Artificial sharp-wave-ripples to support memory and counter neurodegeneration.

Information processed in our sensory neocortical areas is transported to the hippocampus during memory encoding, and between hippocampus and neocortex during memory consolidation, and retrieval. Short bursts of high-frequency oscillations, so called sharp-wave-ripples, have been proposed as a potential mechanism for this information transfer: They can synchronize neural activity to support the formation of local neural networks to store information, and between distant cortical sites to act as a bridge to transfer information between sensory cortical areas and hippocampus. In neurodegenerative diseases like Alzheimer's Disease, different neuropathological processes impair normal neural functioning and neural synchronization as well as sharp-wave-ripples, which impairs consolidation and retrieval of information, and compromises memory. Here, we formulate a new hypothesis, that artificially inducing sharp-wave-ripples with noninvasive high-frequency visual stimulation could potentially support memory functioning, as well as target the neuropathological processes underlying neurodegenerative diseases. We also outline key challenges for empirical tests of the hypothesis.

Poor Sleep Associated with Clinically Severe Obesity Is Independent of OSA Status.

PURPOSE: Obesity has been reported to be associated with short sleep duration. It follows that patients with a BMI >35kg/m2 could be expected to have the poorest sleep. This poor sleep could be explained by the presence of obstructive sleep apnoea (OSA), although treatment with positive airway pressure (PAP) may modify this. The purpose of this study is to determine if patients attending for bariatric surgery have poor sleep independent of OSA status. MATERIALS AND METHODS: Sleep duration and quality, using the Pittsburgh Sleep Quality Index (PSQI), was analysed in 203 patients undergoing bariatric surgery between June 2016 and May 2019 in a single centre. Anthropometric data on all patients were recorded as well as presence of OSA and PAP usage. RESULTS: The bariatric population reported an average (standard deviation) sleep duration of 6.5 (1.6) h, and 67.9% of patients had a documented poor sleep quality (PSQI>5). The presence of OSA did not significantly influence either sleep duration (p=0.23) or sleep quality (p=0.5). On logistic regression, there was no significant relationship between sleep duration or sleep quality and the following variables: age, sex, and AHI. There was however a significant association between BMI and sleep quality (p= 0.007). PSQI was inversely associated with BMI. This equated to 1 kg/m2 weight gain being associated with 0.097 decrease in PSQI score. CONCLUSIONS: The presence of OSA does not influence either sleep duration or sleep quality in the bariatric surgical population. This suggests that clinically severe obesity itself may cause poor sleep.

How Relevant Is Pre-operative Obstructive Sleep Apnoea in the Asymptomatic Bariatric Surgery Patient?

INTRODUCTION: The American Academy of Sleep Medicine recommends patients attending for bariatric surgery (BS) to be evaluated for obstructive sleep apnoea (OSA) as untreated OSA is associated with a greater risk of post-operative complications. Not all bariatric patients have symptoms of OSA and their phenotype may be at less risk than the typical sleep clinic phenotype. Therefore, all patients may not require pre-operative sleep studies. This study aimed to establish whether screened and unscreened BS patients are at increased risk of post-operative complications. METHODS: A retrospective review of BS patients at a single centre, June 2008-May 2017. Demographic data, sleep study outcomes, post-operative complications, length of stay (LOS), intensive care unit (ICU) admission, and readmission rates were reviewed. RESULTS: A total of 510 patients underwent gastric bypass, sleeve gastrectomy, or gastric banding. 385/510 (75.5%) were female. Mean age was 46 ± 11.27 years, mean BMI was 49 kg/m2 ± 7.42. OSA was diagnosed in 300/510 (58.8%) and normal sleep in 57/510 (11.2%). OSA was not associated with increased post-operative complications. No significant difference between screened and unscreened patients for the development of post-operative pulmonary or cardiac complications, (p = 0.607, p = 0.827, respectively). Increasing age was a predictor for pulmonary (p = 0.011) and cardiac (p = 0.018) complications. CONCLUSION: OSA is very prevalent in morbidly obese patients. The lack of association between patients diagnosed with OSA and unscreened patients, and post-operative complications suggests that not all patients require pre-operative sleep studies. Further studies may help identify which patients can safely avoid OSA screening.

Influence of glass wool as separator on bioelectricity generation in a constructed wetland-microbial fuel cell.

