Clinical and Technical Skills: Screening, Monitoring and In-Chamber Recognition
This domain tests the hands-on layer of practice: what you assess before pressurization, what you monitor at depth, how devices behave under pressure, and how fast you recognize a deteriorating patient inside the chamber.
Before the first pressurization
- Otoscopy of both ears and a documented ability to equalize. Middle-ear barotrauma is the most common complication of HBO.
- Screen for untreated pneumothorax, recent thoracic surgery, bullous lung disease, implanted devices (confirm the pressure rating with the manufacturer), claustrophobia, pregnancy, uncontrolled seizure disorder, and upper respiratory infection.
- Medication review: disulfiram, doxorubicin, bleomycin, cisplatin, insulin, and beta-blockers that blunt hypoglycemia warning signs.
Devices and numbers under pressure
- Blood pressure cuffs and aneroid gauges read a pressure difference, so a cuff used inside the chamber gives a true reading.
- Pulse oximetry sits near 100% throughout HBO and hides hyperoxia; trends, not single values, carry information.
- Gas-filled spaces shrink by Boyle's law: fill Foley balloons with sterile water, vent IV bags or use pressure infusers, and expect endotracheal tube cuffs and pneumatic garments to need adjustment.
- Blood gas syringes: expel bubbles, cap, and analyze immediately - bubbles shrink under pressure and distort results.
Recognizing trouble early
- CNS oxygen toxicity: perioral or facial twitching, nausea, dizziness, tinnitus, tunnel vision, irritability, then convulsion.
- Hypoglycemia, anxiety and CO2 retention can all mimic oxygen toxicity; check glucose and breathing pattern.
- New chest pain or breathlessness during ascent suggests expanding gas - think pneumothorax.
Worked example
Twenty minutes into the second oxygen period at 2.4 ATA, a patient develops perioral twitching, nausea and tunnel vision. Action: remove the oxygen hood and place the patient on air, notify the physician, protect the patient from injury, time the event, and do not decompress while the patient is convulsing. Once breathing is normal and the neurologic exam is stable, abort or complete the treatment as directed and document the episode.
Traps
- Pushing through ear pain instead of stopping descent; forcing equalization can rupture the tympanic membrane.
- Anchoring on a normal SpO2 and missing clinical deterioration.
- Filling Foley balloons with air, or leaving unvented IV bags that cannot infuse at depth.
- Dismissing chest pain or a new neurologic deficit as anxiety or positioning.