Negative pressure ventilator

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A negative pressure ventilator (NPV) is a type of mechanical ventilator that stimulates an ill person's breathing by periodically applying negative air pressure to their body to expand and contract the chest cavity. [1] [2] [3] [4] [5] [6]

Contents

Description

Iron lung cylinder (black), patient head exposed through sealed opening. Diaphragm (yellow) mechanically extends, and then retracts, varying cylinder air pressure and causing the patient's chest to expand (top), and then contract (bottom) Iron lung action diagrams.png
Iron lung cylinder (black), patient head exposed through sealed opening. Diaphragm (yellow) mechanically extends, and then retracts, varying cylinder air pressure and causing the patient's chest to expand (top), and then contract (bottom)

In most NPVs (such as the iron lung in the diagram), the negative pressure is applied to the patient's torso, or entire body below the neck, to cause their chest to expand, expanding their lungs, drawing air into the patient's lungs through their airway, assisting (or forcing) inhalation. When negative pressure is released, the chest naturally contracts, compressing the lungs, causing exhalation. In some cases, positive external pressure may be applied to the torso to further stimulate exhalation. [1] [2] [3] [4] [5] [6]

Another form of NPV device (such as the Pulmotor) is placed at the patient's airway, and alternates negative pressure with positive pressure to pump air into their lungs (inhale under positive pressure), then suck it back out (exhale under negative pressure). [2] [7] [8] [9] [10]

Usage

Negative pressure ventilators, while widely used in the early-to-mid 20th century (particularly for victims of the polio epidemics), are now largely replaced by positive-pressure airway ventilators, which force air (or oxygen) directly into the patient's airway. [1] [2] [3] [4] [5] However, researchers and clinicians still find some uses for NPVs, owing to their specific advantages. [1] [2]

Research and developments in artificial ventilation, both negative-pressure and positive-pressure, result in evolving assessments of the benefits and hazards of negative-pressure ventilators (NPVs). Different researchers and clinicians have made varying assessments, over time, about the primary positive and negative aspects of NPVs. A sampling includes:

Advantages

Generally, NPVs are best with patients who have neuromuscular diseases, but normal lung compliance (a measure of the lungs' ability to expand and contract). [2] They are effective for various conditions, especially neuromuscular and skeletal disorders, particularly for long-term night-time ventilation. [1] They are effective in patients who have severe respiratory acidosis, impaired consciousness, are unable to tolerate a facial mask (due to facial deformity, or claustrophobia, or excess airway secretions), and in children. [11] Continuous external negative pressure ventilation (CENPV) was found in a 2015 study to "[improve] oxygenation under [a greater number of] physiological conditions", concurrent with lower "airway," "transpulmonary," and "intra-abdominal" pressures, than experienced with continuous positive pressure ventilation (CPPV), in study of adult respiratory distress syndrome (ARDS) patients, possibly reducing high ARDS mortality. [12]

Disadvantages

NPVs do not work well if patient's lung compliance is decreased, or their lung resistance is increased. [2] They result in a greater vulnerability of the airway to aspiration, such as inhalation of vomit or swallowed liquids, than with intermittent positive pressure ventilation. [1] They exacerbate obstructive sleep apnea. The device is not portable and its installation may be difficult. Patients must sleep in a supine position. [13]

Types of NPVs

There are several types of NPVs, including: [1] [2] [3] [4] [5]

Iron lung

The iron lung, also known as the tank ventilator, Drinker tank or Emerson tank, was the first common pure-NPV device when it was developed in the 1920s by Drinker, Shaw and Mason. It is a large, sealed horizontal cylinder (or "tank") in which the patient lies, with their head protruding from a sealed opening at one end of the tank. An air pump or a flexible diaphragm (usually motor-driven) varies the air pressure inside the tank, in continuous alternations, lowering and raising the air pressure in the cylinder. This causes the patient's chest to rise and fall, stimulating inhalation and exhalation through the patient's nose and mouth (which are outside the cylinder, exposed to ambient air pressure). [1] [2] [3] [4] [6]

