Since the beginning of the Covid-19 pandemic, almost all of us in one way or another have recalled the existence of intensive care units and intensive care units, many have repeatedly in vain mentioned oxygen saturation and mechanical ventilation. Participants in online battles over the past spring have become couch experts in medical technology, respiratory support, and even protective ventilation strategies. A shortage of devices, spontaneous detonations, "miraculous" inventions of matches and acorns, and mind-blowing ideas about ventilation of several patients with one ventilator - the ventilator has firmly entered the information field of the last year. If a doctor became the Person of the Year 2020 according to Time magazine, then the Device of the Year, if there was such a nomination, would definitely become a ventilator.
Artificial ventilation is one of the pillars of intensive care and remains the cornerstone of treatment for respiratory failure. It is about the history of mechanical ventilation that will be discussed in this article.
As usual in medicine, almost everything that is used in treatment, to one degree or another, was described either by Hippocrates, or by Galen, or by the ancient Egyptians. In the case of artificial ventilation, we have the most real bingo - almost all ancient authors from medicine (and even in the Bible!) One way or another uses artificial respiration both by the "mouth-to-mouth" method, and with the help of trachea incisions, various tubes and reed and reed cannula. Tubes were inserted into the trachea either by intubation (passing a tube into the trachea through the mouth) or by tracheostomy (a tube was inserted into the trachea through an artificial opening below the vocal cords). Even then, people intuitively understood the idea of ​​the need to replace the respiratory function in cases of suffocation or drowning. Galen, renowned Roman physician and philosopher of Greek descent,In his writings, who described artificial respiration in animals in an experiment, he considered the movement of the lungs during breathing to be the decisive factor in maintaining life in the body.
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The Middle Ages were not rich in discoveries both in medicine in general and, in particular, in the field of mechanical ventilation. Scientists of the West and the East may not have increased, but preserved the knowledge of Antiquity and applied them as they understood human anatomy and physiology. In the "Canon of Medicine" Avicenna already described gold and silver cannulas for tracheostomy. At the same time, in the European writings of the XIII century, tracheostomy is called "semi-murder and surgery scandal", which is probably due to the imperfection of the surgical technique and the complex anatomy of the trachea.
Following the Middle Ages, which preserved the achievements of Antiquity, the Renaissance era came, marked by new discoveries and ideas, including in the anatomy and physiology of respiration. Andreas Vesalius, professor of anatomy at the University of Padua, author of the fundamental work De Humani Corporis Fabrica (On the structure of the human body) did not ignore this problem. In a unique work that brought its creator the rank of physician-in-chief under Charles V, in addition to the structure of the human body, an experiment to revive animals by means of artificial lung ventilation is described:
In order for life to return to the animal, it is necessary to make a hole in the trunk of the windpipe, where to insert a tube made of reeds or reeds and blow into it so that the lung rises and delivers air to the animal.
The culprit of this paragraph against the background of his experience is
also credited with successful resuscitation by means of artificial respiration, which, however, turned out to be sad for the professor. A miraculous revival occurred during ... the autopsy of a Spanish nobleman. The corpse of the latter suddenly began to show signs of life, but Vesalius was not taken aback and by his actions saved the man. The nobleman subsequently recovered from his wounds, but the scientist himself was under investigation by the Inquisition on charges of murder. As a penance, Vesalius and his family were assigned a pilgrimage to Jerusalem, however, this journey was the last for the great anatomist. On the way back, as a result of a shipwreck, the scientist ended up on the Greek island of Zante, where he died under unexplained circumstances in 1564.
