Mandibular advancement impairs swallowing ability more than head extension but less than mouth opening in the supine position

Striving for humane deaths for laboratory mice: hypobaric hypoxia provides a potential alternative to carbon dioxide exposure

Killing is often an unavoidable and necessary procedure for laboratory mice involved in scientific research, and providing a humane death is vital for public acceptance. Exposure to carbon dioxide (CO2) gas is the most widely used methodology despite well proven welfare concerns. Consequently, the continued use of CO2 and its globally permitted status in legislation and guidelines presents an ethical dilemma for users. We investigated whether killing with hypobaric hypoxia via gradual decompression was associated with better welfare outcomes for killing laboratory mice. We compared the spontaneous behaviour of mice exposed to CO2, decompression or sham conditions, and used analgesic or anxiolytic interventions to determine their relative welfare impact. Gradual decompression resulted in longer times to unconsciousness and death and the pharmacological interventions support the notion of a minimally negative animal experience, while providing further evidence for pain and anxiety associated with exposure to CO2. Decompression resulted in moderate ear haemorrhage, but our welfare assessment suggests this may happen when mice are unconscious. Hence, gradual decompression could be the basis of significant refinement for killing laboratory mice. Future work should corroborate behaviour with neurobiological markers of loss of consciousness to verify the conscious phase of concern for animal welfare.

Comparison of the innovative endoscopic oropharyngeal airway and the conventional mouthpiece in elderly outpatients undergoing esophagogastroduodenoscopy under sedation: a prospective and randomized study

Background

Undesirable outcomes may appear for elderly patients undergoing esophagogastroduodenoscopy (EGD) under sedation, such as hypoxia and hypotension. The aim of our study was to investigate the ability of the innovative endoscopic oropharyngeal airway to reduce the frequency of hypoxia during EGD under sedation in elderly patients.

Methods

In this trial, aged patients undergoing EGD were randomized into airway group and mouthpiece group. The primary outcome was the incidence of the minimum pulse oxygen saturation < 90% and minimum pulse oxygen saturation. In addition, sedation dose, recovery time, emergency management and adverse reactions were recorded.

Results

360 patients completed the study (180 in each groups). The minimum pulse oxygen saturation during EGD was significantly higher in airway group (97.66 ± 2.96%) than in mouthpiece group (95.52 ± 3.84%, P < 0.001). The incidence of pulse oxygen saturation of 85–89% of airway group (5.0%, 9/180) was lower than mouthpiece group (10.6%, 19/180, P = 0.049). The endoscopy entry time in airway group was 3 (2, 4) seconds and in mouthpiece group was 5 (4, 6) (P < 0.001). Propofol total dose and awakening time were significantly lower in the airway group than in the mouthpiece group (P = 0.020 and P = 0.012, respectively). Furthermore, the incidence rate of hypotension was significantly higher in mouthpiece group (12.2%) than in airway group (5.0%) (P = 0.015). By comparison with the mouthpiece group, the satisfaction of endoscopists was higher in airway group (P = 0.012).

Conclusion

Elderly patients undergoing EGD, Endoscopy Protector was associated with a significantly lower incidence of hypoxia, shortened endoscopy entry time and more stable hemodynamics.

Trial registration: ChiCTR, ChiCTR2000031998, 17/04/2020. http://www.chictr.org.cn/index.aspx

Effect of mandibular advancement device on plasticity in corticomotor control of tongue and jaw muscles

STUDY OBJECTIVES

This study aims to investigate if the use of a mandibular advancement device (MAD) is associated with neuroplasticity in corticomotor control of tongue and jaw muscles.

METHODS

Eighteen healthy individuals participated in a randomized crossover study with 3 conditions for 2 weeks each: baseline, wearing an oral appliance (OA: sham MAD) or MAD during sleep. The custom-made MAD was constructed by positioning the mandible to 50% of its maximal protrusion limit. Transcranial magnetic stimulation (TMS) was applied to elicit motor evoked potentials (MEPs). The MEPs were assessed by constructing stimulus-response curves at four stimulus intensities: 90%, 100%, 120%, and 160% of the motor threshold (MT) from the right tongue and right masseter, and the first dorsal interosseous muscles (FDI, control) at baseline, after the first and the second intervention.

RESULTS

There was a significant effect of condition and stimulus intensity both on the tongue and as well as on masseter MEPs (P < 0.01). Tongue and masseter MEPs were significantly higher at 120% and 160% following the MAD compared to the OA (P < 0.05). There were no effects of condition on FDI MEPs (P = 0.855).

CONCLUSIONS

The finding suggests that MAD induces neuroplasticity in the corticomotor pathway of the tongue and jaw muscles associated with the new jaw position. Further investigations are required in patients with obstructive sleep apnea (OSA) to see if this cortical neuroplasticity may contribute or perhaps predict treatment effects with MADs in OSA.

Swallowing ability and intra-oral water-retaining ability during moderate propofol sedation in healthy human volunteers: A prospective observational study

BACKGROUND

The cough reflex or aspiration under monitored anaesthesia care might be associated with sedative-induced changes in swallowing and intra-oral water-retaining abilities.

OBJECTIVES

To investigate the effects of moderate propofol sedation on swallowing and intra-oral water-retaining ability.

DESIGN

Prospective observational study.

SETTING

Single tertiary care centre during 2017.

PARTICIPANTS

A total of 13 healthy adult volunteers.

INTERVENTION

Volunteers in the supine position were asked to retain 10 ml of orally injected water for 5 min. After 5 minutes or when the water was spontaneously swallowed, the retention time and residual intra-oral water volume were measured. Subjects then voluntarily swallowed a further 10 ml of injected water and the residual water volume was measured. This whole process was repeated under sedation with propofol at effect-site concentrations of 0.5, 1.0 and 1.5 μg ml-1.

MAIN OUTCOME MEASURES

The primary outcome was the estimated volume swallowed (swallowing volume); the secondary outcome was water retention time.

RESULTS

Median water retention time decreased from 300 to 11 s (P < 0.001), and greater spontaneous swallowing was induced with increased propofol effect-site concentrations measuring up to 1.5 μg ml-1 (P < 0.001). The median of the estimated swallowing volumes with voluntary swallowing while awake and with all three concentrations of propofol were 9.5, 9.6, 9.6 and 9.4 ml, respectively (P = 0.805); more water remained after spontaneous swallowing than after voluntary swallowing at all concentrations. Differences in mean estimated swallowing volumes between voluntary and spontaneous swallowing were 3.4 ml (95% CI, 0.9 to 6.0, P = 0.016) for 0.5 μg ml-1, 4.1 ml (95% CI, 1.8 to 6.3, P = 0.002) for 1.0 μg ml-1 and 5.1 ml (95% CI, 3.4 to 6.8, P < 0.001) for 1.5 μg ml-1.

CONCLUSIONS

Moderate propofol sedation decreases water-retaining ability but has no effect on voluntary swallowing. Ensuring that patients can respond under sedation may effectively prevent the unexpected cough reflex and aspiration by enabling occasional voluntary swallowing.

TRIAL REGISTRATION

UMIN Clinical Trials Registry identifier: UMIN000027517.