Clinical I NSG522 Blood Pressure
Physiology of Blood Pressure
The physiology of blood pressure (BP) is as follows:
What Is BP?
Blood pressure refers to the force of blood exerted against arterial walls.
The heart contracts, causing the left ventricle to push blood through the aorta and circulatory system.
As the heart contracts, pressure rises; as the heart relaxes, pressure falls.
This rise and fall creates a pressure wave throughout the arterial system.
What Are the Parameters of BP?
Blood pressure is written as a fraction and is measured in millimeters of mercury (mm Hg).
Consider a BP of 120/80 mm Hg:
The 120 is the systolic pressure, or the maximum pressure the heart exerts during contraction.
The 80 is the diastolic pressure, or the lowest amount of pressure in the arteries when the heart relaxes.
Pulse pressure (force that the heart generates with each contraction) is the numeric difference between the diastolic and systolic pressures, which in this case is 40 (120 – 80 = 40).
What Are Stroke Volume and Compliance?
Stroke volume and the compliance of the arterial system help determine blood pressure.
Stroke volume is the amount of blood injected into the arteries with each heartbeat.
An increase in stroke volume increases blood pressure.
A decrease in stroke volume decreases blood pressure.
However, if the increase or decrease in stroke volume is sustained, detrimental effects can occur, such as hypertension and shock.
Compliance refers to the elasticity of the arterial system, especially the arteries.
Flexible arteries have a high compliance.
Stiff arteries have a low compliance.
Regulation of Blood Pressure
The left ventricle is not the only mechanism for regulating blood pressure. The renin-angiotensin-aldosterone system causes vasoconstriction and sodium/water retention to increase blood pressure when needed.
Other mechanisms function in tandem to contribute to both BP regulation and maintenance of tissue perfusion.
Blood Pressure Regulation
Blood Vessels
Arteries
Contain elastic tissue for stretching, distension, and compliance
Stretch with systolic pressure, relax with diastolic pressure
Maintain enough pressure for continuous flow into capillaries
Arterioles
Control delivery of blood to organs, tissues, and cells
Remain partially contracted to provide peripheral resistance (a major factor in blood pressure)
Mechanisms
Autonomic Nervous System (ANS)
Manages mechanisms used for short-term regulation of blood pressure
Responds to circulatory system signals
Responds to triggers like pain and cold
Antidiuretic Hormone (ADH)
Releases in response to low blood pressure
Causes water to be retained, which increases blood pressure
Previous
Factors Influencing Blood Pressure
Internal and external factors can increase or decrease blood pressure:
Factors
Effects on Blood Pressure
Aging
Increases from decreased compliance (elasticity) of arteries, causing an increase in peripheral resistance
Gender
Generally decreased in women until menopause
Race
Generally increased to hypertension levels in Blacks
Medications
Increases in some women taking oral contraceptives; bronchodilators can not only increase pulse but also blood pressure; there are many others that can increase or decrease blood pressure
Weight gain
Increases as weight increases
Circadian rhythm
Decreased in morning and slightly increases in late afternoon
Head injury
Increases from increased intracranial pressure
Increased blood volume
Increases from the extra fluid
Food intake
Increases after eating; sodium intake may increase blood pressure
Emotions
Increases with anger, fear, and excitement
Pain
Increases with pain
Shock
Decreases and can become life-threatening if continues to decrease
Vasodilation
Decreases because the increase in diameter of blood vessels (enlarges) causes less resistance
Vasoconstriction
Increases because the decrease in diameter of blood vessels (narrows) causes more resistance
Question 1 of 3
Which information is accurate about blood pressure?
Exactly!
Blood pressure is measured by subtracting the diastolic from the systolic pressure.
The numerator is the diastolic pressure.
Blood pressure is the force against the venous walls.
The heart exerts maximum pressure during contractions.
Blood pressure is measured by subtracting the diastolic from the systolic pressure.
Pulse pressure, not blood pressure, is the numeric difference between the diastolic and systolic pressure.
The numerator is the diastolic pressure.
The numerator is the systolic pressure; the denominator is the diastolic pressure.
Blood pressure is the force against the venous walls.
Blood pressure is the force against the arterial walls, not the venous walls.
The heart exerts maximum pressure during contractions.
The heart exerts maximum pressure, the systolic pressure, during contractions.
Question 2 of 3
Match the blood vessel or mechanism of blood pressure regulation to its function.
Exactly!
Controls delivery of blood to organs, tissues, and cells
Arterioles
Manages mechanisms used for short-term blood pressure regulation
Autonomic nervous system
Allows a continuous flow of blood into capillaries
Arteries
Releases in response to low blood pressure to retain water
Antidiuretic hormone
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Question 3 of 3
Which factors increase blood pressure?
Exactly!
