Severe respiratory disorders require emergency assistance in the form of forced ventilation. Whether the failure of the lungs themselves or the respiratory muscles is an unconditional need to connect complex equipment to saturate the blood with oxygen. Various models of ventilators are an essential equipment of intensive care or resuscitation services necessary to maintain the life of patients who have manifested acute respiratory disorders.
In emergency situations, such equipment, of course, is important and necessary. However, as a means of regular and long-term therapy, it, unfortunately, is not without drawbacks. For example:
- the need for a permanent stay in the hospital;
- permanent risk of inflammatory complications due to the use of a pump to supply air to the lungs;
- restrictions on the quality of life and independence (immobility, inability to eat normally, speech difficulties, etc.).
To eliminate all these difficulties, while simultaneously improving the process of blood oxygen saturation, the innovative artificial lung system iLA allows resuscitation, therapeutic and rehabilitation use of which is offered today by German clinics.
Risk-free coping with respiratory distress
The iLA system is a fundamentally different development. Its action is extrapulmonary and completely non-invasive. Respiratory disorders are overcome without forced ventilation. The scheme of blood oxygen saturation is characterized by the following promising innovations:
- lack of an air pump;
- absence of invasive ("embedded") devices in the lungs and airways.
Patients who have an artificial lung iLA are not tied to a stationary device and a hospital bed, they can move normally, communicate with other people, eat and drink on their own.
The most important advantage: there is no need to introduce a patient into an artificial coma with artificial respiratory support. The use of standard ventilators in many cases requires a comatose "shutdown" of the patient. For what? To alleviate the physiological consequences of respiratory depression of the lungs. Unfortunately, it is a fact: ventilators depress the lungs. The pump delivers air under pressure. The rhythm of air supply reproduces the rhythm of breaths. But on a natural breath, the lungs expand, as a result of which the pressure in them decreases. And at the artificial inlet (forced air supply), the pressure, on the contrary, increases. This is the oppression factor: the lungs are in a stress mode, which causes an inflammatory reaction, which in especially severe cases can be transmitted to other organs - for example, the liver or kidneys.
This is why two factors are of paramount and equal importance in the use of pumped respiratory support devices: urgency and caution.
The iLA system, by expanding the range of benefits in artificial respiratory support, eliminates the associated dangers.
How does a blood oxygenator work?
The name "artificial lung" has a special meaning in this case, since the iLA system operates completely autonomously and is not a functional addition to the patient's own lungs. In fact, this is the world's first artificial lung in the true sense of the word (and not a pulmonary pump). It is not the lungs that are ventilated, but the blood itself. A membrane system was used to saturate the blood with oxygen and remove carbon dioxide. By the way, in German clinics, the system is called so: a membrane ventilator (iLA Membranventilator). Blood is supplied to the system in a natural order, by the force of compression of the heart muscle (and not by a membrane pump, as in a heart-lung machine). Gas exchange is carried out in the membrane layers of the apparatus in much the same way as in the alveoli of the lungs. The system really works as a “third lung”, unloading the sick respiratory organs of the patient.
The membrane exchange apparatus (the "artificial lung" itself) is compact, its dimensions are 14 by 14 centimeters. The patient carries the instrument with him. Blood enters it through a catheter port, a special connection to the femoral artery. To connect the device, no surgical operation is required: the port is inserted into the artery in much the same way as a syringe needle. The connection is made in the inguinal zone, the special design of the port does not restrict mobility and does not cause any inconvenience to the patient at all.
The system can be used without interruption for quite a long time, up to one month.
Indications for iLA use
In principle, these are any respiratory disorders, especially chronic ones. To the greatest extent, the advantages of an artificial lung are manifested in the following cases:
- chronic obstructive pulmonary disease;
- acute respiratory distress syndrome;
- respiratory injuries;
- the so-called Weaning phase: weaning from the ventilator;
- patient support before lung transplantation.
American scientists from Yale University, led by Laura Niklason, have made a breakthrough: they managed to create an artificial lung and transplant it into rats. Also, a lung was created separately, which works autonomously and imitates the work of a real organ.
It must be said that the human lung is a complex mechanism. The surface area of one lung in an adult human is about 70 square meters, assembled so as to ensure the efficient transfer of oxygen and carbon dioxide between blood and air. But lung tissue is difficult to repair, so at the moment the only way to replace damaged parts of the organ is a transplant. This procedure is very risky due to the high percentage of rejections. According to statistics, ten years after transplantation, only 10-20% of patients remain alive.
Laura Niklason comments: "We have been able to design and manufacture a transplantable lung in rats that efficiently transports oxygen and carbon dioxide and oxygenates hemoglobin in the blood. This is one of the first steps towards recreating a whole lung in larger animals and eventually in humans" .
