Week 7- Cardiorespiratory Mechanics Flashcards
What happens to the flow volume loop in someone with mild obstructive disease?
It is displaced to the left and theres and indentation on the exhalation curve
What happens to the flow volume loop in someone with severe obstructive disease?
Shorter curve displaced to the left with an indentation on the exhalation curve
What happens to the flow volume loop in someone with restrictive disease?
Displaced to the right with a narrower curve overall
What is important to note when displacing flow volume loops?
The direction of the x axis
What happens to the flow volume loop in someone with variable extrathoracic obstruction?
Blunted at the bottom, otherwise normal
What happens to the flow volume loop in someone with variable intrathoracic obstruction?
Blunted expiratory curve at the top thats otherwise normal
What happens to the flow volume loop in someone with fixed airway obstruction?
Blunted at both halves otherwise normal
Why do arteries and arterioles have a lot of smooth muscle in their walls?
To regulate their diameters and control resistance to blood flow
What is the equation for blood pressure?
Cardiac output x resistance
What 3 variables does resistance to flow depend on?
Fluid viscosity
Length of the tube
Inner radius of the tube
What does halving the radius do to the flow?
Decreases flow by 16 times
Describe laminar flow
The velocity of the fluid is constant at any one point and flows inlayers, flows fastest closest to center of lumen
Describe turbulent flow
Blood flows erratically, forming eddys and is prone to pooling, associated with pathophysiological changed in the endothelial lining of vessels
What is the equation for pulse pressure?
Systolic BP- diastolic BP
What is the equation for MAP?
Diastolic BP + one third pulse pressure
What does a negative transumral pressure indicate?
Collapsed pressure
What is compliance?
The tendency to distort under pressure
What is elastance?
The tendency to recoil to its original volume
What is the equation for compliance?
Change in volume/change in pressure
What is the equation for elastance?
Change in pressure/change in volume
What happens to pressure in the aorta and ventricle when the aortic valve closes? Why is this?
Ventricular pressure falls rapidly
Aortic pressure falls slowly
Because elasticity of vessel is related to the compliance
What happens to pulse pressure as arterial compliance decreases?
Pulse pressure increases
How do varicose veins arise?
Incompetent valves causes dialated superficial veins
How does oedema in the feet arise?
Prolonged elevation of venous pressure
What is aneurysmal disease?
When vessel walls weaken causing a balloon like distention, according to law of LaPlace for the same internal pressure due to increased radius, more internal force must be increased. If muscle fibers have weakened this force cannot be created and the aneurysm will expand until it ruptures
What is compliance?
The relationship between transmural pressure and vessel volume
How do venous and arterial compliance differ?
Venous complaince is 10/20 times greater
What happens to change in volume during inspiration and expiration?
Vol change increases from zero during inspiration and then decreases during expiration
What happens to flow rate during inspiration and expiration?
Inspiration: is negative
Expiration: is positive
Describe the relationship between resistance and radius according to Poiseuille’s Law
Resistance is inversely proportional to the fourth power of the radius
What are veins a reservoir for and why?
A reservoir for blood volume, because they are highly compliant
What vessels provide most resistance to flow?
Small arteries/arterioles
How is flow regulated in vessels?
By varying resistance
What flow is heard in a stethoscope when measuring blood pressure?
Turbulent flow
What is the elasticity of a vessel related to?
Compliance
Why does pulse pressure fall slowly in the aorta when the aortic valve closes?
The elasticity of the aorta is low so it acts as a buffer to change in pulse pressure
What happens to pulse pressure as arterial compliance decreases?
Pulse pressure increases
Describe the entry and exit of blood from the aorta during ejection
Blood exits the aorta slower than blood enters the aorta
What effect does a fall in intra thoracic pressure have on the vena cava?
Opens the vena cava
At what place in the lungs is pressure highest?
At the top
Where are ventilation and perfusion greater in the lungs?
At the base
Out of ventilation and perfusion, which one varies more between the base and apex of the lung?
Ventilation
