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Background Severe obesity causes respiratory morbidity and mortality. The impact of obesity on the mechanics of breathing is not fully understood. Patients and methods We undertook a comprehensive observational study of lung volumes and elasticity in nine obese and nine normal weight subjects, seated and supine, during spontaneous breathing. Seated and supine total lung capacity (TLC) and subdivisions were measured by multibreath helium dilution method. Using balloon catheters, oesophageal (Poes) and gastric (Pgas) pressures were recorded. Transpulmonary pressure (PL) was calculated as mouth pressure (Pmouth)-Poes, and complete expiratory PL volume curves were measured. Results The obese group had a body mass index (BMI) of 46.8 (17.2) kg/m2, and the normal group had a BMI of 23.2 (1.6) kg/m2 (p=0.001). Obese and normals were matched for age (p=0.233), gender (p=0.637) and height (p=0.094). The obese were more restricted than the normals (TLC 88.6 (16.9) vs 104.4 (12.3) %predicted, p=0.033; FEV1/FVC 79.6 (7.3) vs 82.5 (4.2) %, p=0.325), had dramatically reduced expiratory reserve volume (ERV 0.4 (0.4) vs 1.7 (0.6) L, p<0.001) and end-tidal functional residual capacity (FRC) was smaller (37.5 (6.9) vs 46.9 (4.6) %TLC, p=0.004) when seated, but was similar when supine (39.4 (7.7) vs 41.5 (4.3) %TLC, p=0.477). Gastric pressures at FRC were significantly elevated in the obese (seated 19.1 (4.7) vs 12.1 (6.2) cm H2O, p=0.015; supine 14.3 (5.7) vs 7.1 (2.6) cm H2O, p=0.003), as were end-expiratory oesophageal pressures at FRC (seated 5.2 (6.9) vs −2.0 (3.5) cm H2O, p=0.013; supine 14.0 (8.0) vs 5.4 (3.1) cm H2O, p=0.008). BMI correlated with end-expiratory gastric (seated R2=0.43, supine R2=0.66, p<0.01) and oesophageal pressures (seated R2=0.51, supine R2=0.62, p<0.01). Conclusions Obese subjects have markedly increased gastric and oesophageal pressures, both when upright and supine, causing dramatically reduced FRC and ERV, which increases work of breathing.

Postural fluid shifts may directly affect respiratory control via a complex interaction of baro‐ and chemo‐reflexes, and cerebral blood flow. Few data exist concerning the steady state ventilatory responses during head‐down tilt. We examined the cardiorespiratory responses during acute 50° head‐down tilt (HDT) in 18 healthy subjects (mean [SD] age 27 [10] years). Protocol 1 (n = 8, two female) was 50° HDT from 60° head‐up posture sustained for 10 min, while exposed to normoxia, normoxic hypercapnia (5% CO2), hypoxia (12% inspired O2) or hyperoxic hypercapnia (95% O2, 5% CO2). Protocol 2 (n = 10, four female) was 50° HDT from supine, sustained for 10 min, while breathing either medical air or normoxic hypercapnic (5% CO2) gas. Ventilation (V̇E ${{\\dot{V}}_E}$ , pneumotachograph), end‐tidal O2 and CO2 concentration and blood pressure (Finapres) were measured continuously throughout each protocol. Middle cerebral artery blood flow velocity (MCAv; transcranial Doppler) was also measured during protocol 2. Ventilation increased significantly (P < 0.05) compared to baseline during HDT in both hyperoxic hypercapnia (protocol 1 by mean [SD] 139 [26]%) and normoxic hypercapnia (protocol 1 by mean [SD] 131 [21]% and protocol 2 by 129 [23]%), despite no change in PETCO2 ${{P}_{{\\mathrm{ETC}}{{{\\mathrm{O}}}_2}}}$or PETO2 ${{P}_{{\\mathrm{ET}}{{{\\mathrm{O}}}_2}}}$from baseline. No change in V̇E ${{\\dot{V}}_E}$was observed during HDT with medical air or hypoxia, and there was no significant change in MCAv during HDT compared to baseline. The absence of change in cerebral blood flow leads us to postulate that the augmented ventilatory response during steep HDT may involve mechanisms related to cerebral venous pressure and venous outflow. What is the central question of this study? Postural fluid shifts affect respiratory control via complex interactions between baroreceptor and chemoreceptor reflexes, and cerebral blood flow. Few data exist concerning steady state ventilatory responses during head down tilt. What is the main finding and its importance? Acute 50° head‐down tilt augments the ventilatory response to steady state normoxic and hyperoxic hypercapnia possibly via mechanisms involving cerebral blood flow. These findings are relevant clinically during procedures performed in a steep head‐down position and microgravity environments where individuals are exposed to fluid shifts and elevated atmospheric CO2.

