It is a type of supraglottic airway.
A laryngeal mask airway (LMA), also known as a laryngeal mask, is a medical device that keeps a patient’s airway open during anesthesia or loss of consciousness.
A laryngeal mask is made up of an airway tube that connects to an elliptical mask with a cuff that is inserted through the patient’s mouth through the trachea.
And once deployed it forms an airtight seal at the top of the glottis (unlike tracheal tubes that pass through the glottis) allowing a healthcare provider to deliver a safe airway.
They are commonly used by anesthetists to channel oxygen or anesthesia gas into a patient’s lungs during surgery and in the pre-hospital setting (for example, by paramedics and EMTs) for unconscious patients.
The laryngeal mask was invented by British anesthetist Archibald Brain in the early 1980s and in December 1987 the first commercial laryngeal mask was made available in the UK.
The laryngeal mask is still widely used throughout the world and a variety of specialized laryngeal masks exist.
A laryngeal mask has an airway tube that connects to an elliptical mask with a cuff. The cuff can be of the inflation type (achieved after insertion with an air syringe), or self-sealing.
Once properly inserted (and the cuff inflates as appropriate), the mask conforms to the anatomy with the mask bowl facing the space between the vocal cords.
After correct insertion, the tip of the laryngeal mask sits in the throat against the muscular valve at the top of the esophagus.
Dr. Archie Brain began studying the anatomy and physiology of the upper airway in relation to existing airways.
Dr. Brain concluded that the current techniques to connect the artificial airways with the patient were not ideal, since if the respiratory tree looks like a tube that ends in 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 clearly failed to form this junction; the mask was sealed against the face and the endotracheal tube penetrated too far, so that the junction was created within the trachea, rather than at first.
Dr. Brain wrote in his journal in May 1981: “Better, use a loop that fits into the anatomical loop of the space around the larynx, projecting down into the esophagus, which may be hollow, to drain fluid. regurgitant.
Dr. Brain made cadaver plaster casts of the space around and behind the glottis, a space adapted to accepting foreign bodies in the form of food, so it is likely to tolerate an inflated cuff.
Dr. Brain recognized that if the canister-shaped space were filled with an expandable sleeve, an end-to-end seal could be formed.
Dr. Brain experimented with the Goldman Dental Nasal Mask Cuff, if the lashes met in the midline they produced a remarkable approximation to plaster casts.
The last step in creating the first prototype laryngeal mask was to incorporate a tube.
Satisfied with the results of inserting the prototype laryngeal mask into cadavers, the prototype laryngeal mask was first used in the summer of 1981 in a 40-year-old male patient who underwent elective inguinal hernia repair.
To Dr. Brain’s delight, it was possible to ventilate the lungs, indicating not only that the device provided a clear airway, but also formed an effective seal with the glottic inlet.
The first study of a laryngeal mask in 23 patients was carried out at the London Hospital in 1982.
The insertion and ventilation with the laryngeal mask in 16 anesthetized and paralyzed patients was successful, achieving a seal of more than 20 cm H2O in all patients.
The onset of anesthesia was also observed without complications and only 3 patients complained of a sore throat, a stark contrast to endotracheal tube anesthesia.
Following the success of the initial study, Dr. Brain successfully inserted and ventilated 6 anesthetized and nonparalyzed patients.
Finding no difference between the first and second groups of patients, Dr. Brain realized that muscle relaxation was not necessary for insertion.
Finally, Dr. Brain used the device on a tooth extraction patient, he realized that because the mask filled the space in and around the glottis, the need for packing was greatly reduced and, more impressively, the larynx was completely protected from surgical debris.
Brain realized the exciting possibility that the laryngeal mask could be applied to head and neck surgery and also noted that “in two patients the anatomy was such that it suggested that endotracheal intubation might have been at least moderately difficult.
Neither of them presented difficulties regarding the insertion of the laryngeal mask ”.
By 1985, experience with the laryngeal mask prototype had reached 4,000 cases. The laryngeal mask for airway rescue.
Dr. Brain, with 5 co-authors, published a second article in anesthesia describing the use of the laryngeal mask in over 500 patients, adding considerable credibility to the laryngeal mask concept.
However, the limitation of prototypes remained, a new material was urgently needed.
