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

1. CME Program for Family PhysiciansAmbulatory BP MonitoringBrian Gore, MD CCFP Dip Epid. 2004 Series

2. CME Program for Family PhysiciansAmbulatory BP MonitoringBrian Gore, MD CCFP Dip Epid.Part IEpidemiology OBP Measurement

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

4. Canadian data on hypertension: • 22% PREVALENCE (4.2 million people) • 16% are controlled (<140/90) 39% (40%) • 23% treated but not controlled (60%) • 19% aware but not treated 61% • 42% are unaware Adapted from: Am J Hypertens 1997; 10:1097-1102.

5. What are the controversies in office blood pressure measurements?

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

7. Observer Bias • habitually reading higher or lower than actual pressure • terminal digit preference (150/90) • bias for normal values • prejudice against certain values • variable speed of observer reaction • differences in interpretation of Korotkoff sounds • Bailey RH, Arch Int Med: 1993, 152:2741-2748 • Pickering TG, Lancet:1994,344:31-35

8. Technique Failures • no rest period prior to BP measure • one arm, one position measures • inappropriate cuff size • poor environmental control: talking, tense. • inappropriate rate of deflation • Bailey RH, Arch Int Med: 1993, 152:2741-2748 • Pickering TG, Lancet:1994,344:31-35

9. Equipment Error • mercury devices not calibrated or faulty components • aneroid devices as above • mechanical and electrical devices: numerous potential problems • Bailey RH, Arch Int Med: 1993, 152:2741-2748 • Pickering TG, Lancet:1994,344:31-35

10. CHS Recommended Technique for Measuring BP

12. Recommended Technique for Measuring Blood Pressure (cont.) • • 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

13. 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)

14. THE PINHOLING EFFECT OF OBP MEASUREMENT

15. Casual OBP: representative?

16. Casual OBP: representative?

17. Casual OBP: representative?

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

19. Casual Blood Pressure“just the tip of the iceberg”

20. 24 hour ABP: representative?

21. Perloff et al. 1983 Zweiker et al. 1994 Ohkubo et al. 1997 Nakano et al. 1998 Yamamoto et al. 1998 Redon et al. 1998 Verdecchi et al. 1998 Khattar et al. 1999 Staessen et al. 1999 Verdecchi et al. 2002 Event-Based Cohort Studies with ABPMcardiovascular disease risk ABP > OBP

22. 24 HOUR ABPM

23. Which BP is representative?

24. Which BP is representative?

25. Inherent Variability of BP

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

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

28. Implications Inaccurate Diagnosis Inappropriate Treatment