The effect of oral positioning on the hypopharyngeal airway

Objectives: It is generally assumed that mouth opening decreases the hypopharyngeal cross-sectional area (HA) and that tongue protrusion (TP) increases the HA. We hypothesize that a substantial number of patients do not exhibit this expected pattern. Study Design: Prospective cohort conducted at a tertiary academic center. Methods: With a flexible fiberoptic scope in position, the hypopharyngeal airway was visualized and assessed in 189 patients with the mouth closed. Patients were then asked to open the mouth with the tongue in neutral position (MOTN) to determine the effect on the airway. The same methodology was used to compare the airway with the MOTN versus TP. Basic demographics, including age, gender, body mass index, and presence and severity of obstructive sleep apnea (OSA), were collected. Student t test, Mantel-Haenszel chi-square, and Cochran-Armitage analyses were assessed for significant relationships and trends with oral positions. Results: Although mean HA decreased with MOTN (P < 0.0001), 33% of patients exhibited an increase in HA. Similarly, mean HA increased with TP (P = 0.0018); however, 38% of patients demonstrated a decrease in HA. There was no significant relationship in HA between OSA and non-OSA patients. For those with OSA, increasing severity trended toward a higher incidence of smaller HA with TP (P = 0.038). Conclusion: The airway is typically most obstructed with mouth opening (MOTN) and most patent with tongue protrusion (TP). Nevertheless, hypopharyngeal changes with MOTN and TP followed a paradoxical pattern in one-third of our population. This may have implications in patient selection for targeted OSA treatment. Level of Evidence: 4. Laryngoscope, 127:1471–1475, 2017.