Week 12 Arterial Blood pressure & Heart sounds

• Systole: ventricle contraction • Diastole: ventricle relaxation• Systole and diastole = one cardio cycle

BLOOD PRESSUREBLOOD PRESSURE• Blood pressure is defined as the pressure of the

blood exerts against the blood vessel walls (arteries).

• The highest blood pressure that results from contraction of the ventricles of the heart is the systolic pressure

– the force of blood in your arteries as the heart contracts and pushes it out

• The lowest blood pressure that results from relaxation of the ventricles is the diastolic pressure

– the force of your blood between heartbeats• A measurement of 130 / 85 reflects a systolic

pressure of 130 and diastolic pressure of 85.

MEASURING BLOOD MEASURING BLOOD PRESSUREPRESSURE

• To measure blood pressure, place the blood pressure cuff, sphygmomanometer, and stethoscope as shown in the diagram.

• measured as the brachial artery compressed by a blood pressure cuff

• A stethoscope is used to hear sounds that result from the compression and release of pressure on the blood vessel.

Pronounced (sfig’-mo-ma-nom-e-ter)

Blood pressure readingBlood pressure reading• Place the cuff so that it just fits the arm, and is neither

too tight nor too loose.• Inflate the cuff so that the sphygmomanometer reads at

least 160. You should not hear any sounds at this point.• Slowly deflate the cuff, and note the reading when you

begin to hear thumping/sharp tapping sounds through the stethoscope. This reading is the systolic pressure (the first sound of Korotkoff).

• Continue deflating the cuff until the thumping sound stops/muffles, and note the reading. This is the diastolic pressure (the second sound of Korotkoff).

• Finish deflating the cuff, and remove it from the arm.• Wait ten minutes before attempting to take a second

blood pressure reading on the same person.

Sounds of KorotkoffSounds of Korotkoff

• Sound is created by turbulent flow of blood through the compressed vessel

• Sound disappear when the vessel is no longer compressed by the pressure cuff and normal (non-turbulent) laminar flow resumes

Factors that affect BP

• Genetics

• Age

• Body weight

• State of physical activity

• Level of salt, caffeine, or drugs

Closed circulatory system- Arterial system is

connected to the venous system by means of capillaries

- Allows for gas exchange to occur

- Pulmonary circulation:- (Lungs) Pick up O2 and

drop off CO2

- Systemic circulation:- (Tissues) Pick up CO2 and

drop off O2

Relationship between flow, pressure & resistance

• F = P/R– F = flow– P = pressure– R= resistance

Average rate of blood flow Average rate of blood flow (pressure)(pressure)

• Mean Arterial Pressure =

pulse pressure + diastolic pressure

3*Pulse Pressure= systolic pressure – diastolic pressure

OR

(systolic pressure + 2x diastolic pressure)

3

MAP

120mmHg

75mmHg

Heart sounds

Pathway of blood flow• (from tissues) dO2 blood

enters R. atrium via superior & inferior vena cava tricuspid valve R. ventricle pulmonary semilunar valve pulmonary (trunk) arteries lungs drop off dO2 blood & pick up O2 blood

• (from lungs) O2 blood enters L. atrium via pulmonary veins bicuspid valve L. ventricle aortic semilunar valve aorta rest of the body

Auscultation Auscultation areas using a areas using a stethoscope.stethoscope.

SL valves:-Aortic valve-Pulmonary valve

AV valves-Tricuspid valve-Bicuspid valve

Four major heart sounds

• Heart Sounds: “lub” and “dup”• First Sound (S1): occurs during ventricular systole.

Under low pressure, closure of the atrioventricular (AV) valves and opening of the semilunar (SL) valves “lup”

• Second Sound (S2): occurs during ventricular diastole. Under high pressure, closure of the SL valves and opening of the AV valves “dup”

• Third Sound (S3): turbulence associated with rapid filling of the ventricles shortly after opening of the AV valves

• Forth Sound (S4): turbulence associated with the passage of blood from the atria into the ventricles during atrial systole

Ventricles

• Diastole: the period of ventricular filling (relaxation), the AV valve open; SL valves are closed to prevent arterial blood from re-entering the heart

• Systole: when the ventricles contract & compress the blood in their chambers, closes the AV valves (prevents backflow into atria); SL valves are forced open as the ventricles discharge the blood into the large arteries

End-End-Systolic Systolic VolumeVolume

End-End-Diastolic Diastolic VolumeVolume

Stroke VolumeStroke Volume

Phases of the Cardiac CyclePhases of the Cardiac Cycle Fig. 12-18 on p 374

IsovolumetrIsovolumetric ic contractioncontraction

Isovolumetric Isovolumetric relaxationrelaxation

Fig. 12-19

1. (a) Atrial contraction begins (S4)

2. Atria eject blood into ventricles

3. (b) Atrial systole ends; AV valves close (S1)

4. (c) ventricular contraction

5. (d) Ventricular ejection occurs

6. Semilunar valves close (S2)

7. (e) relaxation occurs

8. (f) AV valves open; passive ventricular filling occurs (S3)