Home Monitoring Service Improves Mean Arterial Pressure in Patients with Essential Hypertension

Although the use of telecommunication systems in medicine has been increasing, few trials have assessed the efficacy of such technology for improving blood pressure in patients with essential hypertension (1, 2). Friedman and colleagues (1) found that when hypertensive patients used a telephone-linked computer system to report blood pressure, diastolic blood pressure decreased significantly. Bondmass and colleagues (2) also found a significant decrease in both diastolic and systolic blood pressure, although their trial lacked controls. In these studies and in other trials of home monitoring, self-report of blood pressure was the basic mechanism for transmission of information to physicians (1-8). This may have consequences for patient care, since it has recently been shown that patients often erroneously report blood pressure, especially patients whose blood pressure is uncontrolled (9). Johnson and colleagues (9) found that in approximately 20% of instances, self-report of blood pressure differed from the electronic reading by more than 10 mm Hg. Another limitation of previous trials is accurate assessment of the outcome. In some studies, the outcome was determined by one or two blood pressure readings taken during an office visit or by a technician in the home setting (1, 4-7). Only one study of 31 patients used automatic ambulatory blood pressure monitoring (ABPM) to assess usual blood pressure at baseline and exit (3). Twenty-fourhour ABPM recordings yield a more reliable assessment of usual blood pressure levels during the course of daily activities (10). To improve on the previous studies, we designed a randomized, controlled trial that used 24-hour ABPM measurements at baseline and at exit to determine change in blood pressure more accurately. The intervention was a service provided to physicians that used electronic transmission of results and did not rely on self-report of blood pressure. Methods Study Protocol From May 1999 to April 2000, five internists from the Department of Medicine at the State University of New York Upstate Medical University in Syracuse recruited patients from internal medicine outpatient practices affiliated with the general medicine division. Outpatients seen by these physicians were covered by private insurance plans or Medicare. Eligible patients were adults who had previously received a diagnosis of essential hypertension and were under evaluation for a change in antihypertensive therapy because of 1) elevated blood pressure [systolic pressure 140 or diastolic pressure 90 mm Hg] despite current antihypertensive therapy, 2) undesirable side effects of current antihypertensive medication, or 3) office systolic pressure of at least 180 mm Hg or diastolic pressure of at least 110 mm Hg with no current use of antihypertensive medication. For patients with diabetes mellitus, heart disease, stroke, nephropathy, peripheral arterial disease, or hypertensive retinopathy, an office systolic pressure of at least 130 mm Hg or an office diastolic pressure of at least 85 mm Hg was a criterion for eligibility. Patients who were younger than 18 years of age, were pregnant, had secondary hypertension, or did not have the mental or physical capacity to monitor blood pressure at home were excluded. All patients were informed of the study procedures, the risks and benefits of participation, confidentiality, rights, and personnel to contact for additional information. The institutional review board at Upstate Medical University approved the trial, and all patients gave written consent before participation. Patients received printed educational materials on nonpharmacologic approaches to blood pressure control from the National Heart, Lung, and Blood Institute (11). These approaches included reducing weight, increasing physical activity, and changing diet if necessary. At baseline, height and weight were recorded at the clinic for all patients. Body mass index was calculated as kg/m2. Printed information on the treatment of hypertension from the Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (National High Blood Pressure Education Program) (12) was available at each clinical site as a reference for physicians and clinical staff. Study Group Assignment We conducted a randomized trial with concurrent controls. The two study groups were home service and usual care. To ensure an equal number of patients in both study groups, we used a blocking procedure with random permuted blocks of varying size to reduce predictability. Randomization was stratified by the number of prescription medications patients were taking (0 to 2 or 3) at study entry, which served as a general indicator of morbidity. Sequentially numbered, sealed, opaque envelopes were used for assignment. The randomization procedure was concealed to physicians and clinical research staff, but physicians, investigators, and patients were aware of group