Blood Pressure Measurement Techniques

Blood Pressure Measurement

• The bladder of a blood pressure cuff should be 40% of the arm circumference or 20% wider than the diameter of the midpoint of the limb.
• Appropriate sizes of the length of the bladder cuff are:
  • Newborn
  • Infant
  • Child
  • Adult
  • Large adult
  • Thigh

Blood Pressure Assessment Sites

• Brachial artery: taken on the upper arm, mostly
• Radial artery: taken on the lower arm, possible site for infants or clients with a very large upper arm
• Popliteal artery: taken on the thigh
• Dorsalis pedis and posterior tibial: taken on the lower leg

Korotkoff's Sounds

• Phase 1: first faint clear tapping sounds are heard
• Phase 2: sounds have a swishing quality
• Phase 3: sounds are crisper and more intense
• Phase 4: sounds become muffled and have a soft, blowing quality
• Phase 5: sounds disappear

Assessing Blood Pressure

• Purpose: to obtain a baseline measure of arterial blood pressure for subsequent evaluation
• Assessment: signs and symptoms of hypertension, hypotension, and factors affecting blood pressure
• Preparation:
  • Equipment: stethoscope, sphygmomanometer, and blood pressure cuff
  • Patient: client has not smoked or ingested caffeine within 30 minutes, bladder of the cuff must be at least ⅔ of the arm, and arm should be flexed with the palm of the hand facing up and the forearm supported at heart level
  • Nurse: introduce themselves, explain the procedure, and ask the patient's name and birth date

Blood Pressure Concepts

• Blood pressure: the pressure of blood pushing against the walls of arteries
• Arterial blood pressure: a measure of the pressure exerted by the blood as it flows through the arteries
• Systolic pressure: the pressure of the blood as a result of contraction of the ventricles
• Diastolic pressure: the pressure when the ventricles are at rest
• Pulse pressure: the difference between the diastolic and systolic pressures
• Arteriosclerosis: occurs when the arteries that carry oxygen and nutrients from the heart to the rest of the body become thick and stiff
• Hypertension: a blood pressure that is persistently above normal
• Hypotension: the blood pressure is below normal

Measurements of Blood Pressure

• Normal blood pressure: 120/80 mmHg

Factors Determining Blood Pressure

• Pumping action of the heart:
  • Weak pumping action: low cardiac output and BP
  • Strong pumping action: high cardiac output and BP
• Peripheral vascular resistance:
  • Increased peripheral resistance: increases blood pressure, especially diastolic pressure
  • Factors that create resistance: capacity of arterioles and capillaries, compliance of the arteries, and viscosity of the blood
• Blood volume:
  • Decrease in blood volume: decrease in BP
  • Increase in blood volume: increase in BP
• Blood viscosity:
  • High blood viscosity: high BP
  • High haematocrit: increases viscosity

Factors Affecting Blood Pressure

• Age:
  • BP increases with age
  • Decreased elasticity of arteries in older adults
  • Increased systolic and diastolic pressure in older adults
• Exercise:
  • Physical activity increases cardiac output and BP