Laryngoscopy
Encyclopedia
Laryngoscopy is a medical procedure that is used to obtain a view of the vocal folds
and the glottis
. Laryngoscopy may be performed to facilitate tracheal intubation
during general anesthesia or cardiopulmonary resuscitation
or for procedures on the larynx
or other parts of the upper tracheobronchial tree
.
Direct laryngoscopy is carried out (usually) with the patient
lying on his or her back; the laryngoscope is inserted into the mouth
on the right side and flipped to the left to trap and move the tongue
out of the line of sight, and, depending on the type of blade used, inserted either anterior or posterior to the epiglottis
and then lifted with an upwards and forward motion ("away from you and towards the roof "). This move makes a view of the glottis
possible. There are at least ten different types of laryngoscope used for this procedure, each of which has a specialized use for the otolaryngologist. This procedure is most often employed in direct diagnostic laryngoscopy with biopsy. It is extremely uncomfortable and is not typically performed on conscious patient
s, or on patients with an intact gag reflex
.
Indirect laryngoscopy is performed whenever the provider visualizes the patient's vocal cords by a means other than obtaining a direct line of sight. For the purpose of intubation, this is facilitated by fiberoptic bronchoscopes, video laryngoscopes, fiberoptic stylets and mirror or prism optically-enhanced laryngoscopes.
Some historians (for example, Morell Mackenzie
) credit Benjamin Guy Babington
(1794–1866), who called his device the "glottiscope", with the invention of the laryngoscope. Philipp von Bozzini
(1773–1809) and Garignard de la Tour were other early physicians to use mouth mirror
s to inspect the oropharynx
and hypopharynx
.
In 1854, a Spanish
vocal pedagogist
named Manuel García
(1805–1906) became the first man to view the functioning glottis and larynx in a living human. García developed a tool that used two mirrors for which the Sun served as an external light source. Using this device, he was able to observe the function of his own glottic apparatus and the uppermost portion of his trachea. He presented his findings at the Royal Society of London
in 1855.
All previous observations of the glottis and larynx had been performed under indirect vision (using mirrors) until 23 April 1895, when Alfred Kirstein (1863–1922) of Germany first described direct visualization of the vocal cords. Kirstein performed the first direct laryngoscopy in Berlin, using an esophagoscope he had modified for this purpose; he called this device an autoscope. It is believed that the death in 1888 of Emperor Frederick III
motivated Kirstein to develop the autoscope.
In 1913, Chevalier Jackson
was the first to report a high rate of success for the use of direct laryngoscopy as a means to intubate the trachea. Jackson introduced a new laryngoscope blade that had a light source at the distal tip, rather than the proximal light source used by Kirstein. This new blade incorporated a component that the operator could slide out to allow room for passage of an endotracheal tube or bronchoscope.
That same year, Henry H. Janeway (1873–1921) published results he had achieved using another new laryngoscope he had recently developed. An American anesthesiologist practicing at Bellevue Hospital
in New York City
, Janeway believed that direct intratracheal insufflation
of volatile anesthetics would provide improved conditions for surgery of the nose, mouth and throat
. With this in mind, he developed a laryngoscope designed for the sole purpose of tracheal intubation. Similar to Jackson's device, Janeway's instrument incorporated a distal light source. Unique however was the inclusion of batteries
within the handle, a central notch in the blade for maintaining the tracheal tube in the midline of the oropharynx during intubation, and a slight curve to the distal tip of the blade to help guide the tube through the glottis. The success of this design led to its subsequent use in other types of surgery. Janeway was thus instrumental in popularizing the widespread use of direct laryngoscopy and tracheal intubation in the practice of anesthesiology.
s.
, and this design is still the standard pattern veterinary laryngoscopes are based upon; however the blade is difficult to control in adult humans and can cause pressure on the vagus nerve
, which can cause unexpected cardiac arrhythmias to spontaneously occur in adults.
Two basic styles of laryngoscope blade are currently commercially available: the curved blade and the straight blade. The Macintosh
blade is the most widely used of the curved laryngoscope blades, while the Miller blade is the most popular style of straight blade. Both Miller and Macintosh laryngoscope blades are available in sizes 0 (neonatal) through 4 (large adult). There are many other styles of curved and straight blades (e.g., Phillips, Robertshaw, Sykes, Wisconsin, Wis-Hipple, etc.) with accessories such as mirrors for enlarging the field of view and even ports for the administration of oxygen
. These specialty blades are primarily designed for use by anesthetist
s, most commonly in the operating room.
