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{{Short description|Activity of the vagus nerve}}
'''Vagal tone''' refers to activity of the [[vagus nerve]], a fundamental component of the [[Parasympathetic nervous system|parasympathetic]] branch of the [[autonomic nervous system]]. This branch of the nervous system is not under conscious control and is largely responsible for the regulation of several body compartments at rest. Vagal activity results in various effects, including: [[heart rate]] reduction, [[Vasodilation|vasodilation/constriction]] of [[Blood vessel|vessels]], glandular activity in the [[heart]], [[lung]]s, and [[Gastrointestinal tract|digestive tract]] as well as control of gastrointestinal sensitivity, motility and inflammation.<ref name=":1" />


In this context, tone specifically refers to the continual nature of baseline parasympathetic action that the vagus nerve exerts. While baseline vagal input is constant, the degree of stimulation it exerts is regulated by a balance of inputs from [[Sympathetic nervous system|sympathetic]] and [[Parasympathetic nervous system|parasympathetic]] divisions of the autonomic nervous system. Despite the described duality, vagal tone has been reported to mainly reflects the general level of parasympathetic activity. Vagal tone is typically considered in the context of heart function, but also has utility in assessing emotional regulation and other processes that alter, or are altered by changes and modification of the parasympathetic activity.<ref>{{Cite journal|last=Diamond|first=Lisa M.|last2=Fagundes|first2=Christopher P.|last3=Butterworth|first3=Molly R. | name-list-format = vanc | date=2011|title=Attachment Style, Vagal Tone, and Empathy During Mother-Adolescent Interactions |journal=Journal of Research on Adolescence |volume=22|issue=1|pages=165–184|doi=10.1111/j.1532-7795.2011.00762.x }}</ref><ref>{{cite journal | vauthors = Grossman P, Wilhelm FH, Spoerle M | title = Respiratory sinus arrhythmia, cardiac vagal control, and daily activity | journal = American Journal of Physiology. Heart and Circulatory Physiology | volume = 287 | issue = 2 | pages = H728-34 | date = August 2004 | pmid = 14751862 | doi = 10.1152/ajpheart.00825.2003 }}</ref>
tone of the vagus nerve the of [[ nervous system|]] [[ nervous system]] of the nervous system . Vagal in heart , of | | , , of .<ref>{{cite journal | vauthors = , , | title = Respiratory sinus arrhythmia, , and | journal = | volume = | issue = 2 | pages = | date = | pmid = | doi = 10./.. }}</ref>


Measuring vagal tone along with its quantification and estimation can be performed by means of either invasive or noninvasive procedures. The former methodologies encompass the vagus nerve stimulation by manual or electrical techniques but literature reports a very limited number of experiments and clinical studies especially involving human subjects. On the other hand, noninvasive techniques are largely employed and they mainly rely on the investigation of [[heart rate]] and [[heart rate variability]].<ref name="Vagus Nerve Stimulation">{{cite journal | vauthors = Howland RH | title = Vagus Nerve Stimulation | journal = Current Behavioral Neuroscience Reports | volume = 1 | issue = 2 | pages = 64–73 | date = June 2014 | pmid = 24834378 | pmc = 4017164 | doi = 10.1007/s40473-014-0010-5 }}</ref><ref name=":0">{{cite journal | vauthors = Porges SW, Doussard-Roosevelt JA, Maiti AK | title = Vagal tone and the physiological regulation of emotion | journal = Monographs of the Society for Research in Child Development | volume = 59 | issue = 2-3 | pages = 167–86 | date = 2008 | pmid = 7984159 | doi = 10.1111/j.1540-5834.1994.tb01283.x }}</ref><ref>{{cite journal | vauthors = Brock C, Jessen N, Brock B, Jakobsen PE, Hansen TK, Rantanen JM, Riahi S, Dimitrova YK, Dons-Jensen A, Aziz Q, Drewes AM, Farmer AD | title = Cardiac vagal tone, a non-invasive measure of parasympathetic tone, is a clinically relevant tool in Type 1 diabetes mellitus | journal = Diabetic Medicine | volume = 34 | issue = 10 | pages = 1428–1434 | date = October 2017 | pmid = 28703868 | doi = 10.1111/dme.13421 }}</ref>
tone the stimulation and the , heart and journal|=|= |=|= |=|= | -- = | =|title= Vagal and |journal= of Research |volume=|issue=|pages=|doi=10.1111/j.-...x }}</ref><ref>{{cite journal | vauthors = , , , , | = of | volume = | issue = | pages = | date = | pmid = | doi = 10./. }}</ref>

Measurements of vagal tone can be performed by means of either invasive or noninvasive procedures. Invasive procedures are in the minority and include vagus nerve stimulation by specific manual, breathing or electrical techniques. Noninvasive techniques mainly rely on the investigation of [[heart rate]] and [[heart rate variability]].<ref name="Vagus Nerve Stimulation">{{cite journal | vauthors = Howland RH | title = Vagus Nerve Stimulation | journal = Current Behavioral Neuroscience Reports | volume = 1 | issue = 2 | pages = 64–73 | date = June 2014 | pmid = 24834378 | pmc = 4017164 | doi = 10.1007/s40473-014-0010-5 }}</ref><ref name=":0">{{cite journal | vauthors = Porges SW, Doussard-Roosevelt JA, Maiti AK | title = Vagal tone and the physiological regulation of emotion | journal = Monographs of the Society for Research in Child Development | volume = 59 | issue = 2–3 | pages = 167–86 | date = 2008 | pmid = 7984159 | doi = 10.1111/j.1540-5834.1994.tb01283.x }}</ref><ref>{{cite journal | vauthors = Brock C, Jessen N, Brock B, Jakobsen PE, Hansen TK, Rantanen JM, Riahi S, Dimitrova YK, Dons-Jensen A, Aziz Q, Drewes AM, Farmer AD | title = Cardiac vagal tone, a non-invasive measure of parasympathetic tone, is a clinically relevant tool in Type 1 diabetes mellitus | journal = Diabetic Medicine | volume = 34 | issue = 10 | pages = 1428–1434 | date = October 2017 | pmid = 28703868 | doi = 10.1111/dme.13421 | s2cid = 25030686 }}</ref>


== Noninvasive vagal tone quantification ==
== Noninvasive vagal tone quantification ==
In the majority of cases, vagal tone is not directly measured. The most common procedure towards its quantification consist in investigating the processes altered by the [[vagus nerve]] - specifically heart rate and heart rate variability. As a general consideration, increased vagal tone (and thus vagal action) is associated with a diminished and more variable heart rate. On the opposite, during [[Tilt table test|graded orthostatic tilt]], vagal tone withdrawal is physiological and described as an indirect indicator of cardiovascular fitness.<ref name=":4">{{cite journal | vauthors = Montano N, Ruscone TG, Porta A, Lombardi F, Pagani M, Malliani A | title = Power spectrum analysis of heart rate variability to assess the changes in sympathovagal balance during graded orthostatic tilt | journal = Circulation | volume = 90 | issue = 4 | pages = 1826–31 | date = October 1994 | pmid = 7923668 | doi = 10.1161/01.CIR.90.4.1826 }}</ref>
In cases, vagal tone is not directly. the processes by the [[vagus nerve]] specifically heart rate and heart rate variability a vagal tone (and thus vagal action) is associated with a heart rate , during [[Tilt table test|graded orthostatic tilt]], vagal tone withdrawal is an indirect indicator of cardiovascular fitness.<ref name=":4">{{cite journal | vauthors = Montano N, Ruscone TG, Porta A, Lombardi F, Pagani M, Malliani A | title = Power spectrum analysis of heart rate variability to assess the changes in sympathovagal balance during graded orthostatic tilt | journal = Circulation | volume = 90 | issue = 4 | pages = 1826–31 | date = October 1994 | pmid = 7923668 | doi = 10.1161/01.CIR.90.4.1826 }}</ref>


