Appl Psychophysiol Biofeedback (2008) 33:49–54 DOI 10.1007/s10484-007-9048-4
The Influence of Respiration on Biofeedback Techniques Montserrat Conde Pastor Æ F. Javier Mene´ndez Æ M. Teresa Sanz Æ Enrique Vila Abad
Published online: 1 February 2008 Ó Springer Science+Business Media, LLC 2008
Abstract This research is based on previous studies which identified a specific respiratory pattern and inhalation-exhalation ratio, with which we were able to obtain significantly greater reductions in psychophysiological activation than with other respiratory patterns. The present study aimed to check the effectiveness of this respiratory pattern in learning based on biofeedback from the electrical conductance of the skin. The results obtained demonstrated that biofeedback combined with this respiratory pattern produced a significant reduction in psychophysiological activation and improved learning through biofeedback techniques. Keywords Skin conductance level (SCL) Respiration frequency Inhalation-exhalation ratio Psychophysiological activation Biofeedback
Introduction Biofeedback techniques are known to facilitate treatment for a wide variety of disorders with a psychosomatic component, including asthma, cardiovascular disorders, hypertension, cephalopathies, anxiety and duodenal ulcers,
M. Conde Pastor (&) F. Javier Mene´ndez M. T. Sanz Department of Basic Psychology II, Faculty of Psychology, Universidad Nacional de Educacio´n a Distancia (UNED), C/ Juan del Rosal, 10, 28040 Madrid, Spain e-mail:
[email protected] E. Vila Abad Department of Methodology, Faculty of Psychology, Universidad Nacional de Educacio´n a Distancia (UNED), Madrid, Spain e-mail:
[email protected]
and in many cases the results obtained have been notably positive (Conner et al. 2006; Damen et al. 2006; Goodwin 2006; Lehrer 2007). Nevertheless, it remains unclear how the patient who has undergone training with such biofeedback techniques learns how to control his or her autonomic responses (Gallegos and Yepez 1992). It has not yet been possible to offer such patients the appropriate instructions or guidelines needed to enhance learning and achieve greater control of their psychophysiological responses. In this regard, Shellenberger and Green (1987) highlighted the importance of the instructions given to patients with respect to the outcomes of learning with biofeedback techniques. According to these researchers, biofeedback is an instrument with which patients achieve the desired control over their physiological processes and which serves as a mirror to reflect back to the patient his or her own physiological responses and thus enable awareness of them. Biofeedback is therefore deemed to be an effective technique through which patients train themselves to acquire a set of skills, the learning of which is facilitated through the information given by the biofeedback apparatus. For this reason, the role of the instructions received by patients during their training in such techniques is fundamental to their learning of how to control their responses and thus achieve satisfactory results in the treatment of particular psychophysiological disorders. Generally, the instructions given to such patients have been aimed at achieving a general state of relaxation, in many cases by using progressive muscle relaxation. This involves getting patients to reduce their levels of psychophysiological activation in both situations of stress and at rest (Steve 2005). However, other studies have highlighted the importance of respiration in order to improve learning of biofeedback techniques (Labrador et al. 1996), since
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breathing techniques are a simpler and faster method than relaxation techniques. Outstanding is the biofeedback method proposed by Lehrer et al. (2003), in which the importance of a slow and deep breathing below basal values, an abdominal or thoracic breathing and specially the importance that concrete instructions have to obtain reductions in the activation of the subjects is highlighted. Although many respiration techniques have been used to obtain reduced psychophysiological activation, the ideal conditions for obtaining optimum results have yet to be empirically demonstrated. Indeed, although respiration techniques have been used extensively in the past, they have not been supported by experimental research to ascertain their validity. In previous studies carried out by our group we were able to determine a specific respiratory pattern that reduces skin conductance level (SCL) more readily than do other methods. In an initial study (Conde Pastor and Mene´ndez 2000a) we showed that the induction of