Breathing, the skeletal muscles, internal CO2 production and the Mind

So we hope to have reinforced the importance of the respiratory muscles in t controlling internally generated carbon dioxide and how this relates to the proper function of the brain and of our ability to think and to remember. [Internal CO2 is continually produced during life , by our cells {along with water and energy [ATP] and must not build up to toxic levels.] Toxic levels can cause dose related signs and symptoms of encephalopathy.

Still editing this…….

What Is Encephalopathy?

“Encephalopathy” means damage or disease that affects the brain. It happens when there’s been a change in the way your brain works or a change in your body that affects your brain. Those changes lead to an altered mental state, leaving you confused and not acting like you usually do.

Encephalopathy is not a single disease but a group of disorders with several causes. It’s a serious health problem that, without treatment, can cause temporary or permanent brain damage.

Hypercapnia [or hypocapnia] ia a reversible cause of encephalopathy. It can be caused by unknown malfunctioning respiratory muscles becoming overwhelmed by exacerbations of illnesses causing extreme difficulty with breathing and affecting the already impaired skeletal respiratory muscle system.

So we hope to have reinforced the importance of the respiratory muscles to the control of internal carbon dioxide to the proper function of the brain and of our ability to think and to remember. [Internal CO2 is continually produced , {along with water and energy [ATP] by our cells and must not build up to toxic levels.}

What is Hypercapnic encephalopathy?“ Hypercapnic encephalopathy syndrome”(HES)is an heterogeneous and potentially reversible syndrome characterized by an altered state of consciousness associated with a wide spectrum of psycho-neurological disorders complication of an acute hypercapnic respiratory failure with respiratory acidosis. Neurological evaluation in patients undergoing non-invasive mechanical ventilation for acute hypercapnic encephalopathy:comparison of two different scores Maria Rosaria Gioia, Ambra Nicolai, Giuseppina Ciarleglio, Rosalba Maffucci, Uberto Maccari, Raffaele Scala European Respiratory Journal 2019 54: PA2319; DOI: 10.1183/13993003.congress-2019.PA2319

Hypercapnia is a buildup of carbon dioxide in your bloodstream.  You get rid of excess carbon dioxide  when you breathe out (exhale) using the respiratory muscles. Normal cell metabolism continually produces carbon dioxide in the body which must be controlled by exhaling.

So there is a direct link between the amount of endogenous carbon dioxide produced [by cell] and controlled precisely [respiratory muscles] , retaining too much [or too little ] of the carbon dioxide produced by our cells and the appearance of a reversible encephalopathy [brain dysfunction].

Paula seems to have impairments affecting her respiratory muscles, of which she is unaware of . These issues are visible, but only with mindful physical observation of her breathing [watching her breathing while she is lying down is the best way to notice this] and with measurements of her respiratory rate [again lying down awake in a relaxed position].. Only then does her depressed rate of breathing and her use of accessory muscles to exhale and to help inhale become visible.

Because of her active exhaling and deep inhaling with every breath, spirometry does not measure her tidal volume at all. But the doctor will assume quiet breathing and average respiratory rate on her part, which will be wrong.. If neither the doctor or the patient knows that her quiet breathing is absent, and they will not know that they are only getting measurements of forced effortful breathing at rest as well as during the actual forced breathing part of the test.

Spirometry records tidal volume while the patient breathes quietly” StatPearls Physiology, Tidal Volume Sasha Hallett; Fadi Toro; John V. Ashurst. accessed January 16 2022 …

Paula does not have normal quiet breathing so spirometry will give the doctor faulty information.

Tidal Volume is the amount of air inhaled or exhaled normally at rest [using passive exhaling] Click on the underlined words Tidal volume  in this sentence. The small waves depicted on the graph are tidal volume and the big wave is Vital Capacity. You can see that in a normal person, breathing at rest, there is a difference between tidal volume and vital capacity. This is what the doctor assumes to be true in every patient.