Cuirass ventilator

The cuirass ventilator, also known as the chest shell, turtle shell or tortoise shell, is a more compact variation of the iron lung which only encloses the patient's torso and is sealed around their neck and waist, and depressurized and repressurized by an external pump or portable ventilator. [1] [2] [3] [4] [16]

Exovent

The exovent is a modern device similar to the cuirass ventilator, but developed in 2020, in response to the COVID-19 pandemic. [14] [15]

Jacket ventilator

The jacket ventilator, also known as a poncho or raincoat ventilator, is a lighter version of the iron lung or the cuirass ventilator, constructed of an airtight material (such as plastic or rubber) arranged over a light metal or plastic frame, or screen, and depressurized and repressurized by a portable ventilator. [1] [2] [12] [17]

Positive-and-negative pressure ventilator

Pulmotor

The Pulmotor is a device developed in the early 1900s which was the forerunner of modern mechanical ventilators. It used pressure from a tank of compressed oxygen to operate a valve system that alternately forced air into and out of a person's airway, using alternating positive and negative air pressure. Although portable, and able to be used by lay persons and non-medical emergency responders, some medical personnel criticized it as dangerous (in part due to the risks of barotrauma or vomiting) and inefficient. [7] [8] [9] [10] [16]

Related Research Articles

<span class="mw-page-title-main">Ventilator</span> Device that provides mechanical ventilation to the lungs

A ventilator is a type of breathing apparatus, a class of medical technology that provides mechanical ventilation by moving breathable air into and out of the lungs, to deliver breaths to a patient who is physically unable to breathe, or breathing insufficiently. Ventilators may be computerized microprocessor-controlled machines, but patients can also be ventilated with a simple, hand-operated bag valve mask. Ventilators are chiefly used in intensive-care medicine, home care, and emergency medicine and in anesthesiology.

<span class="mw-page-title-main">Mechanical ventilation</span> Method to mechanically assist or replace spontaneous breathing

Mechanical ventilation or assisted ventilation is the medical term for using a ventilator machine to fully or partially provide artificial ventilation. Mechanical ventilation helps move air into and out of the lungs, with the main goal of helping the delivery of oxygen and removal of carbon dioxide. Mechanical ventilation is used for many reasons, including to protect the airway due to mechanical or neurologic cause, to ensure adequate oxygenation, or to remove excess carbon dioxide from the lungs. Various healthcare providers are involved with the use of mechanical ventilation and people who require ventilators are typically monitored in an intensive care unit.

<span class="mw-page-title-main">Iron lung</span> Negative-pressure mechanically functioning respirator

An iron lung is a type of negative pressure ventilator, a mechanical respirator which encloses most of a person's body and varies the air pressure in the enclosed space to stimulate breathing. It assists breathing when muscle control is lost, or the work of breathing exceeds the person's ability. Need for this treatment may result from diseases including polio and botulism and certain poisons.

<span class="mw-page-title-main">Positive airway pressure</span> Mechanical ventilation in which airway pressure is always above atmospheric pressure

Positive airway pressure (PAP) is a mode of respiratory ventilation used in the treatment of sleep apnea. PAP ventilation is also commonly used for those who are critically ill in hospital with respiratory failure, in newborn infants (neonates), and for the prevention and treatment of atelectasis in patients with difficulty taking deep breaths. In these patients, PAP ventilation can prevent the need for tracheal intubation, or allow earlier extubation. Sometimes patients with neuromuscular diseases use this variety of ventilation as well. CPAP is an acronym for "continuous positive airway pressure", which was developed by Dr. George Gregory and colleagues in the neonatal intensive care unit at the University of California, San Francisco. A variation of the PAP system was developed by Professor Colin Sullivan at Royal Prince Alfred Hospital in Sydney, Australia, in 1981.

<span class="mw-page-title-main">Respiratory arrest</span> Medical condition

Respiratory arrest is a serious medical condition caused by apnea or respiratory dysfunction severe enough that it will not sustain the body. Prolonged apnea refers to a patient who has stopped breathing for a long period of time. If the heart muscle contraction is intact, the condition is known as respiratory arrest. An abrupt stop of pulmonary gas exchange lasting for more than five minutes may permanently damage vital organs, especially the brain. Lack of oxygen to the brain causes loss of consciousness. Brain injury is likely if respiratory arrest goes untreated for more than three minutes, and death is almost certain if more than five minutes.

