2. Blood pressure
• Blood pressure is the force or pressure of the blood against the walls
of the blood vessels.
• Arterial blood pressure is a measure of the pressure exerted by the
blood as it flows through the arteries.
3. Blood pressure
• Blood pressure is mentioned in terms of systolic blood pressure over
diastolic blood pressure.
• Systolic blood pressure is the highest pressure attained in arteries
during systole and diastolic blood pressure is the lowest arterial
pressure during diastole.
4. diastolic pressure
• The diastolic pressure is the pressure when the ventricles are at rest.
• When complete cardiac relaxation occurs and the heart is resting after
the ejection of blood, the pressure within the arteries is called diastolic
blood pressure.
5. Blood pressure
• Arterial blood pressure is measured with a sphygmomanometer.
• Blood pressure is recorded as a fraction: systolic pressure over the
diastolic pressure, and expressed in millimeters of mercury (mm Hg).
• A typical blood pressure for a healthy adult is 120/80 mmHg
6. Pulse pressure
• The difference between systolic and diastolic blood pressures is the
pulse pressure.
• A normal pulse pressure is about 40 mmHg.
7. Physiology of Arterial Blood pressure
• BP reflects the interrelations of cardiac output, peripheral vascular
resistance, blood volume, blood viscosity.
8. Cardiac output and stroke volume
Cardiac output: the amount of blood your heart pumps each minute.
Stroke volume: the volume of blood pumped out of the left ventricle of
the heart during each systolic cardiac contraction.
9. Cardiac output and stroke volume
Cardiac output is the product of heart rate (HR) and stroke volume
(SV) and is measured in liters per minute.
CO = SV x HR
Normal cardiac output is about 5 liters per minute in a person at rest.
11. Cardiac output
• The Bp depends on the cardiac output. When volume increases in an
enclosed space such as blood vessel, the pressure in that space rises.
Thus as cardiac output increases, more blood is pumped against the
arterial walls, causing the BP to rise.
12. Systolic pressure
• The systolic pressure is the pressure as a result of contraction of the
ventricles. When the left ventricle contracts and pushes blood into the
aorta the pressure produced within the arterial system is called the
systolic blood pressure
13. Peripheral resistance
• Blood circulated through a network of arteries and arterioles.
• Arteries and arterioles are surrounded by smooth muscles that
contracts or relaxes to change the size of the lumen.
• The size of arteries and arterioles changes to adjust blood flow to the
needs of local tissue.
14. Peripheral resistance
• Peripheral vascular resistance is the resistance to blood flow
determined by the tone of vascular musculature and diameter of blood
vessels.
• The smaller the lumen of a vessel, the greater is the peripheral
vascular resistance to blood flow.
• As resistance rises arterial BP rises. As vessels dilate and resistance
falls, BP falls.
15. Blood viscosity
Blood viscosity is the thickness of the blood that
affects the ability of blood flow
The viscosity of blood is directly proportional to
blood pressure and inversely proportional to blood
flow
Any condition that causes increased viscosity will
also increase BP and decreased blood flow
Conversely, any condition that causes decreased
blood viscosity will decrease BP and increase blood
flow
17. Factors affecting Blood pressure
• As age increases the BP also increases due to structural
changes in the arteries and especially with large artery
stiffness.
Age
• No clinical significant difference between gender
• After puberty males tend to have higher BP & after
menopause women tend to have higher BP
Gender
• Anxiety, fear, pain & emotional stress result in
sympathetic stimulation, which increases HR, cardiac
output and vascular resistance.
• The effect of sympathetic stimulation increases BP
Stress
• The incidence of high is higher in African-Americans
than in European Americans.
• Africans Americans tend to develop more severe
hypertension at an earlier age.
Ethnicity
18. Factors affecting Blood pressure
• Physical activity increases the cardiac output
and hence the blood pressure.
Exercise
• Pressure is usually lowest early in the morning,
when the metabolic rate is lowest, then rises
throughout the day and peaks in the late
afternoon or early evening.
Diurnal
variation
• Some medications directly or indirectly affects
BP.
• Anti-hypertensive, diuretics lower BP
• Vasoconstrictors and an excess volume of IV
fluids increase it.
Medication
19. Factors affecting Blood pressure
• A period of exercise can reduce BP for several
hours afterwards.
• An increase in oxygen demand by the body
during the activity increases BP.