=== Vagal innervation of the heart ===
=== Vagal innervation of the heart ===
[[Heart rate]] is largely controlled by the heart's internal pacemaker activity. Considering a healthy heart, the main pacemaker is a collection of cells on the border of the [[Atrium (heart)|atria]] and [[Venae cavae|vena cava]] called the [[sinoatrial node]]. Heart cells exhibit automaticity which is the ability to generate [[Electrical conduction system of the heart|electrical activity]] independent of external stimulation. As a result, the cells of the node spontaneously generate electrical activity that is subsequently conducted throughout the heart, resulting in a regular heart rate.<ref name=":1" />
[[Heart rate]] is largely controlled by the heart's internal pacemaker activity. a healthy heart, the main pacemaker is a collection of cells on the border of the [[Atrium (heart)|atria]] and [[Venae cavae|vena cava]] called the [[sinoatrial node]]. Heart cells exhibit automaticity the ability to generate [[Electrical conduction system of the heart|electrical activity]] independent of external stimulation. the node the heart.<ref name=":1" />


In absence of any external stimuli, sinoatrial pacing contributes to maintain the heart rate in the range of 60-100 beats per minute (bpm).<ref>{{cite journal | vauthors = Nunan D, Sandercock GR, Brodie DA | title = A quantitative systematic review of normal values for short-term heart rate variability in healthy adults | journal = Pacing and Clinical Electrophysiology | volume = 33 | issue = 11 | pages = 1407–17 | date = November 2010 | pmid = 20663071 | doi = 10.1111/j.1540-8159.2010.02841.x }}</ref> At the same time, the two branches of the autonomic nervous system act in a complementary way increasing or slowing the heart rate. In this context, the vagus nerve acts on sinoatrial node slowing its conduction thus actively modulating vagal tone accordingly. This modulation is mediated by the [[neurotransmitter]] [[acetylcholine]] and downstream changes to [[Ion channel|ionic currents]] and calcium of heart cells.<ref name="Vagus Nerve Stimulation"/>
In absence of external stimuli, sinoatrial pacing the heart rate in the range of beats per minute (bpm).<ref>{{cite journal | vauthors = Nunan D, Sandercock GR, Brodie DA | title = A quantitative systematic review of normal values for short-term heart rate variability in healthy adults | journal = Pacing and Clinical Electrophysiology | volume = 33 | issue = 11 | pages = 1407–17 | date = November 2010 | pmid = 20663071 | doi = 10.1111/j.1540-8159.2010.02841.x }}</ref> two branches of the autonomic nervous system or the heart rate. vagus nerve acts on sinoatrial node slowing its conduction modulating vagal tone the [[neurotransmitter]] [[acetylcholine]] and downstream changes to [[Ion channel|ionic currents]] and calcium of heart cells.<ref name="Vagus Nerve Stimulation"/>

Given the evidence that the vagus nerve plays a crucial role in heart rate regulation by modulating the response of [[sinoatrial node]], vagal tone can be quantified by investigating heart rate modulation induced by vagal tone changes. This kind of analysis allows to investigate vagal tone by means of several noninvasive techniques based on [[heart rate variability]].<ref name=":0" />


===Respiratory sinus arrhythmia===
===Respiratory sinus arrhythmia===
'''Respiratory sinus arrhythmia''' (RSA) is typically a benign, naturally occurring variation in heart rate that occurs during each breathing cycle. Specifically, heart rate increases during inspiration and decreases during expiration period.<ref name=":1">{{cite journal | vauthors = Berntson GG, Cacioppo JT, Quigley KS | title = Respiratory sinus arrhythmia: autonomic origins, physiological mechanisms, and psychophysiological implications | journal = Psychophysiology | volume = 30 | issue = 2 | pages = 183–96 | date = March 1993 | pmid = 8434081 | doi = 10.1111/j.1469-8986.1993.tb01731.x }}</ref> RSA was firstly recognized by [[Carl Ludwig]] but its genesis and understanding it is still nowadays largely discussed.<ref name=":2">{{Citation | vauthors = De Burgh Daly M | title=Interactions Between Respiration and Circulation|date=1985 |encyclopedia=Comprehensive Physiology|pages=529–594|publisher=John Wiley & Sons, Inc. |doi=10.1002/cphy.cp030216|isbn=9780470650714 }}</ref> RSA has been observed in human from early stages of life as well as in adults.<ref>{{cite journal | vauthors = Hathorn MK | title = Respiratory sinus arrhythmia in new-born infants | journal = The Journal of Physiology | volume = 385 | pages = 1–12 | date = April 1987 | pmid = 3656159 | pmc = 1192333 }}</ref><ref name=":1" /> Moreover, RSA is an mechanism which can be consistently found in several different species.<ref>{{cite journal | vauthors = Myers MM, Fifer W, Haiken J, Stark RI | title = Relationships between breathing activity and heart rate in fetal baboons | journal = The American Journal of Physiology | volume = 258 | issue = 6 Pt 2 | pages = R1479-85 | date = June 1990 | pmid = 2360694 | doi = 10.1152/ajpregu.1990.258.6.R1479 }}</ref><ref>{{cite journal | vauthors = Hayano J, Yasuma F, Okada A, Mukai S, Fujinami T | title = Respiratory sinus arrhythmia. A phenomenon improving pulmonary gas exchange and circulatory efficiency | journal = Circulation | volume = 94 | issue = 4 | pages = 842–7 | date = August 1996 | pmid = 8772709 }}</ref><ref>{{cite journal | vauthors = Castellini MA, Rea LD, Sanders JL, Castellini JM, Zenteno-Savin T | title = Developmental changes in cardiorespiratory patterns of sleep-associated apnea in northern elephant seals | journal = The American Journal of Physiology | volume = 267 | issue = 5 Pt 2 | pages = R1294-301 | date = November 1994 | pmid = 7977857 | doi = 10.1152/ajpregu.1994.267.5.R1294 }}</ref>
Respiratory sinus arrhythmia (RSA) is typically a benign, variation in heart rate that occurs during each breathing cycle heart rate increases and decreases .<ref name=":1"> |title= |==2=|= |=|=}}</ref> but is still .<ref name=":2">{{Citation | vauthors = De Burgh Daly M | =Interactions Between Respiration and Circulation|date=1985 |encyclopedia=Comprehensive Physiology|pages=529–594|publisher=John Wiley & Sons, Inc. |doi=10.1002/cphy.cp030216|isbn=9780470650714 }}</ref> has been observed in from early stages of life <ref>{{cite journal | vauthors = Hathorn MK | title = Respiratory sinus arrhythmia in new-born infants | journal = The Journal of Physiology | volume = 385 | pages = 1–12 | date = April 1987 | pmid = 3656159 | pmc = 1192333 }}</ref><ref name=":1" /> is found in several different species.<ref>{{cite journal | vauthors = Myers MM, Fifer W, Haiken J, Stark RI | title = Relationships between breathing activity and heart rate in fetal baboons | journal = The American Journal of Physiology | volume = 258 | issue = 6 Pt 2 | pages = | date = June 1990 | pmid = 2360694 | doi = 10.1152/ajpregu.1990.258.6.R1479 }}</ref><ref>{{cite journal | vauthors = Hayano J, Yasuma F, Okada A, Mukai S, Fujinami T | title = Respiratory sinus arrhythmia. A phenomenon improving pulmonary gas exchange and circulatory efficiency | journal = Circulation | volume = 94 | issue = 4 | pages = 842–7 | date = August 1996 | pmid = 8772709 }}</ref><ref>{{cite journal | vauthors = Castellini MA, Rea LD, Sanders JL, Castellini JM, Zenteno-Savin T | title = Developmental changes in cardiorespiratory patterns of sleep-associated apnea in northern elephant seals | journal = The American Journal of Physiology | volume = 267 | issue = 5 Pt 2 | pages = | date = November 1994 | pmid = 7977857 | doi = 10.1152/ajpregu.1994.267.5.R1294 }}</ref>


