Cardiac Biofeedback training and Subjective Well-Being improvement Treinamento de Biofeedback Cardíaco e Melhoria do Bem-Estar Subjetivo

Psychosomatic Stress Management, based on computational psychophysiological biofeedback techniques, is a modern method of training and conscious stress control. The Heart Rate Variability biofeedback (HRV) is one of the most reliable strategy for measuring parameters related to the functioning of the autonomic nervous system. The study aim was to apply HRV technique to the evaluation and training university students, correlating cardiac coherence to changes in the perception of Subjective well-being (SWB). Eighty two students from the State University of Goiás, Goiânia, Goiás, Brazil, were evaluated. The cardiac biofeedback evaluation and training were performed using the CardioEmotion software (Neuropsicotronics, University of São Paulo, SP). For the accomplishment of this study, the students’ HRVs were measured, in consecutive training sessions, and the pre and post scores training were compared. Significant improvement in SWB was demonstrated after biofeedback training. The technique also helped participants to learn how to reestablish and maintain cardiac coherence. We concluded that HRV training helped to reduce the stress levels and anxiety reported by the study participants.


INTRODUCTION
Heart rate variability (HRV) biofeedback is one of the most reliable methods for measuring parameters related to the autonomic nervous system functioning. HRV is defined as the time variation measured between two R's waves. On the electrocardiogram, the heartbeat shows a peak generated by atrial depolarization, P wave, a ventricular depolarization complex, QRS complex, and finally the ventricular depolarization, T wave. The instantaneous heart rate can be established as the interval between two consecutive R's peaks, which is known by RR interval. HRV is, therefore, the variation found in the time intervals between RR peaks in a series of measurements performed in the time domain.(PAUL; GARG, 2012) There are three cardiac biofeedback action axes in the cardiac coherence state: the baroreflex axis -responsible for the blood pressure regulation -, a second axis, known as vagal afference -where information is sent via the vagus nerve to the upper centers (limbic system -emotions) and the prefrontal cortex. A third mechanism is associated with the anti-inflammatory axis, responsible for reducing inflammation.(PAUL; GARG,

2012)
HRV biofeedback reports the emotional expression index based on the interaction between the sympathetic and parasympathetic systems. A low HRV is associated with vagus nerve less activity and sympathetic nervous system increased activity. (DANUCALOV, 2010) In the cardiac coherence state, the autonomic nervous system rebalances. This rebalancing results in increased oxygen saturation and better brain and prefrontal cortex oxygenation; hypertension reduction; reduced tension, through muscle relaxation, and reduced chronic pain; reduced heart rate; excess cortisol reduction, by acting on the HPA axis (hypothalamus-pituitary-adrenal), resulting in dehydroepiandrosterone levels increase (DHEA). (DANUCALOV, 2010) The autonomic nervous system balance is also reflected in the limbic system, promoting a amygdala hyper-reactivity reduction in the hippocampus. As a result, there are stress, anxiety and depression decrease; there are also insomnia, hyperactivity, and lack of attention reduction. (MCEWEN;WINGFIELD, 2003;TROISI, 2001)

Subjective well-being (SWB)
SWB is the studies field that seeks to understand the assessments that people make of their lives.(DIENER; SUH; OISHI, 1997) These must be cognitive (overall satisfaction with life and other specific domains) and must also include a personal frequency analysis which positive and negative emotions are experienced. According to OISHI, 1997), in this field of knowledge, we do not seek to study negative or pathological psychological states, such as depression, anxiety and stress, but to differentiate the levels of well-being that people can achieve in their lives.
The SWB concept appeared in the late 1950s, when quality of life indicators were sought to monitor social changes and the implementation of social policies. Campbell In SWB, it is necessary to consider that each person evaluates his own life by applying subjective conceptions. In this process, they rely on their own expectations, values, emotions and previous experiences. These subjective conceptions, according to Diener, Oishi and Lucas (DIENER;LUCAS, 2003), are organized in thoughts and feelings about individual existence.
It is understood by several scholars (DIENER et al., 1999;OISHI, 1997) that SWB is a broad phenomenon and should be considered as a scientific interest area that encompasses two specific concepts: global satisfaction with life judgments, or with specific domains of it, and positive and negative emotional experiences. (DIENER et al., 1999) In this sense, the SWB concept articulates two perspectives in psychology: one is based on theories about emotional states, emotions, affects and feelings (positive affects and negative affects) and the other one is sustained in the cognition domains, being operationalized by satisfaction evaluations (in general life, in specific life aspects such as work).
Considering the above description, the study aim was to assess whether cardiac biofeedback improves the university students SWB perception.

