Practicals CV

Question 1

What is pulse?

Answer 1

Blood pumped from the left ventricle during systole is ejected into the aorta, which is already full, so it distends due to its elasticity.
As the ventricle relaxes, the aortic valve closes and the elastic aorta recoils to its original diameter, forcing blood into the next part of the aorta, which is stretched and increases tension.
So there is a wave of distension and recoil that travels into the arteries and can be felt - pulse.

Question 2

What is the method of measuring arterial blood pressure using a cuff?

Answer 2

The cuff is inflated until it collapses the brachial artery, stopping the flow of blood and eliminating the sound of the pulse, around 150mmHg.
The air is let out slowly, and when pressure falls below systolic pressure, blood will enter the artery - first Korotkoff sounds, around 120mmHg.
When the cuff pressure falls below diastolic pressure, blood flow becomes continuous and the sound of the pulse disappears, around 80mmHg.

Question 3

What is an auscultatory gap?

Answer 3

There is sometimes a silent gap over a large range between systolic and diastolic pressure.
This is often in old people or those with hypertension.
So the cuff should be inflated until the pulse cannot be palpated.

Question 4

What are the phases of the Korotkoff sounds?

Answer 4

Phase 1 - first sounds - systolic bp.
Phase 2 - sounds soften, no clinical relevance.
Sometimes auscultatory gap.
Phase 3 - return of crisp, sharp sounds - no clinical relevance.
Phase 4 - muffling of sounds.
Phase 5 - disappearance of sounds - diastolic bp.

Question 5

What is average heart beat?

Answer 5

70bp/m

Question 6

From your finger pulse recording, is there any way to determine diastolic pressure? Could a finger pulse measurement ever replace the stethoscope in determining diastolic pressure?

Answer 6

No, diastolic pressure cannot be accurately determined from a finger pulse recording. Finger pulse measurements primarily capture heart rate and pulse amplitude but lack the specific features needed to identify diastolic pressure, which is the pressure in the arteries when the heart is at rest between beats

Question 7

What is the basis for the sounds referred to as Korotkoff sounds?

Answer 7

Turbulent blood flow

Question 8

What is the effect of column height on flow rate?

Answer 8

As the column height increases, the flow rate increases.
Flow is proportional to column height.
This is because the pressure increases with height.

Question 9

What is the effect of tube length on flow rate?

Answer 9

As the tube length increases, the flow rate decreases.
Tube length is inversely proportional to flow rate.

Question 10

What is the effect of tube radii on flow rate?

Answer 10

As tube radius increases, the flow rate increases.
Tube radius is proportional to flow rate.

Question 11

Why is the radius to the power of 4?

Answer 11

This allows blood flow to be controlled in a linear fashion.
A small change in diameter will give a lot bigger increase in flow.

Question 12

What is the effect of the number of tubes in parallel on flow rate?

Answer 12

As the number of tubes increases, the flow rate increases.
Tube number is proportional to flow rate.
This is because increasing the number of tubes decreases resistance to flow.

Question 13

How does the resistance change in vessels?

Answer 13

Series is where the fluid has to flow through one then another.
Adding resistance arranged in series increases the total resistance.
Parallel is where the fluid can go in and out through different routes.
Adding resistance arranged din parallel decreases the total resistance.
In the cardiovascular system the vessels to different organs are arranged in parallel.

Question 14

What is inspiratory reserve volume?

Answer 14

IRV - the maximum volume above tidal volume that we can inspire into our lungs, about 3L.

Question 15

What is tidal volume?

Answer 15

VT - the volume we inspire and expire during restful breathing, around 0.5L.

Question 16

What is expiratory reserve volume?

Answer 16

ERV - the maximum volume below the tidal volume that we can expire from our lungs, around 1.5L.

Question 17

What is residual volume?

Answer 17

The volume of air remaining in the lungs after a full expiration, around 1.2L.
The lungs cannot be emptied completely.

Question 18

What is inspiratory capacity?

Answer 18

IC - the air breathed in during a maximal inspiration at the end of a normal expiration. Calculated by IRV + VT.

Question 19

What is expiratory capacity?

Answer 19

EC - the air breathed out in a maximal expiration after a normal inspiration.
Calculated by VT + ERV.

Question 20

What is functional residual capacity?

Answer 20

FRC - the volume of air remaining in the lungs at the end of a normal expiration.
Calculated by ERV + RV.

Question 21

What is vital capacity?

Answer 21

VC - the air that can be expired from a maximal inspiration.
Calculated by IRV + VT + ERV.

Question 22

What is total lung capacity?

Answer 22

TLC - all the air that is possible for the lungs to contain.
Calculated by IRV + VT + ERV + RV.
Or TLC = VC + RV

Question 23

What is spirometry?

Answer 23

Spirometry measures airflow and the changes in lung volume using a spirometer.
This produces a graph of lung volume over time called a spirogram.
Inspiration produces an upward waveform deflection, whereas expiration produces a downward deflection.