The Macintosh blade is positioned in the vallecula
, anterior to the epiglottis
, lifting it out of the visual pathway, while the Miller blade is positioned posterior to the epiglottis, trapping it while exposing the glottis and vocal folds. Incorrect usage can cause trauma
to the front incisor
s; the correct technique is to displace the chin
upwards and forward at the same time, not to use the blade as a lever with the teeth serving as the fulcrum.
The Miller, Wisconsin, Wis-Hipple, and Robertshaw blades are commonly used for infants. It is easier to visualize the glottis using these blades than the Macintosh blade in infants, due to the larger size of the epiglottis relative to that of the glottis.
viewing laryngoscopes such as the flexible fiberoptic bronchoscope
. The flexible fiberoptic bronchoscope or rhinoscope
can be used for office-based diagnostics or for tracheal intubation. The patient can remain conscious during the procedure, so that the vocal folds
can be observed during phonation
. Surgical instruments passed through the scope can be used for performing procedures such as biopsies of suspicious masses. These instruments have become indispensable within the otolaryngology
, pulmonology
and anesthesia
communities.
Other available fiberoptic devices include the Bullard scope, UpsherScope, and the WuScope. These devices are widely employed for tracheal intubation, especially in the setting of the difficult intubation (see below).
viewing laryngoscopes, such as the fiberscope
, Bullard scope, Upsher scope, and the WuScope. Though these devices can be effective alternatives to direct laryngoscopy, they each have certain limitations, and none of them is effective under all circumstances. One important limitation commonly associated with these devices is fogging of the lens
. In an attempt to address some of these limitations, Dr. Jon Berall, a New York City
internist
and emergency medicine
physician
, designed the camera screen straight video laryngoscope in 1998.
The Digital Revolution
has brought new technology to the practice of tracheal intubation. Several manufacturers have developed video laryngoscopes which employ digital technology such as the CMOS
active pixel sensor
(CMOS APS) to generate a view of the glottis so that the trachea may be intubated. The Glidescope video laryngoscope is one example of such a device. Other examples include the McGrath laryngoscope, Daiken Medical Coopdech C-scope vlp-100, the Storz C-Mac, Pentax AWS, and the Berci DCI laryngoscopes.
John Allen Pacey) became the first commercially available video laryngoscope. It incorporates a high resolution
digital camera, connected by a video cable to a high resolution LCD monitor
. It can be used for tracheal intubation to provide controlled mechanical ventilation
, as well as for removal of foreign bodies from the airway. The Glidescope owes its superior results to a combination of five key factors:
Tracheal intubation with the GlideScope can be facilitated by the use of the Verathon Stylet, a rigid stylet that is curved to follow the 60° angulation of the blade. To achieve a 99% successful rate of intubation with the GlideScope requires the operator to acquire a new skill set with this stylet.
In a 2003 study, the authors noted that the GlideScope provided adequate vision of the glottis (Cormack and Lehane grade I-II) even when the oral, pharyngeal and laryngeal axes could not be optimally aligned due to the presence of a cervical collar
. Despite this significant limitation, the average time to intubate the trachea with the GlideScope was only 38 seconds. In 2005, the first major clinical study comparing the Glidescope to the conventional laryngoscope was published. In 133 patients in whom both Glidescope and conventional laryngoscopy were performed, excellent or good laryngeal exposure was obtained in 124/133 (93%) of Glidescope laryngoscopy patients, compared with only 98/133 (74%) of patients in whom conventional laryngoscopy was used. Intubation was successful in 128/133 (96%) of Glidescope laryngoscopy patients. These early results suggest that this device may be a useful alternative in the management of difficult tracheal intubation.
The Verathon design team later produced the Ranger Video Laryngoscope for a United States Air Force
requirement that is now rolling forward into EMS
and military use. The Cobalt series of Glidescopes then introduced a single use variant that encompasses weights from 1000 grams to morbid obesity and is successful in many airway syndromes as well. The Glidescope Ranger is a variant designed for use in pre-hospital airway management including air, land, and sea applications. This device weighs 1.5 pounds, and is waterproof as well as airworthy to 20,000 feet altitude. The Glidescope Cobalt is a variant that has a reusable video camera with light-emitting core which has a disposable or single use external shell for prevention of cross infection.
In August 2009, the team at Verathon collaborated with Professor John Sakles from the University of Arizona Emergency Department in achieving the world's first tracheal intubation conducted with the assistance of telemedicine
technology. During this demonstration, Dr. Sakles and the University of Arizona Telemedicine service guided physicians in a rural
hospital
as they performed a tracheal intubation using the Glidescope.
on the handle and or channels to assist in guiding the endotracheal tube into the trachea. The superior performance of video laryngoscopes in airway management where cervical spine injury is possible has raised the question of whether these scopes should supersede direct laryngoscopy in routine airway management.
(used as a conduit for endotracheal tube placement), the lighted stylet, and the AirTraq. Due to the widespread availability of such devices, the technique of blind digital intubation of the trachea is rarely practiced today, though it may still be useful in emergency situations under austere conditions such as natural or man-made disaster
s.
Vocal folds
The vocal folds, also known commonly as vocal cords, are composed of twin infoldings of mucous membrane stretched horizontally across the larynx...
and the glottis
Glottis
The glottis is defined as the combination of the vocal folds and the space in between the folds .-Function:...
. Laryngoscopy may be performed to facilitate tracheal intubation
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...
during general anesthesia or cardiopulmonary resuscitation
Cardiopulmonary resuscitation
Cardiopulmonary resuscitation is an emergency procedure which is performed in an effort to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person in cardiac arrest. It is indicated in those who are unresponsive...
or for procedures on the larynx
Larynx
The larynx , commonly called the voice box, is an organ in the neck of amphibians, reptiles and mammals involved in breathing, sound production, and protecting the trachea against food aspiration. It manipulates pitch and volume...
or other parts of the upper tracheobronchial tree
Tracheobronchial tree
The tracheobronchial tree is the structure from the trachea, bronchi, and bronchioles that forms the airways that supply air to the lungs. It is within the neck and the chest. The structure looks like a tree because the trachea splits into the right and left mainstem bronchi, which "branch" into...
.
Direct laryngoscopy is carried out (usually) with the patient
Patient
A patient is any recipient of healthcare services. The patient is most often ill or injured and in need of treatment by a physician, advanced practice registered nurse, veterinarian, or other health care provider....
lying on his or her back; the laryngoscope is inserted into the mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
on the right side and flipped to the left to trap and move the tongue
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
out of the line of sight, and, depending on the type of blade used, inserted either anterior or posterior to the epiglottis
Epiglottis
The epiglottis is a flap that is made of elastic cartilage tissue covered with a mucous membrane, attached to the entrance of the larynx. It projects obliquely upwards behind the tongue and the hyoid bone, pointing dorsally. The term, like tonsils, is often incorrectly used to refer to the uvula...
and then lifted with an upwards and forward motion ("away from you and towards the roof "). This move makes a view of the glottis
Glottis
The glottis is defined as the combination of the vocal folds and the space in between the folds .-Function:...
possible. There are at least ten different types of laryngoscope used for this procedure, each of which has a specialized use for the otolaryngologist. This procedure is most often employed in direct diagnostic laryngoscopy with biopsy. It is extremely uncomfortable and is not typically performed on conscious patient
Patient
A patient is any recipient of healthcare services. The patient is most often ill or injured and in need of treatment by a physician, advanced practice registered nurse, veterinarian, or other health care provider....
s, or on patients with an intact gag reflex
Gag reflex
The pharyngeal reflex or gag reflex is a reflex contraction of the back of the throat, evoked by touching the soft palate or sometimes the back of the tongue. It prevents something from entering the throat except as part of normal swallowing and helps prevent choking...
.
Indirect laryngoscopy is performed whenever the provider visualizes the patient's vocal cords by a means other than obtaining a direct line of sight. For the purpose of intubation, this is facilitated by fiberoptic bronchoscopes, video laryngoscopes, fiberoptic stylets and mirror or prism optically-enhanced laryngoscopes.
History
Morell Mackenzie
Sir Morell Mackenzie was a British physician, one of the pioneers of laryngology in the United Kingdom.-Biography:...