During [[inhalation]] [[Thoracic diaphragm|intra-thoracic pressure]] lowers due to the contraction and downward movement of the [[Diaphragmatic breathing|diaphragm]] and the expansion of the chest cavity. Atrial pressure is also lowered as a result, enabling and increased blood flow to the heart. Such increase in blood volume towards the heart cavities triggers [[baroreceptor]]s which act to diminish vagal tone. Subsequently, heart rate increases.<ref name=":1" />
During [[inhalation]] [[Thoracic diaphragm|intra-thoracic pressure]] lowers due to the contraction and downward movement of the [[Diaphragmatic breathing|diaphragm]] and the expansion of the chest cavity. Atrial pressure is also lowered as a result, increased blood flow to the heart in [[baroreceptor]]s vagal tone. heart rate.<ref name=":1" />


On the opposite during [[exhalation]], the diaphragm relaxes, moving upward it decreases the size of the chest cavity, causing a subsequent increase in intrathoracic pressure. This increase in pressure inhibits [[Venous return curve|venous return]] to the heart resulting in both reduced atrial expansion and minor activation of baroreceptors. Given the reduced baroreceptor activation, vagal tone is not suppressed as during inhalation so that it can exert its ability in decreasing heart rate.<ref name=":1" />
[[exhalation]], the diaphragm relaxes, moving upward decreases the size of the chest cavity, causing increase in intrathoracic pressure. This increase in pressure inhibits [[Venous return curve|venous return]] to the heart resulting in both reduced atrial expansion and activation of baroreceptors. the vagal tone heart rate.<ref name=":1" />
[[File:VivoSenseHR vs Vt.jpg|thumb|Heart rate (HR) (first row), tidal volume (Vt) (second row), Vt and superimposed HR (third row). It is clearly visible the HR modulation: HR increases with inspiration and decreases with expiration.|274x274px]]
[[File:VivoSenseHR vs Vt.jpg|thumb|Heart rate (HR) (first row), tidal volume (Vt) (second row), Vt and superimposed HR (third row). is clearly visible: HR increases with inspiration and decreases with expiration.|274x274px]]
[[File:RSA_neonatal_ECG+RESP+HR.png|thumb|274x274px|Heart rate (HR) (first row), ECG signal (ECG) (second row), and respiration (third row) for a newborn subject in a 15-seconds recording. HR expresses oscillations synchronous with respect to respiration.]]
[[File:+RESP+HR.png|thumb|274x274px|Heart rate (HR) (first row), ECG signal (ECG) (second row), and respiration (third row) for a newborn subject in a 15-seconds recording. HR expresses oscillations synchronous with respect to respiration.]]
[[File:RSA Bartsch method.png|thumb|RSA magnitude estimation based on a multivariate approach based on joint analysis of ECG and respiration.<ref name=":8" /> The green line shows the heart rate variations averaged over several breathing cycles. It is clearly visible heart rate increase-decrease trend which is typical of RSA.|274x274px]]
[[File:RSA Bartsch method.png|thumb|RSA magnitude estimation based on a multivariate approach based on joint analysis of ECG and respiration.<ref name=":8" /> The green line shows the heart rate variations averaged over several breathing cycles. clearly typical of RSA.|274x274px]]


==== RSA as a vagal tone estimator ====
==== RSA as a vagal tone estimator ====
As previously described, it is nowadays established that the two division of the autonomic nervous system influence each other reciprocally and independently so more and more measures able to discriminate the two contributions have been developed. In recent years, several studies have been published highlighting the quantification of RSA as a reliable tool to investigate vagal tone in a noninvasive way. Such investigations encompass physiological, behavioral, and several clinical studies.<ref>{{cite journal | vauthors = Hayano J, Sakakibara Y, Yamada M, Kamiya T, Fujinami T, Yokoyama K, Watanabe Y, Takata K | title = Diurnal variations in vagal and sympathetic cardiac control | journal = The American Journal of Physiology | volume = 258 | issue = 3 Pt 2 | pages = H642-6 | date = March 1990 | pmid = 2316678 | doi = 10.1152/ajpheart.1990.258.3.H642 }}</ref><ref>{{Citation|last=Porges|first=Stephen W. | name-list-format = vanc | chapter=Respiratory Sinus Arrhythmia: Physiological Basis, Quantitative Methods, and Clinical Implications|date=1986 | title =Cardiorespiratory and Cardiosomatic Psychophysiology|pages=101–115|publisher=Springer US |doi=10.1007/978-1-4757-0360-3_7|isbn=9781475703627 }}</ref><ref>{{cite journal | vauthors = Pagani M, Lombardi F, Guzzetti S, Rimoldi O, Furlan R, Pizzinelli P, Sandrone G, Malfatto G, Dell'Orto S, Piccaluga E | title = Power spectral analysis of heart rate and arterial pressure variabilities as a marker of sympatho-vagal interaction in man and conscious dog | journal = Circulation Research | volume = 59 | issue = 2 | pages = 178–93 | date = August 1986 | pmid = 2874900 | doi = 10.1161/01.RES.59.2.178 }}</ref> The main advantage in measuring of vagal tone by RSA is that such information are easily derivable from a single [[electrocardiography]] (ECG) recording.<ref>{{cite journal | vauthors = Grossman P, van Beek J, Wientjes C | title = A comparison of three quantification methods for estimation of respiratory sinus arrhythmia | journal = Psychophysiology | volume = 27 | issue = 6 | pages = 702–14 | date = November 1990 | pmid = 2100356 }}</ref> At the same time, novel methodologies started addressing RSA quantification by a multivariate approach thus not considering ECG only but the interrelationship of ECG and [[Respiratory system|respiration]].<ref>{{cite journal | vauthors = Dick TE, Hsieh YH, Dhingra RR, Baekey DM, Galán RF, Wehrwein E, Morris KF | title = Cardiorespiratory coupling: common rhythms in cardiac, sympathetic, and respiratory activities | journal = Progress in Brain Research | volume = 209 | pages = 191–205 | date = 2014 | pmid = 24746049 | pmc = 4052709 | doi = 10.1016/b978-0-444-63274-6.00010-2 | publisher = Elsevier | isbn = 9780444632746 }}</ref><ref name=":8">{{cite journal | vauthors = Bartsch RP, Schumann AY, Kantelhardt JW, Penzel T, Ivanov PC | title = Phase transitions in physiologic coupling | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 109 | issue = 26 | pages = 10181–6 | date = June 2012 | pmid = 22691492 | pmc = 3387128 | doi = 10.1073/pnas.1204568109 }}</ref>
is as a vagal tone in physiological, behavioral, and several clinical studies.<ref>{{cite journal | vauthors = Hayano J, Sakakibara Y, Yamada M, Kamiya T, Fujinami T, Yokoyama K, Watanabe Y, Takata K | title = Diurnal variations in vagal and sympathetic cardiac control | journal = The American Journal of Physiology | volume = 258 | issue = 3 Pt 2 | pages = | date = March 1990 | pmid = 2316678 | doi = 10.1152/ajpheart.1990.258.3.H642 }}</ref><ref>{{Citation|last=Porges|first=Stephen W. | name-list- = vanc | chapter=Respiratory Sinus Arrhythmia: Physiological Basis, Quantitative Methods, and Clinical Implications|date=1986 | title =Cardiorespiratory and Cardiosomatic Psychophysiology|pages=101–115|publisher=Springer US |doi=10.1007/978-1-4757-0360-3_7|isbn=9781475703627 }}</ref><ref>{{cite journal | vauthors = Pagani M, Lombardi F, Guzzetti S, Rimoldi O, Furlan R, Pizzinelli P, Sandrone G, Malfatto G, Dell'Orto S, Piccaluga E | title = Power spectral analysis of heart rate and arterial pressure variabilities as a marker of sympatho-vagal interaction in man and conscious dog | journal = Circulation Research | volume = 59 | issue = 2 | pages = 178–93 | date = August 1986 | pmid = 2874900 | doi = 10.1161/01.RES.59.2.178 [[electrocardiography]] (ECG) recording<ref>{{cite journal | vauthors = Grossman P, van Beek J, Wientjes C | title = A comparison of three quantification methods for estimation of respiratory sinus arrhythmia | journal = Psychophysiology | volume = 27 | issue = 6 | pages = 702–14 | date = November 1990 | pmid = 2100356 }}</ref> the ECG and [[Respiratory system|respiration]].<ref>{{cite | vauthors = Dick TE, Hsieh YH, Dhingra RR, Baekey DM, Galán RF, Wehrwein E, Morris KF | = Cardiorespiratory | = Progress in Brain Research | volume = 209 | pages = 191–205 | date = 2014 | pmid = 24746049 | pmc = 4052709 | doi = 10.1016/b978-0-444-63274-6.00010-2 | publisher = Elsevier | isbn = 9780444632746 }}</ref><ref name=":8">{{cite journal | vauthors = Bartsch RP, Schumann AY, Kantelhardt JW, Penzel T, Ivanov PC | title = Phase transitions in physiologic coupling | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 109 | issue = 26 | pages = 10181–6 | date = June 2012 | pmid = 22691492 | pmc = 3387128 | doi = 10.1073/pnas.1204568109 }}</ref>

