Bag valve mask
Encyclopedia
Ambulance
An ambulance is a vehicle for transportation of sick or injured people to, from or between places of treatment for an illness or injury, and in some instances will also provide out of hospital medical care to the patient...
crew. The BVM is frequently used in hospital
Hospital
A hospital is a health care institution providing patient treatment by specialized staff and equipment. Hospitals often, but not always, provide for inpatient care or longer-term patient stays....
s, and is an essential part of a crash cart
Crash cart
A crash cart or code cart is a set of trays/drawers/shelves on wheels used in hospital emergency rooms for transportation and dispensing of emergency medication/equipment at site of medical/surgical emergency for life support protocols to potentially save someone's life.The contents of a crash...
. The device is used extensively in the operating room to ventilate an anaesthetised patient in the minutes before a mechanical ventilator is attached. The device is self-filling with air, although additional oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
(O2) can be added.
Use of the BVM to ventilate a patient is frequently called "bagging" the patient. Bagging is regularly necessary in medical emergencies
Medical emergency
A medical emergency is an injury or illness that is acute and poses an immediate risk to a person's life or long term health. These emergencies may require assistance from another person, who should ideally be suitably qualified to do so, although some of these emergencies can be dealt with by the...
when the patient's breathing is insufficient (respiratory failure
Respiratory failure
The term respiratory failure, in medicine, is used to describe inadequate gas exchange by the respiratory system, with the result that arterial oxygen and/or carbon dioxide levels cannot be maintained within their normal ranges. A drop in blood oxygenation is known as hypoxemia; a rise in arterial...
) or has ceased completely (respiratory arrest
Respiratory arrest
Respiratory arrest is the cessation of breathing. It is a medical emergency and it usually is related to or coincides with a cardiac arrest. Causes include opiate overdose, head injury, anaesthesia, tetanus, or drowning...
). The BVM resuscitator is used in order to manually provide mechanical ventilation
Mechanical ventilation
In medicine, mechanical ventilation is a method to mechanically assist or replace spontaneous breathing. This may involve a machine called a ventilator or the breathing may be assisted by a physician, respiratory therapist or other suitable person compressing a bag or set of bellows...
in preference to mouth-to-mouth resuscitation (either direct or through an adjunct such as a pocket mask
Pocket mask
A pocket mask, or pocket face mask or CPR mask, is a device used to safely deliver rescue breaths during a cardiac arrest or respiratory arrest.-Design:...
).
History
The bag valve mask concept was developed in 1953 by the German engineer, Dr. Holger Hesse, and his partner, Danish anaesthetist Henning Ruben, following their initial work on a suction pump. They named their resuscitator Ambu bag, and then formed their own company, also called AmbuAmbu (company)
Ambu A/S , is a Danish company that develops, produces and markets diagnostic and life-supporting equipment and solutions to hospitals and rescue services.Founded in Denmark in 1937 by German engineer Holger Hesse, Ph.D...
, to manufacture and market it, starting in 1956. This has led to incorrect common usage of the proprietary name Ambu for bag valve masks from all manufacturers.
Standard components
American football
American football is a sport played between two teams of eleven with the objective of scoring points by advancing the ball into the opposing team's end zone. Known in the United States simply as football, it may also be referred to informally as gridiron football. The ball can be advanced by...
), attached to a face mask via a shutter valve. When the face mask is properly applied and the "bag" is squeezed, the device forces air through into the patient's lungs; when the bag is released, it self-inflates from its other end, drawing in either ambient air or a low pressure oxygen flow supplied by a regulated cylinder, while also allowing the patient's lungs deflate to the ambient environment (not the bag) past the one way valve.
Bag and valve combinations can also be attached to an alternate airway adjunct, instead of to the mask. Fpr example, it can be attached to an endotracheal tube
Tracheal tube
A tracheal tube is a catheter that is inserted into the trachea in order for the primary purpose of establishing and maintaining a patent airway and to ensure the adequate exchange of oxygen and carbon dioxide. Many different types of tracheal tubes are available, suited for different specific...
or laryngeal mask airway
Laryngeal mask airway
The laryngeal mask airway is a supraglottic airway device invented by Archie Brain, a British anaesthetist.-Description:Laryngeal masks consist of a tube with an inflatable cuff that is inserted into the pharynx. Laryngeal mask airways come in a variety of sizes ranging from large adult to infant...
. Often a small HME filter (Heat & Moisture exchanger, or humidifying / bacterial filter) is used.