) credit Benjamin Guy Babington
Benjamin Guy Babington
Benjamin Guy Babington was an English physician and epidemiologist.He was born on 5 March 1794, the son of the physician and mineralogist William Babington and his wife, Martha Elizabeth Babington....
(1794–1866), who called his device the "glottiscope", with the invention of the laryngoscope. Philipp von Bozzini
Philipp Bozzini
Philipp Bozzini was born in Mainz, Germany. On June 12, 1797 he was awarded the degree of doctor of medicine. From 1804 onwards, Bozzini devoted himself virtually completely to develop his instrument, Lichtleiter or "Light Conductor", a primitive endoscope to allow for inspecting the ear, urethra,...
(1773–1809) and Garignard de la Tour were other early physicians to use mouth mirror
Mouth mirror
A mouth mirror or dentist's mirror is an instrument used in dentistry. The head of the mirror is usually round, and the most common sizes used are the No. 4 and No. 5. A No. 2 is sometimes used when a smaller mirror is needed, such as when working on back teeth with a dental dam in place. The...
s to inspect the oropharynx
Oropharynx
The Oropharynx reaches from the Uvula to the level of the hyoid bone.It opens anteriorly, through the isthmus faucium, into the mouth, while in its lateral wall, between the two palatine arches, is the palatine tonsil....
and hypopharynx
Hypopharynx
In human anatomy, the hypopharynx is the bottom part of the pharynx, and is the part of the throat that connects to the esophagus....
.
In 1854, a Spanish
Spanish people
The Spanish are citizens of the Kingdom of Spain. Within Spain, there are also a number of vigorous nationalisms and regionalisms, reflecting the country's complex history....
vocal pedagogist
Vocal pedagogy
Vocal pedagogy is the study of the art and science of voice instruction. It is used in the teaching of singing and assists in defining what singing is, how singing works, and how proper singing technique is accomplished....
named Manuel García
Manuel Patricio Rodríguez García
Manuel Patricio Rodríguez García , was a Spanish singer, music educator, and vocal pedagogue.-Biography:García was born on 17 March 1805 in the town of Zafra in Badajoz Province, Spain. His father was singer and teacher Manuel del Pópulo Vicente Rodriguez García...
(1805–1906) became the first man to view the functioning glottis and larynx in a living human. García developed a tool that used two mirrors for which the Sun served as an external light source. Using this device, he was able to observe the function of his own glottic apparatus and the uppermost portion of his trachea. He presented his findings at the Royal Society of London
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...
in 1855.
All previous observations of the glottis and larynx had been performed under indirect vision (using mirrors) until 23 April 1895, when Alfred Kirstein (1863–1922) of Germany first described direct visualization of the vocal cords. Kirstein performed the first direct laryngoscopy in Berlin, using an esophagoscope he had modified for this purpose; he called this device an autoscope. It is believed that the death in 1888 of Emperor Frederick III
Frederick III, German Emperor
Frederick III was German Emperor and King of Prussia for 99 days in 1888, the Year of the Three Emperors. Friedrich Wilhelm Nikolaus Karl known informally as Fritz, was the only son of Emperor William I and was raised in his family's tradition of military service...
motivated Kirstein to develop the autoscope.
In 1913, Chevalier Jackson
Chevalier Jackson
Chevalier Jackson was a laryngologist.Jackson was born in Pittsburgh, Pennsylvania. He went to school at the Western University of Pennsylvania from 1879 to 1883, and received his MD from Jefferson Medical College. He also studied laryngology in England.His work reduced the risks involved in a...
was the first to report a high rate of success for the use of direct laryngoscopy as a means to intubate the trachea. Jackson introduced a new laryngoscope blade that had a light source at the distal tip, rather than the proximal light source used by Kirstein. This new blade incorporated a component that the operator could slide out to allow room for passage of an endotracheal tube or bronchoscope.
That same year, Henry H. Janeway (1873–1921) published results he had achieved using another new laryngoscope he had recently developed. An American anesthesiologist practicing at Bellevue Hospital
Bellevue Hospital Center
Bellevue Hospital Center, most often referred to as "Bellevue", was founded on March 31, 1736 and is the oldest public hospital in the United States. Located on First Avenue in the Kips Bay neighborhood of Manhattan, New York City, Bellevue is famous from many literary, film and television...
in New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
, Janeway believed that direct intratracheal insufflation
Insufflation (medicine)
Insufflation is the practice of inhaling a substance. Insufflation has limited medical use, but is a common route of administration with many respiratory drugs used to treat conditions in the lungs and paranasal sinus .The technique is common for many recreational drugs and is also used for some...
of volatile anesthetics would provide improved conditions for surgery of the nose, mouth and throat
Otolaryngology
Otolaryngology or ENT is the branch of medicine and surgery that specializes in the diagnosis and treatment of ear, nose, throat, and head and neck disorders....
