Acute Respiratory Distress Syndrome (ARDS) |

On January 7^th, 2020, I wrote an article about pneumonia that described a mysterious new syndrome affecting 60 people in Wuhan, China. Millions of cases and hundreds of thousands of deaths later, the virus, since named SARS-CoV2, has wreaked havoc throughout the world.

The respiratory disease caused by SARS-CoV2 is called COVID-19 and appears deadlier than the flu, with 20 percent of closed cases ending in a fatality. As of mid- late April 2020, 600,000 patients have recovered and 160,000 have died due to COVID-19. More than 1.5 million cases remain active.

Those who perished suffered from a condition known as Acute Respiratory Distress Syndrome (ARDS). In ARDS, the tiny air sacs (called “alveoli”) are inundated with fluid, forming a barrier to the absorption of oxygen. At the same time, an important substance in the lungs called “surfactant” malfunctions. Surfactant is a substance that allows adequate inflation and works like a lubricant to keep the lungs full expanded. In ARDS, failure of surfactant action “stiffens” the lungs and prevents filling with air.

CAUSES OF ARDS

ARDS can occur as a result of any severe respiratory illness or major trauma. Besides COVID-19, it can be caused by infection, the inhalation of smoke or other toxic substances, near-drowning, aspirating vomit into the airways, burns, and more.

ARDS can also be the result of a “cytokine storm”. Cytokines are molecules that aid in activating immune responses and stimulate the movement of immune cells towards sites of inflammation, infection and trauma. A cytokine storm happens when the body overproduces immune cells, causing an uncontrolled surge that increases inflammation and fluid build-up. This “hyperinflammation” raises the probability of a bad outcome.

THE DECISION TO VENTILATE IN ARDS

Respiratory distress can develop anywhere from a few hours to a few days from the start of an infection or injury. These patients will appear short of breath and have a lack of oxygen in the blood. The patient may appear blue due to “cyanosis”, an increase in de-oxygenated blood. Cyanosis occurs peripherally in the extremities (for example, fingertips) or may be seen in the core and face, especially the lips.

Low oxygen levels cause confusion, fatigue, and eventually, organ failure. They may also have difficulty maintaining a high enough blood pressure to drive circulation. In these circumstances, physicians have little choice but to help ventilate an ARDS victim mechanically.

The use of a ventilator is a big and, for the patient, frightening decision. There is no test for Acute Respiratory Distress Syndrome that says “positive” or “negative”. The physical exam, CT scans, X-rays, and oxygen levels are evaluated to determine that the patient needs respiratory support.

The goal is to improve the delivery of oxygenated blood to the organs. Giving supplemental oxygen by face mask may be tried first in some situations. If it proves ineffective, ventilation is indicated. Patients are often paralyzed with drugs while a tube is inserted into the airways. If correct tube placement is confirmed by x-ray, the ventilator is connected and gets to work forcing oxygen into wet lungs. The ventilator gives the body a break from the extreme exertion required to breathe in ARDS patients.

OTHER STRATEGIES

Sedation is needed while patients are on a ventilator, as an anxious patient may resist and pull the tube out. Anti-clotting drugs may be used to prevent blood clots. Antacids decrease gastric acid rising from the stomach. Antibiotics may be given to treat secondary bacterial infections or as a preventative against opportunistic germs.

Most hospital patients lie on their back in bed, but patients resistant to ventilator support are sometimes placed in prone position, that is, on their stomachs. ARDS patients that have trouble maintaining decent oxygen levels at high ventilator settings often improve while “proning”. Of course, this is a difficult strategy to maintain for a long period of time.

WEANING OFF THE VENTILATOR

Once a machine is breathing for the patient, the process of “weaning” off it may be long and difficult. In COVID-19, The process requires an average of two weeks of breathing support.

It’s thought that 40 percent of the time spent on a ventilator involves attempts to wean. During the weaning process, ventilator support is decreased to see if the patient can breathe spontaneously and maintain reasonable oxygen levels.

COMPLICATIONS OF VENTILATION IN ARDS

Complications may occur while on the machine. They include:

Collapsed lungs: A ventilator may use so much force to increase the oxygen content in tissues that it “pops” a lung and collapses the organ. This is known as a “pneumothorax”.

Infections: Being placed on a ventilator increases the chance that microbes can enter the respiratory tract. Some hospital-based infections are resistant to antibiotic therapy.

Blood clots: Bedridden patients on ventilators have a higher chance of developing deep vein thrombosis, a condition where blood flow in the lower extremities is decreased, leading to blood clots. Blood clots can travel from the legs to the lungs and elsewhere.

Scarring: Lung tissue can become scarred, especially in those requiring long-term ventilator support.

RECOVERY FROM ARDS

Being placed on a ventilator with COVID-19 means you have a 50-50 chance of survival. Many other conditions, however, do not require so lengthy a period and have a better chance of recovery. Various factors are involved, including age, general health, and the type of injury or infection.

Survivors of Acute Respiratory Distress Syndrome may, over time, recover completely while others experience lasting damage to their lungs. Often, there will be breathing difficulties and a temporary or permanent need for supplemental oxygen. ARDS patients may have long-term mental status issues as well, such as memory loss or confusion. Chronic fatigue, weakness, and depression are additional effects seen in ARDS patients.

Acute Respiratory Distress Syndrome is a major bump in the road for every sufferer and becomes the end of the road for many. The final result varies from patient to patient. In the years ahead, our experience with the many ARDS patients with COVID-19 may help researchers improve outcomes for this very dangerous condition.

Joe Alton MD