Can J Anesth/J Can Anesth DOI 10.1007/s12630-013-0101-x
SPECIAL ARTICLE
From the Journal archives: Mallampati in two millennia: its impact then and implications now J. Adam Law, MD
Received: 6 October 2013 / Accepted: 18 December 2013 Canadian Anesthesiologists’ Society 2014
Editors’ Note: Classics Revisited Key Articles from the Canadian Journal of Anesthesia Archives: 1954-2013 As part of the Journal’s 60th anniversary Diamond Jubilee Celebration, a number of seminal articles from the Journal archives are highlighted in the Journal’s 61st printed volume and online at: www.springer.com/ 12630. The following article was selected on the basis of its novelty at the time of publication, its scientific merit, and its overall importance to clinical practice: Mallampati SR, Gatt SP, Gugino LD, et al. A clinical sign to predict difficult tracheal intubation: a prospective study. Can Anaesth Soc J 1985; 32: 429-34. Dr. J. Adam Law provides expert commentary on the poor correlation between the oropharyngeal view and ease of tracheal intubation and how, almost 30 years after publication of this article, the Mallampati classification continues to be commonly assessed as part of a comprehensive airway evaluation. Hilary P. Grocott MD, Editor-in-Chief Donald R. Miller MD, Former Editor-in-Chief Overview In the early 1980s, few alternatives were available when difficult direct laryngoscopy was encountered in the J. A. Law, MD (&) Department of Anesthesia, Dalhousie University, QEII Health Sciences Centre, Halifax Infirmary Site, 1796 Summer Street, Halifax, NS B3H 3A7, Canada e-mail: [email protected]
unconscious patient. Until then, to help avoid unanticipated difficult laryngoscopy, the airway evaluation focused on an examination of the bony aspects of patient anatomy, such as the mentohyoid distance. In 1985, Dr. Mallampati et al. published their study on the relationship between the visibility of oropharyngeal structures and the subsequent view obtained during direct laryngoscopy. In so doing, the connection was made between difficult direct laryngoscopy and a base-of-tongue disproportionately large to the volume of the oropharyngeal cavity. Although later clinical trials questioned the sensitivity and positive predicted value suggested by results of the original study, the Mallampati classification continues to be useful as a component of a multivariate airway assessment. In addition, evidence is emerging that a modified Mallampati class 3 or 4 view may correlate with difficult bag-mask ventilation. To date, any studies on alternatives to direct laryngoscopy, such as video laryngoscopy, suggest little correlation between the oropharyngeal view and ease of tracheal intubation with their use. Regardless, almost 30 years later, the Mallampati classification continues to be commonly assessed as part of a comprehensive airway evaluation.
Article summary Authors: Mallampati SR, Gatt SP, Gugino LD, Desai SP, Waraksa B, Freiberger D, Liu PL. Citation: Can Anaesth Soc J 1985; 32: 429-34. Purpose: In a 1983 letter to the editor, Dr. S. Rao Mallampati communicated his observations of a patient who had unexpectedly presented great difficulty with direct laryngoscopy.1 A subsequent examination of the patient revealed normal anatomic features of the head, neck, and teeth, as well as normal temporomandibular joint and neck mobility.
123
J. A. Law
Nevertheless, with the patient’s mouth opened widely and her tongue maximally protruded, the faucial pillars and uvula were concealed by her tongue, and her soft palate was barely visible. In his communication, Mallampati hypothesized that a disproportionately large tongue base would mask visibility of the faucial pillars and uvula on airway examination, and by ‘‘overshadowing the larynx and render[ing] the angle to the larynx more acute’’ during direct laryngoscopy, it might portend difficult direct laryngoscopy.1 In this 1985 publication,2 Dr. Mallampati et al. followed up the letter with their classic prospective study that formally assessed the relationship between the visibility of oropharyngeal structures (faucial pillars, soft palate, and uvula) on examination and subsequent ease or difficulty of direct laryngoscopy. Principal findings: The study included just over 200 surgical patients requiring tracheal intubation. Preoperatively, each patient was examined twice for oropharyngeal visibility by one of 22 clinicians. Patients were assessed in the sitting position with a widely opened mouth and maximally protruded tongue, and they were assigned to one of three classes (Table 1). There were 155 patients assigned to class 1, 40 assigned to class 2, and 15 assigned to class 3. After examination, general anesthesia was induced with conditions optimized by succinylcholine, and the same clinician performed direct laryngoscopy with a Macintosh 3 blade. The laryngeal view obtained was graded using a four-point scale similar (although not identical) to that published earlier by Cormack and Lehane3 (Table 2). No class 1 patients presented difficulty with direct laryngoscopy. In ten of the 40 class 2 patients, only the corniculate cartilages could be exposed, and in four class 2 patients, none of the glottis (including the corniculate cartilages) could be seen. In nine of the 15 class 3 patients, only the corniculate cartilages could be seen, and in five class 3 patients, none of the glottis was visualized. ‘‘Inadequate exposure’’ was defined as a view of only the corniculate cartilages or worse. The result of the Chi square test was significant at P \ 0.001. Conclusions: The authors concluded that a correlation exists between the ability to visualize oropharyngeal structures and ease of direct laryngoscopy. Table 1 Classification of oropharyngeal view Mallampati2