<span class="mw-page-title-main">Artificial ventilation</span> Assisted breathing to support life

Artificial ventilation or respiration is when a machine assists in a metabolic process to exchange gases in the body by pulmonary ventilation, external respiration, and internal respiration. A machine called a ventilator provides the person air manually by moving air in and out of the lungs when an individual is unable to breathe on their own. The ventilator prevents the accumulation of carbon dioxide so that the lungs don't collapse due to the low pressure. The use of artificial ventilation can be traced back to the seventeenth century. There are three ways of exchanging gases in the body: manual methods, mechanical ventilation, and neurostimulation.

A resuscitator is a device using positive pressure to inflate the lungs of an unconscious person who is not breathing, in order to keep them oxygenated and alive. There are three basic types: a manual version consisting of a mask and a large hand-squeezed plastic bulb using ambient air, or with supplemental oxygen from a high-pressure tank. The second type is the expired air or breath powered resuscitator. The third type is an oxygen powered resuscitator. These are driven by pressurized gas delivered by a regulator, and can either be automatic or manually controlled. The most popular type of gas powered resuscitator are time cycled, volume constant ventilators. In the early days of pre-hospital emergency services, pressure cycled devices like the Pulmotor were popular but yielded less than satisfactory results. Most modern resuscitators are designed to allow the patient to breathe on his own should he recover the ability to do so. All resuscitation devices should be able to deliver more than 85% oxygen when a gas source is available.

<span class="mw-page-title-main">Breathing apparatus</span> Equipment allowing or assisting the user to breath in a hostile environment

A breathing apparatus or breathing set is equipment which allows a person to breathe in a hostile environment where breathing would otherwise be impossible, difficult, harmful, or hazardous, or assists a person to breathe. A respirator, medical ventilator, or resuscitator may also be considered to be breathing apparatus. Equipment that supplies or recycles breathing gas other than ambient air in a space used by several people is usually referred to as being part of a life-support system, and a life-support system for one person may include breathing apparatus, when the breathing gas is specifically supplied to the user rather than to the enclosure in which the user is the occupant.

<span class="mw-page-title-main">Bag valve mask</span> Hand-held device to provide positive pressure ventilation

A bag valve mask (BVM), sometimes known by the proprietary name Ambu bag or generically as a manual resuscitator or "self-inflating bag", is a hand-held device commonly used to provide positive pressure ventilation to patients who are not breathing or not breathing adequately. The device is a required part of resuscitation kits for trained professionals in out-of-hospital settings (such as ambulance crews) and is also frequently used in hospitals as part of standard equipment found on a crash cart, in emergency rooms or other critical care settings. Underscoring the frequency and prominence of BVM use in the United States, the American Heart Association (AHA) Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiac Care recommend that "all healthcare providers should be familiar with the use of the bag-mask device." Manual resuscitators are also used within the hospital for temporary ventilation of patients dependent on mechanical ventilators when the mechanical ventilator needs to be examined for possible malfunction or when ventilator-dependent patients are transported within the hospital. Two principal types of manual resuscitators exist; one version is self-filling with air, although additional oxygen (O2) can be added but is not necessary for the device to function. The other principal type of manual resuscitator (flow-inflation) is heavily used in non-emergency applications in the operating room to ventilate patients during anesthesia induction and recovery.

Positive end-expiratory pressure (PEEP) is the pressure in the lungs above atmospheric pressure that exists at the end of expiration. The two types of PEEP are extrinsic PEEP and intrinsic PEEP. Pressure that is applied or increased during an inspiration is termed pressure support. PEEP is a therapeutic parameter set in the ventilator, or a complication of mechanical ventilation with air trapping (auto-PEEP).

High-frequency ventilation is a type of mechanical ventilation which utilizes a respiratory rate greater than four times the normal value and very small tidal volumes. High frequency ventilation is thought to reduce ventilator-associated lung injury (VALI), especially in the context of ARDS and acute lung injury. This is commonly referred to as lung protective ventilation. There are different types of high-frequency ventilation. Each type has its own unique advantages and disadvantages. The types of HFV are characterized by the delivery system and the type of exhalation phase.

