CHS CHS Decompression Sickness & Diving Medicine 2 — Questions and Answers
Question 1: Which condition is treated with US Navy Treatment Table 5 rather than Table 6?
- Type II DCS with neurological symptoms
- Mild Type I DCS (pain only) that resolves completely with initial oxygen breathing at 60 fsw (Correct answer)
- Arterial gas embolism
- Carbon monoxide poisoning
Correct answer: Mild Type I DCS (pain only) that resolves completely with initial oxygen breathing at 60 fsw
USN TT5 is appropriate for mild Type I DCS (musculoskeletal pain, skin symptoms) that fully resolves during the initial oxygen-breathing period at 60 fsw, indicating a favorable response.
Question 2: A diver reports progressive tingling in both legs after surfacing from a deep dive. This bilateral lower extremity paresthesia most likely indicates what type of DCS?
- Type I DCS (limb pain only)
- Spinal cord DCS (Type II), requiring urgent HBOT (Correct answer)
- Inner ear DCS (vestibular)
- Cutaneous DCS
Correct answer: Spinal cord DCS (Type II), requiring urgent HBOT
Bilateral paresthesias of the lower extremities strongly suggest spinal cord bubble formation affecting the thoracic or lumbar cord, classifying this as Type II (neurological) DCS.
Question 3: What is the maximum delay between DCS symptom onset and first HBOT treatment still considered likely to provide neurological benefit?
- 30 minutes
- 2 hours
- There is no absolute cutoff; treat as soon as possible even if delayed by hours or days (Correct answer)
- 6 hours only
Correct answer: There is no absolute cutoff; treat as soon as possible even if delayed by hours or days
While earlier treatment is always better, HBOT can still provide benefit in DCS even when delayed by 24 hours or more, particularly for neurological symptoms, and should never be withheld solely due to delay.
Question 4: A patient with DCS is being treated with USN TT6 and reports symptom recurrence after initial improvement. What is the appropriate response?
- End the treatment immediately
- Extend the table by adding oxygen breathing periods or repeat TT6 as directed by the physician (Correct answer)
- Switch immediately to TT5
- Ascend the chamber to surface pressure
Correct answer: Extend the table by adding oxygen breathing periods or repeat TT6 as directed by the physician
Symptom recurrence or inadequate resolution during TT6 warrants table extension with additional 20-minute oxygen-breathing periods or repeat treatments under physician direction.
Question 5: Oxygen breathing breaks during USN Treatment Tables are provided to prevent what complication?
- Nitrogen narcosis
- Central nervous system (CNS) oxygen toxicity seizures (Correct answer)
- Decompression sickness from the treatment itself
- Ear barotrauma
Correct answer: Central nervous system (CNS) oxygen toxicity seizures
Air breaks during treatment tables reduce cumulative CNS oxygen exposure, lowering the risk of oxygen toxicity seizures without significantly compromising the treatment's therapeutic effectiveness.
Question 6: What pre-treatment measure should a CHS technologist perform for a diver presenting with AGE before the patient enters the chamber?
- Administer high-flow 100% normobaric oxygen by tight-fitting mask during pre-chamber preparation (Correct answer)
- Give the patient water to drink to rehydrate nitrogen out of tissues
- Apply compression bandages to the extremities
- Restrict oxygen use to prevent further embolism
Correct answer: Administer high-flow 100% normobaric oxygen by tight-fitting mask during pre-chamber preparation
Continuous 100% normobaric oxygen before and during transport accelerates nitrogen washout, reduces bubble size, and maintains cerebral oxygenation while preparing for HBOT.
CHS CHS Decompression Sickness & Diving Medicine 2
Which condition is treated with US Navy Treatment Table 5 rather than Table 6?