MCQ Flashcards
What pressure opens aortic valve
80mmHg
How many times bigger is left ventricular wall to right?
3x
Describe the effect of venous pressure on volume
The initial graph is very steep between 0 and 10mmHg due to the large capacitance of the vessels
Pressure at venules vs larger veins
12-20mmHg in venues, 10mmHg in large veins like femoral/axillary
How is physiological dead space calculated?
Bohr Equation
What is the Bohr equation?
For ease of measurement, PACo2 equal to PaCO2. PECO2 equal to PETCo2
Small a = arterial, capital A = alveolar
What is normal value for Vd/Vt (Bohr equation)?
0.2-0.35
Why does blood flow increase in dependent area of lung?
Gravity increases perfusion pressures in lungs by 1cm H20 for every 1cm below level of heart. Therefore increased hydrostatic pressure
What is Fick equation for CO calculation?
Describe make up of polypeptides in adult Hb and fatal Hb
HBA (two alpha two beta), 2-3% is HbA2 (two alpha two delta).
Fetal = two alpha, two gamma
What type of iron is in Hb
Ferrous (Fe2+)
What is Bohr effect?
As co2 rises, affinity for O2 falls in Hb
What is Haldane effect?
Deoxygenated Hb has greater affinity for CO2
Why does rectal administration increase bioavailability?
Avoid first pass
Chemical form of thiopental
sulphur analogue of the oxybarbituate pentobarbital
How much of thiopental is availble in the active form in humans?
12% is unionised and not protein bound
Blood gas co-efficient for Xenon
0.14 - very low, thus onset/offset is faster than Des/Sevo/N2O
What is first perfect gas law?
Boyle’s law
What is Boyles law
At a constant temp, the volume of a gas is inversely proportional to the pressure
What us second perfect gas law?
Charle’s law
What is Charles’ law
At a constant pressure, the volume of a gas is directly proportional to the temperature
Third gas law?
At a constant volume, the absolute pressure of a gas is directly proportional to the temperature
What is the perfect gas equation?
Constant = (PxV)/T
What are gas laws corrected to?
Standard temp: 273.15K (0 degrees celsius)
Standard pressure: 101kPa
What is the temperature of water’s triple point?
273.16K (0.01C)
Describe the flow nearest the wall in laminar flow and flow in the centre
near wall: It has no flow
Centre: twice the velocity of the average flow
Why is nitrous a liquid in cylinders?
Boiling point -88, Critical temp 36.5, therefore it is a liquid with a vapour layer above
what is nitrous filling ratio?
0.75
How accurate are flowmeters?
accurate to within 2.5%
What reduces accuracy of flowmeters?
Dirt in conical tube
static electricity build up
back pressure from common gas outlet
Which heart sounds correspond to which parts on QRS
Describe pressure in RA, LA, RV, LV
