Effect of mandibular position on upper airway collapsibility and resistance

Analysis of Sedation Accident Records Available in the Japan Council for Quality Health Care Public Database

OBJECTIVE

Medical accidents occur frequently. However, only a few studies have been conducted on sedation-related medical accidents. This study aimed to classify sedation accidents and analyze their causes using the (Patient-management Software Hardware Environment Livewear (P-mSHELL) model.

METHODS

The Japan Council for Quality Health Care database on medical accidents was used. Sedation accidents that occurred during procedures between January 2010 and June 2022 were included. After examining the accident details for several variables, the accident factors were classified by factors in the P-mSHELL model, and statistical analyses, including multivariate analysis of each factor and outcome (presence or absence of residual disability), were conducted.

RESULTS

Regarding the influence of the P-mSHELL factors on outcome, P factor (odds ratio = 6.347, 95% confidence interval = 2.000, 20.144) was a factor for having disability. There was a significant association between outcome and accident timing (that is, preoperative, intraoperative, or postoperative; p =0.01). No significant association was found between the outcomes and types of drugs used (p =1, 0.722, 0.594); however, there was a significant association between the incidence of respiratory depression and multiple drug use (p <0.001).

CONCLUSIONS

To prevent sedation accidents, it is important to monitor patients throughout the perioperative period. However, it is especially important to know the patient's condition in advance, and strict postoperative management is essential, especially for high-risk patients, to prevent serious accidents.

Mandibular advancement reduces pharyngeal collapsibility by enlarging the airway rather than affecting velopharyngeal compliance

Mandibular advancement devices (MADs) are frequently prescribed for obstructive sleep apnea (OSA) patients, but approximately one third of patients experience no therapeutic benefit. Understanding the mechanisms by which MADs prevent pharyngeal collapse may help optimize MAD therapy. This study quantified the relative contributions of changes in airspace cross-sectional area (CSA) versus changes in velopharyngeal compliance in determining MAD efficacy. Sixteen patients with moderate to severe OSA (mean apnea-hypopnea index of 32 ± 15 events/h) underwent measurements of the velopharyngeal closing pressure (PCLOSE ) during drug induced sedated endoscopy (DISE) via stepwise reductions in nasal mask pressure and recording of the intraluminal pressure with a catheter. Airspace CSA was estimated from video endoscopy. Pharyngeal compliance was defined as the slope of the area-pressure relationship of the velopharyngeal airspace. MAD therapy reduced PCLOSE from a median of 0.5 cmH2 O pre-advancement to a median of -2.6 cmH2 O post-advancement (p = 0.0009), increased the minimal CSA at the velopharynx by approximately 20 mm2 (p = 0.0067), but did not have a statistically significant effect on velopharyngeal compliance (p = 0.23). PCLOSE had a strong correlation with CSA but did not correlate with velopharyngeal compliance. Our results suggest that MADs reduce velopharyngeal collapsibility by increasing airway size as opposed to affecting velopharyngeal compliance. This contradicts the speculation of previous literature that the effectiveness of MADs is partially due to a reduction in velopharyngeal compliance resulting from stretching of the soft palate. These findings suggest that quantification of velopharyngeal CSA pre- and post-MAD advancement has potential as a biomarker to predict the success of MAD therapy.

Usefulness of new acoustic respiratory sound monitoring with artificial intelligence for upper airway assessment in obese patients during monitored anesthesia care

Monitored anesthesia care (MAC) often causes airway complications, particularly posing an elevated risk of aspiration and airway obstruction in obese patients. This study aimed to quantify the levels of aspiration and airway obstruction using an artificial intelligence (AI)-based acoustic analysis algorithm, assessing its utility in identifying airway complications in obese patients. To verify the correlation between the stridor quantitative value (STQV) calculated by acoustic analysis and body weight, and to further evaluate fluid retention and airway obstruction, STQV calculated exhaled breath sounds collected at the neck region, was compared before and after injection of 3 ml of water in the oral cavity and at the start and end of the MAC procedures. STQV measured immediately following the initiation of MAC exhibited a weak correlation with body mass index. Furhtermore, STQV values before and after water injection increased predominantly after injection, further increased at the end of MAC. AI-based analysis of cervical respiratory sounds can enhance the safety of airway management during MAC by quantifying airway obstruction and fluid retention in obese patients. J. Med. Invest. 70 : 430-435, August, 2023.

The clinical advantage of nasal high-flow in respiratory management during procedural sedation: A scoping review on the application of nasal high-flow during dental procedures with sedation

Structured summary

Rationale: Nasal high-flow (NHF), a new method for respiratory management during procedural sedation, has greater advantages than conventional nasal therapy with oxygen. However, its clinical relevance for patients undergoing oral maxillofacial surgery and/or dental treatment remains uncertain and controversial, due to a paucity of studies. This scoping review compared and evaluated NHF and conventional nasal therapy with oxygen in patients undergoing oral maxillofacial surgery and/or dental treatment.

