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Co2

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.
Is it true that the urge to breathe is triggered only by high CO2 levels?

Yes, mostly so. There might be trace effects from other stuff, but CO2 is the major trigger AFAIK.

(CO2 as dilute carbonic acid (Carbon dioxide dissolved in aqueous solution), the same stuff makes caves in limestone rock).
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Wikipedia:
Carbon dioxide dissolved in water is in equilibrium with carbonic acid... Carbonic acid has the formula H2CO3. It is also a name sometimes given to solutions of carbon dioxide in water, which contain small amounts of H2CO3. The salts of carbonic acids are called bicarbonates and carbonates. It is a weak acid. the majority of the carbon dioxide is not converted into carbonic acid and stays as CO2 molecules. CO2 + H2O ⇌ H2CO3

Role of carbonic acid in blood

Carbonic acid is an intermediate step in the transport of CO2 out of the body via respiratory gas exchange. The hydration reaction of CO2 is generally very slow in the absence of a catalyst, but red blood cells contain carbonic anhydrase which both increases the reaction rate and disassociates a hydrogen ion (H+) from the resulting carbonic acid, leaving bicarbonate (HCO3-) dissolved in the blood plasma. This catalysed reaction is reversed in the lungs, where it converts the bicarbonate back into CO2 and allows it to be expelled.

Carbonic acid also plays a very important role as a buffer in mammalian blood. The equilibrium between carbon dioxide and carbonic acid is very important for controlling the acidity of body fluids, and the carbonic anhydrase increases the reaction rate by a factor of nearly a billion to keep the fluids at a stable pH.

[ame=http://en.wikipedia.org/wiki/Carbonic_acid]Carbonic acid - Wikipedia, the free encyclopedia[/ame]
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Air hunger

Air hunger is the sensation of the urge to breathe. It is usually caused by the detection of high levels of carbon dioxide in the blood by sensors in the carotid sinus and is one of the body's homeostatic mechanisms to ensure proper oxygenation. Natural chemicals in the blood such as epinephrine (adrenaline) can also induce an urge to breathe by a separate pathway. Insufficient pulmonary minute ventilation, a sustained breath-hold, constriction of the alveoli of the lungs as in asthma, or high ambient levels of carbon dioxide in the air breathed can cause air hunger resulting in a respiratory distress condition characterized by dyspnea, labored breathing or gasping. Air hunger can be extremely distressing and triggers panic and strong reactions to restore breathing.

In mammals the breathing reflex is triggered by excess of carbon dioxide rather than lack of oxygen. In particular, this means that air hunger is not always experienced during asphyxiation. In oxygen-deprived environments, respiration continues to cycle out carbon dioxide but does not bring in sufficient oxygen. Without the required carbon dioxide accumulation, victims may not realize they are being asphyxiated until other symptoms appear, or at all.
[ame]http://en.wikipedia.org/wiki/Air_hunger[/ame]
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Parts of the brain which react to high CO2 (hypercapnea):
http://www.uthscsa.edu/opa/issues/new34-9/PET.html

They induced breathlessness in healthy volunteers by adding a small amount of carbon dioxide (CO2) to the subjects' inspired air. The resulting PET images revealed consistent blood flow changes (a measure of brain activity) in the amygdala, anterior cingulate cortex, cerebellum and other brain areas. These changes then were correlated with measures of the participants' physiological and subjective responses to better characterize the brain circuitry involved in unconscious and conscious detection of air hunger.

The amygdala, a brain structure that is present in all animals and regulates the subconscious ability to perceive threat, was strongly activated by CO2 inhalation. However, when subjects felt breathless, blood flow to the anterior cingulate cortex increased dramatically. "We believe this reflects a key role for the anterior cingulate in mediating conscious awareness of breathlessness," stated Dr. Liotti.

"Our physiological drives run on autopilot to a certain point," continued Dr. Brannan. "We breathe without thinking; we eat when it seems time; we drink when we feel thirsty. What we have identified here is part of an adaptive brain circuit involved in automatic respiratory control and conscious perception of air hunger. The amygdala continuously senses our internal states and detects potential threats to our survival. The anterior cingulate sounds the alarm when there is conscious perception of immediate danger."
 
