Funtabulously Frivolous Friday Five 256

The common answer: the blood is pumped out, slows and the falling blood closes the valves.

This is incorrect and would result in the valves closing incorrectly and permanent regurgitation in everyone.

So how do the valves close?

Leonardo da Vinci noted that mammals contained a sinus of valsalva just above the aortic valve and pondered what this was for.

He predicted it was used to close the aortic valve by forming ‘eddies’  and close the valves before the blood slows down.

Leonardo built a glass model to prove his theory. Surprisingly it took 450 years to prove him right. An engineer called Dr Brian J Bellhouse in 1969 built an updated model confirming the vortices and just in the last few years, 4D cardiac monitoring has proven the same concept.

• Peacock JA. An In Vitro Study of the Onset of Turbulence in the Sinus of Valsalva. Circulation Research 1990;67:448-460

No, not physiologically, unless you are combining your activities with performance enhancers.

Elite athletes have a high haematocrit, in theory compounded by taking EPO. This creates blood at a high viscosity which is great during the Tour de France but not when your cardiac heart rate drops and you need this sludge to pass through your coronaries. This is the theory behind many athletes suddenly dying in their sleep.

Marco Pantani retired as EPO allegations were beginning to surface but later died from cocaine and heart failure aged 35 in 2004. 

• Matt Rendell The Death of Marco Pantani. 2012

Activation of Baroreceptors.

1. When you enter the water, the hydrostatic pressure in the water pushes on your arms and legs increasing the return of blood to the heart, activating baroreceptors.
2. The coldness of the water also causes the blood vessels in your periphery to contract, even more cardiac return and stimulation of the baroreceptors. 
3. This activation of the baroreceptors culminates in you urinating in the water.

Genetics – a gene called EPAS 1 ‘super athlete gene’ is one of many likely responsible (see video below for a full description).

• They prioritise glucose metabolism over fats at altitude (and thus need less oxygen).
• Creatine phosphate can also be used as an energy substrate when ATP is scarce, in Sherpa’s this level increases at altitude but in lowlanders it decreases.
• They have more capillaries per square cm muscle.
• Bigger chests.
• Greater lung capacity.
• Less hypoxic pulmonary vasoconstriction.
• No cardiac remodelling.
• No change in metabolic rate at altitude
• Higher levels of nitric oxide.
• Lower haemoglobin, haematocrit and mitochondria due to increased efficiency of utilising oxygen.

• Hanaoka M et al. Genetic Variants in EPAS1 Contribute to Adaptation to High-Altitude Hypoxia in Sherpas. PLoS ONE 7(12): e50566

• Allows the red cones to recharge in the eye.
• Prevents red overload (i.e. seeing too much blood in theatre)
• Prevents ghost images.

Initially as sterility was becoming popular, the ol’ bloodied surgical apron was out and white was adopted. White is notoriously difficult to remove blood from (try heparin – top tip).

So why not have red scrubs? Our eyes detect colour using 3 types of cone cells (Red, Blue and Green). If you look at one colour for a long time this cones pigment becomes depleted and you can’t see that colour as well. So in theatre, when the surgeon is looking at predominantly red, it is not a good idea to flood the eye with more red colours.