Samsoon and Young6
Class 1
Faucial pillars, soft palate, and uvula Soft palate, fauces, can be visualized uvula, and pillars visible
Class 2
Faucial pillars and soft palate can be Soft palate, fauces, and visualized, but uvula is masked uvula visible by the base of the tongue
Class 3
Only the soft palate can be visualized
Class 4
123
Soft palate and base of uvula visible Soft palate not visible at all
Table 2 Grading of laryngeal exposure Mallampati2
Cormack-Lehane3
Grade 1
Glottis (including anterior Most of the glottis is visible and posterior [no difficulty] commissures) can be fully exposed [adequate exposure]
Grade 2
Glottis can be partly exposed Only the posterior extremity (anterior commissure not of the glottis is visible visualized) [adequate [slight difficulty] exposure]
Grade 3
Glottis cannot be exposed No part of the glottis can be (only corniculate cartilages seen, but only the epiglottis can be visualized) [fairly severe difficulty] [inadequate exposure]
Grade 4
Glottis including corniculate cartilages cannot be exposed [inadequate exposure]
Not even the epiglottis can be exposed [intubation impossible except by special methods]
In the early 1980s, most tracheal intubations were facilitated by direct laryngoscopy. Commonly used alternatives to direct laryngoscopy for tracheal intubation in the anesthetized patient (e.g., Trachlight (Laerdal Medical Corp., Wappingers Falls, NY, USA), Bullard (Circon Corporation, Santa Barbara, CA, USA) laryngoscope or LMA-Fastrach (LMA North America, San Diego, CA, USA) would not appear until the 1990s, and video laryngoscopy was almost two decades away. At least in North America, the Eschmann tracheal tube introducer (‘‘bougie’’) was not in common use as an adjunct to direct laryngoscopy, which meant a poor laryngoscopic view would often result in a failed intubation attempt. If maneuvers such as external laryngeal manipulation or an exaggerated head lift failed to reveal the larynx during direct laryngoscopy, blind attempts to ‘‘hook’’ a styleted endotracheal tube into the trachea beneath an obscuring epiglottis would often follow. This approach met with variable success, and prolonged attempts at tracheal intubation by multiple operators would sometimes ensue,4 an approach that is now known to be detrimental to the patient.5 At the time, often the only alternative means of tracheal intubation in the unconscious patient was the flexible fibreoptic bronchoscope. Issues could be encountered with this option, including collapsing soft tissues, blood and secretions in an airway already subjected to multiple intubation attempts, and variable operator skills. With so few effective options for failed intubation by direct laryngoscopy, it is little surprise that Mallampati and others were motivated to identify patients likely to present significant difficulty with direct laryngoscopy under general anesthesia. Once such patients were identified, they could be considered for ‘‘awake’’ tracheal intubation
Key article from the journal archives Figure The modified Mallampati classification of oropharyngeal view. Reproduced with permission from: Samsoon GL, Young JR. Difficult tracheal intubation: a retrospective study. Anaesthesia 1987; 42: 487-90
or other options such as a regional anesthetic technique. Awake intubation would most likely be performed with the same flexible fibreoptic bronchoscope that could be used in an unconscious patient, but in the awake patient, there would be additional benefits, including a protected, patent airway through which to navigate and maintenance of spontaneous ventilation. As referenced in the Mallampati paper, earlier published reports had already begun to address the prediction of difficult direct laryngoscopy. Several of these studies concluded that bony constraints of the mandible and upper cervical spine could cause difficulty; however, they made no direct association between limited dimensions of the mandible and difficulty with tongue retraction during laryngoscopy. In his prescient 1985 paper, Mallampati was one of the first researchers to make the connection between difficult direct laryngoscopy and a base-of-tongue disproportionately large to the volume of the oropharyngeal cavity.2 Samsoon and Young published an article soon after the Mallampati study.6 In their study, obstetrical and other surgical patients with previously failed tracheal intubation were recalled for assessment. Samsoon and Young modified the scale published by Mallampati et al. by adding a fourth class of oropharyngeal view in which no aspect of the soft palate was visible. In their series, all 12 patients who had experienced failed tracheal intubation on the basis of difficult (Cormack-Lehane grades 3 and 4) direct laryngoscopy were subsequently found to have a class 4 oropharyngeal view on examination.6 Although small numbers were involved and the study was retrospective, the Samsoon and Young paper continues to be frequently referenced alongside the Mallampati study, and indeed, the term ‘‘modified Mallampati’’ is often used to describe the now commonly used four-view oropharyngeal classification. To this day, when the oropharyngeal view is described or studied, the accompanying pictorial diagram is generally the one originating from the Samsoon study (Figure).