Materials and methods

A literature search of two public electronic databases was conducted, and English writing randomized controlled trials (RCTs) of nasal high flow during dental procedure with sedation reviewed. The primary and secondary outcomes of interest were the incidence of hypoxemia and hypercapnia during sedation and the need for intervention to relieve upper airway obstruction, respectively.

Results

The search strategy yielded 7 studies, of which three RCTs met our eligibility criteria, with a total of 78 patients. Compared with conventional nasal therapy with oxygen, NHF significantly reduced the incidence of hypoxemia and hypercapnia during procedural sedation.

Conclusion

NHF can maintain oxygenation and possibly prevent hypercapnia in patients undergoing dental treatment. Additional RCTs are needed to clarify and confirm these findings.

Critical to Know Pcrit: A Review on Pharyngeal Critical Closing Pressure in Obstructive Sleep Apnea

It is crucial to understand the underlying pathophysiology of obstructive sleep apnea (OSA). Upper airway collapsibility is an important pathophysiological factor that affects the upper airway in OSA. The aim of the current study was to review the existing body of knowledge on the pharyngeal collapsibility in OSA. After a thorough search through Medline, PubMed, Scopus, and Web of science, the relevant articles were found and used in this study. Critical closing pressure (Pcrit) is the gold standard measure for the degree of collapsibility of the pharyngeal airway. Various physiological factors and treatments affect upper airway collapsibility. Recently, it has been shown that the baseline value of Pcrit is helpful in the upfront selection of therapy options. The standard techniques to measure Pcrit are labor-intensive and time-consuming. Therefore, despite the importance of Pcrit, it is not routinely measured in clinical practice. New emerging surrogates, such as finite element (FE) modeling or the use of peak inspiratory flow measurements during a routine overnight polysomnography, may enable clinicians to have an estimate of the pharyngeal collapsibility. However, validation of these techniques is needed.

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

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.

Tridimensional upper airway assessment in male patients with OSA using oral advancement devices modifying their vertical dimension

STUDY OBJECTIVES

Mandibular advancement devices (MADs) constitute an alternative treatment in selected patients with OSA. A mandibular advanced position has been suggested to be beneficial, whereas its combination with an increased bite-raise may increase its adverse effects. The objective of this study was to assess upper airway (UA) volume and inspiratory pressure gradient variations in a group of 17 patients with OSA. The study was performed under 3 mandibular positions: intercuspal position (P1), MAD position in closed mouth (P2), and MAD position with an increased bite-raise (P3).

METHODS

We conducted a 3-dimensional reconstruction of the pharynx using the finite element method via a computed tomography scan and the subsequent calculation using fluid-dynamic analysis.

RESULTS

One hundred percent of the patients showed an increase in UA volume in both P2 and the MAD position with an increased bite-raise, P2 being the position where 76.47% of the patients showed the largest UA volume. P2/velopharynx was the position/region where the largest UA volume increase was achieved (4.73 mm³). A better gradient in P2 (mean = 0.62) in 58.82% of the patients and a better gradient in P3 (mean = 0.74) in 41.18% of patients respect P1 was observed. In 82.35% of patients, a better volume-pressure gradient match was also found.

CONCLUSIONS

The best efficiency scores for both volume increase and better inspiratory pressure gradient were obtained in P2. This study findings suggest that in a MAD, the minimal bite opening position necessary for mandibular protrusion is more effective in increasing airway volume and inspiratory gradient compared to a larger bite-raising (15 mm).

Upper-airway collapsibility and compensatory responses under moderate sedation with ketamine, dexmedetomidine, and propofol in healthy volunteers

BACKGROUND

Ketamine is a potent sedative drug that helps to maintain upper-airway patency, due to its higher upper-airway dilator muscular activity and higher level of duty cycle, as seen in rats. However, no clinical trials have tested passive upper-airway collapsibility and changes in the inspiratory duty cycle against partial upper-airway obstruction in humans. The present study evaluated both the passive mechanical upper-airway collapsibility and compensatory response against acute partial upper-airway obstruction using three different sedative drugs in a crossover trial.

METHODS

Eight male volunteers entered this nonblinded, randomized crossover study. Upper-airway collapsibility (passive critical closing pressure) and inspiratory duty cycle were measured under moderate sedation with ketamine, propofol, and dexmedetomidine. Propofol, dexmedetomidine, and ketamine anesthesia were induced to obtain adequate, same-level sedation, with a BIS value of 50-70 and the OAA/S score of 2-3 and RASS score of -3.

RESULTS

The median passive critical closing pressure of 0.08 [-5.51 to 1.20] cm H2 O was not significantly different compared to that of propofol sedation (-0.32 [-1.41 to -0.19] cm H2 O) and of dexmedetomidine sedation (-0.28 [-0.95 to -0.03] cm H2 O) (p = .045). The median passive RUS for ketamine 54.35 [32.00 to 117.50] cm H2 O/L/s was significantly higher than that for propofol 5.50 [2.475 to 19.60] cm H2 O/L/s; (mean difference, 27.50; 95% CI 9.17 to 45.83) (p = .009) and for dexmedetomidine 19.25 [4.125 to 22.05] cm H2 O/L/s; (mean difference, 22.88; 95% CI 4.67 to 41.09) (p = .021). The inspiratory duty cycle increased significantly as the inspiratory airflow decreased in passive conditions for each sedative drug, but behavior differed among the three sedative drugs.

