Predictors Of Difficult Intubation: Study In Kashmiri Population

Abstract

Airway assessment is the most important aspect of Anaesthesia practice as a difficult intubation may be unanticipated. A prospective study was done to compare the efficacy of airway parameters to predict difficult intubation viz; degree of head extension, thyromental distance, inter incisor gap, grading ofprognathism, obesity and modified mallampati test. Six hundred patients with ASA I& ASA II grade were enrolled in study. All patients were preoperatively assessed for airway parameters. Intra-operatively all patients were classified according to Cormack and Lehane laryngoscopic view. Clinical data of each test was collected, tabulated and analyzed to obtain the sensitivity, specificity, positive predictive value & negative predictive value. Results obtained showed incidence of difficult intubation in 3.3%. Head&neck movements had the highest sensitivity (86.36%); high arched palate had highest specificity (99.38%).Head & neck movements had highest sensitivity; high arched palate had highest specificity, however, head & neck movements strongly correlated for patients with difficult intubation.

Full text

British Journal of Medical Practitioners, March 2010, Volume 3, Number 1
© BJMP.org
BJMP 2010;3(1):307
Predictors
Predictors Predictors
Predictors of
ofof
of
Difficult Intubation: Study In Kashmiri Population
Difficult Intubation: Study In Kashmiri PopulationDifficult Intubation: Study In Kashmiri Population
Difficult Intubation: Study In Kashmiri Population
Arun Kr. Gupta
Arun Kr. Gupta Arun Kr. Gupta
Arun Kr. Gupta , Mohamad Ommid , Showkat Nengroo , Imtiyaz Naqash and Anjali Mehta
, Mohamad Ommid , Showkat Nengroo , Imtiyaz Naqash and Anjali Mehta, Mohamad Ommid , Showkat Nengroo , Imtiyaz Naqash and Anjali Mehta
, Mohamad Ommid , Showkat Nengroo , Imtiyaz Naqash and Anjali Mehta
Abstract
AbstractAbstract
Abstract
Airway assessment is the most important aspect of anaesthetic practice as a difficult intubation may be unanticipated. A prospective study was done to
compare the efficacy of airway parameters to predict difficult intubation. Parameters studied were degree of head extension, thyromental distance, inter
incisor gap, grading of prognathism, obesity and modified mallampati classification. 600 Patients with ASA I& ASA II grade were enrolled in the study. All
patients were preoperatively assessed for airway parameters. Intra-operatively all patients were classified according to Cormack and Lehane laryngoscopic
view. Clinical data of each test was collected, tabulated and analyzed to obtain the sensitivity, specificity, positive predictive value & negative predictive
value. Results obtained showed an incidence of difficult intubation of 3.3 % of patients. Head and neck movements had the highest sensitivity (86.36%);
high arched palate had the highest specificity (99.38%). Head and neck movements strongly correlated for patients with difficult intubation.
KEYWORDS
KEYWORDSKEYWORDS
KEYWORDS
Intubation, Anaesthesia, Laryngoscopy
Introduction
IntroductionIntroduction
Introduction
The fundamental responsibility of an anesthesiologist is to
maintain adequate gas exchange through a patent airway.
Failure to maintain a patent airway for more than a few minutes
results in brain damage or death
1
. Anaesthesia in a patient with
a difficult airway can lead to both direct airway trauma and
morbidity from hypoxia and hypercarbia. Direct airway trauma
occurs because the management of the difficult airway often
involves the application of more physical force to the patient’s
airway than is normally used. Much of the morbidity
specifically attributable to managing a difficult airway comes
from an interruption of gas exchange (hypoxia and
hypercapnia), which may then cause brain damage and
cardiovascular activation or depression
2
.
Though endotracheal intubation is a routine procedure for all
anesthesiologists, occasions may arise when even an experienced
anesthesiologist might have great difficulty in the technique of
intubation for successful control of the airway. As difficult
intubation occurs infrequently and is not easy to define,
research has been directed at predicting difficult laryngoscopy,
i.e. when is not possible to visualize any portion of the vocal
cords after multiple attempts at conventional laryngoscopy. It is
argued that if difficult laryngoscopy has been predicted and
intubation is essential, skilled assistance and specialist
equipment should be provided. Although the incidence of
difficult or failed tracheal intubation is comparatively low,
unexpected difficulties and poorly managed situations may
result in a life threatening condition or even death
3
.
Difficulty in intubation is usually associated with difficulty in
exposing the glottis by direct laryngoscopy. This involves a
series of manoeuvres, including extending the head, opening the
mouth, displacing and compressing the tongue into the
submandibular space and lifting the mandible forward. The
ease or difficulty in performing each of these manoeuvres can be
assessed by one or more parameters
4
.
