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Laryngeal mask airway | |
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Specialty | Anaesthetics |
A laryngeal mask airway (LMA), also known as laryngeal mask, is a medical device that keeps a patient's airway open during anaesthesia or while they are unconscious. It is a type of supraglottic airway device. They are most commonly used by anaesthetists to channel oxygen or inhalational anaesthetic to the lungs during surgery and in the pre-hospital setting (for instance by paramedics and emergency medical technicians) for unconscious patients.[ citation needed ]
A laryngeal mask is composed of an airway tube that connects to an elliptical mask with a cuff which is inserted through the patient's mouth, down the windpipe, and once deployed forms an airtight seal on top the glottis (unlike tracheal tubes which pass through the glottis) allowing a secure airway to be managed by a health care provider.
The laryngeal mask was invented by British anaesthesiologist Archibald Brain in the early 1980s, and in December 1987 the first commercial laryngeal mask was made available in the United Kingdom. The laryngeal mask is still widely used today worldwide, and a variety of specialised laryngeal masks exist.
It channels oxygen and inhalational anaesthetic to the lungs. It can be used during anaesthesia, or while a patient is unconscious. Laryngeal mask airways are designed to be an easy way to secure the airway and ventilate a patient – they are easier to place than tracheal intubation due to the lack of muscle relaxants and laryngoscopy. They are also less likely to damage teeth or the larynx itself. It may form an air-tight seal. Cuffs are available in multiple sizes. [1]
LMAs can be alternatives to the use of a face mask when using a bag-valve-mask device to prevent gastric insufflation. [2]
A laryngeal mask airway is generally not used in surgeries where there is a high risk that stomach contents may be aspirated. This is particularly for surgeries that last longer than 2 hours. It often uses low inflation pressures, so may not be appropriate in patients with illnesses that cause low lung compliance. As it is typically larger and more obstructive than tracheal intubation, it is generally not used for surgery of the mouth and throat. [1]
It should not be used for conscious patients because of the risk of stimulating the gag reflex. [2]
A laryngeal mask leaves more anatomical dead space in the trachea than with tracheal intubation. [1] This can decrease the oxygenation of the lungs and the removal of carbon dioxide. It also slightly increases airway resistance. [1] More serious complications include vomiting while the laryngeal mask airway is in place (potentially leading to aspiration of stomach contents). [1]
Although the laryngeal mask airway is specifically designed to be easy to place, it is possible for the ventilation it provides to be inadequate. [1] This may be due to variations in neck anatomy, abnormal neck position, dislodgement of the cuff, the mask not being long enough to reach the larynx (or more rarely too long), or folding of the mask in the pharynx. [1] For these reasons, radiology can be used to ensure that the laryngeal mask airway is in the correct position. [1]
A laryngeal mask airway has an airway tube that connects to an elliptical mask with a cuff. The cuff can either be an inflating type (achieved after insertion using a syringe of air), or self-sealing.[ citation needed ]
A laryngeal mask airway must first be completely sterilised (it may be reused many times). [1] Standard checks for common use defects should be performed (such as cracks in the plastic). [1] For an inflatable cuff, the cuff should be inflated and deflated outside the patient to ensure it is functional. [1] A pen-like grip is used to move it through the patient's mouth and throat, preferably when their head is extended to straighten the airway. [1] The laryngeal mask airway should be lubricated so that it can be placed more easily. [1]
Once inserted correctly (and the cuff inflated where relevant), the mask conforms to the anatomy with the bowl of the mask facing the space between the vocal cords. [1] The tip of the laryngeal mask sits in the throat against the upper oesophageal sphincter. [1] [3]
Archie Brain began studying the anatomy and physiology of the upper airway in relation to existing airways. Brain concluded that current techniques for connecting artificial airways to the patient were not ideal. He reasoned that if the respiratory tree is seen as a tube ending at the glottis and the objective is to connect this tube to an artificial airway, the most logical solution was to create a direct end-to-end junction. Existing airway devices failed to form this junction; the face-mask sealed against the face, and the endotracheal tube penetrated too far so that the junction was created within the trachea, instead of at its beginning. [4]
The first study of a laryngeal mask in 23 patients was conducted at London Hospital in 1982. Insertion and ventilation using the laryngeal mask in 16 anaesthetised, paralysed female patients was successful, achieving a seal greater than 20 cm H2O in all patients. Emergence from anaesthesia was also noted to be uneventful and only 3 patients complained of a sore throat, a marked contrast to endotracheal tube anaesthesia. Following the success of the initial study, Brain successfully inserted and ventilated 6 anaesthetised, non-paralysed patients. Finding no difference between the first and second group of patients, Brain realised that muscle relaxation was not required for insertion. Finally, Dr Brain used the device in a dental extraction patient, he realised that because the space in and around the glottis was filled by the mask, the need for packing was much reduced and more impressively the larynx was completely protected from surgical debris. Brain realised the exciting possibility that the laryngeal mask could be applied to head and neck surgery [5] and also observed that "In two patients the anatomy was such as to suggest that endotracheal intubation might have presented at least moderate difficulty. Neither presented difficulty with regard to insertion of the laryngeal mask ". [6] By 1985, experience with the laryngeal mask prototype had reached 4000 cases. Brain published a case series in Anaesthesia in 1985 describing the management of 3 difficult airway patients, illustrating the use of the laryngeal mask for airway rescue. Brain with 5 co-authors published a second paper in anaesthesia describing the use of the laryngeal mask in over 500 patients, adding considerable credence to the laryngeal mask concept. However the limitation of the prototypes remained, a new material was urgently needed.[ citation needed ]