. With this in mind, he developed a laryngoscope designed for the sole purpose of tracheal intubation. Similar to Jackson's device, Janeway's instrument incorporated a distal light source. Unique however was the inclusion of batteries
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
within the handle, a central notch in the blade for maintaining the tracheal tube in the midline of the oropharynx during intubation, and a slight curve to the distal tip of the blade to help guide the tube through the glottis. The success of this design led to its subsequent use in other types of surgery. Janeway was thus instrumental in popularizing the widespread use of direct laryngoscopy and tracheal intubation in the practice of anesthesiology.
Applications
- Helps in intubation during the administration of general anaesthesia or for mechanical ventilation.
- Detects causes of voice problems, such as breathing voice, hoarse voice, weak voice, or no voice.
- Detects causes of throat and ear pain.
- Evaluates difficulty in swallowing : a persistent sensation of lump in the throat, or mucous with blood.
- Detects strictures or injury to the throat, or obstructive masses in the airway.
Conventional laryngoscope
The vast majority of tracheal intubations involve the use of a viewing instrument of one type or another. Since its introduction by Kirstein in 1895, the conventional laryngoscope has been the most popular device used for this purpose. Today, the conventional laryngoscope consists of a handle containing batteries with a light source, and a set of interchangeable bladeBlade
A blade is that portion of a tool, weapon, or machine with a cutting edge and/or a pointed tip that is designed to cut and/or puncture, stab, slash, chop, slice, thrust, or scrape animate or inanimate surfaces or materials...
s.
Laryngoscope blades
Early laryngoscopes used a straight "Magill Blade"Ivan Magill
Sir Ivan Whiteside Magill was an Irish born anaesthetist who is famous for his involvement in much of the innovation and development in modern anaesthesia....
, and this design is still the standard pattern veterinary laryngoscopes are based upon; however the blade is difficult to control in adult humans and can cause pressure on the vagus nerve
Vagus nerve
The vagus nerve , also called pneumogastric nerve or cranial nerve X, is the tenth of twelve paired cranial nerves...
, which can cause unexpected cardiac arrhythmias to spontaneously occur in adults.
Two basic styles of laryngoscope blade are currently commercially available: the curved blade and the straight blade. The Macintosh
Robert Reynolds Macintosh
Sir Robert Reynolds Macintosh was a New Zealand-born anaesthetist. He was the first Professor of Anaesthetics outside United States.-Early life:...
blade is the most widely used of the curved laryngoscope blades, while the Miller blade is the most popular style of straight blade. Both Miller and Macintosh laryngoscope blades are available in sizes 0 (neonatal) through 4 (large adult). There are many other styles of curved and straight blades (e.g., Phillips, Robertshaw, Sykes, Wisconsin, Wis-Hipple, etc.) with accessories such as mirrors for enlarging the field of view and even ports for the administration of 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...
. These specialty blades are primarily designed for use by anesthetist
Anesthesiologist
An anesthesiologist or anaesthetist is a physician trained in anesthesia and peri-operative medicine....
s, most commonly in the operating room.
The Macintosh blade is positioned in the vallecula
Vallecula
-Types:There are a variety of valleculae in the human body, including one between the hemispheres of the brain, on the inferior surface of the cerebellum, in which the medulla oblongata is located...
, anterior to the epiglottis
Epiglottis
The epiglottis is a flap that is made of elastic cartilage tissue covered with a mucous membrane, attached to the entrance of the larynx. It projects obliquely upwards behind the tongue and the hyoid bone, pointing dorsally. The term, like tonsils, is often incorrectly used to refer to the uvula...
