Respiratory mechanics Flashcards
Diagram of the mechanics of ventilation
Whyn can’t you have a longer snorkel
There is more dead space and hard for you to receive oxygen
What is Boyle’s Law
Pgas = 1/Vgas
Why doesn’t resistance continue to increase as airways get smaller
Higher up, airways have differen structural support
Resistnace is inversely porpotional to what power of radius
4
What is conductance of the airways
Conductivity of the airways increases with increasing volume
Why are veins more compliant to stretch
Arteries have extensive smooth muscle to regulate diameters and resistance to blood flow
Veins and venules are highly compliant and act as a reservoir
Diagram of systemic circulation blood flow
Are smaller arteries and arterioles more resistance to flow
Yes
What is the formula for blood pressure
Cardiac output x resistance
Q x TPR
APPROXIMATION: right atrial pressure is negligible, rigid vessels, steady flow
How is regualtion of flow achieved
Variation in resistance in the vessels
Blood pressure remaisn relatively constant
What does resistance of a tube depend on
Fluid viscosity
Length of tube
Radius of tube
What is poiseuille’s equations
Halving the raidus decreases the flow 16 times
Small changes in vascular tone can produce large changes in flow
What is laminar flow
Velocity of the lfuid is constant
Blood flows fastest closet to the centre of the lumen
What is turbuluent flow
Blood flows erratically - forms eddys and prone to pooling
Associated pathophysiological changes to endothelial lining
Why can you hear the blood on a cuff
Slow deflation of cuff causes turbulent flow
Blood pressure measured on upper arm
Why is our extrapulmonary airways supported with cartilage
Because otherwise the pressure acting on the airway is great than the pressure acting outwards
What is compliance
The tendency to distort under pressure
Change in volume/ change in pressure
What is elastance
Tendency to recoil to its original volume
change in pressure/ change in volume
What happens once the aortic valve closes
Ventricular pressure falls rapidly but aortic pressure falls slowly
Why happens to aorta diameter during systole
It increases
What happens to aorta diameter during diastole
recoil of arteries generating blood flow
What is the speed of blood in aorta
It enters faster than it leaves them
If arterial compliance decrease. How woudl you expect blood pressure measurements to change
Systolic pressure goes up
Diastolic pressure goes down
Increase in pulse pressure
How is venous return facilitated
Skeletal muscle pump
respiratory pump - diaphragm suction pressure
What are varicose veins
incompetent valves causing dilated superficial veins
What causes oedema in feet
Prolonged elevation of venous pressure
What is aneurysmal disease
Vessel walls can weaken causing balloon like distension
Vascular aneurysms increase radius of the vessels
For the same internal pressure, the inward force exerted by the muscular wall must also increase
However the force needed cannot be produced by muscle fibres so aneurysm will rupture
Why is there more ventilation in the base
Alveoli are smalle rand more compliant - more ventilation
Why is there more perfusion in the base
Blood responds to gravity
Heart situated in the middle of the long
More recruitment, less resistance and higher flow rate
What is the ideal spot for ventilation
Perfusion and ventilation are equal
Different zones in the lung
How would compliance and resistance be affected by chronic obstructive pulmonary disease
Increase compliance and increase resistance
How much higher is venous compliance compared to arterial compliance
10 to 20 times greater