On the opposite, vagal tone quantification by means of RSA has been questioned by many authors.<ref name=":2" /><ref>{{cite journal | vauthors = Grossman P, Karemaker J, Wieling W | title = Prediction of tonic parasympathetic cardiac control using respiratory sinus arrhythmia: the need for respiratory control | journal = Psychophysiology | volume = 28 | issue = 2 | pages = 201–16 | date = March 1991 | pmid = 1946886 }}</ref> It has been argued that RSA is unequivocally related to vagal control but it also clear that is determined by two different mechanisms namely: vagal tonic and vagal phasic. The former processes exhibit different dynamics and origins so that it is crucial to be able to differentiate their contributions to RSA. Furthermore, it has been observed that tonic and phasic components are distinct yet not completely independent one each other.<ref name=":1" />

Despite the nowadays limitations in RSA quantification, it is considered a promising, noninvasive and reliable index of vagal control of the heart, thus an indirect estimator of vagal tone.<ref name=":1" />

====Biological findings====
⚫
The main hypothesis capable of explaining the reason behind the correlation of RSA and vagal tone describes RSA as an intrinsic resting function of the cardiopulmonary system.<ref name=":3">{{cite journal | vauthors = Hayano J, Yasuma F | title = Hypothesis: respiratory sinus arrhythmia is an intrinsic resting function of cardiopulmonary system | journal = Cardiovascular Research | volume = 58 | issue = 1 | pages = 1–9 | date = April 2003 | pmid = 12667941 | doi = 10.1016/S0008-6363(02)00851-9 }}</ref> The theory suggest that in animals and humans RSA may eventually contribute to energy saving for both cardiac and respiratory systems thus reducing the heart rate and related heartbeats numbers. Furthermore, RSA could save energy expenditure by suppressing ineffective ventilation during the ebb of [[perfusion]] (delivery of blood from arteries to capillaries for oxygenation and nutrition).<ref>{{cite journal | vauthors = Ben-Tal A, Shamailov SS, Paton JF | title = Evaluating the physiological significance of respiratory sinus arrhythmia: looking beyond ventilation-perfusion efficiency | journal = The Journal of Physiology | volume = 590 | issue = 8 | pages = 1989–2008 | date = April 2012 | pmid = 22289913 | pmc = 3573317 | doi = 10.1113/jphysiol.2011.222422 }}</ref><ref>{{cite journal | vauthors = Hayano J, Yasuma F, Okada A, Mukai S, Fujinami T | title = Respiratory sinus arrhythmia. A phenomenon improving pulmonary gas exchange and circulatory efficiency | journal = Circulation | volume = 94 | issue = 4 | pages = 842–7 | date = August 1996 | pmid = 8772709 | doi = 10.1161/01.cir.94.4.842 }}</ref>


====Evolution and physiology====
In the physiological fields, RSA has been found to increase in subjects in resting state and to decrease in state of stress or tension.<ref name=":3" /> RSA is increased in supine position and decreased in prone position. RSA is on average higher and more pronounced during day time with respect to night time.<ref name=":3" /> RSA have also been extensively used to quantify vagal tone withdrawal in [[Tilt table test|graded orthostatic tilt]].<ref name=":4" /><ref name=":6">{{cite journal | vauthors = Lewis GF, Furman SA, McCool MF, Porges SW | title = Statistical strategies to quantify respiratory sinus arrhythmia: are commonly used metrics equivalent? | journal = Biological Psychology | volume = 89 | issue = 2 | pages = 349–64 | date = February 2012 | pmid = 22138367 | pmc = 3269511 | doi = 10.1016/j.biopsycho.2011.11.009 }}</ref>
⚫
the <ref name=":3">{{ journal|=HayanoYasuma|title=Hypothesis: respiratory sinus arrhythmia is an intrinsic resting function of cardiopulmonary system|journal=Cardiovascular Research|volume=58|issue=1|pages=1–9|doi=10.1016/-6363(02)00851-9}}</ref> and by suppressing ineffective ventilation during the ebb of [[perfusion]] (delivery of blood from arteries to capillaries for oxygenation and nutrition).<ref>{{cite journal | vauthors = Ben-Tal A, Shamailov SS, Paton JF | title = Evaluating the physiological significance of respiratory sinus arrhythmia: looking beyond ventilation-perfusion efficiency | journal = The Journal of Physiology | volume = 590 | issue = 8 | pages = 1989–2008 | date = April 2012 | pmid = 22289913 | pmc = 3573317 | doi = 10.1113/jphysiol.2011.222422 }}</ref><ref>{{cite journal | vauthors = Hayano J, Yasuma F, Okada A, Mukai S, Fujinami T | title = Respiratory sinus arrhythmia. A phenomenon improving pulmonary gas exchange and circulatory efficiency | journal = Circulation | volume = 94 | issue = 4 | pages = 842–7 | date = August 1996 | pmid = 8772709 | doi = 10.1161/01.cir.94.4.842 }}</ref>


Typically, expression of RSA decreases with age: it is pronounced in children and its magnitude tends to gradually disappear once a subject approach adulthood.<ref name=":5">{{cite journal | vauthors = Graziano P, Derefinko K | title = Cardiac vagal control and children's adaptive functioning: a meta-analysis | journal = Biological Psychology | volume = 94 | issue = 1 | pages = 22–37 | date = September 2013 | pmid = 23648264 | pmc = 4074920 | doi = 10.1016/j.biopsycho.2013.04.011 }}</ref> However, adults in excellent cardiovascular health, such as endurance runners, swimmers, and cyclists, are likely to have a more pronounced RSA. Professional athletes on average maintain very high vagal tone and consequently higher RSA levels. RSA has been found to becomes less prominent in individuals with diabetes and cardiovascular disease.<ref>{{cite journal | vauthors = Masi CM, Hawkley LC, Rickett EM, Cacioppo JT | title = Respiratory sinus arrhythmia and diseases of aging: obesity, diabetes mellitus, and hypertension | journal = Biological Psychology | volume = 74 | issue = 2 | pages = 212–23 | date = February 2007 | pmid = 17034928 | pmc = 1804292 | doi = 10.1016/j.biopsycho.2006.07.006 }}</ref>
RSA in to . and = /> to vagal tone in .<ref>{{cite journal | vauthors = , , , | title = : | journal = Biological Psychology | volume = | issue = 2 | pages = | date = February | pmid = | pmc = | doi = 10.1016/j.biopsycho... }}</ref>