Extension of the head at the atlanto-occipital joint can be
assessed by simply looking at the movements of the head,
measuring the sternomental distance, or by using devices to
measure the angle
5
. Mouth opening can be assessed by
measuring the distance between upper and lower incisors with
the mouth fully open. The ease of lifting the mandible can be
assessed by comparing the relative position of the lower incisors
in comparison with the upper incisors after forward protrusion
of the mandible
6
. The measurement of the mento-hyoid
distance and thyromental distance provide a rough estimate of
the submandibular space
7
. The ability of the patient to move
the lower incisor in front of the upper incisor tells us about jaw
movement. The classification provided by Mallampati et al
8
and
later modified by Samsoon and Young
9
helps to assess the size
of tongue relative to the oropharynx. Abnormalities in one or
more of these parameters may help predict difficulty in direct
laryngoscopy
1
.
Initial studies attempted to compare individual parameters to
predict difficult intubation with mixed results
8,9
. Later studies
have attempted to create a scoring system
3,10
or a complex
mathematical model
11,12
. This study is an attempt to verify
which of these factors are significantly associated with difficult
exposure of glottis and to rank them according to the strength
of association.
Materials & methods
Materials & methodsMaterials & methods
Materials & methods
The study was conducted after obtaining institutional review
board approval. Six hundred ASA I & II adult patients,
scheduled for various elective procedures under general
anesthesia, were included in the study after obtaining informed
consent. Patients with gross abnormalities of the airway were
excluded from the study. All patients were assessed the evening
before surgery by a single observer. The details of airway
assessment are given in Table I.
Re
Re
Re
Rese ar c h
se ar c h
se ar c h
se ar c h
Ar ti cl e
Ar ti cl e
Ar ti cl e
Ar ti cl e

British Journal of Medical Practitioners, March 2010, Volume 3, Number 1
© BJMP.org
Table I: Method of assessment of various airway parameters
Table I: Method of assessment of various airway parameters Table I: Method of assessment of various airway parameters
Table I: Method of assessment of various airway parameters
(predictors)
(predictors)(predictors)
(predictors)
Airway Paramet
Airway ParametAirway Paramet
Airway Paramet
er
erer
er
Method of assessment
Method of assessmentMethod of assessment
Method of assessment
Modified
Mallampati Scoring
Class I:
Faucial pillars, soft palate and uvula
visible.
Class II: Soft palate and base of uvula seen
Class III: Only soft palate visible.
Class IV: Soft palate not seen
Class I & II : Easy Intubation
Class III & IV: Difficult Intubation
Obesity
Obese
BMI (
≥ 25)
Non Obese BMI (< 25)
Inter Incisor Gap
Distance between the incisors with mouth fully
open(cms)
Thyromental
distance
Distance between the tip of thyroid cartilage and
tip of chin, with fully extended(cms)
Degree of Head
Extension
Grade I ≥ 90
◦
Grade II = 80
◦
-90
◦
Grade III < 80
◦
Grading of
Prognathism
Class A:
-
Lower incisor protruded anterior to
the upper incisor.
Class B: -
Lower incisor brought edge to edge
with upper incisor but not anterior to them.
Class C: -
Lower incisors could be brought edge
to edge.
In addition the patients were examined for the following.
• High arched palate.
• Protruding maximally incisor (Buck teeth)
• Wide & short Neck
Direct laryngoscopy with Macintosh blade was performed by an
anaesthetist who was blinded to preoperative assessment.
Glottic exposure was graded as per Cormack-Lehane
classification
13
(Fig 1).
Figure 1: Cormack
Figure 1: CormackFigure 1: Cormack
Figure 1: Cormack-
--
-Lehane grading of glottic exposure on direct
Lehane grading of glottic exposure on directLehane grading of glottic exposure on direct
Lehane grading of glottic exposure on direct
laryngoscopy
laryngoscopylaryngoscopy
laryngoscopy
Grade 1: most of the glottis visible; Grade 2: only the posterior
extremity of the glottis and the epiglottis visible; Grade 3: no part of the
glottis visible, only the epiglottis seen; Grade 4: not even the epiglottis
seen. Grades 1 and 2 were considered as ‘easy’ and grades 3 and 4 as
‘difficult’
.
Results
ResultsResults
Results
Glottic exposure on direct laryngoscopy was difficult in 20
(3.3%) patients. The frequency of patients in various categories
of ‘predictor’ variables is given in Table-II.
The association between different variables and difficulty in
intubation was evaluated using the chi-square test for qualitative
data and the student’s test for quantitative data and p<0.05 was
regarded as significant. The clinical data of each test was used to
obtain the sensitivity, specificity and positive and negative
predictive values. Results are shown in Table III.
Table II: The frequency analysis of predictor parameters
Table II: The frequency analysis of predictor parametersTable II: The frequency analysis of predictor parameters
Table II: The frequency analysis of predictor parameters
Airway Parameter
Airway ParameterAirway Parameter
Airway Parameter
Group
GroupGroup
Group
Frequency (%)
Frequency (%)Frequency (%)
Frequency (%)
Modified Mallampati
Scoring
Class 1&2
Class 3&4
96%
4%
Obesity
Obese BMI (
≥ 25)
Non Obese BMI (< 25)
28.7%
71.3%
Inter Incisor Gap
Class I :
>
4cm
Class II: <4cm
93.5%
6.5%
Thyromental distance
Class I:
≥ 6cm.
Class II: ≤6cm.
94.6%
5.4%
Head & Neck
Movements
Difficult {class II & III
(90˚)}
Easy {class I(>90˚)}
16%
84%
Grading of
Prognathism
Difficult (class III)
Easy (class I + II)
96.1%
3.9%
Wide and Short neck
Normal neck body ratio
1:13
Difficult (Ratio≥ 1:13)
86.9%
13.1%
High arched Palate
Yes
No
1.9%
98.1%
Protruding Incisors
Yes
No
4.2%
95.8%
Table III: Comparative analysis of v arious physical factors and
Table III: Comparative analysis of v arious physical factors and Table III: Comparative analysis of various physical factors and
Table III: Comparative analysis of v arious physical factors and
scoring systems
scoring systemsscoring systems
scoring systems
Physical factors and various
Physical factors and various Physical factors and various
Physical factors and various
Scoring Systems
Scoring SystemsScoring Systems
Scoring Systems
Sensitivity
Sensitivity Sensitivity
Sensitivity
( % )
( % )( % )
( % )
Specificity
Specificity Specificity
Specificity
( % )
( % )( % )
( % )
PPV
PPVPPV
PPV
( % )
( % )( % )
( % )
NPV
NPVNP V
NPV
( % )
( % )( % )
( % )
Obesity
81.8
72.76
6.34
99.43
Inter incisor gap
18.8
94.14
6.6
98.1
Thyromental distance
72.7
96.5
32.0
99.4
Head and Neck movement
86.36
86.0
34.6
99.7
Prognathism
4.5
96.3
2.7
97.9
Wide and Short neck
45.5
87.9
7.8
98.6
High arched palate
40.1
99.38
60.0
98.67
Protruding incisor
4.6
95.9
2.5
97.79
Mallampati scoring system
77.3
98.2
48.57
99.5
Cormack and Lehane’s scoring
system
100
99.7
88
100
Discussion
DiscussionDiscussion
Discussion
Difficulty in endotracheal intubation constitutes an important
cause of morbidity and mortality, especially when it is not
anticipated preoperatively. This unexpected difficulty in
intubation is the result of a lack of accurate predictive tests and
inadequate preoperative assessment of the airway. Risk factors if
identified at the preoperative visit help to alert the anaesthetist
so that alternative methods of securing the airway can be used
or additional expertise sought before hand.
Direct laryngoscopy is the gold standard for tracheal intubation.
There is no single definition of difficult intubation but the ASA
defines it as occurring when “tracheal intubation requires
multiple attempts, in the presence or absence of tracheal
pathology”. Difficult glottic view on direct laryngoscopy is the
most common cause of difficult intubation. The incidence of
difficult intubation in this study is similar to that found in
others.

British Journal of Medical Practitioners, March 2010, Volume 3, Number 1
© BJMP.org
As for as the predictors are concerned, different parameters for
the prediction of difficult airways have been studied. Restriction
of head and neck movement and decreased mandibular space
have been identified as important predictors in other studies.
Mallampati classification has been reported to be a good
predictor by many but found to be of limited value by others
14
.
Interincisor gap, forward movement of jaw and thyromental
distance have produced variable results in predicting difficult
airways in previous studies
7,15
. Even though thyromental
distance is a measure of mandibular space, it is influenced by
degree of head extension.
There have been attempts to create various scores in the past.
Many of them could not be reproduced by others or were
shown to be of limited practical value. Complicated
mathematical models based on clinical and/or radiological
parameters have been proposed in the past
16
, but these are
difficult to understand and follow in clinical settings. Many of
these studies consider all the parameters to be of equal
importance.
