Hyperbaric Environment Flashcards
What effect does increased depth have on body gases?
Become compressed (Boyles Law) -> dissolves
Which gas laws are most affected by increased pressure?
- Boyle’s law (P ∝ 1/ V)
- Henry’s law (P ∝ solubility)
- Dalton’s law (gases behave independently)
Why does blood pool in the legs of an individual standing on land?
gravity acts on longitudinal axis → hydrostatic pressure gradient down body → blood pulled to lower half of body, where BP is greater
What happens to blood distribution of an underwater individual?
water surrounding → equal hydrostatic pressure gradient applied to body → opposes internal hydrostatic pressure gradient (due to gravity)
as result 500ml blood moves from lower limbs → thoracic region
Physiological consequence of changed venous return (VR) of an underwater individual?
500ml blood from legs → thoracic (increased venous return) → raises right atrial volume & pressure → increased SV → increased CO
Effect of changed VR on pulmonary BF & gas exchange of an underwater individual?
increased pulmonary BF → recruitment of pulmonary blood vessels → increased pulmonary perfusion → better alveolar ventilation ratio (Va/ Q)
Increased central blood volume effect on hormone secretion? Functional consequences of this?
- decreased ADH & aldosterone → decreased water & salt retention
- increased ANH → increased GFR, decreased water and salt retention
What is the “dive response/ reflex”? What characterizes it?
Characterised by:- bronchoconstriction
- bradycardia
- peripheral vasoconstriction
- breathing halts
Explain how the dive reflex works - what stimulates it?
- cold cutaneous thermoreceptors of face become stimulated
- V1 (of CN V) → trigeminal ganglion → sensory trigeminal nucleus (pons
- various effects:
- vagus N → heart (bradycardia), lungs (bronchoconstriction)
- breathing stops
- peripheral vasoconstriction (skin)
What occurs when gases are compressed past residual volume?
Causes negative intra-alveolar pressure = lung squeeze, pulm congestion, oedema and haemorrhage
Who invented the scuba apparatus?
Jacques Cousteau and Emile Gagnan co-invented it. 1943
Why is VO2max reduced when diving?
Air of increased density slow intra-alveolar diffusion of gases
What is ‘raptures of the deep’?
Nitrogen Narcosis
What depth does narcs usually occur?
30msw (4atm)
Symptoms of the narcs
poor judgement short-term memory loss trouble concentrating a sense of euphoria disorientation
