Vital SignsJarvis, Chapter 9

Vital SignsClassic Vital Signs TPR/BPTemperaturePulseRespirationsBlood PressureAdditional Vital SignsHeightWeightBMI (Kg/m2) or (702Xlbs/in2)Supine, orthostatic BP

TemperatureMeasurement of metabolic activityCore vs SurfaceExerciseSize Mass to Body surface areaFat deposits insulationEnvironmentLocation, Location, LocationOral (PO)Ear (Tym)Arm pit (ax)Anal (PR)Normal values?

PulseMeasurement of Heart ActivityOne aspect of Cardiac OutputStroke Volume * Heart RateRate, regularity, qualityLocationsCommonly palpated: Carotid, Radial, Femoral, Posterior Tibial, Dorsal PedalisLess Common: Ulnar, Antecubital, PoplitealNormal Values?

RespirationMore properly ventilationMeasure of how ease of ventilation and respiratory demandRate and qualityNormal values?

Blood PressureSurrogate measure for blood flowPressure drives blood flowNecessary to push blood against gravity and keep it movingOnly affects arterial pressureVenous blood returns due to muscle contraction and valvesGenerated by heart and arteries

Blood PressureMeasurement is only as good as your instrumentInterpretation is only as good as your theorySphygmomanometers - 64% unreliable21% inaccurateAneroids 70% unreliable44% in the hospital setting 61% in private medicalMion & Pierin, (1998), J Hum Hypertens, 12(4)

Cuff-Based MeasurementRiva Rocci, 1896Korotkoff, 1905TheoryBlood flow is normally laminarCuff occludes blood flowMoment blood flow returns, cuff pressure equals arterial pressureUsual site of measurement is brachial artery

Direct MeasurementIntensive Care or SurgeryArterial line direct blood pressureUsually radial pressureCath LabVentricular pressureAortic pressure

Blood Pressure ParametersSystolic PeakDiastolic TroughMean AveragePulse AmplitudeHeart Rate Peak to Peak

JNC VII RecommendationsSeated, back supported, arms supported at heart levelRefrain from smoking or ingesting caffeine for at least thirty minutes priorRest for at least five minutes.The cuff should be of appropriate size.Two or more readings separated by two minutes should be averaged

Sources of errorBack supported 6.5 mmHg DBPArm Position dependent vs supported 10 mmHG SBP, 12 mmHG DBPAuscultatory GapAural acuity of clinicianQuality of StethoscopeClinicians bias toward subjectClinicians moodTerminal digit bias

Why should you care?5 mmHg missed (90 95)21 million peopleOver next 6 years125,000 die from CADTreating these would cause 50,000 saved lives5 mmHg extra (85 90)27 million falsely hypertensive$1000 per year per person27 billion per year

Why should you care contHTN causes 80% of Renal FailureTreatment delays RF by 4.5 yearsOne year of dialysis costs $50,000Potential savings of $225,000 per person treated

Why should you care contSeven national surveys had serious BP measurement errorsFinlandNorwayUnited StatesAustraliaEngland

Serious Errors in SurveysTerminal Digit biasDirection biasFalsification of dataFailure to follow proper protocol for calibration and technique

Defining ResourcesAHA Human Blood Pressure Determination by SphygmomanometryNational High Blood Pressure Education Program Working Meeting on Blood Pressure MeasurementNational High Blood Pressure Education Program JNC 7Last 2 are publications of NIH/NHLBI

Automated devicesAuscultatoryElectronic MicrophoneMeasures SBP, DBPOscillometricMeasures vibrationMeasures MAPDerives SBP, DBP from algorithm

Blood Pressure TheoryMean arterial pressureResponsible for perfusing bodyBP = CO*TPR (Ohms law)BP = (SV*HR)*TPR (expanded)Ohms law works only for MAP, not SBP or DBPMAP estimated from SBP & DBP(1/3)*SBP + DBP

Arterial Tree

Arterial structureCentral ArteriesAorta, CarotidElasticConduit ArteriesBrachial, FemoralMuscularArteriolesContractile

ApplicationShockDifficult to diagnose early stagesArterioles compensate for decreased cardiac outputSudden decompensation with little warning

Central Pressure drops before brachial

Ventricular-Vascular CouplingHeart does not pump against all of the bodys blood, only against what is in the aortaAorta stretches to absorb stroke volumeWhen valves close, heart relaxes, then the aorta contracts and blood flows downwardEffectDecrease systolic pressureIncrease diastolic pressureHardening of arteries causes opposite effects

Human Heart

BP ChecklistSeatedBack supportedLegs uncrossedArm supported heart levelNo caffeine or smokesStimulus free roomAppropriate cuff sizePlace cuffManometer at eye levelPalpate pulsePump cuff till pulse disappearsRelease cuffPlace stethoscopePump cuff and releaseSystolic first soundDiastolic last sound

Orthostatic Blood PressureGravity pulls blood downward to legsLess blood volume goes to headArteries contract to compensateLie down, and blood evenly distributesArteries relax to compensateStand up too quicklyGet dizzy while arteries contractNormally, takes 1 10 seconds

Orthostatic Blood Pressure ContTake BP while patient is lying downHave patient stand up and wait two minutesTake blood pressure againDifference of 10mm is considered Orthostatic hypotension

Final ConsiderationsFirst time taking BP on a new patient, take it in both armsCompare arm and leg pressures to rule out aortic coarctationNEVER, EVER take blood pressure in an arm when:Patient has a shunt or port in that armPatient had a mastectomy on that side

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