A bag valve mask can be used without being attached to an oxygen tank to provide air to the patient, often called "room air" in the U.S. Supplemental oxygen increases the partial pressure of oxygen inhaled, helping to increase perfusion
Perfusion
In physiology, perfusion is the process of nutritive delivery of arterial blood to a capillary bed in the biological tissue. The word is derived from the French verb "perfuser" meaning to "pour over or through."...
in the patient.
Most devices also have a reservoir which can fill from an oxygen source during the patient expiratory phase (a process which happens passively for patients in respiratory arrest), in order to increase the amount of oxygen that can be delivered to the patient to nearly 100%.
Bag valve masks come in different sizes to fit infants, children, and adults. The mask size may be independent of the bag size; for example, a single pediatric-sized bag might be used with different masks for multiple face sizes, or a pediatric mask might be used with an adult bag for patients with small faces.
Most types of the device are disposable and therefore single use, while others are designed to be cleaned and reused.
Other components
A filter is sometimes placed between the mask and the bag (before or after the valve) to prevent contamination of the bag.Some devices have PEEP valve connectors, for better positive airway pressure maintenance.
A covered port may be incorporated into the valve assembly, to allow inhalatory medicines to be injected into the airflow.
A pressure relief valve (often known as a "pop-up valve") is often included in pediatric versions, and sometimes in adult versions, to prevent overinflation of the lungs. A bypass clip is typically incorporated into this valve assembly, in case medical protocol calls for inflation at a rate beyond the maximum pressure cuttoff allowed by the pop-up valve.
A connection for a pressure or flow meter may be included in the valve or mask assembly.
Some bags have a built-in strap to assist the pressure provider.
Some bags are designed to collapse for storage. A bag not designed to store collapsed may lose elasticity when stored compressed for long periods, reducing its effectiveness. The collapsible design has longitudinal scoring so that the bag collapses on the scoring "pivot point," opposite to the direction of normal bag compression.
Method of operation
The BVM directs the gas inside it via a one-way valveValve
A valve is a device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but are usually discussed as a separate category...
when compressed by a rescuer; the gas is then delivered through a mask and into the patient's trachea
Vertebrate trachea
In tetrapod anatomy the trachea, or windpipe, is a tube that connects the pharynx or larynx to the lungs, allowing the passage of air. It is lined with pseudostratified ciliated columnar epithelium cells with goblet cells that produce mucus...
, bronchus and into the lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s. In order to be effective, a bag valve mask must deliver between 500 and 800 milliliters of air to an adult patient's lungs, but if oxygen is provided through the tubing and if the patient's chest rises with each inhalation (indicating that adequate amounts of air are reaching the lungs), 400 ml may still be adequate. Squeezing the bag once every 5 seconds for an adult or once every 3 seconds for an infant or child provides an adequate respiratory rate
Respiratory rate
Respiratory rate is also known by respiration rate, pulmonary ventilation rate, ventilation rate, or breathing frequency is the number of breaths taken within a set amount of time, typically 60 seconds....
(12 respirations per minute in an adult and 20 per minute in a child or infant).
Professional rescuers are taught to ensure that the mask portion of the BVM is properly sealed around the patient's face (that is, to ensure proper "mask seal"); otherwise, air pressure is relieved to the environment instead of to the lungs. This is difficult when a single rescuer maintains the seal with one hand while operating the bag with other. Therefore, common protocol protocol uses two rescuers: one rescuer to hold the mask to the patient's face with both hands and focus entirely on mask seal, while the other squeezes the bag and focuses on tidal volume
Tidal volume
Tidal volume is the lung volume representing the normal volume of air displaced between normal inspiration and expiration when extra effort is not applied.Typical values are around 500ml or 7ml/kg bodyweight.-Mechanical Ventilation:...
and timing. However, in a two-person ambulance
Ambulance
An ambulance is a vehicle for transportation of sick or injured people to, from or between places of treatment for an illness or injury, and in some instances will also provide out of hospital medical care to the patient...
crew, the other crew member is likely to be doing compressions in the case of CPR, or may be performing other interventions such as defibrillation
Defibrillation
Defibrillation is a common treatment for life-threatening cardiac arrhythmias, ventricular fibrillation and pulseless ventricular tachycardia. Defibrillation consists of delivering a therapeutic dose of electrical energy to the affected heart with a device called a defibrillator...
or cannulation. In this case, or if no other options are available, the BVM can also be operated by a single rescuer who holds the mask to the patient's face with one hand, in the anaesthetists grip, and squeezes the bag with the other.
