Study explains fluctuation in blood oxygenation levels in COVID-19 patients ANI | Updated: Jan 02, 2021 12:13 IST Washington [US], January 2 (ANI): A study published in the journal sheds light on the explanation for the lack of blood oxygenation detected in many COVID-19 patients. The mysterious physiopathological characteristics of COVID-19 that has most baffled the scientific and medical community is what is known as 'silent hypoxemia' or 'happy hypoxia'. Patients suffering this phenomenon, the causes of which are still unknown, have severe pneumonia with markedly decreased arterial blood oxygen levels (known as hypoxemia). However, they do not report dyspnea (subjective feeling of shortness of breath) or increased breathing rates, which are usually characteristic symptoms of people with hypoxemia from pneumonia or any other cause.