To figure out the impact of the separator on the electrical performance of the newly established constructed wetland-microbial fuel cell (CW-MFC), two parallel upflow CW-MFC systems, with and without glass wool (GW), were set up in this study. System performances in terms of bioelectricity production were monitored for more than 4 months. Results showed that the highest voltage was achieved in non-separator (NS) system (465.7 ± 4.2 mV with electrode spacing of 5 cm), which is 48.9% higher than the highest value generated in GW system (312 ± 7.0 mV with electrode spacing of 2 cm). The highest power density was produced in NS system (66.22 mW/m2), which is 3.9 times higher than the value in GW system (17.14 mW/m2). The diffusion of oxygen from the open air was greatly hindered by the biofilm formed under the cathode. This kind of biofilm can be severed as the "microbial separator", playing the same role in a real separator.

Constructed wetland integrated microbial fuel cell system: looking back, moving forward.

In the last 10 years, the microbial fuel cell (MFC) has been extensively studied worldwide to extract energy from wastewater via electricity generation. More recently, a merged technique of embedding MFC into a constructed wetland (CW) has been developed and appears to be increasingly investigated. The driving force to integrate these two technologies lies in the fact that CWs naturally possess a redox gradient (depending on flow direction and wetland depth), which is required by MFCs as anaerobic anode and aerobic cathode chambers. No doubt, the integration of MFC with a CW will upgrade the CW to allow it to be used for wastewater treatment and, simultaneously, electricity generation, making CWs more sustainable and environmentally friendly. Currently, published work shows that India, China, Ireland, Spain, Germany and Malaysia are involved in the development of this technology although it is in its infant stage and many technical issues are faced on system configuration, operation and maximisation of electricity production. This paper aims to provide an updated review and analysis of the CW-MFC development. Focuses are placed on the experience gained so far from different researchers in the literature and further research directions and proposals are discussed in great detail.

Promoting the bio-cathode formation of a constructed wetland-microbial fuel cell by using powder activated carbon modified alum sludge in anode chamber.

MFC centered hybrid technologies have attracted attention during the last few years due to their compatibility and dual advantages of energy recovery and wastewater treatment. In this study, a MFC was integrated into a dewatered alum sludge (DAS)- based vertical upflow constructed wetland (CW). Powder activate carbon (PAC) was used in the anode area in varied percentage with DAS to explore its influences on the performance of the CW-MFC system. The trial has demonstrated that the inclusion of PAC improved the removal efficiencies of COD, TN and RP. More significantly, increasing the proportion of PAC from 2% to 10% can significantly enhance the maximum power densities from 36.58 mW/m(2) to 87.79 mW/m(2). The induced favorable environment for bio-cathode formation might be the main reason for this improvement since the content of total extracellular polymeric substances (TEPS) of the substrate in the cathode area almost doubled (from 44.59 µg/g wet sludge to 87.70 µg/g wet sludge) as the percentage of PAC increased to 10%. This work provides another potential usage of PAC in CW-MFCs with a higher wastewater treatment efficiency and energy recovery.

A review of a recently emerged technology: Constructed wetland--Microbial fuel cells.

Constructed wetlands (CWs) and microbial fuel cells (MFCs) are compatible technologies since both are reliant on the actions of bacteria to remove contaminants from wastewater. MFCs require the anode to remain anaerobic with the cathode exposed to oxygen while these redox conditions can develop naturally in CWs. For this reason, research into combining the two technologies (termed as CW-MFC) has emerged in recent years with the aim of improving the wastewater treatment capacity of wetlands while simultaneously producing electrical power. Based on the published work (although limited), this review aims to provide a timely, current state-of-the-art in CW-MFC while exploring future challenges and research directions.

Operating a two-stage microbial fuel cell-constructed wetland for fuller wastewater treatment and more efficient electricity generation.

By integrating microbial fuel cells (MFCs) into constructed wetlands (CWs) the need and cost of building a reactor are eliminated, while CWs provide the simultaneous redox conditions required for optimum MFC performance. Two single-stage MFC-CWs, with dewatered alum sludge cake as the main wetland medium for enhanced phosphorus removal, were operated to determine the effects of electrode separation and flow regimes on power production and wastewater treatment. When the anode is buried and the cathode is at the air-water interface the system is inhibited by a large ohmic resistance resulting from the increased electrode separation. By placing the cathode directly above the anode and operating the system with simultaneous up-flow into the anode and down-flow into the cathode the ohmic resistance is reduced. The chemical oxygen demand (COD) removal efficiency was, however, reduced to 64% (compared with 79%). A two-stage system was subsequently run for fuller wastewater treatment and increased power production. The results indicate that a two-stage MFC-CW can increase the normalized energy recovery and improve removal efficiencies of COD, total nitrogen, NH4⁺, total phosphorus and reactive phosphorus to 93 ± 1.7%, 85 ± 5.2%, 90 ± 5.4%, 98 ± 5.3% and 99 ± 2.9%, respectively.