Typically, expression of RSA decreases with age.<ref name=":5">{{cite journal | vauthors = Graziano P, Derefinko K | title = Cardiac vagal control and children's adaptive functioning: a meta-analysis | journal = Biological Psychology | volume = 94 | issue = 1 | pages = 22–37 | date = September 2013 | pmid = 23648264 | pmc = 4074920 | doi = 10.1016/j.biopsycho.2013.04.011 }}</ref> However, adults in excellent cardiovascular health, such as endurance runners, swimmers, and cyclists, are likely to have a more pronounced RSA. Professional athletes on average maintain very high vagal tone and consequently higher RSA levels. RSA is less prominent in individuals with diabetes and cardiovascular disease.<ref>{{cite journal | vauthors = Masi CM, Hawkley LC, Rickett EM, Cacioppo JT | title = Respiratory sinus arrhythmia and diseases of aging: obesity, diabetes mellitus, and hypertension | journal = Biological Psychology | volume = 74 | issue = 2 | pages = 212–23 | date = February 2007 | pmid = 17034928 | pmc = 1804292 | doi = 10.1016/j.biopsycho.2006.07.006 }}</ref>
====Psychological findings====
The majority of vagal tone research in the physiological field (social behavior, social interactions, and human psychology) have been focused on [[newborn]]s and [[child]]ren.<ref name=":5" /> The rational is to investigate children's adaptive functioning within a quantitative and reliable framework. Typically, researchers focus their attention on baseline vagal tone detection, treating it either as a potential predictor of behavior or examining its relationship with mental health (particularly [[emotion regulation]], [[anxiety]], and [[Internalizing disorder|internalizing]] and [[externalizing disorders]]).<ref>{{cite journal | vauthors = Connell AM, Hughes-Scalise A, Klostermann S, Azem T | title = Maternal depression and the heart of parenting: respiratory sinus arrhythmia and affective dynamics during parent-adolescent interactions | journal = Journal of Family Psychology | volume = 25 | issue = 5 | pages = 653–62 | date = October 2011 | pmid = 21875198 | doi = 10.1037/a0025225 }}</ref>


====Insights into psychology and disease====
The [[Polyvagal theory]] by [[Stephen Porges|Porges]] is considered as the most influential model able to describe the differences between basal vagal tone during steady state and vagal reactivity as a response to external stimuli.<ref>{{cite journal | vauthors = Porges SW | title = Orienting in a defensive world: mammalian modifications of our evolutionary heritage. A Polyvagal Theory | journal = Psychophysiology | volume = 32 | issue = 4 | pages = 301–18 | date = July 1995 | pmid = 7652107 | doi = 10.1111/j.1469-8986.1995.tb01213.x }}</ref><ref>{{cite journal | vauthors = Porges SW | title = The Polyvagal Theory: phylogenetic contributions to social behavior | journal = Physiology & Behavior | volume = 79 | issue = 3 | pages = 503–13 | date = August 2003 | pmid = 12954445 }}</ref><ref>{{cite journal | vauthors = Porges SW | title = Social engagement and attachment: a phylogenetic perspective | journal = Annals of the New York Academy of Sciences | volume = 1008 | pages = 31–47 | date = December 2003 | pmid = 14998870 }}</ref> The model describes vagal tone modifications a differential measure between vagal tone baseline and vagal tone activation during attention-demanding state. The theory states that successful vagal regulation is characterized by RSA suppression or withdrawal during attention tasks leading to increased metabolic output associated with heart rate increase.<ref name=":5" />
Vagal tone research has the potential to offer insight into social behavior, social interactions, and human psychology. Much of this work has been focused on [[newborn]]s and [[child]]ren.<ref name=":5" /> Baseline vagal tone can be used either as a potential predictor of behavior or as a signal of mental health (particularly [[emotion regulation]], [[anxiety]], and [[Internalizing disorder|internalizing]] and [[externalizing disorders]]).<ref>{{cite journal | vauthors = Connell AM, Hughes-Scalise A, Klostermann S, Azem T | title = Maternal depression and the heart of parenting: respiratory sinus arrhythmia and affective dynamics during parent-adolescent interactions | journal = Journal of Family Psychology | volume = 25 | issue = 5 | pages = 653–62 | date = October 2011 | pmid = 21875198 | doi = 10.1037/a0025225 }}</ref><ref name="Porges Doussard-Roosevelt Maiti 1994 pp. 167–86">{{cite journal | last1=Porges | first1=SW | last2=Doussard-Roosevelt | first2=JA | last3=Maiti | first3=AK | title=Vagal tone and the physiological regulation of emotion. | journal=Monographs of the Society for Research in Child Development | volume=59 | issue=2–3 | year=1994 | issn=0037-976X | pmid=7984159 | pages=167–86 | quote=A review of research indicates that baseline levels of cardiac vagal tone and vagal tone reactivity abilities are associated with behavioral measures of reactivity, the expression of emotion, and self-regulation skills. Thus, we propose that cardiac vagal tone can serve as an index of emotion regulation. Historically, the vagus and other components of the parasympathetic nervous system have not been incorporated in theories of emotion.| doi=10.1111/j.1540-5834.1994.tb01283.x | jstor=1166144 }}</ref>


The [[polyvagal theory]] by [[Stephen Porges|Porges]] is an influential model of how the vagal pathways respond to novelty and to stressful external stimuli.<ref name=":9">{{cite journal | vauthors = Porges SW | title = Orienting in a defensive world: mammalian modifications of our evolutionary heritage. A Polyvagal Theory | journal = Psychophysiology | volume = 32 | issue = 4 | pages = 301–18 | date = July 1995 | pmid = 7652107 | doi = 10.1111/j.1469-8986.1995.tb01213.x | doi-access = free }}</ref><ref>{{cite journal | vauthors = Porges SW | title = The Polyvagal Theory: phylogenetic contributions to social behavior | journal = Physiology & Behavior | volume = 79 | issue = 3 | pages = 503–13 | date = August 2003 | pmid = 12954445 | doi = 10.1016/S0031-9384(03)00156-2 | s2cid = 14074575 }}</ref><ref>{{cite journal | vauthors = Porges SW | title = Social engagement and attachment: a phylogenetic perspective | journal = Annals of the New York Academy of Sciences | volume = 1008 | issue = 1 | pages = 31–47 | date = December 2003 | pmid = 14998870 | doi = 10.1196/annals.1301.004 | bibcode = 2003NYASA1008...31P | s2cid = 1377353 }}</ref> The theory proposes that there are two vagal systems, one that is shared with [[reptile]]s and [[Amphibian|amphibia]] and a second, more recent, system that is unique to [[mammal]]s. The two pathways behave differently and can work against each other. This theory can account for several [[Psychophysiology|psychophysiological]] phenomena and [[psychosomatic illness]]es.<ref name=":9" /><ref name=":5" /> However, recent studies indicate that the vagal "system" described by Porges as being unique to mammals existed long before the evolution of mammals.<ref>{{cite journal |last1=Monteiro |first1=Diana |title=Cardiorespiratory interactions previously identified as mammalian are present in the primitive lungfish |journal=Science Advances |date=2018 |volume=4 |issue=2 |pages=eaaq0800 |doi=10.1126/sciadv.aaq0800 |pmid=29507882 |pmc=5833999 |bibcode=2018SciA....4..800M |doi-access=free }}</ref><ref>{{cite journal |last1=Taylor |first1=E. W. |title=Autonomic control of cardiorespiratory interactions in fish, amphibians and reptiles |journal=Brazilian Journal of Medical and Biological Research |date=2010 |volume=43 |issue=7 |pages=600–610 |doi=10.1590/S0100-879X2010007500044 |pmid=20464342 |doi-access=free |hdl=11449/21090 |hdl-access=free }}</ref>
Despite the hypothesized link between vagal tone reduction and social functioning as stated by Porges' theory, researchers have been focusing mainly on the analysis of basal vagal tone. Examples are the findings reporting lower baseline RSA in children with [[Autism Spectrum Disorders]] with respect to healthy controls.<ref>{{cite journal | vauthors = Patriquin MA, Scarpa A, Friedman BH, Porges SW | title = Respiratory sinus arrhythmia: a marker for positive social functioning and receptive language skills in children with autism spectrum disorders | journal = Developmental Psychobiology | volume = 55 | issue = 2 | pages = 101–12 | date = March 2013 | pmid = 22212893 | doi = 10.1002/dev.21002 }}</ref> Research indicates that children with more secure attachments with their mothers exhibited greater empathetic responsiveness, less social inhibition, and higher vagal tone, highlighting the vagus nerve's regulatory effect, as well as the quantification of vagal tone by means of RSA, as a predictor of emotional and social function.<ref name="vagal tone adolescents attachment style">{{cite journal|vauthors=Diamond LM, Fagundes CP, Butterworth MR|year=2012|title=Attachment style, vagal tone, and empathy during mother–adolescent interactions|journal=Journal of Research on Adolescence|volume=22|issue=1|pages=165–184|doi=10.1111/j.1532-7795.2011.00762.x}}</ref>