Following the discoveries of the Renaissance, the famous English naturalist and inventor Robert Hooke, who gave the world the concept of a "cell" and made many discoveries in the field of physics, also conducted research in the field of respiration physiology and artificial ventilation. An experiment presented by him in 1664 at a meeting of the Royal Scientific Society (in many ways similar to Vesalius's experiment) proved that not only the movement of the lungs, but a constant flow of fresh air and gas exchange in the lungs is important for maintaining life. The discovery of Robert Hooke led to an increase in interest in artificial ventilation - researchers and inventors one after another throughout the 17th-18th centuries. offered various designs of portable resuscitation kits based on the principle of positive pressure ventilation - using bellows similar to blacksmiths,he had to blow (hehe) air into the patient's lungs. The discovery of oxygen by Joseph Priestley and its role in the life of living organisms by Antoine Lavoisier only increased interest in artificial ventilation.
Many manuals have been written on rescuing drowning and sudden deaths, reviving “supposedly dead” newborns. Among them there were genuine diamonds, offering to ventilate drowning people with tobacco smoke and administer tobacco enemas to them in order to dry out the insides and better stimulate blood circulation and respiration. Later, the recommendations became more moderate. Among them - published in St. Petersburg in 1799 "A short book for the people, containing an easy and understandable instruction, as with the deceased, frozen, strangled, fainted, hung or seeming to be dead, should be done." This manual instructed "to try to let him (that is, the victim) into the lungs again air by inhalation from mouth to mouth or using an inflatable bag."
Brave American resuscitators
Be that as it may, any method of treatment has its own complications, and mechanical ventilation is no exception. At the beginning of the 19th century, cases of rupture of the lungs and tense pneumothorax (accumulation of air in the pleural cavity) were recorded against the background of artificial respiration. And despite the rather simple and elegant solution to this problem - the French doctor Leroy d'Etyol added a simple Soviet line to the furs to regulate the inhaled volume - the interest of the world medical community in ventilation by blowing air into the patient's lungs has cooled somewhat. At the same time, with the increasing accumulation of knowledge about the anatomy and physiology of the respiratory system, progressive mankind came to the idea that for physiological replacement of the function of external respiration, it is necessary not to blow air into the lungs,and to replace the work of the respiratory muscles to create negative pressure in the chest cavity. This is how negative pressure ventilation appeared.
Tank Ventilator
One of the first vehicles to use this principle was the Tank Ventilator, created by Albert Jones in 1864. It was a sealed container in which the patient was placed in such a way that only the head remained outside the "cistern". Then a relative vacuum was created in the apparatus, by means of which the respiratory cycle was then simulated. According to the assurances of its creator, the device cured almost all diseases, from paralysis and asthma to neuralgia and even deafness. Further design improvements have led to a prototype device of the "iron lung" class. Its author, the Parisian physician Alfred Voye, proposed to arrange a whole network of such devices along the Seine to rescue drowning people. A significant disadvantage of such devices, with the exception of the complexity and high cost, was the lack of constant access to the patient's body and, as a consequence,serious difficulties in caring for the patient. In an attempt to overcome this disadvantage, entire rooms were built in which intermittent negative pressure was created using a system of giant pistons. This made it possible not only to provide care and treatment, but even to carry out operations! However, the construction and maintenance of such premises demanded incredible financial costs, and therefore they were not widely used.
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In the first half of the 20th century, both positive pressure and negative pressure ventilation developed in parallel. In 1907, the German company Dräger created the Pulmotor, the first fully automated ventilator complete with an oxygen cylinder and face mask. It worked on the principle of a clockwork mechanism and rhythmically dispensed equal portions of the oxygen-air mixture. Due to the fact that the device was placed in a relatively small suitcase, it quickly gained popularity among mountain rescuers. Also, positive pressure ventilation has found its application in the field of anesthesiology, where, by connecting a hand bag, a ventilator and a vaporizer, an anesthetic apparatus was obtained, without which it is impossible to imagine any operating room today.The field of ventilation with negative pressure still remained a wide field of diseases and disorders of the respiratory system. The “iron lungs” designs of Drinker & Shaw and Emerson covered a wide range of diseases from paralysis of the respiratory muscles to bronchial asthma.
