I would like to report my experience in the use of a visual biofeedback technique in COPD pulmonary rehabilitation. As will be described, the technique permits breathing pattern alteration, even in the elderly, that is surprisingly easy to achieve. These learned breathing patterns are retained to a variable degree. A copy of the training program is being made available for downloading from the Internet.
I am a pulmonary physician, and have no formal training in biofeedback. The breathing training device and program was begun with the presumption that it should be possible to mechanically define a breathing pattern that was optimal for every disease state or functional respiratory condition.
Of necessity this assumption challenges what seems to be a general feeling in the pulmonary community, that breathing is autoregulated to an optimal state. It is certainly true there are numerous chemical, neural, proprioceptive and other reflexes that autoregulate breathing. Further is the prominent 1978 paper by Sorli(1) and colleagues which noted COPD patients with hypercapnia breathed at lower tidal volumes with a resulting decrease in alveolar ventilation. Essentially these patients obtained dyspnea relief by trading reducing mechanical work for a rise in their PCO2 levels. This is a reasonable explanation for breathing pattern regulation of end stage COPD with ventilatory failure, but it does not adequately explain the large majority of decompensating patients who are not retaining CO2. The explanation perhaps lies in what I have called the "Rescue Breathing Pattern."
The Rescue Breathing Pattern involves the cognitive aspect of breathing control, and is the conscious response of the patient to dyspnea stress. Simply described, this breathing pattern is to "pump air in and out of the lungs." I submit that virtually every layman and even young children, with prompting, will be able to describe this reflex action. In greater detail, this is a rapid rate, a focus on inspiration, a larger tidal volume (within rate limitations), a shorter expiratory phase, and forced inspiration and expiration. I submit that simple observation confirms this to be the typical dyspnea distress breathing pattern of the young and elderly, healthy but deconditioned individuals and world class athletes, and every cardiac and pulmonary disease condition that I am aware of. Perhaps the Rescue Breathing Pattern is so common that it is simply not being recognized?
As will be seen in this article, in patients with COPD there are both acute and chronic responses to the Rescue Breathing Pattern. Acute patient response results in well defined physiologic consequences of functional Air Trapping and dynamic overinflation, resulting in further acute distress. A chronic patient response seems probable to the author, but this is not well defined and certainly controversial. COPD chronic breathing pattern alteration would be the basis for an important aspect of the loosely defined and controversial term "Breathing Exercises," and as such would also be physiologically sound, at least in the context of correcting functional overinflation.
First consider the Rescue Breathing Pattern in Restrictive Lung Disease, e.g. Pulmonary Fibrosis. Typically this pattern is rapid and shallow, and terminally one sees essentially panting respiration. This breathing pattern is an example of good autoregulation and adaptation, as it is in conformity with mechanically efficient breathing, and likewise conforms to the Rescue Breathing Pattern. When the reduced lung volume reservoir is stretched to its elastic limit, further attempts at increasing the tidal volume result in a marked increase in inspiratory effort and the work of breathing. Thus, rapid shallow breathing results, and this pattern is not enhanced by conscious breathing alterations in the chronically dyspneic patient. Note also that rapid shallow breathing is the typical defensive breathing pattern of fatiguing respiratory muscles, and chronic respiratory fatigue is commonly seen in many restrictive disorders.
Now consider the Rescue Breathing Pattern in Obstructive Lung Disease such as COPD / Emphysema and Asthma. But first we must digress to the problem of functional "Air Trapping" and pulmonary overinflation. This occurs because with expiration the caliber of the bronchi normally diminishes, and expiration is therefore always more mechanically difficult due to this selective increase in airway resistance on expiration. This phenomenon is exaggerated in Emphysema with the loss of supporting alveolar structure to help maintain bronchial diameter. Hence an increased time constant to expiratory flow and the need for a slower respiratory rate and a prolonged expiratory phase in order to permit full exhalation of alveolar gas. And furthermore, the need for gentle expiration, as forced breathing will only aggravate the problem of dynamic bronchial compression with further narrowing of the airways.
