Conquering the Difficult Airway

In every medic's practice, one of the most challenging cases is the patient with a difficult airway. What do we mean by "difficult airway"? Basically, it is an airway that is hard to manage due to anatomy or medical conditions that make ventilation or intubation more difficult than normal. An article in this publication a year ago stated, "An experienced EMS provider will tell you that, when treating a patient, the three most important considerations are airway, airway, airway."¹ That has not changed. The challenge for medics is to be prepared for the difficult airway patient. This means understanding the causes for a difficult airway and having a wide spectrum of skills, techniques and tools available to manage it.

You and your partner arrive at a local park to find an approximately 30-year-old, obviously pregnant patient who was stung by a bee about 15 minutes previously. She is in obvious respiratory distress, with audible wheezing and stridor and a respiratory rate greater than 30 breaths per minute. Her husband tells you she is in her 33rd week of pregnancy and that immediately after the sting she began to itch, the skin on her chest and neck turned red, and her lips began to swell. She is conscious and frightened. She says, "Please don't let me and my baby die."

As in any airway situation, the first task is assessment. Realizing that a pregnant patient can present a challenge for intubation, you ask your partner to apply a non-rebreather mask and administer oxygen at 15 liters per minute, start an IV, administer diphenhydramine, and prepare to administer epinephrine 1:1,000 subcutaneously if it should become necessary.² Then you begin to review the problems you are confronting.

The first thing you remember is that the incidence of failed intubations in the obstetric patient is approximately 13 times higher than in the non-pregnant patient.^3,4 Such statistics are not reassuring, so you begin assessing the patient's airway for potential difficulty. Forewarned is forearmed.

ASSESSING THE AIRWAY
The "6-D" method of assessment, where "D" is for difficulty, can help to estimate the difficulty of laryngoscopy. While no single "D" sign alone would indicate difficulty, the more "D" signs that are present, the higher the likelihood of difficult laryngoscopy.^5,6

The six "D"s are:

• Distortion
• Disproportion
• Decreased thyromental distance
• Decreased inter-incisor gap
• Decreased range of motion
• Dental overbite.

Distortion refers to any variances caused by altered anatomy, disease or trauma that change the normal appearance of the airway. Distortion can include airway swelling, airway trauma, tumors, hematomas, abscesses, arthritic changes in the body structure and scarring from a previous surgical airway. Airway swelling is obviously present in this patient.⁶

Disproportion refers to increased tongue size in relation to the size of the oral cavity, as in a patient with Down syndrome. Another condition that results in disproportion of the airway is Pierre Robin sequence or syndrome, a condition present at birth marked by a very small lower jaw (micrognathia), a large-appearing tongue that tends to fall back and downward (glossoptosis), and often a cleft palate. This condition resolves somewhat as the jaw grows, but can cause significant airway problems in neonates and young children.⁷

Decreased thyromental distance refers to the distance from the tip of the chin to the superior aspect of the thyroid cartilage (the upper portion of the larynx). If the thyromental distance is less than 7 cm or 3 fingerbreadths, this would be another positive "D" sign.⁶