Since 1985, many more studies have assessed the efficacy of the modified or original Mallampati classification in predicting difficult laryngoscopy and/or intubation, either on its own or as a component of multivariate airway assessments. A number of meta-analyses can now be added to this inventory.7,8 Most study results concur that both sensitivity and positive predicted value are limited when a modified Mallampati class 3 or 4 oropharyngeal view is used as a sole anatomic predictor, meaning that a difficult laryngoscopy or intubation situation does not consistently ensue. Conversely, a modified Mallampati class 1 or 2 more specifically reassures the clinician that easy laryngoscopy/intubation will follow. In all probability, it is reasonable to state that few clinicians would ever rely on only a single anatomic feature to predict difficult laryngoscopy or intubation. Indeed, studies of multivariate airway evaluations (many of which include the Mallampati assessment) do indicate higher sensitivity and specificity figures.9-11 Interestingly, even the original 1985 Mallampati study documents that subject patients’ head and neck mobility was also examined during their airway assessments. Beyond sensitivity concerns, the modified Mallampati classification has been criticized for poor inter-observer reliability12 and potential changes in oropharyngeal view with phonation or patient position.13 The original study had multiple assessors, and bias may have occurred for each subject by having the same clinician rate both oropharyngeal and laryngoscopic views. Furthermore, it has been observed that the study would have resulted in sensitivity and positive predicted value figures more congruent with subsequent clinical trials if it had not included a ‘‘corniculates-only’’ view (i.e., CormackLehane grade 2b)14 in the ‘‘difficult orotracheal intubation’’ group.15 Nevertheless, when published in 1985, the Mallampati study helped increase awareness of the utility of an airway evaluation and paved the way for further studies on anatomic predictors of difficult direct laryngoscopy.
123
J. A. Law
In contemporary airway management practice, emphasis is appropriately placed on patient oxygenation rather than on tracheal intubation alone. Accordingly, a complete airway evaluation also seeks predictors of difficulty with fall-back oxygenation options such as bag-mask ventilation, use of a supraglottic device, and even surgical airway.16 It turns out that a modified Mallampati class 3 and/or 4 has also been identified as a predictor of difficult and/or impossible bag-mask ventilation.17-19 This is significant, as the combination of predicted difficulty with both direct laryngoscopy/ intubation and bag-mask ventilation may favour awake tracheal intubation in some circumstances. Fortunately, a high modified Mallampati class is not correlated with difficulty inserting a supraglottic device20 or performing a surgical airway. How, if at all, does the oropharyngeal view relate to tracheal intubation techniques other than direct laryngoscopy? The question is especially relevant with the recent explosion in numbers of alternatives to direct laryngoscopy, video laryngoscopes in particular. Indeed, the 2013 American Society of Anesthesiologists difficult airway guidelines now include ‘‘video-assisted laryngoscopy as an initial approach to intubation’’ as an option to consider for the anticipated difficult airway.21 In two studies that address predictors of difficult tracheal intubation using the GlideScopeTM video laryngoscope, a high Mallampati class was found not22 or only weakly23 to predict difficulty. This is not surprising, as the whole premise of most indirect (e.g., video) laryngoscopes is to allow ‘‘around-the-corner’’ visualization, bypassing the obstructing base-of-tongue that can be such an impediment to direct laryngoscopy.24 Successful intubation using the Trachlight lighted stylet appears to be similarly independent of Mallampati class.25 So, where does that leave the Mallampati classification in 2014? After obtaining an ‘‘end-of-bed gestalt’’, it can still be argued that mouth opening is a good starting point for the airway evaluation. It gives an early indication of patient cooperation, and beyond obtaining the modified Mallampati class, enables quick assessment of inter-incisor distance, width of the dental arch, and condition of the teeth. If direct laryngoscopy is planned, seeing a Mallampati class 1 or 2 view is probably reassuring, while a modified Mallampati class 3 or 4 may be an indication of difficulty if other anatomic predictors, such as jaw protrusion or head and upper neck extension, are also abnormal. A high Mallampati class may also be an indication to assess the patient carefully for other predictors of difficult bag-mask ventilation. To date, it does not appear to be a strong indication of difficulty with alternatives to direct laryngoscopy such as video laryngoscopy.
123
Dr. Mallampati is alive and well and continues to administer anesthetics in Boston, MA. The author of this review contacted him to ask for reflections on his 1985 study. Although charmingly modest, he did allow that widespread use of the simple and quickly performed test may have helped widen the focus of the airway exam from assessing only bony dimensions to also considering the oropharynx and its contents. On its potential application to video laryngoscopy, Dr. Mallampati ventured that he would not be surprised to see, eventually, reports of future clinical trials showing a positive correlation between a high Mallampati class and difficulty with tracheal intubation using video-based devices.A
Key points •
•
•
•
•
Published in the early 1980s, Dr. Mallampati’s observation and clinical trial made the connection between difficult direct laryngoscopy and a base-oftongue disproportionately large to the volume of the oropharyngeal cavity. Although subsequent studies have questioned sensitivity and positive predicted value figures for the Mallampati exam by itself, it does appear to be useful as a component of a multi-component airway examination. As a widely referenced paper, the Mallampati study has helped increase awareness of the need for an airway evaluation. There is now some evidence that a modified Mallampati class 3 or 4 oropharyngeal view may correlate with difficult bag-mask ventilation. To date, a modified Mallampati class 3 or 4 view does not appear to have significant correlation with difficult tracheal intubation using alternatives to direct laryngoscopy such as video laryngoscopy.
Acknowledgments Supported in part by the Department of Anesthesia, Dalhousie University. Conflicts of interest
None declared.
