Resuscitation as we understand it today was born in the middle of the 19th century, following the polio epidemic that was raging then, and for which the entire population is now vaccinated. It was at this time that the first resuscitation ventilators were invented. Thus, today, mechanical ventilation, carried out using devices called resuscitation ventilators, is a vital step in the management of patients with respiratory failure, in particular that linked to COVID-XNUMX, but also in other indications where the lungs are weak, such as severe flu or coma. This medical intervention must be reserved for competent and qualified personnel. Patients should be able to wean themselves off the ventilator as soon as possible. The resuscitation ventilator supplies oxygen to the patient (oxygenation) and removes carbon dioxide (ventilation). Professor Alexandre Demoule, intensive care physician and head of department at La Pitié Salpêtrière Hospital, sheds light on the subject.

Resuscitation as it exists today dates from the mid-twentieth century. In fact, at that time, the first center for the treatment of respiratory forms of polio was created at Claude Bernard Hospital in 1954. The first respirators appeared around this time. “The ventilator, in intensive care, is a machine that will temporarily replace the function of the lungs when they have become too sick to perform their role, which is to draw oxygen from the air and put it in the blood. ”, Explains Professor Alexandre Demoule, intensive care physician and head of the intensive care unit at Pitié Salpêtrière.

The first to have recommended, in terms of artificial ventilation, the use of mouth-to-mouth, were Réaumur then Buchanan, from 1740 and 1759. As for the origins of the very first model of mechanical ventilation, using a lung of steel, these date back to 1876. Thereafter, respirators experienced a real boom in the mid-twentieth century, the most remarkable of these devices being at the time the respirator of Engström 150, a robust device but whose main weakness was the lack of alarms.

“The principle of operation of a respirator, indicates Professor Demoule, is to breathe into the trachea and the bronchi of a patient, into his lungs, a certain volume of air and oxygen, so cyclic”. It is thus necessary to choose, at the level of the settings, what quantity of gas will be insufflated to the patient, for example 300 or 400 mL at each insufflation, and at what frequency will be given this gas, for example 20 times per minute, 25 times per minute …

This respirator is made up of several elements:

• First of all, a mixer: a tank in which air and oxygen are mixed. The more sick the lungs are, the more oxygen will be required. A healthy person, when breathing, absorbs 21% oxygen. In a patient with a very severe form of COVID-19, for example, doctors sometimes need to provide 100% oxygen. This mixer is therefore the place where the respective proportion of air and oxygen will be metered;
• Then, the other extremely important component of the ventilator is the part which allows this gas mixture to rise in pressure, with the aim of being able to propel it inside the patient, through a pipe;
• This ventilator is connected to the patient through an intubation probe, a small piece of tubing that is slipped into the patient’s trachea. The specialized nursing staff will therefore connect the ventilator to this intubation probe;
• Finally, the third fundamental element of the respirator consists of a set of sensors. These make it possible to verify that the gas mixture is sent at the appropriate pressure, that it is indeed delivered at the frequency which has been set, or even, in particular, that the gas mixture which leaves the patient is indeed the same as the one we made fit into the patient. It is also necessary to ensure that the pressure entering the patient is not too high, which could damage his lungs. These sensors can also detect leaks in the system, they check the good working condition of the respirator which must effectively deliver this gas mixture safely.

Respirators have evolved enormously since their inception. “Resuscitation ventilators, born in the 1950s, made it possible to fight polio, which at the time was responsible for respiratory damage, causing paralysis of breathing,” explains Professor Alexandre Demoule. Respirators were therefore well developed at that time to be able to make patients’ lungs work while the patients were recovering from polio. 

In half a century, these respirators have finally changed a lot. While initially ventilators were extremely simple, as only the volume breathed into the patient was set as well as how often that volume was breathed in, now there are many more subtleties, for example if this volume is blown in quickly or on the contrary rather slowly. 

It is, moreover, also possible to adjust very precisely the pressure which one wishes to leave in the lungs at the end of the expiration. Today, ventilators are able to adjust the volume as needed by the patient. And respirators have made enormous progress in particular when it comes to resumption of autonomy, so they are able to restore autonomy to the patient in a much more flexible way when the latter can resume breathing on his own. Respirators have therefore become much more comfortable. Research and development are still very important today in the field of respirators.

Resuscitation respirators are essential for the management of respiratory arrest, hypoxemic or hypercapnic respiratory distress, in the event of shock, for the protection of the airways or even during general anesthesia which requires analgo- major sedation. Here are the various cases in which the use of the ventilator in intensive care is essential:

• In the severe form of COVID-19, very severe damage to the lungs prevents them from functioning properly, and it is therefore necessary that at this time a machine takes the place of the function of the lungs and temporarily replaces them, until that they heal: this is the function of the respirator;
• All other serious lung infections require the use of a ventilator, including influenza in its more severe forms;
• When a patient is in a coma, his lungs stop breathing properly, so in this case too, the ventilator will be essential to keep the lungs working while the patient comes out of the coma;
• As soon as there are very serious cardiac and circulatory problems, it is also generally necessary to place the patients on a ventilator, so as to put the lungs to rest while the circulation or the heart are better again.

