Respiratory support with nasal high flow without supplemental oxygen in patients undergoing endoscopic retrograde cholangiopancreatography under moderate sedation: a prospective, randomized, single-center clinical trial.

BACKGROUND: Nasal high flow (NHF) may reduce hypoxia and hypercapnia during an endoscopic retrograde cholangiopancreatography (ERCP) procedure under sedation. The authors tested a hypothesis that NHF with room air during ERCP may prevent intraoperative hypercapnia and hypoxemia. METHODS: In the prospective, open-label, single-center, clinical trial, 75 patients undergoing ERCP performed with moderate sedation were randomized to receive NHF with room air (40 to 60 L/min, n = 37) or low-flow O2 via a nasal cannula (1 to 2 L/min, n = 38) during the procedure. Transcutaneous CO2, peripheral arterial O2 saturation, a dose of administered sedative and analgesics were measured. RESULTS: The primary outcome was the incidence of marked hypercapnia during an ERCP procedure under sedation observed in 1 patient (2.7%) in the NHF group and in 7 patients (18.4%) in the LFO group; statistical significance was found in the risk difference (-15.7%, 95% CI -29.1 - -2.4, p = 0.021) but not in the risk ratio (0.15, 95% CI 0.02 - 1.13, p = 0.066). In secondary outcome analysis, the mean time-weighted total PtcCO2 was 47.2 mmHg in the NHF group and 48.2 mmHg in the LFO group, with no significant difference (-0.97, 95% CI -3.35 - 1.41, p = 0.421). The duration of hypercapnia did not differ markedly between the two groups either [median (range) in the NHF group: 7 (0 - 99); median (range) in the LFO group: 14.5 (0 - 206); p = 0.313] and the occurrence of hypoxemia during an ERCP procedure under sedation was observed in 3 patients (8.1%) in the NHF group and 2 patients (5.3%) in the LFO group, with no significant difference (p = 0.674). CONCLUSIONS: Respiratory support by NHF with room air did not reduce marked hypercapnia during ERCP under sedation relative to LFO. There was no significant difference in the occurrence of hypoxemia between the groups that may indicate an improvement of gas exchanges by NHF. TRIAL REGISTRATION: jRCTs072190021 . The full date of first registration on jRCT: August 26, 2019.

Involvement of spinal G-protein inwardly rectifying potassium (GIRK) channels in the enhanced antinociceptive effects of the activation of both µ-opioid and cannabinoid CB1 receptors.

Neuropathic pain is refractory to opioid analgesics. Since there are functional linkages between µ-opioid receptors (MOR) and cannabinoid receptors (CBR), the present study was designed to investigate the interactions between MOR and CB1R based on antinociceptive effects for neuropathic pain mediated through G protein-coupled inwardly-rectifying potassium channels (GIRKs). The antinociceptive effects against pseudonociceptive response or neuropathic pain of MOR and CBR agonists were assessed in mice with or without partial sciatic nerve ligation. To investigate the functional interaction between MOR and CB1R, electrophysiological recording through GIRK was performed using the two-electrode voltage-clamp method in oocytes along with Western blotting in the spinal cord of mice. Co-administration of the MOR agonist DAMGO and the CB1R agonist CP55,940 augmented inwardly rectifying K+ currents in Xenopus oocytes co-expressing MOR, CB1R and GIRK1/2. Further, combination of morphine and the CBR agonist WIN-55,212-2 produced prominent antinociceptive effects in an i.t. GIRK1 inhibitor-reversible manner. Furthermore, CB1R was upregulated under neuropathic pain in the spinal cord, and such upregulation and antinociceptive effects were not altered by repeated treatment with morphine plus WIN-55,212-2. Our findings suggest that co-administration of MOR and CBR agonists could enhance their antinociceptive effects through GIRK1 in the spinal cord of mice.

Effect of nasal high-flow oxygen therapy on the swallowing reflex: an in vivo volunteer study.