Disclosures None related to this article. The author has been a recipient of equipment (as loan or gift) from Ambu A/S, BOMImed, and Prodol Meditec and has sold a patent to Ambu A/S.
A By the way, sensitive, specific, or not, Dr. Mallampati still assesses the oropharyngeal view in all his patients. Happily, he denies that it bothers him to see his name misspelled with two t’s, but did offer that people could save themselves some space by using the correct spelling…
Key article from the journal archives
References 1. Mallampati SR. Clinical sign to predict difficult tracheal intubation (hypothesis). Can Anaesth Soc J 1983; 30(3 Pt 1): 316-7. 2. Mallampati SR, Gatt SP, Gugino LD, et al. A clinical sign to predict difficult tracheal intubation: a prospective study. Can Anaesth Soc J 1985; 32: 429-34. 3. Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 1984; 39: 1105-11. 4. Knill RL. Difficult laryngoscopy made easy with a ‘‘BURP’’. Can J Anaesth 1993; 40: 279-82. 5. Law JA, Broemling N, Cooper RM, et al.; for the Canadian Airway Focus Group. The difficult airway with recommendations for management - Part 1 - Difficult tracheal intubation encountered in an unconscious/induced patient. Can J Anesth 2013; 60: 1089-118. 6. Samsoon GL, Young JR. Difficult tracheal intubation: a retrospective study. Anaesthesia 1987; 42: 487-90. 7. Lee A, Fan LT, Gin T, Karmakar MK, Ngan Kee WD. A systematic review (meta-analysis) of the accuracy of the Mallampati tests to predict the difficult airway. Anesth Analg 2006; 102: 1867-78. 8. Lundstrom LH, Vester-Andersen M, Moller AM, et al. Poor prognostic value of the modified Mallampati score: a metaanalysis involving 177 088 patients. Br J Anaesth 2011; 107: 659-67. 9. Arne J, Descoins P, Fusciardi J, et al. Preoperative assessment for difficult intubation in general and ENT surgery: predictive value of a clinical multivariate risk index. Br J Anaesth 1998; 80: 140-6. 10. Naguib M, Scamman FL, O’Sullivan C, et al. Predictive performance of three multivariate difficult tracheal intubation models: a double-blind, case-controlled study. Anesth Analg 2006; 102: 818-24. 11. el-Ganzouri AR, McCarthy RJ, Tuman KJ, Tanck EN, Ivankovich AD. Preoperative airway assessment: predictive value of a multivariate risk index. Anesth Analg 1996; 82: 1197-204. 12. Karkouti K, Rose DK, Ferris LE, Wigglesworth DF, MeisamiFard T, Lee H. Inter-observer reliability of ten tests used for predicting difficult tracheal intubation. Can J Anaesth 1996; 43: 554-9.
13. Wilson ME, John R. Problems with the Mallampati sign. Anaesthesia 1990; 45: 486-7. 14. Cook TM. A new practical classification of laryngeal view. Anaesthesia 2000; 55: 274-9. 15. O’Leary AM, Sandison MR, Roberts KW. History of anesthesia; Mallampati revisited: 20 years on. Can J Anesth 2008; 55: 250-1. 16. Murphy M, Hung O, Launcelott G, Law JA, Morris I. Predicting the difficult laryngoscopic intubation: are we on the right track? Can J Anesth 2005; 52: 231-5. 17. Kheterpal S, Han R, Tremper KK, et al. Incidence and predictors of difficult and impossible mask ventilation. Anesthesiology 2006; 105: 885-91. 18. Kheterpal S, Martin L, Shanks AM, Tremper KK. Prediction and outcomes of impossible mask ventilation: a review of 50,000 anesthetics. Anesthesiology 2009; 110: 891-7. 19. Yildiz TS, Solak M, Toker K. The incidence and risk factors of difficult mask ventilation. J Anesth 2005; 19: 7-11. 20. Brimacombe JR. Difficult airway. In: Laryngeal mask anesthesia: principles and practice, 2nd ed. Philadelphia: Saunders; 2005. p. 305-55. 21. Apfelbaum JL, Hagberg CA, Caplan RA, et al. Practice guidelines for management of the difficult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology 2013; 118: 251-70. 22. Aziz MF, Healy D, Kheterpal S, Fu RF, Dillman D, Brambrink AM. Routine clinical practice effectiveness of the Glidescope in difficult airway management: an analysis of 2,004 Glidescope intubations, complications, and failures from two institutions. Anesthesiology 2011; 114: 34-41. 23. Tremblay MH, Williams S, Robitaille A, Drolet P. Poor visualization during direct laryngoscopy and high upper lip bite test score are predictors of difficult intubation with the GlideScope videolaryngoscope. Anesth Analg 2008; 106: 1495500. 24. Griesdale DE, Liu D, McKinney J, Choi PT. GlideScope videolaryngoscopy versus direct laryngoscopy for endotracheal intubation: a systematic review and meta-analysis. Can J Anesth 2012; 59: 41-52. 25. Hung OR, Pytka S, Morris I, et al. Clinical trial of a new lightwand device (Trachlight) to intubate the trachea. Anesthesiology 1995; 83: 509-14.
