The effects of specific respiratory rates on heart rate and heart rate variability

In this study respiratory rates of 3, 4, 6, 8, 10, 12, and 14 breaths per minute were employed to investigate the effects of these rates on heart rate variability (HRV). Data were collected 16 times at each respiratory rate on 3 female volunteers, and 12 times on 2 female volunteers. Although mean heart rates did not differ among these respiratory rates, respiratory-induced trough heart rates at 4 and 6 breaths per minute were significantly lower than those at 14 breaths per minute. Slower respiratory rates usually produced higher amplitudes of HRV than did faster respiratory rates. However, the highest amplitudes were at 4 breaths per minute. HRV amplitude decreased at 3 breaths per minute. The results are interpreted as reflecting the possible effects of the slow rate of acetylcholine metabolism and the effect of negative resonance at 3 cycles per minute.     

Contingently faded heart rate biofeedback: Attempted replication of large-magnitude decreases

McKinney et al. (1980) reported large-magnitude reductions in heart rate (HR) from resting baseline levels, employing shaping and fading techniques and a reinforcement program in which a secondary reinforcer was awarded both contingently and immediately during training. The four male subjects in this group showed significantly greater HR decreases than a group of four males receiving beat-by-beat analogue HR feedback. The present study compared decreases in HR in 20 male subjects receiving the contingently faded biofeedback procedure to those shown by 10 male subjects for whom reinforcement was contingent on vigilant observation of a visual display, and independent of HR. The former group showed significantly greater decreases in HR that could not be attributed to elevated baseline levels. However, the decreases in HR were not as large as those reported by McKinney et al. (1980). It is argued that future research should assess variables contributing to individual differences in performance.This research was supported by Ontario Heart Foundation Research Grant 15–37 to R. Pavloski.     

The role of biofeedback in the operant modification of human heart rate

The recent literature on the role played by biofeedback in the modification of human heart rate is reviewed. Emphasis is placed on research pertinent to the issue of whether biofeedback is more productively conceived as a reinforcer of an operant response or as a source of information enabling the development of a voluntary motor skill. Criticisms of the operant paradigm are answered, and limitations of the motor skills analogy are discussed. It is concluded that the operant conditioning paradigm best accounts for most available data on the role of biofeedback in heart rate control, and that it is superior to the motor skills model because it is more parsimonious and makes fewer untestable assumptions.     

The production and generalization of large-magnitude heart rate deceleration by contingently faded biofeedback

Eight subjects were taught to decrease their heart rates via biofeedback training. Four of these received contingently faded, beat-by-beat analogue feedback and contingent reinforcement each time their performance met a specified and adjusting criterion. The other four received continuous, beat-by-beat analogue feedback, but not the contingent reinforcement. Subjects in the two groups were yoked to ensure equal densities of reinforcement. Subjects in the first group were asked to decrease heart rates 15% from baseline and were then trained using only 75%, 50% and 25% of beat-by-beat feedback. It was hypothesized that the immediate reinforcement of appropriate behavior and the contingent fading(following mastery) of feedback would aid in the generalization of the response. Following completion of all criterion steps or 10 training sessions, whichever came first, all subjects were tested with no feedback and no contingent reinforcement. The group receiving contingently faded feedback training showed a significantly greater heart rate decrease in the training sessions and also the test session. These results were interpreted as indicating that biofeedback can be conceptualized as an operant conditioning paradigm, and that the use of operant techniques may help subjects produce clinically significant changes.This research was supported in part by a grant to Robert J. Gatchel from the National Heart, Lung, and Blood Institute (Grant No. NIH HL 21426-01).     

Negative transfer of heart rate control following biofeedback training: a partial replication

Ability to raise and lower heart rate (HR) on instruction was tested before and after unidirectional biofeedback training in two groups of 10 male volunteers. Instructional control was assessed in 2-min trials before training, and after 5 and 10 biofeedback trials of increasing (Group I) and decreasing (Group D) HR. The magnitude of HR elevations produced by Group D diminished following training, while modifications in Group I were unchanged. This negative transfer effect is discussed in relation to whether voluntary speeding and slowing HR reflect distinct capacities.     

Effect of lung inflation on the respiratory frequency and heart rate of premature neonates

Changes in the respiratory frequency and heart rate in response to 10 seconds' inflation of the lungs with oxygen by the CPAP method were studied in 32 premature neonates. Elevation of the pressure in the airways and lungs of 0.25, 0.49, 0.73 and 0.98 kPa led to a slower respiration rate or to apnoea. The incidence of apnoea rose in proportion to the pressure. When inflation was started, forced inspiratory efforts (a gasp reflex) occurred. The incidence of the efforts was higher at higher inflation pressures, but their intensity was not correlated to the size of the pressure. They were manifested in a drop in oesophageal pressure to a mean -2.0 +/- 0.2 kPa and their mean duration was 169 +/- 8 ms. The administration of oxygen without an increase in pressure produced neither apnoea nor forced inspiratory reactions. Neither an increase in the pressure in the airways and lungs to the above values, nor the plain administration of oxygen, produced any significant changes in the instantaneous heart rate.     

