PHYSICAL EVALUATION I (Dent 5121) Vital Signs: Blood Pressure
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PHYSICAL EVALUATION I (Dent 5121) Vital Signs: Blood Pressure Lecture Objectives After today’s lecture, the student will be able to: Describe the objectives of assessing the vital signs. Describe how to assess the blood pressure. Describe how common technical errors cause inaccurate readings. Objectives of Assessing the Vital Signs Baseline indicators of a patient’s physical status. Can help detect undiagnosed medical problems. Determine the severity of a current disease Vital Signs • Blood pressure • Pulse • Respirations • Temperature Blood Pressure • Force of blood pushing against vessel wall • Measured indirectly • Systolic pressure • Diastolic pressure Blood Pressure Controlled by 5 Factors Cardiac output Increased CO = increased BP Peripheral vascular resistance Increased resistance = increased BP Volume of circulating blood Increased volume = increased BP Blood Pressure Controlled by 5 Factors Viscosity of blood Increased thickness of blood = increased BP Elasticity of vessel walls Decreased elasticity of vessel walls = increased BP Patient Factors that Alter Blood Pressure • Age • Increased activity • Sex • Emotion • Race • Posture • Weight • Artery • Diurnal rhythm • Disease Sphygmomanometer Mercury Sphygmomanometer Sphygmomanometer Components Cuff Bladder Aneroid pressure gauge Bulb Tubing Correct cuff size Cuff width ≈ 40% of arm circumference Bladder length ≈ 80% of arm circumference Cuff range indicator Stethoscope Bell more effective in transmitting the lowpitched sounds Diaphragm most commonly used Blood Pressure • Steps – Prepare patient – Estimate systolic pressure – Measure blood pressure Prepare Patient Seated upright Arm free of clothing Antecubital crease at level of the heart (middle of thorax) Arm slightly flexed at the elbow and comfortably supported Prepare Patient Lower border of the cuff 2.5 cm above the antecubital crease Prepare Patient Lower border of the cuff 2.5 cm above the antecubital crease Center bladder over the brachial artery Prepare Patient Lower border of the cuff 2.5 cm above the antecubital crease Center bladder over the brachial artery Secure cuff snugly Prepare Patient Lower border of the cuff 2.5 cm above the antecubital crease Center bladder over the brachial artery Secure cuff snugly Dial of aneroid manometer directly facing you Estimate Systolic Pressure • Palpatory method – Palpate brachial or radial pulse Inflate the cuff quickly to 100 mm Hg. Then, inflate the cuff 10-15 mm Hg/s until you no longer feel the pulse Estimate Systolic Pressure Palpable systolic blood pressure tends to be 10-15 mm Hg below true systolic pressure Increase the pressure by 20 mm Hg Measure Blood Pressure Place the bell or diaphragm of the stethoscope lightly over the brachial artery Measure Blood Pressure Deflate cuff slowly (2-3 mm Hg/s) Pressure at which you hear the first sounds represents the systolic pressure Measure Blood Pressure Continue to deflate the cuff slowly Pressure on the manometer at which the sounds disappear represents the diastolic pressure Measure Blood Pressure Deflate the cuff for 10-20 mm Hg below the diastolic pressure Rapidly deflate the cuff completely Record as systolic/diastolic pressure (to nearest even number mm Hg) Wait 2 minutes or more then repeat, average your readings Korotkoff Sounds • Watching dial versus Korotkoff sound • Watching dial versus Korotkoff sound – Systolic pressure estimated high – Diastolic pressure estimated low Auscultatory Gap Period of silence between phase 1 and phase 2 of the Korotkoff sounds 5% of people, most often with hypertension Unrecognized auscultatory gap causes serious underestimation of systolic pressure or overestimation of diastolic pressure Auscultatory Gap Blood Pressure Website • http://www.abdn.ac.uk/medical/bhs/ind ex.htm Automatic Blood Pressure Monitors Automatic Blood Pressure Monitors • Advantages – Fast – Automatically detects how high to inflate cuff – Eliminates SOME human error – Measures pulse – Automatically stores some number of BPs and pulses Automatic Blood Pressure Monitors • Disadvantages – Not determine rhythm and amplitude of pulse – Needs to be calibrated (annually?) – More likely to break than manual BP equipment Automatic Blood Pressure Monitors • Look for monitors recommended by the Association for the Advancement of Medical Instruments • Read the manufacturer’s instructions! Automatic Blood Pressure Monitors • Patient preparation the same as for manual BP measurement Patient seated upright Arm free of clothing Upper arm at level of right atrium Arm slightly flexed at the elbow and comfortably supported Automatic Blood Pressure Monitors • Patient preparation – Lower border of the cuff 2.5 cm above the antecubital crease – Center bladder (green indicator) over the brachial artery – Secure cuff snugly Automatic Blood Pressure Monitors • Memory function Common Errors in Measuring Blood Pressure Factor Result Rationale Patient anxious, angry, recently active Falsely high systolic Sympathetic stimulation of heart Antecubital crease positioned below heart Falsely high systolic and diastolic Adds force of gravity to brachial artery pressure Failure to estimate systolic pressure Falsely low systolic Miss first Korotkoff sound Common Errors in Measuring Blood Pressure Factor Result Rationale Cuff size too narrow/too short Falsely high systolic Needs excessive pressure to occlude brachial artery Cuff size too wide/too long Falsely low systolic Requires less pressure to occlude brachial artery Cuff size too loose, uneven, or bladder balloons out of wrap Falsely high systolic Needs excessive pressure to occlude brachial artery Common Errors in Measuring Blood Pressure Factor Result Rationale Deflate cuff too quickly Falsely low systolic/falsely high diastolic Poor resolution Re-inflate the cuff during deflation/ not wait more than 2 minutes before retake blood pressure Falsely low systolic and falsely high diastolic or auscultatory gap Venous congestion in forearm makes sounds less audible Inaccurate placement of stethoscope Inaccurate reading Weak or inaudible Korotkoff sounds Lecture Objectives After today’s lecture, the student will be able to: Describe the objectives of assessing the vital signs. Describe how to assess the blood pressure. Describe how common technical errors cause inaccurate readings.