Effects of salmeterol on sleeping oxygen saturation in chronic obstructive pulmonary disease.

BACKGROUND: Sleep is associated with important adverse effects in patients with chronic obstructive pulmonary disease (COPD), such as disturbed sleep quality and gas exchange, including hypoxemia and hypercapnia. The effects of inhaled long-acting beta(2)-agonist therapy (LABA) on these disturbances are unclear. OBJECTIVES: The aim of the study was to assess the effect of inhaled salmeterol on nocturnal sleeping arterial oxygen saturation (SaO(2)) and sleep quality. METHODS: In a randomized, double-blind, placebo-controlled, crossover study of moderate/severe stable COPD patients, we compared the effects of 4 weeks of treatment with salmeterol 50 microg b.d. and matching placebo on sleeping SaO(2) and sleep quality. Overnight polysomnography (PSG) was performed at baseline, and after 4 and 8 weeks in addition to detailed pulmonary function testing. Of 15 patients included, 12 completed the trial (median age 69 years, forced expiratory volume in 1 s, FEV(1): 39%). RESULTS: Both mean SaO(2) [salmeterol vs. placebo: 92.9% (91.2, 94.7) vs. 91.0% (88.9, 94.8); p = 0.016] and the percentage of sleep spent below 90% of SaO(2) [1.8% (0.0, 10.8) vs. 25.6% (0.5, 53.5); p = 0.005] improved significantly with salmeterol. Sleep quality was similar with both salmeterol and placebo on PSG. Static lung volumes, particularly trapped gas volume, tended to improve with salmeterol. CONCLUSION: We conclude that inhaled LABA therapy improves sleeping SaO(2) without significant change in sleep quality.

Effects of heated humidification and topical steroids on compliance, nasal symptoms, and quality of life in patients with obstructive sleep apnea syndrome using nasal continuous positive airway pressure.

BACKGROUND: Nasal side effects are common in patients with obstructive sleep apnea syndrome (OSAS) starting on nasal continuous positive airway pressure (CPAP) therapy. We tested the hypothesis that heated humidification or nasal topical steroids improve compliance, nasal side effects and quality of life in this patient group. METHODS: 125 patients with the established diagnosis of OSAS (apnea/hypopnea index > or = 10/h), who tolerated CPAP via a nasal mask, and who had a successful CPAP titration were randomized to 4 weeks of dry CPAP, humidified CPAP or CPAP with additional topical nasal steroid application (fluticasone, GlaxoWellcome). Groups were similar in all demographic variables and in frequency of nasal symptoms at baseline. Outcome measures were objective compliance, quality of life (short form 36), subjective sleepiness (Epworth Sleepiness Scale score) and nasal symptoms such as runny, dry or blocked nose, sneezing and headaches; all variables assessed using a validated questionnaire and by direct interview. RESULTS: There was no difference in compliance between groups after 4 weeks (dry: 5.21 +/- 1.66 h/night, fluticasone: 5.66 +/- 1.68, humidifier: 5.21 +/- 1.84; p = 0.444). Quality of life and subjective sleepiness improved in all groups, but there were no differences in the extent of improvement. Nasal Symptoms were less frequently reported in the humidifier group (28%) than in the remaining groups (dry: 70%, fluticasone: 53%, p = 0.002). However, the addition of fluticasone resulted in increased frequency of sneezing. CONCLUSION: The addition of a humidifier, but not nasal steroids decreases the frequency of nasal symptoms in unselected OSAS patients initiating CPAP therapy; however compliance and quality of life remain unaltered.

Electrocardiogram recording as a screening tool for sleep disordered breathing.

STUDY OBJECTIVES: Transient changes in heart rate associated with obstructive apneas have been suggested for screening of sleep disordered breathing (SDB). This study prospectively compares the outcomes of an automated ECG-based SDB screening tool with simultaneous polysomnography. METHODS: The previously-developed automated algorithm was applied to a single channel ECG obtained during standard overnight polysomnography (92 subjects) to obtain an apnea-hypopnea index (AHI) estimate. Using AHI thresholds of < 5 and > or =15 to define absence and presence of SDB, respectively, we determined the likelihood ratios of the proposed technique. RESULTS: The automated algorithm achieved positive and negative likelihood ratios of 2.16 and 0.08. Estimated and reference AHI were highly correlated (r = 0.88). Pathologically insignificant arrhythmia in some subjects had no discernible impact on the algorithm. CONCLUSIONS: ECG-based assessment provides a simple but limited means of recognizing subjects with obstructive sleep apnea.

