I. Prediction of the difficult airway. In 1200 prospectively studied patients in an article by Latto IP. and Rosen M., it was shown of 84 patients predicted to have problem, only 22 (25%) actually had a problem of 43 actual difficult intubations incurred, only 22 (51%) were predicted.

Three lessons are learned from these results.

First - a detailed history of the patients past airway problems must be sought.

Second - to improve positive and negative predictive values of airway examinations all possible measurements must be taken into account.

Third - to have the knowledge and experience to overcome the "unpredicted difficult airway". This means learning practical airway management skills in an environment that is not urgent, stressful or life threatening i.e. at a course such as this!!

A. History - Obtain detailed history from patient and, if necessary, family or medical records, i.e.:

previous difficult intubation

congenital abnormalities

previous airway trauma

previous airway surgery

medical conditions, i.e. ankylosing spond/rheumatoid arthritis

B. Airway Examination - This should be conducted in an orderly fashion with a set of tools to aid measurements, i.e. light, centimeter ruler, bubble inclinometer and special investigations.

Order of examination:

Nares

Cervical spine

Temperomandibular joint

Mandibular-mental dist.

Mallampati

Hyomental dist.

Laryngeal lateral movement.

Laryngeal tilt

Auscultation

II. Initial Evaluation of the Airway

Upon arrival in the emergency situation the overall status of the patient must be assessed immediately. ABCs:

Airway -- Is the airway clear and patent??

Breathing -- Is the patient breathing spontaneously? With adequate tidal volume? Are the breath sounds clear? Is ventilation sufficient?

"Color" -- Is the patient oxygenated?

Skin color pink?

Oxyhemoglobin saturation?

Coexisting disease --

Consciousness/cranial pathology?

Hemodynamic stability

Cardiovascular disease

Coagulopathy

"Full stomach"

Trauma

Obesity

Surgical problems

Decision -- Is this urgent? Time frame?
III. The Technique Oriented Airway Examination
When there is a need to secure the airway there is a need to assess the likelihood of one of the following airway management techniques to be successful. The history and examination must answer the question: "Will the abnormality discovered make one of these particular techniques difficult?

A. Mask ventilation will be made difficult by:
poor mask seal --

beards

facial burns

facial scarring/cuts

facial dressings

edentulous patients

any evidence of airway obstruction

neck instability

penetrating neck trauma

repeated failed direct laryngoscopy

obesity/bull neck

B. Other ventilation techniques will be made difficult by:

lack of knowledge and experience

lower airway obstruction

neck instability

penetrating neck injury

C. Direct laryngoscopy will be made difficult by:

decreased mobility cervical spines

tempero-mandibular jt larynx decreased visualization oral structures

mandibular structures laryngeal tilt dentition secretions airway obstruction pharyngeal

laryngeal tracheal D. Indirect laryngoscopy will be made difficult by:

lack of knowledge and experience

nasal obstruction

neck instability

secretions

E. Fiberoptic laryngoscopy will be made difficult by:

lack of knowledge and experience

nasal obstruction

base of skull fractures (nasal route)

secretions

F. Cricothyroidotomy/airway surgery will be made difficult by:

coagulopathy

lack of knowledge and experience

soft tissue neck injury

obesity/"bull neck"

confused and combative patient

IV. Reference Articles

1. Clinical Anesthesia Updates Vol.5 Number 3. Barash Cullen and Stoelting.

2. Mallampati SR.et al. A Clinical sign to predict difficult intubation:a prospective study. Can Anaesth Soc J 1985;32:4,429-434.

3. McIntyre JWR,The difficult tracheal intubation.CME.Can J Anaesth 1987;34:2,204-213.