Mechanisms underlying the prolonged activation of the genioglossus following arousal from sleep.

STUDY OBJECTIVES: Transient arousal from sleep has been shown to elicit a prolonged increase in genioglossus muscle activity that persists following the return to sleep and which may protect against subsequent airway collapse. We hypothesized that this increased genioglossal activity following return to sleep after an arousal is due to persistent firing of inspiratory-modulated motor units (MUs) that are recruited during the arousal. METHODS: Thirty-four healthy participants were studied overnight while wearing a nasal mask with pneumotachograph to measure ventilation and with 4 intramuscular genioglossus EMG electrodes. During stable N2 and N3 sleep, auditory tones were played to induce brief (3-15s) AASM arousals. Ventilation and genioglossus MUs were quantified before the tone, during the arousal and for 10 breaths after the return to sleep. RESULTS: A total of 1089 auditory tones were played and gave rise to 239 MUs recorded across arousal and the return to sleep in 20 participants (aged 23 ±â€…4.2 years and BMI 22.5 ±â€…2.2 kg/m2). Ventilation was elevated above baseline during arousal and the first post-arousal breath (p < .001). Genioglossal activity was elevated for five breaths following the return to sleep, due to increased firing rate and recruitment of inspiratory modulated MUs, as well as a small increase in tonic MU firing frequency. CONCLUSIONS: The sustained increase in genioglossal activity that occurs on return to sleep after arousal is primarily a result of persistent activity of inspiratory-modulated MUs, with a slight contribution from tonic units. Harnessing genioglossal activation following arousal may potentially be useful for preventing obstructive respiratory events.

Referral patterns for specialist child and adolescent mental health services in the Republic of Ireland during the COVID-19 pandemic compared with 2019 and 2018.

BACKGROUND: Countries worldwide are experiencing a third wave of the coronavirus disease 2019 (COVID-19) pandemic. Government-imposed restrictive measures continue with undetermined effects on physical and mental health. AIMS: To compare child and adolescent mental health services (CAMHS) referrals over 11 months (January-November) in 2020, 2019 and 2018 and examine any impact the different phases of the COVID-19 restrictions might have on referral rates. METHOD: Monthly CAMHS Health Service Executive data were examined, covering a catchment population of 260 560 or 12.7% of all youth (age group 0-18 years) in Ireland. The total number of urgent and routine referrals, appointments offered, rates of non-attendances and discharge outcome are presented. RESULTS: There was a significant drop in referrals in 2020, compared with prior years (χ2 = 10.3, d.f. = 2, P = 0.006). Referrals in 2020 dropped from March to May by 11% and from June to August by 10.3%. From September, both routine and urgent referrals increased by 50% compared with previous years (2018/2019), with the highest increase in November 2020 (180%). Clinic activity also increased from September, with double the number of out-patient appointments offered, compared with previous years (χ2 = 5171.72, d.f. = 3, P < 0.001) and lower (6.6%) rates of non-attendance (χ2 = 868.35, d.f. = 3, P < 0.001). CONCLUSIONS: In 2020, following an initial decline, referrals to CAMHS increased consistently from September. Such unprecedented increase in referrals places further strain on services that are already underresourced and underfunded, with the likelihood of increased waiting lists post COVID-19. It is envisaged that once the pandemic is over, resources will be even more constrained, and CAMHS will be urgently in need of additional ring-fenced funding.

After-discharge in the upper airway muscle genioglossus following brief hypoxia.

STUDY OBJECTIVES: Genioglossus (GG) after-discharge is thought to protect against pharyngeal collapse by minimizing periods of low upper airway muscle activity. How GG after-discharge occurs and which single motor units (SMUs) are responsible for the phenomenon are unknown. The aim of this study was to investigate genioglossal after-discharge. METHODS: During wakefulness, after-discharge was elicited 8-12 times in healthy individuals with brief isocapnic hypoxia (45-60 s of 10% O2 in N2) terminated by a single breath of 100% O2. GG SMUs were designated as firing solely, or at increased rate, during inspiration (Inspiratory phasic [IP] and inspiratory tonic [IT], respectively); solely, or at increased rate, during expiration (Expiratory phasic [EP] or expiratory tonic [ET], respectively) or firing constantly without respiratory modulation (Tonic). SMUs were quantified at baseline, the end of hypoxia, the hyperoxic breath, and the following eight normoxic breaths. RESULTS: A total of 210 SMUs were identified in 17 participants. GG muscle activity was elevated above baseline for seven breaths after hyperoxia (p < 0.001), indicating a strong after-discharge effect. After-discharge occurred due to persistent firing of IP and IT units that were recruited during hypoxia, with minimal changes in ET, EP, or Tonic SMUs. The firing frequency of units that were already active changed minimally during hypoxia or the afterdischarge period (p > 0.05). CONCLUSION: That genioglossal after-discharge is almost entirely due to persistent firing of previously silent inspiratory SMUs provides insight into the mechanisms responsible for the phenomenon and supports the hypothesis that the inspiratory and expiratory/tonic motor units within the muscle have idiosyncratic functions.

