Structure and Biomechanics of Peripheral Nerves: Nerve Responses to Physical Stresses and Implications for Physical Therapist Practice

Denne sier mye om nervenes blodgjennomstrømmning. Spesielt interessant er avnittet om hvor lite trykk som skal til før blodgjennomstrømningen stopper. Om trykket opprettholdes i 8 timer vil det skje en skade i nerven. Så lite som 20 mm Hg er nok til at blodsirkluasjonen blir dårligere.

Simply placing the hand on a computer mouse was shown to increase the tunnel pressure from the resting 5 mm Hg to 16 to 21 mm Hg,79 and actively using the mouse to point and click increased the tunnel pressure to 28 to 33 mm Hg, a pressure high enough to reduce nerve blood flow.

In subjects with carpal tunnel syndrome, pressure in the carpal tunnel was 32 mm Hg with the wrist in a neutral position and rose to a mean of 110 mm Hg with full wrist extension in subjects with carpal tunnel syndrome.76 These tunnel pressures exceed the threshold of 20 to 30 mm Hg for vascular perfusion even at rest. Taken together, these findings suggest that even functional positions, such as the use of a computer keyboard and mouse, place the wrist in a position of increased carpal tunnel pressure, compromising nerve blood flow and placing people at risk for median nerve injury.

Arterial and endoneurial capillary blood flows were stopped at pressures of 50 to 70 mm Hg67 and 80 mm Hg,75 respectively. Interestingly, in humans, intraneural blood flow and sensory responses are blocked at extraneural tissue pressures 45 mm Hg below the mean arterial pressure.82 A compressive stress of only 30 mm Hg, if maintained for 2 hours, results in endoneurial edema,83 and, if maintained for 8 hours, results in endoneurial pressure high enough to subsequently impair blood flow.84 The endoneurial edema is thought to result from ischemic damage to endoneurial capillary endothelial cells and an alteration in the blood-nerve barrier. The same compressive stress of 30 mm Hg applied for 8 hours is sufficient to impair both anterograde axonal transport and retrograde axonal transport.85,86Increasing pressure results in greater tissue damage, as a compressive force of 150 mm Hg maintained for 30 minutes was shown to induce a degeneration of 30% of the distal fibers,48 and compressive forces of 200 and 400 mm Hg maintained for 2 hours were shown to block axonal transport for 1 and 3 days, respectively.87

The pathological consequences of prolonged compression include subperineurial edema; inflammation; deposition of fibrin; activation of endoneurial fibroblasts, mast cells, and macrophages; demyelination; axon degeneration; and fibrosis.83 Compression of a very long duration has been modeled in animals with loose ligatures,88 Silastic* tubes,89,90and pressure balloons placed within an anatomical tunnel.91 The pathological findings are thought to result from both inflammatory and cellular phenomena and include changes in the blood-nerve barrier, thickening of the perineurium and epineurium, thinning of myelin, demyelination and degeneration of axons in the fascicle periphery, and slowed nerve conduction velocity.

Differential blood flow responses to CO2 in human internal and external carotid and vertebral arteries

Denne viser hvordan CO2-responsen er litt forskjellige i forskjellige blodkar. Den er sterkere i blodkar inni hjernen enn i blodkar i kraniet, ansiktet og ryggraden. Blodkar i ryggraden har større respons enn blodkar i ansiktet, men mindre respons enn blodkar i hjernen.

Because of methodological limitations, almost all previous studies have evaluated the response of mean blood flow velocity (Vmean) in the middle cerebral artery (MCA) to changes in CO2 as a measure of CO2 reactivity across the whole brain (Aaslid et al. 1989Ainslie & Duffin, 2009Ainslie & Ogoh, 2009).


ICA, VA and BA CO2 reactivity was significantly higher during hypercapnia than during hypocapnia (ICA, P < 0.01; VA, P < 0.05; BA, P < 0.05), but ECA and MCA were not significantly different.

The major finding from the present study was that cerebral CO2 reactivity was significantly lower in the VA and its distal artery (BA) than in the ICA and its distal artery (MCA). These findings indicate that vertebro-basilar circulation has lower CO2 reactivity than internal carotid circulation. Our second major finding was that ECA blood flow was unresponsive to hypocapnia and hypercapnia, suggesting that CO2 reactivity of the external carotid circulation is markedly diminished compared to that of the cerebral circulation. These findings suggest that different CO2 reactivity may explain differences in CBF responses to physiological conditions (i.e. dynamic exercise and orthostatic stress) across areas in the brain and/or head.

Hypercapnic cerebral CO2 reactivity in global CBF was greater than the hypocapnic reactivity (Ide et al. 2003) (Table 3). The mechanisms underlying this greater reactivity to hypercapnia compared with hypocapnia may be related to a greater influence of vasodilator mediators on intracranial vascular tone compared with vasoconstrictive mediators (Toda & Okamura, 1998Ainslie & Duffin, 2009). In humans, Peebles et al.(2008) recently reported that, during hypercapnia, there is a large release of nitric oxide (NO) from the brain, whereas this response was absent during hypocapnia.

The difference in CO2 reactivity between vertebro-basilar territories (VA and BA) and the cerebral cortex (ICA and MCA) may be due to diverse characteristics of vasculature, e.g. regional microvascular density (Sato et al. 1984), basal vascular tone (Ackerman, 1973Haubrich et al. 2004Reinhard et al. 2008), autonomic innervation (Edvinsson et al. 1976Hamel et al. 1988) and regional heterogeneity in ion channels or production of NO (Iadecola & Zhang, 1994Gotoh et al. 2001).