Here the seminal papers in the 1950's by Dr. William Miller(2, 3) are instructive. And note in Dr. Miller's reference list some papers dating to the 1930's. With only simple spirometric tools Dr. Miller conclusively demonstrated the detrimental overinflation effects of functional Air Trapping with uncontrolled hyperpnea (and also important, similar adverse effects with uncontrolled coughing). Numerous papers since have refined Dr. Miller's observations, and it is now undisputed that functional overinflation places the respiratory bellows apparatus in a position of mechanical disadvantage, with a resultant increase in the work of breathing and therefore increased dyspnea distress. The problems of overinflation and the complex interaction with the chest wall and respiratory muscles was summarized in an editorial by Macklem(4) in 1984.
Consider now the psychological reaction of the emphysema victim who suffers an episode of increasing dyspnea, for example, after mild exertion or a coughing episode. Fear and sometimes panic is typical, and with loss of control, frequently there is activation of the Rescue Breathing Pattern. The resultant breathing pattern is a physiologic disaster, as this pattern is 180 degrees out of phase with physiologic requirements. Within only a few breaths progressive Air Trapping develops and the dyspnea state acutely intensifies. And further distress leads to a vicious cycle of further unproductive breathing efforts which only magnifies the problem.
In order to recover from an acute dyspnea attack the COPD patient must:
1. Be calm, and regain control (the dyspnea exacerbation is substantially a cognitive trigger).
2. Relax (tense respiratory muscles are at a functional disadvantage)
3. Breathe slowly (not fast; the long time constant of alveolar emptying requires this).
4. Concentrate on breathing OUT (not the natural instinct to breathe in; Air Trapping must first be resolved, i.e. "You must first get rid of the stale air to make room for the fresh air").
5. Breathe OUT a long way (not the natural instinct to relieve dyspnea by breathing in; the expiratory phase must be excessively prolonged, to promote alveolar deflation).
6. Breathe gently (not the natural instinct to force breathing; this will exacerbate the dynamic bronchial compression / critical airway closure problem).
7. Breathe in only 75-80% (not the desired full inspiration breath; this will only prolong the problem of overinflation).
The need for breathing pattern alteration in this acute recovery process should be obvious, and likewise the need for cognitive effort. If the patient does this breathing pattern correctly, typically they feel dyspnea relief usually within ten breaths. They can then switch into a more satisfying breathing pattern with less emphasis on prolonged expiration and deflation. The skilled patient learns to control dyspnea in this manner, before it gets out of control. This encourages progressive activity. Loss of control, with subsequent fear and depression is certainly one of the dominant features of COPD. Regaining control from dyspnea distress can have a profoundly positive benefit to the patient's general well being.
Teaching breathing patterns in a traditional manner (hands on; listen to breath sounds, etc.) is tedious, labor intensive, and highly imprecise and empirical. The breathing training device to be described was born of frustration with traditional rehabilitation methods and designed to enhance this process. It was created as a scientific tool, with capability of clinical use. Inherent design features necessitated the capability to precisely define breathing patterns, teach these breathing patterns effectively, quality control patient performance, and document learning progress and retention of learned breathing patterns. With this in mind the following visual biofeedback training system was created, initially in the Commodore 2000 PET computer, and later in the IBM XT computer system. It was first publicly shown to the California Thoracic Society on October 7, 1978.
