CME Program for Family Physicians Ambulatory BP Monitoring Brian Gore, MD CCFP Dip Epid. CME Program for Family Physicians Ambulatory BP Monitoring Brian Gore, MD CCFP Dip Epid Series

CME Program for Family Physicians Ambulatory BP Monitoring Brian Gore, MD CCFP Dip Epid. Part I Epidemiology OBP Measurement

PREVALENCE of HIGH BLOOD PRESSURE PREVALENCE of HIGH BLOOD PRESSURE Whole Population 15% Subjects > 65 years 30%

Canadian data on hypertension : 22% PREVALENCE (4.2 million people) 22% PREVALENCE (4.2 million people) 16% are controlled (<140/90) 39% (40%) 16% are controlled (<140/90) 39% (40%) 23% treated but not controlled (60%) 23% treated but not controlled (60%) 19% aware but not treated 61% 19% aware but not treated 61% 42% are unaware 42% are unaware Adapted from: Am J Hypertens 1997; 10:

What are the controversies in office blood pressure measurements?

Common Errors in Blood Pressure Evaluation Observer Bias Observer Bias Technique Failures Technique Failures Equipment Error Equipment Error

Observer Bias habitually reading higher or lower than actual pressure habitually reading higher or lower than actual pressure terminal digit preference (150/90) terminal digit preference (150/90) bias for normal values bias for normal values prejudice against certain values prejudice against certain values variable speed of observer reaction variable speed of observer reaction differences in interpretation of Korotkoff sounds differences in interpretation of Korotkoff sounds Bailey RH, Arch Int Med: 1993, 152: Bailey RH, Arch Int Med: 1993, 152: Pickering TG, Lancet:1994,344:31-35 Pickering TG, Lancet:1994,344:31-35

Technique Failures no rest period prior to BP measure no rest period prior to BP measure one arm, one position measures one arm, one position measures inappropriate cuff size inappropriate cuff size poor environmental control: talking, tense. poor environmental control: talking, tense. inappropriate rate of deflation inappropriate rate of deflation Bailey RH, Arch Int Med: 1993, 152: Bailey RH, Arch Int Med: 1993, 152: Pickering TG, Lancet:1994,344:31-35 Pickering TG, Lancet:1994,344:31-35

Equipment Error mercury devices not calibrated or faulty components mercury devices not calibrated or faulty components aneroid devices as above aneroid devices as above mechanical and electrical devices: numerous potential problems mechanical and electrical devices: numerous potential problems Bailey RH, Arch Int Med: 1993, 152: Bailey RH, Arch Int Med: 1993, 152: Pickering TG, Lancet:1994,344:31-35 Pickering TG, Lancet:1994,344:31-35

CHS Recommended Technique for Measuring BP

Patient seated, feet on floor, back against wall Position 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.)

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 apart Measure BP in both arms, different positions Repeated visits (3-5)

THE PINHOLING EFFECT OF OBP MEASUREMENT

Casual OBP: representative?

CASUAL OFFICE READINGS repeated visits, blood pressure variability, common errors

Casual Blood Pressure “just the tip of the iceberg”

24 hour ABP: representative?

Event-Based Cohort Studies with ABPM cardiovascular disease risk ABP > OBP Perloff et al Perloff et al Zweiker et al Zweiker et al Ohkubo et al Ohkubo et al Nakano et al Nakano et al Yamamoto et al Yamamoto et al Redon et al Verdecchi et al Khattar et al Staessen et al Verdecchi et al. 2002

24 HOUR ABPM

Which BP is representative?

Inherent Variability of BP

Reflective moment.….. Daily average no. of heartbeats: 103,680 Daily average no. of heartbeats: 103,680 No of beats per OBPM: <15 No 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 visits Clinical decision in 3 to 5 office visits Include the BP variability Include the BP variability Include the other common errors in BP measurement Include the other common errors in BP measurement Include the concept of WCE/WCH Include the concept of WCE/WCH

What is your level of confidence that you have representative BP measurements upon which you can make a clinical and therapeutic decision??

Inaccurate Diagnosis Implications Inappropriate Treatment Inappropriate Treatment