=== Additional heart rate variability parameters ===
=== ===
There are several methods of estimating vagal tone other than measuring RSA, including:
Vagal tone estimation based on heart rate is quantifiable by several parameters rather than the use of RSA only. Examples are indexes of beat-to-beat variability such as RMSSD reported by The Task Force of the [[European Society of Cardiology]] and [[Heart Rhythm Society]].<ref name=":7">{{cite journal | vauthors = | title = Heart rate variability. Standards of measurement, physiological interpretation, and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology | journal = European Heart Journal | volume = 17 | issue = 3 | pages = 354–81 | date = March 1996 | pmid = 8737210 }}</ref> [[Heart rate variability|Frequency analysis of heart rate]] in the range 0.15-0.4&nbsp;Hz has been reported to quantify vagal tone based on heart rate variability spectrum.<ref name=":6" /> In the specific context of vagal tone response to head up tilt, a measure of beat-to-beat variability (RMSSD) showed significant decreases following head-up tilts as reported by Myers.<ref>{{cite journal | vauthors = Myers MM, Elliott AJ, Odendaal HJ, Burd L, Angal J, Groenewald C, Nugent JD, Yang JS, Isler JR, Dukes KA, Robinson F, Fifer WP | title = Cardiorespiratory physiology in the safe passage study: protocol, methods and normative values in unexposed infants | journal = Acta Paediatrica | volume = 106 | issue = 8 | pages = 1260–1272 | date = August 2017 | pmid = 28419567 | pmc = 5530586 | doi = 10.1111/apa.13873 }}</ref> Another method employed to quantify vagal activity is the computation of high frequency spectral component of heart rate variability power spectral density.<ref name=":4" /><ref name=":7" /> An example for the latter described methodology is the change in sympatho-vagal balance during [[hypnosis]]. Results report hypnosis to affet heart rate variability, shifting the sympatho-vagal interaction toward an enhanced parasympathetic activity and reduction of the sympathetic tone.<ref>{{Cite journal|last=DeBenedittis|first=G.|last2=Cigada|first2=M.|last3=Bianchi|first3=A.|last4=Signorini|first4=M. G.|last5=Cerutti|first5=S.|date=April 1994|title=Autonomic changes during hypnosis: a heart rate variability power spectrum analysis as a marker of sympatho-vagal balance|journal=The International Journal of Clinical and Experimental Hypnosis|volume=42|issue=2|pages=140–152|doi=10.1080/00207149408409347|issn=0020-7144|pmid=8200716}}</ref>
of beat-to-beat variability such as RMSSD reported by The Task Force of the [[European Society of Cardiology]] and [[Heart Rhythm Society]].<ref name=":7">{{cite journal | title = Heart rate variability. Standards of measurement, physiological interpretation, and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology | journal = European Heart Journal | volume = 17 | issue = 3 | pages = 354–81 | date = March 1996 | pmid = 8737210 }}</ref> [[Heart rate variability|Frequency analysis of heart rate]] in the range 0..4&nbsp;Hz has been reported to quantify vagal tone.<ref name=":6" /><ref>{{cite journal | vauthors = Myers MM, Elliott AJ, Odendaal HJ, Burd L, Angal J, Groenewald C, Nugent JD, Yang JS, Isler JR, Dukes KA, Robinson F, Fifer WP | title = Cardiorespiratory physiology in the safe passage study: protocol, methods and normative values in unexposed infants | journal = Acta Paediatrica | volume = 106 | issue = 8 | pages = 1260–1272 | date = August 2017 | pmid = 28419567 | pmc = 5530586 | doi = 10.1111/apa.13873 }}</ref>
* Computation of the "power spectrum", or the ratio between the low frequency and high frequency spectral components, of heart rate variability.<ref name=":4" /><ref name=":7" /> This has been used to measure the change in sympatho-vagal balance during [[hypnosis]].<ref>{{cite journal | vauthors = DeBenedittis G, Cigada M, Bianchi A, Signorini MG, Cerutti S | title = Autonomic changes during hypnosis: a heart rate variability power spectrum analysis as a marker of sympatho-vagal balance | journal = The International Journal of Clinical and Experimental Hypnosis | volume = 42 | issue = 2 | pages = 140–52 | date = April 1994 | pmid = 8200716 | doi = 10.1080/00207149408409347 }}</ref>


==See also==
==See also==
*[[Autonomic nervous system]]
*[[Autonomic nervous system]]
*[[Parasympathetic nervous system]]
*[[Parasympathetic nervous system]]
*[[Vagus nerve]]
*[[Vagus nerve]]
*[[Vagus nerve stimulation]]
*[[Vagus nerve stimulation]]
*[[Heart rate variability]]
*[[Heart rate variability]]
* [[Sinus arrhythmia]]
* [[Bainbridge reflex]]


== References ==
== References ==
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[[Category:Heart]]
[[Category:Heart]]
[[Category:Physiology]]
[[Category:Physiology]]
[[Category:Psychology]]

Latest revision as of 18:24, 22 August 2024

Vagal tone is activity of the vagus nerve (the 10th cranial nerve) and a fundamental component of the parasympathetic branch of the autonomic nervous system. This branch of the nervous system is not under conscious control and is largely responsible for the regulation of several body compartments at rest. Vagal activity results in various effects, including: heart rate reduction, vasodilation/constriction of vessels, glandular activity in the heart, lungs, and digestive tract, liver, immune system regulation as well as control of gastrointestinal sensitivity, motility and inflammation.[1]

In this context, tone specifically refers to the continual nature of baseline parasympathetic action that the vagus nerve exerts. While baseline vagal input is constant, the degree of stimulation it exerts is regulated by a balance of inputs from sympathetic and parasympathetic divisions of the autonomic nervous system, with parasympathetic activity generally being dominant. Vagal tone is frequently used to assess heart function, and is also useful in assessing emotional regulation and other processes that alter, or are altered by, changes in parasympathetic activity.[2][3]

Measurements of vagal tone can be performed by means of either invasive or noninvasive procedures. Invasive procedures are in the minority and include vagus nerve stimulation by specific manual, breathing or electrical techniques. Noninvasive techniques mainly rely on the investigation of heart rate and heart rate variability.[4][5][6]

Noninvasive vagal tone quantification

[edit]

In most cases, vagal tone is not measured directly. Instead the processes affected by the vagus nerve – specifically heart rate and heart rate variability – are measured and used as a surrogate for vagal tone. Increased vagal tone (and thus vagal action) is generally associated with a lower heart rate and increased heart rate variability. However, during graded orthostatic tilt, vagal tone withdrawal is an indirect indicator of cardiovascular fitness.[7]

Vagal innervation of the heart

[edit]

Heart rate is largely controlled by the heart's internal pacemaker activity. In a healthy heart, the main pacemaker is a collection of cells on the border of the atria and vena cava called the sinoatrial node. Heart cells exhibit automaticity, the ability to generate electrical activity independent of external stimulation. The electrical activity spontaneously generated by the sinoatrial node sets the pace for the rest of the heart.[1]