By menu selection the operator selects Tidal Volume, Respiratory Rate, Inspiration : Expiration Ratio, end Inspiratory Hold time, end Expiratory Hold time, and inspiration and expiration waveforms (linear, slightly curvilinear, more curvilinear). The computer then generates a "Breathing Prescription" volume (y axis) versus time (x axis) display. A blinking cursor moves along this programmed analog in the correct time domain to prompt the patient as to desired performance. Given the fundamental equation Volume = Flow X Time, knowing the volume and time, the device then becomes an instantaneous flow controller. As the patient breathes through the mouthpiece (Hans Rudolph or Fleisch pneumotachs; Validyne or Celesco differential pressure transducers) the flow signal is input into the computer with an Analog to Digital Converter and software integrated to a Tidal Volume display, which is displayed in real time from left to right. At the end of each inspiration / expiration cycle the screen refreshes back to zero on the left side of the display.
A simple computer generated "Breathing Prescription" volume versus time display is noted in Figure 1.
A more complex breathing analog is shown in Figure 2. A blinking cursor moves along the
programmed analog in the correct time domain to prompt the patient as to desired performance. Note the patient performance line below the programmed line, thus giving a visual biofeedback prompt to correct performance.
To quality control performance, adjustable plus and minus error limit lines may be displayed, and an auditory alarm signals when the patient has exceeded parameter limits. The program may be paused, and hard copy obtained for documentation purposes. Further details and graphic displays of this system, and a patient example, may be seen at http://www.sierrabiotech.com in the section on Biofeedback Incentive System (tm) (BIS (tm)).
What I believe is unique and powerful in this biofeedback display was discovered by serendipity. It was desired to use the full computer screen for display purposes, and therefore the display was adjusted to automatic full scale the Tidal Volume and Time parameters. The effect is, that large and small breaths, and slow and rapid breaths, all appear to be identical (with only the moving cursor indicating the respiratory rate). This I have called the "Primary Breathing Pattern" as indeed all breathing patterns must contain the fundamental aspects of volume and time. All of the other adjustments (I:E Ratio, inspiration and expiration Hold times, and various waveforms) are then characterized as "Secondary Breathing Patterns" superimposed on the Primary Breathing Pattern. Most breathing patterns, even with the addition of a variety of Secondary Breathing Pattern adjustments appear superficially quite similar. However, despite appearing rather simplistic, the information content of visual analogs is high.
Now, consider the general nature of the biofeedback learning experience. This external patient signal to elicit the biofeedback awareness response always appears identical, or nearly identical. Thus, the learned patient response comes from within the patient's own unique sensed physiologic sensations. To recall and use the breathing prescription the patient needs only to recall the simple visual analog signal. In addition, if the derived breathing prescription is correct, the patient should sense breathing comfort, and therefore the technique would be classified as a more powerful Positive Reinforcement Biofeedback technique.
Carefully consider Figure 1. That simple breathing pattern could represent both a Tidal Volume of 500 cc with a Rate of 15 bpm, as well as a Tidal Volume of 2000 cc with a Rate of 5 bpm. Despite the identical appearance of the breathing pattern, obviously the breathing pattern is very different. The use of that breathing pattern must dominantly come from within the individual learned breathing biofeedback experience and the breathing sensations generated. This biofeedback training method appears therefore to accentuate the biofeedback learning process, and presumably is the reason why the technique appears to be so effective in breathing pattern alteration.
In my practice the operator and computer system were separated from the patient display and input mouthpiece device by about three meters, thus providing a less distracting area for the patient, spouse, and/or therapist to interact. Presence of the spouse is encouraged, as they usually relate to the breathing display and the patient interaction, and often become excellent observers and coaches in the home environment to encourage better patient performance.
All training sessions began with the patient's screen blanked, and a native, unprompted breathing pattern was obtained, to document the initial and follow-up breathing patterns to evaluate progress. Then, the patient screen is activated, and the patient practices intermittently for approximately five to ten minutes, but never more than fifteen minutes as the sessions are tiring ( and sometimes mild hyperventilation symptoms appear, as the working Tidal Volume is generally 30 to 50 percent above their usual, to encourage progressively larger volume excursion capability). As part of the instruction session the patient is taught to visually exhale past their usual end expiratory volume, in order to teach them lung deflation techniques. This is in conjunction with physical therapy techniques of chest mobilization and diaphragm awareness that will not be elaborated upon. At the end of the session the patient is given a copy of their native breathing pattern, and their practice breathing prescription, with annotations as to deficiencies and desired performance.
