Cardio respiratory mechanics

Question 1

Draw the graph for how the volume of air in the lungs change during inspiration and expiration

Answer 1

Question 2

draw the graph for P_alv and flow rate during inspiration and expiration

why do they look so similar

Answer 2

They look similar because air flows down pressure gradient. The greater the presure the greater the flow rate

Question 3

draw the graph to show how the pressure in the pleura changes during inspiration and expiration.

Try to explain the significance

Answer 3

Question 4

draw a flow volume loop and explain what each point and loop signify

Answer 4

Question 5

what is the protocol in order to perform a pulmonary function test

Answer 5

• patient wears noseclip
• Patient wraps lips round mouthpiece
• Patient completes atleast one tidal breath
• Patient inhales steadily to total lung capacity
• Patient exhales as hard and fast as possible
• exhalation continues until Residual voulme is reached
• patient immediately inhales to total lung capacity
• visually inspect performacne and volume time curve and repeat if neccessary

Question 6

after performing the pulmonary function test, what should you look out for?

Answer 6

• Inconsistencies with clinical picture
• Interrupted flow data

Question 7

draw the flow volume curve for mild obstructive lung diseases

Answer 7

• displaced to the left
• indented exhalation curve

Question 8

draw the flow volume loop for severe obstructive disease

Answer 8

• Shorter curve
• displaced to the left
• indented exhalation curve

Question 9

draw the flow-volume loop for restrictive lung disease

Answer 9

• displaced to the right
• narrower curve

Question 10

draw the flow volume loop for variable EXTRATHORACIC obstruction

Answer 10

• Blunted inspiratory curve
• Otherwise normal

Question 11

draw the flow volume loop for INTRATHORACIC obstruction

Answer 11

• Blunted expiratory curve
• otherwise normal

Question 12

draw the flow volume loop for FIXED AIRWAY obstruction

Answer 12

• Blunted inspiratory and expiratory curve
• otherwise normal

Question 13

How is resistance to flow related to diameter

Answer 13

Inversely proportional to 4th power of radius

Question 14

Why doesn’t the resistance continue to increase as airways get smaller

Answer 14

They branch out more and the increased surface area reduce the overall resistance of the system

Question 15

How does resistance and conductance of airway change with increasing lung volume.

give reasons why

Answer 15

• Resistance decreases (1/x equation)
• conductance increases at a constant rate- airway dilates as lung volume increases

Question 16

What is Poiseuille’s Law

Answer 16

Question 17

What is the purpose of te extensive smooth muscles in arteries and arterioles

Answer 17

They help to regulate diameter and resistance to blood flow

Question 18

What is the purpose of the highly compliant venules and veins?

Answer 18

Act as reservoir for blood volume; can easily expand and stretch to have mor blood.

Question 19

Draw the graph for how total surface of vessels, Mean pressure and proportion of systemic blood volume varies across, arteries, veins and capillaries

Answer 19

Question 20

Why does pressure fall across circulation? And what vessels present more resistance to flow?

Answer 20

Pressure falls due to viscous (frictional) pressure losses and the small arteries and arterioles present most resistance to flow

Question 21

What is the relation between Mean arterial pressure and cardiac output ?

Answer 21

P= Qx TPR (Total peripheral resistance)

Q- cardiac output

Question 22

What are the assumptions taken in order to derive the equation that relates mean arterial pressure and cardiac output?

Answer 22

• There’s steady flow
• the vessels are rigid
• right atrial pressure is negligible

Question 23

Physiologically, how is regulation of flow of blood achieved

Answer 23

This is achieved by variation in resistance of the vessels, whilst blood pressure remain as relatively constant

Question 24

What does resistance of a tube to flow depends on?

Answer 24

Poiseuille’s law

• fluid viscosity
• length of tube
• inner radius of tube

hence small changes in vascular tone can produce large changes to flow

Question 25

Draw out the distribution of blood to organs at rest **and** at ***exercise.*** ## Footnote ***what Are the respective cardiac outputs?***

Answer 25

Rest- cardiac output is 5L/min exrecise- cardiac output is 20L/min

Question 26

What are the 2 different types of flow of blood in vessels

Answer 26

Laminar and turbulent

Question 27

What are the characteristics of **Laminar** flow?

Answer 27

* Velocity of fluid is constant at any one point AND flows in layers * Blood flows fastest when closest to the centre of the lumen. Peak velocity is in the middle in a straight line

Question 28

What are the characteristics of **Turbulent** Flow?

Answer 28

* Blood flows erratically, forming eddys * blood is prone to pooling * associated with pathophysiological changes to the endothelial lining of the blood vessels.

