Flashcards in Control of Arterial Blood pressure Deck (45)
What is Blood pressure?
The (outwards) hydrostatic pressure exerted by the blood on the blood vessel walls
Define systolic blood pressure?
The pressure exerted by blood on the walls of the aorta and systemic arteries when the heart contracts (Shouldn't reach/exceed 140mmHg when resting
Define diastolic blood pressure?
The pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart relaxes (should not normally reach/exceed 90mm Hg under resting conditions)
Clinical blood pressure of 140/90mmHg or higher and a daytime average of 135/85mmHg or higher
Define pulse pressure?
The difference between systolic and diastolic blood pressures (normally between 30-50mmHg)
How does blood flow in arteries normally?
In a laminar fashion - not audible through a stethoscope
What can you use to estimate arterial blood pressure?
Stethoscope or sphygmomanometer
What happens if external pressure exceeding the systolic is applied to an artery?
The flow of that artery would be blocked and no sound heard through a stethoscope
What happens if external pressure is applied to an artery and kept between systolic and diastolic pressure?
The flow becomes turbulent when blood pressure exceeds external pressure - this flow is audible through a stethoscope
When estimating BP- to hear Korotkoff sounds- when is the first sound heard ?
The first sound is heard at peak systolic pressure- this is the followed by intermittent sounds due to turbulent spurts
What happens when a cuff is applied and its pressure is less than 80 mmHg and is below blood pressure in the cardiac cycle?
Blood flows in an smooth laminar fashion
When is the last Korotkoff sound heard>
Minimum diastolic pressure (Muffled/muted)- no sounds are heard after cause there is continuous smooth laminar blood flow
When is diastolic pressure heard in BP?
The 5th Korotkoff sound
What is the main force for blood flow and why?
The main driving force for blood flow is MAP because the RA pressure is close to 0
What drives the blood around the systemic circulation ?
Pressure gradient between the RA (right atrium) and the Aorta (AO)
Pressure gradient equation?
Mean arterial pressure - central venous (Right atrial) pressure
What is mean arterial blood pressure?
The average arterial blood pressure during a single cycle which involves contraction and relaxation of the heart
Which portion of the cardiac cycle is longer?
Diastolic- twice as long as systolic
Formula for MAP? equation 1
[2x diastolic pressure]+systolic pressure
Formula for MAP? equation 2
diastolic blood pressure + 1/3 pulse pressure
Normal range of MAP?
Minimum MAP to perfuse coronary arteries, kidneys and brain?
Normal arterial BP?
Why must MAP be regulated to within a narrow range?
-Pressure is high enough to perfuse internal organs (kidney, brain and heart)
-Pressure is not to high to damage blood vessels or place extra strain on heart
Equation to get MAP with important relationships?
Mean arterial pressure= cardiac output x systemic vascular resistance
MAP= CO x SVR
What is cardiac outpu?
Volume of blood pumped by each ventricle of the heart per minute
Equation to find cardiac output?
Cardiac output= Heart rate x stroke volume
C0= HR x SV
Define stroke volume?
Volume of blood pumped by each ventricle of the heart per heart beat
Another equation to find MAP relationships?
MAP= Stroke vol x heart rate x systemic vascular resistance