OBJECTIVE: The advantages of nasal high-flow oxygen therapy (NHF) include not only allowing talking, but also eating and drinking, during the therapy. However, the effect of NHF on the swallowing reflex remains unclear. In the present study, we aimed to assess the effects of NHF on the swallowing reflex. METHODS: Nine healthy adult Japanese male volunteers with no history of dysphagia or diseases that may cause dysphagia, such as stroke or Parkinson's disease, were evaluated. Participants received one of four levels of NHF intervention (0 (control), 15, 30 and 45 L/min of oxygen) with the NHF system through the nasal cannula. Swallowing was induced by the administration of a bolus injection of 5 mL of distilled water over 3 s through a polyethylene catheter at each level of oxygen flow. The primary end-point was the latency period of the swallowing reflex after bolus injection, which was defined as the time from the start of the bolus injection to the onset of the electromyogram (EMG) burst of the first swallow. RESULTS: Mean latency times of the swallowing reflex with 15 (9.8 ± 2.9 s), 30 (9.0 ± 2.7 s) and 45 (8.5 ± 3.0 s) L/min of NHF were significantly shorter than those under control conditions (11.9 ± 3.7 s; P < 0.05). CONCLUSIONS: Our study demonstrates that NHF may enhance swallowing function with increasing levels of NHF by reducing the latency of the reflex. CLINICAL RELEVANCE: NHF may allow continuation of oral intake without aspiration during oxygen therapy.

Nitrous Oxide Inhalation Sedation Through a Nasal High-Flow System: The Possibility of a New Technique in Dental Sedation.

High-flow nasal cannula (HFNC) systems are increasingly used for patients with both acute and chronic respiratory failure because of the clinical effectiveness and patient comfort associated with their use. Recently, HFNC has been used not only as a respiratory support device, but also as a drug delivery system. HFNC is designed to administer heated and humidified inspiratory oxygen flows (100% relative humidity at 37°C). Therefore, HFNC can provide high flows (up to 60 L/min) without discomfort. Moreover, HFNC improves oxygenation by exerting physiologic effects such as (a) dead-space washout and (b) moderate positive airway pressure. These characteristics and physiologic effects of HFNC may permit administration of high-flow nitrous oxide sedation while ensuring patient comfort and adequate sedative effect.

Anaphylactoid-like Reaction to Midazolam During Oral and Maxillofacial Surgery.

We experienced a case of life-threatening hypotension and bronchoconstriction associated with edema in a patient undergoing resection of a tumor of the right mandible following intravenous midazolam for induction of general anesthesia. We decided to postpone surgery for further examination of a possible drug-induced allergic reaction, and we rescheduled surgery for 1 week later. After administering H1 and H2 histamine antagonists, we administered a slow induction with sevoflurane in nitrous oxide and oxygen plus intravenous atropine sulfate after performing a test dose injection. We safely induced and maintained anesthesia with nitrous oxide, oxygen, and sevoflurane.

Perioperative management of tooth extractions for a patient with hereditary angioedema.

Hereditary angioedema (HAE) is a rare genetic disorder that causes a deficiency in or dysfunction of C1 esterase inhibitor (C1-INH) and is clinically characterized by sudden and recurrent attacks of angioedema. Although almost any part of the body can be affected, HAE is of greatest concern and can be life-threatening when the upper airway is involved, particularly the larynx (laryngeal attack). HAE attacks can be triggered by physical or psychological stress or can arise spontaneously without any apparent trigger. Dental treatments and routine oral surgical procedures, such as tooth extraction, abound with factors that can trigger an attack of HAE. Indeed, several cases of death resulting from HAE attacks have been reported after such procedures. Therefore, patients with HAE are of special concern in dentistry and require precautionary preparations before treatment. This report describes the successful management of tooth extractions in a patient with HAE who was at high risk of an HAE-induced laryngeal attack.

Upside-down mask ventilation technique for a patient with a long and narrow mandible.

Mask ventilation, along with tracheal intubation, is one of the most basic skills for managing an airway during anesthesia. Facial anomalies are a common cause of difficult mask ventilation, although numerous other factors have been reported. The long and narrow mandible is a commonly encountered mandibular anomaly. In patients with a long and narrow mandible, the gaps between the corners of the mouth and the lower corners of the mask are likely to prevent an adequate seal and a gas leak may occur. When we administer general anesthesia for these patients, we sometimes try to seal the airway using several sizes and shapes of commercially available face masks. We have found that the management of the airway for patients with certain facial anomalies may be accomplished by attaching a mask upside down.

A Case Report of Burning Mouth Syndrome with Dry Mouth Managed by Kampo Medicine.

The patient was a 56-year-old woman who complained of chronic pain involving her tongue. We diagnosed her with burning mouth syndrome (BMS) based on exclusion of any local factors or systemic conditions. The patient not only had tongue pain but also had other signs and symptoms like scalloped tongue, dry mouth, and headache. To manage these additional issues, we used Goreisan, an herbal Kampo medicine, as a complementary alternative medicine (CAM) approach along with cognitive behavioral therapy (CBT). The patient's BMS was successfully managed with the combination of CAM and CBT, which may suggest that the pathophysiology for BMS might be nociplastic pain rather than purely nociceptive or neuropathic.