• In adequate exercise frequently contributes to
weight gain, and obesity is a factor in the
development of hypertension
Activity
and weight
• Smoking results in vasoconstriction, a
narrowing of blood vessels.
• BP rises when a person smokes ad returns to
baseline about 15 minutes after stopping
smoking.
Smoking
20. Scientific principles
• Exercise, emotions, anxiety, fear, tension and worry cause a temporary rise
in blood pressure. So take BP when the patient is in relax.
• The brachial artery in superficial in the antecubital area which is a
convenient place for taking BP
• A twisted cuff may produce unequal pressure and can cause inaccurate
reading so wrap the cuff around the arm smoothly.
• Use the appropriate size of cuff according to the age of the patient. Too
narrow or too wide cuff may produce error in blood pressure reading.
21. Scientific principles
• A noisy environment and parallax error interfere with correct reading
on manometer.
• Air tight system of cuff and tubing facilitates accurate reading.
• Reading is possible only when the diaphragm of stethoscope is
directly over the artery.
• The cuff should not be inflated to much as this causes unnecessary
discomfort to the patient
22. Scientific principles
• The patient`s arm should not be placed above the level of the patient`s
heart as it may cause low blood pressure reading up to 10 mm of Hg.
• The instrument should be in eye level.
23. Special precautions
Do not take blood pressure on a patient`s arm if:
The arm has an intravenous infusion on it.
The arm is injured/ diseased.
The arm has a shunt/fistula for renal dialysis.
On the same side of the patient, he has had a radical mastectomy.
The arm is paralyzed.
26. hypotension
• When the BP is below the normal level.
• When the systolic BP is below 110 mm of hg or diastolic BP is below
70 mm of hg
27. Orthostatic hypotension
• also called postural hypotension — is a form of low blood pressure
that happens when standing after sitting or lying down. Orthostatic
hypotension can cause dizziness or lightheadedness and possibly
fainting.
29. Korotkoff`s sounds
Phase 1: The pressure level at which the first faint, clear tapping or
thumping sounds are heard. These sounds gradually become more
intense. To ensure that they are not extraneous sounds, the nurse should
identify at least two consecutive tapping sounds. The first tapping sound
heard during deflation otf the cuff is the systolic blood pressure.
30. Korotkoff`s sounds
Phase 2: The period during deflation when the sounds havea muffled,
whooshing, or swishing quality.
Phase 3: The period during which the blood flows freely through an
increasingly open artery and the sounds become crisper and more
intense and again assume a thumping quality but softer than in phase 1
31. Korotkoff`s sounds
Phase 4: The time when the sounds become muffed and have a soft,
blowing quality.
Phase 5: The pressure level when the last sound is heard. This is
followed by a period of silence. The pressure at which the last sound is
heard is the diastolic blood pressure in adults.
33. Oxygen saturation
• Oxygen saturation measures the percentage of oxyhemoglobin
(oxygen-bound hemoglobin) in the blood, and it is represented as
arterial oxygen saturation (SaO2)
• Oxygen saturation is a vital parameter to define blood oxygen content
and oxygen delivery.
36. Oxygen saturation
• A pulse oximeter is a noninvasive device that estimates a client`s
arterial blood oxygen saturation by means of a sensor attached to the
client`s finger, toe, earlobe.
• The oxygen saturation value is the percent of all haemoglobin binding
sites that are occupied by oxygen.
• A low can provide warning hypoxemia before other signs such as
cynosis or a change in heart rate are observed.
37. Oxygen saturation
• The pulse oximeters sensor has two parts:
(a) two light-emittingg diodes (LEDs)-one red, the other infrared-that
transmit light through nails, tissue, venous blood, and arterial blood
(b) a photodetector placed directly opposite the LEDs (eg, the other
side of the finger, toe, or nose).
38. Oxygen saturation
• Absorption of light at these wavelengths differs significantly between
blood loaded with oxygen and blood lacking oxygen.
• Oxygenated hemoglobin absorbs more infrared light and allows more
red light to pass through.
• Deoxygenated hemoglobin allows more infrared light to pass through
and absorbs more red light.
39. Oxygen saturation
Because the photodetector measures the amount of red and infrared light
absorbed by oxygenated and de Oxygenated hemoglobin in peripheral
arterial blood, it is reported as SpO2
Normal oxygen saturation is 95% to 100% A value lower than 90% is
considered low oxygen saturation, which requires external oxygen
supplementation and below 70% is life threatening.