Search for new material
Realizing that new material was needed, Brain examined several options; The polyvinyl chloride was too stiff and the synthetic foam did not lend itself to reuse.
The silicone prototypes looked promising as what was produced was an ellipse with a flat central band which, if cut properly, could be used to create an opening bar to prevent the epiglottis from falling into the distal opening.
The silicone prototype was also smooth and deflated into a thin ellipse, however the silicone mask was unable to maintain the desired bowl shape and quick adjustments to the design were no longer possible.
The Dunlop silicone prototype was superior to the Goldman prototype, one of Brains’ first prototypes created from a Goldman latex dental mask; however, Brain needed a material that would give it design flexibility before the next set of silicone molds was cast.
In 1986, Brain continued to make prototypes from latex with a series of modifications.
The inclusion of an inflation line, a thin-walled elliptical ring on the cuff that resulted in equal cuff expansion, creating a larger size to increase cuff sealing pressure reliability, and a molded back plate for the bracelet.
In December 1986, Brain was ready to perform the first fully independent test and selected Dr. John Nunn to receive the silicone prototypes to perform the test. “There were three salient advantages of laryngeal mask airway in spontaneously breathing patients.”
First, excellent airway patency was obtained in 98% of the patients and did not deteriorate during the course of the anesthetic.
Second, as no manual jaw support was necessary, the anesthetist’s hands were freed for monitoring, recording, and other tasks.
Third, it was possible to maintain a clear airway during transfer of the patient to the recovery room. “The publication of this essay in 1989 was instrumental in driving uptake of the laryngeal mask in the UK.”
First commercial laryngeal mask
On December 5, 1987, Brain received the first case of a classic laryngeal mask, silicone-shaped, with laryngeal mask and airway, distributed by Laryngeal Mask Company Limited.
The laryngeal mask airway classic was launched in the UK and the British anesthesia community quickly realized 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 all hospitals.
In 1992, the laryngeal mask was approved for sale and sold in Australia, New Zealand, South Korea, Hong Kong, Taiwan, Malaysia, India, and the United States.
The anesthesia community had been calling for guidelines for practice and in 1992 the American Society of Anesthesiologists (ASA) commissioned a task force to establish practical guidelines for handling difficult airway situations.
The American Society of Anesthesiologists’ Algorithm for Difficult Airways was published in 1993 and highlighted an early attempt at laryngeal mask insertion if mask ventilation was not adequate.
The laryngeal mask revolutionized anesthetic practice and, by 1995, it had been used in more than 100 million patients and was available in more than 80 countries around the world. The laryngeal mask had now been widely accepted as a form of airway management.
Between 1989 and 2000, a variety of specialized laryngeal masks were released including the flexible airway laryngeal air mask (1990), fastrach laryngeal air mask (1997), airway unique laryngeal air mask (1997), and proseal airway laryngeal mask ( 2000), all offered by the laryngeal mask company.
Classic Laryngeal Airway Mask
The classic laryngeal mask airway consists of a tube with an inflatable mask. The entire appliance is latex free with a silicone edge. The mask is a flattened, pear-shaped inflatable armband with an open front.
If positioned correctly, the opening covers the glottis and the proximal end faces the base of the tongue and the distal edge wedges against the upper esophageal sphincter, forming a seal.
The classic laryngeal mask airway is autoclavable and reusable. Its total use has been estimated at approximately 200 million patient uses since its introduction into clinical practice.
Proseal airway laryngeal mask
The proseal laryngeal mask airway was launched in 2000 and is a modified version of the classic laryngeal mask airway.
In addition to the silicone rim intended to seal around the larynx, the distal tip has an esophageal drainage port designed to communicate with the gastrointestinal tract.
The port allows suction, potentially reducing the risk of gastric content aspiration.
Its insertion time is slightly longer compared to the classic laryngeal mask airway, but it shows a 50% improvement in obtaining a proper seal.
If the device is placed too proximal or there is a leak, air is detected from the esophageal port.
Many unconventional techniques for proseal laryngeal mask airway insertion have been described, offering options for the operator when faced with a difficult airway in the adult or pediatric population.
Potential problems may include poor position, laryngeal edema, 9 and airway obstruction. Complications regarding the laryngeal mask airways in general are discussed later.
