Pediatric Annals

Biofeedback

Mark S Smith, MD

Abstract

Biofeedback is a useful form of adjunctive therapy for many psychophysiologic conditions in children and adolescents. A little over 20 years ago a surge in interest occurred in the application of physiological self- monitor ing devices toward medical conditions. In addition to the training of voluntary skeletal muscle, learned control of autonomie nervous system responses was reported. Although not fully replicated in subsequent studies, in 1969 a fascinating report by Miller described opérant conditioning of such autonomie nervous system functions as heart rate, blood pressure, intestinal motility, urine production rate, and gastric and peripheral blood flow in the curarized rat.1 The optimistic tone of early biofeedback experimentation seemed to state: Any biological function that can be monitored and presented to the individual in a comprehensible manner (feedback) is subject to self-control!

After a decade of mainly anecdotal reports, more rigorous scientific research began to temper the initial optimism. Subsequently, knowledge of biofeedback efficacy has been enhanced by studies employing proper control groups, standardized treatment approaches, criteria to define training effect, and followup evaluation to demonstrate maintenance of clinical improvement. The current body of research suggests that the application of biofeedback may be useful in many clinical conditions, although there appear to be few conditions in which biofeedback is demonstrably superior to other behavioral techniques such as relaxation training, hypnosis, or meditation.2,3

With the exception of a few specific indications (eg, electromyographic training of the external rectal sphincter), the major clinical effect of biofeedback training may be more generalized than specific in promoting physiological homeostasis. Elucidation of the actual mechanisms opérant in effective clinical biofeedback training frequently is confounded by findings that do not support a direct relationship between symptom amelioration and changes in the monitored variable (eg, fingertip temperature and frontalis voltage). In fact, several studies using either false biofeedback or promoting physiological change that is counterintuitive to that which would be expected to promote symptom improvement have produced positive clinical results."1'5

Debate continues as to whether biofeedback results in clinical improvement by means of specific visceral or skeletal muscular training or through another mechanism such as generalized relaxation or cognitive change.6'7 For example, improvement in headache activity following biofeedback training might reflect learned control of servomotor mechanisms affecting blood flow, skeletal muscular relaxation, or an improved sense of mastery and control promoted by successful biofeedback performance. The latter might change coping style and perhaps even alter the physiologic response of the limbic system (visceral brain) to stressful cognitions. Finally, many studies purporting to show no advantage of biofeedback training over other behavioral therapies have oversimplified data, failed to recognize individual differences, or suffered from low statistical power (ie, not enough subjects) and may therefore not be sensitive enough to detect actual differences in treatment efficacy between groups.

In summary, it appears that biofeedback training can be effective in many clinical situations. It is not always clear, however, that this efficacy is directly related to a specific effect of biofeedback training. Other mechanisms such as generalized relaxation or cognitive change may be operant. Clinical experience suggests that when a child or adolescent recognizes that self-control of a physiologic response previously held to be autonomous is being demonstrated via biofeedback, enhancement of perceived coping skills ensues. Individual patient variables such as perception of treatment credibility, expectation of symptom reliei sense of self-efficacy, motivation to receive treatment, capacity for absorption, and compliance with practice also may be important. In clinical pediatrie practice, it is useful to have several behavioral strategies available for the individual patient. Some children and adolescents prefer biofeedback training over other modalities such as progressive muscular relaxation, meditation, or…

Biofeedback is a useful form of adjunctive therapy for many psychophysiologic conditions in children and adolescents. A little over 20 years ago a surge in interest occurred in the application of physiological self- monitor ing devices toward medical conditions. In addition to the training of voluntary skeletal muscle, learned control of autonomie nervous system responses was reported. Although not fully replicated in subsequent studies, in 1969 a fascinating report by Miller described opérant conditioning of such autonomie nervous system functions as heart rate, blood pressure, intestinal motility, urine production rate, and gastric and peripheral blood flow in the curarized rat.1 The optimistic tone of early biofeedback experimentation seemed to state: Any biological function that can be monitored and presented to the individual in a comprehensible manner (feedback) is subject to self-control!

