A ventilator or respirator is an electrically, nowadays controlled by microcontrollers , electromagnetically or pneumatically driven machine for the ventilation of people with insufficient or suspended self-breathing . The breathing gas is usually enriched with oxygen .
In 1907, George Poe (1846-1914), a cousin of the American writer Edgar Allan Poe , filed for US Patent 859778 on a Machine for inducing artificial respiration . While previous respirators purely according to the principle of the bellows worked ventilator, 1980s have become increasingly at the beginning, starting with the ventilator EV-A , microprocessors used the Draeger for controlling the respiratory gas flow (also for automatic compensation of leakage) and the function of the bellows replaced by valves with electromagnetic actuation (instead of the previous pneumatic or electrically operated mechanism).
Depending on the area of application, a distinction is made between emergency, intensive and home ventilators. Even anesthesia machines are specialized ventilators. Since around 1970 the number of possible ventilation methods (originally only one) and additional functions (originally only the “sigh”, then an adjustable oxygen concentration and pressure limitation) has increased continuously.
When ventilating newborns and infants, special ventilators are used, which above all protect against excessive airway pressures. The first ventilator for small children was the so-called “Baby Pulmotor ” from Drägerwerke , from which the Babylog 1 series of respirators developed in 1975 . The first ventilators specifically for newborns were developed in the late 1980s. The first ventilator designed exclusively for small children and premature babies was the Babylog 8000 , which was introduced in 1989 and operated with digitally controlled valves and precise flow measurement , with which premature babies could for the first time be gently ventilated in a volume-oriented manner.
To avoid endangering the patient, ventilation monitoring with monitoring of the settings is required during use, which generally includes the following aspects:
- Properties of the breathing gas such as
- Inspiratory oxygen concentration (e.g. FiO 2 = 0.5 to 0.8)
- Gas exchange, in particular
- Ventilation pressure
- Peak pressure
- Plateau pressure
- Medium pressure
- PEEP , e.g. B. 5 cm water column.
The degrees of freedom resulting from the setting parameters (pressure, volume, flow, expiratory pause time, etc.) of a respirator (parameters, the size of which results from the selected settings depending on the lung condition) can be:
- Tidal volume (with pressure control and constant pressure time control)
- Minute ventilation (with pressure control, constant pressure time control and volume control)
- Airway pressure (with volume control and volume-constant time control)
- Respiratory rate (with pressure control and volume control)
- Breathing time ratio (with pressure control and volume control), e.g. B. I: E ratio = 1: 2
- Plateau duration (with constant volume time control), e.g. B. Plateau ("Hold") = 0.5 s.
Types of ventilators
Emergency respirators (transport ventilators)
Emergency respirators, synonymous with transport respirators, are used in the rescue service and are therefore designed to be robust, portable and compact and have a pneumatic (operated by oxygen gas cylinders or with ambient air via a breathing gas compressor) or battery-operated (electronically controlled) mechanics. They are also used in intensive care medicine for intra-hospital transports of ventilated patients, for example to the operating theater or for X-ray examinations. Parameters such as the oxygen concentration or the breathing time ratio can be set. The first transport and emergency ventilators were only equipped with the option of purely controlled ventilation and a manometer for measuring airway pressure. Modern emergency respirators (e.g. Oxylog 3000 (from Dräger ), Medumat Transport ) have a variety of (pressure and volume-controlled) ventilation modes (e.g. also BIPAP), so that even in the preclinical area during the transport and care of intensive care patients requiring ventilation Ventilation options are available.
Intensive care respirators are used for longer and differentiated ventilation therapies under intensive care conditions. In principle, all forms of ventilation, including the less common high-frequency ventilation , are possible. They have numerous measurement, documentation and alarm options, can be better adapted to the patient or the clinical picture and can be connected to a network .
Only with these devices is weaning , i.e. the slow reduction of the respiratory support provided by the device as the patient breathes more and more, and thus weaning from the device, since ventilation patterns (in ventilation technology, the temporal progressions of pressure and volume) are used Enable self-breathing at any time and also support it, depending on the setting of the device. These are mostly pressure-controlled forms of ventilation such as BIPAP ventilation with recognition of the patient's independent efforts to inhale and their enabling. The additional function of automatic tube compensation makes it possible, for example, to reduce the patient's breathing effort so that he or she has the feeling that he is not intubated.