CONCLUSION

Our findings demonstrate that ketamine sedation may have an advantage of both maintained passive upper-airway collapsibility and a compensatory respiratory response, due to both increase in neuromuscular activity and the increased duty cycle, to acute partial upper-airway obstruction.

Upper airway collapsibility measured using a simple wakefulness test closely relates to the pharyngeal critical closing pressure during sleep in obstructive sleep apnea

STUDY OBJECTIVES

A collapsible or crowded pharyngeal airway is the main cause of obstructive sleep apnea (OSA). However, quantification of airway collapsibility during sleep (Pcrit) is not clinically feasible. The primary aim of this study was to compare upper airway collapsibility using a simple wakefulness test with Pcrit during sleep.

METHODS

Participants with OSA were instrumented with a nasal mask, pneumotachograph and two pressure sensors, one at the choanae (PCHO), the other just above the epiglottis (PEPI). Approximately 60 brief (250 ms) pulses of negative airway pressure (~ -12 cmH2O at the mask) were delivered in early inspiration during wakefulness to measure the upper airway collapsibility index (UACI). Transient reductions in the continuous positive airway pressure (CPAP) holding pressure were then performed during sleep to determine Pcrit. In a subset of participants, the optimal number of replicate trials required to calculate the UACI was assessed.

RESULTS

The UACI (39 ± 24 mean ± SD; range = 0%-87%) and Pcrit (-0.11 ± 2.5; range: -4 to +5 cmH2O) were quantified in 34 middle-aged people (9 female) with varying OSA severity (apnea-hypopnea index range = 5-92 events/h). The UACI at a mask pressure of approximately -12 cmH2O positively correlated with Pcrit (r = 0.8; p < 0.001) and could be quantified reliably with as few as 10 replicate trials. The UACI performed well at discriminating individuals with subatmospheric Pcrit values [receiver operating characteristic curve analysis area under the curve = 0.9 (0.8-1), p < 0.001].

CONCLUSIONS

These findings indicate that a simple wakefulness test may be useful to estimate the extent of upper airway anatomical impairment during sleep in people with OSA to direct targeted non-CPAP therapies for OSA.

Correlation Between Body Movements and Salivary Secretion During Sedation

During dental sedation, control of the cough reflex is crucial for a safe and smooth procedure. Accumulated saliva is one of the predisposing factors for coughing. Body movements during dental sedation appear to enhance salivation. Therefore, the aim of this study was to investigate the difference in salivary secretion between the with-movements state and the without-movements state during sedation. Salivary weight for 1 min was measured 3 times in 27 patients with intellectual disability during dental treatment under deep sedation with midazolam and propofol. The observed variables were body movements, bispectral index (BIS), and predicted propofol effect-site concentration. A total of 81 measurements were classified into the with-movements state (n = 39; ie, measurements during which body movements were observed) or the without-movements state (n = 42; ie, measurements during which no body movements were observed). The median salivary weight was significantly smaller in the without-movements state compared with the with-movements state (0.03 vs 0.11 g, P < .0001). The BIS was significantly lower in the without-movements state. There was no significant difference in the predicted propofol effect-site concentration between the 2 states. Significant correlation was observed between salivary weight and BIS in the with-movements state (r = 0.44, P = .004). The findings indicate that salivary secretion decreased according to deep sedation. Furthermore, immobility also reduced salivary secretion. We concluded that one reason that immobility is beneficial is because of the resulting decreased salivary secretion during dental treatment under deep sedation.

Treatment of Obstructive Sleep Apnea. Prospects for Personalized Combined Modality Therapy

Obstructive sleep apnea (OSA) is a common sleep disorder with serious associated morbidities. Although several treatment options are currently available, variable efficacy and adherence result in many patients either not being treated or receiving inadequate treatment long term. Personalized treatment based on relevant patient characteristics may improve adherence to treatment and long-term clinical outcomes. Four key traits of upper airway anatomy and neuromuscular control interact to varying degrees within individuals to cause OSA. These are: (1) the pharyngeal critical closing pressure, (2) the stability of ventilator chemoreflex feedback control (loop gain), (3) the negative intraesophageal pressure that triggers arousal (arousal threshold), and (4) the level of stimulus required to activated upper airway dilator muscles (upper airway recruitment threshold). Simplified diagnostic methods are being developed to assess these pathophysiological traits, potentially allowing prediction of which treatment would best suit each patient. In contrast to current practice of using various treatment modes alone, model predictions and pilot clinical trials show improved outcomes by combining several treatments targeted to each patient's pathophysiology profile. These developments could theoretically improve efficacy and adherence to treatment and in turn reduce the social and economic health burden of OSA and the associated life-threatening morbidities. This article reviews OSA pathophysiology and identifies currently available and investigational treatments that may be combined in the future to optimize therapy based on individual profiles of key patient pathophysiological traits.