Laryngeal airway intubator mask, fastrach
It is a modified version of the classic laryngeal mask airway with the upper part of the tube removed. The remaining tube has a metal core with a handle used for positioning at its proximal end.
After establishing an airway with the intubating laryngeal mask airway, an endotracheal tube (ETT) can be inserted through the metal channel. It has been incorporated into difficult airway management algorithms.
It is easy to use and can save lives. In a study using manikin models, both experienced and inexperienced operators achieved high first-attempt intubation success rates after a 60-second demonstration.
C-tracheal laryngeal mask
Last year, a modified intubating laryngeal mask airway was developed that incorporates fiber optics to provide a real-time view of the glottis.
It is directed at the difficult airway, and a study examining its usefulness in the intubation of obese patients demonstrated favorable initial success rates.
Disposable Laryngeal Airway Mask
There are 3 main types of disposable laryngeal mask airways. These include the laryngeal mask, single airway, portex soft seal, and ambu laryngeal mask (now called auraonce).
The single laryngeal mask airway is very similar to the classic reusable laryngeal mask airway.
The portex soft seal does not have the silicone rim. The ambergris mask has a rigid curve in the main tube to better accommodate the oropharyngeal anatomy.
Most studies of these devices are small and investigate the timing of insertion and safety.
Brimacombe et al. compared the single laryngeal air mask and the soft seal, and found that the single airway laryngeal air mask is easier to insert and allows a better glottic position.
All 3 were recently compared by Francksen et al. All were quite similar in clinical use, ease of insertion, and success rate; The laryngeal ambu mask with the shortest insertion time.
All airways in the laryngeal mask consist of 2 parts, a continuous hollow tube with a hollow mask. The pear-shaped mask has an open front and a closed back.
An opening bar extends across the open front to prevent obstruction of the tube by the epiglottis. The posterior part is lubricated and makes contact with the palate and pharynx during insertion.
Stand on the flexed neck and the extended head of the patient in a supine position; the tube is held with the dominant hand as close to the mask as possible, as if it were a pen.
The deflated flattened mask is inserted against the hard palate down into the mouth following the contour of the back of the pharynx to get behind and under the tongue to finally sit at the entrance to the larynx.
The index finger follows the tube into the mouth to keep pressing “back” and “down” until the appliance is properly seated in the piriformis fossa.
An alternative to intraoral manipulation is to allow the dominant hand to guide the tube when the mouth is reached and to use the non-dominant hand to push the tube with or without an introducer.
Various manuals and videotapes demonstrating proper techniques are available.
It is important to quickly assess the correct placement of the airway. Cuff inflation pressure should not exceed 60mm Hg and proper tidal volumes should be achieved with minimal leakage.
If the mask is misplaced, the mask must be replaced and other maneuvers attempted. The use of a partially or fully inflated cuff can facilitate insertion.
Wakeling et al. states that insertion with a fully inflated cuff causes less mucosal trauma and therefore less postoperative sore throat.
Brimacombe refutes this claim. These maneuvers not only aid insertion but also increase morbidity. If available, a second operator can apply a jaw thrust maneuver.
This moves the tongue forward and out of the way and also prevents compression of the epiglottis. If a second operator is not available, a tongue depressor or even laryngoscopy can be used to reposition the tongue.
Another maneuver for difficult positioning is to stand facing the patient. This can facilitate placement because the dominant hand action is now “forward” rather than “backward.”
This technique can be used if the patient is sitting or semi-reclined or when neck flexion and head extension are not desirable.
The fit of the mask also depends on the size of the cuff and the volume of air used to fill it.
The maximum volume of air, which can be used to inflate the cuff, is written on the airway of the laryngeal mask with an inflation pressure not to exceed 60 mm Hg.
Dr. Brain, in his 1991 manual, states that a better seal is obtained by using the largest cuff size possible.
If the mask is too small, the cuff will have to over-inflate to form a seal, which can lead to poor positioning.
Controversy exists as to whether the larger mask with less inflation decreases or increases postoperative morbidity, such as a sore throat.
Selection based on weight has given way to selection based on sex, especially in adults. Asai and Brimacombe have summarized many studies that have looked at this problem.