, lifting it out of the visual pathway, while the Miller blade is positioned posterior to the epiglottis, trapping it while exposing the glottis and vocal folds. Incorrect usage can cause trauma
Dental trauma
Dental trauma refers to trauma to the face, mouth, and especially the teeth lips and periodontium. The study of dental trauma is called dental traumatology.- Types :* Tooth fractures**Enamel infraction**Enamel fracture**Enamel-dentine fracture...
to the front incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s; the correct technique is to displace the chin
Chin
In the human anatomy, the chin is the lowermost part of the face.It is formed by the lower front of the mandible.People show a wide variety of chin structures. See Cleft chin....
upwards and forward at the same time, not to use the blade as a lever with the teeth serving as the fulcrum.
The Miller, Wisconsin, Wis-Hipple, and Robertshaw blades are commonly used for infants. It is easier to visualize the glottis using these blades than the Macintosh blade in infants, due to the larger size of the epiglottis relative to that of the glottis.
| Blade | Named for | Year introduced | Comments |
|---|---|---|---|
| Cranwall | George D. Cranton and Barry L. Wall | 1963 | straight, no flange |
| Jackson | Chevalier Jackson Chevalier Jackson Chevalier Jackson was a laryngologist.Jackson was born in Pittsburgh, Pennsylvania. He went to school at the Western University of Pennsylvania from 1879 to 1883, and received his MD from Jefferson Medical College. He also studied laryngology in England.His work reduced the risks involved in a... |
straight | |
| Janeway | Henry H. Janeway | straight | |
| Reduced Flange (RF Mac) | George D. Cranton | 1999 | curved reduced flange at heel |
| Macintosh | Robert Reynolds Macintosh Robert Reynolds Macintosh Sir Robert Reynolds Macintosh was a New Zealand-born anaesthetist. He was the first Professor of Anaesthetics outside United States.-Early life:... |
1943 | curved |
| Magill | Ivan Magill Ivan Magill Sir Ivan Whiteside Magill was an Irish born anaesthetist who is famous for his involvement in much of the innovation and development in modern anaesthesia.... |
1921 | straight |
| Miller | Robert A. Miller | 1941 | straight |
| Parrott | C.M. Parrott | 1951 | curved |
| Phillips | 1973 | straight | |
| Robertshaw | straight | ||
| Siker | 1956 | curved, with integrated mirror | |
| Soper | R.I. Soper | 1947 | straight |
| Wis-Hipple | straight | ||
| Wisconsin | straight | ||
Fiberoptic laryngoscopes
Besides the conventional laryngoscopes, many other devices have been developed as alternatives to direct laryngoscopy. These include a number of indirect fiberopticOptical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...
viewing laryngoscopes such as the flexible fiberoptic bronchoscope
Fiberscope
A fiberscope is a flexible fiber optic bundle with an eyepiece at one end, and a lens at the other. It is used for inspection work, often to examine small components in tightly packed equipment, when the inspector cannot easily access the part requiring inspection.The lens is often a wide-angle...
. The flexible fiberoptic bronchoscope or rhinoscope
Rhinoscope
A rhinoscope is a thin, tube-like instrument used to examine the inside of the nose. A rhinoscope has a light and a lens for viewing and may have a tool to remove tissue.- External links :...
can be used for office-based diagnostics or for tracheal intubation. The patient can remain conscious during the procedure, so that the vocal folds
Vocal folds
The vocal folds, also known commonly as vocal cords, are composed of twin infoldings of mucous membrane stretched horizontally across the larynx...
can be observed during phonation
Phonation
Phonation has slightly different meanings depending on the subfield of phonetics. Among some phoneticians, phonation is the process by which the vocal folds produce certain sounds through quasi-periodic vibration. This is the definition used among those who study laryngeal anatomy and physiology...
. Surgical instruments passed through the scope can be used for performing procedures such as biopsies of suspicious masses. These instruments have become indispensable within the otolaryngology
Otolaryngology
Otolaryngology or ENT is the branch of medicine and surgery that specializes in the diagnosis and treatment of ear, nose, throat, and head and neck disorders....
, pulmonology
Pulmonology
In medicine, pulmonology is the specialty that deals with diseases of the respiratory tract and respiratory disease. It is called chest medicine and respiratory medicine in some countries and areas...
and anesthesia
Anesthesia
Anesthesia, or anaesthesia , traditionally meant the condition of having sensation blocked or temporarily taken away...
communities.
Other available fiberoptic devices include the Bullard scope, UpsherScope, and the WuScope. These devices are widely employed for tracheal intubation, especially in the setting of the difficult intubation (see below).
Video laryngoscope
The conventional direct laryngoscope uses a line of sight provided by a rigid viewing instrument with a light on the blade or intra-oral portion which requires a direct view of the target larynx; this view is clearly seen in 80-90% of attempts. The frequent failure of direct laryngoscopy to provide an adequate view for tracheal intubation led to the development of alternative devices such as the lighted stylet, and a number of indirect fiberopticOptical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...
viewing laryngoscopes, such as the fiberscope
Fiberscope
A fiberscope is a flexible fiber optic bundle with an eyepiece at one end, and a lens at the other. It is used for inspection work, often to examine small components in tightly packed equipment, when the inspector cannot easily access the part requiring inspection.The lens is often a wide-angle...
, Bullard scope, Upsher scope, and the WuScope. Though these devices can be effective alternatives to direct laryngoscopy, they each have certain limitations, and none of them is effective under all circumstances. One important limitation commonly associated with these devices is fogging of the lens
Lens (optics)
A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
. In an attempt to address some of these limitations, Dr. Jon Berall, a New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
internist
Internal medicine
Internal medicine is the medical specialty dealing with the prevention, diagnosis, and treatment of adult diseases. Physicians specializing in internal medicine are called internists. They are especially skilled in the management of patients who have undifferentiated or multi-system disease processes...
and emergency medicine
Emergency medicine
Emergency medicine is a medical specialty in which physicians care for patients with acute illnesses or injuries which require immediate medical attention. While not usually providing long-term or continuing care, emergency medicine physicians diagnose a variety of illnesses and undertake acute...
physician
Physician
A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...
, designed the camera screen straight video laryngoscope in 1998.
The Digital Revolution
Information Age
The Information Age, also commonly known as the Computer Age or Digital Age, is an idea that the current age will be characterized by the ability of individuals to transfer information freely, and to have instant access to knowledge that would have been difficult or impossible to find previously...
has brought new technology to the practice of tracheal intubation. Several manufacturers have developed video laryngoscopes which employ digital technology such as the CMOS
CMOS
Complementary metal–oxide–semiconductor is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits...
active pixel sensor
Active pixel sensor
An active-pixel sensor is an image sensor consisting of an integrated circuit containing an array of pixel sensors, each pixel containing a photodetector and an active amplifier. There are many types of active pixel sensors including the CMOS APS used most commonly in cell phone cameras, web...
(CMOS APS) to generate a view of the glottis so that the trachea may be intubated. The Glidescope video laryngoscope is one example of such a device. Other examples include the McGrath laryngoscope, Daiken Medical Coopdech C-scope vlp-100, the Storz C-Mac, Pentax AWS, and the Berci DCI laryngoscopes.
Glidescope
In 2001, the Glidescope (designed by vascular and general surgeonGeneral surgery
General surgery, despite its name, is a surgical specialty that focuses on abdominal organs, e.g., intestines including esophagus, stomach, small bowel, colon, liver, pancreas, gallbladder and bile ducts, and often the thyroid gland . They also deal with diseases involving the skin, breast, soft...
John Allen Pacey) became the first commercially available video laryngoscope. It incorporates a high resolution
Image resolution
Image resolution is an umbrella term that describes the detail an image holds. The term applies to raster digital images, film images, and other types of images. Higher resolution means more image detail....
digital camera, connected by a video cable to a high resolution LCD monitor
TFT LCD
Thin film transistor liquid crystal display is a variant of liquid crystal display which uses thin-film transistor technology to improve image quality . TFT LCD is one type of Active matrix LCD, though all LCD-screens are based on TFT active matrix addressing...
. It can be used for tracheal intubation to provide controlled 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...
, as well as for removal of foreign bodies from the airway. The Glidescope owes its superior results to a combination of five key factors:
- The steep 60-degree angulation of its blade improves the view of the glottis by reducing the requirement for anterior displacement of the tongue.
- The CMOS APS digital camera is located at the point of angulation of the blade (rather than at the tip). This placement allows the operator to more effectively view the field in front of the camera.
- The video camera is recessed for protection from blood and secretions which might otherwise obstruct the view.
- The video camera has a relatively wide viewing angle of 50 degrees.
- The heated lens innovation helps to prevent fogging of the lens, which might otherwise obscure the view.
