Editing Ventilator (section)

== History ==
{{more citations needed section|date=April 2020}}
The history of mechanical ventilation begins with various versions of what was eventually called the [[Negative pressure ventilator|iron lung]], a form of noninvasive negative-pressure ventilator widely used during the [[Poliomyelitis|polio]] epidemics of the twentieth century after the introduction of the "Drinker respirator" in 1928, improvements introduced by [[John Haven Emerson]] in 1931,<ref name="pmid18189086">{{cite journal |last=Geddes |first=LA |year=2007 |title=The history of artificial respiration |journal=IEEE Engineering in Medicine and Biology Magazine |pmid=18189086 |doi=10.1109/EMB.2007.907081 |volume=26 |issue=6 |pages=38–41|s2cid=24784291 }}</ref> and the [[Both respirator]] in 1937. Other forms of noninvasive ventilators, also used widely for polio patients, include [[Biphasic Cuirass Ventilation]], the rocking bed, and rather primitive positive pressure machines.<ref name="pmid18189086" />

In 1949, John Haven Emerson developed a mechanical assister for anaesthesia with the cooperation of the anaesthesia department at [[Harvard University]]. Mechanical ventilators began to be used increasingly in anaesthesia and intensive care during the 1950s. Their development was stimulated both by the need to treat polio patients and the increasing use of [[muscle relaxant]]s during anaesthesia. Relaxant drugs paralyse the patient and improve operating conditions for the surgeon but also paralyse the respiratory muscles. In 1953 [[Bjørn Aage Ibsen]] set up what became the world's first Medical/Surgical ICU utilizing muscle relaxants and controlled ventilation.<ref>{{cite journal 
|author1=P. G. Berthelsen |author2=M. Cronqvist |title=The first intensive care unit in the world: Copenhagen 1953 
|journal=Acta Anaesthesiologica Scandinavica
|year=2003
|volume=47
|issue=10
|pages=1190–1195
|doi=10.1046/j.1399-6576.2003.00256.x|pmid=14616314 |s2cid=40728057 }}</ref>

[[File:East-Radcliffe Respirator Wellcome L0001305.jpg|alt=A machine with hoses and gauges on a wheeled cart|thumb|An East-Radcliffe respirator model from the mid-twentieth century]]
In the United Kingdom, the East Radcliffe and Beaver models were early examples. The former used a [[Sturmey-Archer]] bicycle [[hub gear]] to provide a range of speeds, and the latter an automotive [[windscreen wiper]] motor to drive the bellows used to inflate the lungs.<ref name="pmid13320798">{{cite journal |vauthors=Russell WR, Schuster E, Smith AC, Spalding JM |date=April 1956 |title=Radcliffe respiration pumps |journal=[[The Lancet]] |pmid=13320798 |doi=10.1016/s0140-6736(56)90597-9 |volume=270 |issue=6922 |pages=539–41}}</ref> Electric motors were, however, a problem in the operating theatres of that time, as their use caused an explosion hazard in the presence of flammable anaesthetics such as [[diethyl ether|ether]] and [[cyclopropane]]. In 1952, Roger Manley of the [[Westminster Hospital]], London, developed a ventilator which was entirely gas-driven and became the most popular model used in Europe. It was an elegant design, and became a great favourite with European anaesthetists for four decades, prior to the introduction of models controlled by electronics. It was independent of electrical power and caused no explosion hazard. The original Mark I unit was developed to become the Manley Mark II in collaboration with the Blease company, which manufactured many thousands of these units. Its principle of operation was very simple, an incoming gas flow was used to lift a weighted bellows unit, which fell intermittently under gravity, forcing breathing gases into the patient's lungs. The inflation pressure could be varied by sliding the movable weight on top of the bellows. The volume of gas delivered was adjustable using a curved slider, which restricted bellows excursion. Residual pressure after the completion of expiration was also configurable, using a small weighted arm visible to the lower right of the front panel. This was a robust unit and its availability encouraged the introduction of positive pressure ventilation techniques into mainstream European anesthetic practice.

The 1955 release of [[Forrest Bird]]'s "Bird Universal Medical Respirator" in the United States changed the way mechanical ventilation was performed, with the small green box becoming a familiar piece of medical equipment.<ref name=AboutBird>{{cite web |last=Bellis |first=Mary |title=Forrest Bird invented a fluid control device, respirator & pediatric ventilator |publisher=About.com |url=http://inventors.about.com/od/bstartinventors/a/Forrest_Bird.htm |archive-url=https://archive.today/20130101223131/http://inventors.about.com/od/bstartinventors/a/Forrest_Bird.htm |url-status=dead |archive-date=January 1, 2013 |access-date=2009-06-04 }}</ref> The unit was sold as the Bird Mark 7 Respirator and informally called the "Bird". It was a [[Pneumatics|pneumatic]] device and therefore required no [[electrical power]] source to operate.