Simultaneous biofeedback of heart rate and frontal EMG as a pretraining for the control of EEG theta activity

Following one base-line session, 20 normal subjects received four half hour sessions consisting of simultaneous feedback of heart rate and frontalis muscle (pretraining). Ten subjects received contingent (CF), the other ten noncontingent feedback (NCF). Subjects were asked to lower heart rate and frontal muscle tension (EMG). Heart rate within sessions decreased up to 19 bpm, with a mean of 4 bpm for the CF group. There was only a weak decrease over sessions, however, because of the strong habituation effect. The following events accompanied the heart rate decrease: (1) an increase of the variability of the heart rate, (2) a decrease of the variance of the EMG, (3) an increased correlation between heart rate slowing and EMG decrease, and (4) an increasing subjective experience of control of heart rate and EMG. After pretraining, subjects received eight sessions of auditory feedback of their frontal EEG theta activity (four sessions with CF and four sessions with NCF in balanced order). There was a weak increase of theta for the CF condition over sessions, but a decrease within the sessions. Pretraining on heart rate and frontal EMG control had no influence on the performance during theta training. It was hypothesized that control of heart rate slowing and theta control involve different mechanisms.     

Analysis of heart rate variability during exercise stress testing using respiratory information

This paper presents a novel method for the analysis of heart rate variability (HRV) during exercise stress testing enhanced with respiratory information. The instantaneous frequency and power of the low frequency (LF) and high frequency (HF) bands of the HRV are estimated by parametric decomposition of the instantaneous autocorrelation function (ACF) as a sum of damped sinusoids. The instantaneous ACF is first windowed and filtered to reduce the cross terms. The inclusion of respiratory information is proposed at different stages of the analysis, namely, the design of the filter applied to the instantaneous ACF, the parametric decomposition, and the definition of a dynamic HF band. The performance of the method is evaluated on simulated data as well as on a stress testing database. The simulation results show that the inclusion of respiratory information reduces the estimation error of the amplitude of the HF component from 3.5% to 2.4% in mean and related SD from 3.0% to 1.7% when a tuned time smoothing window is used at an SNR of 15 dB. Results from the stress testing database show that information on respiratory frequency produces HF power estimates which closely resemble those from the simulations which exhibited lower SD. The mean SD of these estimates with respect to their mean trends is reduced by 84% (from 0.74×10⁻³ s⁻² to 0.12×10⁻³ s⁻²). The analysis of HRV in the stress testing database reveals a significant decrease in the power of both the LF and HF components around peak stress.     

Instructed heart rate control in the presence and absence of a distracting task: The effects of biofeedback training

Twenty volunteers participated in a single-session experiment in which bidirectional heart rate (HR) control was assessed before and after brief unidirectional HR biofeedback. Subjects attempted to raise (INC) and lower (DEC) HR while performing mental arithmetic, as well as in no-task conditions. Biofeedback training was also carried out in the presence and absence of mental arithmetic. Subjects were divided into two groups on the basis of initial HR reactivity to mental arithmetic. Group U received feedback and instructions to raise HR during the training period, while group D attempted to lower HR. Significant differences in HR modifications during INC and DEC trials were observed prior to any biofeedback training in no-task conditions. Following training, however, ability to raise HR deteriorated in group D, while HR decelerations were impaired in group U. Unidirectional training in HR control thus handicapped subsequent attempts to modify HR in the reverse direction. The pattern of HR change was generally paralleled by respiration rate. Subjects were also able to influence the cardiac reactions to mental arithmetic even before the administration of biofeedback. The data nevertheless suggest that training affects the magnitude of HR reactions after the biofeedback is withdrawn. In the biofeedback phase itself, the HR increases and decreases produced by groups U and D, respectively, were diminished on simultaneous mental arithmetic performance.The authors are grateful to Drs. Beryl Starr and Alvin Ross for their advice at various stages of this project.     