After a decade of mainly anecdotal reports, more rigorous scientific research began to temper the initial optimism. Subsequently, knowledge of biofeedback efficacy has been enhanced by studies employing proper control groups, standardized treatment approaches, criteria to define training effect, and followup evaluation to demonstrate maintenance of clinical improvement. The current body of research suggests that the application of biofeedback may be useful in many clinical conditions, although there appear to be few conditions in which biofeedback is demonstrably superior to other behavioral techniques such as relaxation training, hypnosis, or meditation.2,3

With the exception of a few specific indications (eg, electromyographic training of the external rectal sphincter), the major clinical effect of biofeedback training may be more generalized than specific in promoting physiological homeostasis. Elucidation of the actual mechanisms opérant in effective clinical biofeedback training frequently is confounded by findings that do not support a direct relationship between symptom amelioration and changes in the monitored variable (eg, fingertip temperature and frontalis voltage). In fact, several studies using either false biofeedback or promoting physiological change that is counterintuitive to that which would be expected to promote symptom improvement have produced positive clinical results."1'5

Debate continues as to whether biofeedback results in clinical improvement by means of specific visceral or skeletal muscular training or through another mechanism such as generalized relaxation or cognitive change.6'7 For example, improvement in headache activity following biofeedback training might reflect learned control of servomotor mechanisms affecting blood flow, skeletal muscular relaxation, or an improved sense of mastery and control promoted by successful biofeedback performance. The latter might change coping style and perhaps even alter the physiologic response of the limbic system (visceral brain) to stressful cognitions. Finally, many studies purporting to show no advantage of biofeedback training over other behavioral therapies have oversimplified data, failed to recognize individual differences, or suffered from low statistical power (ie, not enough subjects) and may therefore not be sensitive enough to detect actual differences in treatment efficacy between groups.

In summary, it appears that biofeedback training can be effective in many clinical situations. It is not always clear, however, that this efficacy is directly related to a specific effect of biofeedback training. Other mechanisms such as generalized relaxation or cognitive change may be operant. Clinical experience suggests that when a child or adolescent recognizes that self-control of a physiologic response previously held to be autonomous is being demonstrated via biofeedback, enhancement of perceived coping skills ensues. Individual patient variables such as perception of treatment credibility, expectation of symptom reliei sense of self-efficacy, motivation to receive treatment, capacity for absorption, and compliance with practice also may be important. In clinical pediatrie practice, it is useful to have several behavioral strategies available for the individual patient. Some children and adolescents prefer biofeedback training over other modalities such as progressive muscular relaxation, meditation, or self-hypnosis, even though biofeedback training usually incorporates one or more of these modalities in the overall program. Additionally, electronic instrumentation with its scientific aura may promote interest and expectation of symptom relief in some individuals. Auditory feedback and visual display may be preferred over silent, internalized behavioral techniques.

EQUIPMENT AND METHODOLOGY

Biofeedback training can use techniques as simple as self-monitoring of pulse for essential hypertension to electroencephalographic (EEG) feedback for seizure control. Galvanic skin response, plethysmography, electromyography (EMG), and peripheral skin temperature monitoring are common modalities employed in biofeedback practice. In most clinical situations, EMG and skin temperature biofeedback are practical and used most often.

Electromyography biofeedback units measure the amount of electrical discharge in muscle fibers, transform the raw EMG signal into more meaningful information through the use of integration techniques, and provide a biofeedbacfc signal with a direction that is directly proportional to the amount of electrical activity in the monitored muscle group. A typical dual channel EMG biofeedback unit with preamplifiers and electrodes costs approximately $1500 (J and J Engineering Ine, Poulsbo, Washington). Skin temperature biofeedback equipment most frequently uses a small transducer (thermistor) attached to the skin, which detects temperature change induced by alterations of blood flow. The sensitivity and range of continuous skin temperature biofeedback can be modified by these devices in order to facilitate training at a level appropriate for the biofeedback subject. A typical dual channel skin temperature biofeedback unit with sensors costs approximately $800 (J and J Engineering Ine, Poulsbo, Washington). More expensive modular units allowing interface with computers are available from most biofeedback equipment manufacturers. Software programs have been designed that allow the biofeedback information to be presented in graphic or game format. Although an untested hypothesis, it is possible that computer game biofeedback enhances patient interest and compliance with the biofeedback program.

