Lungs At Depth

Question 1

Apnoea diving

Answer 1

Diving without breathing

Single breath at surface

Question 2

For every 10m of water you descend how does pressure increase?

Answer 2

By 1 atm

Question 3

What is Boyles law?

Answer 3

At a constant temperature the absolute
pressure of a fixed mass of gas is
inversely proportional to its volume

P1V1 = P2V2

Question 4

Total lung capacity in a 23 year old female diver is 8 litres at the surface. What will this volume be at 160m of seawater during breath hold diving?

Answer 4

470 mls

Question 5

What is SCUBA?

Answer 5

Self contained underwater
breathing apparatus

Gas on demand

Gas delivered at ambient pressure

Question 6

What is Daltons Law?

Effects:

Answer 6

Total pressure exerted by a mixture of gases is equal to the sum of the pressures that would be exerted by each of the gases if it alone were present and occupied the total volume.

• At sea level –
– partial pressure N2 = 0.78 ata, O2 = 0.209 ata
• At 10 msw –
–
partial pressure N2 = 1.56 ata, O2 = 0.418 ata

Question 7

46 year old diver. 3 hours dive. 30% O2. 130m depth. Now has shortness off breath, sub sternal pain and cough.
What has happened?

Answer 7

Very high PiO2 0.3x14 = 4.2 ata

Casing Pulmonary oxygen toxicity

Question 8

What is Pulmonary Oxygen Toxicity?

Answer 8

PiO2> 0.5 ata

Relief by PiO2

Little extra for interest:

Oxygen toxicity is a condition resulting from the harmful effects of breathing molecular oxygen (O. ) at increased partial pressures. Severe cases can result in cell damage and death, with effects most often seen in the central nervous system, lungs, and eyes.

V    -    Vision (tunnel vision etc) 
E    -    Ears (tinnitus) 
N    -    Nausea
T    -    Twitching (extremities or facial muscles) I    -    Irritability 
D    -    Dizziness

Question 9

What is inert gas narcosis?

Answer 9

commonest is nitrogen narcosis –
worsens with increasing pressure
first noticed between 30-40 msw
Increased PiN2 – individual variation –
influencing factors- cold, anxiety, fatigue, drugs, alcohol and some medications.

Question 10

What is decompression illness?

Answer 10

N2 bubbles poorly soluble so once taken in due to increased diving pressure they from bubbles in tissue as they ascent to surface.

Forming a rash on the skin

Question 11

What is arterial gas embolism?

Answer 11

Surfacing quickly and holding your breath can cause air trapped in your lungs to expand. This may rupture lung tissue (pulmonary barotrauma), which can lead to gas bubbles being released into the arterial circulation (arterial gas embolism).

Boyles law - as you come to surface gas expands if you hold your breath the gas can not escape and it can tear your vessels.

Treatment urgent recompression

Question 12

What is an embolism?

Answer 12

An embolism is a blocked artery caused by a foreign body, such as a blood clot or an air bubble.

Question 13

What is pulmonary barotrauma?

Answer 13

Pulmonary barotrauma: Damage to the lung from rapid or excessive pressure changes, as may occur when a patient is on a ventilator and is subjected to high airway pressure. Pulmonary barotrauma can also occur in scuba and other forms of diving.

Again link to Boyles law

— pneumothorax etc