Svært interessant studie som gjennomgår hele 20 studier som viser hvordan HRV forholder seg til smerte, lav HRV = høy smerte og motsatt. Den nevner blandt annet at SNS reagerer i løpet av sekunder, mens PNS reagerer i løpet av millisekunder. Så når vi ser på variasjoner i hjerterytme (HRV), eller kurven på StressEraser eller StressDoctor App, er det PNS sin funksjon vi ser.

http://robjellis.net/papers/Koenig_et_al_2013_EJP.pdf

Non-pathologic acute pain is a complex sensory and emotional experience (Fernandez and Turk, 1992) that signals the organism to somatic damage, leading to an appropriate motor response of protection (Loeser and Melzack, 1999). Because pain is a stressor and environmental challenge (which in turn requires that organism to respond), it has been dis- cussed as a specific emotion that reflects homeostatic behavioural drive, similar to temperature, itch, hunger and thirst (Craig, 2003).

A comprehensive framework to investigate the way in which organisms function and adapt to diverse types of stressor such as pain is the model of neurovis- ceral integration (Thayer and Lane, 2000, 2007), which posits flexibility in the face of changing physiological and environmental demands as a hallmark of success- ful adaptation. The authors proposed that a core set of neural structures provides an organism with the ability to continuously assess the environment for signs of threat and safety and to prepare the organism for appropriate action. Heart rate variability (HRV) has been proposed to serve as index of the degree to which this system provides flexible, adaptive regulation (Thayer et al., 2012).

Like many organs in the body, the heart is dually innervated. Although a wide range of physiologic factors determine cardiac functions such as HR, the ANS is the most prominent (Thayer et al., 2012). Chronotropic (i.e., the timing of heartbeats) control of the heart is achieved via the complex interplay of the sympathetic nervous system (SNS) and parasympa- thetic nervous system (PNS) branches of the ANS. More importantly, the HR is under tonic inhibitory control by the PNS influences (Jose and Collison, 1970).

Relative increases in SNS activity are associated with HR increases and relative increases in PNS activity are associated with HR decreases. While SNS effects are slow on the timescale of seconds, PNS effects are faster on the timescale of milliseconds (Levy, 1997). There- fore, the PNS influences are the only ones capable of producing rapid changes in the beat-to-beat timing of the heart (Uijtdehaage and Thayer, 2000).

Findings from these studies may have important clinical implications as a large variety of health condi- tions are associated with changes in ANS function that can be indexed by HRV (Rajendra Acharya et al., 2006).

Addressing the field of pain, reduced HRV is reported in patients with complex regional pain syn- drome (Terkelsen et al., 2012), fibromyalgia patients (Mork et al., 2013), patients with chronic neck pain (Kang et al., 2012), irritable bowel syndrome (Mazurak et al., 2012) or headache (Micieli et al., 1993; Tubani et al., 2003). Furthermore, lower HRV is associated with extended pain-related sick leave in employees (Kristiansen et al., 2011).

Thus, HRV is of interest as a potential biomarker for specific pain- related diseases (Lerma et al., 2011) and a potential outcome measure for the relief of pain due to thera- peutic interventions (Storella et al., 1999; Zhang et al., 2006; Toro-Velasco et al., 2009). Evidence on the rela- tion of HRV and experimentally induced pain in healthy subjects may help gain further insights on changes in autonomic function in patients with pathological pain states.