Practicals CV Flashcards
What is pulse?
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.
What is the method of measuring arterial blood pressure using a cuff?
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.
What is an auscultatory gap?
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.
What are the phases of the Korotkoff sounds?
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.
What is average heart beat?
70bp/m
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?
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
What is the basis for the sounds referred to as Korotkoff sounds?
Turbulent blood flow
What is the effect of column height on flow rate?
As the column height increases, the flow rate increases.
Flow is proportional to column height.
This is because the pressure increases with height.
What is the effect of tube length on flow rate?
As the tube length increases, the flow rate decreases.
Tube length is inversely proportional to flow rate.
What is the effect of tube radii on flow rate?
As tube radius increases, the flow rate increases.
Tube radius is proportional to flow rate.
Why is the radius to the power of 4?
This allows blood flow to be controlled in a linear fashion.
A small change in diameter will give a lot bigger increase in flow.
What is the effect of the number of tubes in parallel on flow rate?
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.
How does the resistance change in vessels?
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.
What is inspiratory reserve volume?
IRV - the maximum volume above tidal volume that we can inspire into our lungs, about 3L.
What is tidal volume?
VT - the volume we inspire and expire during restful breathing, around 0.5L.
What is expiratory reserve volume?
ERV - the maximum volume below the tidal volume that we can expire from our lungs, around 1.5L.
What is residual volume?
The volume of air remaining in the lungs after a full expiration, around 1.2L.
The lungs cannot be emptied completely.
What is inspiratory capacity?
IC - the air breathed in during a maximal inspiration at the end of a normal expiration. Calculated by IRV + VT.
What is expiratory capacity?
EC - the air breathed out in a maximal expiration after a normal inspiration.
Calculated by VT + ERV.
What is functional residual capacity?
FRC - the volume of air remaining in the lungs at the end of a normal expiration.
Calculated by ERV + RV.
What is vital capacity?
VC - the air that can be expired from a maximal inspiration.
Calculated by IRV + VT + ERV.
What is total lung capacity?
TLC - all the air that is possible for the lungs to contain.
Calculated by IRV + VT + ERV + RV.
Or TLC = VC + RV
What is spirometry?
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.
What is a pneumotachometer?
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.
What does a typical spirogram look like?
see picture
What is correct about spirometry?
see picture
Can all of ERV be expired?
ERV is the maximum volume below the tidal volume that can be expired from the lungs.
So all of ERV can be expired.
What lung volumes cannot be measured in spirometry?
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.
How is Helium used to measure residual volume?
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
How is the loss of He prevented?
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.
Why do gas volumes need converting?
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.
What are the conditions of He gas?
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.
What is a forced respiratory manoeuvre?
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.
What are dynamic lung parameters?
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.
What is FVC?
Forced vital capacity is the maximum volume of air that a person can forcibly expire after a maximal inspiration.
What does forced vital capacity look like on a graph?
see picture
What does the graph look like for FVC procedure?
see picture
What is FEV1?
The forced expiratory volume in 1 second, following maximal inspiration.
What are normal FEV1 values?
It represents more than 80% of the exhaled volume in a healthy young adult.
What does a typical trace to measure FVC look like?
See pictures.
What are obstructive lung diseases?
There is an increase in airway resistance.
So it is harder to blow air out in a forced manoeuvre and the rate is slower.
What are restrictive lung diseases?
There is a reduction in the size of the lungs, so volumes would be less, and air flows slower.
What does a trace look like in an obstructive lung disease?
See pictures.
What does a peak flow meter allow you to assess?
The maximum rate of flow that a person can achieve during a forced expiration.
What could a low FEV1/FVC ratio indicate?
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.
What are static lung parameters?
Tidal volume.
Expiratory capacity.
Inspiratory capacity.
Inspiratory reserve volume.
Total lung capacity.
Expiratory reserve volume.
For each of the variables, indicate what happens during aerobic exercise?
VO2
VCO2
PvO2
PvCO2
PaO2
PaCO2
Arterial pH
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.
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.
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.
