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While studying for (arguably) one of the most miserable exams in existence, I've come across quite a few hyperbaric and diving physiology related questions. Most of them would cause no difficulties to the calibre of divers that frequent YD, but others are a little more challenging.

Have a go*, it's just for fun :)
*not open to anaesthetists!

1. Concerning a diver breathing air at the surface and then descending to a depth of 20 metres while breathing air, what is the approximate increase in oxygen content of the diver's blood?

2. Concerning the solubility of gases in blood. What is the effect of increased solubility on rate of delivery of gas to the tissues? Explain your reasoning.
 

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As an Anaesthetist I will not answer the questions but give some help.

The theoretical maximum oxygen carrying capacity is 1.39 ml O2/g Hb, but direct measurement gives a capacity of 1.34 ml O2/g Hb. 1.34 is also known as Hüfner’s constant.

The oxygen content of blood is the volume of oxygen carried in each 100ml blood.

It is calculated by: (O2 carried by Hb) + (O2 in solution) = (1.34 x Hb x SpO2 x 0.01) + (0.023 x PaO2)

Where:

SO2 = percentage saturation of Hb with oxygen
Hb = haemoglobin concentration in grams pre 100 ml blood
PO2 = partial pressure of oxygen (0.0225 = ml of O2 dissolved per 100 ml plasma per kPa, or 0.003 ml per mmHg)

Note: SpO2 will probably not increase with depth just the PO2.

Enjoy.

Neil
 

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While studying for (arguably) one of the most miserable exams in existence, I've come across quite a few hyperbaric and diving physiology related questions. Most of them would cause no difficulties to the calibre of divers that frequent YD, but others are a little more challenging.

Have a go*, it's just for fun :)
*not open to anaesthetists!

1. Concerning a diver breathing air at the surface and then descending to a depth of 20 metres while breathing air, what is the approximate increase in oxygen content of the diver's blood?

2. Concerning the solubility of gases in blood. What is the effect of increased solubility on rate of delivery of gas to the tissues? Explain your reasoning.
1. None if you measure it at ambient?

2. Must depend on whether the ambient pressure is increasing/decreasing/staying the same.

How silly do I look now?
 

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My own question to those like yourself studying for that exam (which I passed in 1977) is this:
If you have a patient stable on 1.2% inspired Isofulrane (an anaesthetic agent) and you need to put the patient and anaesthetic machine into a hyperbaric chamber and compress to 10m. In order to keep the same level of anaesthesia do you halve, double or leave the same the setting on the vapouriser dial. Explain your reasoning.
Good luck with your little test.
Tim Digger
 

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Yes :)
 

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Absolutely the standard answer.
BUT, there is a small change in splitting ratio due to changes in gas density and viscosity with pressure and the different length/radius of the two gas channels, this produces a non significant change, < 0.1kPa.
Tim Digger
 
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