Respiratory sinus arrhythmia (RSA) characterises the variation in heart rate that occurs during each breathing cycle. RSA is known to have important regulatory functions and can be modulated using biofeedback procedures. It has been proposed that this helps stabilise autonomic tonus, which in turn might improve different disorders characterized by autonomic dysfunction. The aim of this study was to explore the effect of RSA biofeedback on cortical pain processing in healthy subjects. 

‘Control’ (N=6) and ‘RSA’ (N=6) groups received acute painful stimuli (Nd:YAP laser) on the hand at the nociceptive threshold. Pain reports were recorded with cortical potentials (32 electrodes, 2 series of 15 stimuli) before and after two full weeks of RSA training (5 min, 3 times a day, six breaths per minute) for the ‘RSA’ group and of a control respiratory task for the ‘control’ group. Latencies and amplitudes of laser evoked potentials (LEPs) were studied. 
The amplitudes of LEPs are significantly smaller after the two weeks training in the ‘RSA’ group, relative to those obtained before training. No significant effect was observed on the amplitudes of the LEPs in the ‘control’ group. Latencies of the LEPs were not changed before and after the training in the two groups.
RSA biodfeedback is a non-invasive, cost-effective and self-administered technique which appears to modulate acute cortical pain processing. Our results are encouraging enough to warrant further the studies in healthy subjects (eg assessing descending pain modulation) as well as in patients with pain linked to autonomic dysfunction and stress.

MODULATING CORTICAL RESPONSE TO PAIN BY RESPIRATORY SINUS ARRHYTHMIA BIOFEEDBACK