The application of a successful clinical biofeedback treatment program requires skill on the part of the therapist. The Association for Applied Psychophysiology and Biofeedback is instrumental in the publication of Biofeedback and Self-Regulation, a quarterly interdisciplinary journal dealing with relevant aspects of psychology, physiology, and cybernetics, and the certification of biofeedback therapists. Although the underlying mechanism of biofeedback training remains unknown, it is clear that treatment credibility, motivation, compliance, reinforcement, and enhancement of feelings of mastery and control are important variables in the clinical biofeedback setting. Simply providing patients with an electronic device and instructing them to learn self-control over the monitored physiological variable is rarely successful in reducing symptoms. Particularly with children, it is important for the biofeedback therapist to ascertain which modality will capture the interest and motivation to practice of the individual patient.

Although practice varies, most biofeedback treatment programs employ 4 to 12 biofeedback sessions that are 30 to 45 minutes in length. The amount and length of treatment is variable and depends on the individual, the clinical problem, and the response to treatment. Although it is extremely difficult to sort out issues of reinforcement and compliance, several studies have suggested that brief clinic instruction followed by home practice may provide adequate treatment for some clinical problems. In standard practice, clinic-based biofeedback visits are intended to provide information for the patient regarding self-induced physiologic change. This new awareness may then be applied to home practice of nonbiofeedback based techniques such as progressive muscular relaxation, meditation, or relaxation and mental imagery (self- hypnosis). The patient who does not practice at home between weekly biofeedback visits probably will not show significant improvement in the clinical problem.

A typical biofeedback session with EMG and skin temperature monitoring begins with a brief baseline period for stabilization. With EMG biofeedback, the therapist may ask the patient to reduce the signal from the monitored muscle group as much as possible. Most patients find with EMG monitoring they are able to achieve lower voltage potentials on the monitored groups than without the feedback. The patient also may be asked to maintain low EMG potentials during the application of a Stressor such as visualizing an extremely embarrassing moment or performing serial seven subtraction. Discrimination training also may be introduced by asking the patient to provide a given level of EMG potential without a feedback signal and then providing the signal for comparison. After a few EMG training sessions, most children and adolescents are able to provide fairly accurate EMG potentials on command without feedback.

Peripheral skin temperature biofeedback usually involves placing the thermistor on a fingertip or the dorsal aspect of the hand. After a baseline that is long enough to provide stabilization of temperature, the patient is asked to either warm or cool the monitored hand. Most children and adolescents are able to learn this skill after several skin temperature biofeedback sessions. The manner in which this skill is performed is ineffable. It appears that "passive volition" is key to success. Therefore, an intensely competitive individual who seeks with extreme vigor to warm the hand may merely increase sympathetic nervous system discharge, vasoconstrict, and drop the temperature. In the usual clinical setting, the patient is asked to warm the hand as much as possible. The therapist may provide suggestions such as imagining the hand in warm water, but children and adolescents choose a variety of different strategies such as relaxation, imagery, or attention to the biofeedback signal.8 Vasodilatation during skin temperature biofeedback can be quite dramatic with increases of 10° to 25° Fahrenheit, and the cognition of enhanced mastery and control during this process may be profound. Since regulation of vasomotor tone and not merely vasodilatation may be important in learned autonomie nervous system control, some therapists include hand cooling in the treatment program.