Home ventilation devices are used for patients whose natural breathing is severely reduced due to temporary or permanent disorders of the nervous system or respiratory muscles, but who are discharged from the clinic anyway. Home ventilators are small in size so that they can be easily accommodated in the patient's home. Mobility is also little restricted by such small respirators, since the patients can carry them with them even when they are battery operated. Since there are usually no wall connections for oxygen or compressed air in private apartments or nursing homes , such respirators are manufactured in such a way that they are independent of them. Home ventilation devices are also easier to use, so that patients or their relatives can easily familiarize themselves with the technology and make the necessary settings themselves.
The iron lung was the first device for mechanical ventilation. An iron lung does not work like modern respirators, but the patient lies up to his neck in the device and is hermetically enclosed by it. When a negative pressure is created in the chamber, the chest expands and ambient air flows through the airways into the lungs.
Even today, in rare cases, and almost exclusively for home ventilation, negative pressure respirators, such as the cuirass ventilator, are used . These consist of a hard plastic shell that can also be made to measure in the case of chest deformities. In modern clinical intensive care medicine, tank respirators are no longer used, since the underlying diseases are usually associated with an increase in the mechanical work of breathing (which can be read and calculated from pressure-volume diagrams), which cannot be compensated for.
With every respirator there is the possibility of a device failure, so that a ventilated patient should be close to a resuscitator so that the patient can continue to ventilate even if the respirator fails. The failure of the respirator must also be able to be recognized by oxygen monitoring.
In addition, when a patient is transferred with a ventilator, it must be ensured that the supplies in the oxygen bottles are sufficient and thus enable uninterrupted ventilation. Electrically operated emergency respirators have a rechargeable battery and an external charger, intensive respirators often only have a rechargeable battery that enables an alarm in the event of a power failure. However, for critical cases of patient transport, devices with accumulators are also available, which guarantee network-independent operation for a certain period of time. The accumulators and power supply units are also built redundantly in some systems.
Legislation and standards (Germany, Austria)
As medical products , ventilators are subject to the German and Austrian medical product laws and the associated operator regulations , which, as implementation of the EEC directive 93/42, ensure standardization within the EU and, depending on the type, the standards EN 60601-2-12 and EN 60601-1- 8 , which is intended to ensure safety for users and patients. Ventilators as active medical devices may only be used by persons who are qualified for this and who have been instructed in the use of the respective device type. In addition, they may only be manufactured by qualified personnel and developed and produced in compliance with standards.
In the course of the COVID-19 pandemic , the demand for ventilators skyrocketed . The German federal government ordered 10,000 ventilators, the United States authorities issued an inquiry for 100,000 devices.
Open source and open hardware initiatives
In addition, since spring 2020, several joint projects have been created with the approach of providing an open design for a simple ventilator. It should be possible to produce such devices quickly in a simple way.
- Open source fan initiative
- The DIY ventilator project as part of the German government's # WirVsVirus hackathon
- The Oxysphere project is developing open construction plans for a ventilation bell.
- Further projects are listed on the website of the Open Source Ventilator Initiative .
At the initiative of the University of Minnesota Bakken Medical Device Center , a collaboration was started with various companies to bring a ventilator alternative to the market that works as a one-armed robot and replaces the need for manual ventilation in emergency situations. The device called Coventor was developed in a very short time and approved by the US health authority FDA just 30 days after conception . The mechanical ventilator is easy to use for trained medical professionals in intensive care units . The costs are only about 4% of a fully functional normal ventilator. In addition, this device does not require any pressurized oxygen or air supply as is normally the case. A first series is produced by Boston Scientific .
- SP Stawicki et al .: Analytic Reviews: High-Frequency Oscillatory (HFOV) and Airway Pressure Release Ventilation (APRV): A Practical Guide . In: Journal of Intensive Care Medicine. Volume 24, 2009.
- W. Oczenski et al. (2006): Breathing-Respiratory Aids : Breathing Physiology and Ventilation Technology . Thieme Verlag, 7th edition: 497–498.
- S. Derdak, S. Mehta et al. (2002): High-frequency oscillatory ventilation for acute respiratory distress syndrome in adults: a randomized, controlled trial. Am J Respir Crit Care Med 166 (6): 801-808.
- Y. Imai, S. Nakagawa, et al. (2001): Comparison of lung protection strategies using conventional and high-frequency oscillatory ventilation. In: J Appl Physiol . 91 (4): 1836-1844.
- S. Metha, SE Lapinsky et al. (2001): Prospective trial of high-frequency oscillation in adults with acute respiratory distress syndrome. Crit Care Med 29 (7): 1360-1369.
