Rationale: Ansa cervicalis stimulation (ACS) of the infrahyoid muscles has been proposed as a neurostimulation therapy for obstructive sleep apnoea (OSA). ACS stabilises the pharynx by pulling it caudally, but its specific effects on flow limitation caused by palatal, oropharyngeal lateral wall, tongue base, or epiglottis collapse remains unclear.Objectives: To quantify the effect of ACS on collapsibility of different pharyngeal flow-limiting structures.Methods: Participants with OSA underwent bilateral ACS during drug-induced sleep endoscopy. Maximum inspiratory airflow was assessed over a range of positive airway pressures while ACS was applied. The flow-limiting structure for each breath was classified based on manometric and endoscopic findings and a linear mixed-effects model characterised their response to ACS. The influence of patient characteristics was explored with univariate models.Measurements and main results: 41 participants yielded 1761 breaths for analysis. On average, bilateral ACS decreased the observed pharyngeal critical closing (P_CRIT) and opening (P_OPEN) pressures by −3.0 (95% CI −3.6–−2.3) and −3.7 (−4.4–−3.0) cmH₂O, respectively (p<0.001). During tongue base obstruction, modelled ACS effects forP_CRITandP_OPENwere −2.0 (−2.7–−1.4) and −3.1 (−3.8–−2.4) cmH₂O, respectively (p<0.001). Greater reductions were generally observed for other flow-limiting structures. A lower apnoea–hypopnea index was associated with a greater decrease inP_OPEN(p0.05).Conclusions: Bilateral ACS decreased collapsibility of all airway flow-limiting structures. ACS generally had greater effects on palatal, oropharyngeal lateral wall and epiglottic collapse than the tongue base.

Background: The best approaches to supplemental oxygen administration during surgery remain unclear, which may contribute to variation in practice. This study aimed to assess determinants of oxygen administration and its variability during surgery. Methods: Using multivariable linear mixed-effects regression, the study measured the associations between intraoperative fraction of inspired oxygen and patient, procedure, medical center, anesthesiologist, and in-room anesthesia provider factors in surgical cases of 120 min or longer in adult patients who received general anesthesia with tracheal intubation and were admitted to the hospital after surgery between January 2016 and January 2019 at 42 medical centers across the United States participating in the Multicenter Perioperative Outcomes Group data registry. Results: The sample included 367,841 cases (median [25th, 75th] age, 59 [47, 69] yr; 51.1% women; 26.1% treated with nitrous oxide) managed by 3,836 anesthesiologists and 15,381 in-room anesthesia providers. Median (25th, 75th) fraction of inspired oxygen was 0.55 (0.48, 0.61), with 6.9% of cases less than 0.40 and 8.7% greater than 0.90. Numerous patient and procedure factors were statistically associated with increased inspired oxygen, notably advanced American Society of Anesthesiologists classification, heart disease, emergency surgery, and cardiac surgery, but most factors had little clinical significance (less than 1% inspired oxygen change). Overall, patient factors only explained 3.5% (95% CI, 3.5 to 3.5%) of the variability in oxygen administration, and procedure factors 4.4% (95% CI, 4.2 to 4.6%). Anesthesiologist explained 7.7% (95% CI, 7.2 to 8.2%) of the variability in oxygen administration, in-room anesthesia provider 8.1% (95% CI, 7.8 to 8.4%), medical center 23.3% (95% CI, 22.4 to 24.2%), and 53.0% (95% CI, 52.4 to 53.6%) was unexplained. Conclusions: Among adults undergoing surgery with anesthesia and tracheal intubation, supplemental oxygen administration was variable and appeared arbitrary. Most patient and procedure factors had statistical but minor clinical associations with oxygen administration. Medical center and anesthesia provider explained significantly more variability in oxygen administration than patient or procedure factors. Editor’s Perspective: What We Already Know about This Topic: What This Article Tells Us That Is New:

Background: The relationship between postoperative adverse events and blood pressures in the preoperative period remains poorly understood. This study tested the hypothesis that day-of-surgery preoperative blood pressures are associated with postoperative adverse events. Methods: The authors conducted a retrospective, observational study of adult patients having elective procedures requiring an inpatient stay between November 2017 and July 2021 at Vanderbilt University Medical Center to examine the independent associations between preoperative systolic and diastolic blood pressures (SBP, DBP) recorded immediately before anesthesia care and number of postoperative adverse events—myocardial injury, stroke, acute kidney injury, and mortality—while adjusting for potential confounders. The study used multivariable ordinal logistic regression to model the relationship. Results: The analysis included 57,389 cases. The overall incidence of myocardial injury, stroke, acute kidney injury, and mortality within 30 days of surgery was 3.4% (1,967 events), 0.4% (223), 10.2% (5,871), and 2.1% (1,223), respectively. The independent associations between both SBP and DBP measurements and number of postoperative adverse events were found to be U-shaped, with greater risk both above and less than SBP 143 mmHg and DBP 86 mmHg—the troughs of the curves. The associations were strongest at SBP 173 mmHg (adjusted odds ratio, 1.212 vs. 143 mmHg; 95% CI, 1.021 to 1.439; P = 0.028), SBP 93 mmHg (adjusted odds ratio, 1.339 vs. 143 mmHg; 95% CI, 1.211 to 1.479; P < 0.001), DBP 106 mmHg (adjusted odds ratio, 1.294 vs. 86 mmHg; 95% CI, 1.003 to 1.17671; P = 0.048), and DBP 46 mmHg (adjusted odds ratio, 1.399 vs. 86 mmHg; 95% CI, 1.244 to 1.558; P < 0.001). Conclusions: Preoperative blood pressures both less than and above a specific threshold were independently associated with a higher number of postoperative adverse events, but the data do not support specific strategies for managing patients with low or high blood pressure on the day of surgery. Editor’s Perspective: What We Already Know about This Topic: What This Article Tells Us That Is New: