With the state seeing an increase in the number of Covid-19 cases, experts have been seeing multiple cases of “happy hypoxia” or “silent hypoxia” amongst 30-40 per cent of patients which is a cause of concern. The silent hypoxia is when the peripheral oxygen saturation remains good, but the partial pressure of oxygen is very low that shows up in the arterial blood gas (ABG) tests. But patients do not feel any symptoms of low oxygen, as they feel fine, healthy and keep talking.
Suddenly, their condition deteriorates, leading to their death. In a case study, a patient’s partial pressure oxygen (PO2) was 73.7 as against the normal value of 83-108, while the peripheral saturation level (SO2) was 95.5 per cent, which is normal. “In such cases, peripheral saturation remains good which is seen on a pulse oximeter, but when the ABG test is done, PO2 levels are quite low. When there is a discrepancy between PO2 and SO2, these patients come into the category of silent or happy hypoxia.
They do not feel breathlessness or gasping and are normal,” said Dr Anoop Amarnath, Head, Scientific Board, Chairman, Geriatric Medicine, Manipal Hospital, and a member of the Critical Care Support Team. “The concern is that there is no correlation between peripheral saturation level and Oxygen saturation levels in the blood. These patients do not show any symptoms.
It is a must to detect these patients early and prevent them from becoming more hypoxic, which will reduce the mortality,” he said. The potential causes are clotting in the lungs, direct viral interaction with haemoglobin and acclimatisation. Dr Amarnath said that silent hypoxia is usually seen between Day 2 and Day 10 of the onset of clinical symptoms. Patients with lung involvement, like pneumonia, that can be detected through the CT scan or X-ray, are more prone.
Also, happy hypoxia patients have elevated four inflammatory markers -- ferritin, LDH, IL6 and D- Dimer. “We have seen cases in the age group of 20-50. All the countries and also many states in the country have reported such cases. In Karnataka too, there have been instances,” he said. On managing such patients, Dr Amarnath said that all treating physicians should have an index of suspicion. “Doctors should not rely only on PO2 and must do an ABG, which reveals the patient’s status. Next is the oxygen supplementation.
Even if a patient has 93 per cent saturation, but his/her ABG shows partial pressure of oxygen, then patients need to be given oxygen supplementation. Thirdly, such patients should be advised awake proning which helps in making us of lungs that are underutilised. Lastly, if the inflammatory marker -- DDimer — is elevated then bloodthinning injections should be given,” he said.