Question 24

What is a pneumotachometer?

Answer 24

Uses flow rate to measure volume.
Air is breathed through the mesh and creates a pressure difference across the mesh, which is proportional to flow rate.
Volume = Flow x change in time.

Question 25

What does a typical spirogram look like?

Answer 25

see picture

Question 26

What is correct about spirometry?

Answer 26

see picture

Question 27

Can all of ERV be expired?

Answer 27

ERV is the maximum volume below the tidal volume that can be expired from the lungs. So all of ERV can be expired.

Question 28

What lung volumes cannot be measured in spirometry?

Answer 28

Residual volume cannot be expired, and since spirometry measures airflows and volumes passing through a mouthpiece it cannot measure RV. As FRC is made up of ERV and RV this cannot be directly measured either.

Question 29

How is Helium used to measure residual volume?

Answer 29

The amount of He at the start must equal the amount at the end. Adding the lung volume to be measured to He will dilute He, so by calculating how much it is diluted can work out the extra volume added. C1V1 = C2V2

Question 30

How is the loss of He prevented?

Answer 30

He can escape by a leak in the spirometer, so use a mouthpiece or nose clip to prevent escape of gas. He escapes in the lungs by moving into the blood stream. But this route is minimal due to the low solubility of He in plasma.

Question 31

Why do gas volumes need converting?

Answer 31

Gas expands as it becomes warmer, so both gases need to be at body temperature. So gas volumes need converting from ambient temperature and pressure dry (ATPD) to body temperature and pressure saturated (BTPS) in the lungs.

Question 32

What are the conditions of He gas?

Answer 32

The He gas mixture in the practical comes from the cylinder as dry gas, so the gas in the bag is at ATPD. Lung volumes are measured at BTPS, so the values need converting to account for the change in temperature and water vapour pressure between the conditions.

Question 33

What is a forced respiratory manoeuvre?

Answer 33

Taking a maximal inspiration to Total Lung Capacity (TLC) as quickly as possible to achieve Peak Inspiratory Flow (PIF). It is immediately followed by a rapid forced maximal expiration all the way down to Residual Volume (RV). The forced manoeuvre requires that the subject exhale as hard and fast as they can, for as long as you can.

Question 34

What are dynamic lung parameters?

Answer 34

Lung parameters that depend on time - the rate of airflow, which indicates the openness of airways. forced vital capacity. forced expiratory volume in 1 second.

Question 35

What is FVC?

Answer 35

Forced vital capacity is the maximum volume of air that a person can forcibly expire after a maximal inspiration.

Question 36

What does forced vital capacity look like on a graph?

Answer 36

see picture

Question 37

What does the graph look like for FVC procedure?

Answer 37

see picture

Question 38

What is FEV1?

Answer 38

The forced expiratory volume in 1 second, following maximal inspiration.

Question 39

What are normal FEV1 values?

Answer 39

It represents more than 80% of the exhaled volume in a healthy young adult.

Question 40

What does a typical trace to measure FVC look like?

Answer 40

See pictures.

Question 41

What are obstructive lung diseases?

Answer 41

There is an increase in airway resistance. So it is harder to blow air out in a forced manoeuvre and the rate is slower.

Question 42

What are restrictive lung diseases?

Answer 42

There is a reduction in the size of the lungs, so volumes would be less, and air flows slower.

Question 43

What does a trace look like in an obstructive lung disease?

Answer 43

See pictures.

Question 44

What does a peak flow meter allow you to assess?

Answer 44

The maximum rate of flow that a person can achieve during a forced expiration.

Question 45

What could a low FEV1/FVC ratio indicate?

Answer 45

That an individual may have obstructive lung disease. This is because an obstructive disease induces increases in airway resistance that reduces the ability to blow out as fast.

Question 46

What are static lung parameters?

Answer 46

Tidal volume. Expiratory capacity. Inspiratory capacity. Inspiratory reserve volume. Total lung capacity. Expiratory reserve volume.

Question 47

For each of the variables, indicate what happens during aerobic exercise? VO2 VCO2 PvO2 PvCO2 PaO2 PaCO2 Arterial pH

Answer 47

VO2 - increases. VCO2 - increases. PvO2 - decreases. PvCO2 - increases. PaO2 - same, due to diffusion reserve, but equilibrium reached later. PaCO2 - same. Arterial pH - same, as CO2 in arterial blood should be the same.

Question 48

Type 2 diabetes can cause autonomic dysfunction due to autonomic neuropathy. Explain why a person with type 2 diabetes might feel lighted-headed when undertaking physical activity.

Answer 48

Cardiac output increases in exercise, but total peripheral resistance decreases more than it should, so mean arterial blood pressure decreases. There is also compromised NO2 release and prostacyclin release. So vasoconstriction is wrong and resistance is too low. The brain does not recieve enough blood and oxygen.