Scientists have removed cellular components from the lungs of an adult rat, leaving branching structures of the pulmonary tract and blood vessels that served as a scaffold for new lungs. And they were helped to grow lung cells by a new bioreactor that mimics the process of lung development in an embryo. As a result, the grown cells were transplanted onto the prepared scaffold. These cells filled the extracellular matrix - a tissue structure that provides mechanical support and transport of substances. Transplanted to rats for 45-120 minutes, these artificial lungs took in oxygen and expelled carbon dioxide just like real ones.
But researchers from Harvard University managed to simulate the work of the lung offline in a miniature device based on a microchip. They note that the ability of this lung to absorb nanoparticles in the air and mimic an inflammatory response to pathogenic microbes provides fundamental evidence that microchip organs can replace laboratory animals in the future.
Actually, scientists have created a device for the wall of the alveoli, the pulmonary vesicle, through which gas exchange with capillaries is carried out. To do this, they planted epithelial cells from the alveoli of the human lung on a synthetic membrane on one side, and cells of the pulmonary vessels on the other. Air is supplied to the lung cells in the device, a liquid imitating blood is supplied to the "vessels", and periodic stretching and compression transmits the breathing process.
To test the new lungs' response to exposure, the scientists had him "breathe in" Escherichia coli bacteria along with the air that had entered the "lung" side. And at the same time, from the "vessels" side, the researchers released white blood cells into the fluid flow. Lung cells detected the presence of the bacterium and launched an immune response: white blood cells crossed the membrane to the other side and destroyed foreign organisms.
In addition, the scientists added nanoparticles, including typical air pollutants, to the air "inhaled" by the apparatus. Some types of these particles got into the lung cells and caused inflammation, and many passed freely into the "blood stream". At the same time, the researchers found that the mechanical pressure during breathing significantly enhances the absorption of nanoparticles.
Artificial lungs, compact enough to be carried in a regular backpack, have already been successfully tested on animals. Such devices can make the lives of those people whose own lungs do not function properly for any reason much more comfortable. Until now, very bulky equipment has been used for these purposes, but a new device being developed by scientists at the moment can change this once and for all.
A person whose lungs are unable to perform their main function, as a rule, join machines that pump their blood through a gas exchanger, enriching it with oxygen and removing carbon dioxide from it. Of course, during this process, a person is forced to lie on a bed or couch. And the longer they lie down, the weaker their muscles become, making recovery unlikely. It is in order to make patients mobile that compact artificial lungs have been developed. The problem became especially relevant in 2009, when there was an outbreak of swine flu, as a result of which many of the sick people lost their lungs.
Artificial lungs can not only help patients recover from certain lung infections, but also allow patients to wait for suitable donor lungs for transplantation. As you know, the queue can sometimes stretch for many years. The situation is complicated by the fact that in people with failed lungs, as a rule, the heart, which has to pump blood through, is also very weakened.
“Creating artificial lungs is a much more difficult task than designing an artificial heart. The heart simply pumps blood, while the lungs are a complex network of alvioli, within which the process of gas exchange takes place. To date, there is no technology that can even come close to the efficiency of real lungs, ”says William Federspiel of the University of Pittsburgh.
William Federspiel's team has developed an artificial lung that includes a pump (supporting the heart) and a gas exchanger, but the device is so compact that it can easily fit into a small bag or backpack. The device is connected to tubes connected to the human circulatory system, effectively enriching the blood with oxygen and removing excess carbon dioxide from it. This month, successful tests of the device on four experimental sheep were completed, during which the blood of animals was saturated with oxygen for different periods of time. Thus, scientists gradually brought the time of continuous operation of the device to five days.
An alternative model of artificial lungs is being developed by researchers at Carnegie Mellon University in Pittsburgh. This device is intended primarily for those patients whose heart is healthy enough to independently pump blood through an external artificial organ. The device is connected in the same way to tubes that are directly connected to the human heart, after which it is attached to the body with straps. So far, both devices need a source of oxygen, in other words, an additional portable cylinder. On the other hand, at the moment, scientists are trying to solve this problem, and they are quite successful.
Right now, researchers are testing a prototype artificial lung that no longer needs an oxygen tank. According to the official statement, the new generation of the device will be even more compact, and oxygen will be released from the surrounding air. The prototype is currently being tested on lab rats and is showing some truly impressive results. The secret of the new model of artificial lungs lies in the use of ultra-thin (only 20 micrometers) tubules made of polymer membranes, which significantly increase the gas exchange surface.
