Heart Biomarker Evaluation in Apnea Treatment

7.1 Overview

24 hour BP provides the ability to detect people whose blood pressure rises or does not fall during sleep as would be normally expected. (These individuals are called “non-dippers.”) Repeated BP over the course of the day and night also may provide a more reliable measure of BP than from one or two reading made during the day.

Systolic and diastolic BP will be continuously monitored (every 30 minutes) using an automated oscillometric monitor (model 90217; Spacelabs Inc., Redmond, Washington, USA) over a 24 hour period on 2 occasions; at baseline and the month 3 visit. At the end of those visits, prior to leaving the clinic, the blood pressure monitor and cuff will be placed and worn for the 24 hour period. Clear instructions will be given to the participant.

Specifically, participants will be instructed to avoid contact sports and swimming during the day of the recording and to keep a diary that reflects their daily activities and sleep time over the 24 hour period. A return prepaid mailer will be provided to each participant or a courier service may be used. Participants will sign an agreement to return the monitor as soon as the study is completed.

The following parameters will be compared between groups:

1. Mean diurnal systolic, diastolic and mean BP
2. Mean nocturnal systolic, diastolic and mean BP
3. Mean 24 hour BP
4. BP dipping defined as the difference between mean awake and sleep systolic, diastolic and mean BP expressed as a percentage of awake measurement.
5. Blood pressure variability measured as BP SD / variance
6. Mean heart rate and heart rate variability AMBP MOP