There are many types of system failures when something as complex as the autonomic nervous system is concerned. Maintaining an adequate “internal milieu” or homeostasis is vital to being alive and is vital to the function of the brain and to the function of memory and the mind.
Loss of baseline adult memory and of one’s baseline adult ability to think is what occurs in mental illness such as schizophrenia and bipolar illness. Researchers still do not know what causes these severe illness.
In the case of bipolar attacks, Dr Emile Kraepelin  found clues that suggest hidden failure to ventilate adequately enough to maintain acid base balance of the blood. The patients were unaware of their abnormal ventilation. Doctors also were unaware, unless they took the time and effort to measure the baseline at rest respiratory rate per minute. Dr Kraepelin suggested that following these clues and learning about insufficient ventilation and build up of acid [in particular carbon dioxide] result in the pattern of clinical signs and symptoms of bipolar illness or manic depressive insanity, as he called it in 1926.
Spirometry did not exist in Kraepelin’s time. Kraepelin could not measure tidal volume or vital capacity. He understood, however, that abnormal ventilation rates per minute, could lead to an acidosis, a respiratory acidosis, particularly with an exacerbation of respiratory challenges such as chronically poor breathing conditions, respiratory infection, any infection leading to deteriorating body condition [such as inappetence, weight loss, blood loss, muscle weakness, etc…].
Part of breathing involves the motor respiratory muscle pump and part involves the lungs. Today we evaluate the lungs but ignore the state of the ventilatory pump, yet both are crucial to acid base control.
It seems to me [and it seemed to Dr Kraepelin back in 1926] that the adequacy of the ventilatory pump and the adequacy of physiological reflexes responding to increase of respiratory acids needed to be assessed, especially in patients who suddenly showed signs of altered mental status.
1]. The altered mental status is one major clue. 2]. The abnormal pattern and rate of breathing is another major clue. In order to become aware of these clues, both will require non invasive testing. If cognitive/memory screening tests are abnormal AND if breathing rate and pattern are abnormal [depressed or excited] this will suggest the need to measure PC02 and pH of the blood with an arterial blood gas test. The arterial blood gas test is the only way to identify abnormal PC02 in the blood. Analyzing serial arterial blood gases in ambulatory awake upright patients is not without risk, [which is why doctors never do it], BUT such analysis of PCO2 might lead to successful treatments that will rescue baseline mental status during hidden respiratory challenges worsening already abnormal ventilation. The risk of being incapacitated and disabled by altered and diminished mental status for most of one’s life is far worse than an invasive arterial blood gas test, doctors just ask your patient. Just ask their family. Just ask their friends. Just ask their employers. Just ask their loved ones. Just ask anyone at all if the risk is worth possibly finding out more information about any condition involving altered mental status and how to rescue baseline mental function.
I am not a doctor or a scientist but I am disappointed that no one seems to have looked at the effects of an unlooked for injury on the complex ventilatory pump [apart from the lungs-which might be fine].
The ventilatory pump is unprotected and easily injured and, without looking at patterns and rate of breathing, injuryis easily overlooked. The ventilatory pump is key to the control of respiratory acids, which-as you know- is key to the function of the brain and key to intracranial pressure.
The function of the brain, the function of the ventilatory system and normal or impaired reflex response to retention of carbon dioxide is surely important to study in any patient who becomes acutely confused, depressed or cognitively impaired; a good example is the post-stroke recovery of mental function. It is easy to study ventilation during sleep and also during daytime baseline respiratory rate and pattern in ambulatory, awake, upright patients. [It is non-invasive too]. Abnormal minute ventilation [RR times Tidal Volume] will suggest the need for ABG studies.
Dr Emile Kraepelin  noted that spontaneous recovery of cognitive function also occurred in manic depressive insanity in then, unmedicated patients.
Kraepelin also measured vital signs of respiratory rate, blood pressure, heart rate and body temperature during both depressive and manic insanity [insanity referring to changes in the cognitive functions] phases in the same patients. Kraepelin found abnormal baseline respirations in depressive insanity and in manic attacks in the same patient [different patterns]. Interestingly, he found depressed respiration in the depressive phase and excited respiration in the manic phase. E .Kraepelin Manic Depressive Insanity 1926. Ch. 3 Bodily Signs
All this to say that Kraepelin knew his physiology and hypothesized respiratory acid base dysfunction causing disturbed brain function due to the findings of abnormal baseline respiration.
After all, “ respiration and cerebral blood flow regulatory systems may interact with each other because both systems are regulated by the same mediator …C02.” “Interaction between the respiratory system and cerebral blood flow regulation” Shigehiko Ogoh. 2019 https://doi.org/10.1152/japplphysiol.00057.2019
Signs of abnormal exchange of air along with symptoms of cognitive impairment [after stroke], depression and/or mental confusion might suggest the need for serial arterial blood gas tests to check for possible and reversible hypercapnia and respiratory acidosis.
Certainly it seems to me [and it seemed to Kraepelin] that the presence of cognitive impairment and abnormal minute ventilation in an ambulatory awake upright person with sudden altered mental status, might suggest an respiratory acid base imbalance which today we may be able to treat, thus possibly rescuing mental status faster, even if we cannot correct the injury to the ventilatory pump system.
Kraepelin’s hypothesis needs to be looked at, I think, both for stroke patients and for bipolar patients, since injury to the ventilatory pump system would affect the brain, even if the lungs were healthy.
Most doctors do not bother thinking about the possible subtle permanent damage to the ventilatory system, even in patients with altered mental and cognitive status when the patients are ambulatory, upright and awake. And they certainly ignore baseline respiratory rate and patterns and do not often obtain arterial blood gas measurements.], evrn in delirious patients, never mind post stroke or mentally confused neuropsychiatric patients.
One would think that doctors understood that “ both systems are regulated by the same mediator …C02.”
Interaction between the respiratory system and cerebral blood flow regulation Shigehiko Ogoh. 2019 https://doi.org/10.1152/japplphysiol.00057.2019
Just a reminder that my friend Paula has an unknown and unconscious injury to the ventilatory pump system. [we think from her difficult birth].
No one is investigating whether or not she has chronic hypercapnia [which will often result in no symptoms] due to her depressed baseline breathing.[which even she is unaware of unless respirations are carefully and mindfully counted.]. [She does not have sleep apnea].
Paula seems perfectly normal except that she most likely is more prone to different percentages of respiratory dysfunction and respiratory pump failure during respiratory challenges and during recovery from respiratory challenges. This results in periods of depressed motor and mental activity which can become chronic and then spontaneously lift, for reasons we cannot understand without looking more carefully at her respiratory blood gases.
Arterial blood gases in upright ambulatory awake patients with altered mental status are generally not done by doctors, even when patients show up with acute changes to their mental status. so we know nothing of if or how this links to her reversible attacks of cognitive impairment, which nonetheless may be debilitating while they last. It is an interesting hypothesis though.
We also found out that she was born not breathing and needed resuscitation and transfusion [in 1955]. Her mother had crooked lower body bones from infantile Rickets [most likely due to poverty]. So it is possible that she suffered early hidden injury to the unprotected and complex peripheral ventilatory pump.
Looking for stable but abnormal breathing rates and patterns in post stroke patients and in confused or depressed patients might help identify the need to address issues of hidden chronic hypercapnia impeding recovery of baseline mental status [and maybe even motor status].
to be continued………..