Maxillomandibular Volume Influences the Relationship between Weight Loss and Improvement in Obstructive Sleep Apnea

STUDY OBJECTIVES

Obesity is the major risk factor for OSA; however, weight loss reduces OSA to a variable extent. We aimed to assess whether size of the maxillomandibular skeletal enclosure influences the relationship between weight loss and OSA reduction.

METHODS

Obese males (≥ 30 kg/m2) with moderate-severe OSA (AHI > 15/h) participating in a 6-mo open-label weight loss program had craniofacial computed tomography (CT) scans before and after weight loss. CT scans were analysed using three-dimensional cephalometry. Maxillomandibular volume was calculated from skeletal landmarks on the mandible (condyle, gonion, menton) and maxilla (anterior nasal spine). Multiple regression analysis was used to test for moderating effects of maxillomandibular volume on relationship between changes in weight and apnea-hypopnea index (AHI).

RESULTS

Fifty-two men (age 44.3 ± 8.8 y, AHI 42.9 ± 21.3 events/h, body mass index [BMI] 34.0 ± 2.7 kg/m2) had 7.4 ± 4.1% weight loss and 34.1 ± 32.4% AHI reduction at 6 months. BMI reduction modestly predicted AHI change (r2 = 0.17, P = 0.002). The interaction term of maxillomandibular volume and BMI change was a predictor of OSA improvement (P = 0.03), indicating maxillomandibular volume moderates this relationship. Subgroup analyses of patients by small, medium, and large maxillomandibular volume showed a strong correlation between weight loss and OSA improvement only in the small volume group (r = 0.654, P = 0.004). There was no relationship evident in those with large maxillomandibular volume (r = 0.05, P = 0.9).

CONCLUSION

Maxillomandibular volume influences the relationship between weight loss and OSA improvement with an effect on AHI more evident in those with a smaller craniofacial skeleton.

Peripharyngeal tissue deformation, stress distributions, and hyoid bone movement in response to mandibular advancement

Mandibular advancement (MA) increases upper airway (UA) patency and decreases collapsibility. Furthermore, MA displaces the hyoid bone in a cranial-anterior direction, which may contribute to MA-associated UA improvements via redistribution of peripharyngeal tissue stresses (extraluminal tissue pressure, ETP). In the present study, we examined effects of MA on ETP distributions, deformation of the peripharyngeal tissue surface (UA geometry), and hyoid bone position. We studied 13 supine, anesthetized, tracheostomized, spontaneously breathing adult male New Zealand White rabbits. Graded MA was applied from 0 to ∼4.5 mm. ETP was measured at six locations distributed throughout three UA regions: tongue, hyoid, and epiglottis. Axial computed tomography images of the UA (nasal choanae to glottis) were acquired and used to measure lumen geometry (UA length; regional cross-sectional area) and hyoid displacement. MA resulted in nonuniform decreases in ETP (greatest at tongue region), ranging from −0.11 (−0.15 to −0.06) to −0.82 (−1.09 to −0.54) cmH2O/mm MA [linear mixed-effects model slope (95% confidence interval)], across all sites. UA length decreased by −0.5 (−0.8 to −0.2) %/mm accompanied by nonuniform increases in cross-sectional area (greatest at hyoid region) ranging from 7.5 (3.6–11.4) to 18.7 (14.9–22.5) %/mm. The hyoid bone was displaced in a cranial-anterior direction by 0.42 (0.36–0.44) mm/mm MA. In summary, MA results in nonuniform changes in peripharyngeal tissue pressure distributions and lumen geometry. Displacement of the hyoid bone with MA may play a pivotal role in redistributing applied MA loads, thus modifying tissue stress/deformation distributions and determining resultant UA geometry outcomes.

A Remote-Controlled Airbag Device Can Improve Upper Airway Collapsibility by Producing Head Elevation With Jaw Closure in Normal Subjects Under Propofol Anesthesia

Continuous maintenance of an appropriate position of the mandible and head purely by manual manipulation is difficult, although the maneuver can restore airway patency during sleep and anesthesia. The aim of this paper was to examine the effect of head elevation with jaw closure using a remote-controlled airbag device, such as the airbag system, on passive upper airway collapsibility during propofol anesthesia. Seven male subjects were studied. Propofol infusion was used for anesthesia induction and maintenance, with a target blood propofol concentration of 1.5–2 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\(\mu \) \end{document}g/ml. Nasal mask pressure (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\({P}_{\text {N}}\) \end{document}) was intermittently reduced to evaluate upper airway collapsibility (passive \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\({P}_{_{\text {CRIT}}}\) \end{document}) and upstream resistance (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\({R}_{_{\text {US}}}\) \end{document}) at three different head and jaw positions, jaw opening position in the supine position, jaw opening position in the sniffing position with 6-cm head elevation, and jaw closure at a 6-cm height sniffing position. The 6-cm height sniffing position with jaw closure was achieved by an airbag device that was attached to the subject’s head-like headgear. Patient demographics, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\({P}_{_{\text {CRIT}}}\) \end{document} and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\({R}_{_{\text {US}}}\) \end{document} in each condition were compared using one-way ANOVA with a post hoc Tukey test. \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\({\rm P}<0.05\) \end{document} was considered significant. We also confirmed the effects of our airbag device on improvement of upper airway collapsibility in three obstructive sleep apnea patients in a clinical study. The combination of 6-cm head elevation with jaw closure using the air-inflatable robotic airbag system decreased upper airway collapsibility (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\({P}_{_{\text {CRIT}}}\sim -3.4\) \end{document}-cm H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\(_{2}\) \end{document}O) compared with the baseline position (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\({P}_{_{\text {CRIT}}}\sim -0.8\) \end{document}-cm H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\(_{2}\) \end{document}O, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\({P} = 0.0001\) \end{document}). In the clinical study, there was improvement of upper airway obstruction in sleep apnea patients, including decreased apnea and hypopnea duration and increased the lowest level of oxygen saturation. We demonstrated that establishment of head elevation with jaw closure achieved by a remote-controlled airbag device using an inflatable airbag system can produce substantial decreases in upper airway collapsibility and maintain upper airway patency during propofol anesthesia and sleep.

Drug-induced sleep endoscopy: a two drug comparison and simultaneous polysomnography

The purpose of the present study was to compare pharyngeal and polysomnographical findings during drug-induced sleep endoscopy (DISE) performed with either propofol or midazolam as a single sedative agent. It is prospective, non-randomized, double-blinded case series study. Sixteen patients with sleep disordered breathing were sedated first with propofol and after full wake up with midazolam. Simultaneous polysomnography (PSG) was performed. We compared the zones of obstruction and vibration found with both drugs using the VOTE classification. Simultaneous PSG findings are also compared. There were 15 men and one woman; the mean age was 42.7 years old, mean body mass index 26.9 kg/m(2). Average DISE duration was 20 min with Propofol and 14.3 min with Midazolam. The induced sleep stage obtained was N2 with both drugs. Outpatient physical exam did not correlate with drug-induced sleep findings. There was a good correlation between DISE results with both drugs in all the areas of collapse except the velum (p < 0.005). Using a continuous perfusion, there is a good agreement in the findings observed in DISE performed with propofol and midazolam and PSG.

Obesity and obstructive sleep apnoea: mechanisms for increased collapsibility of the passive pharyngeal airway

Epidemiological evidence suggests there are significant links between obesity and obstructive sleep apnoea (OSA), with a particular emphasis on the importance of fat distribution in the development of OSA. In patients with OSA, the structure of the pharyngeal airway collapses. A collapsible tube within a rigid box collapses either due to decreased intraluminal pressure or increased external tissue pressure (i.e. reduction in transmural pressure), or due to reduction in the longitudinal tension of the tube. Accordingly, obesity should structurally increase the collapsibility of the pharyngeal airway due to excessive fat deposition at two distinct locations. In the pharyngeal airway region, excessive soft tissue for a given maxillomandibular enclosure size (upper airway anatomical imbalance) can increase tissue pressure surrounding the pharyngeal airway, thereby narrowing the airway. Even mild obesity may cause anatomical imbalance in individuals with a small maxilla and mandible. Lung volume reduction due to excessive central fat deposition may decrease longitudinal tracheal traction forces and pharyngeal wall tension, changing the 'tube law' in the pharyngeal airway (lung volume dependence of the upper airway). The lung volume dependence of pharyngeal airway patency appears to contribute more significantly to the development of OSA in morbidly obese, apnoeic patients. Neurostructural interactions required for stable breathing may be influenced by obesity-related hormones and cytokines. Accumulating evidence strongly supports these speculations, but further intensive research is needed.

Current opinions and clinical practice in the titration of oral appliances in the treatment of sleep-disordered breathing

Obstructive sleep apnea is characterized by recurrent obstruction of the upper airway during sleep, resulting in episodic reductions in blood oxygen saturation and arousals from sleep. Mandibular repositioning appliances (MRAs) which are worn intra-orally at night, mechanically advance the mandible to help maintain a patent oropharygeal airway and have been proven to be an effective alternative for continuous positive airway pressure in the treatment of obstructive sleep apnea. Titratable MRAs are designed to gradually protrude the mandible applying an easy-to-use mechanical advancing mechanism, until a protrusive position with positive effect on sleep apnea is reached. Considering the relatively low-tech approach of the basic advancement mechanism, the interest in the mechanistic element of the dental treatment of obstructive sleep apnea has increased. The present paper provides an overview of the different titration protocols described in the recent literature together with a discussion of both the clinical and mechanical aspects of treatment. At present, a consensus exists that an optimal titration protocol is of primary importance to achieve a successful treatment outcome with an MRA. To date however, there is no consensus on how to define the optimal titration protocol.