123
SPECIAL ARTICLE
From the Journal archives: Mallampati in two millennia: its impact then and implications now J. Adam Law, MD
Received: 6 October 2013 / Accepted: 18 December 2013 Canadian Anesthesiologists’ Society 2014
Editors’ Note: Classics Revisited Key Articles from the Canadian Journal of Anesthesia Archives: 1954-2013 As part of the Journal’s 60th anniversary Diamond Jubilee Celebration, a number of seminal articles from the Journal archives are highlighted in the Journal’s 61st printed volume and online at: www.springer.com/ 12630. The following article was selected on the basis of its novelty at the time of publication, its scientific merit, and its overall importance to clinical practice: Mallampati SR, Gatt SP, Gugino LD, et al. A clinical sign to predict difficult tracheal intubation: a prospective study. Can Anaesth Soc J 1985; 32: 429-34. Dr. J. Adam Law provides expert commentary on the poor correlation between the oropharyngeal view and ease of tracheal intubation and how, almost 30 years after publication of this article, the Mallampati classification continues to be commonly assessed as part of a comprehensive airway evaluation. Hilary P. Grocott MD, Editor-in-Chief Donald R. Miller MD, Former Editor-in-Chief Overview In the early 1980s, few alternatives were available when difficult direct laryngoscopy was encountered in the J. A. Law, MD (&) Department of Anesthesia, Dalhousie University, QEII Health Sciences Centre, Halifax Infirmary Site, 1796 Summer Street, Halifax, NS B3H 3A7, Canada e-mail: [email protected]
unconscious patient. Until then, to help avoid unanticipated difficult laryngoscopy, the airway evaluation focused on an examination of the bony aspects of patient anatomy, such as the mentohyoid distance. In 1985, Dr. Mallampati et al. published their study on the relationship between the visibility of oropharyngeal structures and the subsequent view obtained during direct laryngoscopy. In so doing, the connection was made between difficult direct laryngoscopy and a base-of-tongue disproportionately large to the volume of the oropharyngeal cavity. Although later clinical trials questioned the sensitivity and positive predicted value suggested by results of the original study, the Mallampati classification continues to be useful as a component of a multivariate airway assessment. In addition, evidence is emerging that a modified Mallampati class 3 or 4 view may correlate with difficult bag-mask ventilation. To date, any studies on alternatives to direct laryngoscopy, such as video laryngoscopy, suggest little correlation between the oropharyngeal view and ease of tracheal intubation with their use. Regardless, almost 30 years later, the Mallampati classification continues to be commonly assessed as part of a comprehensive airway evaluation.
Article summary Authors: Mallampati SR, Gatt SP, Gugino LD, Desai SP, Waraksa B, Freiberger D, Liu PL. Citation: Can Anaesth Soc J 1985; 32: 429-34. Purpose: In a 1983 letter to the editor, Dr. S. Rao Mallampati communicated his observations of a patient who had unexpectedly presented great difficulty with direct laryngoscopy.1 A subsequent examination of the patient revealed normal anatomic features of the head, neck, and teeth, as well as normal temporomandibular joint and neck mobility.
123
J. A. Law
Nevertheless, with the patient’s mouth opened widely and her tongue maximally protruded, the faucial pillars and uvula were concealed by her tongue, and her soft palate was barely visible. In his communication, Mallampati hypothesized that a disproportionately large tongue base would mask visibility of the faucial pillars and uvula on airway examination, and by ‘‘overshadowing the larynx and render[ing] the angle to the larynx more acute’’ during direct laryngoscopy, it might portend difficult direct laryngoscopy.1 In this 1985 publication,2 Dr. Mallampati et al. followed up the letter with their classic prospective study that formally assessed the relationship between the visibility of oropharyngeal structures (faucial pillars, soft palate, and uvula) on examination and subsequent ease or difficulty of direct laryngoscopy. Principal findings: The study included just over 200 surgical patients requiring tracheal intubation. Preoperatively, each patient was examined twice for oropharyngeal visibility by one of 22 clinicians. Patients were assessed in the sitting position with a widely opened mouth and maximally protruded tongue, and they were assigned to one of three classes (Table 1). There were 155 patients assigned to class 1, 40 assigned to class 2, and 15 assigned to class 3. After examination, general anesthesia was induced with conditions optimized by succinylcholine, and the same clinician performed direct laryngoscopy with a Macintosh 3 blade. The laryngeal view obtained was graded using a four-point scale similar (although not identical) to that published earlier by Cormack and Lehane3 (Table 2). No class 1 patients presented difficulty with direct laryngoscopy. In ten of the 40 class 2 patients, only the corniculate cartilages could be exposed, and in four class 2 patients, none of the glottis (including the corniculate cartilages) could be seen. In nine of the 15 class 3 patients, only the corniculate cartilages could be seen, and in five class 3 patients, none of the glottis was visualized. ‘‘Inadequate exposure’’ was defined as a view of only the corniculate cartilages or worse. The result of the Chi square test was significant at P \ 0.001. Conclusions: The authors concluded that a correlation exists between the ability to visualize oropharyngeal structures and ease of direct laryngoscopy. Table 1 Classification of oropharyngeal view Mallampati2
