Transcript Week 12 Arterial Blood pressure & Heart sounds

Week 12 Arterial Blood
pressure & Heart sounds
• Systole: ventricle contraction
• Diastole: ventricle relaxation
• Systole and diastole = one cardio cycle
BLOOD 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
PRESSURE
• 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 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 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
(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
areas using a
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
Phases of the Cardiac Cycle
Fig. 12-18 on p 374
End-Diastolic
Volume
Isovolumetric
contraction
Isovolumetric
relaxation
End-Systolic
Volume
Stroke Volume
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)