A method for measuring and modeling the physiological traits causing obstructive sleep apnea

There is not a clinically available technique for measuring the physiological traits causing obstructive sleep apnea (OSA). Therefore, it is often difficult to determine why an individual has OSA or to what extent the various traits contribute to the development of OSA. In this study, we present a noninvasive method for measuring four important physiological traits causing OSA: 1) pharyngeal anatomy/collapsibility, 2) ventilatory control system gain (loop gain), 3) the ability of the upper airway to dilate/stiffen in response to an increase in ventilatory drive, and 4) arousal threshold. These variables are measured using a single maneuver in which continuous positive airway pressure (CPAP) is dropped from an optimum to various suboptimum pressures for 3- to 5-min intervals during sleep. Each individual's set of traits is entered into a physiological model of OSA that graphically illustrates the relative importance of each trait in that individual. Results from 14 subjects (10 with OSA) are described. Repeatability measurements from separate nights are also presented for four subjects. The measurements and model illustrate the multifactorial nature of OSA pathogenesis and how, in some individuals, small adjustments of one or another trait (which might be achievable with non-CPAP agents) could potentially treat OSA. This technique could conceivably be used clinically to define a patient's physiology and guide therapy based on the traits.

Performance characteristics of upper airway critical collapsing pressure measurements during sleep

OBJECTIVE

The critical pressure (P(CRIT)), a measurement of upper airway collapsibility, is a determinant of the severity of upper airway obstruction during sleep. We examined the performance characteristics of the passive and active P(CRIT) by examining both within-night and between-night variability in the measurements.

METHODS

We studied 54 sleep apnea patients (39 men, 15 women) and 34 normal subjects (20 men, 14 women) on either 1 or 2 nights during sleep. The P(CRIT) was measured during relative hypotonia ("passive" state) or during periods of sustained upper airway obstruction used to recruit upper airway neuromuscular responses ("active" state) within- and between-nights. In a subgroup of 10 normal subjects, we performed repeated measurements during hypnotic-induced sleep. Bland-Altman analyses were used to determine the within-night and between-night reliability of the P(CRIT) measurements.

RESULTS

There were no significant within-night or between-night differences for the mean passive P(CRIT). The active P(CRIT) was ∼1 cm H(2)O more collapsible on the second night than on the first night. The limits of agreement, which bound the passive and active P(CRIT), was ∼ ± 3 cm H(2)O and was reduced to ∼ ± 1 cm H(2)O for the passive P(CRIT) with hypnotic-induced sleep.

CONCLUSION

Passive and active P(CRIT) measurements are reasonably reliable within and between nights. An approximately 3 cm H(2)O change in passive or active P(CRIT) appears to represent the minimally significant change in P(CRIT) necessary to assess the effect of an intervention (e.g., positional therapy, surgical interventions, oral appliance effects, and pharmacotherapy) on upper airway mechanical loads or neuromuscular responses.

The mandible advancement may alter the coordination between breathing and the non-nutritive swallowing reflex

The coordination between nasal breathing and non-nutritive swallowing serves as a protective reflex against potentially asphyxiating material, i.e. saliva and secretions, entering the respiratory tract. Although this protective reflex is influenced by positional changes in the head and body, the effect of mandible position on this reflex is not fully understood. We examined the effect of mandible advancement associated with mouth opening on the coordination between nasal breathing and non-nutritive swallowing induced by continuous infusion of distilled water into the pharyngeal cavity. The combination of mandible advancement and mouth opening increased the duration of swallowing apnoea and submental electromyographic burst duration. When the mandible was advanced with the mouth open, the duration of swallowing apnoea increased significantly compared with the centric position (0.79 +/- 0.23 vs. 0.64 +/- 0.12 s, P < 0.05, n = 12), and the duration of submental electromyographic activity increased significantly (2.11 +/- 0.63 vs. 1.46 +/- 0.25 s, P < 0.05, n = 12). Mandible advancement with mouth opening altered the respiratory phase resetting during swallowing and the timing of swallow in relation to respiratory cycle phase. We conclude that mandible re-positioning may strongly influence the coordination between nasal breathing and non-nutritive swallowing by altering respiratory parameters and by inhibiting movement of the tongue-jaw complex.

A new external upper airway opening device combined with a cervical collar

Airway problems are the main cause of mortality in otherwise survivable trauma injuries. We developed a novel external airway protector in combination with a cervical collar. The new device simultaneously opens the airway and protects the cervical spine.

MATERIALS AND METHODS

The device called the 'Lubo Collar' has a chin holder that can be attached to a gliding knob on the collar. When the knob is pushed forward, the mandible moves forward, thus imitating the jaw thrust manoeuvre and opens the airway. In order to study the safety and efficacy of this new device, a two-phase clinical trial was conducted. In the safety phase 20 patients were evaluated for adverse reactions immediately, 2h and 24h following application of the device. The efficacy phase evaluated the ability of the device to open and maintain an airway in anaesthetised patients. In this phase, 10 patients who had undergone orthopaedic surgery under general anaesthesia were included. Seven patients had blocked airways following anaesthesia induction. The gliding knob attached to the mandible arc was pushed 1cm forward to open their airways.

RESULTS

No adverse events were recorded. In the seven patients with blocked airways, the external airway/collar device opened and maintained patent airways.

CONCLUSION

The new external non-invasive airway device (Lubo Collar) is safe and effective in opening and maintaining an open airway in an unconscious anaesthetised patient with a blocked airway. These preliminary results may encourage assessment in the field.