In absence of external stimuli, sinoatrial pacing generally, while awake, maintains the heart rate in the range of 60–100 beats per minute (bpm).[8] The two branches of the autonomic nervous system work together to increase or slow the heart rate. The vagus nerve acts on the sinoatrial node, slowing its conduction and modulating vagal tone, via the neurotransmitter acetylcholine and downstream changes to ionic currents and calcium of heart cells.[4] Because of its effect on heart rate, and cardio health, vagal tone can be measured and understood by examining its correlation to heart rate modulation and heart rate variability.[5]

Respiratory sinus arrhythmia

[edit]

Respiratory sinus arrhythmia (RSA) is typically a benign, normal variation in heart rate that occurs during each breathing cycle: the heart rate increases when breathing in and decreases when breathing out.[1] RSA was first recognized by Carl Ludwig in 1847[9] but is still imperfectly understood.[10] It has been observed in humans from the early stages of life through adulthood,[11][1] and is found in several different species.[12][13][14]

During inhalation, the intra-thoracic pressure lowers due to the contraction and downward movement of the diaphragm and the expansion of the chest cavity. Atrial pressure is also lowered as a result, causing increased blood flow to the heart, which in turn decreases baroreceptors firing response which diminishes vagal tone. This causes an increase in heart rate.[1]

During exhalation, the diaphragm relaxes, moving upward, and decreases the size of the chest cavity, causing an increase in intrathoracic pressure. This increase in pressure inhibits venous return to the heart resulting in both reduced atrial expansion and increased activation of baroreceptors. This relieves the suppression of vagal tone and leads to a decreased heart rate.[1]

Heart rate (HR) (first row), tidal volume (Vt) (second row), Vt and superimposed HR (third row). The HR modulation is clearly visible: HR increases with inspiration and decreases with expiration.
Heart rate (HR) (first row), ECG signal (ECG) (second row), and respiration (third row) for a newborn subject in a 15-seconds recording. HR expresses oscillations synchronous with respect to respiration.
RSA magnitude estimation based on a multivariate approach based on joint analysis of ECG and respiration.[15] The green line shows the heart rate variations averaged over several breathing cycles. This clearly shows the trends that are typical of RSA.

RSA as a vagal tone estimator

[edit]

Respiratory sinus arrhythmia is frequently used as a noninvasive method for investigating vagal tone, in physiological, behavioral, and several clinical studies.[16][17][18] This can be done using electrocardiography (ECG) recording,[19] although other methods are also being developed that take advantage of the interactions between ECG and respiration.[20][15] Interpretation of RSA measurements must be done with care, however, as several factors including differences between individuals can change the relationship between RSA and vagal tone.[21]

Evolution and physiology

[edit]

It has been suggested that RSA may have evolved to save energy for both cardiac and respiratory systems by reducing the heart rate[22] and by suppressing ineffective ventilation during the ebb of perfusion (delivery of blood from arteries to capillaries for oxygenation and nutrition).[23][24]

RSA has been found to increase in subjects in resting state and to decrease in states of stress or tension. It is increased in supine position and decreased in prone position, and is on average higher and more pronounced during the day as compared to the night.[22] RSA has also been extensively used to quantify vagal tone withdrawal in graded orthostatic tilt.[7][25]

Typically, expression of RSA decreases with age.[26] However, adults in excellent cardiovascular health, such as endurance runners, swimmers, and cyclists, are likely to have a more pronounced RSA. Professional athletes on average maintain very high vagal tone and consequently higher RSA levels. RSA is less prominent in individuals with diabetes and cardiovascular disease.[27]

Insights into psychology and disease

[edit]

Vagal tone research has the potential to offer insight into social behavior, social interactions, and human psychology. Much of this work has been focused on newborns and children.[26] Baseline vagal tone can be used either as a potential predictor of behavior or as a signal of mental health (particularly emotion regulation, anxiety, and internalizing and externalizing disorders).[28][29]

The polyvagal theory by Porges is an influential model of how the vagal pathways respond to novelty and to stressful external stimuli.[30][31][32] The theory proposes that there are two vagal systems, one that is shared with reptiles and amphibia and a second, more recent, system that is unique to mammals. The two pathways behave differently and can work against each other. This theory can account for several psychophysiological phenomena and psychosomatic illnesses.[30][26] However, recent studies indicate that the vagal "system" described by Porges as being unique to mammals existed long before the evolution of mammals.[33][34]

Other estimates of vagal tone

[edit]

There are several methods of estimating vagal tone other than measuring RSA, including:

See also

[edit]