Safety of COVID-19 vaccine delivery by dentists: An observational cohort study.

Background/purpose: Although many coronavirus disease 2019 (COVID-19) vaccine injections have been administered worldwide, the safety of this practice remains unclear. This study aimed to compare the rates of complications associated with COVID-19 vaccines administered by dentists with those of vaccines administered by nurses. This study aimed to evaluate the safety of a vaccination program delivered by dentists. Materials and methods: This observational cohort study included 537 recipients of the second dose of the Pfizer COVID-19 vaccine, delivered as an intramuscular injection to the upper arm deltoid muscle by dentists or nurses at the study site. Vaccine recipients were divided into two groups according to the vaccination administrator (dentist vs. nurse groups). The rates of complications associated with intramuscular injection technique (numbness in the hand or arm at the time of the injection, vasovagal reflex at the time of the injection, vaccine-related shoulder injury, and prolonged numbness) were examined. Results: A total of 125 vaccine recipients were included (nurse group, n = 84; dentist group, n = 41). The overall incidence rate of complications was lower in the dentist group (2.4%; 1/41) than in the nurse group (8.3%; 7/84). However, this difference was not statistically significant (P = 0.3). Conclusion: This study suggests that the safety of COVID-19 vaccine administration is comparable between dentists and nurses.

Examination of stabilization of sedation by Nasal High Flow in patients with endoscopic retrograde cholangiopancreatography during sedation using Dexmedetomidine.

INTRODUCTION: Dexmedetomidine is used for the sedation method in the case of endoscopic retrograde cholangiopancreatography (ERCP) for the purpose of relieving patient anxiety. It has been reported that CO2 accumulated during sedation causes an arousal reaction, so how to normalize CO2 during sedation can be improved by administration of the minimum necessary sedative.Nasal High Flow oxygen therapy (NHF) uses a mild positive pressure load that improves carbon dioxide washout and reduces rebreathing to improve respiratory function and therefore is widely used to prevent hypoxemia and hypercapnia. In this study, we will investigate whether the upper airway patency would be maintained and the hypercapnia and hypoxemia during sedation would be prevented, by applying NHF as a respiratory management method to patients undergoing ERCP under sedation. METHODS/DESIGN: In a randomized comparative study of 2 groups, the NHF device use group and the nasal cannula use group, for adult patients who visited the Nagasaki University Hospital and underwent ERCP examination under sedation. For sedation, Dexmedetomidine will be used in combination with and Midazolam and evaluation by anesthesiologist. In addition, as an analgesic, pethidine hydrochloride was administered intravenously. The total dose of the analgesic pethidine hydrochloride used in combination is used as the primary endpoint. As a secondary evaluation item, the percutaneous CO2 concentration is evaluated with a TCO2 monitor to examine whether it is effective in preventing hypercapnia. Furthermore, we will evaluate the incidence of hypoxemia with a percutaneous oxygen saturation value of 90% or less, and examine whether the use of equipment is effective in preventing the occurrence of hypercapnia and hypoxemia. DISCUSSION: The purpose of this study was to obtain evidence for the utility of NHF as a potential therapeutic device for patients undergoing an ERCP under sedation, assessed by determining if the incidence rates of hypercapnia and hypoxemia decreased in the NHF device group, compared to the control group that did not use of this device.

Influence of general anesthesia on the postoperative sleep cycle in patients undergoing surgery and dental treatment: a scoping review on the incidence of postoperative sleep disturbance.

General anesthesia may influence the postoperative sleep cycle; however, no clinical studies have fully evaluated whether anesthesia causes sleep disturbances during the postoperative period. In this scoping review, we explored the changes in postoperative sleep cycles during surgical procedures or dental treatment under general anesthesia. We compared and evaluated the influence of general anesthesia on sleep cycles and sleep disturbances during the postoperative period in adult and pediatric patients undergoing surgery and/or dental treatment. Literature was retrieved by searching eight public databases. Randomized clinical trials, observational studies, observational case-control studies, and cohort studies were included. Primary outcomes included the incidence of sleep, circadian cycle alterations, and/or sleep disturbances. The search strategy yielded six studies after duplicates were removed. Finally, six clinical trials with 1,044 patients were included. In conclusion, general anesthesia may cause sleep disturbances based on alterations in sleep or the circadian cycle in the postoperative period in patients scheduled for elective surgery.

The Impact of COVID-19 on Dental Anesthesiologists: An Online Survey of Board-Certified Dental Anesthesiology Specialists of the Japanese Dental Society of Anesthesiology.