Optimising the unprotected airway with a prototype Jaw-Thrust-Device--a prospective randomised cross-over study

Despite being a standard procedure during induction of anaesthesia, facemask ventilation can be a major challenge especially for inexperienced anaesthetists. We manufactured a Jaw-Thrust-Device designed to keep the patient's jaws in an optimised position, and thus to maintain the airway in a permanently patent state. Using a cross over design, we compared the influence of using the Esmarch manoeuvre (bimanual jaw-thrust), a nasopharyngeal airway, an oropharyngeal airway, or the Jaw-Thrust-Device on airway physiology in 50 healthy adults with body mass index < 35 kg.m(-2), undergoing standard facemask ventilation for routine induction of anaesthesia. The main study endpoints were expiratory tidal volumes, airway resistances, and gas flow rates. The Jaw-Thrust-Device was more effective in increasing expiratory tidal volumes and peak inspiratory flow than a standard Esmarch manoeuvre, and was more effective than both nasopharyngeal and oropharyngeal airways in decreasing airway resistance.

Obesity and upper airway control during sleep

Mechanisms linking obesity with upper airway dysfunction in obstructive sleep apnea are reviewed. Obstructive sleep apnea is due to alterations in upper airway anatomy and neuromuscular control. Upper airway structural alterations in obesity are related to adipose deposition around the pharynx, which can increase its collapsibility or critical pressure (P(crit)). In addition, obesity and, particularly, central adiposity lead to reductions in resting lung volume, resulting in loss of caudal traction on upper airway structures and parallel increases in pharyngeal collapsibility. Metabolic and humoral factors that promote central adiposity may contribute to these alterations in upper airway mechanical function and increase sleep apnea susceptibility. In contrast, neural responses to upper airway obstruction can mitigate these mechanical loads and restore pharyngeal patency during sleep. Current evidence suggests that these responses can improve with weight loss. Improvements in these neural responses with weight loss may be related to a decline in systemic and local pharyngeal concentrations of specific inflammatory mediators with somnogenic effects.

The effect of gender on compensatory neuromuscular response to upper airway obstruction in normal subjects under midazolam general anesthesia

BACKGROUND

Upper airway patency may be compromised during sleep and anesthesia by either anatomical alterations (mechanical properties) or disturbances in the neural control (compensatory neuromuscular responses). The pathophysiology of upper airway obstruction during anesthesia may differ between men and women. Recently, we reported that the upper airway mechanical properties were comparable with those found during natural nonrapid eye movement sleep, as evaluated by measurements of passive critical closing pressure (P(CRIT)) and upstream resistance (R(US)) during midazolam sedation. In this study, we compared the effects of gender on compensatory neuromuscular responses to upper airway obstruction during midazolam general anesthesia.

METHOD

Thirty-two subjects (14 men and 18 women) were studied. We constructed pressure-flow relationships to evaluate P(CRIT) and R(US) during midazolam anesthesia. The midazolam anesthesia was induced with an initial dose of midazolam (0.07-0.08 mg/kg bolus) and maintained by midazolam infusion (0.3-0.4 microg x kg(-1) x min(-1)), and the level of anesthesia was assessed by Ramsay score (Level 5) and Observer's Assessment of Alertness/Sedation score (Level 2). Polysomnographic and hemodynamic variables were monitored while nasal pressure (via mask), inspiratory air flow (via pneumotachograph), and genioglossal electromyograph (EMG(GG)) were recorded. P(CRIT) was obtained in both the passive condition, under conditions of decreased EMG(GG) (passive P(CRIT)), and in an active condition, whereas EMG(GG) was increased (active P(CRIT)). The difference between the active P(CRIT) and passive P(CRIT) (Delta P(CRIT) (P - A)) was calculated in each subject to determine the compensatory neuromuscular response.

RESULTS

The difference between the active P(CRIT) and passive P(CRIT) (Delta P(CRIT) (A - P)) was significantly greater in women than in men (4.6 +/- 2.8 cm H(2)O and 2.2 +/- 1.7 cm H(2)O, respectively; P < 0.01), suggesting greater compensatory neuromuscular response to upper airway obstruction independent of arousal.

CONCLUSION

We demonstrate that the arousal-independent compensatory neuromuscular responses to upper airway obstruction during midazolam anesthesia were partially maintained in women, and that gender may be a major determinant of the strength of compensatory responses during anesthesia.

The compensatory responses to upper airway obstruction in normal subjects under propofol anesthesia

Upper airway obstruction during sleep can trigger compensatory neuromuscular responses and/or prolong inspiration in order to maintain adequate minute ventilation. The aim of this study was to investigate the strength of these compensatory responses during upper airway obstruction during propofol anesthesia. We assessed respiratory timing and upper airway responses to decreases in nasal pressure in nine propofol anesthetized normal subjects under condition of decreased (passive) and increased (active) neuromuscular activity. Critical closing pressure (PCRIT) and upstream resistance (RUS) were derived from pressure-flow relationships generated from each condition. The inspiratory duty cycle (IDC), maximum inspiratory flow (V1max) and respiratory rate (f) were determined at two levels of mean inspiratory airflow (VI; mild airflow limitation with VI > or = 150 ml s-1; severe airflow limitation with VI < 150 ml s-1). Compared to the passive condition, PCRIT decreased significantly (5.3 +/- 3.8 cm H2O, p < 0.05) and RUS increased (7.4 cm H2O ml-1 s, p < 0.05) in the active condition. The IDC increased progressively and comparably as decreased in both the passive and active conditions (p < 0.05). These findings imply that distinct compensatory mechanisms govern the modulation of respiratory pattern and pharyngeal patency during periods of airway obstruction under propofol anesthesia.

