Blood Pressure Measurement: Should Technique Define Targets?

Hypertension is the single most important risk factor for cardiovascular disease and death. Over the last several decades many classes of blood pressure lowering drugs have been discovered. These allow physicians to achieve optimal blood pressure and prevent adverse cardiovascular outcomes in most patients. However, the optimal blood pressure level has changed over time, and most recently has been decreased to 120 mm Hg, on the basis of clinical trials. These trials used a specific rigorous method of blood pressure measurement (patient alone in room, enforced period of rest, average of multiple readings) that is currently not the standard of practice in most clinics. Blood pressure itself is highly influenced by technique and device. In particular the length of resting time (if any), and whether it is measured with device requiring medical personnel presence in the room or not. For the same individual, the difference between blood pressure taken with and without rest could be 10 mmHg, and presence vs absence of medical personnel in the room during rest and/or BP assessment could be another 10 mmHg. Hence, the target blood pressure could vary materially based on BP technique and device used. As it is unlikely that all physicians can change their practice overnight and embrace blood pressure device allowing for standard resting time and unattended blood assessment, a comparative pragmatic study of the blood pressure technique and devices endorsed by Hypertension Canada and used in Canada is desirable to avoid either over- or under-treatment of Canadian patients with hypertension.

In the present study, the investigators will compare 4 different methods of measuring blood pressure in the office (casual, resting average of 3 readings with nurse present or absent for resting period, and average of 5 readings) as well as a 24 hour ambulatory measurement in 90 patients. The results of this study will help and enable practicing family physicians and specialists in Canada to target BP for their patients based on algorithm and method of assessment of BP they use in their offices.

Inclusion criteria

• All patients being followed in the Renal Hypertension Clinic will be eligible for enrollment

Exclusion criteria

• Inability to do oscillometric measures (eg., arrhythmia, pain, device reporting error)
• inability to consent the patient