Dräger Pulmotor
The 50s of the XX century were marked by the height of the polio epidemic. As today, most cases of the disease were moderate, mild, or even asymptomatic, but the scale of the spread of the infection has led to a critical increase in the number of severe forms of the disease. Details of the chronicles of the epidemic and the heroic efforts of Soviet and American virologists, the symptoms and pathogenesis of the disease can be found in the article authored by Ekaterina Ulyanova (link is provided at the end of the article) or on the website of the World Health Organization, and in the meantime, we will return to the patient's bed. In severe cases, the polio virus infects the nuclei of the spinal cord and medulla oblongata, which leads to paralysis of the respiratory muscles - the patient cannot breathe.In an epidemic, the number of such patients turned out to be critical for the health care of that time - the available "iron lungs" were not enough for all patients. This situation has forced the medical community to return to positive pressure ventilation due to its relative simplicity and low cost. New ventilators with PPV (positive pressure ventilation) began to appear, their production was rapidly established, but the shortage of devices was still felt very acutely. An illustrative example is Copenhagen, where almost 1,500 medical students, replacing each other, for 19 weeks carried out manual ventilation using Ambu bags (while not stopping from classes!).This situation has forced the medical community to return to positive pressure ventilation due to its relative simplicity and low cost. New ventilators with PPV (positive pressure ventilation) began to appear, their production was rapidly established, but the shortage of devices was still felt very acutely. An illustrative example is Copenhagen, where almost 1,500 medical students, replacing each other, for 19 weeks carried out manual ventilation using Ambu bags (while not stopping from classes!).This situation has forced the medical community to return to positive pressure ventilation due to its relative simplicity and low cost. New ventilators with PPV (positive pressure ventilation) began to appear, their production was rapidly established, but the shortage of devices was still felt very acutely. An illustrative example is Copenhagen, where almost 1,500 medical students, replacing each other, for 19 weeks carried out manual ventilation using Ambu bags (while not stopping from classes!).where almost 1,500 medical students, replacing each other, for 19 weeks carried out the ventilation of the lungs manually using Ambu bags (while not stopping from classes!).where almost 1,500 medical students, replacing each other, for 19 weeks carried out the ventilation of the lungs manually using Ambu bags (while not stopping from class!).
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As the epidemic progressed, technology developed and clinical experience accumulated, it quickly became clear that positive pressure ventilation, despite its non-physiological principle of operation, largely outperforms the "iron lungs" - it is much easier to control breathing parameters, ensure airway patency and exercise general patient care. Another important feature of the new devices was the use of positive end-expiratory pressure (PEEP), which prevented the inevitable collapse and damage of the pulmonary alveoli during ventilation. Positive pressure ventilators have shown themselves to be safer and more efficient than their colleagues in the shop. Yes, the old problems have not disappeared, moreover, new ones have been added to them - in addition to the damaging effect of volume,flow and pressure during ventilation, the problem of cooperation with the patient arose. However, the devices of the second generation had not only thinner instruments for breathing control, but also the ability to record the patient's breathing attempt and help it. Departments and centers dealing exclusively with artificial ventilation of the lungs began to appear - they were the beginning of what we now call the Department of Resuscitation and Intensive Therapy.
Bird Mk7, one of the first devices with PPV
Today, artificial ventilation is one of the most important and most high-tech branches of resuscitation and intensive care. Modern ventilators solve a wide range of tasks: from assisted respiratory support to full-fledged invasive ventilation of the lungs in accordance with the current understanding of respiratory physiology, the latest patient-ventilator feedback systems and strategies to protect the lungs from ventilator-associated damage. Despite a number of problems, the experience of the current SARS-CoV-2 pandemic has shown the enormous potential of mechanical ventilation to replenish the function of external respiration and has repeatedly proven that a ventilator is a life-saving device.
An illustration showing that the idea of ​​connecting several patients to one ventilator has certain difficulties.
Be healthy :)
Author: Pavel Zavgorodniy
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