Interacting effects of genioglossus stimulation and mandibular advancement in sleep apnea

Both mandibular advancement (MA) and stimulation of the genioglossus (GG) have been shown to improve upper airway patency, but neither one achieves the effect of continuous positive airway pressure (CPAP) treatment. In the present study we assessed the combined effect of MA and GG stimulation on the relaxed pharynx in patients with obstructive sleep apnea (OSA). We evaluated responses of upper airway pressure-flow relationships and endoscopically determined pharyngeal cross-sectional area to MA and electrical stimulation of the GG in 14 propofol-anesthetized OSA patients. Measurements were undertaken at multiple levels of CPAP, enabling calculation of the critical closing pressure (Pcrit), upstream resistance (Rus), and pharyngeal compliance. GG stimulation, MA, and the combination of both shifted the pressure:flow relationships toward higher flow levels, resulting in progressively lower Pcrit (from baseline of 2.9 +/- 2.2 to 0.9 +/- 2.5, -1.4 +/- 2.9, and -4.2 +/- 3.3 cmH(2)O, respectively), without significant change in Rus. DeltaPcrit during GG stimulation was significantly larger during MA than under baseline conditions (-2.8 +/- 1.4 vs. -2.0 +/- 1.4 cmH(2)O, P = 0.011). Combining the effect of GG stimulation with MA lowered Pcrit below 0 in all patients and restored pharyngeal patency to a level that enabled flow above the hypopnea level in 10/14 of the patients. Velopharyngeal compliance was not affected by either manipulation. We conclude that the combined effect of MA and GG stimulation is additive and may act in synergy, preventing substantial flow limitation of the relaxed pharynx in most OSA patients.

Effect of progressive mandibular advancement on pharyngeal airway size in anesthetized adults

BACKGROUND

General anesthesia in adult humans is associated with narrowing or complete closure of the pharyngeal airway. The purpose of this study was to determine the effect of progressive mandibular advancement on pharyngeal airway size in normal adults during intravenous infusion of propofol for anesthesia.

METHODS

Magnetic resonance imaging was performed in nine normal adults during wakefulness and during propofol anesthesia. A commercially available intraoral appliance was used to manually advance the mandible. Images were obtained during wakefulness without the appliance and during anesthesia with the participants wearing the appliance under three conditions: without mandibular advancement, advancement to 50% maximum voluntary advancement, and maximum advancement. Using computer software, airway area and maximum anteroposterior and lateral airway diameters were measured on the axial images at the level of the soft palate, uvula, tip of the epiglottis, and base of the epiglottis.

RESULTS

Airway area across all four airway levels decreased during anesthesia without mandibular advancement compared with airway area during wakefulness (P < 0.007). Across all levels, airway area at 50% advancement during anesthesia was less than that at centric occlusion during wakefulness (P = 0.06), but airway area with maximum advancement during anesthesia was similar to that during wakefulness (P = 0.64). In general, anteroposterior and lateral airway diameters during anesthesia without mandibular advancement were decreased compared with wakefulness and were restored to their wakefulness values with 50% and/or maximal advancement.

CONCLUSIONS

Maximum mandibular advancement during propofol anesthesia is required to restore the pharyngeal airway to its size during wakefulness in normal adults.

A pilot study of quantitative assessment of mandible advancement using pressure?flow relationship during midazolam sedation

It has been proposed that a titration of the mandibular positioner would be a promising method for predicting the outcome of nasal continuous positive airway pressure (CPAP) therapy. This study was carried out to test the hypothesis that mandible advancement could be evaluated by analysis of inspiratory flow limitation using a titration procedure. To explore its effect, we examined upper airway pressure-flow relationships using a titrated mandible positioner during midazolam sedation. Non-flow limited inspiration occurred when the mandible was advanced 7.1 +/- 1.2 mm from centric occlusion position. In the centric occlusion position (0 mm advancement), Pcrit was -1.9 +/- 2.9 cmH2O and Rua was 23.3 +/- 4.5 cmH2O L(-1) s(-1). In the eMAP position, Pcrit was -7.3 +/- 1.9 cmH2O and Rua was 27.8 +/- 3.3 cmH2O L(-1) s(-1). Essentially no CPAP was required to overcome flow limitation in eMAP position, whereas 3.7 +/- 2.2 cmH2O CPAP was required in centric occlusion position. We conclude that assessing inspiratory flow limitation using a titrated mandible positioner was effective for estimating individual-matched mandible positions.