Nervus vagus og inflammasjon

april 6, 2014 av Marius

Veldig omfattende litteratur studie av hvordan vagus påvirker betennelser.

https://www.duo.uio.no/bitstream/handle/10852/29480/ProsjektVogt.pdf?sequence=3

Autonomic system modification in zen practitioners

april 3, 2014 av Marius

Nevner mye om hvordan pustefrekvens påvirker HRV og andre faktorer. Og spesielt hvordan dette endrer den normale pusten på lang sikt.

http://www.ncbi.nlm.nih.gov/pubmed/24469560

http://www.indianjmedsci.org/article.asp?issn=0019-5359;year=2013;volume=67;issue=7;spage=161;epage=167;aulast=Fiorentini

Background: Meditation in its various forms is a traditional exercise with a potential benefit on well-being and health. On a psychosomatic level these exercises seem to improve the salutogenetic potential in man.Especially the cardiorespiratory interaction seems to play an important role since most meditation techniques make use of special low frequency breathing patterns regardless of whether they result from a deliberate guidance of breathing or other mechanisms, for example, the recitation of specific verse. During the different exercises of Zen meditation the depth and the duration of each respiratory cycle is determined only by the process of breathing. Respiratory manoeuvres during Zazen meditation may produce HR variability changes similar to those produces during biofeedback.Recognition that the respiratory sinus arrhythmia (RSA) was mediated by efferent vagal activity acting on the sinus node led investigators to attempt to quantify the fluctuations in R-R intervals that were related to breathing. Materials and Methods: Nine Zen practitioners with five years of experience took part in the study. Autonomic nervous system function was evaluated by heart rate variability (HRV) analysis during 24-hours ECG recording during zen meditation and at rest. Results: The data of this small observational study confirm that ZaZen breathing falls within the range of low frequency HR spectral bands. Our data suggest that the modification of HR spectral power remained also in normal day when the subject have a normal breathing. Conclusion: We suggest that the changes in the breathing rate might modify the chemoreflex and the continuous practice in slow breathing can reduce chemoreflex. This change in the automonic control of respiration can be permanent with a resetting of endogenous circulatory rhythms.

Figure 1: Power spectrum analysis of heart rate variability during zen meditation

Figure 2: Power spectrum analysis of heart rate variability to rest

In conclusion, repeated training to slow down breathing reduces the spontaneous breathing rate with long term effects on the cardiovascular control mechanisms. Indeed, when respiration slows to about 6 cycles/min, as in Zen practitioners and in the frequency range of the spontaneous LF oscillation, the cardiovascular fluctuations become maximal. The changes in the breathing rate might modify the chemoreflex and the continuous practice in slow breathing can reduce chemoreflex. This change in the autonomic control of respiration can be permanent with a resetting of endogenous circulatory rhythms.

Relationship between dysfunctional breathing patterns and ability to achieve target heart rate variability with features of «coherence» during biofeedback.

april 3, 2014 av Marius

Nevner hvordan en topp-pust relateres til lav HRV og problemer i hjerte/kar systemet.

http://www.ncbi.nlm.nih.gov/pubmed/22164811

Abstract

BACKGROUND:

Heart rate variability (HRV) biofeedback is a self-regulation strategy used to improve conditions including asthma, stress, hypertension, and chronic obstructive pulmonary disease. Respiratory muscle function affects hemodynamic influences on respiratory sinus arrhythmia (RSA), and HRV and HRV-biofeedback protocols often include slow abdominal breathing to achieve physiologically optimal patterns of HRV with power spectral distribution concentrated around the 0.1-Hz frequency and large amplitude. It is likely that optimal balanced breathing patterns and ability to entrain heart rhythms to breathing reflect physiological efficiency and resilience and that individuals with dysfunctional breathing patterns may have difficulty voluntarily modulating HRV and RSA. The relationship between breathing movement patterns and HRV, however, has not been investigated. This study examines how individuals’ habitual breathing patterns correspond with their ability to optimize HRV and RSA.

METHOD:

Breathing pattern was assessed using the Manual Assessment of Respiratory Motion (MARM) and the Hi Lo manual palpation techniques in 83 people with possible dysfunctional breathing before they attempted HRV biofeedback. Mean respiratory rate was also assessed. Subsequently, participants applied a brief 5-minute biofeedback protocol, involving breathing and positive emotional focus, to achieve HRV patterns proposed to reflect physiological «coherence» and entrainment of heart rhythm oscillations to other oscillating body systems.

