Diving physiology in man

Question 1

How much pressure in 10m of water?

Answer 1

1 atmosphere

Question 2

What is boyles law relating pressure and volume?

Answer 2

P1V1=P2V2

Question 3

Danton’s law to find total pressure?

Answer 3

Add up all partial pressures

Question 4

How does p02 and pN2 change depending on depth of water?

Answer 4

It is directly proportional. E.g. po2 from 0.21 to 0.42 to 0.63 (surface to 10 metres to 20 metres).

Question 5

What are the immediate and long term effects of cold water shock?

Answer 5

Immediate:
Tachycardia
Peripheral vasoconstriction
Hyperventilation

Short-long term:
Loss of coordination
Hypothermia 
Incapacitation
Drowning

Question 6

Effects of the diving response?

Answer 6

Bradycardia
Apnoea (cessation of breathing)
Increase in SV
Peripheral vasoconstriction
Contraction of spleen
Increase in MAP 
Reduction on 02 consumption

Question 7

What are the receptors of the face that are stimulated in immersion?

Answer 7

Ophthalmic and maxillary divisions of the trigeminal nerve. Stimulated by water.

Question 8

Why is diving less oxygen conserving in humans than diving mammals?

Answer 8

In humans BP rises and bradycardia and vasoconstriction are less intense.

Question 9

Limitations of free diving in man?

Answer 9

Co2 tolerance or declining 02 partial pressure.

Question 10

How to prolong breathhold?

Answer 10

Hypocapnia (reduced co2) can double breath hold time and supplementation with 100% o2 can prolong to above 4 mins.

Question 11

Common cause for shallow water blackout?

Answer 11

Hyperventilation prior to diving. Hypoxia causes unconsciousness before diver reaches surface due to changes in pressure.

Question 12

Mechanisms to increase breath hold dive?

Answer 12

Lung volume increase:
Lung ‘packing’
Lung ‘training’

Oxygen carriage:
Training
Erythropoietin
Spleen

Relaxation:
Lowers VO (amount of 02 consumed)
Lowers resting HR

Question 13

What genetic selection in humans is an adaptation in breath hold diving?

Answer 13

Larger spleens. For increase in RBC into blood stream providing a higher 02 reservoir.

Question 14

Effect of SCUBA equipment while scuba diving on lung volume?

Answer 14

Lung volume remains at 100% despite change in depth and pressure.

Question 15

What is dissolved gas narcosis?

Answer 15

Many gassed are mild anaesthetics and can have similar effects to alcohol. Effects related to partial pressures.

Question 16

How to avoid nitrogen narcosis?

Answer 16

Reducing pn2:
Reducing fraction in breathing mix
Reducing depth of dive

OR acclimatisation with repeated exposure.

Question 17

What is the lorrain smith effect?

Answer 17

Pulmonary 02 toxicity. Too much o2 results in not enough 02 reaching blood resulting in hypoxia. Can also result in damage to lung epithelium and lung oedema.

Question 18

What is Paul Bert effect?

Answer 18

Seizure that occurs if subject is allowed to breath 100% o2 at high pressures. Happens due to disruption of GABA metabolism.

Question 19

Types of barotraumas?

Answer 19

Damage to nasal sinuses due to blockages

Bloodshot eyes due to tight fitting mask

Ruptured eardrum due to rapid compression

Rupture of lung tissue due to breath hold while ascending or blockages

Abdominal: swallowing air at depth or antacids can lead to rapid decompression

Explosion of tooth

Question 20

Consequences of ascending too fast from diving?

Answer 20

Arterial Gas Embolism:

Bronchospasm, extra alveolar gas enters left side of heart and can cause embolism

Question 21

What is decompression illness (the bends)?

Answer 21

Formation of excessive bubbles during the decompression phase of a dive bypassing the lung filter. Bubbles can form in many diff places.