Interestingly, the response of the ECA to changes in CO2 may be similar to other peripheral arteries. It has long been appreciated that the vasodilatory effect of hypercapnia is much more profound in cerebral than in peripheral vasculature, particularly leg (Lennox & Gibbs, 1932Ainslie et al. 2005) and brachial arteries (Miyazaki, 1973). These findings suggest that control of CO2 is particularly important in the cerebral circulation. The high resting metabolic requirements of the brain, compared with that of other vasculature, might be one reason why this circulatory arrangement is desirable (Ainslie et al. 2005). Specifically, high CO2 reactivity may be a way for the brain to match metabolism with flow (Ainslie et al. 2005).

Lower CO2reactivity in the vertebro-basilar system may be important for maintaining central respiratory function because Graphic in central chemoreceptors is regulated by Graphic and blood flow to maintain breathing stability.

In summary, our study shows that cerebral CO2 reactivity in the vertebro-basilar circulation is lower than that in the internal carotid circulation, while CO2 reactivity in the external carotid circulation is much lower compared with two other cerebral arteries. These findings indicate a difference in cerebral CO2 reactivity between different circulatory areas in the brain and head, which may explain different CBF responses to physiological stress. Lower CO2 reactivity in the vertebro-basilar system may be beneficial for preserving blood flow to the medulla oblongata to maintain vital systemic functions, while higher CO2 reactivity in the internal carotid system may imply a larger tolerance for varied blood flow in the cerebral cortex.

Morning attenuation in cerebrovascular CO2 reactivity in healthy humans is associated with a lowered cerebral oxygenation and an augmented ventilatory response to CO2

Denne beskriver hvordan blodkarenes respons på CO2 er dårligere om morgenen, og det er derfor det skjer flere slag og slikt om morgenen. Den nevner mange interessante prinsipper. Bl.a. at lavere vasomotor respons (på CO2) gir mindre oksygen til hjernen. Og at i opptil 20 sekunder etter en 20 sekunder holdning av pust (etter utpust) øker fortsatt oksygenmengden og blodgjennomstrømningen i hjernen. Nevner også at siden blodkarene i hjernen reagerer dårligere på CO2 om morgenen blir det lett at pusten over- eller underkompenserer, så pustemønsteret blir uregelmessig om morgenen. Spesielt om man har underliggende faremomenter som hjerte/karsykdommer.


Furthermore, our results suggest that morning cerebral tissue oxygenation might be reduced as a result of a decreased cerebrovascular responsiveness to CO2 or other factors, leading to a higher level of desaturation.

Our data indicate that the cerebrovascular reactivity to CO2 in healthy subjects is significantly reduced in the morning and is strongly associated with an augmented ventilatory response to CO2. It is likely that this reduction in MCAV CO2 reactivity, by reducing blood flow through medullary respiratory control centers, increases both the arterial-brain tissue PCO2 difference and the H+ concentration presented to the central chemoreceptor(s) (1144). In effect, it appears the brain tissue is more susceptible in the morning to changes in arterial PCO2, which could increase the likelihood of ventilatory overshoots and undershoots.

However, as was the case with the hypercapnic challenge, subjects holding their breath in the morning experienced a significantly blunted increase in MCAV compared with evening, likely a result of a reduced cerebrovascular responsiveness to CO2.

In conclusion, our results suggest that early morning reductions in cerebrovascular CO2 reactivity strongly influence the magnitude of the ventilatory response to CO2. This may have significant implications for breathing stability, increasing the chances of periodic breathing in the morning in patients with additional risk factors. The early morning reduction in cerebral oxygenation with hypercapnic challenge, mild hypoxemia, or during apnea may be a contributing factor in the high prevalence of early morning stroke. Whether differences in the responses of CBF, oxygenation, or V̇E to CO2challenge are associated with other risk factors for stroke, such as gender or age, remains to be elucidated.

CO2-beriket vann til fotbad

Å bade i CO2 beriket vann har vært brukt som medisin i alle år. Hellige og mirkauløse kilder har ofter vært vann med et høyt innhold av karbondioksid. Og det har blitt brukt i spa behandling i århundrer, spesielt i Bulgaria. Man finner Co2-rikt vann spesielt ved sovende og inaktive vulkaner.

CO2 er et veldig lite molekyl som diffunderer lett igjennom huden. I CO2-beriket vann kommer derfor CO2 inn i huden og inn til blodkarene i underhuden, hvor alle sansenerver ligger. Den økte CO2 en gjør at blodkarene rundt nervetrådene og i muskelvevet utvides (vasodilasjon) og at oksygene letter hopper av blodcellene slik at det kan bli brukt til energi i celler som vanligvis har lite tilgang på oksygen.

CO2 beriket vann kan vi lage selv på en svært enkel måte: blande Natron, Sitronsyre og vann. Begge disse stoffene fåes kjøpt på vanlig daglivarebutikk. Vannet begynner å bruse, og dette er CO2.

Studier nevner at man bør ha 900-1200 mg CO2 pr liter vann. Ved å måle pH kan vi regne med at vi har det når pH er nede på 5.

Vi kan se CO2 effekten på huden ved at det kommer tett-i-tett med ørsmå bobler. I f.eks. fotbad vil vi se at når vi tar foten opp fra vannet så er den rød, noe som er et tegn på økt blodsirkulasjon i huden.