Tracheal intubation with the GlideScope can be facilitated by the use of the Verathon Stylet, a rigid stylet that is curved to follow the 60° angulation of the blade. To achieve a 99% successful rate of intubation with the GlideScope requires the operator to acquire a new skill set with this stylet.
In a 2003 study, the authors noted that the GlideScope provided adequate vision of the glottis (Cormack and Lehane grade I-II) even when the oral, pharyngeal and laryngeal axes could not be optimally aligned due to the presence of a cervical collar
Cervical collar
A cervical collar is an orthopedic medical device used to support a patient's neck and head. It is also used by emergency personnel for victims of traumatic head or neck injuries, and can be used to treat chronic medical conditions....
. Despite this significant limitation, the average time to intubate the trachea with the GlideScope was only 38 seconds. In 2005, the first major clinical study comparing the Glidescope to the conventional laryngoscope was published. In 133 patients in whom both Glidescope and conventional laryngoscopy were performed, excellent or good laryngeal exposure was obtained in 124/133 (93%) of Glidescope laryngoscopy patients, compared with only 98/133 (74%) of patients in whom conventional laryngoscopy was used. Intubation was successful in 128/133 (96%) of Glidescope laryngoscopy patients. These early results suggest that this device may be a useful alternative in the management of difficult tracheal intubation.
The Verathon design team later produced the Ranger Video Laryngoscope for a United States Air Force
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...
requirement that is now rolling forward into EMS
Emergency medical services
Emergency medical services are a type of emergency service dedicated to providing out-of-hospital acute medical care and/or transport to definitive care, to patients with illnesses and injuries which the patient, or the medical practitioner, believes constitutes a medical emergency...
and military use. The Cobalt series of Glidescopes then introduced a single use variant that encompasses weights from 1000 grams to morbid obesity and is successful in many airway syndromes as well. The Glidescope Ranger is a variant designed for use in pre-hospital airway management including air, land, and sea applications. This device weighs 1.5 pounds, and is waterproof as well as airworthy to 20,000 feet altitude. The Glidescope Cobalt is a variant that has a reusable video camera with light-emitting core which has a disposable or single use external shell for prevention of cross infection.
In August 2009, the team at Verathon collaborated with Professor John Sakles from the University of Arizona Emergency Department in achieving the world's first tracheal intubation conducted with the assistance of telemedicine
Telemedicine
Telemedicine is the use of telecommunication and information technologies in order to provide clinical health care at a distance. It helps eliminate distance barriers and can improve access to medical services that would often not be consistently available in distant rural communities...
technology. During this demonstration, Dr. Sakles and the University of Arizona Telemedicine service guided physicians in a rural
Rural
Rural areas or the country or countryside are areas that are not urbanized, though when large areas are described, country towns and smaller cities will be included. They have a low population density, and typically much of the land is devoted to agriculture...
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....
as they performed a tracheal intubation using the Glidescope.
Other video laryngoscopes
Several types of video laryngoscopes are also currently available, such as the Glidescope, McGrath laryngoscope, Daiken Medical Coopdech C-scope VLP-100, the Storz C-Mac, Pentax AWS, Video Macintosh Intubating Laryngoscope System (VMS), the Berci DCI, and the Copilot VL. These laryngoscopes employ a variety of features such as a monitorVideo monitor
A video monitor also called a broadcast monitor, broadcast reference monitor or just reference monitor, is a display device similar to a television set, used to monitor the output of a video-generating device, such as playout from a video server, IRD, video camera, VCR, or DVD player. It may or...
on the handle and or channels to assist in guiding the endotracheal tube into the trachea. The superior performance of video laryngoscopes in airway management where cervical spine injury is possible has raised the question of whether these scopes should supersede direct laryngoscopy in routine airway management.
Other noninvasive intubation devices
Other "noninvasive" devices which can be employed to assist in tracheal intubation are the laryngeal mask airwayLaryngeal 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...
(used as a conduit for endotracheal tube placement), the lighted stylet, and the AirTraq. Due to the widespread availability of such devices, the technique of blind digital intubation of the trachea is rarely practiced today, though it may still be useful in emergency situations under austere conditions such as natural or man-made disaster
Disaster
A disaster is a natural or man-made hazard that has come to fruition, resulting in an event of substantial extent causing significant physical damage or destruction, loss of life, or drastic change to the environment...
s.