Heart Variability Biofeedback as Supplementary Care for Brain Cancer: A Feasibility Study

Abstract

Heart rate variability biofeedback (HRVB) is a breathing-based technique that can reduce symptoms of distress in noncancer populations.¹ However, only two identified, small n studies have used HRVB in an oncology setting,^2,3 and neither used elevated distress as an inclusion criterion. The authors' study was therefore designed to test the feasibility and the efficacy of HRVB in a sample of distressed primary brain tumor (PBT) patients (World Health Organization grade II–IV). PBT patients exhibit high levels of distress⁴ and often experience diverse symptoms, making a side-effect free intervention particularly valuable.

The authors sought to recruit 15 distressed PBT survivors. Assessments were conducted during the first, fifth, and eighth meetings. During the assessments participants completed self-report measures and a 10-min HRVB task. The intervention involved eight weekly meetings. The HRVB protocol was adapted from Lehrer et al.⁵ and offered participants' audio/visual feedback for both respiration rate (via abdominal strain gauges) and heart rate (via infrared blood volume pulse sensor attached to a finger). The goal of training was to teach participants to breathe in a relaxed, diaphragmatic manner at their specific “resonant frequency.” This is an idiosyncratic pace (typically between 4 and 7 breaths/min) that produces a strong spike in HRV power, centered in the Low Frequency (LF) range (0.05–0.15 Hz). Daily homework involved 20 min of paced breathing. The specific breathing rates for home practice were based on each participant's unique resonant frequency.⁵ A Procomp 2 device (Thought Technology) was used for all HRV acquisition and training. The Psychosocial Screen for Cancer⁶ was used as a screening tool. The Beck Depression Inventory II and the Beck Anxiety Inventory served as outcome measures.

Data Analysis

For HRV data analysis, an experienced biofeedback clinician removed relevant artifacts. Normalized units of LF power (NLF) from the biofeedback task were then calculated using the formula LF power/Very LF power+LF power+High Frequency power. This calculation was used to assess for skill acquisition⁷ because successful application of the biofeedback technique causes a higher percentage of the total HRV power to arise within the LF range. Analysis of the self-report data involved computing descriptive statistics and effects sizes (Mean 2 − Mean 1/pooled standard deviation).

Results

Patients (n = 163) were invited to participate. Forty-six expressed interest, 26 were screened, and 9 were recruited. Five participants completed all of the training sessions/assessments. One completed all the training sessions, but not the final HRV assessment. The other three were noncompleters.

Only 48% of the home practice tracking sheets were returned. However, the returned sheets revealed completion of 93% of the homework. Five HRV completers' posttraining NLF mean on the biofeedback task was larger than their equivalent pretraining mean. The effect size of this difference was d = 0.58. There was a decrease in Beck Depression Inventory-II (BDI-II) and Beck Anxiety Inventory (BAI) scores with effect sizes of d = 0.75 and d = 0.87, respectively (Table 1).

Table 1.

Self-report Outcomes for Training Completers (N = 6)

Measure	Time 1, mean (SD)	Time 2, mean (SD)	Time 3, mean (SD)	Time 1–3, ES
BDI-II	17.8 (2.5)	15.7 (4.5)	12.0 (3.6)	d = 0.75
BAI	16.2 (3.6)	8.0 (1.9)	9.3 (2.8)	d = 0.87

BAI, Beck Anxiety Inventory; BDI-II, Beck Depression Inventory-II; ES, effect size; SD, standard deviation.

Discussion

The primary purpose of this study was to test the feasibility of HRVB with distressed PBT survivors. This study targeted (n = 15), recruited (n = 9), and completed (n = 5). Alternate recruitment approaches will be needed to feasibly carry out a full-size randomized clinical trial. The dropout rate was 33%, only slightly above the 26% dropout rate found for cognitive behavioral therapy across diverse clinical trials.⁸ The results therefore appear supportive of retention-related feasibility. Patients also seemed to adhere closely to the assigned home practice. However, conclusions around practice compliance must remain tentative because of the low rate of returned homework tracking sheets. In terms of skill acquisition, the NLF analysis revealed a large to moderate effect size for pre–posttraining, consistent with similar studies and with the ability of study completers to develop the necessary skills. The BAI (d = 0.87) and BDI-II (d = 0.75) also showed improvements consistent with clinically meaningful reductions in symptoms of anxiety and depression. Although encouraging, these findings must be viewed with strong caution, given the very small n and lack of a control group.

In sum, this feasibility study encourages the execution of a full clinical trial of HRVB because it represents a potentially effective, side-effect free intervention for distressed PBT patients.

Footnotes

Acknowledgments

This study was funded by the BC Cancer Agency Hershey and Yvette Porte Neuro-oncology Endowment Fund. Thanks to Linda Walker (LPC, BCIA-EEG) for artifact detection and analyzing the HRV data.

Author Disclosure Statement

This study was granted approval from the BC Cancer Agency REB with no competing financial interests.

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