How Do You Know When a Major Depression is a Subtle, Quiet Subtype of Delirium?

You don’t. They will look the same. And the patient will nor be able to tell the difference either. Appearances can be deceiving; UNLESS you measure the respiratory rate and the other vital signs. Paula looked depressed. She was clearly not her normal self. Had anyone measured her resting vital signs; they would have seen that her breathing rate was seriously depressed, at 3 breaths per minute. She had mild hypothermia, lethargy, changes to her voice, difficulty speaking and she no longer remembered her address. She did not take opioids or other drugs and did not practice Yoga. Her hands were too cold for pulse oximetry. If I had been the doctor, I would have ordered an arterial blood gas test to check O2 and PCO2 levels. Hypercapnia is caused by hypoventilation and most likely she had both hypoventilation and hypercapnia. This explained her high blood pressure and heart rate and abnormal heart sounds.

Voila! Diagnosis made! Supportive medical care is needed to bring back her baseline mental status and clear her delirium as quickly as possible.

But this is not what the doctor did.

He/She did not know to measure vital signs. He/She never figured out that Paula did not have a psychiatric syndrome. The doctor was misled by a faulty belief system, one which taught him/her to only judge by external appearances and behaviour. Paula herself knew the doctor was making a mistake but was helpless to prevent it. Paula had hypercapnic respiratory failure , probably from congestion of the upper airway [nose and throat] and could not breathe. This is why she felt so bad. Sometimes feelings are not emotions, they are sensations of physical illness and signs of failure of homeostasis.

Kraepelin made the correct diagnosis also, in thousands of his patients who felt equally bad. He measured their respiratory rates and the rest of their vital signs. Kraepelin discovered a respiratory defect; these patients could not raise their breathing rates in response to physical illness, as is normal. Kraepelin understood that patients like Paula needed the supportive and pharmacological care that the 21st century would eventually bring.

Thanks Dr Kraepelin.