AIRWAY ASSESSMENT

BY DR SALONI SOOD

MODERATOR :-DR SHELLY RANA

Maintenance of airway is the fundamental responsibility of the anesthetist.

30% of anesthesia related deaths attributable to inability to manage DA.

Failed Tracheal intubation once in every 2230 attempts

Failed ventilation accounts for 44% of intra operative cardiac arrests

THEREFORE IDENTIFICATION OF DA IS HOLY GRAIL OF CLINICAL MX

INTRODUCTION

Diagnose the potential for difficult airway for optimal patient preparation

Proper equipment and technique selection

Participation of personnel experienced in the difficult airway management.

AIMS and OBJECTIVES

Before getting started!

Difficult Airway : Clinical scenario in

which conventionally trained anesthesiologist experiences difficulty with Face mask ventilation Tracheal intubation Both

It is not possible for the unassisted anesthesiologist to maintain oxygen saturation more than 90% using 100% oxygen and positive pressure mask ventilation in a patient whose oxygen saturation was more than 90%before anesthetic intervention

And/ or it is not possible for the unassisted anesthesiologist to prevent or reverse signs of inadequate ventilation during positive pressure mask ventilation

Difficult Mask Ventillation

2 MAIN REASONS ARE INADEQUATE SEAL INADEQUATE PATENCY OF AIRWAY

INCIDENCE:- 0.08 -5%

DIFFICULT MASK VENTILATION

Difficult LaryngoscopyNot possible to visualize any portion of the vocal cords after multiple attempts at conventional laryngoscopy

More than 3 attempts Longer than 10 minutes Failure of optimal best attemptTracheal intubation requiring multiple

attempts in presence or absence of tracheal pathology.

FAILED INTUBATIONFailure of passage of endotracheal tube after

multiple intubation attempts.

Difficult intubation

Adverse outcomes associated with the difficult airway

◦ Death◦ Brain injury◦ Cardio pulmonary arrest◦ Unnecessary tracheostomy◦ Airway trauma◦ Damage to teeth

PREVENT!!

Painless – JUST SCREENING!! Quick and simple to apply Essentially bedside Less inter examiner variation Reproducible High sensitivity and positive predictive

value

ASSESSMENT ESSENTIALS

HISTORY PHYSICAL EXAMINATION: :--GENERAL PHYSICAL EXAMINATION :--SPECIFIC ASSESSMENT TOOLS

PHYSICAL RADIOLOGICALEXAMINATION ADVANCED

IND

AIRWAY ASSESSMENT

Detect medical, surgical, and anesthetic factors

◦That indicate the presence of a difficult airway

Previous anesthetic records◦History of difficult airway : single most

reliable predictor of a difficult airway

HISTORY TAKING…

Previous anesthetic exposure Snoring/ history s/o OSA Trauma to airway/ neck Burns (airway?) Neck swelling Hoarseness Stridor Previous neck surgery Radiotherapy Systemic diseases : DM/RA

History of piercing???

GENERAL PHYSICAL EXAMINATION

Tounge Palate :

High arched Long &narrow

Elderly/ cachexic : buccal pad of fat

Any burns/ wound Dressings Epidermolysis bullosa Skin grafts

Nares : patency/polyps/DNS

Mouth opening : >3FB

Jaw-deformity/massive/musculatue

Teeth Prominent upper

incisors/canines Edentulous “Buck” teeth

Hair bun : decreased extension of AO Joint prevents sniffing position

Beard : difficulty in mask seal Facial deformities Neck : Short, thick neck difficult intubation(17 in-M ; 16in –F) BMI : > 30 kg/m2

Infections of airway URI Epiglottitis Abscess Croup Bronchitis Pneumonia

Physiologic conditions : Pregnancy

1.The Obese (body mass index > 30 kg/m2) 2.The Bearded 3.The Elderly (older than 55 y) 4.The Snorers 5.The Edentulous

Patients with two or more of there risk factors are likely to have difficult mask ventilation

GROUP INDICES FOR DIFFICULT BMV

Mask seal difficult(receding mandible,facial abn,burn strictures)