Continuous positive airway pressure (CPAP) is the first-line treatment for the majority of patients affected by obstructive sleep apnea syndrome (OSA). However, long-term compliance with CPAP therapy may result limited and alternatives to CPAP therapy are required to address the increasing need to provide tailored therapeutic options. Understanding the pathophysiological traits (PTs) of OSA patients [upper airway (UA) anatomical collapsibility, loop gain (LG), arousal threshold (AT), and UA gain (UAG)] lies at the heart of the customized OSA treatment. However, sleep research laboratories capable to phenotype OSA patients are sparse and the diagnostic procedures time-consuming, costly, and requiring significant expertise. The question arises whether the use of routine clinical polysomnography or nocturnal portable multi-channel monitoring (PSG/PM) can provide sufficient information to characterize the above traits. The aim of the present review is to deduce if the information obtainable from the clinical PSG/PM analysis, independently of the scope and context of the original studies, is clinically useful to define qualitatively the PTs of individual OSA patients. In summary, it is possible to identify four patterns using PSG/PM that are consistent with an altered UA collapsibility, three that are consistent with altered LG, two with altered AT, and three consistent with flow limitation/UA muscle response. Furthermore, some PSG/PM indexes and patterns, useful for the suitable management of OSA patient, have been discussed. The delivery of this clinical approach to phenotype pathophysiological traits will allow patients to benefit in a wider range of sleep services by facilitating tailored therapeutic options.

BackgroundExacerbations of chronic obstructive pulmonary disease (COPD) are characterised by increased dyspnoea, reduced quality of life and muscle weakness. Re-exacerbation and hospital admission are common. Pulmonary rehabilitation (PR) administered after hospital admission for an exacerbation can improve quality of life and exercise capacity.ObjectiveTo determine whether outpatient post-exacerbation PR (PEPR) could reduce subsequent hospital admission episodes.MethodsPatients admitted to hospital for an exacerbation of COPD were randomised to receive either usual follow-up care (UC) or PEPR after discharge. Hospital admission and emergency department attendances for COPD exacerbations were recorded over a 3-month period and analysed on an intention-to-treat basis. Secondary outcomes included exercise capacity and quadriceps strength.Results60 patients underwent concealed randomisation at the time of their hospital discharge (UC: n=30, mean (SD) age 65 (10) years, forced expiratory volume in 1 s (FEV1) 52 (22)% predicted; PEPR: n=30, 67(10) years, 52 (20)% predicted). The proportion of patients re-admitted to hospital with an exacerbation was 33% in the UC group compared with 7% in those receiving PEPR (OR 0.15, 95% CI 0.03 to 0.72, p=0.02). The proportion of patients that experienced an exacerbation resulting in an unplanned hospital attendance (either admission or review and discharge from the emergency department) was 57% in the UC group and 27% in those receiving PEPR (OR 0.28, 95% CI 0.10 to 0.82, p=0.02).ConclusionsPost-exacerbation rehabilitation in COPD can reduce re-exacerbation events that require admission or hospital attendance over a 3-month period.Clinical Trials Registration NumberNCT00557115.

