This article delves into the intricacies of a specific type of machine designed to assist respiration: the ventilator. It's crucial to distinguish this from the broader category of mechanical ventilation, which encompasses both positive- and negative-pressure devices. Furthermore, the term "respirator" can be confusing; while it was once commonly used for ventilators, it now typically refers to respiratory personal protective equipment (PPE) worn to shield individuals from hazardous airborne substances. For a comprehensive understanding of ventilation in all its facets, consult the Ventilation disambiguation page. And if you're searching for other meanings of "ventilator," the Ventilator (disambiguation) page is your destination.
Ventilator
Specialty: Pulmonology [edit on Wikidata]
A ventilator, in essence, is a sophisticated piece of medical technology that operates as a breathing apparatus. Its primary function is to provide mechanical ventilation, a process involving the controlled movement of breathable air into and out of a patient's lungs. This intervention is critical for individuals who are unable to breathe adequately on their own, either due to a complete inability to respire or insufficient respiratory effort. While many modern ventilators are intricately computerized and microprocessor-controlled systems, the fundamental principle can also be achieved with simpler, manual devices like a bag valve mask. These life-sustaining machines find their primary applications in critical care settings such as intensive-care medicine, home care, and emergency medicine, often as standalone units. In the realm of surgery, they are integrated components of an anesthesia machine.
The term "respirator" often causes conflation. While it was a common descriptor for ventilators back in the 1950s, particularly referencing devices like the "Bird respirator", its contemporary usage is distinct. Today, "respirator" generally denotes a protective mask designed to prevent the inhalation of harmful airborne particles.
Function
At its most rudimentary, a modern positive pressure ventilator comprises several key components: a mechanism to deliver air (either a compressible reservoir or a turbine), sources for both air and oxygen, a system of valves and tubing, and a patient circuit, which can be disposable or reusable. The air delivery system, whether it's a compressible reservoir or a turbine, cycles multiple times per minute, pushing room air or, more commonly, a carefully calibrated mixture of air and oxygen into the patient's lungs. In the case of a turbine, it actively propels air through the device, with a flow valve precisely regulating the pressure to match the patient's specific requirements. Once the delivery pressure is released, the patient exhales passively, a process facilitated by the inherent elasticity of their lungs. The exhaled air is then typically directed away from the patient through a one-way valve integrated into the patient circuit, often referred to as the patient manifold.
More advanced ventilators are equipped with comprehensive monitoring and alarm systems. These systems track crucial patient parameters such as pressure, volume, and flow rates, as well as the operational status of the ventilator itself, including any air leaks, power failures, or mechanical malfunctions. They may also incorporate backup power sources like batteries, dedicated oxygen tanks, and even remote control capabilities. The pneumatic systems of older models have largely been supplanted by computer-controlled turbopumps in contemporary designs.
The intricate control of modern ventilators is managed by embedded embedded systems. This allows for highly precise adjustments to pressure and flow characteristics, tailoring the ventilation to the unique needs of each patient. These finely tuned settings not only ensure adequate gas exchange but also contribute significantly to the patient's comfort and tolerance of the mechanical support. In North America, respiratory therapists are typically responsible for fine-tuning these settings, while biomedical technologists handle the maintenance. In the United Kingdom and other parts of Europe, the management of patient-ventilator interaction falls under the purview of critical care nurses.
The patient circuit itself is usually composed of a set of three durable yet lightweight plastic tubes, each designated for a specific function: delivering inhaled air, monitoring patient pressure, and managing exhaled air. Depending on the required level of respiratory support, the interface between the circuit and the patient can be either noninvasive or invasive.
Noninvasive ventilation methods, such as continuous positive airway pressure (CPAP) and other forms of non-invasive ventilation, are often sufficient for patients who only require ventilator support during sleep or periods of rest. These methods typically utilize a nasal mask. Invasive ventilation, conversely, necessitates intubation. For patients requiring long-term ventilator dependence, a tracheotomy cannula is the preferred method, offering significantly greater comfort and practicality compared to laryngeal or nasal intubation.
There are two primary classifications of ventilator systems based on their operational circuits:
- Closed-circuit ventilator systems: These are designed to deliver oxygen-enriched air to the patient, precisely controlling the gas mixture.