The fact that breathing air into the lungs can revive a person has been known since ancient times, but auxiliary devices for this began to be produced only in the Middle Ages. In 1530, Paracelsus first used a mouth air duct with leather bellows designed to fan a fire in a fireplace. After 13 years, Vezaleus published the work “On the structure of the human body”, in which he substantiated the benefits of ventilation through the tube inserted into the trachea. And in 2013, researchers at Case Western Reserve University created a prototype artificial lung. The device uses purified atmospheric air and does not need concentrated oxygen. The device is similar in structure to a human lung with silicone capillaries and alveoli and works on a mechanical pump. Biopolymer tubes mimic the branching of the bronchi into bronchioles. In the future, it is planned to improve the apparatus with reference to myocardial contractions. A mobile device is likely to replace a transport ventilator.
The dimensions of the artificial lung are up to 15x15x10 centimeters, they want to bring its dimensions as close as possible to the human organ. The huge area of the gas diffusion membrane gives a 3-5-fold increase in the efficiency of oxygen exchange.
While the device is being tested on pigs, tests have already shown its effectiveness in respiratory failure. The introduction of an artificial lung will help to abandon the more massive transport ventilators that work with explosive oxygen cylinders.
An artificial lung allows activation of a patient otherwise confined to a bed-mounted resuscitator or transport ventilator. And with activation, the chance for recovery and psychological state increase.
Patients awaiting a donor lung transplant usually have to stay in the hospital for quite a long time on an artificial oxygen machine, using which you can only lie in a bed and watch the machine breathe for you.
The project of an artificial lung capable of prosthetic respiratory failure gives these patients a chance for a speedy recovery.
The portable artificial lung kit includes the lung itself and a blood pump. Autonomous work is designed for up to three months. The small size of the device allows it to replace the transport ventilator of emergency medical services.
The work of the lung is based on a portable pump that enriches the blood with air gases.
Some people (especially newborns) do not need long-term high concentration oxygen because of its oxidizing properties.
Another non-standard analogue of mechanical ventilation used for high spinal cord injury is transcutaneous electrical stimulation of the phrenic nerves (“phrenicus stimulation”). A transpleural lung massage according to V.P. Smolnikov was developed - the creation of a state of pulsating pneumothorax in the pleural cavities.
Mohammadhossein Dabaghi et al. \Biomicrofluidics 2018
A group of scientists from Canada and Germany have created external artificial lungs for newborns born with respiratory problems. The new outer lungs are a system of microchannels consisting of double-sided porous membranes that enrich the blood flowing through them with oxygen. Blood flows through such channels on its own, which is a huge plus and helps to avoid many problems associated with external pumps, according to an article in biomicrofluidics.
Respiratory distress syndrome (RDS) occurs in approximately 60 percent of newborns at 28 weeks' gestation, and 15 to 20 percent at 32 to 36 weeks' gestation. However, because the lungs are one of the organs that develop at the end of pregnancy, premature infants with RDS need additional outside help to oxygenate their blood until their own lungs can fully perform their functions on their own. In this case, there are cases when mechanical ventilation of the lungs is not enough, and doctors are forced to enrich the blood with oxygen directly. In such cases, it is necessary to drive the baby's blood through special membrane systems in which the blood is saturated with oxygen.
But, unlike adults, newborns typically don't have more than 400-500 milliliters of blood, so to avoid over-dilution and low hematocrit, it's dangerous to use more than 30-40 milliliters of blood for oxygenation outside the body. This fact limits the time that a unit of blood can spend outside the body, that is, the process of oxygenation must occur fairly quickly. In addition, in order to avoid pressure drops that occur when using a perfusion pump and can damage blood cells, ideally the heart should provide blood movement through the membrane system. And, although this is not critical, it would be good if the membranes could enrich the blood with oxygen using ordinary air for this, and not a specially prepared mixture of gases or pure oxygen.
Scientists tried to meet all these requirements using the concept of an artificial placenta. It involves the exchange of gases between the blood and an external source, without mixing the baby's blood with other fluids (only by adding saline to it to maintain the amount of fluid circulating in the blood vessels). At the same time, since the volume of blood outside the body should not exceed 30 milliliters, it is necessary to create a structure in which, at a fixed volume, the contact area of the blood with the gas exchange membrane is maximum. The easiest way to do this is to fill a box with a very small height with blood, but such a structure will be very unstable. It was the fact that the structure must be thin, but at the same time strong, as well as made of porous materials, that imposed the main restrictions on the creation of artificial lungs.
For efficient gas exchange, scientists placed two square (43 × 43 mm) porous polydimethylsiloxane membranes parallel to each other, placing between them a network of square columns with a side of a millimeter, forming many straight, perpendicular to each other channels through which blood flows. In addition to mechanically holding the membranes, these columns also helped to mix the blood, making it more homogeneous in composition throughout the system. Also, for sufficient stability of the structure, the absence of deformations during operation and the reduction of the influence of defects, one of the membranes must be thick enough to ensure the strength of the structure, but at the same time thin enough so that gas exchange can occur through it. To reduce the thickness of the polydimethylsiloxane layer without losing its mechanical properties, the researchers inserted a network of reinforced steel strips into it.
