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Coronavirus: How do ventilators work?

March 31, 2020

Critically ill COVID-19 patients need artificial respiration. But there is a worldwide lack of equipment.

A nurse providing respiratory support to a patient in a hospital.
Image: picture-alliance/dpa/M. Becker

In 20% of those infected in the current pandemic, the SARS CoV-2 viruses are lodged deep in the lungs, since COVID-19 mainly affects the lower respiratory tract. Then the illness quickly becomes critical, and the most severe cases must be immediately connected to a ventilator in the intensive care unit.

Because there are too few intensive care beds with ventilators even in high-technology countries such as Italy and Spain, doctors are increasingly having to decide who gets the lifesaving treatment and who doesn't.

Who needs to be ventilated and why?

Artificial respiration can save lives because if breathing stops, the organs are no longer supplied with oxygen. At the same time, the carbon dioxide produced during breathing is no longer exhaled via the lungs.

A short time after a respiratory arrest, the heart also stops beating and the circulation ceases, so that the patient dies within minutes. 

Read more: Coronavirus and ethics: 'Act so that most people survive'

Infografik Herz 2 Blutkreislauf ENG

How do ventilators work?

In simple terms, a ventilator pushes oxygenated air into the lungs at positive pressure and displaces fluid from the pulmonary alveoli, the tiny, balloon-shaped air sacs in which the exchange of oxygen and carbon dioxide molecules to and from the bloodstream takes place.

This sounds simple but is actually a highly complex treatment option. That is because modern ventilators can adapt the form of ventilation to the individual needs of the patient.

For pressure-controlled ventilation (PCV ventilation), the ventilator creates a certain pressure in the airways and the alveoli so that as much oxygen as possible can be absorbed. As soon as the pressure is high enough, exhalation begins. The respirator thus takes over the entire breathing process of the patient.

What do patients notice during artificial respiration?

In non-invasive artificial ventilation, the air is passed over the mouth and nose with the help of a tightly fitting ventilation mask. In invasive ventilation (intubation), the tube is pushed through the mouth or nose and into the trachea (windpipe). In the case of a tracheotomy, the doctor has direct access to the trachea through a small hole in the throat.

People who are connected to a ventilator can neither speak nor eat and are artificially fed through a tube. Since invasive ventilation, in particular, is very unpleasant, patients are usually put into an artificial coma with anesthetics for the duration of the treatment. 

Read more: Volkswagen explores using 3D printers to produce ventilators

Production of ventilators a the Dräger company in Lübeck
Demand is rising for ventilators worldwide: Dräger produces under high pressure. Image: picture-alliance/dpa/A. Heimken

Why are there too few ventilators?

During the coronavirus crisis, the demand for ventilators has increased dramatically because the health care systems in many countries are not geared to the need for so many respirators simultaneously.

However, such high-performance ventilators for intensive care use, which cost up to €50,000 ($55,842) apiece, cannot be purchased at short notice. There are only a few manufacturers of ventilators and so-called ECMO devices, which can enrich the blood with oxygen, i.e. work as an artificial lung.

Although these companies have increased their production capacities to the maximum, there are still supply bottlenecks, including for consumables such as breathing tubes and cannulas.

Dramatic shortfalls in the care of seriously ill COVID-19 patients can also occur if, for example, illness or quarantine leads to a lack of highly qualified personnel who can reliably operate these sometimes highly complex devices in intensive care.

What is the situation in Germany?

In Germany, 1,160 hospitals have intensive care beds (ITS). In all, 33.7 ITS beds are available per 100,000 inhabitants. Compared to other countries, this is far above average. In 2010, Italy, for example, had 12.5 beds per 100,000 inhabitants, less than half of Germany's intensive care capacity. In the Netherlands, the figure in 2018 was less than a quarter of Germany's capacity, with 7.1 beds per 100,000 inhabitants. The situation is similar in the Scandinavian countries. All countries, however, have worked to increase the number of ITS beds, recently.

Since many German hospitals are currently performing only absolutely necessary operations, additional ventilators from operating theaters are available in many places to treat COVID-19 patients. 

Read more: Coronavirus: Why are the death rates different?

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