AAPB White Paper
BIOFEEDBACK IN ESSENTIAL HYPERTENSION IN BALTIMORE, MD
Angele McGrady, Ph.D.
Blood pressure (BP) is commonly expressed as systolic over diastolic in millimeters of mercury (mm Hg). Systolic blood pressure is the maximum pressure or force that occurs when the heart contracts. Diastolic blood pressure is the minimum pressure that the blood exerts against the blood vessel walls when the heart is not contracting or beating. Blood pressure is determined by cardiac output and total peripheral resistance. Cardiac output is determined from heart rate in beats per minute multiplied by stroke volume output, which is the amount of blood ejected in one beat of the heart. Normally, blood pressure varies frequently; the changes are mediated by neural, kidney or hormone action. Neural mechanisms are responsible for rapid changes in BP while the kidney and endocrine organs modulate long term control of BP.
High blood pressure is caused by a complex interaction of behavioral, psychological, physiological and genetic factors. Essential or primary hypertension is sustained increased blood pressure of unknown cause. Most people with high blood pressure are diagnosed with essential hypertension. Other types of hypertension are produced by diseases of the kidney, tumors of the adrenal gland or diseases of the endocrine organs. All types of hypertension are diagnosed by physicians.
Treatment of essential hypertension consists of pharmacotherapy, lifestyle modifications and psychophysiological therapy including biofeedback and relaxation. For persons with moderate or severe hypertension, pharmacotherapy is the treatment of choice. Some of the types of antihypertensive drugs are diuretics, beta blockers, angiotensin-converting enzyme inhibitors and calcium channel blockers. Refer to a textbook on clinical hypertension for descriptions of each type of antihypertensive. For borderline BP and mild elevations in BP, lifestyle modification and psychophysiological therapy are logical first choices. The lifestyle modifications include weight loss, dietary changes particularly in salt and alcohol consumption, and physical exercise. Pharmacotherapy can be coupled with lifestyle modifications and psychophysiological therapy in moderate and severe hypertension.
Psychophysiological therapy can be divided into several components which are: patient education, monitoring of BP, biofeedback, relaxation, home practice and follow-up. Education of the patient includes explanation of the rationale for each component of treatment, a simple explanation of normal BP and possible reasons for elevated BP. This may be provided by written materials, video presentations or oral explanations. Repeated monitoring and recording of blood pressure for 2-4 weeks may result in decreases in blood pressure. Although the means underlying BP reduction are unknown, a lowering of patient's anxiety or desensitization to BP measurements are likely to contribute.
Several types of biofeedback have been used in treating essential hypertension. These are direct BP, electromyographic, electrodermal and thermal biofeedback. Direct blood pressure feedback involves the use of the brachial artery sounds as feedback. Patients are trained in the technique in the clinical setting and are then instructed to practice several times daily at home. Thermal biofeedback involves the patient receiving information about the temperature of their finger and using this information to warm their hands or feet. Recommended criterion for temperature is 95 degrees Fahrenheit for the finger and 93 degrees Fahrenheit for the feet.
Electromyographic feedback is designed to provide the patient with information about skeletal muscle tension, usually from the forehead or neck area. If the person learns to relax skeletal muscle, resistance to blood flow would be expected to decrease. Electrodermal feedback involves the use of a monitor of sweat gland activity usually in the hands as an indicator of generalized arousal. Patients receive electrodermal feedback and are instructed to decrease the signal, i.e., decreasing the sweating response which is known to be mediated by the sympathetic division of the autonomic nervous system.
Relaxation therapies are commonly combined with biofeedback in treatment of essential hypertension. These include progressive relaxation, autogenic relaxation, diaphragmatic breathing and Benson's relaxation response. Progressive relaxation consists of sequential tightening and loosening of specific muscle groups in the body. This assists the patient in contrasting tension and relaxation and thus facilitates relaxation. Autogenic relaxation is a passive relaxation process in which patients focus on different parts of the body, associating the sensation of heaviness and warmth with relaxation. Deep breathing training involves assisting the patient to increase the depth and decrease the frequency of breathing, particularly to breathe from the diaphragm in contrast to shallow chest breathing. Benson's relaxation response involves concentrating on a specific word or phrase in a quiet environment with the body in a relaxed posture. There is no clear evidence favoring one form of relaxation over another but one or more types of relaxation are commonly used with biofeedback therapy. Similarly, cognitive behavioral therapy may be an important part of treatment but is beyond the scope of this paper.
No matter what type of psychophysiological treatment is used, home practice of relaxation seems to be important. Frequency of relaxation practice is usually recommended at twice per day for 10-20 minutes but multiple short periods of relaxation may also be recommended. Practice involves the use of cassette tapes, simple biofeedback devices or written instructions.
Follow-up for patients who complete the clinical program is important since hypertension is a progressive disease. BP would normally increase over time as part of the aging process. Follow-up may be designed with first monthly, then every three- or six-month refresher sessions in the practitioner's office. Mailing in of blood pressures or regular phone calls may also be used. Generalization of the response to the patient's environment and maintenance of lowered BP over the long term is an essential component of treatment. Improved cognitive processing of stressful stimuli should be reinforced during follow-up of sessions.
Efficacy studies document the percent of patients lowering BP by chemically and statistically significant amounts as ranging from 50-80%. The types of patients on which biofeedback and/or relaxation therapy have been tested include unmedicated mild hypertensives, unmedicated and medicated moderate hypertensives, elderly hypertensives and pregnant hypertensives. Data on BP lowering in elderly and pregnant hypertensives is sparse but very encouraging. It is worthwhile to attempt to predict what types of hypertensive patients will respond by BP lowering. There is preliminary evidence that patients who are in a hyper aroused state as evidenced by high heart rates, high anxiety and cool hands have a better chance of success. Compliance is also an important part of patient selection. Resistance on the part of the patient to blood pressure monitoring and a high incidence of missed appointments during the early phases of treatment puts psychophysiological therapy in jeopardy.
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