Haemodynamics

Question 1

What is the unit of measuring blood pressure?

Answer 1

mmHg- millimetres of mercury

Question 2

Why is mercury used in measuring blood pressure?

Answer 2

Mercury is a stable fluid with a high density, that expands less as pressure changes

Question 3

Normal blood pressure

Answer 3

120mmHg systolic

80mmHg diastolic

Question 4

MAP definition

Answer 4

Mean Arterial Pressure is an average blood pressure in an individual during a single cardiac cycle

Question 5

How can MAP be determined?

Answer 5

(Cardiac output x systemic vascular resistance) = central venous pressure

Question 6

normal range of MAP

Answer 6

65-110 mmHg

Question 7

Pulse pressure definition

Answer 7

the difference between systolic and diastolic blood pressure.

Represents the force that the heart generates each time it contracts

Question 8

normal pulse pressure

Answer 8

40mmHg

Question 9

What is the systemic pulse pressure similar to?

Answer 9

stroke volume- the amount of blood ejected from the left ventricle during systole

Question 10

How is pulmonary pulse pressure measured?

Answer 10

Measured by right heart catheterisation or may be estimated by transthoracic echocardiography

Question 11

process of sphygmomanometry

Answer 11

Blood pressure meter is composed of an inflatable cuff and a manometer.

The cuff is placed around the patients arm and inflated- causing the brachial artery to collapse.

The artery beneath the cuff is then released in a controlled manner.

The mercury or mechanical manometer meaures the pressure.

Question 12

Korotkov sounds definition

Answer 12

Sounds that medical personnel listen for when they are taking blood pressure using a non-invasive procedure

Question 13

Are the sounds the same as the vibrations of the ventricles? explain

Answer 13

No, as there should be no audible sound in a normal person with no arterial disease.

If the cuff of the sphygomanometer is placed around the patient’s upper arm and inflated to a pressure above systolic, there should be no audible sound. This is due to the pressure in the cuff being high enough such that it completely occludes the blood flow

Question 14

When is the first Korotkoff sound heard?

Answer 14

When the pressure is dropped to a level equal to that of the patient’s systolic blood pressure

Question 15

Why is the sound heard?

Answer 15

Some blood will be able to pass through the upper arm when the pressure in the artery rises during systole. The blood flows in spurts as the pressure in the artery rises above the pressure i the cuff, then drips down in the uncuffed region- resulting in turbulence that produces an audible sound.

Question 16

5 phases of Korotkov sounds

Answer 16

1. faint, repetitive, clear tapping sounds which gradually increase in intensity- systolic pressure
2. brief period may follow during which the sounds soften and acquire a swishing quality
3. return of sharper sounds, crisp and regain intensity
4. distinct abrupt muffling sounds
5. point at which all sounds finally disappear- diastolic pressure

Question 17

central venous pressure definition

Answer 17

blood pressure in the venae cavae, near the right atrium of the heart

Question 18

normal pressure range

Answer 18

3-8 mmHg

Question 19

How is CVP measured?

Answer 19

connecting the patients central venous catheter to a special infusion set which is connected to a small diameter water column.

Question 20

How is the patient lying during CVP measuring?

Answer 20

semi supine- tilted 45 degree

Question 21

Define jugular venous pressure

Answer 21

The indirectly observed pressure over the venous system via visualisation of the internal jugular vein.

Question 22

How is the jugular venous pressure visualised?

Answer 22

at the semi supine angle, the height from the atria can be visualised- if it is greater than 10cmH2O then it could suggest heart failure and other conditions

Question 23

What is the normal central venous pressure?

Answer 23

5mmHg or 7cmH2O

Question 24

Cardiac Output definition

Answer 24

The amount of blood ejected from the left ventricle in one minute

Question 25

Average CO

Answer 25

5 litres/minute

Question 26

What is the relationship between atrial and venous pressures, cardiac output and systemic vascular resistance

Answer 26

MAP-CVP = CO x SVR

Question 27

What determines the systemic vascular resistance?

Answer 27

vascular compliance determined by the muscle tone in the tunica media and the elasticity of fibres

viscosity of blood, length of vessel, radius of blood vessel

Question 28

compliance definition

Answer 28

relationship between volume and pressure

The ability of a vessel to distend and increase volume with increasing pressure and to resist recoil

Question 29

What vessels have high compliance + what does this mean?

Answer 29

veins- higher compliance means they deform more easily than others would under the same pressure and resistance

Question 30

flow definition

Answer 30

volume moved over time

Question 31

Explain conservation of flow

Answer 31

right and left flows are equal- at a steady state

Question 32

two different types of flows explained

Answer 32

laminar- most efficient delivery of blood in one direction

turbulent- suboptimal, favoured by wide diameter, fast velocity . Occurs mainly in ventricles and increases the risk of blood clotting

Question 33

how does lymph flow return to circulation?

Answer 33

Via the thoracic duct