere (Correct answer)
- It allows emergency venting of the chamber to surface pressure
- It supplies a burst of O2 to raise chamber pressure quickly during compression
Correct answer: It purges carbon dioxide buildup from the chamber atmosphere
The O2 flush valve on a monoplace chamber continuously replenishes oxygen and removes CO2 accumulation from the patient's exhalation.
CHT Hyperbaric Chamber Operations & Safety 3
What is the maximum allowable oxygen concentration in a multiplace chamber breathing air, per NFPA 99 guidelines?