For alle med nevropatier, diabetes, sår, nevromer, leggspenninger, restless leg syndrom, som lett blir sliten i bena av å gå, så vil dette være verdt et forsøk.

2-3 ganger i uka pleier å være den vanlige oppskriften. Noen studier har brukt det hver dag i mange uker. Spesielt når det gjelder diabetes sår.

Oppskrift: Bland 1 poseNatron med 2 poser Sitronsyre (blandingsforhold ca. 1:1) og hell innholdet i 5L vann. Det bruser veldig pga reaksjonen som lager CO2. Når du setter føttene nedi skal det komme mange små bobler som dekker huden. Etter 5-10 minutter vil huden som er under vann bli rød. Dette er et tegn på økt blodsirkulasjon.

5-15 minutter etter du er ferdig med fotbadet vil du sannsynligvis kjenne det prikker og strømmer ellers i kroppen også. Vanligvis kjennes det først og fremst i armer og bein, som er de stedene vi lettest kjenner økt blodsirkulasjon.

Her er noen studier som bekrefter effektene av CO2 beriket vann.

Beskriver det meste om balneotherapy, som det også heter. Inkludert kontraindikasjoner(hjerteproblemer og hypercapni som følge av lungeskade):

Table 4. Major Indicators for CO2 Balneotherapy

1. Hypertension, especially borderline hypertension

2. Arteriolar occlusion, Stages I and II

3. Functional arteriolar blood flow disorders

4. Microcirculatory disorders

5. Functional disorders of the heart

Beskriver alt om hvordan det øker blodsirkulasjon og oksygenmetning:

Viser at det øker blodsirkulasjonen i huden og oksygenmetningen i muskelvev hos de som lett blir trøtte i beina:

Viser at det øker blodsirkulasjon og produksjonen av blodkar (angiogenese):

Viser at det reparerer sår som ikke vil gro:

Viser at det reparerer muskelskade:

Viser at det reparerer muskelskade og atrofi (muskelsvikt) etter langtids post-operative sengeliggende:

Viser at det reduserer hjertefrekvens gjennom å dempe sympaticus aktivering (ikke ved å øke parasymptaticus aktivering):

Viser at det øker mitokondrier og fjerner syster:

Viser at det øker antioksidant status, reduserer frie radikaler og øker blodsirkulasjon i kapuillærene (mikrosirkulasjon):

Viser at det hjelper til å reparere sår etter operasjon:

Dr. Sircus sin forklaring av CO2 medisin som nevner mange måter å gjøre det på:

Denne artikkelen beskriver mye om historien til CO2-bad.

Mange bilder av diabetes sår (OBS: ikke for sarte sjeler) som blir regenerert i løpet av få uker med 20-30 min fotbad. Disse bruker 900-1000ppm CO2 konsentrasjon. Jeg er usikker på om det er mulig med å blande Sitronsyre og Natron:

Denne artikkelen beskriver de fleste sider ved forskjellig bruk av CO2 behandling. God gjennomgang av hvordan blodsirkluasjonen påvirkes.

Is recovery driven by central or peripheral factors? A role for the brain in recovery following intermittent-sprint exercise

Nevner svært mye spennende om stølhet (DOMS). Spesielt om hvor mye central sensitering har å si, og mye om hydrering (vann). Samt alt om betennelser og andre faktorer knyttet til DOMS. Sier bl.a. at glucogenlagre normaliseres etter 24 timer uavhengig av hva man spiser, men glykogen omsetningen i kroppen er begrenset i 2-3 dager etter. Nevner også at det er alle de perifere faktorene, sammen med de sentrale, som tilsammen skaper DOMS tilstanden.


Prolonged intermittent-sprint exercise (i.e., team sports) induce disturbances in skeletal muscle structure and function that are associated with reduced contractile function, a cascade of inflammatory responses, perceptual soreness, and a delayed return to optimal physical performance. In this context, recovery from exercise-induced fatigue is traditionally treated from a peripheral viewpoint, with the regeneration of muscle physiology and other peripheral factors the target of recovery strategies. The direction of this research narrative on post-exercise recovery differs to the increasing emphasis on the complex interaction between both central and peripheral factors regulating exercise intensity during exercise performance. Given the role of the central nervous system (CNS) in motor-unit recruitment during exercise, it too may have an integral role in post-exercise recovery. Indeed, this hypothesis is indirectly supported by an apparent disconnect in time-course changes in physiological and biochemical markers resultant from exercise and the ensuing recovery of exercise performance. Equally, improvements in perceptual recovery, even withstanding the physiological state of recovery, may interact with both feed-forward/feed-back mechanisms to influence subsequent efforts. Considering the research interest afforded to recovery methodologies designed to hasten the return of homeostasis within the muscle, the limited focus on contributors to post-exercise recovery from CNS origins is somewhat surprising. Based on this context, the current review aims to outline the potential contributions of the brain to performance recovery after strenuous exercise.

recovery strategies might be broadly differentiated as being either physiological (e.g., cryotherapy, hydrotherapy, massage, compression, sleep), pharmacological (e.g., non-steroidal anti-inflammatory medications) or nutritional (e.g., dietary supplements), all mean to limit continued post-exercise disturbances and inflammatory events within the exercised muscle cells. This peripheral focus emphasizes the importance of an accelerated return of structural integrity and functional capacity from below the neuromuscular junction.

Conceptually, if the brain is held as central to the process of performance declines (i.e., fatigue), it stands to reason that it would also have some role in post-exercise recovery (De Pauw et al., 2013).