References

[edit]
  1. ^ a b c d e f Berntson GG, Cacioppo JT, Quigley KS (March 1993). "Respiratory sinus arrhythmia: autonomic origins, physiological mechanisms, and psychophysiological implications". Psychophysiology. 30 (2): 183–96. doi:10.1111/j.1469-8986.1993.tb01731.x. PMID 8434081.
  2. ^ Diamond LM, Fagundes CP, Butterworth MR (2011). "Attachment Style, Vagal Tone, and Empathy During Mother-Adolescent Interactions". Journal of Research on Adolescence. 22 (1): 165–184. doi:10.1111/j.1532-7795.2011.00762.x.
  3. ^ Grossman P, Wilhelm FH, Spoerle M (August 2004). "Respiratory sinus arrhythmia, cardiac vagal control, and daily activity". American Journal of Physiology. Heart and Circulatory Physiology. 287 (2): H728–34. doi:10.1152/ajpheart.00825.2003. PMID 14751862.
  4. ^ a b Howland RH (June 2014). "Vagus Nerve Stimulation". Current Behavioral Neuroscience Reports. 1 (2): 64–73. doi:10.1007/s40473-014-0010-5. PMC 4017164. PMID 24834378.
  5. ^ a b Porges SW, Doussard-Roosevelt JA, Maiti AK (2008). "Vagal tone and the physiological regulation of emotion". Monographs of the Society for Research in Child Development. 59 (2–3): 167–86. doi:10.1111/j.1540-5834.1994.tb01283.x. PMID 7984159.
  6. ^ Brock C, Jessen N, Brock B, Jakobsen PE, Hansen TK, Rantanen JM, Riahi S, Dimitrova YK, Dons-Jensen A, Aziz Q, Drewes AM, Farmer AD (October 2017). "Cardiac vagal tone, a non-invasive measure of parasympathetic tone, is a clinically relevant tool in Type 1 diabetes mellitus". Diabetic Medicine. 34 (10): 1428–1434. doi:10.1111/dme.13421. PMID 28703868. S2CID 25030686.
  7. ^ a b c Montano N, Ruscone TG, Porta A, Lombardi F, Pagani M, Malliani A (October 1994). "Power spectrum analysis of heart rate variability to assess the changes in sympathovagal balance during graded orthostatic tilt". Circulation. 90 (4): 1826–31. doi:10.1161/01.CIR.90.4.1826. PMID 7923668.
  8. ^ Nunan D, Sandercock GR, Brodie DA (November 2010). "A quantitative systematic review of normal values for short-term heart rate variability in healthy adults". Pacing and Clinical Electrophysiology. 33 (11): 1407–17. doi:10.1111/j.1540-8159.2010.02841.x. PMID 20663071. S2CID 44378765.
  9. ^ Ludwig, Carl (1847). "On the influence of respiratory movements on blood flow in the aortic system [in German]". Arch Anat Physiol Leipzig. 13: 242–302.
  10. ^ De Burgh Daly M (1985), "Interactions Between Respiration and Circulation", Comprehensive Physiology, John Wiley & Sons, Inc., pp. 529–594, doi:10.1002/cphy.cp030216, ISBN 9780470650714
  11. ^ Hathorn MK (April 1987). "Respiratory sinus arrhythmia in new-born infants". The Journal of Physiology. 385: 1–12. doi:10.1113/jphysiol.1987.sp016480. PMC 1192333. PMID 3656159.
  12. ^ Myers MM, Fifer W, Haiken J, Stark RI (June 1990). "Relationships between breathing activity and heart rate in fetal baboons". The American Journal of Physiology. 258 (6 Pt 2): R1479–85. doi:10.1152/ajpregu.1990.258.6.R1479. PMID 2360694.
  13. ^ Hayano J, Yasuma F, Okada A, Mukai S, Fujinami T (August 1996). "Respiratory sinus arrhythmia. A phenomenon improving pulmonary gas exchange and circulatory efficiency". Circulation. 94 (4): 842–7. doi:10.1161/01.CIR.94.4.842. PMID 8772709.
  14. ^ Castellini MA, Rea LD, Sanders JL, Castellini JM, Zenteno-Savin T (November 1994). "Developmental changes in cardiorespiratory patterns of sleep-associated apnea in northern elephant seals". The American Journal of Physiology. 267 (5 Pt 2): R1294–301. doi:10.1152/ajpregu.1994.267.5.R1294. PMID 7977857.
  15. ^ a b Bartsch RP, Schumann AY, Kantelhardt JW, Penzel T, Ivanov PC (June 2012). "Phase transitions in physiologic coupling". Proceedings of the National Academy of Sciences of the United States of America. 109 (26): 10181–6. Bibcode:2012PNAS..10910181B. doi:10.1073/pnas.1204568109. PMC 3387128. PMID 22691492.
  16. ^ Hayano J, Sakakibara Y, Yamada M, Kamiya T, Fujinami T, Yokoyama K, Watanabe Y, Takata K (March 1990). "Diurnal variations in vagal and sympathetic cardiac control". The American Journal of Physiology. 258 (3 Pt 2): H642–6. doi:10.1152/ajpheart.1990.258.3.H642. PMID 2316678.
  17. ^ Porges SW (1986), "Respiratory Sinus Arrhythmia: Physiological Basis, Quantitative Methods, and Clinical Implications", Cardiorespiratory and Cardiosomatic Psychophysiology, Springer US, pp. 101–115, doi:10.1007/978-1-4757-0360-3_7, ISBN 9781475703627
  18. ^ Pagani M, Lombardi F, Guzzetti S, Rimoldi O, Furlan R, Pizzinelli P, Sandrone G, Malfatto G, Dell'Orto S, Piccaluga E (August 1986). "Power spectral analysis of heart rate and arterial pressure variabilities as a marker of sympatho-vagal interaction in man and conscious dog". Circulation Research. 59 (2): 178–93. doi:10.1161/01.RES.59.2.178. hdl:2434/205812. PMID 2874900.
  19. ^ Grossman P, van Beek J, Wientjes C (November 1990). "A comparison of three quantification methods for estimation of respiratory sinus arrhythmia". Psychophysiology. 27 (6): 702–14. doi:10.1111/j.1469-8986.1990.tb03198.x. PMID 2100356.
  20. ^ Dick TE, Hsieh YH, Dhingra RR, Baekey DM, Galán RF, Wehrwein E, Morris KF (2014). "Cardiorespiratory Coupling". The Central Nervous System Control of Respiration. Progress in Brain Research. Vol. 209. Elsevier. pp. 191–205. doi:10.1016/b978-0-444-63274-6.00010-2. ISBN 9780444632746. PMC 4052709. PMID 24746049.
  21. ^ Grossman, Paul; Taylor, Edwin W. (2007). "Toward understanding respiratory sinus arrhythmia: relations to cardiac vagal tone, evolution and biobehavioral functions". Biological Psychology. 74 (2): 263–285. doi:10.1016/j.biopsycho.2005.11.014. ISSN 0301-0511. PMID 17081672. S2CID 16818862.
  22. ^ a b Hayano, Junichiro; Yasuma, Fumihiko (2003-04-01). "Hypothesis: respiratory sinus arrhythmia is an intrinsic resting function of cardiopulmonary system". Cardiovascular Research. 58 (1): 1–9. doi:10.1016/s0008-6363(02)00851-9. ISSN 0008-6363. PMID 12667941.
  23. ^ Ben-Tal A, Shamailov SS, Paton JF (April 2012). "Evaluating the physiological significance of respiratory sinus arrhythmia: looking beyond ventilation-perfusion efficiency". The Journal of Physiology. 590 (8): 1989–2008. doi:10.1113/jphysiol.2011.222422. PMC 3573317. PMID 22289913.
  24. ^ Hayano J, Yasuma F, Okada A, Mukai S, Fujinami T (August 1996). "Respiratory sinus arrhythmia. A phenomenon improving pulmonary gas exchange and circulatory efficiency". Circulation. 94 (4): 842–7. doi:10.1161/01.cir.94.4.842. PMID 8772709.
  25. ^ a b Lewis GF, Furman SA, McCool MF, Porges SW (February 2012). "Statistical strategies to quantify respiratory sinus arrhythmia: are commonly used metrics equivalent?". Biological Psychology. 89 (2): 349–64. doi:10.1016/j.biopsycho.2011.11.009. PMC 3269511. PMID 22138367.
  26. ^ a b c Graziano P, Derefinko K (September 2013). "Cardiac vagal control and children's adaptive functioning: a meta-analysis". Biological Psychology. 94 (1): 22–37. doi:10.1016/j.biopsycho.2013.04.011. PMC 4074920. PMID 23648264.
  27. ^ Masi CM, Hawkley LC, Rickett EM, Cacioppo JT (February 2007). "Respiratory sinus arrhythmia and diseases of aging: obesity, diabetes mellitus, and hypertension". Biological Psychology. 74 (2): 212–23. doi:10.1016/j.biopsycho.2006.07.006. PMC 1804292. PMID 17034928.
  28. ^ Connell AM, Hughes-Scalise A, Klostermann S, Azem T (October 2011). "Maternal depression and the heart of parenting: respiratory sinus arrhythmia and affective dynamics during parent-adolescent interactions". Journal of Family Psychology. 25 (5): 653–62. doi:10.1037/a0025225. PMID 21875198.
  29. ^ Porges, SW; Doussard-Roosevelt, JA; Maiti, AK (1994). "Vagal tone and the physiological regulation of emotion". Monographs of the Society for Research in Child Development. 59 (2–3): 167–86. doi:10.1111/j.1540-5834.1994.tb01283.x. ISSN 0037-976X. JSTOR 1166144. PMID 7984159. A review of research indicates that baseline levels of cardiac vagal tone and vagal tone reactivity abilities are associated with behavioral measures of reactivity, the expression of emotion, and self-regulation skills. Thus, we propose that cardiac vagal tone can serve as an index of emotion regulation. Historically, the vagus and other components of the parasympathetic nervous system have not been incorporated in theories of emotion.
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  32. ^ Porges SW (December 2003). "Social engagement and attachment: a phylogenetic perspective". Annals of the New York Academy of Sciences. 1008 (1): 31–47. Bibcode:2003NYASA1008...31P. doi:10.1196/annals.1301.004. PMID 14998870. S2CID 1377353.
  33. ^ Monteiro, Diana (2018). "Cardiorespiratory interactions previously identified as mammalian are present in the primitive lungfish". Science Advances. 4 (2): eaaq0800. Bibcode:2018SciA....4..800M. doi:10.1126/sciadv.aaq0800. PMC 5833999. PMID 29507882.
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  36. ^ Myers MM, Elliott AJ, Odendaal HJ, Burd L, Angal J, Groenewald C, Nugent JD, Yang JS, Isler JR, Dukes KA, Robinson F, Fifer WP (August 2017). "Cardiorespiratory physiology in the safe passage study: protocol, methods and normative values in unexposed infants". Acta Paediatrica. 106 (8): 1260–1272. doi:10.1111/apa.13873. PMC 5530586. PMID 28419567.
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