Coronavirus: What happens inside the lungs of a patient?

Dubai: With COVID-19 affecting over two million people and resulting in more than 133,000 deaths within four months worldwide, there is much talk about how the virus preys on those with a weak immune system and overwhelms it.

Hospitals around the world have reported what they call is a Cytokine Storm (CS) within a COVID-19 patient, where the body is overrun by excessive immune cells meant actually for protection. The National Cancer Institute, US, defines a CS as a severe immune reaction in which the body releases too many cytokines or proteins in our immune system into the blood too quickly.

Dubai-based Dr Dirar Abdallah, specialist in internal medicine and head of the Intensive Care Unit (ICU) at the COVID-19 ward at Prime Hospital, explained what this means.

When cytokines turn rogue

“Cytokines are proteins in our immune system that are programmed to destroy any alien invasion. However, in many cases when the immune system is overwhelmed, it produces more of these protein bodies than required and these turn rogue, turn invaders and attack the healthy cells of the body. This happens in autoimmune diseases such as lupus or Rheumatoid Arthritis. In COVID-19 positive cases, it happens very easily.”

Dr Abdallah said the patient might hardly have any symptoms -- just light fever and dry cough -- but the chest X-ray will show severe fibrosis. “We have indications of a CS with typical markers of this in blood tests such as a high level of C-reactive protein, ferritin etc. The patient rapidly deteriorates, gets a seizure, goes into coma, organ failure and even death without timely intervention,” he said.

All patients, with severe COVID-19 experience CS which is marked by fluid filling in the lungs. The cells attack the lungs and leave scar tissue which results in fibrosis and inflammation. This results in blood vessels leaking and clotting, depriving major organs of blood and oxygen which in turn leads to a drop in blood pressure. If this condition is left unchecked, the patient rapidly deteriorates and can succumb to the disease.

Immune system goes on the rampage

What happens when the virus enters the respiratory tract? Our bodies are not programmed to deal with the novel coronavirus. According to Dr Sandip Pargi, consultant pulmonologist at Aster Mankhool Hospital, who has handled COVID-19 positive cases: “Our bodies have a specific defense system and react in a specific manner to each alien that enters, be it viruses, bacteria or fungi and release cytokines or proteins in our immune system that move between the cells and destroy the alien.”

However, he said, in the case of COVID-19, the virus is an unknown enemy and our bodies are not programmed to deal with it. “Therefore, the immune system overreacts producing more cytokines than required. The immune system literally goes on the rampage, invading healthy tissues of the lungs. This leads to inflammation, fluid retention, inability of the blood vessels to carry oxygen, bleeding and clotting in the capillaries and veins that deprives major organs of blood and oxygen, resulting in a drop in blood pressure and organ failure and possible death.”

How is CS treated? A case study

Citing the instance of a recently recovered patient who was put on a mechanical ventilator, Dr Aballah said: “This patient was a typical example of someone who got the infection through community transmission. He had no travel history or any knowledge of coming close to a positive patient. In his early sixties with diabetes and hypertension, he developed symptoms and tested COVID-19 positive, so the odds were against him.”

He said sometimes, CS can be insidious and moves very quickly, damaging the lungs of the patient. “We have to act very quickly and judge if the patient needs to be put on a ventilator. Externally, this patient had mild to moderate symptoms - just a slight fever and dry cough with some breathing difficulties. But he was a classic case of a CS as his X rays and CT scans showed his lungs were badly affected. The alveoli in the lungs where the transfer of oxygen and carbon dioxide occurs were run over by the virus. His blood tests had all the markers of a storm. His condition began to deteriorate rapidly as his lungs got fibrosis, he suffered from Acute Respiratory Distress Syndrome (ARDS) and his oxygen saturation, which is normally 94, had dropped.”

In such cases, when the patient is put on the mechanical ventilator, it pushes air into the lungs under pressure while the patient is heavily sedated. “We gave him an injection to curb the production of cytokines. All this while other anti-virals, hydroxycholoroquine and antibiotics were being given to him via an oral tube going into his stomach,” said the specialist.

It took about four days for the storm to subside and the patient was weaned off the ventilator but continued to be on oxygen via the canula. He was advised to sleep in a sitting position to allow the phlegm and fluid in the lungs to come out. The treatment was continued until the patient recovered after nearly 10 days of being in the Intensive Care Unit.