Alveolar hypoventilation is a laboratory diagnosis. An arterial blood gas test is necessary to detect it.
Abnormal respiratory rate, depth and minute ventilation are non invasive and simple ways to see if more invasive arterial blood gas tests are needed. The physiological and biochemical status of the body will be abnormal if the motor act of ventilation is abnormal. The dose related effects of alveolar hypoventilation are most likely responsible for attacks of manic depressive insanity. This hypothesis needs testing. Psychiatrists know nothing about acid base homeostasis and the role of nerves and muscles in moving air in and out of the body and things which can go wrong with this process. This is not a lung issue; the lungs are most likely normal. This is a nerve and muscle issue affecting structures in the torso, neck, throat, peripheral ganglions and nerve fibres. Ventilation [the motor part of breathing] involves the entire body and parts can be damaged invisibly any time from birth to near death.
Breathing is an involuntary neural and motor act needed to move air in and out of the body. If the lungs are normal, then ventilation will be seamless even when inadequate. Thus, damage to “control of breathing” mechanisms will go unnoticed by others and by the person with such damage.
This is why Paula was so surprised to find that her ventilatory motor system was abnormal in health as an adult and that she was at risk of respiratory pump failure when her already limited compensatory systems where overwhelmed.
Paula had no awareness of abnormal ventilation in health or in illness BUT in illness, she most likely developed alveolar hypoventilation and some level of hypercapnia [retention of endogenous carbon dioxide]. Her mood, mental status and locomotor activity and speed were affected, as is to be expected by effects of the build up of a [endogenous] neurotoxin such as C02, a normal byproduct of aerobic cell metabolism which needs to be exhaled.
The mood change can be explained by the distress and anguish produced by the abnormal biochemical status caused by alveolar hypoventilation and hypercapnia.
The altered mental status can be explained by the effects of alveolar hypoventilation and the retention of C02. [luckily the effects are reversible if ventilation is supported and C02 exhaled.]
The psychomotor inhibition helps limit aerobic metabolism and production of C02. Less aerobic metabolism occurs if one is resting rather than active; the body arranges for this involuntarily; the person is not aware of the reason for this inhibition in their activity.
The other sickness behaviours in bipolar depression such as lack of appetite is another way of limiting cell metabolism and production of C02. Breakdown of food requires oxygen and will produce C02. Starvation [involuntary] will keep acids [H+] lower during this period of ventilatory crisis.
During the shift to mania, this tactic creates too many problems [ie muscle wasting, nutrient deficiency] and cannot be maintained. Body temperature declines too much [no food, decline of motor activity, decline of blood pressure] and other tactics are needed to keep the vital signs functioning. Unfortunately the stage of mania is very hard on the heart and heart rate begins to decline. It is unclear if changes to ventilation [which becomes irregular] in mania is helpful or harmful. Intracranial pressure due to retention of C02 may even increase and become dangerous. Mania often, at least in the beginning, causes patients to complain of pressure in their heads and this is very troubling to them.