Cardiorespiratory Mechanics Flashcards
How does pouseuille’s equation relate to blood flow
Small changes in vascular tome can produce large changes in flow
Importance of arterial diameter as a determinant of resistance
What occurs in turbulent blood flow and why might it happen
Blood flows irrationally, forms eddys, prone to pooling, likely to clot
Associated with pathophysiological changes to endothelial lining of blood vessels
Describe laminar flow
Velocity of fluid is constant at any one point and flows in layers
Blood flows fastest closest to centre of lumen
What is heard in blood pressure measurement and how is this sound brought about
Turbulent flow of blood can be heard with the stethoscope, caused by slow deflation of the cuff
How does pressure change in collapsible tubes during ventilation and what does this mean for our large extra pulmonary airways
Pre,mid,end inspiration, airway transmural pressures increases, patent
Hard expiration, airway transmural pressure decreases to -ve, collapsed
This is why large extrapulmonary airways are supported with cartilage
What is the relationship between compliance and elastance
Distort under pressure vs recoil to original volume, inverse relationship
How is continuous flow of blood achieved after systole and closure of aortic valves, when ejection ceases
How would a decrease in arterial compliance affect BP measurements
due to recoil of elastic arteries (eg aorta), pressure falls slowly and there is diastolic flow in downstream circulation
Systolic increases, diastolic falls, pulse pressure increases
What are the two methods of facilitated venous return
Skeletal muscle pump Respiratory pump (negative pressure from diaphragm pulling down, pulls vein apart, pulling blood up)
What causes varicose veins
Incompetent valves cause dilated superficial veins in leg
What causes oedema in feet
Prolonged elevation of venous pressure, even with intact compensatory mechanisms
What is abdominal aortic aneurysm caused by
Local failure of vessel to regulate pressure (eg muscle fibres have weakened), cause balloon like distension, inward force from vascular wall to overcome increased radius cannot be produced. Aneurysm will expand and potentially rupture
How does alveolar size and compliance change down the lungs and why
What force causes this
Become smaller and more compliant as there is a smaller transmural pressure gradient, more ventilation
Gravity
How does the gradient of diffusion and ventilation vary from base to apex
Where does wasted perfusion occur
Perfusion has a steeper decline than ventilation, as blood is denser than air
At base