- P. Fort, C. Farmer, et al. (1997): High-frequency oscillatory ventilation for adult respiratory distress syndrome - a pilot study. Crit Care Med 25 (6): 937-947.
- H. Benzer: Therapy of respiratory failure. In: J. Kilian, H. Benzer, FW Ahnefeld (ed.): Basic principles of ventilation. Springer, Berlin a. a. 1991, ISBN 3-540-53078-9 , 2nd, unchanged edition, ibid 1994, ISBN 3-540-57904-4 , pp. 215-278; here: pp. 222–268.
- Machine for inducing artificial respiration. October 11, 1906 ( google.com [accessed April 29, 2020]).
- Dr. Poe and His Curious Breathing Machine. Retrieved April 29, 2020 .
- Ernst Bahns: It all started with the Pulmotor. The history of mechanical ventilation. Drägerwerk, Lübeck 2014, p. 66 f. ( New ventilation technology with EV-A ).
- Ernst Bahns: It all started with the Pulmotor. The history of mechanical ventilation. Drägerwerk, Lübeck 2014, p. 98 f.
- Ernst Bahns: It all started with the Pulmotor. The history of mechanical ventilation. Drägerwerk, Lübeck 2014, pp. 48–51.
- Dirk Weismann: Forms of ventilation. In: J. Kilian, H. Benzer, FW Ahnefeld (ed.): Basic principles of ventilation. Springer, Berlin a. a. 1991, ISBN 3-540-53078-9 , 2nd, unchanged edition, ibid. 1994, ISBN 3-540-57904-4 , pp. 201-211; here: pp. 209–211 ( ventilation monitoring ).
- M. Baum: Technical basics of ventilation. In: J. Kilian, H. Benzer, FW Ahnefeld (ed.): Basic principles of ventilation. Springer, Berlin a. a. 1991, ISBN 3-540-53078-9 , 2nd, unchanged edition, ibid. 1994, ISBN 3-540-57904-4 , pp. 185-200; here: pp. 189–198.
- Example: Savina ventilator from Dräger
- Ernst Bahns: It all started with the Pulmotor. The history of mechanical ventilation. 2014, p. 44 f.
- Ernst Bahns: It all started with the Pulmotor. The history of mechanical ventilation. Drägerwerk, Lübeck 2014, p. 54 f. ( The Oxylog Family - The Path to Modern Emergency Ventilation ).
- Oxylog 3000 plus. Dräger , accessed on February 23, 2015 .
- Walied Abdulla: Interdisciplinary Intensive Care Medicine. Urban & Fischer, Munich a. a. 1999, ISBN 3-437-41410-0 , p. 12 ( transport ventilators ).
- Ernst Bahns (2014), p. 58 f. ( The ventilator in clinical use ).
- Thomas Pasch, S. Krayer, HR Brunner: Definition and parameters of acute respiratory insufficiency: ventilation, gas exchange, respiratory mechanics. In: J. Kilian, H. Benzer, FW Ahnefeld (ed.): Basic principles of ventilation. Springer, Berlin a. a. 1991, ISBN 3-540-53078-9 , 2nd, unchanged edition, ibid 1994, ISBN 3-540-57904-4 , pp. 95-108; here: p. 102 ff.
- Dietmar Kirchberg: The Medical Devices Act: what nurses need to know; Regulations, examples, consequences . Schlütersche Verlagsanstalt, 2003, ISBN 978-3-87706-878-6 , p. 58 ff . ( limited preview in Google Book search).
- Lukas Eberle, Martin U. Müller: "An absolute mission impossible" . In: Der Spiegel . No. 14 , 2020, p. 48 f . ( online - March 28, 2020 ).
- Open Source Ventilator initiatives and more. Website of the Open Source Ventilator initiative. Accessed March 29
- WirVsVirus: Self-made ventilator Article on heise.de. Retrieved on March 29th
- Oxysphere - OpenHardware Ventilation Project - Let us Stop Covid together. Retrieved March 31, 2020 (American English).
- List of various projects for the manufacture of a ventilator. Website of the Open Source Ventilator initiative. Accessed March 29
- Joe Carlson: FDA approves production of device designed at University of Minnesota to help COVID-19 patients breathe. In: https://www.startribune.com/ . Star Tribune, April 16, 2020, accessed April 16, 2020 .
- Darrell Etherington: FDA authorizes production of a new ventilator that costs up to 25x less than existing devices. In: https://techcrunch.com/ . Verizon Media, April 16, 2020, accessed April 16, 2020 .