The consensus seems to be that wearing a size 3 for most adult women and a size 4 for most adult men is inappropriate.
The correct size would be a size 4 for most adult women and a size 5 for most adult men.
Regardless of the initial size selected, if there is a poor position or an inadequate seal, a larger laryngeal mask airway should be considered.
A priori identification of a difficult laryngeal mask airway insertion can be problematic. A smaller than desired laryngeal mask airway can be used due to a small opening in the mouth.
The Mallampati class, used to identify difficult intubations, may or may not herald the placement of a difficult laryngeal mask airway.
A study by Brimacombe and Berry indicated that laryngeal mask airway placement does not correlate with the Mallampati class, while a study by McCrory and Moriarty indicates a positive correlation.
We suggest that if repeated attempts with one type of laryngeal mask airway are unsuccessful, switching to another type or even a third type may work. No studies have been conducted on this phenomenon.
One of the reasons laryngeal masks have gained popularity is because successful donning is easily learned. However, its routine use by personnel not trained in airway management is advised.
None of the studies state that 100% successful placement and alternative airway management maneuvers may be necessary.
Many studies have looked at the ease of training with medical providers who have little experience in airway management.
It seems clear that training with a manikin is sufficient to master the basics of using the laryngeal airway mask. Furthermore, studies have shown that these basics only need a short training period.
However, not all mannequins are the same. Silsby et al. evaluated 4 different manikins to teach the use of the laryngeal mask in the airways.
They concluded that 3 (ie Bill 1, Airsim and Airway Trainer) of the 4 manikins offered an acceptable training experience, while the Airway Management Trainer was rated as not acceptable.
Hesselfeldt et al. evaluated Simman, a complete patient simulator, and was considered acceptable for training with a laryngeal mask airway.
Parry and Owen tested many manikins and found that most would be acceptable or good for laryngeal mask airway training.
Tiah et al. advocate for an emphasis on airway management training in medical school.
They found that medical students were able to place the laryngeal mask airway in the fastest and most reproducible way compared to other airway devices, such as the Combitube and the endotracheal tube.
Effect on the physiological response
Another reason that the laryngeal mask airway has gained popularity is due to its decreased physiological response compared to insertion of an endotracheal tube.
Many studies have shown that changes in heart rate and blood pressure are significantly reduced with the insertion of a laryngeal mask compared to the insertion of an endotracheal tube or a comparable invasive device.
Hemodynamic changes are similar when comparing a laryngeal mask airway and a less invasive device (such as a cuffed oropharyngeal airway).
Insertion of a laryngeal mask airway also minimizes other effects. Insertion does not cause an increase in intraocular pressure, and agarwal and shobhana imply that insertion does not increase intracranial pressure (ICP).
To an untrained observer, laryngeal mask airway insertion may seem like a simple procedure.
However, incorrect insertion techniques explain many of the problems associated with their use.
The optimal position of the mask at the laryngeal inlet allows unimpeded gas exchange to occur and may also allow positive pressure ventilation.
An improperly fitted laryngeal mask airway causes a gas leak around the cuff, especially when using positive pressure.
Laryngeal mask airway malposition may not always be apparent and a flexible bronchoscope may be necessary to verify the position of the opening.
The risk of gastric distention, gastroesophageal reflux and tracheal dirt can increase with incorrect positioning, especially if positive pressure is used.
However, several studies have shown that if a laryngeal mask airway was positioned correctly, the risks of gastric distention and gastroesophageal reflux were not increased compared to an endotracheal tube.
Cassu et al. showed that the use of a laryngeal mask airway in ventilated cats can cause reflux but not aspiration.
Haslam et al. reported a case of gastric rupture during cardiopulmonary resuscitation attributed to the use of the laryngeal airway mask. Nolan et al. refute this
Soft tissue trauma during laryngeal mask airway placement is not an uncommon occurrence and blood can often be seen when removing the laryngeal mask airway.
Folding of the airway tip of the laryngeal mask on itself, use of undue force, incorrect technique, or inadequate depth of anesthesia are often to blame for these mishaps.
Trauma to the uvula and the posterior wall of the pharynx has been reported.