- Open-circuit ventilators: These systems are employed to deliver normal ambient air, maintaining the standard oxygen ratio found in the Earth's atmosphere.
At a fundamental physiological level, ventilators play a crucial role in renewing the air within the pulmonary alveolus, ensuring the critical exchange of oxygen and carbon dioxide necessary for life.
Safety-Critical System
Given that a failure in mechanical ventilation can have fatal consequences, these systems are unequivocally classified as safety-critical systems. This designation mandates rigorous design principles and extensive precautions to ensure their utmost reliability, including the integrity of their power supply. Ventilatory failure itself is defined as the inability of the respiratory system to maintain an adequate rate of carbon dioxide elimination, thereby preventing a stable blood pH without the assistance of mechanical intervention, or leading to intolerable muscle fatigue or dyspnea. Consequently, mechanical ventilators are engineered to eliminate any single point of failure that could jeopardize patient safety. Many incorporate manual backup mechanisms, such as the integrated ventilator found in an anaesthetic machine, which allows for hand-driven respiration in the event of power loss. Additionally, safety valves are often included; these open to the atmosphere if power fails, functioning as an anti-suffocation mechanism to permit spontaneous breathing. Some systems are further fortified with compressed gas tanks, air compressors, or backup batteries to guarantee continued ventilation during power outages or failures in the primary gas supply. Provisions are also made for operators to summon assistance should the device's mechanisms or software encounter issues. Power failures, particularly those occurring during natural disasters, can escalate into life-threatening emergencies for individuals reliant on ventilators in a home care setting. While battery backup may offer temporary respite, prolonged outages necessitate relocation to a hospital environment.
History
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The genesis of mechanical ventilation traces back to various iterations of what became known as the iron lung. This type of noninvasive negative-pressure ventilator saw widespread use during the polio epidemics of the 20th century. Key developments include the introduction of the "Drinker respirator" in 1928, followed by improvements by John Haven Emerson in 1931, and the Both respirator in 1937. Other noninvasive ventilators, also instrumental in treating polio patients, included Biphasic Cuirass Ventilation, the rocking bed, and rudimentary positive pressure machines.
In 1949, John Haven Emerson collaborated with the anesthesia department at Harvard University to develop a mechanical assister for anesthesia. The 1950s witnessed an increasing adoption of mechanical ventilators in anesthesia and intensive care. This surge in development was driven by the dual needs of treating polio patients and the growing use of muscle relaxants during anesthesia. Muscle relaxants, while improving surgical conditions by paralyzing the patient, also impair respiratory muscle function, necessitating mechanical support. In 1953, Bjørn Aage Ibsen established what is recognized as the world's first Medical/Surgical Intensive Care Unit (ICU), specifically designed for patients managed with muscle relaxants and controlled ventilation.
An example of an East-Radcliffe respirator from the mid-20th century is depicted. In the United Kingdom, early models included the East Radcliffe and Beaver respirators. The East Radcliffe ingeniously employed a Sturmey-Archer bicycle hub gear to offer a range of operational speeds, while the Beaver utilized an automotive windscreen wiper motor to drive its bellows for lung inflation. However, electric motors posed a significant explosion risk in operating theaters of that era due to the presence of flammable anesthetics like ether and cyclopropane.
In 1952, Roger Manley, working at Westminster Hospital in London, engineered a ventilator that operated entirely on gas power, quickly becoming the most prevalent model in Europe. This elegant design remained a favorite among European anesthetists for four decades, predating the widespread adoption of electronic controls. Its gas-driven nature eliminated explosion hazards and reliance on electrical power. The original Mark I unit evolved into the Manley Mark II through collaboration with the Blease company, which manufactured thousands of these devices. Its operational principle was straightforward: an incoming gas flow lifted a weighted bellows unit, which then descended under gravity, intermittently forcing breathing gases into the patient's lungs. The inflation pressure could be adjusted by repositioning the movable weight on the bellows, and the delivered volume was controlled via a curved slider that limited the bellows' excursion. The residual pressure at the end of expiration was also configurable using a small weighted arm visible on the front panel. This robust unit played a pivotal role in integrating positive pressure ventilation techniques into mainstream European anesthetic practice.
