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Evaluation of the airway


How to recognize a potentially difficult airway?


The Anesthesiologist is responsible for:

  • recognize a potentially difficult airway,

  • activate a prepared plan to solve the problem.


The patient’s safety should be guaranteed in all situations where an intubation failure is present.


During the pre anesthetic visit, the previous patient`s story, associated pathologies

and physical examination will call attention to the potential problems possible to happen

during the maneuvers necessary to keep a free and safe airway.


The medical files describing previous anesthesias and the history showing problems

with intubation,  will give important clues for the possible difficulties that may arise with the

programmed procedure.




 Preanesthetic evaluation of the airway

 Acceptable findings and its meaning




Acceptable findings


inter-incisive distances

over  3 cm


there is room enough to position the blade between

the superior and inferior dental arcade

lenght of the superior incisives

short incisives

long incisives:

the laryngoscope blade is oriented cephalad


mallampati test classificaltion

less or equal to II

small tongue in relationship

to the oropharynx


palate anatomy

must not be too narrow,

too straigh or too high arched

a narrow palate decrease the oropharynx volume-less room for the blade and endotracheal tube


situation of maxilar and mandibular incisives during the normal closure of the mandible 






maxilar teeth do not pass over the

line of the mandibular ones

(evaluation in lateral position)


maxilar arcade anterior to the mandibular teeth (protusion of the superior arcade): the blade follows a cephalad diretion


voluntary protusion

of the mandibule 

mandibular teeth pass

over the maxilar ones,

(lateral position)



motility of the temporomandibular joint: allows anterior dislodgement

of the mandible during laringoscopy

thyromental distance







    3 finger breadths,  6 cm in adults


if this thyromental distance is short (< 3 finger breadths,

or < 6 cm in adults)


the laryngeal axis makes a more acute angle with the pharyngeal axis, and it will be difficult to achieve alignment

check neck extension

on to the chest



















flexion of the neck

over the thorax with 35º


 extension of the head over

the neck of 80º


limitation of neck extension

(< 30 degrees) may interfere with the sniffing position and limit the laryngoscopic view

mandibular space complacency



digitial depression is possible



check if the tongue fits the mandibular gap during laringoscopy

neck lenght


subjective evaluation

a short neck difficults the right alignent of the axis during laryngoscopy


wideness of the neck

subjective evaluation

a gross neck makes difficult the alignement of the axis during laryngoscopy


Predicting Difficult Intubation in Apparently Normal Patients
A Meta-analysis of Bedside Screening Test Performance

Anesthesiology, V 103, No 2, Aug 2005



Pictures produced by:

Dr. José Octávio G. Freitas*  and Dr. Leandro de Oliveira Chiarelli

*Serviços Integrados de Cirurgia Plástica

Hospital Ipiranga   São Paulo - Brazil


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