Most patients, even those in their 80's and computer phobic, are able to begin to follow the breathing prescription within about five minutes, and by the end of the second session have a reasonable degree of skill in following the prescription.
The home program consists of twice a day (but no more) sessions, lasting no more than five minutes. Longer sessions are tiresome, discourage concentration, and are otherwise unproductive. The patient is instructed to sit in a comfortable chair, relax, and to concentrate on the performance of their breathing exercises. They are instructed to visualize their printed breathing pattern and to "put it into your mind."
Most patients show early breathing pattern modification by the end of the first month, and most are significantly following their breathing pattern by the second or third month. During this time I have usually reviewed the patient three times, for routine clinical matters (as most patients initially are referred following an episode of decompensation, requiring closer follow-up), plus the additional training session. The overall medical and technician component to this training regime is therefore minimal, the large burden of training shifted to the patient and spouse in the home environment. The efficiency and cost effectiveness of this method therefore becomes apparent.
Retention of the learned breathing pattern is less certain and variable. Most patients have a slow decline in their performance, which is easily corrected and reinforced by two, occasionally three prompting sessions a year. On the other hand I have seen occasional patients at yearly intervals, and rarely after two years, with no decline in performance. Clearly, breathing patterns can be taught, and appear to be retained, even in the elderly.
A related and fascinating anecdote needs telling. Several years ago a patient's spouse told me that her husband was breathing "like that," i.e. the prescribed breathing pattern, while asleep. Subsequently I have routinely asked spouses about nocturnal breathing patterns, and approximately half of them report positively after about three or four months into the rehabilitation program.
Does this indicate that patients are incorporating learned breathing patterns chronically into their physiologic control mechanisms? Does it indicate that patients are able to overcome chronic activation of their Rescue Breathing Pattern, and thereby maintain relative comfort? The answer to this crucial question is probably yes, but still not entirely certain. Confirmation of breathing pattern alteration on re-testing in the office environment is easily documented but still with uncertainties as this may be a testing and training artifact that is not representative of the true native breathing pattern. Long term respiratory monitoring studies, before and after breathing re-training are needed to answer this question. I would submit that if nocternal breathing pattern alteration is confirmed by direct measurement, this would resolve the question as to whether or not learned breathing patterns are retained.
What is the correct breathing pattern for the individual patient? I would be the first to admit that I do not know the precise answer to this important question. As noted above, the teachings of Dr. William Miller and many others provide only general guidelines. The answer must lie in a study of breathing patterns in the COPD patient using advanced pulmonary mechanics techniques, and most likely to demonstrate breathing patterns which are most efficient (i.e. with the lowest work of breathing) while maintaining a necessary level of alveolar ventilation. To the best of my knowledge this has never been done.
In the interim I have been guided by my discovery of an unusual (I would estimate approximately 1 in 40 of the patients referred to me for pulmonary rehabilitation) and most interesting subset of patients. These patients had few complaints of dyspnea, despite having severe pulmonary function defects (e.g. RV/TLC 65% or more; FEV1 0.5 LPS or less). The breathing pattern of these patients was generally as noted from the teachings of Dr. Miller, and of probable significance, inspection of their tracings indicated a smooth, well coordinated pattern, in contrast to the usual more irregular pattern of breathing. Of interest these patients typically were well coordinated (previous athletic excellence, etc.), trained singers, and musicians (e.g. woodwind instruments). I believe this small subset of patients is a model of natural adaptation, who have intuitively learned to overcome a chronic Rescue Breathing Pattern and are maintaining relative breathing comfort despite severe pulmonary mechanical adversity. If this is correct, I submit it would be of interest to identify and thoroughly study this subset of patients to discover why they have done so well.