Question 29

How can pulse pressure be calculated?

Answer 29

Systolic blood pressure ***minus*** Diastolic blood pressure

Question 30

What causes this dichroic notch seen in the diagram

Answer 30

Closure of the aortic valve

Question 31

How can mean arterial pressure be calculated WITHOUT cardiac output

Answer 31

MAP= DBP + 1/3 Pulse pressure

Question 32

How does slow deflation of cuff of blood pressure measurement allow us to auscultate blood

Answer 32

Causes turbulent flow

Question 33

What is compliance

Answer 33

***Tendency to distort under pressure*** - caused by the relationship between transmural pressure and vessel volume change in volume/ change in pressure

Question 34

What is elastance?

Answer 34

Tendency to recoil to it's original volume change in pressure/ change in volume

Question 35

How does ventricular pressure and aortic pressure changes after ejection? Explain why?

Answer 35

Once aortic valve closes, ventricular pressure falls rapidly to zero but aortic pressure falls more slowly. this is due to large arteries and aorta elasticity which act to buffers the change in pressure elasticity is related to compliance

Question 36

How does MAP increases with age due to changes in arterial compliance

Answer 36

Age makes artery stiffer and compliance decreases. Hence windkessel effect is reduced and DBP is higher this increases pulse pressure

Question 37

Explain arterial compliance

Answer 37

Question 38

What are the 2 methods of facilitated venous return?

Answer 38

1. S**keletal pump**: muscle contracts to squeeze veins one way up towards IVC 2. ***Respiratory pump***- inspiration decreases pressure in thoracic cavity and opens up IVC. Steeper pressure gradient for venous return.

Question 39

What causes Varicosity?

Answer 39

Incompetent valves in veins causes dilated superficial veins in legs. There's more back flow of blood.

Question 40

What causes oedema in feet?

Answer 40

Prolonged elevation of venous pressure even with intact compensatory mechanisms

Question 41

Explain the mechanism with why aneurysm can form and how it can lead to haemorrhage

Answer 41

* Vascular aneurysm increases radius of vessel * for the same internal outward pressure, the muscle wall must produce a inward tension (this increases now due to increased radius) * if muscle fibres cant meet demands due to it's weakened , aneurysm continues to expands until it may ruptures. LAW OF LAPLACE

Question 42

What is an aneurysm and what does aneurysmal dilation of the abdominal gut lead to?

Answer 42

Aneurysm- balloon-like distension formed due to vessel wall weakening Aneurysmal dilation of abdominal aorta can lead to the formation of **diverticuliti** in the gut

Question 43

What can severe transmural pressure cause? But why doesn't it happen to large airways?

Answer 43

Can collapse small- to medium airways but doesn't collapse large airways as the supported with cartilage

Question 44

What is the difference in ventilation and perfusion between base and apex of lung?

Answer 44

Base of lung has higher ventilation and perfusion

Question 45

Why is perfusion Greater at base of lung than at apex

Answer 45

At base theres higher intravascular pressure due to gravity effect hence this leads to: * More recruitment * less resistance * Higher flow rate

Question 46

Why is ventilation greater at the base of the lung than at apex?

Answer 46

At apex pleural pressure is MORE NEGATIVE (-8cmH₂O). Less compliant, larger alveoli hence less ventilation At base: theres **smaller transmural pressure gradient** (pleural pressure is less negative) also there's **small alveoli and they are more compliant**; this leads to **more** ventilation

Question 47

How does the ventilation, perfusion and Ventilation/Perfusion ratio change from **base to apex** of lung? draw the graph explain any differences seen

Answer 47

Ventilation and perfusion both decrease Perfusion decrease at a faster rate as blood is more dense than air the ventilation/perfusion ratio increases

Question 48

Compare the different pressures in the zones of the lungs from **apex to base** where apex is zone 1 and base is zone 3. Write in descending order P_A = Alveolar pressure P_a = arterial pressure P_v = venous pressure

Answer 48

Zone 1 = P_A\>P_a\>P_v Zone 2 = P_a\>P_A\>P_v Zone 3 = P_a\>P_v\>P_A

Question 49

Compare the compliance of artery and vein at **low pressure**

Answer 49

Venous compliance is 10 to 20 times greater than arterial complicates at low pressure

Question 50

What is the effect of increasing smooth muscle contraction on **venous** compliance

Answer 50

This decreases ***venous*** volume and increases venous pressure since most blood is stored in the veins, any small dilation in veins can increase volume of blood stored in them.