<span class="mw-page-title-main">Continuous positive airway pressure</span> Form of ventilator which applies mild air pressure continuously to keep airways open

Continuous positive airway pressure (CPAP) is a form of positive airway pressure (PAP) ventilation in which a constant level of pressure greater than atmospheric pressure is continuously applied to the upper respiratory tract of a person. The application of positive pressure may be intended to prevent upper airway collapse, as occurs in obstructive sleep apnea, or to reduce the work of breathing in conditions such as acute decompensated heart failure. CPAP therapy is highly effective for managing obstructive sleep apnea. Compliance and acceptance of use of CPAP therapy can be a limiting factor, with 8% of people stopping use after the first night and 50% within the first year.

Transpulmonary pressure is the difference between the alveolar pressure and the intrapleural pressure in the pleural cavity. During human ventilation, air flows because of pressure gradients.

<span class="mw-page-title-main">Airway pressure release ventilation</span> Pressure control mode of mechanical ventilation

Airway pressure release ventilation (APRV) is a pressure control mode of mechanical ventilation that utilizes an inverse ratio ventilation strategy. APRV is an applied continuous positive airway pressure (CPAP) that at a set timed interval releases the applied pressure. Depending on the ventilator manufacturer, it may be referred to as BiVent. This is just as appropriate to use, since the only difference is that the term APRV is copyrighted.

Modes of mechanical ventilation are one of the most important aspects of the usage of mechanical ventilation. The mode refers to the method of inspiratory support. In general, mode selection is based on clinician familiarity and institutional preferences, since there is a paucity of evidence indicating that the mode affects clinical outcome. The most frequently used forms of volume-limited mechanical ventilation are intermittent mandatory ventilation (IMV) and continuous mandatory ventilation (CMV). There have been substantial changes in the nomenclature of mechanical ventilation over the years, but more recently it has become standardized by many respirology and pulmonology groups. Writing a mode is most proper in all capital letters with a dash between the control variable and the strategy.

Work of breathing (WOB) is the energy expended to inhale and exhale a breathing gas. It is usually expressed as work per unit volume, for example, joules/litre, or as a work rate (power), such as joules/min or equivalent units, as it is not particularly useful without a reference to volume or time. It can be calculated in terms of the pulmonary pressure multiplied by the change in pulmonary volume, or in terms of the oxygen consumption attributable to breathing.

<span class="mw-page-title-main">Bragg-Paul Pulsator</span> Medical ventilator

The Bragg-Paul Pulsator, also known as the Bragg-Paul respirator, was a non-invasive medical ventilator invented by William Henry Bragg and designed by Robert W. Paul in 1933 for patients unable to breathe for themselves due to illness.

<span class="mw-page-title-main">Carl Gunnar Engström</span> Swedish physician and inventor

Carl Gunnar David Engström was a Swedish physician and innovator. He is the inventor of the first intermittent positive pressure mechanical ventilator that could deliver breaths of controllable volume and frequency and also deliver inhalation anesthetics.

Airway clearance therapy is treatment that uses a number of airway clearance techniques to clear the respiratory airways of mucus and other secretions. Several respiratory diseases cause the normal mucociliary clearance mechanism to become impaired resulting in a build-up of mucus which obstructs breathing, and also affects the cough reflex. Mucus build-up can also cause infection, and inflammation, and repeated infections can result in damage to the airways, and the lung tissue.

<span class="mw-page-title-main">Glossary of breathing apparatus terminology</span> Definitions of technical terms used in connection with breathing apparatus