Obesity or upper airway Obstruction Advanced age No teeth Snorer

Group indices…

Physical Examination Indices Radiological Indices Advanced Indices

SPECIFIC ASSESSMENT TOOLS

Functions : Rotation of condyle in synovial cavity

(initial 2-3cm of mouth opening) Forward displacement of the condyle :

(further 2-3cm mouth opening)

Tests for TMJ function1. Inter incisor gap (IG)2. Mandible luxation (ML)3. Mandibular protusion test4. Upper lip bite test

TMJ ASSESSMENT

INTER-INCISOR GAP : Ask patient to open mouth Place his 3 fingers (index, middle & ring) Indicates IG >5cm Adequate for direct

laryngoscopy

MANDIBULAR LUXATION : Index finger in front of tragus Thumb in front of the lower part of the

mastoid process Ask patient to open mouth

Index finger enters in space of condyle Thumb feels the sliding of the condyle

TMJ DISPLACEMENT TEST

UPPER LIP BITE TEST : (KHAN ET AL)◦Range and freedom of mandibular

movement & architecture of teeth

◦Class I: Lower incisors can bite upper lip above

vermilion line◦Class II:

Lower incisors can bite upper lip below vermilion line

◦Class III: Lower incisors cannot bite the upper lip

Class III upper lip bite test may have C&L grade III-IV

MALLAMPATI GRADING (1983)

Size of tongue wrt oral cavity How much of the pharynx is obscured by

tongue Patient in sitting pst,observer’ eye at level wid

pt’s mth Maximal mouth opening in neutral position Maximal tongue protrusion without arching No phonation

THE ADEQUACY OF THE OROPHARYNX

ClassIFaucial pillarsUvulaSoft palateHard palate

Class IIUvulaSoft palateHard palate

Class IIIUvula BaseSoft palateHard palate

Class IVHard palate

Samsoon and Young’s modification of the Mallampati classification, a IV class was added

Limitations

Failure to consider Neck mobility Size of the mandibular space Inter-observer variability in

classification.

◦Testing in supine position, phonation and patient’s arching of tongue cause inter-observer variability

Determines ease of alignment of laryngeal and pharyngeal axes when the atlanto-occipital joint is extended

It’s the space ant to larynx. Inadequate exposure of glottis if space

reduced/narrowed as tongue is pushed in here◦MTD◦RHTMD◦MSD◦MHD

ASSESSMENT OF MANDIBULAR SPACE

THYROMENTAL DISTANCE (PATIL TEST) Distance from the tip of thyroid cartilage to

the tip of mandible(mental symphysis) Neck fully extended

• > 6.5cm: no problem with L/I• 6.0 – 6.5cm: without other concomitant

anatomical problems L&I are difficult but possible

• < 6cm: Laryngoscopy may be impossible

RATIO OF HEIGHT TO THYROMENTAL DISTANCE (RHTMD) Modification to improve the accuracy Useful bedside screening test very sensitive predictor of difficult

laryngoscopy RHTMD < 23.5 –easy laryngoscopy

MENTOSTERNAL DISTANCE : (SAVVA TEST) Head in full extension and mouth closed <12.5cm predicts difficult laryngoscopic

intubation sensitivity of test is 0.82 and specificity is 0.89 Considered single best predictorMODIFIED MEASURMENT

Distance between mentum and the hyoid bone

Grade I: > 6.0 cm Grade II: 4.0 – 6.0 cm Grade III: < 4.0 cm

Grade III may be associated with impossible laryngoscopy and intubation.

MENTOHYOID DISTANCE

INDIRECT LARYNGOSCOPIC VIEW Grade 1: Vocal cords visible Grade 2: Posterior commisure visible Grade 3: Epiglottis visible Grade 4: No glottic structures visible

Grade 3 & 4: Predicted difficult This correlates with Cormack and

Lehane’s laryngoscopic view

ASSESSMENT OF GLOTTIC VIEW DURING LARYNGOSCOPY

DIRECT LARYNGOSCOPY VIEW Based on Cormack & Lehane

classification ◦ Grade I: Visualization of entire vocal cords◦ Grade II: Visualization of posterior part of

laryngeal aperture◦ Grade III: Visualization of epiglottis◦ Grade IV: No glottic structures seen