Does Nasal Obstruction Induce Obstructive Sleep Apnea in Healthy Women?

PURPOSE: Obstructive sleep apnea (OSA) is less prevalent among women and is associated with different symptoms and consequences to OSA in men. The reasons for these differences are unknown and difficult to tease apart in clinical populations. If OSA could be temporarily induced in healthy men and women, the causes of some of these differences could be investigated. Nasal blocking has been used to induce OSA in healthy men but its effect in women has not been reported. PATIENTS AND METHODS: A total of 14 healthy individuals (10 women) underwent in-laboratory diagnostic sleep studies on two occasions separated by a week. On one occasion, the nasal passages were blocked, whereas on the other occasion, participants slept naturally. In both conditions, a full-face mask was used to monitor respiratory events. Participants' self-reported sleepiness, mood and performance on a motor learning task were assessed in the evening and morning of both sleep studies. Furthermore, endothelial function and self-reported sleep quality were assessed in the morning following each study. RESULTS: Nasal blockage induced OSA in healthy young (age=22±3 years) and slim (BMI=22.2±3.2 kg/m2) women (control AHI=2.0±2.6, blocked AHI=33.1±36.7 events/hr, p=0.02). One night of OSA was associated with poorer self-reported sleep quality (p<0.001) and increased self-reported snoring (p<0.04), choking and gasping during sleep (p<0.001) but was not associated with alterations in mood, neurocognitive or endothelial function on the following morning. CONCLUSION: Nasal blockage induces OSA in healthy, young, and normal weight women. However, whether the induced OSA is representative of naturally occurring OSA and the technique useful for future studies is unclear.

Arousal-Induced Hypocapnia Does Not Reduce Genioglossus Activity in Obstructive Sleep Apnea.

Study Objectives: To determine whether arousals that terminate obstructive events in obstructive sleep apnea (OSA) (1) induce hypocapnia and (2) subsequently reduce genioglossus muscle activity following the return to sleep. Methods: Thirty-one untreated patients with OSA slept instrumented with sleep staging electrodes, nasal mask and pneumotachograph, end-tidal CO2 monitoring, and intramuscular genioglossus electrodes. End-tidal CO2 was monitored, and respiratory arousals were assigned an end-arousal CO2 change value (PETCO2 on the last arousal breath minus each individual's wakefulness PETCO2). This change value, in conjunction with the normal sleep related increase in PETCO2, was used to determine whether arousals induced hypocapnia and whether the end-arousal CO2 change was associated with genioglossus muscle activity on the breaths following the return to sleep. Results: Twenty-four participants provided 1137 usable arousals. Mean ± SD end-arousal CO2 change was -0.2 ± 2.4 mm Hg (below wakefulness) indicating hypocapnia typically developed during arousal. Following the return to sleep, genioglossus muscle activity did not fall below prearousal levels and was elevated for the first two breaths. End-arousal CO2 change and genioglossus muscle activity were negatively associated such that a 1 mm Hg decrease in end-arousal CO2 was associated with an ~2% increase in peak and tonic genioglossus muscle activity on the breaths following the return to sleep. Conclusions: Arousal-induced hypocapnia did not result in reduced dilator muscle activity following return to sleep, and thus hypocapnia may not contribute to further obstructions via this mechanism. Elevated dilator muscle activity postarousal is likely driven by non-CO2-related stimuli.

The highs and lows of the interaction between word meaning and space.

We examined whether the processing of words associated with distinct spatial locations automatically biases behavior toward these locations in space. In four experiments (Ns = 30, 34, 32, 32), participants were shown stimuli denoting objects typically associated with the upper and lower regions of visual space. In Experiment 1, words were categorized as man-made or natural by pressing one of two vertically arranged keys. Reaction times were faster for trials in which response locations were congruent with the stimulus-associated locations. Experiment 2 replicated the stimulus-response congruency effect when the stimuli were presented in a pictorial format. Stimuli-space interactions therefore seem to be driven by an automatic activation of the spatial attributes associated with the stimuli, irrespective of input format. In Experiments 3 and 4, a target detection task involving only one response button was employed to examine whether the effects observed in the first two experiments were due to attentional shifts, independent of response selection processes. In both experiments, the previously observed congruence effect between words and space either diminished or vanished completely. Consequently, the results of the four experiments in the current study point to a dominant role of response-selection processes in the genesis of space-object word interactions.