Hypercapnia causes abnormally elevated arousal and distress. [mental anguish].
This is due to the internal reflex sympathetic activation causing very high blood pressure and heart rate [and cardiac arrhythmia’s] and vasoconstriction.
Dr Emile Kraepelin found these vital signs and more, in his bipolar depressed patients. These patients had no words to describe the immense distress they experienced. Sympathetic activation usually includes higher than normal breathing rates. Kraepelin did not find higher than normal breathing rates, he did not even find normal breathing rates [12-15 breathes per minute], he found very slow breathing rates.
It seems clear to Paula and I that the reason for the reflex sympathetic activation was that breathing rates remained too slow when the patient became physically ill. And the too slow breathing led to mental anguish from unseen dyspnea when breathing became more shallow. This led to reduced motor activity, reduced body temperature, and reduced function of mind [a state of mental confusion]. These are all consistent with the signs of retention of carbon dioxide in the blood.
This hypothesis is further strengthened by the Merck’s Manual’s explanation of Respiratory Acidosis meant for doctors:
“Respiratory acidosis is carbon dioxide (CO2) accumulation (hypercapnia) due to a decrease in respiratory rate and/or respiratory volume (hypoventilation).
Causes of hypoventilation (discussed under Ventilatory Failure) include
• Conditions that impair central nervous system (CNS) respiratory drive
• Conditions that impair neuromuscular transmission and other conditions that cause muscular weakness
• Obstructive, restrictive, and parenchymal pulmonary disorders“
It is not very complicated.
The complicated part is understanding why a person’s baseline breathing remain too slow in a situation of respiratory challenge. We do not understand “Conditions that impair central nervous system (CNS) respiratory drive ” very well. We understand even less when the patient has normal lungs like Paula. It seems clear to Paula and I that Paula has a condition or injury that impairs her CNS respiratory drive in health. This leaves her vulnerable in illness. In Paula’s case, it is probable that this injury stems from her anoxic birth from getting stuck in her mother’s birth canal [made crooked by her Mom’s history of Rickets] and then being successfully resuscitated. Or, something might have happened to her during her sleep that fateful night when she suddenly woke up with unbearable dyspnea that lasted over a year until the serotonin booster was able to rescue her tidal volume, if not her slow respiratory rate.
No one suspects invisible and unlooked for “Conditions that impair central nervous system (CNS) respiratory drive ” impairing mind. [during increased respiratory loads ]..in depressive bipolar depressive attacks today.
Thus no one is is researching “Conditions that impair central nervous system (CNS) respiratory drive by causing baseline slow breathing at rest, even during major respiratory challenges, today in depressive bipolar depressive attacks today..
The clues are in monitoring the respiratory rate at rest. There are sensors today that do this. We used one of those sensors , Montreal’s Hexoskin Shirt, to track her baseline respiratory rate for 5 hours [during which she read an exciting thriller]. Her breathing was very stable, she moved lots of air in and out, per minute, but slowly: at the rate of 5 breathes per minute with active exhaling instead of normal effortless passive exhaling.
Paula wishes to remind everyone that the effects of internal injuries causing hypercapnia are reversible, but will require supportive medical help to resolve in a timely way ,[ie. before it destroys your life]
” Patients with hypercapnia can present with tachycardia, [and bradypnea;too slow breathing] , dyspnea, flushed skin, confusion, headaches, and dizziness. If the hypercapnia develops gradually over time, symptoms may be mild or may not be present at all. Other cases of hypercapnia may be more severe and lead to respiratory failure. Diagnosis is made with arterial blood gas.
Hypercapnia should be managed by addressing its underlying cause. A noninvasive positive pressure ventilator may provide support to patients who are having trouble breathing normally. [ie Paula]. If a noninvasive ventilator is not efficient, intubation may be indicated. Bronchodilators may also be used in patients suffering from an obstructive airway disease. [ i.e. the airway should be checked for secretions, etc.. that might be obstruction the airway]. StatPearls [Internet]. 2020 Physiology, Carbon Dioxide Retention S. Patel, JH Miao, SH Majmundar https://www.ncbi.nlm.nih.gov/books/NBK482456/

Research may uncover even better drugs or supportive devices in the future. These could help bipolar patients with hidden respiratory acidosis and normal lungs. But only if we look for retention of carbon dioxide as a possible cause for their depressive insanity.
Doctors often ignore vital signs, especially respiratory rates [and tidal volumes] and forget that retention of carbon dioxide is an invisible cause of undiscovered neuropsychiatric [potentially reversible ] mental confusional states.
Dr Kraepelin understood this over one hundred years ago during the Golden Age of Science.
He understood the significance of finding abnormal breathing rates in depressed and insane patients. He understood that abnormal breathing rates needed investigation because respiratory problems could lead to acid base problems causing mental confusion.
The importance of what Kraepelin documented in his many studies has long been forgotten. Paula and I are hoping to correct this.
The hypothesis is not difficult to test. Research will show if this hypothesis has merit or it doesn’t.