Microgravity alters respiratory sinus arrhythmia and short-term heart rate variability in humans

We studied heart rate (HR), heart rate variability (HRV), and respiratory sinus arrhythmia (RSA) in four male subjects before, during, and after 16 days of spaceflight. The electrocardiogram and respiration were recorded during two periods of 4 min controlled breathing at 7.5 and 15 breaths/min in standing and supine postures on the ground and in microgravity. Low (LF)- and high (HF)-frequency components of the short-term HRV (< or =3 min) were computed through Fourier spectral analysis of the R-R intervals. Early in microgravity, HR was decreased compared with both standing and supine positions and had returned to the supine value by the end of the flight. In microgravity, overall variability, the LF-to-HF ratio, and RSA amplitude and phase were similar to preflight supine values. Immediately postflight, HR increased by approximately 15% and remained elevated 15 days after landing. LF/HF was increased, suggesting an increased sympathetic control of HR standing. The overall variability and RSA amplitude in supine decreased postflight, suggesting that vagal tone decreased, which coupled with the decrease in RSA phase shift suggests that this was the result of an adaptation of autonomic control of HR to microgravity. In addition, these alterations persisted for at least 15 days after return to normal gravity (1G).     

A device for functional residual capacity controlled biofeedback of respiratory resistance

A computer-aided procedure is presented providing subjects with analogous visual feedback of respiratory resistance, which is continuously measured using the forced oscillation method. Simultaneous pneumotachographical control of the breathing volume curve makes it possible to prevent reinforcement for decreases of respiratory resistance which are due to increases of functional residual capacity (FRC). Lung hyperinflation is an unsuitable way to reduce respiratory resistance; if it occurs, feedback is interrupted until the subject decreases his FRC to its initial level. Analysis of the data of 15 adult asthmatic subjects which underwent a 12-sessions feedback training showed that no substantial changes of FRC appeared within feedback trials. Advantages of this new biofeedback technique compared to other procedures are discussed with regard to volume control and feedback signal.     

Thyroid effect on brain activity in adolescents during heart rhythm biofeedback session

Types of neurophysiologic and thyroid condition in 15-17-year old adolescents were studied for the purpose of heart rhythm biofeedback session effect by heart rhythm variability parameters. Changes of heart rhythm vegetative regulation activity modulate functional capacities of central vegetative regulation structures. The biofeedback training with heart rhythm variability parameters increases brain bioelectrical activity in different frequency ranges. The thyroid system modulates functional activity of vegetative regulation central structures uppermost at sympathotonic and thyreotropin increasing leads to increase of rhythm maker structure reactivity in brain.     

Heart rate biofeedback and cold pressor pain: effects of expectancy

The study investigated the effects of expectancy on the reduction of cold pressor test pain using heart rate biofeedback training. Thirty-six male subjects were given an initial 45-sec cold pressor test, 25 heart rate decrease feedback training trials, and a final cold pressor test in which they were told to decrease their heart rate, but without the aid of feedback. Two levels of outcome expectancy (increase pain, decrease pain) and two levels of cold pressor water temperature (0 degrees C, 5 degrees C), resulting in four groups (N = 9 per group), were used to assess the interaction between expectancy and aversive stimulus intensity. Immediately prior to the final cold pressor test, the increase pain expectancy subjects were told that decreasing their heart rate during the ice water immersion would cause more pain. Decrease pain subjects were told that decreasing their heart rate would cause less pain. Expectancy was found to be the major determinant of pain reports. The decrease pain subjects consistently reported less pain on the final cold pressor, whereas the increase pain subjects consistently reported more pain. Contrary to prediction, expectancy effects were greater for the colder water. The findings indicate the importance of expectancy in the clinical use of biofeedback to control pain.     

Heart rate biofeedback and cold pressor pain: Effects of expectancy

The study investigated the effects of expectancy on the reduction of cold pressor test pain using heart rate biofeedback training. Thirty-six male subjects were given an initial 45-sec cold pressor test, 25 heart rate decrease feedback training trials, and a final cold pressor test in which they were told to decrease their heart rate, but without the aid of feedback. Two levels of outcome expectancy (increase pain, decrease pain) and two levels of cold pressor water temperature (0°C, 5°C), resulting in four groups (N=9 per group), were used to assess the interaction between expectancy and aversive stimulus intensity. Immediately prior to the final cold pressor test, the increase pain expectancy subjects were told that decreasing their heart rate during the ice water immersion would cause more pain. Decrease pain subjects were told that decreasing their heart rate would cause less pain. Expectancy was found to be the major determinant of pain reports. The decrease pain subjects consistently reported less pain on the final cold pressor, whereas the increase pain subjects consistently reported more pain. Contrary to prediction, expectancy effects were greater for the colder water. The findings indicate the importance of expectancy in the clinical use of biofeedback to control pain.This research was supported by National Institute of Mental Health Research Grant MH-26923. Computing assistance was provided by the Office of Academic Computing, UCLA. We would like to thank Lisa Greenstadt, John Richards, John Reeves, and Barbara Smith for their assistance.