Not a grading system for everyday recording of view at laryngoscopy

MODIFIED C/L CLASSIFICATION {Yentis et al }

Grade I : Same as C&L Grade II a: Partial view of glottis Grade II b: Arytenoids or posterior

part of the vocal cords only just visible

Grade III : Same as C&L Grade IV : Same as C&L

POGO Scoring

Percentage Of Glottic OpeningSeen during D/L

100% : Entire glottic aperture visualized 33% : Lower one third of VC & arytenoids 0% : No glottic structures visible

POGO Scoring Layrngeal Opening

Patient to hold the head erect, facing directly to the front maximal head extension angle traversed by the occlusal surface of upper teeth◦ Grade I : > 35°◦ Grade II : 22-34°◦ Grade III : 12-21°◦ Grade IV : < 12°

For greater accuracy a goniometer is used to measure the angle traversed by upper teeth

ASSESSMENT OF ATLANTO-OCCIPITAL JOINT FUNCTION

Sniffing Position (Mc Gills Position)Normal Alanto occipital extension 35

degrees

Placing two fingers on chin and occipital protuberanceResult

◦Finger on chin higher than one on occiput normal cervical spine mobility

◦Level fingers moderate limitation◦Finger on the chin lower than the second

severe limitation Prayer sign Palm print test

Delilkan’s Test

1. Can place 3 finger breaths between the teeth

2. Between the mandibular genu and hyoid bone

3. Between thyroid cartilage and sternal notch

“ RULE OF THREE’S ”

GROUPING INDICES

Difficult L&I multifactorial problem No simple test can predict difficult

intubation accurately Effective prediction requires a combination

of tests◦Wilson Scoring System◦The Intubation Difficulty Scale (IDS)◦Benumoff’s 11parameter analysis

Risk factor Score  

1. Weight 012

< 90 kg90-100 kg> 110 kg

2. Head & neck movement

012

Above 90°About 90° (i.e. ± 10°)Below 90°

3. Jaw movement 012

IG > 5 cm or S. Lux > 0IG < 5 cm S. Lux = 0IG < 5 cm S. Lux < 0

4. Receding mandible 012

NormalModerateSevere

5. Buck teeth 012

NormalModerateSevere

WILSONS SCORING SYSTEM

THE INTUBATION DIFFICULTY SCALE (IDS)

Subjective and Objective criteria Intubation difficulty defined degree of

divergence from a predefined “ideal intubation” performed without effort on the 1st attempt practiced by one operator using one technique full visualization of the laryngeal aperture and

vocal cords abducted.

PARAMETER SCORE1. No. of attempts > 1 N1

2. No. of operators > 1 N2

3. No. of alternative techniques N3

4. Cormack Grade I N4

5. Lifting force requiredNormal N5=0

sed N5=1

6. Laryngeal pressureNot applied N6=0

Applied N6=1

7. Vocal cord mobilityAbduction N7=0

Adduction N7=1 TOTAL IDS = Sum of scores N1–N7 

Rules for calculating IDS ScoreN1 Every additional attempt adds 1 ptN2 Every additional operator adds 1 ptN3 Each alternative technique adds 1 pt:N4 Apply Cormack grade N6 Sellick’s maneuver adds no points

IDS Score Degree of Difficulty

0 Easy

0 < IDS < 5 Slight difficulty

5 < IDS Moderate to Major difficulty

IDS = Impossible intubation

Benumof’s 11 Parameter for QUICK Analysis

1. Inter-incisor gap : >3cm2. Buck teeth +/-3. Length of incisor: <1.5cm4. Upper Lip Bite5. MMP class6. Palate: arching / narrowing7. TMD: >6cm8. Mandibular compliance9. Neck length: sufficient10.Neck diameter: thin or thick11.Neck movement

LEMON trial Look –anatomical features suggestive of difficulty

Facial trauma Large incisors Beard Large tongue

Evaluate 3-3-2 Interincisor distance (3 fingers) Hyoidmental distance (3 fingers) Thyroid to floor of mouth (2fingers)

Mallampati Obstruction Neck movement – chin to chest-flexion extension

follow a simple mnemonic - FOAM for assessing the difficult bag-mask ventilation.