The human genioglossus response to negative airway pressure: stimulus timing and route of delivery.

The genioglossus reflex response to sudden onset pulses of negative airway pressure (NAP) in humans is reported to occur more commonly at end rather than onset of expiration when delivered via a mouthpiece. We examined whether this response was modulated by the route of stimulus delivery throughout the respiratory cycle. The genioglossus surface EMG (GGsEMG) response to NAP delivered randomly throughout the respiratory cycle was measured in a set of experiments: (i) 40 stimuli of NAP at -5, -7.5 and -10 cmH2O applied to eight healthy, awake, supine males via nose-mask; and (ii) 60 stimuli of -7.5 cmH2O NAP applied to 15 subjects via both nose-mask and mouthpiece in random order. Despite similar pressure changes being detected in the epiglottis during both routes of stimulus delivery, far lower pressure changes were measured at the nasal choanae during mouthpiece compared with nose-mask delivery. There were no significant differences between the responses during any phase of respiration, nor when NAP was delivered via nose-mask or mouthpiece. We conclude that the sensitivity of the GGsEMG response to NAP in humans does not vary significantly with phase of respiration or route of breathing.

Improved surface EMG electrode for measuring genioglossus muscle activity.

Activation of the genioglossus (GG) muscles is necessary to maintain the patency of the upper airway. In the condition of obstructive sleep apnea (OSA) this mechanism fails and the possible role of fatigue in its pathogenesis is still not fully understood. In this paper, a new electrode design for recording the genioglossus surface electromyogram (sEMG) is presented. The new design differs from a widely used GG surface electrode in both electrode configuration (unilateral rather than bilateral) and electrode material (Ag-AgCl rather than stainless steel (SS)). The separate effects of these factors were evaluated during force-varying and fatiguing contractions on normal human subjects and using GG sEMG model simulations. Unilateral sEMG was found to have lower amplitude, lower frequency content and a different rate of change of median frequency during fatiguing contractions. It was shown to overcome several disadvantages posed by the bilateral configuration and be more selective. Ag-AgCl has more favorable impedance characteristics and resulted in greater signal amplitudes. It was concluded that the new design is more suitable for detecting GG sEMG and allows more reliable interpretation of changes in sEMG due to physiological mechanisms, thus providing a new methodology for studying GG function and the role of fatigue in OSA.

Auto-adjusting versus fixed positive pressure therapy in mild to moderate obstructive sleep apnoea.

STUDY OBJECTIVES: To determine if auto-adjusting positive airway pressure (APAP) would be better tolerated on the basis of delivering a lower mean pressure in patients with mild to moderate obstructive sleep apnoea syndrome (OSAS). DESIGN: Patients spent 8 weeks on continuous positive airway pressure (CPAP) and 8 weeks on APAP in a randomized crossover design. SETTING: Respiratory Sleep Disorders Unit in a University Hospital and the patient's home. PARTICIPANTS: Twenty-nine patients with newly diagnosed mild to moderate OSAS (apnoea-hypopnoea frequency of 5-30 events/hour) were studied. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Overnight polysomnography and Epworth Sleepiness Scale were recorded at baseline and at the end of each treatment period in addition to patient preference for device, side effects, and objective compliance. No differences were found in polysomnographic variables or Epworth Sleepiness Scale scores between the 2 treatment modes, but all variables were significantly improved from baseline values. Mean APAP pressure levels were significantly lower than CPAP (6.3 +/- 1.4 vs 8.1 +/- 1.7 cm H2O, p < .001). Patient compliance was similar with both treatments. More patients requiring higher fixed pressure (> or = 8cm H2O) preferred APAP, whereas those requiring lower pressure (< 8 cm H2O) preferred CPAP (p = .03). Follow-up after 18 months of therapy indicated that 76% of subjects continued to be compliant, with a nightly use of 5.8 +/- 1.9 hours per night, despite high levels of minor side effects. CONCLUSIONS: APAP and CPAP are equally effective in managing patients with mild to moderate OSAS, but device preference may be influenced by fixed pressure requirements.

Long-term effects of nasal continuous positive airway pressure therapy on cardiovascular outcomes in sleep apnea syndrome.

