Critical closing pressure of the pharyngeal airway during routine drug-induced sleep endoscopy: feasibility and protocol

Abstract

In obstructive sleep apnea (OSA), there are various pathophysiological factors affecting the upper airway during sleep. Two prominent factors contributing to OSA are site and pattern of upper airway collapse and degree of pharyngeal collapsibility. In a clinical setting, drug-induced sleep endoscopy (DISE) is used to visualize the structures of the upper airway. Critical closing pressure (Pcrit) is the gold standard measure of pharyngeal collapsibility. This prospective clinical study aimed to investigate the feasibility and protocol of Pcrit measurements during DISE. Thirteen patients with OSA were included. Pcrit was calculated using peak inspiratory airflow and inspiratory ventilation. The proposed protocol was successful in Pcrit measurement during DISE in all subjects [median[Q1;Q3] Pcrit for "peak inspiratory method" (n = 12): -0.84[-2.07;0.69] cmH2O, "ventilation method" (n = 13): -1.32[2.32;0.47] cmH2O], highlighting the feasibility of the approach. There was no significant difference (P = 0.67) between calculated Pcrit with either of the calculation methods, indicating high reliability. Correlation analysis showed Pcrit as an independent parameter of any of the anthropometric or polysomnographic parameters. The ventilation method proved to be more successful in assessment of Pcrit in subjects with epiglottic collapse (e.g., with high negative effort dependence). Subjects with palatal complete concentric collapse during DISE had a wide Pcrit range ([-2.86;2.51]cmH2O), suggesting no close correlation between Pcrit and this DISE pattern (P = 0.38). Incorporation of Pcrit measurements into DISE assessments is feasible and may yield valuable additional information for OSA management. Combining Pcrit and DISE provides information on both the site and degree of upper airway collapse and the degree of pharyngeal collapsibility.NEW & NOTEWORTHY The protocol of this study was successful in concomitant measurement of Pcrit during routine clinical endoscopy. Comparison of two calculation methods for Pcrit showed that the inspiratory ventilation method was more successful in assessment of Pcrit in subjects with epiglottic collapse who have high negative effort dependence. Subjects with palatal complete concentric collapse during DISE had a wide Pcrit range and did not have a greater Pcrit than patients in other site of collapse categories.

Trial registration: ClinicalTrials.gov NCT04232410.

Keywords: DISE; collapsibility; endotyping; obstructive sleep apnea; upper airway.

Conflict of interest statement

J.V. reports grants from SomnoMed, AirLiquide, Vivisol, Mediq Tefa, Medidis, OSG, Bioprojet, Desitin, Philips, and ResMed outside the submitted work. S.A.S. reports consulting fees from Apnimed, Nox Medical, Merck, and Eli Lilly unrelated to the current work, plus unrelated grant support from Apnimed, Prosomnus, and Dynaflex; his outside activities are actively monitored by his institution. O.M.V. reports grants from Philips and Somnomed at Antwerp University Hospital and others from Inspire Medical Systems, Nightbalance, GSK, and Liva Nova at Antwerp University Hospital outside the submitted work. No conflicts of interest, financial or otherwise, are declared by the other authors.

Figures

Graphical abstract

Figure 1.

Schematic model of the pressure-flow relationship. Pin, inflow pressure; Pout, Outflow pressure; Psur, surrounding pressure.

Figure 2.

Schematic overview of set-up for measurement of critical closing pressure (Pcrit) of the pharyngeal airway during drug-induced sleep endoscopy (DISE).

Figure 3.

Sample representatives of flow with a pressure drop for five breaths. A: start and endpoints of each 5-breath pressure drop (run) were determined by expert visual analysis. B: sample of an apneic event as a result of a pressure drop. C: breaths 3 to 5 of the pressure drop were used in the analysis. D: maximum inspiratory airflow (arrows) was used in the calculations with peak inspiratory method. E: inspiratory ventilation for flow-limited breaths 3 to 5 was used in calculations with the ventilation method. F: sample breaths with airflow pattern pointing to the presence of high negative effort dependence (NED), reflected by the high peak at the start of inspiration (arrows) followed by a low plateau inspiration. Mask pressure (Pmask), pressure recorded via balloon esophageal catheter (Pesophageal).

Figure 4.

Sample representatives of pressure-flow linear regression of subject 10 for both calculation methods. A: peak inspiratory method sample: Pcrit was determined as the zero-flow intercept from the linear regression of flow vs. pressure of the isolated segment between Peff and near Pcrit points (Pcrit = 2.36 cmH2O). B: V̇e, minute ventilation converted to l/s, ventilation method sample (Pcrit = 3.01 cmH2O). Pcrit, critical closing pressure; Peff, upper inflection point.

Figure 5.

Flow chart of subjects for critical closing pressure (Pcrit) measurement and calculation.

Figure 6.

Critical closing pressure (Pcrit) as calculated with both methods [using peak inspiratory (PcritPeak) and inspiratory ventilation (PcritVent)]. Note that patient 7 gave unrealistic results using the peak inspiratory method and was therefore excluded for further analysis with this method. A color is assigned to each subject.

Figure 7.

Bland–Altman plot for comparison of PcritPeak and PcritVent methods showing within-pair means on x-axis and between-pair differences on y-axis (bias = −0.10, upper limit of agreement = 1.48, lower limit of agreement = −1.68, confidence interval = 95%). PcritPeak, critical closing pressure using peak inspiratory; PcritVent, critical closing pressure using inspiratory ventilation.

Figure 8.

Representatives of pressure-flow linear regression of subject 7 for all three calculation methods. A: peak inspiratory method (Pcrit = −7.36 cmH2O). B: V̇e, minute ventilation converted to l/s, ventilation method (Pcrit = −2.72 cmH2O). C: mid inspiratory method (Pcrit = −0.59 cmH2O)

Figure 9.

Drug-induced sleep endoscopy (DISE) findings and critical closing pressure (Pcrit) values. A: palatal complete concentric collapse (CCCp), palatal complete anteroposterior collapse (CAPp), collapse at the level of oropharynx, tongue base, hypopharynx, and epiglottis. B: CCCp in combination with collapse at the level of oropharynx or tongue base. A color is assigned to each subject.