The introduction of Forrest Bird's "Bird Universal Medical Respirator" in the United States in 1955 revolutionized mechanical ventilation. The distinctive small green box became a ubiquitous sight in medical facilities. Known as the Bird Mark 7 Respirator, and informally called the "Bird," this pneumatic device did not require an electrical power source to function.
In 1965, the Army Emergency Respirator was developed through a joint effort involving the Harry Diamond Laboratories (now part of the U.S. Army Research Laboratory) and the Walter Reed Army Institute of Research. Its design incorporated the principle of fluid amplification to manage pneumatic functions. This allowed for the construction of the respirator entirely without moving parts, yet it was capable of complex resuscitation functions. The elimination of moving parts significantly enhanced performance reliability and reduced maintenance requirements. The mask itself was crafted from a poly(methyl methacrylate) (commonly known as Lucite) block, roughly the size of a deck of cards, featuring machined channels and a secured cover plate. This reduction in moving parts not only lowered manufacturing costs but also increased the device's durability.
The bistable fluid amplifier design enabled the respirator to function as both a respiratory assistor and controller, dynamically adapting to the patient's needs without manual intervention. The interplay of dynamic pressure and turbulent jet flow during inhalation and exhalation allowed the respirator to synchronize with the patient's breathing patterns.
The landscape of intensive care units worldwide underwent a significant transformation in 1971 with the unveiling of the first SERVO 900 ventilator by Elema-Schönander. This compact, quiet, and highly effective electronic ventilator featured the renowned SERVO feedback system, which meticulously controlled and regulated gas delivery based on pre-set parameters. This marked a pivotal moment, as it was the first time a machine could reliably deliver the set tidal volume in volume control ventilation mode.
Microprocessor Ventilators
The advent of microprocessor control ushered in the third generation of intensive care unit (ICU) ventilators. The Dräger EV-A, released in Germany in 1982, was a pioneering example, offering the capability to display the patient's breathing curve on an LCD monitor. This was followed by the Puritan Bennett 7200 and Bear 1000, and the SERVO 300 and Hamilton Veolar, in the subsequent decade. Microprocessors enabled highly customized gas delivery and sophisticated monitoring, along with gas delivery mechanisms that responded with unprecedented accuracy to patient demands, surpassing previous generations of mechanical ventilators.
Open-Source Ventilators
An open-source ventilator represents a specific type of ventilator designed for disaster situations, utilizing freely licensed blueprints and, ideally, components and parts that are readily accessible. The designs can range from complete reverse-engineering of existing devices to entirely novel creations. Components might be adapted from inexpensive, off-the-shelf products, or critical, hard-to-find parts can be fabricated using 3D printing rather than being sourced conventionally.
During the global COVID-19 pandemic that began in 2019–2020, a variety of ventilators came under consideration. Severe cases of COVID-19 often lead to acute respiratory distress syndrome, a severe lung inflammation that compromises the body's ability to absorb oxygen and expel carbon dioxide. Patients in such critical condition require the support of a capable ventilator to maintain respiration.
The deployment of ventilators to combat COVID-19 presented numerous challenges. These included concerns about current availability, the logistical complexities of manufacturing increased numbers of ventilators at lower costs, their efficacy, functional design, safety protocols, portability, suitability for pediatric patients, the potential diversion of ventilators from other medical needs, and the requisite operator training. Optimizing the mix of available ventilators was seen as crucial to maximizing life-saving potential.
While not formally designated as open-source, the Ventec V+ Pro ventilator, developed in April 2020 through a collaborative effort between Ventec Life Systems and General Motors, aimed to rapidly supply 30,000 ventilators for treating COVID-19 patients.
A significant global design initiative emerged during the 2019-2020 coronavirus pandemic following the launch of a Hackaday project, intended as a response to the anticipated ventilator shortages that could lead to higher mortality rates among severely ill patients. (Note: This specific citation lacks primary sourcing and is marked as non-primary source needed).
On March 20, 2020, the Irish Health Service began evaluating various designs. A prototype was under development and testing in Colombia.
