M5 THE DIFFICULT AIRWAY

Question 1

Verifying the presence of sustained exhaled CO2 requires the following criteria to be met (4)

Answer 1

• Amplitude rises during exhalation and falls during inspiration
• Consistent or increasing amplitude over at least 7 breaths
• Peak amplitude more than 7.5mmHg above baseline
• Reading is clinically appropriate

Question 2

Causes of exhaled CO2 detection despite oesophageal placement

Answer 2

no alveolar ventilation occuring
- prior ingestion of carbonated beverages or antacids
- gastric insufflation
-pronlonged venitlation with SGA or facemask prior
- bystander rescue breaths

some alveolar ventilation potentially occuring
- tracheo-oesophageal fistula with tube tip proximal to fistula
-proximal oesphageal intubation with uncuffed tube in paed

Question 3

cardiac arrest as a confounder

Answer 3

• An exhaled co2 partial pressure <7.5mmhg is highly unlikely after tracheal intubation in a patient who has a spontaneous cardiac output
• In CA a reading <7.5 would indicate an incorrect tube or very high likelihood for poor outcome from resuscitation

Question 3

bronchospasm as a confounder

Answer 3

• Severe bronchospasm has anecdotally been described as a cause for absent exhaled carbon dioxide and often features as a presumptive alternative cause for the absence of sustained exhaled carbon dioxide in cases of unrecognised oesophageal intubation
• However, in the presence of adequate airway pressures and prolonged expiratory time, bronchospasm is extremely unlikely to result in an inability to satisfy the criteria for sustained exhaled carbon dioxide. If sustained carbon dioxide is not obtained, bronchospasm should not be assumed to be the cause and oesophageal intubation must be excluded.

Question 4

quick check to identify causes of no “sustained exhaled” co2 other than oesophageal intubation

Answer 4

• confirm function of CO2 detection device
• replace all equipment proximal to the tube
• exclude leak around tube (inflate cuff)
  -assess tube patency (suction device)
  -ensure adequate inspiratory pressure and expiratory time (attempt ventilation with increased inspiratory pressure and allow prolonged expiratory time)
• check pulse (confirm SPO2 trace here too)

Question 5

Repeated interventions to optimise a success at a lifeline may contribute to harm by two mechanisms

Answer 5

trauma - repeated airway instrumentation may result in trauma that will impede ability to enter the green zone
time - consumes time and can prolong the time to enter the green zone = increase the duration and severity of hypoxaemia

Question 6

what is the point of measuring the incisor gap and how do you do it

Answer 6

measurement of the TMJ and upper cervical mobility as well as the ability to instrument the airway

3 fingers in the mouth between top and bottom teeth

Question 7

how to measure thyromental distance and what does it tell you

Answer 7

assessment of the length of the mandibular space

3 fingers from the chin to the neck

Question 8

how to measure the hyomental distance and what does it tell you

Answer 8

chin to the hyoid bone

assessment of the position of the glottis in relation to the base of the tongue

Question 9

airway assessment - cervical spine movement

Answer 9

assesses head and neck mobility / head extension

Question 9

what does mallampatti score tell us

Answer 9

size of tongue in relation to oropharyngeal space