PRINCIPLES OF AIRWAY ASSESSMENT

Moderator : Dr. Anil OhriPresented by : Dr. Arun Kumar Sharma

Airway: Extra pulmonary passage.

Difficult airway: Problem in establishing or maintaining gas exchange via a mask , artificial airway or both.

Difficult airway is single most important cause of anesthesia related morbidity and mortality. Upto 30% deaths attributable to anesthesia are due to inadequate airway management.

Difficult airway clinics: allows time for optimal preperation , proper selection of equipment and technique and personal experienced in difficult airway management.

OBJECTIVES

History General, physical and regional examination Specific tests for assessment*Mallampati test*Atlanto occipital joint (AO) extension*Mandibular spaces*Wilson’s clasification*Ame &co.*LEMON Score*Radiological assessment

ASSESSMENT History and physical examination: History : Medial , surgical and

anesthetic factors. Anesthetic factors: edema , burns ,

bleed, tracheal compression , pneumothorax or aspiration of gastric contents.

PHYSICAL EXAMINATION Patency of nares: Mass,DNS, etc Mouth opening : atleast 3 fingers btw upper and lower incisors. Teeth : prominent upper incisors. Palate : high arched palate or long narrow mouth. Tongue size Patients ability to protrude lower jaw. Mandible TMJ movement Submental space Observation of patients neck-mass ,mobility , and ability to assume

sniff position. Hoarse voice/stridor or h/o tracheostomy: stenosis Airway infections Physiological conditions : pregnancy and obesity.

DIFFICULT TO MASK VENTILATEFactors affecting-a) Presence of beardb) Disfiguring malignancy of jawc) BMI >26 d) Absence of teethe) Age >55 f) H/o snoring g) Obstuctive sleep apnoeah) Mallampati class 3&4

SPECIFIC TESTS

Based on tongue/ pharyngeal size: Mallampatti test

(Dr.S.Rao Mallampati): sitting position,head neutral,mouth wide open,tongue protruding to its maximum(not to phonate)

Class I : soft palate, fauces,uvula, anterior and posterior pillars.Class II : soft palate, fauces and uvula.Class III : soft palate and base of uvula.(samsoon & young 1987) Class IV : Hard palate only.Its indirect means of relative proportionality so it should be repeated twice to avoid false positive/ negative.

FAILURE OF MALLAMPATI Failure to include evaluation of two

important factors affecting visualization of glottis

1. Neck mobility2. Size of mandibular space

i) AO extension- sniffing or magill position Oral,Pharyngeal,Laryngeal axis--straight line Angle traversed by occlusional surface of

upper teeth. Grade I : >35*-- (N) Grade II : 22-34* Grade III: 12-21* Grade IV : <12*

For movement at A-O joint ask patient to place the chin on the chest, clasp both hands behind the neck, pull downwards and try to move head upwards.

MANDIBULAR SPACE Sternomental distance-(savva 1948) <12.5cm predicts diff. intubation(PPV

82%) Inter incisor distance- 6 cm or 3 fingers---(N) <4 cm-makes intubation difficult. <2.5cm-LMA insertion will be difficult. Intraoral/ pharyngeal masses e.g

tumours or lingual tonsils (difficult LMA)

THYROMENTAL DISTANCE-3 FINGERS?

T-M distance(patil’s test)—with neck fully extended

6cm ---normal<3 fingers(<6 cm)

difficult(75%) Combined Patil and

mallampati tests(<6cm and class 3-

4)increases specificity(97%)

Hyo-mental distance: distance btw

mentum and hyoid Grade I :<4cm(2 fingers)--normal Grade II :4-6 cm Grade III >6cm

WILSON SCORE

Parameter 0 1 2

Weight (kg) < 90 90 – 110 > 110

Head & neck movement

> 90 = 90 < 90

IID > 5 = 5 < 5

Receding mandible None Moderate severe

Buck teeth None Moderate severe

≤5 Easy intubation; 8-10 very difficult intubation

A total score of >0r =2 predicts 75% of difficult intubation;12% False positives.