The Polish company Urbicum reported successful testing of a 3D-printed, open-source prototype device named VentilAid. The creators describe it as a device of last resort, intended for situations where professional equipment is unavailable. The design is publicly accessible. The initial VentilAid prototype requires compressed air for operation.
On March 21, 2020, the New England Complex Systems Institute (NECSI) commenced the maintenance of a curated list of ongoing open-source ventilator designs. The NECSI project evaluates designs based on manufacturing feasibility, medical safety, suitability for diverse patient conditions, the speed of navigating legal and political hurdles, and logistical and supply chain considerations. NECSI's team comprises scientists from institutions like Harvard and MIT, bringing expertise in pandemics, medicine, systems analysis, risk assessment, and data collection.
The University of Minnesota Bakken Medical Device Center initiated a collaboration with several companies to bring an alternative ventilator to market. This device, functioning as a one-armed robot, was designed to replace manual ventilation in emergency scenarios. Developed with remarkable speed, the Coventor device received emergency use authorization from the FDA on April 15, 2020, a mere 30 days after its conception. This mechanical ventilator is intended for operation by trained medical professionals in intensive care units and is designed for ease of use. Its compact structure and relatively low manufacturing cost make it an economical option for distribution. The estimated cost is approximately 4% of a standard ventilator. Notably, this device does not require pressurized oxygen or air supply, a common requirement for traditional ventilators. An initial production run is being undertaken by Boston Scientific, with plans to make the design freely available online to the public without royalty fees.
COVID-19 Pandemic
The COVID-19 pandemic triggered widespread shortages of essential goods and services, extending from hand sanitizers and masks to hospital beds and, critically, ventilators. Countries globally experienced significant deficits in ventilator availability. Compounding these shortages, fifty-four governments, including many in Europe and Asia, imposed restrictions on the export of medical supplies in response to the pandemic.
The capacity to produce and distribute both invasive and non-invasive ventilators varies considerably among nations. In the initial stages of the pandemic, China significantly ramped up its ventilator production, secured substantial donations from private entities, and dramatically increased imports of medical devices. This led to the accumulation of a substantial ventilator reserve within the country, particularly in Wuhan. Western Europe and the United States, despite possessing greater production capabilities than China, faced shortages due to the sudden and widespread nature of outbreaks across North America and Europe. Meanwhile, Central Asia, Africa, and Latin America, heavily reliant on imported ventilators, endured severe supply shortages.
Healthcare policymakers encountered considerable difficulties in accurately estimating the number of ventilators required and utilized during the pandemic. In instances where specific ventilator data was scarce, estimates were often derived from the number of intensive care unit beds available, as these are typically equipped with ventilators.
United States
In 2006, President George W. Bush signed the Pandemic and All-Hazards Preparedness Act, which established the Biomedical Advanced Research and Development Authority (BARDA) within the United States Department of Health and Human Services. In anticipation of a potential respiratory disease epidemic, BARDA awarded a 3,000 each. In 2011, Newport delivered three prototypes to the Centers for Disease Control. In 2012, Covidien, a major medical device manufacturer with annual revenues of 100 million. Covidien subsequently delayed, and ultimately cancelled, the contract in 2014.
BARDA initiated a new contract with Philips. In July 2019, the FDA approved the Philips ventilator, and the government placed an order for 10,000 units, scheduled for delivery in mid-2020.
On April 23, 2020, NASA announced the successful development of a COVID-19 ventilator, named VITAL ("Ventilator Intervention Technology Accessible Locally"), in just 37 days. On April 30, NASA reported receiving expedited emergency use authorization from the United States Food and Drug Administration for the new ventilator. On May 29, NASA confirmed the selection of eight manufacturers tasked with producing the VITAL ventilator.
Canada
On April 7, 2020, Prime Minister Justin Trudeau announced that the Canadian Federal Government would procure thousands of "Made in Canada" ventilators. Numerous organizations across the country responded to this initiative, ultimately delivering a substantial quantity of ventilators to the National Emergency Strategic Stockpile. These companies, from west to east, included Canadian Emergency Ventilators Inc, Bayliss Medical Inc, Thornhill Medical, Vexos Inc, and CAE Inc.