ABPM Undersea and Hyperbaric Medicine common mistakes
ABPM Undersea and Hyperbaric Medicine · Understand the traps and how to avoid them.
Calculating oxygen partial pressure by multiplying depth in metres by 0.1 and then by FiO2 without adding 1 atm, or switching between msw and fsw mid-calculation.
Gauge depth is not absolute pressure; candidates memorize PO2 = depth × 0.1 × FiO2 and omit the +1 atm conversion.
What to do instead
Convert to ATA first: ATA = depth(msw)/10 + 1 or depth(fsw)/33 + 1; then PO2 = FiO2 × ATA × 1 atm. Write units at every step and back-calculate a known example such as 30 msw on air giving approximately 0.84 atm PO2.
Using ambient pressure or bottom PO2 as the alveolar or inspired oxygen pressure when assessing oxygen toxicity or gas exchange, ignoring water vapour and CO2.
Candidates memorize a single PO2 formula and do not distinguish inspired, alveolar, and arterial oxygen pressures.
What to do instead
Use PIO2 = FiO2 × (PB − 47 mmHg) for inspired gas and state explicitly whether the calculation is inspired, alveolar, or arterial. Do not use depth pressure alone as a surrogate for alveolar PO2.
Continuing descent despite failed ear clearing and then treating persistent ear pain as normal squeeze after surfacing.
Descent urgency and reluctance to abort a dive lead candidates to push through discomfort instead of recognizing barotrauma risk.
What to do instead
Stop descent at the first discomfort, attempt gentle equalization, ascend slightly and retry; abort if the ear does not clear. Examine for middle-ear barotrauma and do not dive with unresolved symptoms.
Diagnosing post-dive pain as just musculoskeletal and delaying recompression while waiting for imaging or giving only analgesics.
Mild symptoms seem benign, imaging may be normal, and candidates underestimate the need for clinical diagnosis of decompression sickness.
What to do instead
Treat suspected DCS clinically: give 100% oxygen, maintain hydration, and arrange urgent hyperbaric consultation and recompression. Do not let imaging or analgesic response delay definitive treatment.
Selecting a hyperbaric treatment table solely by referral diagnosis without considering symptom severity, time to treatment, and the patient’s response during the treatment.
Candidates memorize diagnosis-to-table pairings instead of applying indication-specific protocols and reassessing at depth.
What to do instead
Know the indications and limits of commonly used treatment tables, reassess the patient at depth, and document the rationale for extending, converting, or repeating treatment.
Failing to track cumulative oxygen dose and air breaks during multi-hour hyperbaric oxygen therapy, or continuing oxygen after a seizure without protecting the airway and stopping oxygen.
Attention is focused on chamber pressure and equipment rather than time-dose monitoring and CNS oxygen toxicity management.
What to do instead
Record oxygen periods and air breaks prospectively, recognize early CNS toxicity signs, and manage a seizure by removing oxygen, protecting the patient, and avoiding decompression until it is safe.
Starting compression before confirming chamber atmosphere oxygen is below the facility limit and before completing the pre-compression checklist and communications check.
Routine familiarity and time pressure cause checklist steps to be skipped as formalities.
What to do instead
Use a read-aloud, two-person checklist covering atmosphere analysis, patient and attendant status, communications, door seals, oxygen supply, fire suppression, and the emergency plan before every compression.
Allowing prohibited materials such as petroleum-based ointments, synthetic clothing, electronics, or lighters into the chamber because they are small or requested by the patient.
Candidates underestimate chamber fire risk and prioritize patient comfort over strict material control.
What to do instead
Apply a strict item policy: 100% cotton clothing, no petroleum products, no electronics or ignition sources, and chamber-approved alternatives. Inspect every patient and attendant before entry.
Clearing a diver for work or return to diving after treated DCS or AGE, or with a chronic condition or medication, by relying on the patient feeling fine rather than formal fitness standards.
Desire to return to work and incomplete knowledge of occupational fitness criteria lead to informal clearance.
What to do instead
Use formal fitness-to-dive and return-to-work criteria, obtain specialist assessment when indicated, document residual deficits and restrictions, and consider medication side effects and underlying disease.
Accepting a single diving diagnosis and missing concomitant problems such as pneumothorax with AGE, hypothermia with DCS, or carbon monoxide exposure, without obtaining a complete dive profile and exposure history.
Candidates anchor on the first recognizable syndrome and stop the systematic history and examination.
What to do instead
Use a structured dive-emergency assessment covering dive profile, gas supply, ascent rate, omitted decompression, associated trauma, hypothermia, and toxic exposures; treat all life threats and arrange hyperbaric consultation.