Airway Changes During Labor and Delivery

Tracheal intubation fails much more often in pregnant than in nonpregnant women, but no prospective studies evaluating airway changes during labor have been reported. The investigators carried out 2 studies of airway changes during labor. The first study utilized the conventional Samsoon modification of the Mallampati score, which is based on visualizing the soft palate, faucial pillars, and uvula. The visibility of these structures depends on the relative capacity of the oropharyngeal cavity and the volume of the base of the tongue. In the second study, upper airway volumes were measured by acoustic reflectometry at the onset and end of labor. This method yields values for the components of the upper airway, oral volume, and pharyngeal volume, and includes the concealed part of the upper airway. The first study, conducted in 61 women, demonstrated a significant increase in airway class from pre-labor to the post-labor phase. The airway increased by one grade after labor in one-third of women and by 2 grades in another 5%. Women who initially had class 4 airways were excluded from the study, but 8 women had a class 4 airway and 22 had a class 3 airway at the end of labor. In the second study, performed on 21 women, oral volume and pharyngeal area and volume decreased significantly after labor and delivery. In neither study did airway changes correlate with the duration of labor or with fluid administration. The investigators believe that the airway must be examined immediately before cesarean delivery is carried out rather than depending solely on data from pre-labor assessment.