Classically defined as an exercise-induced reduction in force generating capacity of the muscle, fatigue may be attributed to peripheral contractile failure, sub-optimal motor cortical output (supraspinal fatigue) and/or altered afferent inputs (spinal fatigue) innervating the active musculature (Gandevia, 2001).

Alternatively, concepts of residual fatigue remain predominately within the domain of peripherally driven mechanisms, such as blood flow, muscle glycogen repletion and clearance of metabolic wastes (Bangsbo et al., 2006).

The physical and biochemical changes observed during intermittent-sprint exercise have traditionally been interpreted in terms of metabolic capacity (Glaister, 2005). Indeed, lowered phosphocreatine concentrations (Dawson et al., 1997), reduced glycolytic regeneration of ATP (Gaitanos et al., 1993) and increasing H+ accumulation (Bishop et al., 2003) have all been associated with declining intermittent-sprint performance.

While reductions in muscle excitability after intermittent-sprint exercise have also been observed (Bishop, 2012), metabolic perturbations are rapidly recovered within minutes (Glaister, 2005).

The ultimate indicator of post-exercise recovery is the ability of the muscle to produce force i.e., performance outcomes.

Reductions in skeletal muscle function after intermittent-sprint exercise are often proposed to be caused by a range of peripherally-induced factors, including: intra-muscular glycogen depletion; increased muscle and blood metabolites concentrations; altered Ca++ or Na+-K+ pump function; increased skeletal muscle damage; excessive increases in endogenous muscle and core temperatures; and the reduction in circulatory function via reduced blood volume and hypohydration (Duffield and Coutts, 2011; Bishop, 2012; Nédélec et al., 2012).

Conversely, Krustrup et al. (2006) reported declines in intramuscular glycogen of 42 ± 6% in soccer players, with depleted or almost depleted glycogen stores in ~55% of type I fibers and ~25–45% of type II fibers reasoned to explain acute declines in sprint speed post-match. Importantly, muscle glycogen resynthesis after team sport activity is slow and may remain attenuated for 2–3 days (Nédélec et al., 2012). Such findings highlight the importance of nutrition in post-exercise recovery (Burke et al., 2006); yet it is noteworthy that muscle glycogen stores remain impaired 24 h after a soccer match, irrespective of carbohydrate intake and should be recognized as a factor in sustained post-match suppression of force (Bangsbo et al., 2006; Krustrup et al., 2011).

Mechanical disruptions to the muscle fiber are task dependant, though likely relate to the volume of acceleration, deceleration, directional change and inter-player contact completed (i.e., tackling or collisions) (McLellan et al., 2011; Duffield et al., 2012). Importantly, EIMD manifests in reduced voluntary force production that has been associated with the elevated expression of intracellular proteins (e.g., creatine kinase and C-reactive protein), swelling, restricted range of motion and muscle soreness (Cheung et al., 2003). Whilst it is generally accepted that lowering blood-based muscle damage profiles may hasten athletic recovery, mechanisms explaining the return of skeletal muscle function are somewhat ambiguous (Howatson and Van Someren, 2008).

Interestingly, markers of EIMD are also not closely associated with muscle soreness (Nosaka et al., 2002; Prasartwuth et al., 2005), though perceptual recovery is reportedly related with the recovery of maximal sprint speed (Cook and Beaven, 2013). While this raises questions in terms of the physiological underpinnings of muscle soreness, weaker relationships between EIMD and neuromuscular performance may suggest the potential for other drivers of recovery outside of peripheral (muscle damage or metabolic) factors alone.

Finally, while the relationship between hydration status and intermittent-sprint performance remains contentious (Edwards and Noakes, 2009), fluid deficits of 2–4% are common following team-sport exercise (Duffield and Coutts, 2011). Mild hypohydration reportedly demonstrates limited effects on anaerobic power and vertical jump performance (Hoffman et al., 1995; Cheuvront et al., 2006); however, some caution is required in interpreting these data as these testing protocols reflect only select components of team sport performance.

Nevertheless, the role of hydration in recovery should not be overlooked as changes in extracellular osmolarity are suggested to influence glucose and leucine kinetics (Keller et al., 2003). Further, the negative psychological associations (conscious or otherwise) derived from a greater perceptual effort incurred in a hypohydrated state may impact mental fatigue (Devlin et al., 2001; Mohr et al., 2010).

Rather, that the integrative regulation of whole body disturbances based on these peripheral factors, alongside central regulation may be relevant.

The Mechanisms of Manual Therapy in the Treatment of Musculoskeletal Pain: A Comprehensive Model

Nevner det meste rundt behandling av muskel og skjelett problemer, både usikkerheter, manglende diagnostisk spesifisitet, dårlig forhold mellom forklaringsmodelle og realitet, og foreslår nevrosentriske forklaringsmodeller. Viser til at spesifikk behandling ikke har bedre effekt enn uspesifikk behandling. Og til at den mekaniske teknikken setter igang en kaskade av nevrologiske effekter som resulterer i en behandlingeffekt.


Prior studies suggest manual therapy (MT) as effective in the treatment of musculoskeletal pain; however, the mechanisms through which MT exerts its effects are not established. In this paper we present a comprehensive model to direct future studies in MT. This model provides visualization of potential individual mechanisms of MT that the current literature suggests as pertinent and provides a framework for the consideration of the potential interaction between these individual mechanisms. Specifically, this model suggests that a mechanical force from MT initiates a cascade of neurophysiological responses from the peripheral and central nervous system which are then responsible for the clinical outcomes. This model provides clear direction so that future studies may provide appropriate methodology to account for multiple potential pertinent mechanisms.