respiration frequencies below the normal baseline frequencies of experimental subjects produced significant reductions in skin conductivity levels (SCL). In this study the sample comprised 48 university students and all subjects were applied the same breathing frequencies (6, 10, 14, 18 and 22 breaths per minute). Results showed that a significant number of subjects obtained lower levels of SCL at those frequencies which were below their baseline, as compared with induced frequencies that were the same as or above their baseline. In a second study (Conde Pastor and Mene´ndez 2000b), we aimed to establish which respiration frequency pattern below the baseline breathing frequency enabled experimental subjects to obtain the greatest reduction in SCL. A sample of 52 university students participated in this study. The results revealed an identifiable and effective respiratory pattern, which consisted of the induction of exactly three respiration frequencies below the baseline of experimental subjects. With this pattern, subjects obtained a greater reduction in their level of conductance than with any other pattern. In a third study (Conde Pastor and Mene´ndez 2002) we hypothesised that when we experimentally induced the same breathing frequency, we could expect that when the exhalation time was longer than the inhalation time, the levels of SCL would be lower than when the exhalation and inhalation times were the same. This argument is in consonance with the method proposed by Lehrer et al. (2000), in which they induced subjects to carry out exhalations of longer duration than inhalations. In this study we used a sample of 48 university students randomly distributed into three groups of 16 subjects each. Each group was induced a different inhalation-exhalation ratio (Group A: inhalation = X, exhalation = X; Group B: inhalation = Y,
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exhalation = Y + Y/2; Group C inhalation = Z, exhalation = 2Z). The results showed the presence of an effective, specific and generalizable inhalation-exhalation breathing ratio pattern for all subjects. The most significant differences were found between Groups A and C, with Group C presenting the lowest SCL values. This suggested that the induction of an exhalation time twice that of the inhalation time produced greater reductions in SCL than did the induction of other respiratory patterns. The present experiment, based on our previous studies, sought to determine the most appropriate respiratory pattern for reducing psychophysiological activation in test subjects. Here the control group were given precise guidelines (instructions), based on the respiratory parameters identified as optimum by the previous studies, with the aim of achieving enhanced learning through SCL-monitored biofeedback techniques, as compared with a control group that did not receive these particular guidelines.
Hypothesis Those individuals who, prior to biofeedback-based training, have been given precise respiration guidelines will achieve greater reductions in SCL in the biofeedback trials than those who have not been given such guidelines and only receive general instructions.
Methods Subjects In total, twenty undergraduates (11 males and 9 females) from the UNED University and aged 25–35 years old (29.45 ± 3.53) participated in the experiment. All subjects were chosen randomly. None of the participants reported having a history of psychiatric or neurological disorders. The overall procedure was explained to all subjects, who gave their consent for the procedure. All examinations were performed under the regulations of our Institutional Review Committee.
Equipment and Physiological Measurements A LETICA Polygraph-4006 multichannel polygraph was used. The temperature module (TMP 806) was used to measure and register the individual’s baseline respiratory rate by means of a thermistor placed in one nostril, and which enabled the respiratory cycles to be described. A conductivity module (SCL 316) was used to measure and register the SCL. Bipolar Ag/AgCl electrodes were used,
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each measuring 23 9 25 mm. BIOLOG (Lafayette Instrument Co.) was used as electrolytic paste. Two computer programs (SMAG 3 and TRV 92) were also used, having been specially designed for programming the times of each test and the rest times between tests during the biofeedback session, as well as to create the program containing the instructions that each group was to receive. A CIBERTEC CIBACK TC2 device was used for the biofeedback session. This was provided with two modules, one for control and the other to give information to the test individual.