Following the realisation that a new material was needed, Brain looked at a number of options; polyvinyl chloride was too rigid and synthetic foam did not lend itself to re-use. Silicone prototypes looked promising as what was produced was an ellipse with a flat central web which, if cut correctly, could be used to create an aperture bar to prevent the epiglottis falling into the distal aperture. The silicone prototype was also smooth and deflated into a wafer thin ellipse, however, the silicone mask was unable to retain the desired bowl shape and it was no longer possible to make rapid adjustments to the design. The silicone Dunlop prototype was superior to the Goldman prototype, one of Brain's first prototypes created from the cuff of a latex Goldman dental mask, however Brain needed a material that would give him design flexibility before the next set of silicone moulds were cast. In 1986, Brain continued to make prototypes from latex with a range of modifications; the inclusion of an inflation line, a thin-walled elliptical ring in the cuff which resulted in equal expansion of the cuff, the creation of a larger size to increase the reliability of cuff seal pressure and a moulded back plate for the cuff. By December 1986, Brain was ready to conduct the first wholly independent trial and chose John Nunn to be the recipient of the silicone prototypes to conduct the trial. [7] "There were three outstanding advantages of the LMA in patients who breathed spontaneously. Firstly, excellent airway patency was obtained in 98% of patients and did not deteriorate during the course of the anaesthetic. Secondly, as no manual support of the jaw was necessary the hands of the anaesthetist were freed for monitoring, record keeping and other tasks. Thirdly, it was possible to maintain a clear airway throughout transfer of the patient to the recovery room." The publication of this trial in 1989 was critical in kickstarting the uptake of the laryngeal mask in the UK". [8]
On 5 December 1987, Brain received the first case of all-factory-made, silicone cuffed, LMA Classic laryngeal mask distributed by The Laryngeal Mask Company Limited. The LMA Classic was launched in the UK and the British anaesthesia community were quick to realise the potential benefits of the laryngeal mask. Within 3 years of launch in the UK, the device had been used in at least 2 million patients and was available in every hospital. By 1992, the laryngeal mask was approved for sale and being sold in Australia, New Zealand, South Korea, Hong Kong, Taiwan, Malaysia, India and the United States. The anaesthesia community had been calling for practice guidelines and in 1992 the ASA commissioned a task force to establish practice guidelines for managing difficult airway situations. The ASA algorithm for difficult airways was published in 1993 and stressed an early attempt at insertion of the laryngeal mask if face mask ventilation was not adequate. The laryngeal mask revolutionised anaesthetic practice and by 1995 had been used in excess of 100 million patients and was available in more than 80 countries throughout the world. The laryngeal mask had now been widely accepted as a form of airway management. [9] From 1988 to 2017, more than 200 million patients used laryngeal mask. [ citation needed ]
Between 1989 and 2000 a variety of specialised laryngeal masks were released which included the LMA Flexible (1990), LMA Fastrach (1997), LMA Unique (1997) and LMA ProSeal (2000), all offered by The Laryngeal Mask Company.[ citation needed ]
Tracheal intubation, usually simply referred to as intubation, is the placement of a flexible plastic tube into the trachea (windpipe) to maintain an open airway or to serve as a conduit through which to administer certain drugs. It is frequently performed in critically injured, ill, or anesthetized patients to facilitate ventilation of the lungs, including mechanical ventilation, and to prevent the possibility of asphyxiation or airway obstruction.
Laryngoscopy is endoscopy of the larynx, a part of the throat. It is a medical procedure that is used to obtain a view, for example, of the vocal folds and the glottis. Laryngoscopy may be performed to facilitate tracheal intubation during general anaesthesia or cardiopulmonary resuscitation or for surgical procedures on the larynx or other parts of the upper tracheobronchial tree.
General anaesthesia (UK) or general anesthesia (US) is a method of medically inducing loss of consciousness that renders a patient unarousable even with painful stimuli. This effect is achieved by administering either intravenous or inhalational general anaesthetic medications, which often act in combination with an analgesic and neuromuscular blocking agent. Spontaneous ventilation is often inadequate during the procedure and intervention is often necessary to protect the airway. General anaesthesia is generally performed in an operating theater to allow surgical procedures that would otherwise be intolerably painful for a patient, or in an intensive care unit or emergency department to facilitate endotracheal intubation and mechanical ventilation in critically ill patients. Depending on the procedure, general anaesthesia may be optional or required. Regardless of whether a patient may prefer to be unconscious or not, certain pain stimuli could result in involuntary responses from the patient that may make an operation extremely difficult. Thus, for many procedures, general anaesthesia is required from a practical perspective.