Several cases of nerve palsy have been reported, including palsy of the lingual nerve, hypoglossal nerve, glossopharyngeal nerve, and recurrent laryngeal nerve.
Brimacombe et al. Check out many of these cases. Tongue swelling, tongue cyanosis, arytenoid cartilage dislocation, temporomandibular joint dislocation, and vocal cord dysfunction have been reported.
At least some of these complications can be attributed to elevated cuff pressures or prolonged use of the laryngeal mask airway.
Bronchospasm, laryngospasm, stridor, and partial or total airway obstruction may be found and may be related to the depth of anesthesia or the harmfulness of the surgical stimulus.
Although many of these complications may be susceptible to deepening anesthesia or the use of a muscle relaxant, on occasion, it may be necessary to replace the laryngeal mask airway with an endotracheal tube.
Coughing is also often seen during the emergence of anesthesia when coughing, hitting, and biting the airway with laryngeal mask.
However, for the most part, laryngeal mask airway is quite well tolerated even during emergency and removal is done after simply asking the patient to open their mouth.
Uses of laryngeal mask airway for airway management
The laryngeal mask airway can be used in the spontaneously breathing patient with adequate sedation and topical anesthesia, or in the anesthetized and paralyzed patient with assisted mechanical ventilation.
It can be used in many situations, such as bronchoscopic procedures performed in the endoscopy setting, elective surgeries in outpatient clinics, procedures in critical care units, as well as in the field outside of the hospital with emergency care providers and personnel. emergency.
As a substitute for a mask
Anesthesiologists have considered the laryngeal mask airway to be a substitute for a mask in many situations.
Laryngeal mask airways are especially helpful when mask fitting is difficult such as in edentulous or bearded patients. They also serve to free the hands of the anesthesiologist so that one can attend to other essential tasks simultaneously.
Diagnostic and interventional airway procedures are becoming common among pediatric pulmonologists.
Flexible bronchoscopies comprise the major airway procedures performed, including bronchoalveolar lavage, transbronchial biopsies, and foreign body removal.
Complications are rare but include hypoxemia, laryngospasm, bronchospasm, and local trauma.
A laryngeal mask is a preferred technique for controlling the airways in the pediatric population compared to the adult population due to the difference in body size, airway diameter, and lower tolerance to conscious sedation.
When performing bronchoscopy , the laryngeal mask airway provides a safe alternative with minimal complication compared to nasal or endotracheal intubation.
The use of the airway with a laryngeal mask during pediatric tanning sessions is associated with ease of insertion, patient comfort during general anesthesia with spontaneous or assisted ventilation, as well as a net decrease in procedure time.
As a laryngeal mask is a supraglottic device, it has been shown to be useful in assisting in the diagnosis of subglottic pathologies.
Most diagnostic bronchoscopies in adults are performed in spontaneously breathing patients under conscious sedation.
Therefore, general anesthesia is not usually necessary. However, certain patients who cannot tolerate the procedure, even with conscious sedation (i.e., excessive gag response or discomfort) may require general anesthesia.
A laryngeal mask is an ideal device for establishing an airway. It is quite non-invasive and its proper positioning can be easily ensured with the flexible bronchoscope.
Furthermore, new technologies in diagnostic bronchoscopy can, in specific circumstances, benefit a deeply sedated or even generally anesthetized patient.
For example, electromagnetic navigation bronchoscopy is a technology used to sample small peripheral lesions, such as solitary lung nodules.
The technology is safe with improved precision compared to conventional bronchoscopy, but its precision has not been compared between the moderately sedated patient who breathes spontaneously and the patient under deep sedation or anesthesia.
The use of the laryngeal mask airway in this outpatient procedure would facilitate navigation to the periphery as well as during actual tissue acquisition. Additionally, the anesthesiologist can manipulate the respiratory cycle to improve diagnostic accuracy.
However, the use of a laryngeal airway has not been investigated and may miss the expected benefit of the minimally invasive nature of the procedure.
Therapeutic bronchoscopies are becoming commonplace in the arsenal of interventional pulmonologists.
Tools such as self-expanding metal stents, photoablation techniques for tumor ablation or hemoptysis, and foreign body retrieval can save lives.
Anesthesia for these procedures is also evolving, as they are traditionally performed under general anesthesia and rigid bronchoscopies.
