Breathing is one of the most important signs of life that has been identified with life since ancient times. So much so that this activity is almost identified with life. However, it was not understood for a long time how this activity took place and what its purpose was. Ancient philosophers suggested that breathing took place for various purposes such as ventilating the soul, cooling the body, and replacing the air coming out of the skin. Wind and spirit are used synonymously. (pnemone) Then this sözcüIt has survived to the present day as lung (pneumonia) and pneumonia (pneomnia). According to a similar view widely adopted in China and India in the same period, the process of breathing was considered in relation to the element of air, which is thought to be a part of the soul, and breathing was thought to be a result of this interaction. Especially in eastern cultures, the idea has emerged that some kind of relaxation or increase in cognition will occur through breath control. Although it was known in this period that breathing was necessary for sustaining life, a satisfactory relationship was not established with the above-mentioned intellectual foundations, and methods such as hitting the body with hard blows, hanging the body upside down, compressing it, applying smoke from the mouth and nose were applied in order to reactivate the stopped breathing. These applications have been tried both for the treatment of people with respiratory difficulties and for the "reanimation" of the person in deaths caused by respiratory arrest. It was in later ages that experimental knowledge and practical applications began to be seen as one of the basic elements of human thought. Physiological experiments and examinations on animals in the newly established city of Alexandria focused attention on how respiration occurs. The roles of muscles and organs such as the diaphragm, lungs, etc. began to be understood in this period. In the following period, Avicenna began to approach the modern understanding in ideas about purpose, with the view that breathing was used as a movement mechanism for the heart (or spirit) to give life to the body, and each inhalation caused exhalation and the next cycle.
History of Ventilators
After understanding the mechanism and purpose of breathing, the idea of using this knowledge in life-saving treatments by designing various methods and mechanisms emerged in the late 1700s with the understanding of oxygen and its importance for human life. The development of these ideas and mechanisms over time will lead to modern ventilators and form the basis for the establishment of intensive care units as we know them. Pandemics have played an important role in this development. Problems encountered during this process and iatrogenic (undesirable or harmful conditions occurring during diagnosis and treatment) are issues that should be considered in modern ventilator designs. In order to understand the modern ventilator and the problems it is trying to solve, it will be useful to examine the development of the subject.
1. A dangerous method
The mouth-to-mouth resuscitation (resuscitation) method is one of the first applications on the subject. However, the fact that the exhaled breath is poor in terms of oxygen, the risk of disease transmission and the inability to continue the process for a long time limit the clinical benefits and usability of the application. The first method used to solve these problems was to apply compressed air to the lungs of the patient through a bellows or pipe. Applications related to the subject are encountered in the early 1800s. However, this method has led to many cases of iatrogenic pneumothorax. Pneumothorax is a phenomenon of contraction of the lungs, also described as collapse. The compressed air applied by the bellows bursts the air sacs in the lung and causes the double-leafed pleura, called the pleura, to fill between the leaves. Although mortality can be minimized by surgical procedures such as catheter application, mechanical intervention with thoracoscopy, pleurodesis, re-gluing of leaves, and thoracotomy, the process is still very risky compared to many pneumonias. As a result of iatrogenic damages, in this period when the above-mentioned opportunities were very limited, the application of positive pressure air to the lungs was classified as dangerous and the practice was largely abandoned.
2. Iron Liver
After positive pressure ventilation attempts were deemed dangerous, studies on negative pressure ventilation gained importance. The purpose of negative pressure ventilation devices is to facilitate the work of the muscles that provide respiration. The first negative pressure ventilator, invented in 1854, used a piston to change the pressure of a cabinet in which the patient was placed.
Negative pressure ventilation systems were large and expensive. In addition, iatrogenic effects called “tank shock” were observed, such as gastric fluids rising up and blocking the trachea or filling the lungs. Although these systems did not increase in number, they found a place for use in large hospitals, especially for respiratory difficulties caused by muscles and during surgery, and were used successfully for a while. Similar devices are still used in the treatment of neuromuscular diseases, especially in Europe.
3. Cautious steps
The great polio pandemic of 1952 in the USA and Europe marked a turning point in mechanical ventilation. Despite the drug and vaccine studies used in previous polio epidemics, the pandemic could not be prevented and the health system became unable to respond to the need with the number of cases far above the capacity of the hospitals. At the peak of the epidemic, mortality in patients who were admitted to the hospital with symptoms of respiratory muscles and bulbar palsy increased to around 80%. At the beginning of the pandemic, deaths were thought to be from renal failure due to systemic viremia due to terminal symptoms such as sweating, hypertension, and high carbon dioxide in the blood. An anesthesiologist named Bjorn Ibsen suggested that the deaths were caused by breathing difficulties, not kidney failure, and suggested positive pressure ventilation. Although this theory met with resistance at first, it started to be accepted as the mortality decreased to 50% in patients who underwent manual positive ventilation. The limited number of ventilation devices produced in a short time continued to be used after the epidemic. From now on, the focus of ventilation shifted from reducing the load on the respiratory muscles to applications to increase the oxygen level in the blood and ARDS (Acute Respiratory Distress Symptom) treatment. The iatrogenic effects seen in the previous positive pressure ventilation were partially overcome with non-invasive applications and the PEEP (Poisitive end expiratory pressure) concept. The idea of gathering all patients in one spot to benefit from a single ventilator or manual ventilation team also emerged during this period. Thus, the foundation of modern intensive care units, in which ventilators and physicians who have developed expertise in the subject, are an integral part, was laid.