When using a BVM, as with other methods of positive pressure ventilation, there is a risk of over-inflating the lungs. This can lead to pressure damage to the lungs themselves, and can also cause air to enter the stomach, causing gastric distension
Gastric distension
Gastric Distension is bloating of the stomach when air is pumped into it. This may be done when someone is performing cardiopulmonary resuscitation and blowing air into the mouth of someone who is not breathing spontaneously...
which can make it more difficult to inflate the lungs. Another consequence may be to cause the patient to vomit
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
, which can cause additional airway problems beyond the original breathing difficulty. This can be usually be avoided by care on behalf of the rescuer. Alternatively, some models of BVM (usually pediatric) are fitted with a valve which prevents over-inflation, by venting the pressure when a pre-set pressure is reached. Nevertheless, the "Sellick maneuver" (application of cricoid pressure) is often applied to reduce the risk of aspiration of gastric contents
Pulmonary aspiration
Pulmonary aspiration is the entry of material from the oropharynx or gastrointestinal tract into the larynx and lower respiratory tract...
whenever possible until the trachea can be intubated
Tracheal intubation
Tracheal intubation, usually simply referred to as intubation, is the placement of a flexible plastic or rubber tube into the trachea to maintain an open airway or to serve as a conduit through which to administer certain drugs...
or until there is no longer any need for positive pressure ventilation.
An endotracheal tube can be inserted by a trained practitioner and can substitute for the mask portion of the BVM. This provides a more secure fit and is easier to manage during emergency transport, since the ET tube is sealed with an inflatable cuff in the trachea, so that any regurgitation
Regurgitation (digestion)
Regurgitation is the expulsion of material from the mouth, pharynx, or esophagus, usually characterized by the presence of undigested food or blood.Regurgitation is used by a number of species to feed their young...
is less likely to enter the lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s, and so that positive air pressure can only be relieved into the lungs. The ET also maintains an open airway at all times, even during CPR compressions; a BVM can typically only be operated during set pauses in compressions.
(Vomitus can severely damage the lung tissue, and in the absence of an ET tube, could choke
Choking
Choking is the mechanical obstruction of the flow of air from the environment into the lungs. Choking prevents breathing, and can be partial or complete, with partial choking allowing some, although inadequate, flow of air into the lungs. Prolonged or complete choking results in asphyxia which...
the patient by obstructing the airway. Inhalation of stomach contents can be fatal; the after effects can cause Mendelson's syndrome
Mendelson's syndrome
Mendelson's syndrome is chemical pneumonitis caused by aspiration during anaesthesia, especially during pregnancy.-Presentation:Mendelson's syndrome is characterised by a bronchopulmonary reaction following aspiration of gastric contents during general anaesthesia due to abolition of the laryngeal...
or aspiration pneumonia
Aspiration pneumonia
Aspiration pneumonia is bronchopneumonia that develops due to the entrance of foreign materials into the bronchial tree, usually oral or gastric contents...
.)
Some rescuers may also choose to use a different form of resuscitation adjunt, such as an oropharyngeal airway
Oropharyngeal airway
An oropharyngeal airway is a medical device called an airway adjunct used to maintain a patent airway. It does this by preventing the tongue from covering the epiglottis, which could prevent the person from breathing...
or Laryngeal mask airway
Laryngeal mask airway
The laryngeal mask airway is a supraglottic airway device invented by Archie Brain, a British anaesthetist.-Description:Laryngeal masks consist of a tube with an inflatable cuff that is inserted into the pharynx. Laryngeal mask airways come in a variety of sizes ranging from large adult to infant...
, which would be inserted and then used with the BVM.
In a hospital, long-term mechanical ventilation is provided by using more complex automated devices such as an intensive care ventilator
Medical ventilator
A medical ventilator can be defined as any machine designed to mechanically move breatheable air into and out of the lungs, to provide the mechanism of breathing for a patient who is physically unable to breathe, or breathing insufficiently....
, rather than by a BVM, which requires at least one person to operate it constantly.
A flow-restricted, oxygen-powered ventilation device
Flow-restricted, oxygen-powered ventilation device
A flow-restricted, oxygen-powered ventilation device , also referred to as a manually-triggered ventilation device , is used to assist ventilation in apneic or hypoventilating patients, although these devices can also be used to provide supplemental oxygen to breathing patents....
(FROPVD) is similar to a BVM in that oxygen is pushed through a mask into the patient's lungs, but unlike a BVM, in the FROPVD the pressure needed to push air into the patient's lungs is generated by oxygen via a pressure regulator from a cylinder rather than by squeezing a bag.