2)Ame &co –wilson + airway pathology(+ or-)

Sensitivity and specificity ----90%

LEMON AIRWAY ASSESSMENT L= Look externally (facial trauma, large incisors, beard or moustache, large tongue) E= Evaluate the 3-3-2 rule (incisor distance-3 finger breadths, thyroid-mental distance-3 finger breadths, mento-to-hyoid distance-2 finger breadths) M= Mallampati scoring O= Obstruction (presence of any condition like peritonsillar abscess, trauma,edema,foreign body). N= Neck mobility (limited neck mobility) The score with a maximum of 10 points is calculated by assigning 1 point for each . Patients in the difficult intubation group have higher

LEMON scores.

(Dr. Binnions Lemon )

DIRECT LARYNGOSCOPY AND FIBREOPTIC BRONCHOSCOPY

Cormack and Lehane(1984) defined 4 Grades Grade I – Visualization of entire laryngeal

aperture. Grade II – Visualization of only posterior commissure of laryngeal aperture. Grade III – Visualization of only epiglottis. Grade IV – Visualization of just the soft palate. Grade III and IV predict difficult intubation.

COOK’S MODIFICATION(1999) Grade IIa: visualization of posterior part of

vocal cord. Grade IIb :only arytenoid seen. Grade IIIa:epiglotis liftable. Grade IIIb:epiglotis adherent.Grade I & IIa can be intubated easily.Grade IIb & IIIa needs some support(bougie)Grade IIIb & IV requires alt. techniques.

MOUTH CLASSIFICATION: M : Mallampatti classification , mandibular space) O : Obesity,opening of mouth) U : Upper lip bite T : Teeth H :Head and neck movement.*(The only system which includes upper lip bite test)

Other scoring systems: a)MOANS(mask seal,obesity,age,no teeth,stiff lungs) b)RODS(restrcted oral opening,obstruction,distorted,stiff lungs) c)4Ds(dentition,distortion,disproportion,dismobility) d)LMMAP(look,mallampatti,measurement,A-O extn.,pathology of

teeth)

COLLAGEN DISORDERS: (DIABETIC STIFF JOINT SYNDROME)

Palm print: Grade 0 – All the phalangeal areas are

visible. Grade 1 – Deficiency in the

interphalangeal areas of the 4th and 5th digits.

Grade 2 – Deficiency in interphalangeal areas of 2nd to 5th digits.

Grade 3 – Only the tips of digits are seen

Prayer sign : Patient is

asked to bring both the palms together as ‘Namaste’ and sign is categorized as–

Positive – When there is gap between palms.

Negative – When there is no gap between palms.

If positive:Grade I-metacarpo-phalangeal

gapGrade II-proximal interphlyngeal

involvedGrade III- distal interphalyngeal

joint is also involved

The “prayer sign” indicates the presence of diabetic cheiroarthropathy.

Kim R P et al. Clin Diabetes 2001;19:132-135

Copyright © 2011 American Diabetes Association, Inc.

RADIOLOGICAL INVESTIGATIONS

RADIOLOGICAL ASSESSMENTi . Mandibulo-hyoid distance ii . Atlanto-occipital gap(5mm)Longer the A-O gap,

more space is available for mobility of head at that joint with good axis for laryngoscopy and intubation.

iii. Relation of mandibular angle and hyoid bone with cervical vertebra and laryngoscopy grading : Difficult when the mandibular angle tended to be more rostral and hyoid bone to be more caudal.

iv. Anterior/Posterior depth of the mandible (<3.6) White and Kander (1975)v. C1-C2 gapvi.Calcified stylohyoid ligaments :Difficult because of

inability to lift the epiglottis from posterior pharyngeal wall.

OTHER RADIOLOGICAL INVESTIGATIONS

Fluoroscopy for dynamic imaging for cord mobility,airway malacia.

Ultrasonography- Ant. Mediastinal mass,lymohadenopathy,d/d cyst from mass,cellulitis from abssess

CT/MRI – congenital anomalies.

CONCLUSION

No single airway test can provide a high index ofsensitivity and specificity for prediction of difficultairway. Therefore it has to be a combination of multipletests. It must be recognized, however, that some patientswith a difficult airway will remain undetected despite themost careful preoperative airway evaluation. Thus , anesthesiologists must always be

prepared with variety of preformulated and practiced plans for airway management in the event of an unanticipated difficult airway.

This is my

airway