assignment when randomization was complete. In addition, adherence to the protocol was monitored independently of the clinicians. A priori sample size was calculated to detect a mean (SD) difference in blood pressure of 3 5 mm Hg between the two study groups. This yielded 60 patients per group with 90% power ( = 0.05 [two-tailed]). Intervention The intervention was a telecommunication service consisting of three components: automatic blood pressure recording at home, central processing, and electronic reports provided weekly to the primary physician and patient. We used a home blood pressure monitoring device that transmitted data over analog telephone lines (Model 52500, Welch Allyn, Inc., Skaneateles Falls, New York) and was validated according to the standards of the American National Standard Institute, Inc., and the Association for the Advancement of Medical Instrumentation (13). The oscillometric device (16.26 cm 10.92 cm 6.6 cm) had a digital display for blood pressure and pulse and used automatic pressurization and exhaust for cuff inflation and deflation. Patients were instructed to take their blood pressure three times in the morning before eating or drinking and three times in the evening before going to bed. After each reading, the device automatically dialed the Service and Support Center at Welch Allyn and transmitted the data. Patients were asked to conduct this routine at least three days each week for a minimum of 8 weeks and could take additional readings if they desired. A computer program was developed to display the results in a report form, which was then faxed to each patient's physician. The report form contained information on the mean systolic pressure, mean diastolic pressure, and heart rate (overall, morning, and evening). It also graphed the pressure by date and displayed individual readings in tabular form. Both physicians and patients received a report form each week, as well as a summary report form at the end of the trial. When physicians received report forms that indicated elevated pressure, they adjusted antihypertensive medications through a telephone call, an office visit, or both. At the time of the trial, the service cost $24.95 per month. Patients assigned to usual care were treated for hypertension according to the guidelines of the Joint National Committee on Prevention, Detection, and Treatment of High Blood Pressure (12). Questionnaire Information Information about patients' medical histories, past diagnoses of disease, and use of medications was obtained from questionnaires. The Baecke questionnaire of habitual physical activity was used to assess usual activity levels (14). Subscales included a work index, a sports index, and a nonsports leisure index, as well as a total physical activity score. Dietary intake was estimated by using the Block screening questionnaire, which consists of two subscales: intake of highly saturated fatty foods and intake of fruit, vegetables, and high-fiber grains (15). Questions about smoking and stress were taken from the previously validated Health Habits and History Questionnaire (16). The study questionnaire was collected at the time of the second 24-hour ambulatory readings. Outcome Measures The primary end point was the change in mean arterial pressure during the trial (baseline to exit) for home service compared with usual care. A clinical research nurse (the study manager) fitted participants with a 24-hour ABPM device at baseline and at exit. The nurse gave the patients detailed instructions for using the device. The ABPM device automatically recorded blood pressure every half-hour from 7:00 a.m. to 11:00 p.m. and every hour from 11:00 p.m. to 7:00 a.m. Information from baseline and exit ABPM readings was given to physicians only after the patient exited the trial. All blood pressure measurements indicated in this report refer to these 24-hour readings. Means and SDs were recorded for systolic pressure, diastolic pressure, arterial pressure, and heart rate by using 24-hour ABPM. Mean arterial pressure was measured as (diastolic pressure + 1/3 [systolic pressure diastolic pressure]). The ABPM device also recorded the percentage of readings above the desired target levels ( 140 mm Hg systolic or 90 mm Hg diastolic for patients without target organ damage; 130 mm Hg systolic or 85 mm Hg diastolic for patients with target organ damage). Patients were scheduled to remain in the trial for a minimum of 8 weeks. During the sixth and seventh weeks, appointments were made to schedule second 24-hour ABPM sessions. For both the home service and usual care groups, the median time from baseline to exit was 11 weeks. The final patient receiving usual care exited at 20 weeks, and the final patient receiving home service exited at 28 weeks. Statistical Analysis All information was entered into an Excel database (Microsoft Corp., Redmond, Washington) and was manually rechecked for errors. Statistical analyses were conducted by using STATISTICA software (St