Shock
Head injury
Weight gain
Vasodilation
Acute pain
Shock
Shock decreases (not increases) blood pressure and can be life-threatening if it becomes severely reduced.
Head injury
Head injury increases blood pressure from increased intracranial pressure.
Weight gain
Weight gain increases blood pressure.
Vasodilation
Vasodilation decreases (not increases) blood pressure because the increase in diameter of blood vessels (enlarges) causes less resistance.
Acute pain
Acute pain increases blood pressure.
Brachial Site
Brachial artery.
The most common site for a blood pressure assessment is the brachial artery in the upper arm.
Cautions
If the patient has had any axillary node procedures or a mastectomy (breast removal), blood pressure should not be taken on the side the procedure was performed to prevent lymphedema (swelling).
A brachial artery reading is avoided in the following situations:
Presence of an arteriovenous fistula or shunt
Diseased arm, shoulder, or hand
Presence of a cast or bulky dressing
Infusion of intravenous fluids
Other Sites
A general overview of other sites that may be used to obtain a blood pressure measurement is presented, but the module focuses on the brachial blood pressure because it is most commonly used for vital sign measurements.
Popliteal
If the brachial artery is not accessible, the popliteal artery can be used.
Considerations:
Systolic blood pressure in the leg is approximately 20 mm Hg higher when compared to the brachial artery.
Diastolic pressure is usually the same in the leg and the brachial artery.
The blood pressure is recorded as 138/78 popliteal because any site other than the brachial must be documented.
Radial, Posterior Tibial, and Pedal
In some instances, the radial artery at the wrist or the posterior tibial and dorsalis pedis (pedal) arteries of the lower leg can be used.
Considerations:
These sites are used when the blood pressure cannot be obtained in the brachial or popliteal site or when blood pressure is low and cannot be heard with a stethoscope.
The blood pressure is palpated with the nurse’s fingers, and only a systolic reading is obtained.
The blood pressure is recorded as 60 palpable.
Equipment for Measuring Blood Pressure
Common equipment and devices used for measuring blood pressure are described below.
BP Cuff with Sphygmomanometer (Gauge)
Measures BP either manually or automatically; has a bladder that inflates and deflates.
Measures the systolic and diastolic pressures (gauge).
If used for constant monitoring (electronic, automatic), it is important to set alarms that trigger if a reading is too high or too low (do not turn off alarms; check cuff position frequently and remove to monitor skin integrity).
Cuff Sizes
Comes in a variety of sizes to fit accurately.
Cuff bladder should be 60% to 80% of the circumference of the extremity being used.
Cuff width should be 40% of the circumference of the extremity.
Stethoscope
Allows user to hear sounds coming from inside the body.
Allows user to hear Korotkoff sounds (the changing sound of blood flow made as the blood pressure cuff deflates).
Electronic
Measures blood pressure at the wrist or brachial artery.
Easy for patients to use in the home setting.
Electronic, or automatic, blood pressure measurement devices are invaluable for use with the critically ill or potentially unstable patient.
Errors in Blood Pressure Measurements
Possible errors can occur when assessing a patient’s blood pressure, including the following.
Measurement Errors
Faulty equipment
Equipment that has not been calibrated correctly
Improper use of equipment
Incorrect patient positioning
Gauge too far away to read
Clinical I NSG522 Blood Pressure
Falsely Low Measurements
Hearing deficit in the person performing the assessment
Patient’s arm above heart level
Noisy environment
Use of a cuff that is too wide for the patient’s arm
Stethoscope positioned improperly in nurse’s ears
Broken or kinked cuff tubing
Cuff deflated too rapidly
Falsely High Measurements
Assessment too soon after the patient smokes or exercises
Use of a cuff that is too narrow
Cuff deflated too slowly
Cuff bladder reinflated before completely deflated
Questions to Ask Before the Assessment
Blood pressure is measured after the patient has not smoked or ingested caffeine for at least 30 minutes. Obtaining an accurate baseline is critical.
Before a blood pressure assessment, the nurse would ask the patient the following questions because these factors can affect the blood pressure reading or may indicate an underlying heart condition:
Have you exercised or been to physical therapy within the past 15 minutes?
Is there a family history of hypertension?
Do you have any medical devices, like diabetic continuous glucose monitors, on your arm (BP should be taken in the other arm)?
How would you rate your pain level on a scale from 0 to 10?
How would you describe your stress level?
Measuring Brachial Blood Pressure
The technique for taking a blood pressure depends on the site and whether the equipment is manual or electronic.
Manual One Step Method
To obtain a blood pressure manually, use a cuff with a sphygmomanometer and stethoscope.
Position patient sitting or supine, supported arm at heart level, and legs uncrossed.
Locate where to place the stethoscope by palpating for the brachial pulse.