In 1965, the Army Emergency Respirator was developed in collaboration with the Harry Diamond Laboratories (now part of the [[United States Army Research Laboratory|U.S. Army Research Laboratory]]) and [[Walter Reed Army Institute of Research]]. Its design incorporated the principle of fluid amplification in order to govern pneumatic functions. Fluid amplification allowed the respirator to be manufactured entirely without moving parts, yet capable of complex resuscitative functions.<ref>{{cite book |date=1965 |title=Army R, D & A. |publisher=Development and Engineering Directorate, HQ, U.S. Army Materiel Development and Readiness Command |url=https://books.google.com/books?id=sTrO77DCgkwC&q=Army+Emergency+Respirator,+HDL&pg=RA6-PA33}}</ref> Elimination of moving parts increased performance reliability and minimized maintenance.<ref name=":0">{{cite journal |last1=Mon |first1=George |last2=Woodward |first2=Kenneth E. |last3=Straub |first3=Henrik |last4=Joyce |first4=James |last5=Meyer |first5=James |date=1966 |title=Fluid Amplifier-Controlled Medical Devices |journal=SAE Transactions |issn=0096-736X |jstor=44554326 |volume=74 |pages=217–222}}</ref> The mask is composed of a [[poly(methyl methacrylate)]] (commercially known as [[Poly(methyl methacrylate)|Lucite]]) block, about the size of a pack of cards, with machined channels and a cemented or screwed-in cover plate.<ref name=":1">{{cite web |title=Army Research and Development Monthly Magazine |volume=6 |number=9 |url=https://asc.army.mil/docs/pubs/alt/archives/1965/Sep_1965.PDF}}</ref> The reduction of moving parts cut manufacturing costs and increased durability.<ref name=":0" />

The bistable fluid amplifier design allowed the respirator to function as both a respiratory assistor and controller. It could functionally transition between assistor and controller automatically, based on the patient's needs.<ref name=":1" /><ref name=":0" /> The dynamic pressure and turbulent jet flow of gas from inhalation to exhalation allowed the respirator to synchronize with the breathing of the patient.<ref>{{cite web |date=October 1965 |title=Fluid Amplification Symposium |volume=III |url=https://apps.dtic.mil/dtic/tr/fulltext/u2/623457.pdf|archive-url=https://web.archive.org/web/20191105192113/https://apps.dtic.mil/dtic/tr/fulltext/u2/623457.pdf|archive-date=November 5, 2019}}</ref>

Intensive care environments around the world revolutionized in 1971 by the introduction of the first SERVO 900 ventilator (Elema-Schönander), constructed by [[Björn Jonson]]. It was a small, silent and effective electronic ventilator, with the famous SERVO feedback system controlling what had been set and regulating delivery. For the first time, the machine could deliver the set volume in volume control ventilation.

===Microprocessor ventilators===
[[Microprocessor control]] led to the third generation of [[intensive care unit]] (ICU) ventilators, starting with the [[Drägerwerk|Dräger]] EV-A<ref>{{cite web |title=Dräger - die Geschichte des Unternehmens |website=Dräger |url=https://www.draeger.com/Corporate/Content/draeger_die_geschichte_des_unternehmens.pdf |access-date=March 22, 2020}}</ref> in 1982 in Germany which allowed monitoring the patient's [[Breathing#Respiratory disorders|breathing curve]] on an [[LCD monitor]]. One year later followed [[Puritan Bennett]] 7200 and Bear 1000, SERVO 300 and Hamilton Veolar over the next decade. [[Microprocessors]] enable customized gas delivery and monitoring, and mechanisms for gas delivery that are much more responsive to patient needs than previous generations of mechanical ventilators.<ref>{{cite journal |last=Kacmarek |first=Robert M. |date=August 2011 |title=The Mechanical Ventilator: Past, Present, and Future |journal=[[Respiratory Care (journal)|Respiratory Care]] |issn=0020-1324 |doi=10.4187/respcare.01420 |volume=56 |issue=8 |pages=1170–1180|pmid=21801579 |doi-access=free }}</ref>
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In 1991, the SERVO 300 ventilator series was introduced, enabling treatment of all patient categories from adult to neonate with one ventilator. The SERVO 300 series had a unique gas delivery system with rapid flow-triggering response.

In 1999, the new LTV (Laptop Ventilator) Series was significantly smaller than other ventilators of the time, weighing approximately 6.4 kg (14 lb) and about the size of a laptop computer. This design kept the same functionality of the in-hospital ventilators while allowing patient mobility.

A modular concept was introduced with SERVO-i in 2001, with one ventilator model throughout the ICU department, instead of a fleet of various models and brands for different user needs. With the modular ventilator, ICU departments could choose the modes and options, software and hardware needed for a particular patient category.

In the twenty-first century small portable ventilators like the SAVe II have been manufactured for forward combat use.<ref name=Automedx>{{cite web |title=SAVe II The Smallest and Easiest to Use Pre-hospital Ventilator |publisher=Automedx |website=Automedx |url=http://automedx.com/save-ii/ |access-date=March 31, 2019}}</ref>-->