RESULTS:

Thoracic-dominant breathing was associated with decreased coherence of HRV (r = -.463, P = .0001). Individuals with paradoxical breathing had the lowest HRV coherence (t(8) = 10.7, P = .001), and the negative relationship between coherence of HRV and extent of thoracic breathing was strongest in this group (r = -.768, P = .03).

CONCLUSION:

Dysfunctional breathing patterns are associated with decreased ability to achieve HRV patterns that reflect cardiorespiratory efficiency and autonomic nervous system balance. This suggests that dysfunctional breathing patterns are not only biomechanically inefficient but also reflect decreased physiological resilience. Breathing assessment using simple manual techniques such as the MARM and Hi Lo may be useful in HRV biofeedback to identify if poor responders require more emphasis on correction of dysfunctional breathing.

Slow Breathing Improves Arterial Baroreflex Sensitivity and Decreases Blood Pressure in Essential Hypertension

april 1, 2014 av Marius

Nevner hvordan 6 pust i minuttet øker HRV og vagus nervens effekt på hjertet. Nevner også hvordan CO2 synker ved 15 pust i minuttet og holdes normalt ved 6 pust i minuttet. De med hjerteproblemer har mye større reaksjon på CO2 enn andre, og generelt lavere nivå.

http://hyper.ahajournals.org/content/46/4/714.full

Sympathetic hyperactivity and parasympathetic withdrawal may cause and sustain hypertension. This autonomic imbalance is in turn related to a reduced or reset arterial baroreflex sensitivity and chemoreflex-induced hyperventilation. Slow breathing at 6 breaths/min increases baroreflex sensitivity and reduces sympathetic activity and chemoreflex activation, suggesting a potentially beneficial effect in hypertension. We tested whether slow breathing was capable of modifying blood pressure in hypertensive and control subjects and improving baroreflex sensitivity. Continuous noninvasive blood pressure, RR interval, respiration, and end-tidal CO₂ (CO₂-et) were monitored in 20 subjects with essential hypertension (56.4±1.9 years) and in 26 controls (52.3±1.4 years) in sitting position during spontaneous breathing and controlled breathing at slower (6/min) and faster (15/min) breathing rate. Baroreflex sensitivity was measured by autoregressive spectral analysis and “alpha angle” method. Slow breathing decreased systolic and diastolic pressures in hypertensive subjects (from 149.7±3.7 to 141.1±4 mm Hg, P<0.05; and from 82.7±3 to 77.8±3.7 mm Hg, P<0.01, respectively). Controlled breathing (15/min) decreased systolic (to 142.8±3.9 mm Hg; P<0.05) but not diastolic blood pressure and decreased RR interval (P<0.05) without altering the baroreflex. Similar findings were seen in controls for RR interval. Slow breathing increased baroreflex sensitivity in hypertensives (from 5.8±0.7 to 10.3±2.0 ms/mm Hg; P<0.01) and controls (from 10.9±1.0 to 16.0±1.5 ms/mm Hg; P<0.001) without inducing hyperventilation. During spontaneous breathing, hypertensive subjects showed lower CO₂ and faster breathing rate, suggesting hyperventilation and reduced baroreflex sensitivity (P<0.001 versus controls). Slow breathing reduces blood pressure and enhances baroreflex sensitivity in hypertensive patients. These effects appear potentially beneficial in the management of hypertension.

However, breathing at 6 breaths/min significantly increased the baroreflex sensitivity in hypertensive (from 5.8±0.7 to 10.3±2.0 ms/mm Hg; P<0.01) and control subjects (from 10.9±1.0 to 16.0±1.5 ms/mm Hg; P<0.001;Figure 2).

Hypertensive subjects showed a significantly higher resting respiratory rate (14.55±0.82 versus 11.76±1.00; P<0.05) and a significantly lower CO₂-et values compared with control subjects (Figure 3). During controlled breathing at 6/min, there were no significant changes in CO₂-et and in Vm. The lack of change in Vm, despite lower breathing rate, was attributable to a significant increase in Vt in hypertensives and controls. Controlled breathing at 15/min induced a marked decrease in CO₂-et, particularly in hypertensive subjects, and a marked relative increase in Vm and Vt (Figure 3).

