Method and Apparatus for Breathing in Synchrony with the Heart1. Introduction 1.1 BreathingIt is known that the breathing process is largely automatic. The rhythm of breathing is influenced by physical, emotional and mental activity. The breathing pattern can be easily modified by external (environmental), internal (homeostatic) and volitional influences.
One of the features of the early phase of training in many arts (e.g. singing, playing music instruments, etc.) and sports (e.g. running, swimming, etc.) is training the subject to modify the respiratory pattern at will in order to achieve peak performance results in said arts or sports. Furthermore, techniques for the re-training of the breathing process have been widely used throughout the ages by both traditional and modern medical systems, in order to improve health in various ways. Breathing has been used as a therapy (alone or combined with other strategies) in the treatment of conditions such as clinical anxiety, hyperventilation, sleep apnoea, borderline hypertension, panic attacks, migraine, phobias, asthma, irritable bowel syndrome, gastritis, diabetes, insomnia (Fried R., 1990).
The general physiology of breathing control has been studied extensively, however, the best patterns to be used in breathing re-training schedules and the actual ways to present the data to the trainees remain a subject of intensive discussion (Ronald Ley, 1995).
Two aspects of breathing have been specially dealt with: the breathing mode and the breathing rhythm. Briefly, thoracic/chest, fast and shallow breathing has been associated with high psychophysiological arousal while diaphragmatic/abdominal, slow and deep breathing is known to induce relaxation and reduction in psychophysiological arousal.
Recently a new patent has been filed (Defares, P.B. et al, 1994) which describes an interactive respiratory regulator to record the user's respiratory pattern and to generate an instruction signal to help him/her to influence his/her respiratory pattern according to a pre-determined schedule.
1.2 Respiratory Sinus ArrhythmiaThe heart rate is rhythmically related to the respiratory cycle. It tends to increase during inspiration and decrease during expiration. This phenomenon is known as respiratory sinus arrhythmia ("RSA") and is based on the autonomic modulation of the heart pacemaker. The greater the vagal (vagus nerve) efferent activity, the greater will be its decelerating effect on the heart rate and hence the amplitude of the oscillations of the heart rate in the breathing period.
According to research from the last ten years, RSA has been established as a good marker of parasympathetic (vagal) tone in humans (Berntson et al 1993). RSA amplitude values have even been proposed as a general stress marker (Porges, 1995)) and as a sedation score (Wang et al, 1993).
1.3 Parasympathetic (Vagal) Tone TrainingThe functions of the autonomic nervous system are considered (by definition) to be automatic and involuntary. However, it has been shown that by means of biofeedback techniques, individuals can be made aware of, and eventually trained to achieve control over, the activities of the autonomic nervous system. For example, it has been shown that heart rate biofeedback can be successfully used to teach people to slow down the heart rate at will (Pegalajar et al, 1984).
1.4 Vagus Activity and Breathing disordersIn a recent patent filing, another method was disclosed for the control of the parasympathetic effect over respiratory disorders (Wernicke J. ,1993). According to this application, and depending on the needs of the patient, the Vagus nerve is either stimulated or inhibited by direct electrical means.
2. Purpose, Principles and UsesIt is the purpose of this application to describe a method and apparatus to direct people non-invasively through a breathing re-training programme. The breathing schedule is guided by their own cardiac activity with its oscillations due to the parasympathetic tone (reflected in the degree of RSA present at that moment). The technique is not based on biofeedback principles but rather on resetting the cycle of one natural biological clock (the breathing cycle ) by the beneficial effects of vagal activity shown by another (cardiac pacemaker). This is fully consistent with the need for "synchronicity" among various ultradian rhythms (rhythms with a period shorter than one day) required for the harmonic functioning of the whole body.
This method/device may be used in four main areas:Breathing retraining programmes in cases of breathing disorders related topsychophysiological dysfunction.
Cardiac disease prevention and rehabilitation programmesGeneral stress, clinical anxiety and phobia management programmes.
