The new coronavirus continues to wreak havoc around the globe. The virus causes problems will almost every organ, but its key target are the lungs.
In Mexico City, academic neurologist and expert in infectious diseases, Dr. Alejandra Gonzalez Duarte was drafted in to help care for patients arriving at her local hospital. She was left particularly puzzled by one peculiar observation. It was not about what she did see, it was about what she didn’t see.
The patients arriving with severe COVID pneumonia, had very low oxygen levels, but no sensation of shortness of breath. The same had also been reported in the Wuhan COVID cohort, coining the phrase “happy hypoxia.”
Why were the COVID patients with dangerously low oxygen levels not feeling it? Dr. Gonzalez Duarte and Dr. Norcliffe-Kaufmann explored this question further in their recent letter published in Clinical Autonomic Research.
Normally, when blood oxygen levels drop, nerves arising from the neck and the lung send warning signals to the brain. This allows the brain to speed up and deepen breathing. These nerve signals are also transmitted upwards, to the brain’s cortex, which creates the sensation of air hunger and a conscious need to breathe. This hardwired brainstem reflex is essential for our survival in many scenarios.
The patients were breathing more quickly with faster heart rates – so that part was working. It was the lack of awareness that was astonishing. But, having both trained together at the Dysautonomia Center, they’d seen this before. What the COVID patients appeared to have was a problem with interoception. The term refers to process whereby the brain listens to the body allowing us to have conscious and unconscious awareness of internal bodily signals, like air hunger.
What immediately struck the two scientists, was the simularites between the COVID pneumonia patients and the patients they follow with familial dysautonomia, who have a neuropathy that disrupts interoception. These children are born without the nerves that connect the body to the brain so they have little sense of their inner world. They too are happy hypoxics. When a patient with familial dysautonomia is rushed in with a severe lung infection, we often find them in the emergency room hypoxic, but not complaining. These patients can also die suddenly at night. Most likely because they have long pauses in breathing while asleep with no arousal response to wake them up.
We still don’t know why COVID pneumonia produces no sensation of shortness of breath, but this points towards a problem of blunted interoception. Regardless of the cause, with front line experience in the pandemic, Dr. Gonzalez Duarte emphasized the importance of following the oxygen levels, rather than the patient’s complaints when treating COVID infected patients. Even in hospital facilities, patients can have sudden death when taking voluntary breaks from supplementary oxygen.
Congratulations to Dr. Gonzalez Duarte and Dr. Norcliffe-Kaufmann on their publication, which is the most highly downloaded article of 2020 in Clinical Autonomic Research.
Link to the article: https://pubmed.ncbi.nlm.nih.gov/32671502/
For the full text click here