Mechanical Stimulus 

First, only transient biomechanical effects are supported by studies which quantify motion (Colloca et al., 2006;Gal et al., 1997;Coppieters & Butler, 2007;Coppieters & Alshami, 2007) but not a lasting positional change (Tullberg et al., 1998;Hsieh et al., 2002). Second, biomechanical assessment is not reliable. Palpation for position and movement faults has demonstrated poor reliability (Seffinger et al., 2004;Troyanovich et al., 1998) suggesting an inability to accurately determine a specific area requiring MT.  Third, MT techniques lack precision as nerve biased techniques are not specific to a single nerve (Kleinrensink et al., 2000) and joint biased technique forces are dissipated over a large area (Herzog et al., 2001;Ross et al., 2004).

Finally, studies have reported improvements in signs and symptoms away from the site of application such as treating cervical pain with MT directed to the thoracic spine (Cleland et al., 2005;Cleland et al., 2007) and lateral epicondylitis with MT directed to the cervical spine (Vicenzino et al., 1996).

Subsequently, we suggest, that as illustrated by the model, a mechanical force is necessary to initiate a chain of neurophysiological responses which produce the outcomes associated with MT. 

Neurophysiological Mechanism 

Studies have measured associated responses of hypoalgesia and sympathetic activity following MT to suggest a mechanism of action mediated by the periaquaductal gray (Wright, 1995) and lessening of temporal summation following MT to suggest a mechanism mediated by the dorsal horn of the spinal cord (George et al., 2006) The model makes use of directly measurable associated responses to imply specific neurophysiological mechanisms when direct observations are not possible. The model categorizes neurophysiological mechanisms as those likely originating from a peripheral mechanism, spinal cord mechanisms, and/or supraspinal mechanisms.

Peripheral mechanism 

Musculoskeletal injuries induce an inflammatory response in the periphery which initiates the healing process and influences pain processing. Inflammatory mediators and peripheral nociceptors interact in response to injury and MT may directly affect this process. For example, (Teodorczyk-Injeyan et al., 2006) observed a significant reduction of blood and serum level cytokines in individuals receiving joint biased MT which was not observed in those receiving sham MT or in a control group. Additionally, changes of blood levels of β-endorphin, anandamide, N-palmitoylethanolamide, serotonin, (Degenhardt et al., 2007) and endogenous cannabinoids (McPartland et al., 2005) have been observed following MT. Finally, soft tissue biased MT has been shown to alter acute inflammation in response to exercise (Smith et al., 1994) and substance P levels in individuals with fibromyalgia (Field et al., 2002). Collectively, these studies suggest a potential mechanism of action of MT on musculoskeletal pain mediated by the peripheral nervous system for which mechanistic studies may wish to account. 

Spinal mechanisms 

MT may exert an effect on the spinal cord. For example, MT has been suggested to act as a counter irritant to modulate pain (Boal & Gillette, 2004) and joint biased MT is speculated to “bombard the central nervous system with sensory input from the muscle proprioceptors (Pickar & Wheeler, 2001).”Subsequently, a spinal cord mediated mechanism of MT must be considered and is accounted for in the model. Direct evidence for such an effect comes from a study (Malisza et al., 2003b) in which joint biased MT was applied to the lower extremity of rats following capsaicin injection. A spinal cord response was quantified by functional MRI during light touch to the hind paw. A trend was noted towards decreased activation of the dorsal horn of the spinal cord following the MT. The model uses associated neuromuscular responses following MT to provide indirect evidence for a spinal cord mediated mechanism. For example, MT is associated with hypoalgesia (George et al., 2006;Mohammadian et al., 2004;Vicenzino et al., 2001), afferent discharge (Colloca et al., 2000;Colloca et al., 2003), motoneuron pool activity (Bulbulian et al., 2002;Dishman & Burke, 2003), and changes in muscle activity (Herzog et al., 1999;Symons et al., 2000) all of which may indirectly implicate a spinal cord mediated effect.

Supraspinal mechanisms 

Finally, the pain literature suggests the influence of specific supraspinal structures in response to pain. Structures such as the anterior cingular cortex (ACC), amygdala, periaqueductal gray (PAG), and rostral ventromedial medulla (RVM) are considered instrumental in the pain experience.(Peyron et al., 2000;Vogt et al., 1996;Derbyshire et al., 1997;Iadarola et al., 1998;Hsieh et al., 1995;Oshiro et al., 2007;Moulton et al., 2005;Staud et al., 2007;Bee & Dickenson, 2007;Guo et al., 2006). Subsequently, the model considers potential supraspinal mechanisms of MT. Direct support for a supraspinal mechanism of action of MT comes from (Malisza et al., 2003a) who applied joint biased MT to the lower extremity of rats following capsaicin injection. Functional MRI of the supraspinal region quantified the response of the hind paw to light touch following the injection. A trend was noted towards decreased activation of the supraspinal regions responsible for central pain processing. The model accounts for direct measures of supraspinal activity along with associated responses such as autonomic responses (Moulson & Watson, 2006;Sterling et al., 2001;Vicenzino et al., 1998) (Delaney et al., 2002;Zhang et al., 2006), and opiod responses (Vernon et al., 1986) (Kaada & Torsteinbo, 1989) to indirectly imply a supraspinal mechanism. Additionally, variables such as placebo, expectation, and psychosocial factors may be pertinent in the mechanisms of MT (Ernst, 2000;Kaptchuk, 2002). For example expectation for the effectiveness of MT is associated with functional outcomes (Kalauokalani et al., 2001) and a recent systematic review of the literature has noted that joint biased MT is associated with improved psychological outcomes (Williams et al., 2007). For this paper we categorize such factors as neurophysiological effects related to supraspinal descending inhibition due to associated changes in the opioid system (Sauro & Greenberg, 2005), dopamine production (Fuente-Fernandez et al., 2006), and central nervous system (Petrovic et al., 2002;Wager et al., 2004;Matre et al., 2006) which have been observed in studies unrelated to MT.