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The technical side seems very straight forward, but there has to be a mental side to it too. I wonder how much the persons own mind gets involved. I personally use distraction techiniques of singing in my head to pass the time and convince myself that the whole thing isn't as bad as it is feeling
 
wet:

Quite a comprehensive answer there..
I didn't know all of that.
 
Actually the technical side is much more complex, as far as the 'electrical & plumbing' system of gas exchange, nerves, arteries, baro/chemo-receptors.

How that all ties in with the emotions, I don't know, they are extensions of sensitivity to both internal and external environments. Distraction can override discomfort, music is a good one.
 
The Edinger-Westphal nucleus supplies parasympathetic fibres to the eye via the ciliary ganglion, and thus controls the sphincter pupillae muscle (affecting pupil constriction) and the ciliary muscle (affecting accommodation). It is the most rostral of the parasympathetic nuclei in the brain stem.

[It has also been implicated in the mirroring of pupil size in sad facial expressions. When seeing a sad face, participants' pupils dilated or constricted to mirror the face they saw, which predicted both how sad they perceived the face to be, as well as activity within this region]

Edinger-Westphal nucleus - Wikipedia, the free encyclopedia

(I'm trying to figure out how the eye nerves, CO2 sensors & diving fit.)
 
Simple experiments with an oximeter and CO2 monitor will show you that although CO2 is usually responsible for the urge to breathe, low O2 does create a large urge to breathe, especially if one is holding the breath.

For example, when I am sitting here, if I check my exhaled CO2 it is about 5.0%. No urge to breathe. Regular O2 levels.

If I hyperventilate for 2 minutes my CO2 will go down to about 3.0%. I then do a full exhale static.

After 2 minutes in the exhale static the O2 in my lungs has dropped to around 6% (down from 18%). I feel a huge urge to breathe. I exhale the little air in my lungs and find my exhaled CO2 level to be just 4.2%. Less than while sitting at the computer.

In this case, I felt a strong urge to breathe, and CO2 levels were well below anything that would normally trigger an urge to breathe.
 
I really appreciate everyone's input here. Research material is still thin on the ground and real life experience is priceless.

Thanks to you all
 
Simple experiments with an oximeter and CO2 monitor will show you that although CO2 is usually responsible for the urge to breathe, low O2 does create a large urge to breathe, especially if one is holding the breath.

For example, when I am sitting here, if I check my exhaled CO2 it is about 5.0%. No urge to breathe. Regular O2 levels.

If I hyperventilate for 2 minutes my CO2 will go down to about 3.0%. I then do a full exhale static.

After 2 minutes in the exhale static the O2 in my lungs has dropped to around 6% (down from 18%). I feel a huge urge to breathe. I exhale the little air in my lungs and find my exhaled CO2 level to be just 4.2%. Less than while sitting at the computer.

In this case, I felt a strong urge to breathe, and CO2 levels were well below anything that would normally trigger an urge to breathe.

How did you measure your O2 levels, I would like to try this experiment? I have an oxy medair gadget, will that do or do I need something to breathe into like the Co2 moniter?
 
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Simple experiments with an oximeter and CO2 monitor will show you that although CO2 is usually responsible for the urge to breathe, low O2 does create a large urge to breathe, especially if one is holding the breath.

For example, when I am sitting here, if I check my exhaled CO2 it is about 5.0%. No urge to breathe. Regular O2 levels.

If I hyperventilate for 2 minutes my CO2 will go down to about 3.0%. I then do a full exhale static.

After 2 minutes in the exhale static the O2 in my lungs has dropped to around 6% (down from 18%). I feel a huge urge to breathe. I exhale the little air in my lungs and find my exhaled CO2 level to be just 4.2%. Less than while sitting at the computer.

In this case, I felt a strong urge to breathe, and CO2 levels were well below anything that would normally trigger an urge to breathe.


Just came across a link (pasted below) to research from 2015 where researchers discovered the mechanism where blood Oxygen sensors regulate urge to breathe.
https://www.sciencedaily.com/releases/2015/04/150421142949.htm
Scott
 
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