A tracheal tube is a catheter that is inserted into the trachea for the primary purpose of establishing and maintaining a patent airway and to ensure the adequate exchange of oxygen and carbon dioxide.
Airway management includes a set of maneuvers and medical procedures performed to prevent and relieve airway obstruction. This ensures an open pathway for gas exchange between a patient's lungs and the atmosphere. This is accomplished by either clearing a previously obstructed airway; or by preventing airway obstruction in cases such as anaphylaxis, the obtunded patient, or medical sedation. Airway obstruction can be caused by the tongue, foreign objects, the tissues of the airway itself, and bodily fluids such as blood and gastric contents (aspiration).
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.
In anaesthesia and advanced airway management, rapid sequence induction (RSI) – also referred to as rapid sequence intubation or as rapid sequence induction and intubation (RSII) or as crash induction – is a special process for endotracheal intubation that is used where the patient is at a high risk of pulmonary aspiration. It differs from other techniques for inducing general anesthesia in that several extra precautions are taken to minimize the time between giving the induction drugs and securing the tube, during which period the patient's airway is essentially unprotected.
Sir Ivan Whiteside Magill KCVO was an Irish-born anaesthetist who is famous for his involvement in much of the innovation and development in modern anaesthesia. He helped to establish the Association of Anaesthetists of Great Britain and Ireland. Several medical devices are named after him.
Stridor is an extra-thoracic high-pitched breath sound resulting from turbulent air flow in the larynx or lower in the bronchial tree. It is different from a stertor, which is a noise originating in the pharynx.
An oropharyngeal airway is a medical device called an airway adjunct used in airway management to maintain or open a patient's airway. It does this by preventing the tongue from covering the epiglottis, which could prevent the person from breathing. When a person becomes unconscious, the muscles in their jaw relax and allow the tongue to obstruct the airway.
The Combitube—also known as the esophageal tracheal airway or esophageal tracheal double-lumen airway—is a blind insertion airway device (BIAD) used in the pre-hospital and emergency setting. It is designed to provide an airway to facilitate the mechanical ventilation of a patient in respiratory distress.
Cricoid pressure, also known as the Sellick manoeuvre or Sellick maneuver, is a technique used in endotracheal intubation to try to reduce the risk of regurgitation. The technique involves the application of pressure to the cricoid cartilage at the neck, thus occluding the esophagus which passes directly behind it.
Archie Brain is a British anaesthetist best known as the inventor of the laryngeal mask. The LMA has been used over 300 million times worldwide in elective anaesthesia and emergency airway management.
Tracheal intubation, an invasive medical procedure, is the placement of a flexible plastic catheter into the trachea. For millennia, tracheotomy was considered the most reliable method of tracheal intubation. By the late 19th century, advances in the sciences of anatomy and physiology, as well as the beginnings of an appreciation of the germ theory of disease, had reduced the morbidity and mortality of this operation to a more acceptable rate. Also in the late 19th century, advances in endoscopic instrumentation had improved to such a degree that direct laryngoscopy had finally become a viable means to secure the airway by the non-surgical orotracheal route. Nasotracheal intubation was not widely practiced until the early 20th century. The 20th century saw the transformation of the practices of tracheotomy, endoscopy and non-surgical tracheal intubation from rarely employed procedures to essential components of the practices of anesthesia, critical care medicine, emergency medicine, gastroenterology, pulmonology and surgery.
The laryngeal tube is an airway management device designed as an alternative to other airway management techniques such as mask ventilation, laryngeal mask airway, and tracheal intubation. This device can be inserted blindly through the oropharynx into the hypopharynx to create an airway during anaesthesia and cardiopulmonary resuscitation so as to enable mechanical ventilation of the lungs.
Airtraq is a fibreoptic intubation device used for indirect tracheal intubation in difficult airway situations. It is designed to enable a view of the glottic opening without aligning the oral with the pharyngeal, and laryngeal axes as an advantage over direct endotracheal intubation and allows for intubation with minimal head manipulation and positioning.
A double-lumen endotracheal tube is a type of endotracheal tube which is used in tracheal intubation during thoracic surgery and other medical conditions to achieve selective, one-sided ventilation of either the right or the left lung.
A blind insertion airway device is a medical device used for airway management that ensures an open pathway between a patient's lungs and the outside world, as well as reducing the risk of aspiration, which can be placed without visualization of the glottis. Blind insertion airway devices are often used in the pre-hospital and emergency setting.
Advanced airway management is the subset of airway management that involves advanced training, skill, and invasiveness. It encompasses various techniques performed to create an open or patent airway – a clear path between a patient's lungs and the outside world.
Intubation granuloma is a benign growth of granulation tissue in the larynx or trachea, which arises from tissue trauma due to endotracheal intubation. This medical condition is described as a common late complication of tracheal intubation, specifically caused by irritation to the mucosal tissue of the airway during insertion or removal of the patient's intubation tube.