. Non drug treatment for Obstetric and Gynaecology conditions such as Hot flashes,Pre-menstrual tension and De-arousal during pregnancy.
3. Preferred Embodiment 3.1 Electrocardiogram (ECG) DetectionA preferred embodiment of the invention is now described.
According to the present invention, a chest wall ECG is measured using surface electrodes in the lead II configuration. The signal is amplified and filtered; and the heart beat (i.e. the peak R-wave in the QRS complex) is detected by an adaptive peak detector circuit module. The interbeat duration (i.e. the R-R interval series) between consecutive beats is on-line measured and a special moving average function is applied to these values by a processing module in order to achieve a good degree of data "smoothing".
The result of the a.m. processing procedure is a series of values which mainly oscillates in the frequencies between 0.1 and 0.3 Hz (natural breathing frequencies) when RSA takes place. All faster components are substantially filtered out by the moving average function.
Finally, the data is used to trigger the breathing pattern sound indicator: the multiprocessed R-R interval data series is transformed into an on-line audio output by feeding it to a suitable sound chip. The result is a sound wave which is used to indicates to the user the time, the duration and the amplitude of the breathing cycle to follow.
By breathing in synchronisation with the heart a "resonance-like" phenomenon takes place which prolongs the RSA rich periods and actually amplifies the amplitude of theRSA oscillation. This automatically ensures higher degrees of cardiac parasympathetic activity and hence facilitates de-arousal and healthy breathing habits by purely natural means.
3.2 Breathing Pattern IndicatorThis module comprises two types of display:Two separate LEDs, (of different colour) to mark the inspiration and the expirationcycles;A cyclic naturalistic sound (for instance the sound of the sea wave coming in andgoing out of the coast) generated by an audio chip. The amplitude and timing ofthe wave is dependent on the R-R processed series and will be used to indicate therhythm and depth of breathing.
3.3 Breathing Training ScheduleDuring a preliminary short period of calibration, the user is instructed to breath naturally while trying to make the breathing pattern as slow and as deep as possible without discomfort. It is advisable that a short lesson on healthy breathing (deep, slow and diaphragmatic) be provided to the subject by a doctor or health practitioner prior to the use of the device.
During the calibration period, the device monitors the establishment of a respiratory sinus arrhythmia (RSA) pattern in the R-R series by calculating the presence of a predominant sinus in the normal breathing frequency. This is done by a microprocessor calculating a COSINOR like algorithm. When the amplitude at the natural RSA frequency range is discriminated above noise, the Breathing TrainingSchedule mechanism is discharged.
The device then starts to direct the breathing pattern according to the R-R series using both the inspiration-expiration LEDs display and the natural sound wave.
Finally, the data (R-R wave series) is stored for subsequent data analysis using anEEPROM facility communicating with the main microprocessor. A download connector facility will then facilitate to further process the data (spectrum analysis etc.) in a PC.
4. ReferencesDefares, P.B., De C. A. Willigen, E.T. Verveen (1994). An interactive respiratoryregulator. WO 9414374 Al 940707Ley, R. (1995). Highlights of the 13* International Symposium on RespiratoryPsychophysiology held at the inaugural meeting of the International Society for theAdvancement of Respiratory Psychophysiology. Biofeedback and Self-Regulation(20), 4, 369-279.
Pegalajar, J. and J. Vila (1984) Autocontrol de la tasa cardiaca: El modelo deBrener. Revista de Analisis del Comportamiento 2, 271-283Porges, S.W. (1995). Cardial Vagal Tone: a physiological index of stress.
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Wang D.Y., C.J.D. Pornfrefl and T.E.J. Healy (1993). Resporatory SinusArrhythmia: a new objective sedation score. British Journal ofAnaesthesia 71,354-358.
Wernicke, J.F. and R.S. Terry (1993). Treatment of respiratory disorders by nervestimulation. WO 9301862 Al 930204