ABPM Undersea and Hyperbaric Medicine flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Boyle's law in diving

At constant temperature, gas volume is inversely proportional to absolute pressure; at 20 metres seawater a bubble is one third of its surface volume.

Dalton's law

Total pressure of a gas mixture equals the sum of partial pressures; at 30 metres seawater (4 ATA) nitrogen partial pressure in air is 0.79 × 4 = 3.16 ATA.

Henry's law

Dissolved inert gas in blood and tissue is proportional to its partial pressure; higher pressure and longer exposure increase tissue nitrogen loading and decompression risk.

Nitrogen narcosis

Progressive impairment of judgement and coordination caused by raised nitrogen partial pressure, typically apparent below 30 metres, reversed by ascent; helium reduces it.

Decompression sickness

Illness from inert gas bubbles; Type I involves joints and skin, Type II neurological or pulmonary symptoms; treat with 100% oxygen, supine positioning, and urgent recompression.

Arterial gas embolism

Bubbles entering the arterial circulation after pulmonary barotrauma, often with loss of consciousness soon after ascent; requires immediate recompression and 100% oxygen.

Middle ear barotrauma

The most common diving injury; failure to equalise pressure across the tympanic membrane causes pain, haemorrhage, or rupture, especially during descent.

Oxygen partial pressure limit

For working dives the NOAA maximum is 1.6 ATA oxygen partial pressure; recreational diving keeps 1.4 ATA to limit CNS seizure risk.

Hyperbaric oxygen therapy

Breathing near-100% oxygen at pressures above sea level, typically 2.0–2.5 ATA, to treat ischaemia, infection, and bubble disease.

HBOT absolute contraindication

Untreated pneumothorax is the only absolute contraindication; relative issues include bleomycin, disulfiram, uncontrolled seizures, and severe COPD with CO2 retention.

Carbon monoxide half-life

COHb half-life falls from about 320 minutes on room air to 90 minutes on 1 ATA oxygen and 20–30 minutes at 2.5–3 ATA.

Diabetic foot ulcer HBOT

Adjunctive therapy for Wagner grade 3 or higher wounds after debridement and offloading, improving oxygen delivery to hypoxic infected tissue.

Osteoradionecrosis

Radiation-induced bone necrosis, usually of the mandible, treated with hyperbaric oxygen to promote angiogenesis and wound healing, often combined with surgery.

Air breaks

Five-minute air breathing periods between oxygen cycles reduce pulmonary and CNS oxygen toxicity during prolonged hyperbaric treatment tables.

US Navy Table 6

Standard recompression table for decompression sickness: 2.8 ATA oxygen cycles with air breaks, then gradual ascent, lasting about 4.5 hours.

Oxygen toxicity seizure

CNS toxicity risk rises with oxygen partial pressure and exposure time; seizures are usually self-limiting but can cause aspiration or physical injury.

Necrotising fasciitis HBOT

Used adjunctively with urgent surgical debridement and antibiotics; hyperoxygenation inhibits anaerobic bacteria and improves neutrophil killing.

Compromised flap HBOT

Hyperbaric oxygen supports compromised skin grafts and flaps by increasing oxygen diffusion, reducing oedema, and promoting neovascularisation.

Multiplace chamber atmosphere

Multiplace chambers are compressed with air; patients breathe oxygen by mask, keeping chamber oxygen below about 23.5 percent to reduce fire risk.

Chamber fire prevention

Prohibit petroleum products, oils, and synthetic clothing; use cotton gowns, eliminate ignition sources, and maintain fire suppression inside the chamber.

Chamber relief valves

Pressure relief valves and periodic proof testing protect the chamber from overpressurisation and must be checked before every treatment.

Inside attendant role

A trained attendant accompanies patients in multiplace chambers to assist with masks, equalisation, medical problems, and emergencies during treatment.

Equalisation on compression

Compression is slowed or paused when a patient cannot clear the ears; Valsalva, swallow, or Frenzel manoeuvres are used before pressure rises further.

Medical lock

A small pressure lock on a chamber used to transfer drugs, equipment, or specimens without decompressing the main compartment.

Chamber fire emergency

In fire, oxygen delivery is stopped, the fire suppressed, and the chamber vented as rapidly as safety permits while occupants breathe air.

Backup gas supply

Chambers require backup oxygen and air supplies sized for the full treatment plus decompression, with cross-connections and alarms.

Dysbaric osteonecrosis

Bone death near joints, especially femoral and humeral heads, linked to decompression exposure; often asymptomatic and detected by radiography or MRI.

OSHA commercial diving

US commercial diving falls under OSHA 29 CFR 1910 Subpart T, covering dive plans, supervisors, tenders, decompression tables, and medical fitness.

Flying after diving

Wait at least 12–18 hours after no-stop recreational dives and 24 hours after decompression dives before ascending to altitude.

Saturation diving

Divers live at storage depth for days or weeks; a single decompression at the end reduces cumulative exposure and improves efficiency.

Cylinder hydrostatic testing

Compressed gas cylinders require visual inspection and periodic hydrostatic testing, commonly every 5 years, with clear markings and safe storage.

Altitude diving adjustment

Diving at altitude requires reduced depth limits and adjusted tables because surface pressure is lower and decompression stress greater.

Caisson disease

Decompression sickness in compressed-air workers such as tunnellers; historically common before staged decompression in air locks was used.