Samsoon and Young6
Class 1
Faucial pillars, soft palate, and uvula Soft palate, fauces, can be visualized uvula, and pillars visible
Class 2
Faucial pillars and soft palate can be Soft palate, fauces, and visualized, but uvula is masked uvula visible by the base of the tongue
Class 3
Only the soft palate can be visualized
Class 4
123
Soft palate and base of uvula visible Soft palate not visible at all
Table 2 Grading of laryngeal exposure Mallampati2
Cormack-Lehane3
Grade 1
Glottis (including anterior Most of the glottis is visible and posterior [no difficulty] commissures) can be fully exposed [adequate exposure]
Grade 2
Glottis can be partly exposed Only the posterior extremity (anterior commissure not of the glottis is visible visualized) [adequate [slight difficulty] exposure]
Grade 3
Glottis cannot be exposed No part of the glottis can be (only corniculate cartilages seen, but only the epiglottis can be visualized) [fairly severe difficulty] [inadequate exposure]
Grade 4
Glottis including corniculate cartilages cannot be exposed [inadequate exposure]
Not even the epiglottis can be exposed [intubation impossible except by special methods]
In the early 1980s, most tracheal intubations were facilitated by direct laryngoscopy. Commonly used alternatives to direct laryngoscopy for tracheal intubation in the anesthetized patient (e.g., Trachlight (Laerdal Medical Corp., Wappingers Falls, NY, USA), Bullard (Circon Corporation, Santa Barbara, CA, USA) laryngoscope or LMA-Fastrach (LMA North America, San Diego, CA, USA) would not appear until the 1990s, and video laryngoscopy was almost two decades away. At least in North America, the Eschmann tracheal tube introducer (‘‘bougie’’) was not in common use as an adjunct to direct laryngoscopy, which meant a poor laryngoscopic view would often result in a failed intubation attempt. If maneuvers such as external laryngeal manipulation or an exaggerated head lift failed to reveal the larynx during direct laryngoscopy, blind attempts to ‘‘hook’’ a styleted endotracheal tube into the trachea beneath an obscuring epiglottis would often follow. This approach met with variable success, and prolonged attempts at tracheal intubation by multiple operators would sometimes ensue,4 an approach that is now known to be detrimental to the patient.5 At the time, often the only alternative means of tracheal intubation in the unconscious patient was the flexible fibreoptic bronchoscope. Issues could be encountered with this option, including collapsing soft tissues, blood and secretions in an airway already subjected to multiple intubation attempts, and variable operator skills. With so few effective options for failed intubation by direct laryngoscopy, it is little surprise that Mallampati and others were motivated to identify patients likely to present significant difficulty with direct laryngoscopy under general anesthesia. Once such patients were identified, they could be considered for ‘‘awake’’ tracheal intubation
Key article from the journal archives Figure The modified Mallampati classification of oropharyngeal view. Reproduced with permission from: Samsoon GL, Young JR. Difficult tracheal intubation: a retrospective study. Anaesthesia 1987; 42: 487-90
or other options such as a regional anesthetic technique. Awake intubation would most likely be performed with the same flexible fibreoptic bronchoscope that could be used in an unconscious patient, but in the awake patient, there would be additional benefits, including a protected, patent airway through which to navigate and maintenance of spontaneous ventilation. As referenced in the Mallampati paper, earlier published reports had already begun to address the prediction of difficult direct laryngoscopy. Several of these studies concluded that bony constraints of the mandible and upper cervical spine could cause difficulty; however, they made no direct association between limited dimensions of the mandible and difficulty with tongue retraction during laryngoscopy. In his prescient 1985 paper, Mallampati was one of the first researchers to make the connection between difficult direct laryngoscopy and a base-of-tongue disproportionately large to the volume of the oropharyngeal cavity.2 Samsoon and Young published an article soon after the Mallampati study.6 In their study, obstetrical and other surgical patients with previously failed tracheal intubation were recalled for assessment. Samsoon and Young modified the scale published by Mallampati et al. by adding a fourth class of oropharyngeal view in which no aspect of the soft palate was visible. In their series, all 12 patients who had experienced failed tracheal intubation on the basis of difficult (Cormack-Lehane grades 3 and 4) direct laryngoscopy were subsequently found to have a class 4 oropharyngeal view on examination.6 Although small numbers were involved and the study was retrospective, the Samsoon and Young paper continues to be frequently referenced alongside the Mallampati study, and indeed, the term ‘‘modified Mallampati’’ is often used to describe the now commonly used four-view oropharyngeal classification. To this day, when the oropharyngeal view is described or studied, the accompanying pictorial diagram is generally the one originating from the Samsoon study (Figure).
