Preoperative AirwayAssessmentDr MANISH KHANDELWALSMS MEDICAL COLLEGEMODERATORDr AMIT KULSHRESTHA
AirwayThe passage through which the air passes during respiration Nasal and oral cavities Pharynx Larynx Trachea and large bronchi
Why it is necessary ?? Respiratory events are the most common anaesthetic related injuries, following dental damage. Three main causes: ◦ Inadequate ventilation ◦ Oesophageal intubation ◦ Difficult tracheal intubation Difficult tracheal intubation accounts for 17% of the respiratory related injuries and results in significant morbidity and mortality. Estimated that up to 28% of all anaesthetic related deaths are secondary to the inability to mask ventilate or intubate. Prediction of the difficult airway allows time for proper selection of equipment, technique and personnel
Difficult airwayASA definition of difficult airway: ―The clinical situation in which a conventionally trained anaesthetist experiences difficulty with mask ventilation, difficulty with tracheal intubation or both.‖
Difficult ventilation The inability of a trained anesthetist to maintain the oxygen saturation > 90% using a face mask for ventilation and 100% inspired oxygen, provided that the pre-ventilation oxygen saturation level was within the normal range.
Difficult intubation More than 3 attempts Longer than 10 minutes Failure of optimal best attempt
Prevalence Difficult face mask ◦ 0.1% - 5% Difficult LMA ◦ 0.2% - 1% Difficult intubation ◦ 1-2% of normal surgical population ◦ 50% of rheumatic cervical disease
Components of the AirwayExamination Nostril patency Length of the upper incisors, alignment Condition of the teeth Relationship of the upper (maxillary) incisors to the lower (mandibular) incisors Ability to protrude or advance the lower (mandibular) incisors in front of the upper (maxillary) incisors Interincisor or intergum (if edentulous) distance Tongue size Visibility of the uvula e.g. mallampati Presence of heavy facial hair Compliance of the mandibular space Thyromental distance with the head in maximum extension Length of the neck Thickness or circumference of the neck Range of motion of the head and neck Cheek pad
Causes of difficult airway Stiffness ◦ Arthritis of neck/jaw/larynx. ◦ Fixation devices ◦ Scleroderma ◦ Diabetes Deformity ◦ Cervical and craniofacial ◦ Burns/trauma/infection Swelling ◦ Infection/tumour/trauma/burns ◦ Anaphylaxis/haematoma/acromegaly Reflexes ◦ Cough/breathholding ◦ Laryngospasm/salivation/regurgitation Foreign body Other – Pregnant/full stomach
Airway assessment History ◦ Patient/notes/chart/medic-alert/spam letter Difficulty Surgery/burns Concurrent disease Reflux/recent meals General examination ◦ Do they just look difficult? Dentition (prominent upper incisors, receding chin) Distortion (edema, blood, vomits, tumor, infection) Disproportion (short chin-to-larynx distance, bull neck, large tongue, small mouth) Dysmobility (TMJ and cervical spine) ◦ Massively obese or pregnant ◦ Beards +/- tubes Specific tests/indices Investigations. ◦ Nasoendoscopy ◦ X-ray, CT/MRI ◦ Flow volume loop
How do you assess ??The airway may be assessed for difficult airway using :--Individual indices-Group indices(with and without scoring)Mask ventilation precedes laryngoscopy, which inturn followed by, intubation.So the assessment should be in a systemic manner.
Predictors of difficulty to face mask ventilate (OBESE)1. The Obese (body mass index > 26 kg/m2)2. The Bearded3. The Elderly (older than 55 y)4. The Snorers5. The Edentulous (=BONES)
Predictors of difficulty to facemask ventilate (MOANS) MOANSThis is identicle to BONES except ‗M‘.-Mask seal difficult due to receding mandible,syndromes with facial abnormalities,burn stricture etc.-Obesity, upper airway Obstruction-Advanced age-No teeth-Snorer
Predictors of difficultlaryngoscopy and intubationIndividual indices -Physical examination indices -radiological indices -advanced indicesGroup indices - Wilson‘s score - Benumof‘s analysis - Saghei & safavi test - Lemon assesment - Arne‘s simplified score - Magboul‘s 4 M‘s
Atlanto-occipital movement The patient is asked to hold head erect, facing directly to the front, then he is asked to extend the head maximally and the examiner estimates the angle traversed by the occlusal surface of upper teeth. ◦ Visual assessment or using a goniometer. Grade I >35 degrees Grade II 22-34 degrees Grade III 12–21 degrees Grade IV <12 degrees Assesses feasibility to make the optimal intubation position with alignment of oral, pharyngeal and laryngeal axes into a straight line. Limited A-O joint extension ◦ Spondylosis, rheumatoid arthritis, halo-jacket fixation, and in patients with symptoms indicating nerve compression with cervical extension.
Grading of reduction in A.O.Extension Grade I : > 35° Grade II : 22-34° Grade III : 12-21° Grade IV: < 12° Grade Reduction of A.O.Extension 1 none 2 One third 3 Two third 4 complete Grades 3 and 4 : Difficult laryngoscopy
• ASSESMENT OF A.O. EXTENSION can also be done by asking the patient to look at the floor and at wall after fully flexing and fixing the neck as shown • Flexion movement of the cervical spine can be assessed by asking the patient to touch his manubrium sternii with his chin. If done, the above maneuver assures a neck flexion of 25- 35 degree. Flexion and the extension movement if within the normal range ,three axis ( oral,pharyngeal & laryngeal axis) can be brought
Warning sign of DELIKANPlace the index finger of each hand, one underneath the chin and one under the inferior occipital prominence with the head in neutral position. The patient is asked to fully extend the head on neck. If the finger under the chin is seen to be higher than the other, there would appear to be no difficulty with intubation. If level of both fingers remains same or the chin finger remains lower than the -: other, increased difficulty is predicted.
PRAYER SIGN A positive "prayer sign" can be elicited on examination with the patient unable to approximate the palmar surfaces of the phalangeal joints while pressing their hands together. Seen in diabeties; This represents:- cervical spine immobility and the potential for a difficult endotracheal intubation.
Palm Print testThe palm and fingers of the dominant hand of thepatient is painted with black writing ink using a brush. The patient then presses the hand firmly against a whitesheet of paper on a hard surface. Scoring is done as: * Grade 0 - All phalangeal areas visible. * Grade 1 - Deficiency in the inter-phalangeal areas of 4th and/or 5thdigit. * Grade2 - Deficiency in the inter-phalangeal areas of 2nd to 5th digit. * Grade 3 - Only the tips of digits seen.
Palm Print as a Predictor ofDifficult Airway in DM
ASSESSMENT OF TMJ FUNCTION TM joint exhibits 2 function. 1. Rotation of the condyle in the s.cavity. 2. Forward displacement of the condyle. First movement is responsible for 2-3cm mouth opening & the second is responsible for further 2-3cm mouth opening.SUBLUXATION OF THE MANDIBLE Index finger is placed in front of the tragus & the thumb is placed in front of the the lower part of the mastoid process. patient is asked to open his mouth as wide as possible. Index finger in front of the tragus can be intented in its space and the thumb can feel the sliding movement of the condyle as the condyle of the mandible slides forward.
Significance-Class B and C: difficult laryngoscopy
Assessment of mandibularspace can be expressed as thyromental and hyomental space. This space determines how easily the laryngeal and pharyngeal axis will fall in line when the a-o joint is extended.
Thyromental DistanceMeasure from upper edge of thyroidcartilage to chin with the head fullyextended. Normal is approx 7cm.If the thyromental distance is short, <3finger widths, the laryngeal axis makesa more acute angle with the pharyngealaxis and it will be difficult to achievealignment.Less space to displace thetongue
Limitations Little reliability in prediction Variation according to height, ethnicity Modification to improve the accuracy Ratio of height to thyromental distance (RHTMD) Useful bedside screening test RHTMD > 23.5 – very sensitive predictor of difficult laryngoscopyThyromental Distance PATIL’S TEST
HYO MENTAL DISTANCE Distance between mentum and hyoid bone Grade I : > 6cm Grade II: 4 – 6cm Grade III : < 4cm – Impossible laryngoscopy & Intubation
INTER-INCISOR GAP Inter-incisor distance with maximal mouth opening Normal value > 5 cm / admits 3 fingers. Significance : Positive results: Easy insertion of a 3 cm deep flange of the laryngoscope blade < 3 cm: difficult laryngoscopy < 2 cm: difficult LMA insertion Affected by TMJ and upper cervical spine mobility
STERNOMENTAL DISTANCE (SAVVATEST) Distance from the upper border of the manubrium to the tip of mentum, neck fully extended, mouth closed Minimal acceptable value – 12.5 cm Single best predictor of difficult laryngoscopy and intubation ( Has high sensitivity & specificity).
UPPER LIP BITE /CATCH TEST Class I: Lower incisors can bite the upper lip above vermilion line Class II: can bite the upper lip below vermilion line Class III: cannot bite the upper lipSignificance Assessment of mandibular movement and dental architecture Less inter observer variability
Test for assessing adequacy ofthe oropharynx for laryngoscopyand intubation Mallampati grading (samsoon and young‘s modification) Narrowness of the palate
Sensitivity: 44% - 81% Mallampati Score Specificity: 60% - 80% Roughly corresponds to Cormack and Lehane‘s laryngoscopy views Class I (easy)—visualization of the soft palate, fauces, uvula, and both anterior and posterior pillars Class II—visualization of the soft palate, fauces, and uvula Class III—visualization of the soft palate and the base of the uvula Class IV (difficult)—the soft palate is not visible at all
SIGNIFICANCE OF MMP SCORE Class III or IV: signifies that the angle between the base of tongue and laryngeal inlet is more acute and not conducive for easy laryngoscopy Limitations ◦ Poor interobserver reliability ◦ Limited accuracy Good predictor in pregnancy, obesity, acromegaly
Assessment for quality of glotticviewing during laryngoscopyIndirect mirror laryngoscopic viewDirect laryngoscopy ‗awake look‘ -cormack and lehane gradingGrading ease of intubationPOGO (percentage of glottic opening) scoring
CORMACK - LEHANE Grading at direct laryngoscopy Grade 1: Full exposure of glottis (anterior + posterior commissure) Grade 2: Anterior commissure not visualised Grade3: Epiglottis only Grade 4: No glottic structure visible. Grade I = success & ease of intubation
Group indices - Wilson‘s score - Benumof‘s analysis - Saghei & safavi test - Lemon assesment - Arne‘s simplified score - Magboul‘s 4 M‘s - 4D‘s
Wilson‘s risk score Score • Head movement assessedWeight 0=<90kg with pencil taped to a 1=>90kg patient’s forehead. 2=>110kg •IG = Interincisor gapHead and 0=Above 90degreesneck 1=About 90degrees measured with mouth fullymovement 2=Below 90degrees open.Jaw 0=IG>5cm or SLux >0 •SLux = Maximal forwardmovement 1=IG<5cm and SLux = 0 2=IG<5cm and SLux<0 protrusion of the lower incisors beyond the upperReceding 0=Normalmandible 1=Moderate incisors. 2=Severe •score 5 or < =easy laryngoscopyBuck teeth 0=Normal •Score 8-10 =severe difficulty in 1=Moderate laryngoscopy 2=Severe
BENUMOF’S 11 PARAMETER ANALYSIS Parameter Minimum acceptable value 1. Buck teeth <1.5cm 2. Subluxation Absent 3. Interincisor gap Yes 4. Palate configuration >3cm 5. Mallampati class No arching/narrowness 4-2-2-3 rule 6. Upper inciors length <2 4 for tooth 7. TM distance > 5cm 2 for inside of mouth 8. SMS compliance Soft to palpation. 2 for mandibular space 9. Neck thickness Qualitative ( >33cm DI) 3 for neck examination. 10. Length of neck >8cm 11. Head /neck mvt Normal range
SAGHEI & SAFAVI’S Weight >80kg Tongue protrusion < 3.2cm Mouth opening <5cm Upper incisor length >1.5cm Mallampati class >1 Head extension <70 degreeAny 3 indices if present Prolonged laryngoscopy -
Arne’s simplified score model The points of simplified score were obtained by multiplying the points of the exact score by 3.15 and then rounding the results to the nearest whole number. Risk factor simplified score Previous knowledge of difficult intubation No 0 Yes 10 Pathologies associated with difficult intubation No 0 Yes 5 Clinical symptoms of airway pathology No 0 Yes 3 Inter-incisor gap (IG) and mandible luxatum (ML) IG > 5 cm or ML >0 0 IG 3.5-5cm and ML=0 3 IG<3.5 cm and ML<0 13
Arne’s simplified score contd. Thyromental distance simplified score >6.5cm 0 < 6.5cm 4 Maximum range of head & neck movement Above 100° 0 About 90° (90° ± 10°) 2 Below 80° 5 Mallampati’s modified test Class 1 0 Class 2 2 Class 3 6 Class 4 8 Total...... 48Score of >11 is predictive of difficult tracheal intubationIndian journal of anaesthesia,2002; 46(5) 347-352
LEMON trial Look 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( Airway management in traumaIndian J Anaesth. 2011 Sep-Oct; 55(5): 46)3–469)
LOOK Externally Beards or facial hair Short, fat neck Morbidly obese patients Facial or neck trauma Broken teeth (can lacerate balloons) Dentures (should be removed) Large teeth Protruding tongue A narrow or abnormally shaped face
EVALUATE 3-3-2 Mouth Opens at least 3 finger widths. Three finger widths thyromental distance. Two finger widths mandibulohyoid distance.
Upper & Lower Face Measure the size of the upper face as compared to the lower face. Should be roughly the same. If the lower face is longer than the upper face then you should anticipate some degree of difficulty lining up the structures
Obstruction Laryngoscopy or intubation may be more difficult in the presence of an obstruction ◦ Anatomy ◦ Trauma ◦ Foreign body obstruction ◦ Edema (burns)
Neck Mobility Ideally the neck should be able to extend back approximately 35 Problems: ◦ Cervical Spine Immobilization ◦ Ankylosing Spondylitis ◦ Rheumatoid Arthritis ◦ Halo fixation
Scene and Situation (SEE) Scene safety Environment ◦ Do you have a reasonable chance to get the tube? ◦ Space, positioning, access Egress ◦ Will you be able to ventilate during egress?
Magboul‘s 4 M‘s For Intubation remember the 4(M & Ms) with (STOP) sign Mallampati Measurement Movement Malformation & STOP M =Malformation of the skull, teeth, obstruction, & Pathology (the Macros and Micros). We can memorize them with the word (STOP) S = Skull (Hydro and Microcephalus) T = Teeth (Buck, protruded, & loose teeth. Macro and Micro mandibles) O= Obstruction (due to obesity, short Bull Neck and swellings around the head and neck) P = Pathology (Craniofacial abnormalities & Syndromes: Treacher Collins, Goldenhars, Pierre Robin, Waardenburg syndromes) . (The Internet Journal of Anesthesiology. 2005 Volume 10 Number 1. DOI: 10.5580/1d0a)
What are the 4 Ds?The following Four Ds also suggest a difficult airway: Dentition (prominent upper incisors, receding chin) Distortion (edema, blood, vomits, tumor, infection) Disproportion (short chin-to-larynx distance, bull neck, large tongue, small mouth) Dysmobility (TMJ and cervical spine)
RADIOGRAPHIC PREDICTORS 1. X-Ray neck (lateral view) : Occiput - C1 spinous process distance< 5mm. Increase in posterior mandible depth > 2.5cm. Ratio of effective mandibular length to its posterior depth <3.6. Tracheal compression.
2. CT Scan: Tumors of floor of mouth, pharynx, larynx Cervical spine trauma, inflammation Mediastinal mass 3. Helical CT (3D-reconstruction): Exact location and degree of airway compression ADVANCED INDICES• Flow volume loop• Acoustic response measurement• Ultra sound guided• CT / MRI• Flexible bronchoscope
DOA Difficult Airway DOA ◦ Disruption or Distortion ◦ Obstruction ◦ Access Problems
DOA Obstructions Hematoma Abscess Tumor ◦ Tumors can also create distortions & extra bleeding
DOA Access Issues Obesity Halo Short neck SC Emphysema Bushy beard Flexion deformity of the spine
How to predict difficult placementof supraglottic devices (RODS) Restricted mouth opening Obstruction of the upper airway Distrupted upper airway as following trauma,burn,caustic ingestion . Stiff lung (poor lung or thoracic compliance)Suggested by Hung and Murphy(Canadian journal of anesthesia 2004:10:963-8)
How to predict difficulty increating surgical airway (BANG) Bleeding tendency Agitated patient Neck scarring Growth or vascular abnormality in region of surgical airway.
Why would this man’s airwaybe difficult to manage?
COPUR index assessing difficult airway inpaediatric patient C-chin From the side view the chin is: score Normal 1 Small, moderately hypoplastic 2 Markedly recessive 3 Extremely hypoplastic 4 O-Opening of the mouth(Interdental space) > 40mm 1 20-40 mm 2 10-20mm 3 <10 4 P-Previous Intubation or OSA Previous attempt easy 1 No previous attempt, no hx OSA 2 OSA, previous hx difficult intubation 3 Extremely difficult previous intubation, trach, or patient unable to lie supine 4
COPUR index (contd) U-Uvula (Mouth open tongue out) Tip of uvula visible 1 Uvula partially visible 2 Uvula concealed, soft palate visible 3 Soft palate not visible 4 R Range (estimaterange of motion looking up and down) >120° 1 60°-120° 2 30°-60° 3 < 30° 4 Prediction Points 5-7 Easy normal intubation score >10 predict difficult airway 8-10 laryngeal pressure may help 12 more difficult, fiberoptic may be less traumatic 14 Difficult intubation, fiberoptic or other advanced technique 16 Dangerous airway, consider awake intubation, potential trach
Structured Approach to Airway Management MOUTHSComponent Description Assessment ActivitiesMandible Length and subluxation Measure hyomental distance and anterior displacement of mandibleOpening Base, symmetry, range Assess and measure mouth opening in centimetresUvula Visibility Assess pharyngeal structures and classifyTeeth Dentition Assess for presence of loose teeth and dental appliancesHead Flexion, extension, rotation of head/neck and cervical Assess all ranges and movement spineSilhouette Upper body abnormalities, both anterior and posterior Identify potential impact on control of airway of large breasts, buffalo hump, kyphosis, etc.
Rule of 1-2-3 1 finger breadth for subluxation of mandible. Just to recall 2 finger breatdh for adequacy of mouth opening. 3 finger breathd for hyomental distance. In emergency situation, above test can be rapidly performed within 15sec to assess the TMJ function,mouth opening and SM Space. Significant difficulty in 2 or more of these components requires detailed examination. Rule of 1-2-3-4-5• 4 finger breath for thyromental distance• 5 movements- ability to flex the neck upto the manubrium sterni, extension at the AOJ, rotation of the head along with right & left movement of the head to touch the shoulder. RULE OF THREE`S • 3 finger in the interdental space. • 3 finger between mentum and hyoid bone. • 3 finger between thyroid cartilage & sternum.
To Summarize Airway assessment is a critical part . The difficult airway assessment must be performed prior to ALL attempts. While this criteria helps identify difficult airways, it does not guarantee an easy intubation—Be Prepared! Nothing is more expensive than the missed opportunity
References Airway management in trauma Indian J Anaesth. 2011 Sep-Oct; 55(5): 463–469. The Internet Journal of Anesthesiology ISSN: 1092-406X The Dilemma of Airway Assessment and Evaluation Magboul M. Ali Magboul MD, FFARCSIClinical Assistant Professor, Director of ACLS, PALS & Airway workshop, Department of Anesthesia, University of IowaIowa City, Iowa U.S.A. Citation: M.M. Ali Magboul: The Dilemma of Airway Assessment and Evaluation.The Internet Journal of Anesthesiology. 2005 Volume 10 Number 1. DOI: 10.5580/1d0a 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 2003; 98 (5):1269-77 Frerk CM. Predicting difficult intubation. Anaesthesia 1991; 46 (12):1005-8 Verghese C, Brimacombe JR. Survey of laryngeal mask airway usage in 11,910 patients: safety and efficacy for conventional and nonconventional usage. Anesth Analg 1996; 82: 129–33 Gupta S, Sharma R, Jain D. Airway assessment – Predictors of a Difficult Airway. Indian Journal Of Anaesthetics 2005; 49(4) : 257 -262