Figure 3 Pathway considering both a spinal cord and supraspinal mediated effect from Bialosky et al (2008)

RR Interval Variability Is Inversely Related to Inflammatory Markers: The CARDIA Study

Bekrefter at svak vagus gir økt betennelse. Stor studie som inkluderte over 750 deltakere.

Recent evidence reveals that the immune system is under the direct control of the vagus nerve via the “cholinergic anti-inflammatory pathway.” Stimulation of vagus nerve activity significantly inhibits cytokine levels in animal models, and cholinergic agents inhibit cytokine release by human macrophages. Moreover, when vagus nerve activity is decreased or absent, cytokines are overproduced. Atherosclerosis is an inflammatory disease characterized by elevated levels of CRP and IL-6, but the relationship between cardiac vagal activity and cytokine levels in healthy humans is not well understood. Here we measured RR interval variability, an index of cardiac vagal modulation, and CRP and IL-6 in 757 subjects participating in a subset of the year 15 data collection in the CARDIA study of the evolution of risk factors in young adults. Univariate analysis revealed that all indices of RRV were strongly and inversely related to IL-6 (log pg/mL b= −0.08 and −0.17 for HF and LF power, P < 0.001 respectively) and CRP (log mg/L b = −0.14 and −0.26 for HF and LF power, P < 0.001 respectively) levels. In the multivariate model including gender, race, age, smoking, physical activity, SBP, BMI, and disease, the inverse relationship between RRV and inflammatory markers, although slightly attenuated, remained significant. These findings are consistent with the hypothesis that diminished descending vagal anti-inflammatory signals can allow cytokine overproduction in humans.

To our knowledge, these are the first results demonstrating inverse relationships between inflammatory markers and indices of cardiac autonomic regulation in a large sample of healthy young adults. These findings are consistent with evidence from animal studies indicating that the cholinergic anti-inflammatory pathway counter-regulates inflammation.

It now appears that in our data from the CARDIA study of heart disease in young adults there is an inverse relationship between low frequency RR interval variability and the inflammatory markers IL-6 and CRP, even after control of relevant covariates and cardioactive medications or hypertension or diabetes, which is consistent with the hypothesis of a cholinergic anti-inflammatory pathway that regulates inflammation in humans.

Evolution of Air Breathing: Oxygen Homeostasis and the Transitions from Water to Land and Sky

Omfattende studie som beskriver hvordan vi har tilpasset oss høyere nivåer av oksygen. Bekrefter alle innspill jeg har hatt om oksygen sin destruktive effekt og at beskyttelsen mot oksygenets skadevirkninger er viktigere enn å få mer oksygen inn i kroppen. Lunger, sirkulasjonssystem, hemoglobin, antioksidantsystem og det at mitokondriene er godt gjemt inni en annen celle som er godt beskyttet av en tett cellevegg er forsvars- og reguleringsmekanismer mot det livsfarlige men også livsnødvendige oksygenet.

Nevner at den opprinnelige atmosfæren bestod av veldig lite O2(1-2% eller 2,4 mmHg) og mer enn dobbelt så mye CO2. Dette er miljøet mitokondriene ble utviklet i for 2,7 billioner år siden, og som de fortsatt lever i inni cellene våre. Om oksygennivået økes tilmer enn dette blir mitokondriene dårligere og mister sin funksjon.

Nevner også at forsvarsmekanismene mot oksygen var tilstede helt fra starten. Og hemoglobin (blodcelle i dyr) og klorofyll (i planter) tilfredstiller alle de nødvendige beskyttende egenskapene vi trenger mot oksygen.

Nevner at CO2 var den første antioksidanten i evolusjonen.

Beskriver også det som skjer i mitokondria, at hypoxi (lavere O2 tilgjengelighet) gir mindre ROS og økt mitochondrial uncoupling (produksjon av varme istedet for ATP). Vi kan se dette som om mitokondriene går på tomgang med lavt turtall, mens ATP produksjon er høyt turtall og dermed også mer slitasje.

Nevner også evolusjonen av diafragma som den primære pustemuskelen.

