Feasibility of upper airway collapsibility measurements in anesthetized children.

Patients with a propensity for upper airway obstruction, including those with obstructive sleep apnea (OSA), are vulnerable in the perioperative period. OSA is an increasingly common disorder in children and, when present, is associated with an increased risk of perioperative respiratory adverse events (PRAE),1 morbidity, and mortality. Therefore, identifying at-risk patients is vital to provide tailored perioperative anesthetic management. Quantifying the collapsibility of the upper airway provides useful physiologic information on pharyngeal mechanics, which may help identify patients vulnerable to obstructive airway episodes and consequent PRAE. Several methods have been described to assess upper airway collapsibility, including pharyngeal critical closing pressure (Pcrit).2 However, assessing Pcrit in children is not clinically feasible as it is time-consuming and requires post hoc analysis. Pharyngeal closing pressure (PCLOSE) is another, simpler objective method of assessing upper airway collapsibility. The PCLOSE measurement method and its potential clinical utility in adults have been described.3 However, the feasibility of obtaining perioperative measurement of PCLOSE in children under anesthesia is unknown. Therefore, this study aimed to investigate whether PCLOSE measurement is practical in a clinical environment. Institutional ethics approvals (CAHS 2015140EP; UWA RA/4/1/7856) and trial registration (ACTRN 12615001037594) were obtained before study commencement. Written informed consent was obtained from parents/guardians and children as appropriate. Fifty-six children (34 males) aged 1–8 years (mean ± SD: 5.49 ± 2.00) with no significant co-morbidities undergoing adenotonsillectomy were included. PCLOSE measurements were performed at two separate perioperative phases: following anesthesia induction (Pre-procedure PCLOSE) and emergence from anesthesia (Post-procedure PCLOSE). Standard anesthesia management according to the institutional guidelines was performed. Children received either inhalational induction of anesthesia with sevoflurane or intravenous induction with propofol. Spontaneous breathing was maintained with sevoflurane. No muscle relaxants were used. No opioid was given before the pre-procedure PCLOSE measurements. Airway management devices were mainly laryngeal masks (endotracheal tubes in three patients). The PCLOSE measurement procedure required the use of an anesthetic face mask in series with an airway filter, measurement of mask pressure (pressure transducer (Micro Switch; Honeywell)), a flow sensor (model 0580D, Braebon), and a balloon valve (model 9309 Hans Rudolf; Shanwee) (Figure 1A). Mask pressure and airflow were recorded on a PowerLab data acquisition device (model 16 s; ADInstruments). Pressure-flow relationships were analyzed using LabChart software (version 6.1.1, ADInstruments). The presence of a leak was monitored either graphically from the pressure–time profile (pressure signals trending towards zero) or clinically during the study. All measurements were made in standard posture: supine with the head in a neutral posture without jaw thrust. After ensuring a leak-free facemask, a minimum of five breaths were recorded to confirm stable respiration during spontaneous breathing. The mask was then occluded (via inflation of the balloon valve) at end-expiration. The inspiratory pressure–time profile was monitored for evidence of “plateauing” over 5–6 sequential inspiratory efforts. Once flattening was observed, the balloon valve was deflated, and breathing returned to an unobstructed state (Figure 1B,C). Measurements were repeated a minimum of three times for each pre-and post-procedure PCLOSE. Plateauing of inspiratory pressure (at a level termed PCLOSE) indicated upper airway collapse: a less collapsible airway occluded at more negative pressure. When multiple inspiratory efforts occurred within 10% of each other during a single occlusion period, an average of the pressures was used. If values were outside the 10% range, inspiratory efforts indicative of collapse closest to the onset of occlusion were preferentially selected for analysis. When inspiratory pressure became progressively more negative with sequential efforts, but the mask pressure shape did not indicate collapse, the airway was deemed resistant to collapse. In such cases, the most negative pressure developed was recorded for the subsequent statistical analysis of case-by-case collapsibility. Pre-procedure PCLOSE measurements were successfully obtained in 54 (96.4%) participants, while both pre- and post-PCLOSE measurements were obtained in 51 (91%) participants. A complete set of measurements could not be obtained from three participants; these occurred in the early phase of the study and were due to technical issues, which were subsequently resolved. Post-procedure PCLOSE (mean ± SD) −7.09 ± 5.48 cmH2O was slightly more negative than pre-PCLOSE (mean ± SD) −5.12 ± 4.53 cmH2O (p = .04) indicating an overall improvement in collapsibility post-procedure. This study was conducted in a convenience sample to examine the practicality of PCLOSE measurements. We successfully measured pre- and post-procedure PCLOSE without affecting the routine clinical care or surgery time. Each measurement took 3–5 min. No PRAE were observed during the PCLOSE measurement procedure. Our experience showed that the measurement technique was uncomplicated and could be performed by trained medical staff. This study demonstrated that obtaining PCLOSE measurements is feasible in anesthetized children. In addition, PCLOSE measurement provides a real-time measure of upper airway collapsibility and could be included in future standard anesthetic monitoring. Open access publishing facilitated by The University of Western Australia, as part of the Wiley - The University of Western Australia agreement via the Council of Australian University Librarians. The data supporting this study's findings are available from the corresponding author upon reasonable request.