Experimental Procedure Subjects were comfortably seated in an acoustically shielded, dimly lit room. The electrodes used for measuring SCL were attached between the first and second joint from the fingertips of the index and ring fingers of the individual’s non-dominant hand. The electrode used for measuring baseline respiration frequency (thermistor) was attached inside one of the individual’s nostrils. The sensitivity chosen for each measurement was graded according to the same criteria as used in previous experiments (0.1 l Siemens/mm for SCL and 0.05°C/mm for respiration). The baseline respiration frequency of each individual was measured for 10 min. The next stage was to randomly distribute the sample between two groups of 10 individuals each, according to two experimental conditions. The control group was given some precise guidelines, in addition to the general instructions, about the respiratory pattern that had proven most effective for the reduction of SCL. The test group was only given the general instructions. The twenty subjects were given the following general instructions to follow the experiment: ‘‘The aim of this test is that you reduce the electrical conductance of your skin. The more relaxed you manage to be the more this measure will decrease. To help you with this you will always have this piece of equipment in front of you (Subjects are shown the biofeedback information apparatus), and so you will always know whether your skin conductance is going down, up or staying the same. Notice that on this digital meter there are some numbers and below that a series of lights of which approximately half are lit up. (Pause). As your conductance decreases this number will get smaller and the line of lights will also get shorter. Watch what happens. (As a demonstration the experimenter claps his hands close to the subject’s face). What I’ve just done is activate you by giving you a fright that you weren’t expecting, and as you can see your conductance level has gone up. Notice how the line of lights has got longer and the number has got bigger. (Pause). You
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need to achieve just the opposite, that is, relax and try to make the number as small as possible or the line of lights shorter. You can look at both these things or, if you prefer, just concentrate on one of them. (Pause). In addition to the general instructions, all subjects of the control group also received the following guidelines: ‘‘In order to help you achieve this goal you will now be shown a type of breathing that will make it easier to reduce your SCL. (Here, we chose a respiratory frequency three cycles below the baseline frequency of each subject, and in all cases an expiration time twice as long as the inhalation time). Watch the monitor in front of you. (The monitor is right next to the biofeedback module and in front of the subject). You will see red screens followed by blue screens. Try to breathe, that is, breathe in while the screen is red and breathe out while the screen is blue. Try it for a few seconds. (Pause of around 45 s during which time the subject tries to breathe with the help of the screens being presented). The most important thing in this test is that you try to make this number smaller or the line of lights shorter (The experimenter points to the biofeedback module) in the way that is most comfortable and most effective for you. Practising this type of breathing may be useful to you. Please ask if you have any questions.’’ Once we were sure that the subject had understood perfectly the instructions given, we proceeded with the biofeedback session which consisted of visual information, both analogue and digital, in continuous and real time about his/her SCL. Ten trials, each of one-minute duration, were carried out, with rest times of one minute between trials (Fig. 1). The duration of the entire test was approximately 40 min.
Experiment Design A design of two independent samples was used (test and control).
Baseline respiration frequency (10 minutes)
Control Group (with guidelines)
Test Group 2 (without guidelines)
Baseline SCL (10 minutes) 1 session of biofeedback SCL (10 tests of 1 minute each) Rest between tests for one minute
Fig. 1 Experimental design
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The independent variable used was that of the instructions given to the test individuals, while the dependent variable was the SCL.
Data Analysis Data were analyzed using the SPSS (v. 14.0) package. One mixed, two-factor (2 9 10) ANOVA was performed with group (test, control), a between-subjects factor and trial (from 1 to 10 and a within-subjects factor. Before performing the mixed ANOVA we checked the assumption of sphericity by means of Machly’s sphericity test. The chisquare approximation for this test was 155.02 with 44 df and an associated probability of less than 0.001. Since this is less than the alpha level of 0.05, we can be confident that the data do not meet the sphericity assumption. As a result, we used the Greenhouse-Geisser epsilon (e) to adjust the degrees of freedom in the main analysis.
Appl Psychophysiol Biofeedback (2008) 33:49–54 Table 1 Statistical analysis of trial differences Source
Sum of square
df
Mean square
F
Significance level
Trial 1
0.158
1
0.158
0.118
0.735
Trial 2
1.321
1
1.321
0.678
0.421
Trial 3
7.614
1
7.614
3.182
0.091
Trial 4
28.872
1
28.872
10.458
0.005
Trial 5
25.380
1
25.380
7.980
0.011
Trial 6
24.598
1
24.598
11.197
0.004
Trial 7 Trial 8
34.008 47.957
1 1
34.008 47.957
9.903 10.297
0.006 0.005
Trial 9
38.005
1
38.005
8.666
0.009
Trial 10
32.794
1
32.794
6.911
0.017
Results Throughout the biofeedback session, SCL measurements were taken every two seconds, thus yielding a total of 300 absolute conductivity values, not including rest times, and representing 30 measurements per trial. By comparing these values with the baseline levels of each participant, we obtained, firstly, the average relative values of SCL in each one of the ten biofeedback sessions with both groups: test and control. The analysis showed that the Group main factor was significant (F[1,18] = 7.93, MSe = 2.476, P = 0.011, g2 = 0.306). Therefore, those individuals who, prior to biofeedback-based training, have been given precise respiration instructions show greater reductions in SCL than do those who have not been given such instructions. The Trial main factor was also significant (F[2,41] = 88.53, MSe = 2.734, P = 0.001, g2 = 0.831). The interaction Group x Trial was also significant (F[2,41] = 7.037, MCe = 2.734, P = 0.002, g2 = 0.281). Given the significance of the interaction between Group and Trial we analysed this interaction by computing simple effects analyses to ascertain the levels of the trial condition at which the two groups differed.