Essentially in the programming of the visual biofeedback device I have been guided by the breathing patterns of this subset of patients as I have previously reported (5, 6). The suggested parameters for an average sized adult are Tidal Volume 700 to 900 cc, Respiratory Rate 11-12 bpm, I:E Ratio 1:1.7 to 1.9, end inspiration breath Hold 5%, end expiration breath Hold 10%, inspiration and expiration waveforms more curvilinear. If possible, expiration should be entirely passive, but many patients require end expiration effort, which should be controlled and gentle.
With chest mobilization and improved respiratory muscle strength the Tidal Volume is increased. The occasional patient requires an I:E Ratio as much as 1:2.2. As to possible long term benefits of chronic breathing pattern alteration, the subject is controversial. So-called "Breathing Exercises," a general and poorly defined term in the authors opinion, have been criticized as unworthy, and particularly so in the European pulmonary community. As breathing pattern alteration would fall under the general term of Breathing Exercises, I believe this criticism is not entirely correct.
My observations suggest that COPD patients in more advanced stages of their disease breathe chronically in response to the Rescue Breathing Pattern, and, that they can be taught to breathe in a manner that chronically corrects the problem of functional overinflation. Much more speculative is my suspicion that chest wall mobilization techniques, dating to the 1930's but presently mostly ignored, may shift the Pressure / Volume curve to a slightly less restrictive pattern.
Of interest, a similar respiratory visual biofeedback system has been developed by Esteve (7) and Blanc-Grass (8) and colleagues. These authors select the target breathing pattern from a series of breaths, the so-called "respiratory personality" which they define as "the deepest and longest breath." This author, with his roots in clinical medicine and pulmonary mechanics, and believing in the reality of the chronic Rescue Breathing Pattern, questions the validity of selecting the target breathing pattern in this manner.
A limited but fully functional copy of this visual biofeedback program has been developed in the National Instruments LabVIEW programming environment. It is available for downloading and unrestricted private use at http://www.sierrabiotech.com
It is my hope that clinicians and biofeedback practitioners will use this program better than I have, that pulmonary mechanics researchers define optimal breathing patterns and the underlying mechanisms, and that behavioral scientists tell me why this program appears to work so well.
REFERENCES:
1.) Control of breathing in patients with chronic obstructive lung disease. J. Sorli, A. Grassino, G. Lorange, and J. Milic-Emile; Clinical Science and Molecular Medicine (1978), 54, 295-304.
2.) A Physiologic Evaluation of the Effects of Diaphragmatic Breathing Training in Patients with Chronic Pulmonary Emphysema. William F. Miller; American Journal of Medicine (1954), 17, 471-477.
3.) Physical Therapy Measures in the Treatment of Chronic Bronchopulmonary Disorders: Methods for Breathing Training. William F. Miller; American Journal of Medicine, (1958), 24, 929-940.
4.) Editorial: Overinflation. Macklem, Peter T.; American Review of Respiratory Disease, (1984), 129, 3-7
5.) A visual biofeedback method to define and teach breathing patterns. D. Hillsman; Biological Psychology (1996), 43, No.3, 261.
6.) Clinical experience with a visual biofeedback method in COPD rehabilitation. D. Hillsman; Biological Psychology (1996), 43, No.3, 243-244.
7.) A New Device for Pulmonary Rehabilitation Based on Visual Biofeedback: Principle and Methods. F. Esteve, N. Blanc-Gras, P. Baconnier, G. Benchetrit; Innovation and Technology in Biology and Medicine, (1994), 15, No.1, 10-19.
8. A New Device for Pulmonary Rehabilitation Based on Visual Biofeedback: -2- Computer
Program. N. Blanc-Gras, F. Esteve, P. Baconnier, G. Benchetrit; Innovation and Technology in
Biology and Medicine, (1994), 15, No.1, 20-32.