OBJECTIVE: The impact of the COVID-19 pandemic on dental anesthesiologists has not been examined. This study aimed to determine how the COVID-19 pandemic affected Japanese dental anesthesiologists' professional lives. METHODS: An online questionnaire related to the effects of COVID-19 on dental anesthesiologists' professional lives was emailed to 351 board-certified dental anesthesiology specialists from the Japanese Dental Society of Anesthesiology. The endpoints of this study were changes in income and job satisfaction as a dental anesthesiologist from 2019 prior to the COVID-19 pandemic. RESULTS: A total of 141 dental anesthesiologists participated in the survey. Most respondents reported no change in income relative to 2019 for 2020 or 2021. Significantly more dental anesthesiologists reported income decreases relative to 2019 for 2020 (39%) vs 2021 (21.3%; P = .001). Very few dental anesthesiologists reported income increases relative to 2019 for 2020 (2.1%) vs 2021 (15.6%; P < .001). Job satisfaction as a dental anesthesiologist remained unchanged for all 3 years. CONCLUSION: Even though many Japanese dental anesthesiologist specialists lost income because of COVID-19, they maintained their job satisfaction.

GABA(B) receptors do not internalize after baclofen treatment, possibly due to a lack of ß-arrestin association: study with a real-time visualizing assay.

The mechanism of agonist-induced GABA(B) receptor (GABA(B) R) internalization is not well understood. To investigate this process, we focused on the interaction of GABA(B) R with ß-arrestins, which are key proteins in the internalization of most of the G protein-coupled receptors, and the agonist-induced GABA(B) R internalization and the interaction of GABA(B) R with ß-arrestin1 and ß-arrestin2 were investigated in real time using GABA(B) R and ß-arrestins both of which were fluorescent protein-tagged. We then compared these profiles with those of µ-opioid receptors (µOR), well-studied receptors that associate and cointernalize with ß-arrestins. When stimulated by the specific GABA(B) R agonist baclofen, GABA(B) R composed of GABA(B1a) R (GB(1a) R) and fluorescent protein-tagged GABA(B2) R-Venus (GB2 R-V) formed functional GABA(B) R; they elicited G protein-activated inwardly rectifying potassium channels as well as nontagged GABA(B) R. In cells coexpressing GB(1a) R, GB2 R-V, and ß-arrestin1-Cerulean (ßarr1-C) or ß-arrestin2-Cerulean (ßarr2-C), real-time imaging studies showed that baclofen treatment neither internalized GB2 R-V nor mobilized ßarr1-C or ßarr2-C to the cell surface. This happened regardless of the presence of G protein-coupled receptor kinase 4 (GRK4), which forms a complex with GABA(B) R and causes GABA(B) R desensitization. On the other hand, in cells coexpressing µOR-Venus, GRK2, and ßarr1-C or ßarr2-C, the µOR molecule formed µOR/ßarr1 or µOR/ßarr2 complexes on the cell surface, which were then internalized into the cytoplasm in a time-dependent manner. Fluorescence resonance energy transfer assay also indicated scarce association of GB2 R-V and ß-arrestins-C with or without the stimulation of baclofen, while robust association of µOR-V with ß-arrestins-C was detected after µOR activation. These findings suggest that GABA(B) Rs failure to undergo agonist-induced internalization results in part from its failure to interact with ß-arrestins.

Dental treatment under intravenous sedation prolongs longevity of a fixed prosthesis in patients with intellectual disabilities.

AIMS: This study aimed to assess the longevity of a fixed prosthesis in patients with intellectual disability (ID) and to investigate the risk factors associated with the failure of a prosthesis due to abutment tooth extraction or prosthesis dislodgement or removal. METHODS: We studied past medical records to evaluate the longevity of 315 prostheses that were luted in 76 patients with ID. We calculated the survival rates and assessed 15 variables potentially associated with prosthetic failure using multivariate Cox regression analyses with shared frailty for patients. RESULTS: Three-quarters of our sample population had severe or profound ID. The maximum observation period was 31.0 years, and the corresponding survival ratio was 32.5%; the survival ratio at 10 years was 59.4%. The use of intravenous sedation significantly influenced the success of the prosthesis, with the hazard ratio (HR) being 0.49 times that of conventional treatment without behavior-altering drug therapy. The most significant risk factor for prosthetic failure was age at placement; the HR for patients aged ≥31 years was 2.82 times that for patients aged ≤ 20 years. CONCLUSIONS: In patients with severe ID, appropriate intravenous sedation was effective in prolonging the longevity of a fixed prosthesis.

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.