Since 1985, many more studies have assessed the efficacy of the modified or original Mallampati classification in predicting difficult laryngoscopy and/or intubation, either on its own or as a component of multivariate airway assessments. A number of meta-analyses can now be added to this inventory.7,8 Most study results concur that both sensitivity and positive predicted value are limited when a modified Mallampati class 3 or 4 oropharyngeal view is used as a sole anatomic predictor, meaning that a difficult laryngoscopy or intubation situation does not consistently ensue. Conversely, a modified Mallampati class 1 or 2 more specifically reassures the clinician that easy laryngoscopy/intubation will follow. In all probability, it is reasonable to state that few clinicians would ever rely on only a single anatomic feature to predict difficult laryngoscopy or intubation. Indeed, studies of multivariate airway evaluations (many of which include the Mallampati assessment) do indicate higher sensitivity and specificity figures.9-11 Interestingly, even the original 1985 Mallampati study documents that subject patients’ head and neck mobility was also examined during their airway assessments. Beyond sensitivity concerns, the modified Mallampati classification has been criticized for poor inter-observer reliability12 and potential changes in oropharyngeal view with phonation or patient position.13 The original study had multiple assessors, and bias may have occurred for each subject by having the same clinician rate both oropharyngeal and laryngoscopic views. Furthermore, it has been observed that the study would have resulted in sensitivity and positive predicted value figures more congruent with subsequent clinical trials if it had not included a ‘‘corniculates-only’’ view (i.e., CormackLehane grade 2b)14 in the ‘‘difficult orotracheal intubation’’ group.15 Nevertheless, when published in 1985, the Mallampati study helped increase awareness of the utility of an airway evaluation and paved the way for further studies on anatomic predictors of difficult direct laryngoscopy.
123
J. A. Law
In contemporary airway management practice, emphasis is appropriately placed on patient oxygenation rather than on tracheal intubation alone. Accordingly, a complete airway evaluation also seeks predictors of difficulty with fall-back oxygenation options such as bag-mask ventilation, use of a supraglottic device, and even surgical airway.16 It turns out that a modified Mallampati class 3 and/or 4 has also been identified as a predictor of difficult and/or impossible bag-mask ventilation.17-19 This is significant, as the combination of predicted difficulty with both direct laryngoscopy/ intubation and bag-mask ventilation may favour awake tracheal intubation in some circumstances. Fortunately, a high modified Mallampati class is not correlated with difficulty inserting a supraglottic device20 or performing a surgical airway. How, if at all, does the oropharyngeal view relate to tracheal intubation techniques other than direct laryngoscopy? The question is especially relevant with the recent explosion in numbers of alternatives to direct laryngoscopy, video laryngoscopes in particular. Indeed, the 2013 American Society of Anesthesiologists difficult airway guidelines now include ‘‘video-assisted laryngoscopy as an initial approach to intubation’’ as an option to consider for the anticipated difficult airway.21 In two studies that address predictors of difficult tracheal intubation using the GlideScopeTM video laryngoscope, a high Mallampati class was found not22 or only weakly23 to predict difficulty. This is not surprising, as the whole premise of most indirect (e.g., video) laryngoscopes is to allow ‘‘around-the-corner’’ visualization, bypassing the obstructing base-of-tongue that can be such an impediment to direct laryngoscopy.24 Successful intubation using the Trachlight lighted stylet appears to be similarly independent of Mallampati class.25 So, where does that leave the Mallampati classification in 2014? After obtaining an ‘‘end-of-bed gestalt’’, it can still be argued that mouth opening is a good starting point for the airway evaluation. It gives an early indication of patient cooperation, and beyond obtaining the modified Mallampati class, enables quick assessment of inter-incisor distance, width of the dental arch, and condition of the teeth. If direct laryngoscopy is planned, seeing a Mallampati class 1 or 2 view is probably reassuring, while a modified Mallampati class 3 or 4 may be an indication of difficulty if other anatomic predictors, such as jaw protrusion or head and upper neck extension, are also abnormal. A high Mallampati class may also be an indication to assess the patient carefully for other predictors of difficult bag-mask ventilation. To date, it does not appear to be a strong indication of difficulty with alternatives to direct laryngoscopy such as video laryngoscopy.
123
Dr. Mallampati is alive and well and continues to administer anesthetics in Boston, MA. The author of this review contacted him to ask for reflections on his 1985 study. Although charmingly modest, he did allow that widespread use of the simple and quickly performed test may have helped widen the focus of the airway exam from assessing only bony dimensions to also considering the oropharynx and its contents. On its potential application to video laryngoscopy, Dr. Mallampati ventured that he would not be surprised to see, eventually, reports of future clinical trials showing a positive correlation between a high Mallampati class and difficulty with tracheal intubation using video-based devices.A
Key points •
•
•
•
•
Published in the early 1980s, Dr. Mallampati’s observation and clinical trial made the connection between difficult direct laryngoscopy and a base-oftongue disproportionately large to the volume of the oropharyngeal cavity. Although subsequent studies have questioned sensitivity and positive predicted value figures for the Mallampati exam by itself, it does appear to be useful as a component of a multi-component airway examination. As a widely referenced paper, the Mallampati study has helped increase awareness of the need for an airway evaluation. There is now some evidence that a modified Mallampati class 3 or 4 oropharyngeal view may correlate with difficult bag-mask ventilation. To date, a modified Mallampati class 3 or 4 view does not appear to have significant correlation with difficult tracheal intubation using alternatives to direct laryngoscopy such as video laryngoscopy.
Acknowledgments Supported in part by the Department of Anesthesia, Dalhousie University. Conflicts of interest
None declared.
