CME Program for Family CME Program for Family

PhysiciansPhysicians

Ambulatory BP MonitoringAmbulatory BP Monitoring

Brian Gore, MD CCFP Dip Epid.Brian Gore, MD CCFP Dip Epid.

2004 Series 2004 Series

CME Program for Family CME Program for Family

PhysiciansPhysicians Ambulatory BP Ambulatory BP

MonitoringMonitoring

Brian Gore, MD CCFP Dip Epid.Brian Gore, MD CCFP Dip Epid.

Part IPart IEpidemiology Epidemiology

OBP Measurement OBP Measurement

PREVALENCE PREVALENCE ofof

HIGH BLOOD PRESSURE HIGH BLOOD PRESSURE

Whole Population Whole Population 15%15%

Subjects > 65 years Subjects > 65 years 30%30%

Canadian data on Canadian data on hypertensionhypertension::

22% PREVALENCE 22% PREVALENCE (4.2 million people)(4.2 million people)

16% are controlled (<140/90) 16% are controlled (<140/90) 39% 39% (40%)(40%)

23% treated but not controlled 23% treated but not controlled (60%)(60%)

19% aware but not treated 19% aware but not treated 61%61%

42% are unaware42% are unaware

Adapted from: Adapted from: Am J HypertensAm J Hypertens 1997; 10:1097-1102. 1997; 10:1097-1102.

What are the controversies in What are the controversies in office blood pressure office blood pressure

measurements?measurements?

Common Errors in Blood Common Errors in Blood Pressure EvaluationPressure Evaluation

Observer BiasObserver Bias Technique FailuresTechnique Failures Equipment ErrorEquipment Error

Observer BiasObserver Bias

habitually reading higher or lower than habitually reading higher or lower than actual pressureactual pressure

terminal digit preference (150/90)terminal digit preference (150/90) bias for normal valuesbias for normal values prejudice against certain valuesprejudice against certain values variable speed of observer reactionvariable speed of observer reaction differences in interpretation of Korotkoff differences in interpretation of Korotkoff

soundssounds Bailey RH, Arch Int Med: 1993, 152:2741-2748Bailey RH, Arch Int Med: 1993, 152:2741-2748 Pickering TG, Lancet:1994,344:31-35Pickering TG, Lancet:1994,344:31-35

Technique FailuresTechnique Failures

no rest period prior to BP measureno rest period prior to BP measure one arm, one position measuresone arm, one position measures inappropriate cuff sizeinappropriate cuff size poor environmental control: talking, tense.poor environmental control: talking, tense. inappropriate rate of deflationinappropriate rate of deflation

Bailey RH, Arch Int Med: 1993, 152:2741-2748Bailey RH, Arch Int Med: 1993, 152:2741-2748 Pickering TG, Lancet:1994,344:31-35Pickering TG, Lancet:1994,344:31-35

Equipment ErrorEquipment Error

mercury devices not calibrated or faulty mercury devices not calibrated or faulty componentscomponents

aneroid devices as aboveaneroid devices as above mechanical and electrical devices: mechanical and electrical devices:

numerous potential problemsnumerous potential problems

Bailey RH, Arch Int Med: 1993, 152:2741-2748Bailey RH, Arch Int Med: 1993, 152:2741-2748 Pickering TG, Lancet:1994,344:31-35Pickering TG, Lancet:1994,344:31-35

CHS Recommended Technique CHS Recommended Technique for Measuring BPfor Measuring BP

2000 Canadian Recommendations for the Management of Hypertension

Recommended Technique for Measuring Blood Pressure

Standardized technique:

• Have the patient rest for 5 minutes

• Use an appropriate cuff size

• Use a mercury manometer or a recently calibrated electronic device

• Patient seated, feet on floor, back against wallPosition cuff appropriately• Increase pressure rapidly• Support arm at heart level• Exclude possibility of auscultatory gap by increasing cuff pressure rapidly to 30 mmHg above level of disappearance of radial pulse• Place stethoscope over the brachial artery

Recommended Technique for Measuring Blood Pressure (cont.)

Recommended Technique for Measuring Blood Pressure (cont.)

• Drop pressure by 2 mmHg / beat:- appearance of sound (phase I Korotkoff) = SBP- disappearance of sound (phase V Korotkoff) =

DBP• Take 2 blood pressure measurements, 1 minute apartMeasure BP in both arms, different positionsRepeated visits (3-5)

THE PINHOLING EFFECT THE PINHOLING EFFECT OF OBP MEASUREMENTOF OBP MEASUREMENT

Casual OBP: representative?

Casual OBP: representative?

Casual OBP: representative?

CASUAL OFFICE CASUAL OFFICE READINGSREADINGS

repeated visits, blood pressure repeated visits, blood pressure variability, common errorsvariability, common errors

Casual Blood PressureCasual Blood Pressure

“just the tip of the iceberg”“just the tip of the iceberg”

24 hour ABP: representative?

Event-Based Cohort Studies Event-Based Cohort Studies with ABPMwith ABPM

cardiovascular disease risk ABP > OBPcardiovascular disease risk ABP > OBP

Perloff et al. 1983Perloff et al. 1983 Zweiker et al. 1994Zweiker et al. 1994 Ohkubo et al. 1997Ohkubo et al. 1997 Nakano et al. 1998Nakano et al. 1998 Yamamoto et al. 1998Yamamoto et al. 1998

Redon et al. 1998Redon et al. 1998 Verdecchi et al. 1998Verdecchi et al. 1998 Khattar et al. 1999Khattar et al. 1999 Staessen et al. 1999Staessen et al. 1999 Verdecchi et al. 2002Verdecchi et al. 2002

24 HOUR ABPM24 HOUR ABPM

Which BP is representative?Which BP is representative?

Which BP is representative?Which BP is representative?

Inherent Variability of BP

Reflective moment.…..Reflective moment.…..• Daily average no. of heartbeats: 103,680 Daily average no. of heartbeats: 103,680 • No of beats per OBPM: <15No of beats per OBPM: <15• Sampling ratio is 1:6912 or .0145%Sampling ratio is 1:6912 or .0145%• Clinical decision in 3 to 5 office visitsClinical decision in 3 to 5 office visits• Include the BP variabilityInclude the BP variability• Include the other common errors in BP Include the other common errors in BP

measurementmeasurement• Include the concept of WCE/WCHInclude the concept of WCE/WCH

What is your level of What is your level of confidence that you have confidence that you have

representative BP representative BP measurements upon which you measurements upon which you

can make a clinical and can make a clinical and therapeutic decision??therapeutic decision??

Inaccurate DiagnosisInaccurate Diagnosis

ImplicationsImplications

Inappropriate TreatmentInappropriate Treatment