A breathing apparatus or breathing set is equipment which allows a person to breathe in a hostile environment where breathing would otherwise be impossible, difficult, harmful, or hazardous, or assists a person to breathe. A respirator, medical ventilator, or resuscitator may also be considered to be breathing apparatus. Equipment that supplies or recycles breathing gas other than ambient air in a space used by several people is usually referred to as being part of a life-support system, and a life-support system for one person may include breathing apparatus, when the breathing gas is specifically supplied to the user rather than to the enclosure in which the user is the occupant.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 Shneerson, Dr. John M., Newmarket General Hospital, (Newmarket, Suffolk, U.K.), "Non-invasive and domiciliary ventilation: negative pressure techniques," #5 of series "Assisted ventilation" in Thorax, 1991;46: pp.131-135, retrieved April 12, 2020
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Grum, Cyril M., MD, and Melvin L. Morganroth, MD, "Initiating Mechanical Ventilation," in Intensive Care Medicine 1988;3:6-20, retrieved April 12, 2020
  3. 1 2 3 4 5 6 7 8 Rockoff, Mark, M.D., "The Iron Lung and Polio,", video (8 minutes), January 11, 2016, OPENPediatrics and Boston Children's Hospital on YouTube, retrieved April 11, 2020 (historical background and images, explanatory diagrams, and live demonstrations)
  4. 1 2 3 4 5 6 7 8 "The Iron Lung," Science Museum Group, Kensington, London, England, U.K., retrieved April 11, 2020
  5. 1 2 3 4 "How Does Iron Lung Work?: Polio Survivor, 82, Among Last to Use Breathing Equipment," August 21, 2018, Newsweek retrieved April 11, 2020
  6. 1 2 3 4 Jackson, Christopher D., MD, Dept. of Internal Medicine, and Muthiah P Muthiah, MD, FCCP, D-ABSM, Assoc. Prof. of Medicine, Div. of Pulmonary / Critical Care / Sleep Medicine, Univ. of Tennessee College of Medicine-Memphis, et.al., "What is the background of the iron lung form of mechanical ventilation?," April 11, 2019, Medscape, retrieved April 12, 2020 (short summary of iron history and technology, with photo)
  7. 1 2 3 Bottrell, John, "1907: The first mechanical ventilator: The Pulmotor," April 19, 2017, Asthma History blog, retrieved April 12, 2020
  8. 1 2 3 "Draeger Pulmotor", Wood Library-Museum of Anesthesiology
  9. 1 2 3 "The Return of the Pulmotor as a 'Resuscitator': A Back-Step toward the Death of Thousands," by Yandell Henderson, December 1943, Science.
  10. 1 2 3 Bahns, Ernst, It began with the Pulmotor: One Hundred Years of Artificial Ventilation, Dräger Medical AG & Co. KG, Lübeck, Germany (original manufacturers of the Pulmotor).
  11. ↑ Corrado, A.; Gorini, M.: "Negative-pressure ventilation: is there still a role?," European Respiratory Journal 2002, 20: pp.187-197;, also in PDF retrieved April 17, 2020
  12. 1 2 3 Raymondos, Konstantinos; Jörg Ahrens; Ulrich Molitoris: "Combined Negative- and Positive-Pressure Ventilation for the Treatment of ARDS", in Case Reports in Critical Care 2015; 2015: 714902. Published online July 28, 2015, from NCBI, National Institutes of Health, retrieved April 12, 2020.
  13. ↑ Walkey, Allan M.D. and Ross Summer M.D., "Negative pressure" in "E. Noninvasive Mechanical Ventilation," in Boston Medical Center ICU Manual, 2008, Boston University, p.17, retrieved April 12, 2020.
  14. 1 2 "Modern iron lung designed to address ventilator shortage,", April 06, 2020, New Atlas, retrieved April 11, 2020 (note detailed reader comment, , April 7, 2020, by Christopher Smith, with clinical application details.)
  15. 1 2 "The 'iron lung' and the modern 'ventilation'," Oxy.gen, retrieved April 11, 2020
  16. 1 2 Matioc, Adrian A., M.D., University of Wisconsin School of Medicine & Public Health, William S. Middleton Memorial Veterans Hospital, Madison, Wisconsin, "Early Positive and Alternate Pressure Machines" in "An Anesthesiologist’s Perspective on the History of Basic Airway Management: The 'Progressive' Era, 1904 to 1960," submitted May 27, 2017, published February 2018, Anesthesiology, Vol. 128, No 2
  17. ↑ "Poncho," [ permanent dead link ] by medical device manufacturer Dima Italia S.r.l. of Bologna, Italy (picture of jacket ventilator ("poncho"), and other information.), retrieved April 12, 2020
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