Trial Interaction As shown in Table 1, one-way ANOVAs showed differences between trials for both groups after the third trial. We believe that the respiration instructions do not appear to have any effect on the reduction of SCL, possibly because
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Fig. 2 SCL values for each group and trial
subjects may have been using different strategies at first. As shown in Fig. 2, there were significant differences from trial 4 to trial 10 between groups; there also seems to be a floor effect for the group of subjects that receive instructions after trial number 8.
Discussion Many years of clinical experience and research in the field have shown biofeedback to be a useful tool for achieving a variety of aims, whether therapeutic or not, and that in many cases its effectiveness depends on the therapist’s or researcher’s skill, or on their knowledge of how best to use such a tool. This is why the guidelines or instructions given to the test individuals prior to the beginning of training take on such importance.
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Accordingly, the importance of relaxed respiration, or more precisely, low-frequency respiration (between 8 and 10 c/m approximately), has already been emphasized by researchers such as Benson et al. (1974) or Janus et al. (1983) when they stated that some of the favourable effects observed with relaxation training were essentially the result of changes in respiration patterns. Similarly, other researchers argued that certain dysfunctional respiratory patterns, such as shallow or hurried breathing, or more precisely, high-frequency respiration, are often associated with a wide range of psychosomatic illnesses (Gibson 1978; Grossman 1983). Anxiety disorders and problems of stress, as well as any situation of heightened and sustained activation, may have negative repercussions on an individual’s health. For all of these reasons, respiration or biofeedback techniques may prove effective for the reduction of excess activation. At present, most relaxation techniques used base the state of an individual’s relaxation on his or her respiratory control; this most commonly focuses on time spent on exhalation. For instance, Eysenck (1989) observed that feelings of wellbeing and calm could be induced in test individuals when exhalation was prolonged and respiration techniques were implemented. The results show that individuals who received respiration instructions managed to reduce their SCL significantly more than those who did not. Thus, we deduce that the individual’s voluntary manipulation of certain respiratory parameters has a beneficial effect on his or her learning when SCL is reduced through biofeedback techniques. The identification of a respiratory pattern that can be generalized to all subjects, and with which greater reductions in activation can be achieved, may serve a dual purpose: on the one hand, to achieve states of relaxation in a simpler, quicker and more effective way than with other more costly techniques; and, secondly, to reduce activation levels in individuals in cases of high activation, as occurs, for example, in certain situations of stress and anxiety disorders, etc. Two possibilities therefore present themselves: either the identified respiratory pattern can be applied directly, using it merely as a relaxation technique, or, alternatively, the respiratory parameters that proved most effective at reducing SCL can be used in order to offer precise breathing instructions to individuals with regard to the identified respiratory pattern. This would enable enhanced learning to take place with biofeedback techniques, this being the main aim sought and tested in this study. Our results show a significant decrease of SCL in those subjects who were given precise respiration guidelines as compared to those subjects who only received general instructions. The importance of the present study is
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twofold: first, it demonstrates the importance of giving subjects precise and well-defined guidelines regarding their respiratory pattern and, secondly, it illustrates the importance of respiration when the aim is to decrease SCL in a biofeedback situation in order to lower the stress levels of subjects. Acknowledgement We acknowledge Dr. Emanuel Donchin for his helpful comments in the preparation of this manuscript, University of South Florida, Tampa, FL.
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