Clinical signs associated with hypoventilation may be the result of the systemic effects of hypercapnia, uncompensated respiratory acidosis, or secondary to the disease process causing the hypoventilation. Patients with a decreased minute ventilation may present with shallow, rapid breathing or deep, slow breathing. Dyspnea may or may not be present, depending upon the condition causing hypoventilation. For example, patients with impaired central respiratory drive often do not appear to have difficulty breathing. Meredith L. Daly VMD, DACVECC, in Small Animal Critical Care Medicine (Second Edition), 2015
This is the case with Paula. She does not appear to have difficulty breathing, but she has decreased minute ventilation with deep, slow breathing. She is normal, and in good health most of the time, despite her impaired central respiratory drive. Unfortunately, she cannot cannot increase VE appropriately if illness affecting breathing, under difficult breathing conditions occur. Surprisingly, this has not happened often. [ VE means Minute ventilation, which is the tidal volume times the respiratory rate,]
Since hypercapnia is known to affect the brain and mental status, it seems obvious [in the 21st century at least] to check out breathing rate if a person is “not themselves” and this includes depressive looking states or manic states.
Kraepelin noted slow breathing in thousands of depressive bipolar patients and fast breathing in the same patients with mania. In other words, Kraepelin noted decreased minute ventilation or hypercapnia [a form of respiratory failure] in manic depressive insanity. It is very possible that these patients had undiagnosed acquired or congenital impaired central respiratory drive .
Today there are many ways to help such patients and restore their minds, but it requires supportive medical treatments and research.
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Of Sound Mind 