Why is obstetric airway management more difficult?

Obstetric patients are at increased risk of failed intubation due to a number of unique clinical, environmental and human factors. Despite widely publicised ‘failed intubation drills’ and advances in airway equipment and techniques, the incidence of failed obstetric tracheal intubation has not changed for more than 40 years, and remains higher than in the non-obstetric population. A recent literature review found an incidence of failed tracheal intubation of 2.6 per 1000 obstetric general anaesthetics (1 in 390) and associated maternal mortality of 2.3 per 100 000 general anaesthetics (one death for every ninety failed intubations). Given the difficulties in accurately predicting difficult intubation, and the unchanged rate of failed obstetric tracheal intubation, there has been a shift in focus away from efforts to primarily reduce rates of failed intubation towards a greater appreciation of measures to maintain oxygenation and to control associated human factors that may impact on delivery of safe airway management. These are described in recent UK obstetric-specific airway guidelines jointly published by the Obstetrics Anaesthetists’ Association (OAA) and Difficult Airway Society (DAS) and are explored in the following article.

Why is obstetric airway management more difficult? 

Anatomical and physiological factors 

Maternal anatomical and physiological changes of pregnancy may contribute to the increased failed tracheal intubation rate and airway-related adverse events. (Table 1) Obesity, increased maternal age and associated co-morbidities may further exacerbate the impact of these changes. A 2-year case-control study of failed obstetric intubation found age, body mass index and Mallampati score were significant independent predictors of failed obstetric tracheal intubation.

 Situational factors

 There is increasing awareness of the contribution of situational and human factors to complications encountered during airway management. Cognitive load may be increased in the obstetric setting by the unique emotional environment and dual demands of managing maternal and fetal wellbeing. The declining frequency of obstetric general anaesthesia (GA) in several parts of the world has led to many anaesthetists having little experience of the technique. Time constraints in the emergency setting may lead to inadequate airway assessment and patient positioning.



Table 1: Pregnancy related maternal anatomical and physiological factors that may contribute to airway difficulties and adverse airway-related events

A:

	Anatomical and physiological changes
Airway	• Increased breast size  • Weight gain in pregnancy  • Increased vascularity and oedema of the airway mucosa
Respiratory	• Reduced functional residual capacity
Gastrointestinal	• Decreased lower oesophageal sphincter tone  • Delayed gastric emptying

B:

	Clinical consequences
Airway	• Difficulty with laryngoscope insertion  • Difficulty with positioning and increased oxygen desaturation • Increased risk of airway bleeding and potential difficulty with tracheal intubation
Respiratory	• Increased oxygen desaturation
Gastrointestinal	• Increased risk of gastric regurgitation and pulmonary aspiration

L Bordoni,1 K Parsons,2 and MWM Rucklidge3* *Correspondence email: Matthew.rucklidge@health.wa.gov.au doi: 10.1029/WFSA-D-18-00019

See also: 

Successful intubation position.