Effect of head elevation on passive upper airway collapsibility in normal subjects during propofol anesthesia.

BACKGROUND: Head elevation can restore airway patency during anesthesia, although its effect may be offset by concomitant bite opening or accidental neck flexion. The aim of this study is to examine the effect of head elevation on the passive upper airway collapsibility during propofol anesthesia. METHOD: Twenty male subjects were studied, randomized to one of two experimental groups: fixed-jaw or free-jaw. Propofol infusion was used for induction and to maintain blood at a constant target concentration between 1.5 and 2.0 µg/ml. Nasal mask pressure (PN) was intermittently reduced to evaluate the upper airway collapsibility (passive PCRIT) and upstream resistance (RUS) at each level of head elevation (0, 3, 6, and 9 cm). The authors measured the Frankfort plane (head flexion) and the mandible plane (jaw opening) angles at each level of head elevation. Analysis of variance was used to determine the effect of head elevation on PCRIT, head flexion, and jaw opening within each group. RESULTS: In both groups the Frankfort plane and mandible plane angles increased with head elevation (P < 0.05), although the mandible plane angle was smaller in the free-jaw group (i.e., increased jaw opening). In the fixed-jaw group, head elevation decreased upper airway collapsibility (PCRIT ~ -7 cm H2O at greater than 6 cm elevation) compared with the baseline position (PCRIT ~ -3 cm H2O at 0 cm elevation; P < 0.05). CONCLUSION: : Elevating the head position by 6 cm while ensuring mouth closure (centric occlusion) produces substantial decreases in upper airway collapsibility and maintains upper airway patency during anesthesia.

Successful Dental Treatments Using Procaine Hydrochloride in a Patient Afraid of Local Anesthesia but Consenting for Allergic Testing with Lidocaine: A Case Report.

BACKGROUND: We report a case in which effective dental anesthetic management was achieved using procaine hydrochloride for a patient who had an unknown history of allergic reactions to lidocaine. CASE PRESENTATION: Because the patient refused to undergo screening tests using any of the amide-type local anesthetics because of her extreme fear against local anesthetics that she had been administered previously, procaine hydrochloride, which is an ester-form local anesthetic, was the only agent to be tested on this patient at the department of dermatology. Consequent to a negative allergy test, we performed complete dental treatment using procaine hydrochloride after additional chairside drug challenge tests using minimum test dose under vital sign monitoring. CONCLUSION: The success of dental treatment using procaine hydrochloride may have relieved the patient's fear of local anesthesia. We discuss an important aspect of treatment planning for patients with a history of complications during local anesthesia.

A study on respiratory management in acute postoperative period by nasal high flow for patients undergoing surgery under general anesthesia.

In head and neck surgery where the oropharyngeal area is the operative field, postoperative respiratory depression and upper airway obstruction are common. Therefore, supplemental oxygen is administered to prevent severe postoperative early hypoxemia. However, a high concentration of oxygen increases the likelihood of secondary complications, such as carbon dioxide (CO2) narcosis. Nasal high-flow (NHF) therapy generates high flows (≤60 L/min) of heated and humidified gas delivered via nasal cannula and provides respiratory support by generating positive airway pressure, clearance of dead space and reduction of work of breathing. This study aims to determine whether the postoperative hypoxemia and hypercapnia can be prevented by NHF without the requirement of supplemental oxygen. The study will recruit adult patients undergoing planned oral surgery under general anesthesia at Nagasaki University Hospital. It is a randomized parallel group comparative study with 3 groups: NHF with room air only and no supplemental oxygen, no respiratory support, and face mask oxygen administration. The study protocol will begin at the time that the patient is returned to the general ward and will finish 3 hours later. The primary endpoint is the time-weighted average of transcutaneous O2 over the 180 minutes and secondary endpoints are the time-weighted average of transcutaneous CO2 (tcpCO2), SpO2, and respiratory rate, incidence rate of marked hypercapnia (tcpCO2 ≥60 mm Hg for 5 minutes or longer), incidence rate of moderate hypercapnia (tcpCO2 ≥50 mm Hg for 5 minutes or longer) and the percentage of time that SpO2 is <90%. Included also is a group in which the postoperative management is performed only by spontaneous breathing without performing respiratory support such as oxygen administration, to investigate the efficacy and necessity of conventional oxygen administration. This exploratory study will investigate the use of NHF without supplemental oxygen as an effective respiratory support during the acute postoperative period. TRIAL REGISTRATION:: The study was registered the jRCTs072200018. URL https://jrct.niph.go.jp/latest-detail/jRCTs072200018.

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.