BACKGROUND: Obstructive sleep apnea syndrome (OSAS) has been associated with increased morbidity and mortality, principally from cardiovascular disease, but the impact of nasal continuous positive airway pressure (CPAP) therapy is unclear. METHODS: We performed a long-term follow-up study of 168 patients with OSAS who had begun receiving CPAP therapy at least 5 years previously, most of whom had been prospectively followed up, having been the subject of an earlier report on cardiovascular risk factors in OSAS patients. The average follow-up period was 7.5 years. We compared the cardiovascular outcomes of those patients who were intolerant of CPAP (untreated group, 61 patients) with those continuing CPAP therapy (107 patients). RESULTS: CPAP-treated patients had a higher median apnea-hypopnea index score than the untreated group (48.3 [interquartile range (IQR), 33.6 to 66.4] vs 36.7 [IQR, 27.4 to 55], respectively; p = 0.02), but age, body mass index, and time since diagnosis were similar. Deaths from cardiovascular disease were more common in the untreated group than in the CPAP-treated group during follow-up (14.8% vs 1.9%, respectively; p = 0.009 [log rank test]), but no significant differences were found in the development of new cases of hypertension, cardiac disorder, or stroke. Total cardiovascular events (ie, death and new cardiovascular disease combined) were more common in the untreated group than in the CPAP-treated group (31% vs 18%, respectively; p < 0.05). CONCLUSIONS: The data support a protective effect of CPAP therapy against death from cardiovascular disease in patients with OSAS.

Effects of topical anesthesia on upper airway resistance during wake-sleep transitions.

Deformation of the upper airway (UA) by negative transmural pressure alters the activity of UA mechanoreceptors, causing a reflex increase in UA muscle activity. Topical anesthesia of the UA mucosa, which greatly reduces this reflex response, causes an increase in UA resistance during stage 2 sleep. We hypothesized that topical anesthesia of the UA mucosa would predispose to UA instability at sleep onset and, therefore, examined the effect of UA anesthesia on pharyngeal resistance (Rph) in stage 1 sleep. Eleven normal, healthy volunteers were instrumented to record standard polysomnographic variables, respiratory airflow, and UA pressure at the nasal choanae and the epiglottis. Subjects were permitted to sleep until stable stage 2 sleep was reached and were then awoken. This procedure was repeated three times to obtain reproducible wake-sleep transitions. The UA mucosa was then anesthetized with 10% lidocaine to the oropharynx and laryngopharynx, and the pharyngeal mechanics were studied during the subsequent wake-sleep transition. Three subjects were excluded because of failure to resume sleep postanesthesia. Rph was significantly higher after anesthesia during stage 1 sleep [2.88 +/- 0.77 cmH(2)O.l(-1).s (mean +/- SE)] compared with control (0.95 +/- 0.35 cmH(2)O.l(-1).s; P < 0.05), but there was no difference during wakefulness. Furthermore, there was a significant rise in Rph at wake-to-sleep transitions and a significant fall in Rph at sleep-to-wake transitions after anesthesia (P < 0.05) but not in the control condition. We conclude that sensory receptors in the UA mucosa contribute to the maintenance of UA patency at wake-sleep transition in normal humans.

Impact of nasal continuous positive airway pressure therapy on the quality of life of bed partners of patients with obstructive sleep apnea syndrome.

BACKGROUND: Continuous positive airway pressure (CPAP) improves daytime sleepiness and quality of life in patients with obstructive sleep apnea syndrome (OSAS). However, few studies have examined the impact of treatment on the quality of life of bed partners of these patients. METHODS: We prospectively studied 55 couples in which one person (the patient) had OSAS diagnosed and was subsequently commenced on CPAP therapy; 45 of these couples shared a bed on a regular basis. Both partner and patient completed postal questionnaires immediately prior to CPAP therapy and again after a median of 8 weeks (interquartile range [IQR], 6 to 12 weeks) of therapy at home. Questionnaires consisted of the Epworth sleepiness scale (ESS), the UK Short Form-36 health survey, and the hospital anxiety and depression scale. No intervention or advice was given to the partner of the patient receiving CPAP therapy. RESULTS: In addition to the expected significant benefits reported by patients receiving CPAP, bed partners also reported significant improvements in ESS scores (median, 4 [IQR, 1 to 8.5] before CPAP; median, 2 [IQR, 1 to 5] during CPAP), in addition to measures of anxiety, role limitation due to physical problems, role limitation due to emotional problems, social functioning, mental health, and energy/vitality (all p < 0.05 by Wilcoxon-signed rank testing). CONCLUSIONS: These data support the hypothesis that partners of patients with OSAS benefit significantly from the CPAP therapy their bed partners receive.