Instead of trying to find ‘ideal’ predictor(s), scores or models,
we simply arranged them in an order based on the strength of
association with difficult intubation. Restricted extension of
head, decreased thyromental distance and poor Mallampati class
are significantly associated with difficult intubation.
In other words patients with decreased head extension are at
much higher risk of having a difficult intubation compared to
those with abnormalities in other parameters. The type of
equipment needed can be chosen according to the parameter
which is abnormal. For example in a patient with decreased
mandibular space, it may be prudent to choose devices which
do not involve displacement of the tongue like the Bullard
laryngoscope or Fiber-optic laryngoscope. Similarly in patients
with decreased head extension devices like the McCoy
Larngoscope are likely to be more successful.
Conclusion
ConclusionConclusion
Conclusion
This prospective study assessed the efficacy of various
parameters of airway assessment as predictors of difficult
intubation. We have find that head and neck movements, high
arched palate, thyromental distance & Modified Malampatti
classification are the best predictors of difficult intubation
.
Competing In tere sts
Competing In tere stsCompeti ng I nter ests
Competing In tere sts
None Declared
Autho r Details
Autho r DetailsAu thor Detail s
Autho r Details
ARUN KUMAR GUPTA, Dept. Of Anaesthesiology, Rural Medical College,
Loni, India, MOHAMED OMMID, Dept. Of Anaesthesiology, SKIMS, Soura,
J&K, India, SHOWKAT NENGROO, Dept. Of Anaesthesiology, SKIMS,
Soura, J&K, India, IMTIYAZ NAQASH, Dept. Of Anaesthesiology, SKIMS,
Soura, J&K, India, ANJALI MEHTA, Dept. Of Anaesthesiology, GMC Jammu,
J&K, India.
CORRESSPONDENCE: ARUN KUMAR GUPTA, Assistant Professor Dept. of
Anaesthesiology & Critical Care Rural Medical College, Loni Maharashtra, India,
413736
Email: guptaarun71@yahoo.com
REFERENCES
REFERENCESREFERENCES
REFERENCES
1. Rose DK, Cohen MM. The airway: problems and predictions in
18,500 patients. Can J Anaesth 1994; 41:372-83.
2. Benumof JL: Management of the difficult airway: With special
emphasis on awake tracheal intubation. Anesthesiology 1991; 75: 1087-
1110
3. Wilson ME, Spiegelhalter D, Robertson JA, Lesser P. Predicting
difficult intubation. Br J Anaesth 1988; 61(2):211-6.
4. A.Vasudevan, A.S.Badhe. Predictors of difficult intubation – a simple
approach. The Internet Journal of Anesthesiology 2009; 20(2)
5. Tse JC, Rimm EB, Hussain A. Predicting difficult endotracheal
intubation in surgical patients scheduled for general anesthesia: a
prospective blind study. Anesth Analg 1995; 81(2):254-8.
6. Savva D. Prediction of difficult tracheal intubation. Br J
Anaesth 1994; 73(2):149-53.
7. Butler PJ, Dhara SS. Prediction of difficult laryngoscopy: an
assessment of the thyromental distance and Mallampati predictive
tests. Anaesth Intensive Care 1992; 20(2):139-42.
8. Mallampati SR, Gatt SP, Gugino LD, Desai SP, Waraksa B,
Freiberger D, et al. A clinical sign to predict difficult tracheal
intubation: a prospective study. Can Anaesth Soc J 1985; 32(4):429-34.
9. Samsoon GL, Young JR. Difficult tracheal intubation: a retrospective
study. Anaesthesia 1987; 42(5):487-90.
10. Nath G, Sekar M. Predicting difficult intubation--a comprehensive
scoring system. Anaesth Intensive Care 1997; 25(5):482-6.
11. Charters P. Analysis of mathematical model for osseous factors in
difficult intubation. Can J Anaesth 1994; 41(7):594-602.
12. Arne J, Descoins P, Fusciardi J, Ingrand P, Ferrier B, Boudigues D,
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(2):140-6.
13. Cormack RS, Lehane J. Difficult tracheal intubation in
obstetrics. Anaesthesia 1984; 39(11):1105-11.
14. 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(6):1867-78.
15. Bilgin H, Ozyurt G. Screening tests for predicting difficult
intubation. A clinical assessment in Turkish patients.Anaesth Intensive
Care 1998; 26(4):382-6.
16. Naguib M, Malabarey T, AlSatli RA, Al Damegh S, Samarkandi
AH. Predictive models for difficult laryngoscopy and intubation. A
clinical, radiologic and three-dimensional computer imaging study. Can
J Anaesth 1999; 46(8):748-59.