F: Facial hairs, piercings & deformities [but not limited to] such as burn scarring, growths, emaciated face precluding adequate fit of face mask.

O: Obesity [BMI > 30], Obstructed breathing [history of snoring].

A: Aged > 60 years, Absence of teeth. M: Movement restriction of head & neck [Extension:

cannot look at the ceiling without raising eyebrows; Flexion: cannot touch the chin to the chest] and inability to slide the lower jaw incisors beyond the maxillary jaw incisors.

Assessment for difficult bag-mask ventilation

HAEM for assessing and predicting difficult laryngoscopy & tracheal intubation in patients.

H: History [but not limited to] of past difficult laryngoscopy & intubation, snoring, joint disorders, diabetes mellitus.

A: Appearance [but not limited to] such as short neck, poor dental status, obesity, small or large chin, buck teeth, facial trauma, facial/oral swelling, tumor.

Assessment for difficult laryngoscopy & tracheal intubation:

E: Examination [3-6-12-24]: 3: Assess oral opening for rigid laryngoscopy – <3 cm

inter-incisor space is inadequate for smooth introduction of the laryngoscope blade.

6: Measure the ability of the mandibular space to accommodate the tongue – <6 cm space between the mentum and the thyroid notch is inadequate for compressing the tongue during rigid laryngoscopy.

12: Assess ability to extend the head fully, thereby aligning airway axis for easy laryngoscopy & intubation – <12 cm distance between sternal notch and mentum in a maximally extended head with mouth closed is associated with difficult laryngoscopy.

24: Assess ratio of the patient height to thyromental distance [in cm] for predicting easy laryngoscopy – a ratio of >24 is abnormal and points to difficult laryngoscopy & intubation.

M: Mobility of the head & neck and Mallampati grade II or greater.

DROP for predicting the difficult supraglottic device placement or subsequent ventilation via it.

D: Disrupted upper airway [but not limited to] trauma, ingestion of caustics.

R: Restricted mouth opening [<2 cm]. O: Obstruction of the upper airway [but not

limited to] mass, foreign body, edema. P: Poor lung or thoracic compliance.

Assessment for difficult placement or ventilation via supraglottic device:

RADIOGRAPHIC ASSESSMENT

Lateral cervical x-ray film : head in neutral position

ANTERIOR ATLANTO DENTAL INTERVAL (AADI)

Between posterior surface of arch of C1 Anterior surface of Dens Normal < 3mm adults <5mm Children

ATLANTO-OCCIPITAL GAP : Limits the extension of head on neck Longer the A-O gap, more space for mobility

of head Radiologically there is reduced space

between C1 and occiput <5mm distance

POSTERIOR DEPTH OF THE MANDIBLE : Distance between bony alveolus behind 3rd

molar tooth & lower border of the mandible >2.5 cm predicts difficult L&I

RATIO OF EFFECTIVE MANDIBULAR LENGTH TO POSTERIOR DEPTH <3.6 predicts difficult L&I

DIFFERENT PATHOLOGIES ACQUIRED OR CONGENITAL CAN BE PICKED UP

Seldom used clinically. These are:

a) Flow volume loops b) Acoustic reflectometry c) Ultrasound d) MRI

ADVANCED INDICES

TEST SENSTIVITY SPECIFICITY PPV

Mouth Opening 26-47 94-95 7-25

Jaw protrusion 17-26 95-96 5-21

Mallampati (original) 62 25 16

Mallampati (modified) 65-81 66-82 8-9

TMD 62 25 16

TMD + MMP 81 98 64

Mento sternal distance 82 89 27

Neck movement 10-17 98 64

Wilsons scoring 42-55 86-92 6-9

Indirect Laryngoscopy 69 98 31

No single airway test provides a high index of sensitivity and specificity

Combination of multiple tests a MUST!

Some with difficult airway will remain undetected

Pre-formulated and practiced plans for unanticipated difficult airway

CONCLUSION

Thank You