Life originated in anoxia, but many organisms came to depend upon oxygen for survival, independently evolving diverse respiratory systems for acquiring oxygen from the environment. Ambient oxygen tension (PO2) fluctuated through the ages in correlation with biodiversity and body size, enabling organisms to migrate from water to land and air and sometimes in the opposite direction. Habitat expansion compels the use of different gas exchangers, for example, skin, gills, tracheae, lungs, and their intermediate stages, that may coexist within the same species; coexistence may be temporally disjunct (e.g., larval gills vs. adult lungs) or simultaneous (e.g., skin, gills, and lungs in some salamanders). Disparate systems exhibit similar directions of adaptation: toward larger diffusion interfaces, thinner barriers, finer dynamic regulation, and reduced cost of breathing. Efficient respiratory gas exchange, coupled to downstream convective and diffusive resistances, comprise the “oxygen cascade”—step-down of PO2 that balances supply against toxicity. Here, we review the origin of oxygen homeostasis, a primal selection factor for all respiratory systems, which in turn function as gatekeepers of the cascade. Within an organism’s lifespan, the respiratory apparatus adapts in various ways to upregulate oxygen uptake in hypoxia and restrict uptake in hyperoxia. In an evolutionary context, certain species also become adapted to environmental conditions or habitual organismic demands. We, therefore, survey the comparative anatomy and physiology of respiratory systems from invertebrates to vertebrates, water to air breathers, and terrestrial to aerial inhabitants. Through the evolutionary directions and variety of gas exchangers, their shared features and individual compromises may be appreciated.


Oxygen, a vital gas and a lethal toxin, represents a trade-off with which all organisms have had a conflicted relationship. While aerobic respiration is essential for efficient metabolic energy production, a prerequisite for complex organisms, cumulative cellular oxygen stress has also made senescence and death inevitable. Harnessing the energy from oxidative phosphorylation while minimizing cellular stress and damage is an eternal struggle transcending specific organ systems or species, a conflict that shaped an assortment of gas-exchange systems.

The respiratory organ is the “gatekeeper” that determines the amount of oxygen available for distribution. Gas exchangers arose as simple air-blood diffusion interfaces that in active animals progressively gained in complexity in coordination with the cardiovascular system, leading to serial “step-downs” of oxygen tension to maintain homeostasis between uptake distribution and cellular protection.

While a comprehensive treatment of the evolutionary physiology of respiration is beyond the scope of any one article, here we focuses on the first step of the oxygen cascade—convection and diffusion in the gas-exchange organ—to provide an overview of the diversity of nature’s “solutions” to the dilemma of acquiring enough but not too much oxygen from the environment.

Ubiquity of Reactive Oxygen Species

As reviewed by Lane (407) and Maina (466), the primary atmosphere contained mainly nitrogen, carbon dioxide, and water vapor. Much of these were swept away by meteorite bombardment and replaced with a secondary atmosphere (416-418, 579, 590) consisting of hydrogen sulfide, cyanide, carbon monoxide, carbon doxide, methane, and more water vapor from volcanic eruptions. Only trace oxygen (<0.01% present atmospheric level) existed (418), originated from inorganic (photolysis and peroxy hydrolysis) (622) and organic (photosynthesis) sources.

Oxidative respiration is the reverse process as O2 accepts four electrons successively to form water. Many of these steps are catalyzed by transitional metal ions (e.g., iron, copper, and magnesium). Therefore, aerobic respiration, oxygen toxicity and radiation poisoning represent equivalent forms of oxidative stress (407).

Origin of Oxygen Sensing and Antioxidation—Metalloproteins

If oxidative stress was present from the beginning, early anaerobic organisms must have possessed effective antioxidant defenses, including mechanism(s) for controlled O2 sensing, storage, transport, and release as well as pathways for neutralizing ROS. The general class of compounds that fulfill these requirements is the metalloproteins that transfer electrons via transitional metals (766, 767), for example, heme proteins and chlorophyll (Fig. 2).

Hydrogen may have been the first electron donor and CO2 the first electron acceptor for synthesizing ATP by chemiosmosis (408).

Because of a high redox potential of O2 as the terminal electron acceptor in electron transport, aerobic respiration is far more efficient in energy production (36 moles of ATP per mole of glucose) than anaerobic respiration (~5 moles). Aerobic multicellular organisms arose approximately 1 Ga and more complex organisms such as marine molluscs thrived approximately 550 to 500 million years ago (Ma). Exposed to a still low O2 tension in the deep sea, these organisms uniformly possessed metalloprotein respiratory pigments with a characteristically high O2 affinity for efficient O2 storage and slow O2 release thereby avoiding flooding the cell with excessive ROS (783). Contemporary myoglobin continues to perform this regulatory function in muscle.

It is well recognized that embryos and undifferentiated cells grow better in a hypoxia (129, 153). A low O2 tension (1%-5%) is an important component of the embryonic and mesenchymal stem cell “niche” that maintains stem cell properties, minimizes oxidative stress, prevents chromosomal abnormalities, improves clonal survival, and perpetuates the undifferentiated characteristics (457). In addition, hypoxia stimulates endothelial cell proliferation, migration, tubulogenesis, and stress resistance (752, 850) as well as preferential growth and vascularization of many malignant tumor cells; the latter observation constitutes the basis for the use of adjuvant hyperoxia to enhance tumor killing during irradiation and chemotherapy (277,738). Collectively, these responses to O2 tension suggest that the pulmonary gas-exchange organs adapted in a direction toward controlled restriction of cellular exposure to O2.

Origin of the Oxygen Cascade

The oxygen cascade (Fig. 6) describes serial step-downs of O2 tension from ambient air through successive resistances across the pulmonary, cardiac, macrovascular and microvascular systems into the cell and mitochondria. These resistances adapt in a coordinated fashion in response to changes in ambient O2 availability or utilization (333). Traditional paradigm holds that the primary selection pressure in the evolution of O2 transport systems is the efficiency of O2 delivery to meet cellular metabolic demands. If this is the sole function of the cascade, why are there so many resistances? Once we accept the anaerobic origin of eukaryotes and their persistent preference for hypoxia, an alternative paradigm becomes plausible, namely, the entire oxygen cascade could be viewed as an elaborate gate-keeping mechanism the major function of which is to balance cellular O2 delivery against oxidative damage.