4. Modern Ventilators
Studies conducted in the following period revealed that the damage in the lungs was not caused by high pressure, but mainly due to long-term overdistension in the alveoli and other tissues. In line with the emergence of processors and the needs of different diseases, volume, pressure and flow began to be controlled separately. Thus, devices that are much more useful and can be adjusted according to different applications were obtained compared to only "volume" control. Ventilators are used for drug administration, oxygen support, complete takeover of breathing, anesthesia, etc. It started to be designed to include different modes for many different purposes.
Ventilator Device and Modes
Mechanical ventilation is the controlled and purposeful delivery and recovery of related gases into the lungs. The devices used to perform this process are called mechanical ventilators.
Today, ventilators are used to serve many different clinical purposes. These clinical applications include providing gas exchange, facilitating or taking over respiration, regulating systemic or myocardial oxygen consumption, providing lung expansion, administration of sedation, administration of anesthetics and muscle relaxants, stabilization of the rib cage and muscles. These functions are performed by the ventilator device through continuous or intermittent pressure/flow application of the processes of inhalation and exhalation, also using feedback from the patient. Ventilators can be connected to the patient externally or through the nostrils, intubated through the windpipe or trachea. Most ventilators can perform many of the above operations and also perform additional functions such as nebulizing or providing oxygen support. These functions can be selected as various modes and can also be controlled manually.
Modes commonly found on ICU ventilators are:
- P-ACV: Pressure-controlled Assisted Ventilation
- P-SIMV+PS: Pressure Controlled, Pressure Supported Synchronized Forced Ventilation
- P-PSV: Pressure Controlled, Pressure Supported Ventilation
- P-BILEVEL: Pressure Controlled, bi-level ventilation
- P-CMV: Pressure Controlled, continuous mandatory ventilation
- APRV: Airway pressure Relief Ventilation
- V-ACV: Volume Controlled Assisted Ventilation
- V-CMV: Continuous Forced Ventilation with Volume Control
- V-SIMV+PS: Volume Controlled Pressure Supported Forced Ventilation
- SN-PS: Spontaneous Pressure Support Ventilation
- SN-PV: Spontaneous Volume Supported Non-Invasive Ventilation
- HFOT: High Flow Oxygen Therapy Mode
Apart from intensive care ventilators, there are also ventilator devices for anesthesia, transport, newborn and home use. Some of the terms and applications frequently used in the field of mechanical ventilation, including leg ventilators, are as follows:
- NIV (Non Inavsive Ventilation): It is the name given to the external use of the ventilator without intubating.
- CPAP (Continious Positive Airway Pressure): The most basic support method in which constant pressure is applied to the airway
- BiPAP (Bilevel Positive Airway Pressure): It is the method of applying different pressure levels to the airway during breathing.
- PEEP (Positive Airway End Expiratoey Pressure): It is the maintenance of the pressure on the airway at a certain level by the device during exhalation.
ASELSAN Ventilator Studies
ASELSAN started working on “Life Support Systems”, which it has determined as one of the strategic areas in the health sector, in 2018. It has started to work with various domestic companies and sub-unit suppliers in line with the vision of creating the relevant ecosystem by using the existing studies and experiences in Turkey on the ventilator, which is one of the main devices in this field. Cooperation agreements have been signed with BOISYS company, which works on ventilators in our country. In this context, technical studies and studies have been carried out to transform the ventilator device, which is being studied by BIOSYS, into a product that can compete on a global scale.
In line with the need for ventilators, which are considered to occur in Turkey and in the world with the COVID pandemic at the beginning of 2020, a rapid work has been started with local and foreign companies operating in Turkey for both BIOSYS and different types of ventilators under the support and coordination of the Presidency of Defense Industries. The first problem encountered during this study was that the supply from ventilator sub-part manufacturers such as valves and turbines, which were previously easily and to some extent cost-effectively procured from abroad, became difficult due to the need or high demand in their own countries. For this reason, the design and production of proportional and expiratory valves, turbine and test liver critical sub-components were carried out both to support domestic ventilator manufacturers and to be used in the production of BIYOVENT, which is being worked on with BIOSYS. HBT Sector Presidency made significant contributions in the design and production parts of the valve component.
Simultaneously with this study, hardware and software design studies for the maturation of the BIOVENT device were carried out together with BAYKAR and BIOSYS. ARÇELİK facilities were utilized for the production of the unearthed product in large quantities in a short time. The design and production activities for a medical device were completed in a very short time, and it started to be shipped to both Turkey and the world in June. In the following period, the production infrastructure for BIOVENT production was established at ASELSAN and the production of the device was transferred to ASELSAN. Today, ASELSAN has a production capacity of hundreds of ventilators per day. The device continues to be produced and shipped to the points of need in Turkey and the world.
In cooperation with local companies for ventilators, ASELSAN continues to work on creating an ecosystem, optimizing the designs of sub-components and expanding the production capability. In addition to these, it is planned to design new version ventilators by including the topics that are considered to be the technologies of the future in the ventilator, such as feedback from the diaphragm or nervous system, better evaluation of patient responses and artificial intelligence applications.
SARS COV 2 disease, which we are currently experiencing a pandemic period, requires the use of ventilators in severe patients. However, for example, the treatment of SARS COV disease, another type of coronavirus detected in 2003 and which has not reached the level of pandemic, requires much more ventilators. Similar coronaviruses and mutations are likely to emerge after the pandemic. There are also threats such as rhinovirus and influenza that may create similar needs. In such a scenario, the need for intensive care personnel, intensive care units and ventilators will increase, and the world supply chain may be interrupted for much longer periods. For this reason, preserving domestic and national production capability, creating an ecosystem and stocking ventilators at a certain level will be appropriate approaches.