How artificial respirators work

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Spain and the rest of the countries in the world in which the coronavirus pandemic strikes with the most virulence have been racing to acquire respirators, or even manufacture them, in order to treat the most serious cases. The Health Minister, Salvador Illa, announced days ago in the Congress of Deputies that 400 respirators would be manufactured daily in our country. They are, as we can see, a fundamental instrument to increase the survival possibilities of the most seriously ill patients, but who until very recently were great strangers to the majority of citizens.

What are these devices?

An artificial respirator, or mechanical ventilator, is nothing other than a machine that performs lung ventilation for us, or helps to perform it, in patients who are suffering from acute respiratory failure, who are in a comatose state or under sedation. That is, it introduces and removes air from our lungs at intervals and in predetermined amounts, so that they can carry out the gas exchange in the pulmonary alveoli and continue to carry oxygen to our cells.

How do they work?

Today's respirators use a turbine to generate the air flow that we want to send to the patient. They must be connected, in addition to the electrical current, to an oxygen and an air intake. The latter is essential so that the necessary gas mixture is made inside the respirator to be able to introduce air into the patient's lungs with the desired oxygen concentration (also known as FiO2), and which will vary according to his condition. That resulting gas mixture is blown into the individual at a pressure higher than atmospheric to force the lungs to fill, since they have a lower pressure.

What can we health professionals regulate?

With the most advanced models, we can handle all kinds of parameters in addition to the mixture of oxygen and air. Depending on the state and the needs of the patient, we can regulate from basic aspects such as the respiratory rate to the humidity of the air, going through the amount of it that we introduce into the respiratory system or the pressure at which we do it.

Where are they used?

Respirators are used daily with all types of patients in hospital intensive care units and operating rooms. Its use is also daily in ambulances, medical helicopters and emergency services, although in these cases it is a portable device of smaller size and benefits.

Since when are they used?

Although the first artificial respirator dates back to 1907, its use would not become popular in healthcare practice within hospitals until 1950. This fact curiously coincides with another epidemic also caused by a virus, in this case the one that causes polio. Since then and until today, these devices that have saved thousands of lives and have contributed to improve surgeries, have evolved at a dizzying rate.

What is the security they have?

The models of artificial respirators that achieve homologation by the Spanish Agency of Medicines and Health Products (AEMPS) for their commercialization and use in health centers must have met very strict requirements for safety, efficacy and quality established in current legislation. . In addition to fulfilling its main function, its use may not compromise in any case the clinical status or safety of the patient, nor that of the healthcare professional who manages it.

The health crisis caused by Covid-19 has generated a need for respirators well above current availability, which has led many citizens and companies to try to put their shoulders on the wall by manufacturing home respirators with more or less success. The AEMPS has stepped up preparing a report with the technical documentation and minimum tests that must be carried out on these machines before use in patients, and the regulatory agency is currently working with six projects in a fairly advanced state and that very soon they may be tested on patients in hospital centers.

Let us not forget that they are vital machines that, in addition, must have alarm systems that warn us in the event of pressure losses or errors of any kind and with duplicate systems so that, in case of failure of the first, the second comes into operation immediately.

How many types of respirators are there?

Mechanical fans can be of two kinds: invasive and non-invasive. The latter are those used with patients in a less serious clinical situation, while the former are intended for more serious individuals.

How does an invasive respirator work?

As its name suggests, it is a system that invades the patient's interior. To be able to bring air to the patient's lungs, we must previously introduce a tube through the mouth that will reach the trachea (known as the endotracheal tube), where it will be fixed with the help of a pneumotapping balloon. Next, we will connect this tube to the respirator with the help of a respiratory circuit made up of two tubes and a Y-shaped piece. One of these tubes is responsible for introducing air (inspiratory branch) and the other for removing it from the patient (expiratory branch ).

How does a non-invasive respirator work?

In this case, the patient is not intubated. It is enough to fix a mask over the mouth and nose with the help of straps that are passed behind the patient's head to prevent air leaks. This mask is connected to the respirator with the help of a single tube that helps in the inspiratory function.

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