Mitochondria consume the majority of cellular O2, directly control intracellular O2 tension, and generate most of the cellular ROS (136). Intracellular O2 tension in turn regulates mitochondrial oxidative phosphorylation, ROS production, cell signaling, and gene expression. Via O2-dependent oxidative phosphorylation the mitochondria act as cellular O2 sensors in the regulation of diverse responses from local blood flow to electric activity (830). Earlier studies reported that hypoxia increases mitochondrial ROS generation (126, 782, 823) via several mechanisms: (i) O2 limitation at the terminal complex IV (cytochrome c oxidase) in the mitochondrial electron transport chain causes electrons to back up the chain with increased electron leak to form superoxide (•O2−). (ii) Hypoxia induces conformational changes in complex III (ubiquinol cytochrome c oxidoreductase) to enhance superoxide formation (88, 287). (iii) Oxidized cytochrome c scavenges superoxide (722). Hypoxia-induced O2 limitation at complex IV leads to cytochrome c reduction, limiting its ability to scavenge superoxide and enhancing mitochondrial ROS leakage. However, recent studies of isolated mitochondria show that hypoxia actually reduces mitochondrial ROS generation and causes mitochondrial uncoupling, suggesting extramitochondrial sources of ROS generation in hypoxia (330). These conflicting reports remain to be resolved. Nonetheless, moderate hypoxia rapidly and reversibly downregulates mitochondrial enzyme transcripts, in parallel with reductions in mitochondrial respiratory activity and O2 consumption (631).

As paleo-atmospheric O2 concentration increased and multicellular aerobic organisms arose, the endosymbiotic mitochondria-host relationship faced the challenge of balancing conflicting needs of aerobic energy generation for the host cell and anaerobic protection for its internal power generator. The host cell must finely control a constant supply of O2 to the mitochondria for oxidative phosphorylation while simultaneously protecting mitochondria against oxidative damage by maintaining a near-anoxic level of local O2 concentration. This trade-off may have led to the evolution of ever more elaborate physicochemical barriers that created and maintained successive O2 partial pressure gradients, by convection and diffusion in the lung, chemical binding to hemoglobin, distribution and release via cardiovascular delivery, dissociation from hemoglobin, and diffusion into peripheral cells with or without myoglobin facilitated transport. As a result, the primordial anoxic conditions of the Earth necessary for survival and optimal function of this proteobacterial remnant are preserved inside the host cell. In working human leg muscle O2 tension at the sarcoplasmic and mitochondrial boundaries has been estimated at approximately 2.4 mmHg (0.32 kPa) (835) and muscle mitochondrial O2 concentration at half-maximal metabolic rate 0.02 to 0.2 mmHg (834), that is, in the range of the ancient atmospheric level approximately 2 Ga. Raising O2 tension above these levels impairs mitochondrial activity (672). In this context, protection of mitochondria from O2 exposure likely constitutes a major selection factor in the evolution of complex aerobic life while the various forms of systemic O2 delivery systems are necessary but secondary functions that sustain the “gate-keeping” barrier apparatus to maintain adequate partial pressure gradients along the O2 transport cascade and preserve the near-anoxic intracellular conditions for the mitochondria. In parallel with physical barriers, cells also developed various biochemical scavenging and antioxidant pathways to counteract the toxic effects of ROS as ambient oxygenation increased.

Defense against the Dark Arts of Oxidation

To summarize, the evolution of life on Earth has adapted to a wide range of ambient O2 levels from 0% to 35%. Periods of relative hyperoxia promote biodiversity and gigantism but incur excess oxidative stress and mandating the upregulation of antioxidant defenses. Periods of relative hypoxia promote coordinated conservation of resources and downregulation of metabolic capacities to improve energy efficiency and channel some savings into compensatory growth of gas-exchange organs. The trajectory of early evolution is at least partly coupled to O2 content of the atmosphere and the deep ocean, and there is a plausible explanation for the coupling, namely, defense against the dark arts of oxidation. Oxygen is capable of giving and taking life. The anaerobic proteobacteria escaped the fate of annihilation by taking refuge inside another cell and in a brilliant evolutionary move coopted its own oxygen-detoxifying machinery to provide essential sustenance for the host cell in return for nourishment and physical protection from oxidation. As the threat of oxidation increased with rising environmental O2 concentration, selection pressure escalated for ever more sophisticated defense mechanisms against oxidative injury and in direct conflict with simultaneously escalating selection pressures to harness the energetic advantage of oxidative phosphorylation.

Trading off the above opposing demands shaped all known respiratory organs, from simple O2 diffusion across cell membranes to facilitated transport via O2 binding proteins to gas-exchange systems of varying complexity (skin, gills, tracheae, book lung, alveolar lung, and avian lung) (Sections 2-5). Concurrently evolving with a convective transport system, these increasingly elaborate respiratory organs not only increase O2 uptake but also maintain air-to-mitochondria O2 tension gradients and intracellular O2 fluxes at a hospitable ancestral level. This epic struggle began at the dawn of life and persisted to the present on a universal scale. The evolutionary trajectory of air breathing has continued contemporary significance to the understanding of oxygen-dependent metabolic homeostasis, especially in relation to maturation, senescence, and aging-related organ degeneration and disease.

Hypercapnia Improves Tissue Oxygenation

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.

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.
co2 og pustefrekvens
co2 og blodsirkulasjon og oksygenering
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