The airway becomes more difficult to manage, for numerous reasons.
Bag-mask ventilation becomes more difficult:
- The nasal mucosa is engorged, which means there is greater resistance to flow
- The upper airway mucosa is oedematous
- There has been weight gain
Laryngoscopy becomes more difficult:
- Upper airway oedema
- Breast enlargement
- The Mallampatti grade changes during pregnancy, largely because of oedema of the pharynx, and due to weight gain. It gets even worse with labour.
Less time is available for intubation:
- Decreased FRC, less time to intubate
- Increased oxygen consumption, less time to intubate
Intubation is more risky
- Increased risk of aspiration, decreased stomach emptying
References
Chapter 64 (pp. 684) General obstetric emergencies by Winnie TP Wan and Tony Gin
Chapter 65 (pp. 692) Severe pre-existing disease in pregnancy by Jeremy P Campbell and Steve M Yentis
Munnur, Uma, Ben de Boisblanc, and Maya S. Suresh. "Airway problems in pregnancy." Critical care medicine 33.10 (2005): S259-S268.
Jeejeebhoy, Farida M., et al. "Management of cardiac arrest in pregnancy: a systematic review." Resuscitation 82.7 (2011): 801-809.
Kodali, Bhavani-Shankar, et al. "Airway changes during labor and delivery."Anesthesiology 108.3 (2008): 357-362.