It is important during biofeedback training to define target symptoms and monitor them closely. Symptom diaries and treatment compliance logs allow the therapist to determine progress and provide appropriate instruction and encouragement for the patient. Galvanic skin response and skin temperature home biofeedback trainers are available in the $100 price range (Thought Technology Ltd, Montreal, Canada), but in most clinical settings they probably are not necessary. A simple liquid crystal temperature band may provide reinforcement for some patients (Bio-Temp Products Ine, Indianapolis, Indiana). Home practice of an individualized behavioral technique such as a progressive muscular relaxation or self-hypnosis are probably the most important factors in treatment success. Continued therapist monitoring of treatment compliance and troubleshooting for any difficulties or lack of motivation is essential.

Because the cognition of mastery and control may be an important factor in successful behavioral treatment, it is important that the child or adolescent (not the parent) be the focus of training efforts. Frequently, parents or referring health professionals request biofeedback training for children and adolescents. It is therefore important for the therapist to determine that the patient is adequately motivated and perceives the treatment as credible and appropriate. While maintaining a stance of support and encouragement to practice, the parent should not be responsible for treatment compliance. Excessive parental involvement in treatment may result in additional stress for the child or adolescent and may actually undermine efforts to enhance cognitions of mastery and control. After successful biofeedback training and resolution of clinical symptoms, it is not clear how much continued practice is necessary for maintenance of improvement. In many clinical situations, it appears that less intensive continued practice is adequate and occasional booster sessions may enhance long-term outcome.

CLINICAL APPLICATIONS

Headache

Numerous reports have indicated that biofeedback training is useful in the treatment of recurrent pediatrie headache.9 Doubt has been cast on the specificity theories of muscle contraction and vascular headache, and it is probable that tension and migraine headaches involve changes in both muscular and vascular tone. Therefore, it is rational in the treatment of recurrent pediatrie headache to employ both EMG and skin temperature biofeedback. Both types of pediatrie headaches appear to respond well to biofeedback training.10 With appropriate medical and psychosocial screening (brain tumors and sexual abuse do not respond to biofeedback), children and adolescents with recurrent headaches will usually improve with 8 to 12 biofeedback sessions and daily home practice. Children and adolescents with tension headaches are more likely to have significant psychosocial comorbidity than those with pure migraine headaches. In either type of headache, however; mild psychosocial distress may not impede successful behavioral treatment of the headaches. On the other hand, moderate to severe psychosocial distress may indicate the need for mental health services prior to improvement in headache activity. Because pharmacologie prophylaxis of recurrent pediatrie headaches is not always effective and side effects may be significant, behavioral therapy may be the treatment of choice for recurrent pediatrie headaches.

Hypertension

Although no pediatrie biofeedback studies have been reported, many adult studies indicate that biofeedback treatment results in greater reductions in blood pressure than no-treatment control conditions, particularly for higher levels of blood pressure. Results with borderline and mildly hypertensive patients have been mixed." Additionally, most studies have shown a reduction in pharmacotherapy is possible with the addition of behavioral treatment for hypertension. The psychological treatment of hypertension has been studied using cognitive techniques (eg, learning to change responses to stress and anger) and behavioral techniques including biofeedback. A recent adult study compared cognitive therapy with heart rate biofeedback for essential hypertension.12 While both treatment groups had a significant decrease in blood pressure compared with controls, the heart rate biofeedback group achieved a greater decrease than the cognitive group. Although not using biofeedback, a recent behavioral treatment study of adolescent essential hypertension yielded initial positive results that were not maintained at 6-month follow-up.13 Although definitive pediatrie results are not currently available, it seems reasonable to use a biofeedback regimen for children and adolescents with hypertension in an effort to reduce pharmacotherapy or eliminate the need for it.

Raynaud's Disease/Phenomenon

This functional disorder of the peripheral vasculature is characterized by vasospastic attacks, presumably related to either central sympathetic hyperactivity or local digital vascular dysfunction. Many behavioral techniques have been applied to the treatment of idiopathic Raynaud's disease or the connective tissueassociated phenomenon. In adults, successful treatment has been accomplished with hypnosis, autogenie training, progressive muscular relaxation, and classical conditioning with immersion of the hands in warm water during whole body exposure to cold air.14 Skin temperature biofeedback provides a direct and dramatic measure of clinical response to behavioral treatment for Raynaud's phenomenon. There is some evidence that training under cold stress may enhance the efficacy of skin temperature biofeedback.15 Most children and adolescents find skin temperature biofeedback interesting and absorbing. Although untested, it is possible that temperature biofeedback might enhance motivation and compliance to a greater degree than other behavioral treatments.

