Ascending and Descending Pharyngeal Opening Pressures During Drug-Induced Sleep Endoscopy: Mechanistic Insights for Sleep Surgeons.

Abstract

To assess whether differences exist between ascending pharyngeal opening pressure (PhOP_A) and descending pharyngeal opening pressure (PhOP_D) obtained from positive airway pressure (PAP) titrations during drug-induced sleep endoscopy (DISE) and to identify the associations between the physiologic and anatomic constituents of these differences. Cross-sectional study of a prospective, single-site sleep surgery cohort. Quaternary care center. Consecutive patients with obstructive sleep apnea undergoing DISE with PAP were enrolled. PAP was raised in a stepwise manner until inspiratory airflow limitation was abolished (PhOP_A), then decreased until just before airflow limitation reappeared (PhOP_D). Negative effort dependence (NED) was calculated in flow-limited breaths as the percentage difference in nasal airflow from peak to plateau. Anatomic measures included both computed tomography (CT) and VOTE scores. PhOP_A and PhOP_D were compared using paired t tests. Associations with the percent difference in PhOP values (PhOP_A-D) were evaluated using Pearson's correlations or analysis of variance for continuous or categorical measures, respectively. In a cohort of 43 patients, PhOP_A was greater than PhOP_D (7.41 ± 2.55 vs 6.02 ± 1.77 cm H₂O, P < .01). For patients with nonequivalent PhOP_A-D, the mean PhOP_A-D was 1.88 ± 1.33 cm H₂O, or a percent difference of 21.95% ± 10.37%. In both unadjusted and adjusted analyses, higher PhOP_A-D was associated with higher NED (r = 0.46, P = .003) and with more negative pharyngeal pressure (r = -0.48, P = .002). Patients with a nonequivalent PhOP_A-D were more likely to have complete lateral wall obstruction on VOTE (P = .03). The present study showed no statistically significant associations with CT findings. The correlation of PhOP_A-D with negative pharyngeal pressure supports the ability of DISE to partition passive versus active contributions to upper airway obstruction. Higher PhOP_A-D highlights the possible extrapharyngeal drivers of upper airway obstruction, particularly ventilatory drive and respiratory effort. DISE-PAP with ascending and descending titrations can potentially be used in conjunction with anatomic findings on CT and VOTE scoring to offer insights into patient selection for sleep surgery. Level 2.