Paula can only breathe at her Vital Capacity at rest. [I am not a doctor and I may not be using the completely correct terms but the essence of what I am describing IS correct!

In a person like Paula the doctor will only get a bigger wave and they will not realize it involves abnormal effortful breathing and thus the interpretation of the test will be right and wrong at the same time. The test will show that her lungs are fine. The test won’t detect the increased work of breathing required to get a normal [or somewhat above normal] result. The wave, if interpreted as a tidal volume will be big enough, but as a vital capacity it is not be big enough. Paula does not have a lot of reserve if she should get sick. The test will ignore that her respiratory muscles are not fine [hence the need for forced exhaling] and will ignore her depressed respiratory rate. .[spirometry does not record respiratory rate].


Apparently, Paula’s pattern  is suggestive of hypercapnia.

Hypercapnia induces a breathing pattern characterized by a relatively larger increase in tidal volume than the respiratory rate to minimize dead space ventilation. In other terms, Hypercapnic patients compensate by taking slow, deep breaths to optimize CO2 elimination. The only way to minimize dead space ventilation is to increase the volume of air that reaches the respiratory zone, which can only be done by increasing tidal volume. StatPearls Physiology, Tidal Volume Sasha Hallett; Fadi Toro; John V. Ashurst. accessed January 16 2022

Chronic hypercapnia does not necessarily cause brain or mind dysfunction or any other visible signs, except for deep slow breathing, because the body adapts to this condition.

Tidal Volume/ Organ Systems Involved

The lungs are responsible for delivering a tidal volume capable of maintaining adequate ventilation. However, producing precise tidal volumes relies on complex coordination between the respiratory center in the brain and the muscles of respiration. The respiratory pacemaker in the brainstem determines the rate and depth at which breathing occurs. In response to changes in blood oxygen and carbon dioxide levels, central and peripheral chemoreceptors send information to the brainstem to modulate the pacemaker’s firing rate and pattern. The diaphragm, and other inspiratory muscles, respond by altering tidal volume and respiratory rate. The aim is to maintain adequate levels of oxygen and carbon dioxide in the blood. StatPearls Physiology, Tidal Volume Sasha Hallett; Fadi Toro; John V. Ashurst. accessed January 16 2022

In Paula’s case, the complex coordination between the respiratory centre and the muscles of respiration and her well functioning lungs, are able to maintain adequate levels of oxygen and carbon dioxide BUT only with baseline active exhaling [and inhaling] at a depressed respiratory rate at rest.

This suggests that Paula is susceptible to respiratory acidosis and more hypercapnia due to further mechanical stress to her already hard working respiratory muscles. So she might show the effects from injury or from acute or chronic illness [like infection or upper respiratory obstruction] and/or from exposure high levels of outdoor/indoor CO2, CO and particulates from using fossil fuels or wood ovens for cooking and heating, more quickly because she is already struggling to exchange the right proportion of air.

Effortful ventilation will increase the work of breathing and result most likely in higher production of internal carbon dioxide from cell metabolism .Further increases in internal carbon dioxide during locomotor activity or exercise might exacerbate the situation further because….During exercise, for example, oxygen consumption increases, and carbon dioxide accumulates. As a result, respiratory rate and tidal volume rise to meet the increasing demand.”StatPearls Physiology, Tidal Volume Sasha Hallett; Fadi Toro; John V. Ashurst. accessed January 16 2022

During exacerbations of hypercapnia due to acuter continuing illness [due to Paula’s difficulty increasing her vital capacity further], her body may decide to limit locomotor activity and speed in order to keep internal carbon dioxide from rising too much, too fast. Reducing her activity during even more increased work of breathing [from illness, fatigue etc..] may be her body’s most reasonable option, given her difficulties.

To be continued….

Exacerbations of hypercapnia or development of new hypercapnia affects H+ balance in the brain and in the spinal cord. Neurons are extremely sensitive to alterations of H+ and can cause alterations to baseline mental status, resulting in quiet behaviour, diminished speech and depressed mentation.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s