Place cuff 1 inch (2.5 cm) snugly above the antecubital fossa with arrow pointing to the brachial artery pulse.
Position gauge for easy reading.
Place stethoscope over brachial artery and place into ears.
Inflate cuff 30 mm Hg above the patient’s usual systolic reading.
Deflate cuff at a rate of 2 mm Hg/second.
Remember the first Korotkoff sound (first sound heard) will be the systolic reading.
Remember the last Korotkoff sound (last sound before silence) will be the diastolic reading.
There may be an auscultatory gap (absence of sound after the first Korotkoff sound that is as wide as 40 mm Hg; continue to listen). If a gap is noticed, document the finding (e.g., auscultatory gap of 20 mm Hg).
Record as 112/68.
Electronic
Position patient sitting or supine, supported arm at heart level, and legs uncrossed.
Place cuff 1 inch (2.5 cm) snugly above the antecubital fossa with arrow pointing to the brachial artery pulse (palpate to find pulse).
Turn machine on.
Push start button.
Note and record reading (according to image, BP 134/71 with a pulse rate of 83).
Because low blood pressure is not easily picked up by an electronic device, it is not appropriate to use in patients:
With an irregular heart rate
Who are shivering
Experiencing seizure activity
With systolic blood pressure less than 90 mm Hg
Expected and Unexpected Findings
Expected Findings
Expected findings depend on the patient’s age.
Newborn
1-year-old
6-year-old
15-year-old
Adult and Older Adult
Systolic
60–90
74–100
84–<120 94–<120 90–<120 Diastolic 20–60 50–70 54–<80 62–<80 60–<80 From Yoost, B. L., & Crawford, L. R. (2020). Fundamentals of nursing (2nd ed.) Elsevier. Unexpected Findings Values above systolic or diastolic Values below systolic or diastolic A 20 to 30 mm Hg change (either upward or downward) in either the systolic or diastolic reading when compared to an earlier reading Factors Involved in Cue Recognition To accurately recognize cues for blood pressure, the table provides information for relevancy and irrelevancy. The nurse must also recognize which blood pressure cues are the most important and/or an immediate concern. Relevant Relevant cues relate to important information about blood pressure that the nurse obtains from patient questions, vital sign assessment, patient observation and medical record cues, and signs and symptoms. These help the nurse decide what is relevant. Example: Has increased BP, 150/90 Reports a headache Has a family history of heart disease and strokes Irrelevant cues relate to information that is not a factor or contributing factor to the patient’s blood pressure. Example: Is married Has six grandchildren Had prostate surgery 10 years ago The most important cues relate to severely elevated or decreased blood pressure readings. Example: Has BP of 220/110 mm Hg Generally, low blood pressure values are of immediate concern. Example: Has blood pressure of 60/40 ( medical emergency, indicates shock or possible myocardial infarction [heart attack]) Classifications of Hypertension Hypertension is elevated blood pressure. Sustained levels of hypertension can damage the heart, brain, kidneys, and other body systems. Prolonged hypertension can lead to cardiovascular disease, increased risk for stroke, atherosclerosis (the yellow buildup in the image), and thickened arterial walls. There are different classifications for hypertension depending upon the measurement. Clinical I NSG522 Blood Pressure One reading does not establish hypertension. Readings on two or more occasions on different days at different times over a period of time are assessed before diagnosing high blood pressure. The classifications for adults with no prior history of hypertension are as follows: Classification Systolic (mm Hg) Modifier Diastolic (mm Hg) Elevated 120–129 And <80 Hypertension stage 1 130–139 Or 80–89 Hypertension stage 2 ≥140 Or ≥90 Alteration: Hypertension Cues to recognize hypertension are presented below. Causes Neurohormonal dysfunction from overstimulation of angiotensin and aldosterone, causing blood pressure to increase Primary: No known cause Secondary: Caused by a specific disease (kidney or heart disease) Contributing Factors Family history of hypertension Inactive lifestyle Obesity Prolonged stress Smoking Alcohol use Diet high in: Salt Fat Calories Recognizing Cues/Signs and Symptoms Patient Observation Cues Usually asymptomatic (primary reason BP screenings are necessary) Headache Blurred vision Nose bleeds Dizziness Facial redness Medical Record Cues Vital signs graphic/flow sheet indicates elevated blood pressure readings Nurse’s notes indicate unexpected (abnormal) heart sounds History indicates a family history of hypertension Immediate Concern Is urgent but not immediate unless BP is severely elevated or combined with signs and symptom of stroke (facial drooping, difficulty speaking and/or moving arms) Alterations: Hypotension and Orthostatic Hypotension Analyzing Blood Pressure Cues Interventions and Evaluation: Hypertension Clinical I NSG522 Blood Pressure
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