In proximal central airway injuries, laryngeal mask airways as supraglottic devices can be used for therapeutic intervention, while providing a safe airway in the anesthetized patient.
Percutaneous bedside tracheostomies are increasingly being performed in the intensive care setting.
Most percutaneous tracheostomies are indicated in patients who are dependent on mechanical ventilation due to acute illness, or if the duration of endotracheal intubation is anticipated to be more than 2 weeks.
The recommended technique is performed with the bronchoscope at the proximal end of the endotracheal tube and withdrawing it above the first tracheal ring.
The bronchoscope helps to visualize the needle and guidewire entering the lumen of the trachea, with subsequent dilation with a conical dilator to create the stoma.
Once correct placement of the tracheostomy tube is confirmed, the endotracheal tube can be safely removed.
A retrospective study by Cattano et al. patients reviewed who underwent percutaneous tracheostomy with dilating forceps after the endotracheal tube was replaced by a laryngeal mask airway.
They considered that the supraglottic device offered a superior view of the proximal trachea without the risk of piercing the needle equipment, such as the bronchoscope or endotracheal tube.
The study did not show increased risks such as bleeding. An earlier prospective study comparing laryngeal mask airway versus endotracheal tube for percutaneous tracheostomy found less hypercarbia with laryngeal mask airway.
However, the concerns of aspiration of gastric contents and other potential complications remain.
A study by Ambesh et al. found significantly more complications with the laryngeal mask airway compared with an endotracheal tube.
Therefore, more studies are needed to address both the efficacy and safety of this approach before recommendations for laryngeal mask airway management for percutaneous tracheostomy can be made.
Assist Endotracheal Intubation Using Flexible Bronchoscopy
Alternative and contingent options are needed to deal with a difficult airway. As mentioned, the intubating laryngeal mask airway has provided an important option for the clinician.
Although laryngeal mask airways are designed as blind intubation devices, newer approaches have been reported to incorporate the flexible bronchoscope for airway management.
For example, the aintree catheter has been incorporated with the proseal laryngeal mask airway to facilitate endotracheal intubation.
After laryngeal mask airway placement, a bronchoscope equipped with the Aintree catheter is directed into the laryngeal mask airway and through the glottis, and then the endotracheal tube is placed using the catheter as a guide.
In pediatric literature, the combination of the flexible bronchoscope with the laryngeal mask airway to intubate the difficult airway has also been described.
Pre or outside the hospital airway
In the field, securing an airway can be paramount. In the “can’t ventilate, can’t intubate” situation, laryngeal mask airway can be life saving.
A laryngeal mask airway can be used for transport until a definitive airway can be obtained.
An intubating laryngeal mask airway can also be used, as a 6mm ID endotracheal tube can easily be inserted.
As mentioned above, the basics of laryngeal mask airway placement are easily mastered with limited training.
Case reports of children with laryngotracheoesophageal clefts and an infected neonate showed the ability to use the laryngeal mask airway for interhospital transport.
During cardiopulmonary resuscitation (CPR), the first part of the secondary study includes securing an airway device as soon as possible.
In the event that the patient cannot be easily ventilated or intubated, or if the patient is in a difficult position where there is limited space to perform a direct laryngoscopy, the laryngeal mask airway can be a backup device to ensure correctness. airway.
Keller et al. It demonstrated an increase in vertebral pressure in a cadaver study using a laryngeal mask airway compared to an endotracheal tube.
They suggest that a laryngeal mask airway should be used with caution on an unstable neck. Todd and Traynelis question the clinical validity of the study.
Since its introduction, the laryngeal mask airway has offered anesthesiologists and other physicians who manage the airways as an important option in their arsenal.
Different designs give specific advantages for different clinical scenarios. Insertion is easily learned, and non-physicians are able to secure an airway with proper training.
Knowing the indications and contraindications of using a laryngeal mask airway is essential for its proper use, since complications are different from endotracheal intubations due to its inherent design and position as a supraglottic airway.
Its applications are growing with its recognized benefits, in outpatient, inpatient and critical care settings.
Increasing recognition of the applications of the laryngeal mask airway should expand their role in airway management for the anesthesiologist and bronchoscopist.