Diving medicine Flashcards

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1
Q

Scuba Diving

A

Self-Contained Underwater Breathing Apparatus

Buoyancy control device (BCD)
Diving cylinders
Regulator mechanism to control gas pressure
submersible pressure gauges

open circuit used more commonly (exhausts exhaled air to environment)

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2
Q

Free Diving

A

Breath-holding activities
Physiological adaptationg - reduced HR, blood flow and volume redistributed (via reflex vasoconstriction), body cooling
risk of hypoxic blackout and drowning

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3
Q

Competitive apnoea

A

A discipline where you attempt to achieve great depths (using weights, weighted sled or guide rope) for longer times or distances, with a single breath.

11 disciplines involved

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4
Q

Ideal Gas Law (Hyperbaric medicine)

A

PV = nRT

P = absolute pressure
V = volume
n = no. of moles
R = universal gas constant
T = temperature
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5
Q

Associated laws to gas law (3)

A
  1. Boyle’s law: P 1/α V
  2. Gay-Lussac’s law: P α T
  3. Charle’s law: V α T

In diving, when the T gets colder, the P in the cylinder may drop (GL) and the V of the air in the lunges or BCD jacket drops (Charle). As the P increases in deeper diving, the volume of air in the lungs or BCD jacket drops (Boyle).

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6
Q

Dalton’s and Henry’s Laws

A
  1. Dalton’s: The total pressure of a mixture of gases exerted is equal to the sum of the individual gases, as if they occupied the total volume alone.
  2. Henry’s: The amount of any gas that will dissolve in a liquid at a given temperature is a function of the partial pressure of the gas in contact with the liquid and its solubility coefficient.

Gas pressure increases as depth increases; Partial pressures of N2 and O2 in breathing air increase. For every 33ft of depth, pressure increases by 1bar. According to Henry’s law, more gas will dissolve into the blood and body tissue, as depth increases.

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7
Q

Nitrogen Narcosis and blood bubbles

A

With continuing descent more N2 is released into the blood stream and gradually dissolves into the lipid part of the tissue.
Every 50ft of depth is equivalent to 1 alcoholic drink; at >150ft the divers experience altered thinking, reasoning, memory loss, calculation errors, increased response time.

Bubbles are formed in the blood and tissue when the diver ascends very quickly, causing the N2 to turn back to its gas form. This is due to lagging between the release of N2 in the blood stream.
Tissue => local issues
Blood => embolisation

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8
Q

Decompression Sickness Type 1

A

Bubble forms in the blood and tissue causing local probs

Pain (the bends; 70-85%) in a joint/tendon area

  • most commonly at shoulder
  • initially mild and gradually worsens - mistaken for pulled muscle
  • dull, deep, throbbing, toothache-like

Pruritus (the skin bends)

  • itching or burning + skin rash
  • papular-like skin rash or, mottling or marbling of skin

Oedema

  • non-pitting, painless
  • uncommon

Anorexia or excessive fatigue

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9
Q

Decompression Sickness Type 2

A

Discomfort on inspiration, burning, sub-sternal

Non-productive cough

  • paroxysmal
  • severe respiratory distress in 2% (potentially fatal)

Hypovolemic shock

Low back pain (30%)

  • sudden onset within minutes to 24hrs; can be delayed to 36hrs esp if diver has been to high altitudes 24hrs prior
  • may progress to more severe neurological Sx e.g. paralysis, paresis, loss of sphincter tone
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10
Q

Predisposing DCS factors

A

Diving - inadequate decompression, failure to take safety stops, rapid ascent, failure to reduce accumulated N2 (i.e. surface intervals), going to higher altitudes too soon post diving (12-24hrs)

Individual - obesity, fatigue, age, dehydration, poor physical condition, prior MSK injury, smoking

Environmental - cold weather (vasoconstriction), heavy work (vaccumn effect => tendon gas pockets), poor buoyancy/ rough sea conditions, heated diving suit (dehydration)

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11
Q

Arterial Gas Embolisation (AGE)

A

Pulmonary over-pressurisation causing large gas emboli to enter pulmonary vein and subsequently systemic circulation
continues to expand as ascending pressure is reduced => increases severity

Sx within 10-20mins of resurfacing and depend on location of embolisation
Coronary = MI or dysrrhythmias
Cerebral = stroke or seizures

Clinical features start sudden or gradually
begin with dizziness, headache and profound anxiousness
more severe symptoms=> unresponsiveness, shock, seizures
neurologic Sx vary and can result to death

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12
Q

General Acute Management of diving problems

A
If shock => resus
Do not delay HBO therapy
100% O2 administered
do not put pt in trendelenburg position
consider IV fluids
transport to nearest ED and hyperbaric facility
try and keep all diving gear with pt

In-water recompression not safe

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13
Q

Oxygen Toxicity

A

Harmful effects of breathing molecular oxygen at elevated partial pressures

Sx - disorientation, seizures, breathing problems, vision changes, death
Patho
- collapse of alveoli => hypoxia
- destruction of membrane => chemical toxicity and haemolysis
- hepatic and renal damage
- neural toxicity

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14
Q

Ear Barotrauma

A

MEBT = most common (10-30%), due to insufficient equilibration of the middle ear

EEBT = during ascend if high pressure air is trapped in external auditory canal either by tight fitting equipment or ear was

IEBT = less common, can lead to varying degrees of conductory or sensorineural hearing loss, vertigo, auditory hypersensitivity

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15
Q

Lung Barotrauma

A

Caused by breath-holding ascend
Trapped gas in the lungs expands as ambient pressure decreased
causes lungs to over-expand and rupture unless breathes out

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16
Q

Buoyancy

A

Archimides’ principle - object, wholly or partially immerses in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the object

Too buoyant = harder to stay down, cannot do safety stop
Too heavy = difficulty adjusting at different depths, constantly having to adjust air using BCD

17
Q

Diving Safety

A

Safety stop every 5m

do not ascend at a pace of >10m/ min (decompression stops)

18
Q

Absolute contraindications to diving

A

Epilepsy
Stroke and TIA
Intracranial aneurysm, arterial-venous malformation or tumour
Progressive neurological problems e.g. MS
Severe heart diseases e.g. congenital heart defect, CHF
Lung problems e.g. severe asthma, COPD
Blood disorders e.g. leukemia, haemophilia
Pregnancy
Severe mental health problems and drug abuse
Inability to qualise pressure in the middle ear by auto-inflation or acute perforation of tympanic membrane

19
Q

Temporary contraindications to diving

A

Illness requiring drug treatment

Sedatives, tranquilisers, antidepressants, antihistamines, steroids

20
Q

What are 2 safer strategies to diving

A
  1. Atmospheric diving suits (ADS) -
    maintains internal pressure of 1 atmosphere, can be used for very deep dives (<=700m). No risk of DCS or nitrogen narcosis
  2. Saturation diving -
    Technique which reduces risk of DCS; diver placed in pressurised environment which can be hyperbaric on the surface or an ambient pressure underwater habitat; tissues absorb mximum partial pressure of breathing gas possible for that depth and decompressed only once at the end => limits times of decompression and thus risk. High risk of negative effect on nervous system and risk of steonecrosis