Ethical aspects
This study was approved by the Ethics and Research Committee of the State University of Goiás under the number of 2,512,498.

Participants
Eighty two students from the State University of Goiás, Goiânia, Goiás, Brazil, were evaluated. Students who presented any health problem that prevented the biofeedback assessment procedure, such as heart disease; or students who practiced relaxation, meditation and breathing techniques were excluded from the study.

HRV assessment
Cardiac biofeedback assessment and training was performed using the CardioEmotion software (Neuropsicotronics, University of São Paulo, SP). Cardiovascular biofeedback is a physiological self-modulation technique mediated by resonance between two cardiovascular regulation mechanisms: the baroreceptor reflex and respiratory sinus arrhythmia. This measure represents the interval between two consecutive heartbeat pulsations (RR interval). By non-invasive sensors placed on the fingers or the auricular lobe, the beats were captured and then transmitted to a computer program to assess the heart rate. Before starting training in biofeedback, the resonant breathing frequency was established, in which it is possible to obtain more time in cardiac coherence. The time intervals recording between each heartbeat was followed by the mathematical treatment of these data by software. The software attributed a note (range 0 to 10, being 0 total incoherence and 10, perfect coherence). Participants underwent daily biofeedback sessions, lasting 20 minutes, for 8 weeks.

SWB evaluation
A self-administered questionnaire composed by SWB Scale was used for data collection. This scale was developed by Albuquerque and Tróccoli (ALBUQUERQUE;TRÓCCOLI, 2004), and consists in 62 items, of which 21 represent positive affect components, 26 negative affect and 15 life satisfaction.

Self-Esteem assessment
The Self-Esteem Scale developed by Rosenberg (ROSENBERG, 1989) was used. This is a one-dimensional measure consisting in ten statements related to a feelings set of self-esteem and self-acceptance that assesses global self-esteem. Items are answered on a four-point Likert scale ranging from strongly agree, agree, disagree and strongly disagree.
In this study, the version adapted to Portuguese by Hutz (HUTZ, 2000) was used.

Hope Assessment
The instrument used was Herth's Hope Scale, adapted to Portuguese by Grossi (2008). The scale consists in 12 statements with responses on a Likert-type scale with scores from 1 to 4 for each of them, and the higher the score, the greater the hope.

Optimism assessment
For the optimism assessment, the Life Orientation Test Revised -LOT-R adapted and validated by Bastianello, Pacico, & Hutz (BASTIANELLO;PACICO;HUTZ, 2014) was used. This instrument consists in 10 items that assess optimism and pessimism.

Data analysis
The collected data were analyzed using the Statistical Package for the Social Sciences -SPSS, version 17 for Windows. The ANOVA test and the paired t test were used to compare biofeedback and SWB variables and pre and post training scores. The correlation between SWB and HRV factors was assessed using Pearson and Spearman's correlation coefficient.

Participant characteristics
Eighty two volunteers were invited to participate in the present study. However, 50% of participants resigned from participating in the survey between the first and fifth sessions. The main reason for dropping out was the cell phone compulsion. These students claimed shortage of time, difficulty concentrating during training and the inability to refrain of using a cell phone.
Participants who completed the training were between 17 and 45 years old (mean age = 27). Eighty percent were female and 46.7% were married.

HRV coherence
The average score for physiological monitoring observed before training was 4.2.
After the biofeedback sessions, there was an increase in coherence, being 7.8 the average grade. When comparing the pre and post-training physiological monitoring average scores, significant results (p <0.00001) were observed after training.

SWB assessment
The SWB increase was observed after the study ending. There was an perception improvement in all SWB scales. A significant increase in the component "life satisfaction" (p <0.0001) and positive affects (p <0.0001), in addition to self-esteem (p <0.0001) and Optimism (p <0.002) was observed (table 1). After the interventions ending, the volunteers reported having achieved greater emotional control in verbal confrontation situations, as well as a significant improvement in self-esteem and a considerable growth between positive and negative affects. Eleven participants stated a reduction in the general stress level. One volunteer reported less binge eating. It is worth mentioning that 7 people reported an improvement in sleep quality as well.

HRV and SWB correlation
When assessing the correlation between HRV and SWB, the optimism, hope and self-esteem scales, we observed a significant correlation between HRV and the life satisfaction components, positive affect, optimism and self-esteem scales (table 2).

CONCLUSION
The present study demonstrated that cardiac biofeedback, associated with conscious respiratory control, contributed to SWB, optimism and life satisfaction increase and stress reducing levels.