We found that paced breathing, and particularly slow breathing at 6 cycle/min, reduces blood pressure in hypertensive patients. The reduction in blood pressure during slow breathing is associated with an increase in the vagal arm of baroreflex sensitivity, indicating a change in autonomic balance, related to an absolute or relative reduction in sympathetic activity.

This demonstrated that slow breathing is indeed capable of inducing a modification in respiratory and cardiovascular control, and that appropriate training could induce a long-term effect. In subjects with chronic congestive heart failure, a condition known to induce sympathetic and chemoreflex activation, slow breathing induced a reduction in chemoreflexes and an increase in baroreflex.^10,25 We have also shown that in these patients, 1-month training in slow breathing could induce prolonged benefits, even in terms of exercise capacity.²⁵

Hypercapnia Improves Tissue Oxygenation

mars 19, 2014 av Marius

Denne viser hvordan økt CO2 øker oksygenering og blodsirkulasjon i huden og i vevet. Studien er gjort på individer i narkose og med assistert pust med konstant volum på 10ml/kg og pustefrekvens mellom 11 og 14.

http://journals.lww.com/anesthesiology/Fulltext/2002/10000/Hypercapnia_Improves_Tissue_Oxygenation.9.aspx

Background: Wound infections are common, serious, surgical complications. Oxidative killing by neutrophils is the primary defense against surgical pathogens and increasing intraoperative tissue oxygen tension markedly reduces the risk of such infections. Since hypercapnia improves cardiac output and peripheral tissue perfusion, we tested the hypothesis that peripheral tissue oxygenation increases as a function of arterial carbon dioxide tension (Paco₂) in anesthetized humans.

Methods: General anesthesia was induced with propofol and maintained with sevoflurane in 30% oxygen in 10 healthy volunteers. Subcutaneous tissue oxygen tension (Psqo₂) was recorded from a subcutaneous tonometer. An oximeter probe on the upper arm measured muscle oxygen saturation. Cardiac output was monitored noninvasively. Paco₂ was adjusted to 20, 30, 40, 50, or 60 mmHg in random order with each concentration being maintained for 45 min.

Results: Increasing Paco₂ linearly increased cardiac index and Psqo₂: Psqo₂ = 35.42 + 0.77 (Paco₂), P < 0.001.

Conclusions: The observed difference in PsqO₂ is clinically important because previous work suggests that comparable increases in tissue oxygenation reduced the risk of surgical infection from −8% to 2 to 3%. We conclude that mild intraoperative hypercapnia increased peripheral tissue oxygenation in healthy human subjects, which may improve resistance to surgical wound infections.

This hypercapnia-induced increase in cardiac output results in higher tissue oxygen pressure. In the current study Psqo₂ went from 58 to 74 mmHg with only a 20-mmHg increase in Paco₂. This increase in Psqo₂ is likely to be clinically important because it is associated with a substantial reduction in the risk of surgical wound infection. ¹¹ These results suggest that maintaining slight hypercapnia is likely to reduce the risk of surgical wound infection. Carbon dioxide management thus joins the growing list of anesthetic factors that do or are likely to influence the risk of wound infection.

Hypercapnia appears to provide other benefits as well. ³⁵ For example, hypercapnia and hypercapnic acidosis decrease ischemia–reperfusion injury by inhibiting xanthine oxidase in an in vitro model of acute lung injury. ³⁶ Hypercapnia similarly improves functional recovery and coronary blood flow during hypercapnic acidosis in an isolated blood-perfused heart model. ³⁷ Furthermore, small tidal volume ventilation (associated with mild hypercapnia) and permissive hypercapnia have been shown to improve the outcome of patients with acute respiratory distress syndrome as a result of decreased mechanical stretch of the diseased pulmonary tissues. ^38,39

Hypercapnia also increases cerebral blood flow and decreases cerebrovascular resistance through dilation of arterioles whereas hypocapnia does the opposite. ^40,41 In a recent study, hyper- and hypocapnia were shown to influence brain oxygen tension in swine during hemorrhagic shock ⁴²; hyperventilation and the resulting hypocapnia (15–20 mmHg) decreased cerebral oxygen pressure a further 56%. Hypercapnia has been utilized clinically to improve cerebral perfusion during carotid endarterectomy ^43,44 and for emergency treatment of retinal artery occlusion. ⁴⁵