Disclosures None related to this article. The author has been a recipient of equipment (as loan or gift) from Ambu A/S, BOMImed, and Prodol Meditec and has sold a patent to Ambu A/S.
A By the way, sensitive, specific, or not, Dr. Mallampati still assesses the oropharyngeal view in all his patients. Happily, he denies that it bothers him to see his name misspelled with two t’s, but did offer that people could save themselves some space by using the correct spelling…
Key article from the journal archives
References 1. Mallampati SR. Clinical sign to predict difficult tracheal intubation (hypothesis). Can Anaesth Soc J 1983; 30(3 Pt 1): 316-7. 2. Mallampati SR, Gatt SP, Gugino LD, et al. A clinical sign to predict difficult tracheal intubation: a prospective study. Can Anaesth Soc J 1985; 32: 429-34. 3. Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 1984; 39: 1105-11. 4. Knill RL. Difficult laryngoscopy made easy with a ‘‘BURP’’. Can J Anaesth 1993; 40: 279-82. 5. Law JA, Broemling N, Cooper RM, et al.; for the Canadian Airway Focus Group. The difficult airway with recommendations for management - Part 1 - Difficult tracheal intubation encountered in an unconscious/induced patient. Can J Anesth 2013; 60: 1089-118. 6. Samsoon GL, Young JR. Difficult tracheal intubation: a retrospective study. Anaesthesia 1987; 42: 487-90. 7. Lee A, Fan LT, Gin T, Karmakar MK, Ngan Kee WD. A systematic review (meta-analysis) of the accuracy of the Mallampati tests to predict the difficult airway. Anesth Analg 2006; 102: 1867-78. 8. Lundstrom LH, Vester-Andersen M, Moller AM, et al. Poor prognostic value of the modified Mallampati score: a metaanalysis involving 177 088 patients. Br J Anaesth 2011; 107: 659-67. 9. Arne J, Descoins P, Fusciardi J, et al. Preoperative assessment for difficult intubation in general and ENT surgery: predictive value of a clinical multivariate risk index. Br J Anaesth 1998; 80: 140-6. 10. Naguib M, Scamman FL, O’Sullivan C, et al. Predictive performance of three multivariate difficult tracheal intubation models: a double-blind, case-controlled study. Anesth Analg 2006; 102: 818-24. 11. el-Ganzouri AR, McCarthy RJ, Tuman KJ, Tanck EN, Ivankovich AD. Preoperative airway assessment: predictive value of a multivariate risk index. Anesth Analg 1996; 82: 1197-204. 12. Karkouti K, Rose DK, Ferris LE, Wigglesworth DF, MeisamiFard T, Lee H. Inter-observer reliability of ten tests used for predicting difficult tracheal intubation. Can J Anaesth 1996; 43: 554-9.
13. Wilson ME, John R. Problems with the Mallampati sign. Anaesthesia 1990; 45: 486-7. 14. Cook TM. A new practical classification of laryngeal view. Anaesthesia 2000; 55: 274-9. 15. O’Leary AM, Sandison MR, Roberts KW. History of anesthesia; Mallampati revisited: 20 years on. Can J Anesth 2008; 55: 250-1. 16. Murphy M, Hung O, Launcelott G, Law JA, Morris I. Predicting the difficult laryngoscopic intubation: are we on the right track? Can J Anesth 2005; 52: 231-5. 17. Kheterpal S, Han R, Tremper KK, et al. Incidence and predictors of difficult and impossible mask ventilation. Anesthesiology 2006; 105: 885-91. 18. Kheterpal S, Martin L, Shanks AM, Tremper KK. Prediction and outcomes of impossible mask ventilation: a review of 50,000 anesthetics. Anesthesiology 2009; 110: 891-7. 19. Yildiz TS, Solak M, Toker K. The incidence and risk factors of difficult mask ventilation. J Anesth 2005; 19: 7-11. 20. Brimacombe JR. Difficult airway. In: Laryngeal mask anesthesia: principles and practice, 2nd ed. Philadelphia: Saunders; 2005. p. 305-55. 21. Apfelbaum JL, Hagberg CA, Caplan RA, et al. Practice guidelines for management of the difficult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology 2013; 118: 251-70. 22. Aziz MF, Healy D, Kheterpal S, Fu RF, Dillman D, Brambrink AM. Routine clinical practice effectiveness of the Glidescope in difficult airway management: an analysis of 2,004 Glidescope intubations, complications, and failures from two institutions. Anesthesiology 2011; 114: 34-41. 23. Tremblay MH, Williams S, Robitaille A, Drolet P. Poor visualization during direct laryngoscopy and high upper lip bite test score are predictors of difficult intubation with the GlideScope videolaryngoscope. Anesth Analg 2008; 106: 1495500. 24. Griesdale DE, Liu D, McKinney J, Choi PT. GlideScope videolaryngoscopy versus direct laryngoscopy for endotracheal intubation: a systematic review and meta-analysis. Can J Anesth 2012; 59: 41-52. 25. Hung OR, Pytka S, Morris I, et al. Clinical trial of a new lightwand device (Trachlight) to intubate the trachea. Anesthesiology 1995; 83: 509-14.
123