The resuscitation ventilator is an extremely widely used care tool. Thus, in all intensive care units, there is one ventilator per room. “Any patient who is hospitalized in intensive care is likely to be placed under artificial respiration”, indicates Professor Demoule.

When a specialized team places a patient on a ventilator in intensive care, it begins by checking that the ventilator is in good working order. Then, the healthcare team prepares what is called intubation, and checks that everything is ready. “Indeed, it is a gesture during which the patient can run a risk, simply because he is very severely ill of the lungs”, specifies Alexandre Demoule. The patient is then put to sleep by means of anesthetic agents. Once the patient is asleep, using a metal tool called a laryngoscope, the intubating caregiver will lift the tongue until they can see the entrance to the trachea. A tube is then slipped inside the trachea: this tube is an intubation probe. Then, this intubation probe is connected to the ventilator. 

In a volumetric mode, the ventilator is set to deliver a tidal volume (VT) for a defined duration. In barometric mode, the regulated parameter is the insufflation pressure in the airways for a defined time. There are now more complex methods. Thus, today, many new generation ventilators are very efficient and provide the clinician with multiple ventilation modes.

The duration of respiratory assistance in a patient is very variable. For example, for a patient hospitalized in intensive care following a coma due to poisoning by a drug, but who will quickly eliminate this drug, respiratory assistance can last less than a day, or even half a day. In COVID-19, respiratory assistance lasts on average 2 to 3 weeks, which is really long, longer than for a flu for example. Some patients with COVID-19 may even be placed on a ventilator for 4, 5, or even 6 weeks.

When a patient is placed on a ventilator in intensive care, he is therefore initially put into an artificial coma. He usually doesn’t remember anything. And then, when his condition improves a little, he is woken up, and he will then be placed on medication so that he is not anxious and does not suffer from pain. He will then start breathing a little on his own, which will be done gradually, until the day when we can separate him from the ventilator. At this point, the intubation tube will be removed: this is called extubating.

Putting on life support with a ventilator in intensive care has two objectives: on the one hand, it is survival. “Indeed, the lungs broke down, recalls Professor Demoule. So their job, which is to oxygenate the human body, is no longer being done. However, oxygen is the fuel of cells. So if there is no more oxygen, the heart stops, the brain stops. The patient dies ”. By replacing the lung, the ventilator will thus allow the patient to stay alive. If there is no ventilator when the lungs are very sick, the patient will die. The first of the spectacular results of the ventilator in intensive care is therefore to keep the patient alive.

On the other hand, the second effect of this ventilator is to allow the lungs to rest a little while they repair themselves. Ultimately, this machine allows the patient to survive until the lungs are again able to function on their own.

“There is no treatment in medicine that does not have side effects, unfortunately,” notes Professor Demoule. The respirator also has undesirable effects. First of all, the simple fact that a pipe is made to enter the trachea will allow the bacteria to enter the trachea themselves: this therefore promotes the development of nosocomial infections, linked to care. 

Another effect is due to the fact that the patient’s breathing is taken care of: however, since the ventilator takes care of all the patient’s respiratory work, this causes the patient a small melting of his respiratory muscles. It will therefore be necessary, then, to re-educate the lungs. “In fact, when the patient begins to breathe on his own, he will present difficulties because his lungs will have melted a little,” says Professor Demoule. It is the patient himself who will carry out this rehabilitation, when the specialized care team begins to gradually restore the patient’s respiratory autonomy. The healthcare team will thus make him breathe a little on his own, first 5%, then 10%, 20%: throughout this period, the patient re-educates himself, until he is able to breathe again on his own. .

And Professor Demoule concludes: “But the main side effect that really remains are infections”. In fact, the other potential side effects are not only related to the ventilator, but also to the fact that the patient is very ill. 

Ultimately, compared to the COVID-19 pandemic that has raged around the world since November 2019, Professor Demoule believes that, for the French intensive care services, the most critical point is not currently the number of ventilators: behind the machine requires personnel, that is, resuscitation nurses and resuscitators. Without these people, it is impossible to take care of patients with this ventilator. 

“The shortage of personnel is cruel, and no matter how much you increase the number of ventilators, if the number of trained personnel does not increase, you will not be able to use these ventilators and therefore treat patients with these ventilators.” Professor Demoule assures us that, in his hospital in La Pitié Salpêtrière, there is no shortage today of respirators in proportion to the staff that it is possible for him to mobilize. On the other hand, if the epidemic were to increase a lot and he had to open more intensive care beds, he had enough staff in his department, but if he wanted to increase the size of his department in order to to take care of more patients, in this case the professor explains that there would then be a lack of qualified personnel: essentially, nurses competent in intensive care.