Identification of adults with true high blood pressure resistant to drugs and its relationship with breath pauses during sleep.

This study is an observational study which aims to: 1) identify individuals with true resistant hypertension (TRHT) in a population of Dunedin based adults 60 years and younger, with resistant hypertension (RHT) as defined under the current guidelines (2017) of the American Heart Association and American College of Cardiology; 2) investigate the association between TRHT and high risk of obstructive sleep apnoea (OSA) in the sub group of individuals with TRHT. Dunedin based adults, 60 years or younger, who meet the criteria for RHT (are on three or more pharmacological agents of different classes, including a diuretic), have been identified from the Ministry of Health Pharmaceutical Collection Warehouse (PCW) database. Following a briefing by researchers about the study at a scheduled meeting of the local General Practitioners Association, researchers will gain agreement from General Practitioners to distribute a letter to patients. A letter of invitation to participate in the study will be co-signed by Dr. Skinner and Associate Professor Wilkins. Letters will then be distributed to General Practitioners, who will be asked to forward copies to their patients identified from the PCW database. Step I – Initial recruitment Potential participants will be invited to contact Dr Skinner with enquiries and to indicate their interest in participating in the study. The Principal investigator (PI), the PhD candidate, will provide each participant with an appointment time for the initial assessment where written informed consent will be obtained first. The session will be at the School of Physiotherapy. Step II – Assessment and measurements Appointment 1: The PI will obtain the participant’s demographic data (age; gender; ethnicity); general health and habits, physical activity level, quality of life (SF-36) and OSA risk (ESS), using self-administered questionnaires. Participants will use a tablet computer to complete this section which will take approximately 20 minutes. Data will then be downloaded onto the study database (MS Excel). The PI will then take the participant’s resting blood pressure (office blood pressure – (BP)), heart rate, and peripheral saturation using standardised, calibrated equipment (NT1A Pulse oximeter, New Tech, Hamburg, Germany and Omron automatic digital blood pressure monitor, HEM 7322, Netherlands) and in accordance with the ACC/AHA 2017 guidelines. Next, the PI will take the anthropometric (body weight, height and circumferences of neck, waist, hip,) measurements of the participant using standard guidelines and equipment; electronic weighing scale (kg) and stadiometer (cm), measuring tape (scale in cm); with two decimal point accuracy. The equipment will be calibrated as required. This section of the procedure will take about 15 minutes. The variables, body mass index (BMI) and waist to hip ratio will be calculated using simple formulas on MS Excel. The subset with RHT who also score above or equal 9 on the Epworth Sleepiness Scale (ESS) will be identified as ‘at risk for OSA’, and will be fitted with 24h ambulatory blood pressure monitor on the non-dominant upper arm, at the Cardiology Research Laboratory, on 9th floor in Dunedin Hospital. The participant will be advised to undertake daily activities/sleep as usual over the next 24 hours. Appointment 2: On the following day, the device will be removed at the same setting, the Cardiology Research Laboratory, and data downloaded to confirm TRHT or not. Where THRT is confirmed the participant will have an echocardiogram to confirm baseline left ventricular function (results to be interpreted by co-investigator cardiologist). After the echocardiogram, the PI will conduct a Six Minute Walk Test (6MWT) following the standardised test and safety procedures. Then an activity monitor (ActiGraph GT3XPB, Pensacola, Florida) will be calibrated and placed on the non-dominant wrist to be worn for seven days/nights to determine the participant’s true levels of functional activity during the day and during sleep. The participants will select the most convenient way to return the Activitrax monitor, either in person or by post. Data will be downloaded and analysed for activity levels, and sleep parameters, by the PI. Objective measurements of daytime activity (step count, time in low/moderate/vigorous physical activity, sedentary time and sleep, including total sleep time, awakenings, average awakenings, sleep efficiency, sleep onset, latency and wake after sleep onset) will be derived from the Actigraph calculator for the period. The PI who will then determine the correlation between Epworth Sleepiness Scale score and sleep fragmentation and subsequently identify those with high risk of OSA in the subset with TRHT. Note: Participants not found to have TRHT will meet with the co-investigator (Primary Supervisor) to discuss the outcomes and will be advised to visit their GP to discuss the report on findings for 24hABPM, risk of OSA (obtained from the questionnaire, ESS above or equal to 9), and self-reported physical activity level). The participants with objective signs of OSA scored from the data downloaded from the activity monitor but not with TRHT will be referred by the co-investigator cardiologist, to the physician at the Sleep Clinic for further sleep analysis. Individuals who have TRHT and high risk of OSA will be invited to participate in a second study: a feasibility study to investigate the outcomes of a supervised physical activity programme on blood pressure levels.