CHS Oxygen Toxicity & Barotrauma Management 2 — Questions and Answers
Question 1: Middle ear squeeze (barotitis media) during HBO therapy is caused by:
- Excessive oxygen delivery to cochlear tissues
- Failure of the Eustachian tube to equalize pressure across the tympanic membrane (Correct answer)
- Air bubble formation in the semicircular canals
- Eustachian tube hypertension from rapid ascent
Correct answer: Failure of the Eustachian tube to equalize pressure across the tympanic membrane
Middle ear squeeze results when the Eustachian tube fails to open and allow pressure equalization, causing the tympanic membrane to deform under increasing chamber pressure.
Question 2: Which equalization technique is generally preferred for patients with difficulty clearing their ears during HBO compression?
- Modified Valsalva (pinch nose and swallow or yawn) (Correct answer)
- Forceful standard Valsalva against a closed airway
- Frenzel maneuver with glottis closure
- Toynbee maneuver with nose pinched and swallowing
Correct answer: Modified Valsalva (pinch nose and swallow or yawn)
The modified Valsalva (pinch nose and gently swallow or yawn) is preferred because it is gentler and reduces the risk of inner ear barotrauma compared to forceful exhalation.
Question 3: Pulmonary barotrauma during ascent in a hyperbaric chamber is most likely when a patient:
- Breathes slowly and deeply throughout ascent
- Holds their breath while the chamber is decompressing (Correct answer)
- Uses a demand valve mask during treatment
- Yawns frequently to equalize ear pressure
Correct answer: Holds their breath while the chamber is decompressing
Breath-holding during decompression traps expanding gas in the lungs with no escape route, risking pulmonary overpressurization injury and arterial gas embolism.
Question 4: Arterial gas embolism (AGE) as a complication of pulmonary overpressurization is the primary treatment:
- 100% normobaric oxygen by non-rebreather mask only
- Immediate recompression to 2.8 ATA with oxygen breathing (USN Table 6) (Correct answer)
- Bed rest, IV hydration, and observation
- Aspirin, anticoagulants, and hyperbaric consultation
Correct answer: Immediate recompression to 2.8 ATA with oxygen breathing (USN Table 6)
AGE requires immediate recompression to physically reduce bubble size and dissolve gas emboli; USN Treatment Table 6 at 2.8 ATA with oxygen is the standard protocol.
Question 5: Which paranasal sinus is most commonly affected by sinus squeeze (sinus barotrauma)?
- Sphenoid sinus
- Ethmoid sinus
- Frontal sinus
- Maxillary sinus (Correct answer)
Correct answer: Maxillary sinus
The maxillary sinuses are most frequently affected by sinus squeeze because of their size and the high prevalence of ostial obstruction from nasal congestion or polyps.
Question 6: Barodontalgia (tooth squeeze) during HBO therapy is most commonly caused by:
- Calcium depletion from tooth enamel under pressure
- Gas trapped beneath dental restorations, in caries, or under crowns (Correct answer)
- Increased pulpal blood flow from vasoconstriction
- Fluoride release from sealants during compression
Correct answer: Gas trapped beneath dental restorations, in caries, or under crowns
Gas pockets trapped within dental defects, restorations, or beneath poorly fitting crowns undergo compression and expansion during pressure changes, causing pain or structural injury.
Question 7: Which condition represents an absolute contraindication to HBO therapy due to significant barotrauma risk?
- Mild well-controlled asthma
- Untreated pneumothorax (Correct answer)
- Mild unilateral conductive hearing loss
- History of childhood otitis media
Correct answer: Untreated pneumothorax
Untreated pneumothorax is an absolute contraindication because pressurization and decompression of trapped pleural air can cause tension pneumothorax or facilitate arterial gas embolism.
CHS Oxygen Toxicity & Barotrauma Management 2
Middle ear squeeze (barotitis media) during HBO therapy is caused by: