The 6D of Airway Management

The 6D of Airway Management

Assessment of the airway is recommended to predict the presence of a difficult airway before beginning airway management. The Mallampati classification system was implemented as a method to predict difficult intubation. However, its reliability as a predictor of difficult intubation has been questioned , and it assesses only one aspect of the airway for difficulty (i.e., intraoral disproportion). 

A comprehensive airway examination incorporates both quantitative and qualitative tests that together may increase the probability of predicting difficult intubation. One such system, the “6-D” method, introduced to examine the airway for six separate signs that can be associated with difficult intubation:

1. Disproportion 
2. Distortion 
3. Decreased thyromental distance 
4. Decreased interincisor gap 
5. Decreased range of motion, and 
6. Dental overbite

Airway assessment is beneficial in that it can alert practitioners to the presence of a potentially difficult intubation, thus allowing them either to attempt intubation using a difficult-airway intubation technique from the outset or to proceed using a standard direct laryngoscopy technique while simultaneously being prepared to apply an intubation rescue technique or an adjunctive ventilation technique should intubation or ventilation prove to be difficult.

Disproportion

• Increased size of tongue in relation to pharyngeal size 
• Airway swelling
• Airway trauma (blunt or penetrating) 
• Tissue consolidation (e.g., secondary to radiation ) , Tracheal deviation

Distortion

• Neck mass , Voice changes 
• Neck hematoma , Subcutaneous emphysema (crepitus) 
• Neck abscess , Laryngeal immobility
• Arthritic changes in the neck joints , Non palpable thyroid cartilage 
• Previous surgical airway , Non palpable cricoid cartilage

Decreased thyromental distance

• Anterior larynx and decreased mandibular space 
• Thyromental distance >7 cm (˜3 finger breadths) measured from the superior aspect of the thyroid cartilage to the tip of the chin 
• Receding chin

Decreased interincisor gap

• Reduced mouth opening 
• Distance between upper and lower incisors (i.e., interincisor gap) <4 cm (<2 finger breadths) 
• Mandibular condyle fracture 
• Rigid cervical spine collar

Decreased range of motion or airway joints

i.e., atlanto-occipital joint, temporomandibular joints, cervical spine) , atlantooccipital range of motion is critical for assuming the sniffing position. 

• Limited head extension secondary to arthritis, diabetes, or other diseases 
• Head extension <35°
• Previous neck radiation and/or radical surgery 
• Neck flexion <35°
• Neck contractures secondary to burns or trauma 
• Short, thick neck 

Dental overbite 

• Large angled teeth disrupting the alignment of the airway axes and possibly decreasing the interincisor gap.

The choice of a difficult-airway intubation technique is dependent on the clinical situation and the practitioner's familiarity and skill in using any particular device. Not every difficult airway technique must be learned or mastered, but it is best to be familiar with more than one technique in order to increase the likelihood of success.

Source : www.ncbi.nlm.nih.gov