Methodologic implications for rehabilitation research: Differences in heart rate variability introduced by respiration

PM R, 2022 · DOI: 10.1002/pmrj.12770 · Published: December 1, 2022

Spinal Cord Injury Neurology Rehabilitation

Simple Explanation

Heart rate variability (HRV) is a measure of autonomic activity used in research. However, the influence of respiration on HRV is often overlooked, leading to potential misinterpretations in rehabilitation medicine research. The study examines how unpaced and paced breathing affect HRV measures in individuals with spinal cord injury (SCI). It highlights the importance of considering respiratory patterns when analyzing HRV data. The findings suggest that respiration significantly impacts HRV following SCI, and failure to account for this can lead to inaccurate data interpretation. Future studies should consider paced breathing to standardize respiratory patterns.

Study Duration

Not specified

Participants

59 individuals with spinal cord injury

Evidence Level

Cross sectional comparison

Key Findings

1
Mean low frequency (LF) power was significantly higher during unpaced breathing compared to paced breathing.
2
The percentage of total power derived from the LF spectrum and the mean LF:HF ratio were both significantly higher for unpaced breathing.
3
Bland-Altman plots revealed a significant positive proportional bias for LF power when comparing unpaced and paced breathing, indicating increasing inaccuracy as LF power increases.

Research Summary

This study investigates the impact of respiration on heart rate variability (HRV) measurements in individuals with spinal cord injury (SCI), comparing unpaced and paced breathing conditions. The results demonstrate that unpaced breathing significantly skews LF power, the percentage of total power in the LF range, the LF:HF ratio, and SDNN, leading to a proportional bias in LF measurements. The authors conclude that respiratory frequency has a significant impact on HRV and recommend that future studies in rehabilitation medicine consider paced breathing to minimize uncontrolled error.

Practical Implications

Standardize Breathing Protocols

Future rehabilitation medicine studies using HRV should incorporate paced breathing to minimize the confounding effects of respiration.

Improve Data Interpretation

Researchers and clinicians should be aware of the potential for respiratory patterns to skew HRV results, particularly in populations with altered respiratory mechanics.

Re-evaluate Existing Literature

Previous studies that did not account for respiratory patterns may need to be re-evaluated, as their conclusions regarding autonomic control may be affected by respiratory confounds.

Study Limitations

1
The study did not allow accurate tidal volume estimates.
2
The order of unpaced vs paced breathing was fixed throughout these experiments.
3
Respiration is an established driver of heart rate variability in short-term recordings.

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