Fecal Incontinence

Perhaps one of the best substantiated specific indications for biofeedback training in pediatrics is fecal incontinence. Numerous reports indicate excellent results with the application of manometric biofeedback in children with encopresis, repaired imperforate anus, and myelomeningocele.16,17 Training involves the use of rectal balloons that transmit intramural pressure to transducers for conversion into a biofeedback signal. Treatment usually begins with assessment of the rectosphincteric reflex of the internal anal sphincter, the strength of the external anal sphincter, and the threshold for subjective appreciation of rectal distention. The patient is then taught to voluntarily contract the external sphincter in response to rectal distention created by inflating a balloon. As training progresses, the patient is taught to increasingly discriminate smaller volumes of distention and accomplish the appropriate external rectal sphincter contraction. Eventually, the feedback signal is extinguished as the patient leams to rely solely on the subjective sensation of rectal distention. As in other disorders, the isolated use of biofeedback without a behavioral modification component of training is unlikely to be successful. In myelomeningocele, the relative contributions of biofeedback and behavior modification are debatable, but there may be a subgroup of patients with low spinal cord lesions and frequent bowel movements who benefit specifically from the addition of biofeedback training.18

Movement Disorders

EMG biofeedback may be helpful in managing some pediatrie movement disorders. There is evidence from the adult rehabilitation literature suggesting that EMG biofeedback may augment gains achieved by conventional physical therapy exercises in patients with residual disorders of cerebrovascular accidents and spasmodic torticollis that is refractory to treatment.19 In stroke patients, EMG biofeedback is used to facilitate the contraction of paretic muscles and inhibit spasticity. In children with cerebral palsy, visual feedback of muscle stretch reflex sensitivity has been used to reduce spasticity and joint-position auditory feedback has been used in gait training.20,21 Children and adolescents with tremor or involuntary movements that are increased with stress and anxiety may also benefit from biofeedback training.

Other Disorders

Biofeedback training has been applied to many clinical conditions;22'24 a few will be mentioned here. EEG biofeedback of "sensorimotor rhythm" has resulted in reduction in seizure activity in adults with intractable epilepsy, but the training appears to be labor-intensive and the effects are short-lived. Direct biofeedback of small airway function has not yet been accomplished and feedback of respiratory effort is cumbersome and no more effective than generalized relaxation training. Biofeedback training has been shown to alter heart rate and arrhythmias but extensive training is usually required. Skin temperature biofeedback has been applied successfully in some patients with reflex neurovascular dystrophy. Biofeedback from intraluminal transducers has shown some promise in adults with irritable bowel syndrome and several reports suggest that auditory feedback of bowel sounds may be used to condition gastrointestinal motility. Biofeedback has been used to enhance generalized relaxation in many conditions such as attention deficit disorder, anxiety disorders, and chronic pain syndromes.

FUTURE RESEARCH

Although perhaps not living up to its initial press as a panacea, biofeedback remains an intriguing area for future research. It is probable that with refined technology and greater specificity of physiological monitoring, more clinical indications for biofeedback therapy will develop. Current questions for clinical research might include: Is biofeedback training specific, or do clinical results reflect increased general organ homeostasis? How much biofeedback treatment is enough? Is follow-up practice really necessary? What strategies do patients really use? Does biofeedback enhance motivation and compliance with behavioral treatment programs? Are there any long-term beneficial effects of biofeedback training on cardiovascular, autonomie, and central nervous systems? With a continued scientific approach to application, it is likely that much of the biofeedback story remains to be written.

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10.3928/0090-4481-19910301-07

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