PurposeElectrical stimulation of the upper airway dilator muscles is an emerging treatment for obstructive sleep apnea (OSA). Invasive hypoglossal nerve stimulation (HNS) has been accepted as treatment alternative to continuous positive airway pressure (CPAP) for selected patients, while transcutaneous electrical stimulation (TES) of the upper airway is being investigated as non-invasive alternative.MethodsA meta-analysis (CRD42017074674) on the effects of both HNS and TES on the apnea-hypopnea index (AHI) and the Epworth Sleepiness Scale (ESS) in OSA was conducted including published evidence up to May 2018. Random-effects models were used. Heterogeneity and between-study variance were assessed by I2 and τ2, respectively.ResultsOf 41 identified clinical trials, 20 interventional trials (n = 895) could be pooled in a meta-analysis (15 HNS [n = 808], 5 TES [n = 87]). Middle-aged (mean ± SD 56.9 ± 5.5 years) and overweight (body mass index 29.1 ± 1.5 kg/m2) patients with severe OSA (AHI 37.5 ± 7.0/h) were followed-up for 6.9 ± 4.0 months (HNS) and 0.2 ± 0.4 months (TES), respectively. The AHI improved by − 24.9 h−1 [95%CI − 28.5, − 21.2] in HNS (χ2 79%, I2 82%) and by − 16.5 h−1 [95%CI − 25.1, − 7.8] in TES (χ2 7%, I2 43%; both p < 0.001). The ESS was reduced by − 5.0 (95%CI − 5.9, − 4.1) (p < 0.001).ConclusionBoth invasive and transcutaneous electrical stimulation reduce OSA severity by a clinically relevant margin. HNS results in a clinically relevant improvement of symptoms. While HNS represents an invasive treatment for selected patients with moderate to severe OSA, TES should be further investigated as potential non-invasive approach for OSA.

Many patients with obstructive sleep apnoea (OSA) remain undiagnosed and thus untreated, and in part this relates to delay in diagnosis. Novel diagnostic strategies may improve access to diagnosis. In a multicentre, randomised study, we evaluated time to treatment decision in patients referred for suspected OSA, comparing a mandibular movement (MM) monitor to respiratory polygraphy, the most commonly used OSA detection method in the UK. Adults with high pre-test probability OSA were recruited from both northern Scotland and London. 40 participants (70 % male, mean±SD age 46.8 ± 12.9 years, BMI 36.9 ± 7.5 kg/m2, ESS 14.9 ± 4.1) wore a MM monitor and respiratory polygraphy simultaneously overnight and were randomised (1:1) to receive their treatment decision based on results from either device. Compared to respiratory polygraphy, MM monitor reduced time to treatment decision by 6 days (median(IQR): 13.5 (7.0–21.5) vs. 19.5 (13.7–35.5) days, P = 0.017) and saved an estimated 29 min of staff time per patient.

The presence of visual imagery in dreams of congenitally blind people has long been a matter of substantial controversy. We set to systematically review body of published work on the presence and nature of oneiric visuo-spatial impressions in congenitally and early blind subjects across different areas of research, from experimental psychology, functional neuroimaging, sensory substitution, and sleep research. Relevant studies were identified using the following databases: EMBASE, MEDLINE and PsychINFO. Studies using diverse imaging techniques and sensory substitution devices broadly suggest that the \"blind\" occipital cortex may be able to integrate non-visual sensory inputs, and thus possibly also generate visuo-spatial impressions. Visual impressions have also been reported by blind subjects who had near-death or out-of-body experiences. Deciphering the mechanistic nature of these visual impression could open new possibility in utilization of neuroplasticity and its potential role for treatment of neurodisability.

Excessive dynamic airway collapse (EDAC) is characterized by abnormal airway collapse during expiration, leading to symptoms such as breathlessness, cough, and reduced quality of life. Treatment options remain limited, and evidence-based guidelines are lacking. This prospective cohort study evaluated the impact of positive airway pressure (PAP) therapy on symptom burden in 23 patients with EDAC referred to a tertiary ventilation centre. Diagnosis was confirmed by computed tomography and/or bronchoscopy. Patients received nocturnal and ambulatory PAP, with symptom ratings and quality of life assessed at baseline and after three months. PAP therapy produced rapid and sustained improvements in breathlessness, orthopnoea, cough frequency, sleep quality, and quality of life, with significant differences in all domains (p < 0.01). Adherence to nocturnal PAP was high. These findings suggest that PAP therapy is an effective symptomatic intervention in EDAC and support consideration of EDAC as an indication for PAP therapy in future clinical guidelines.

IntroductionJust under half of patients with obstructive sleep apnoea (OSA) also have gastro-oesophageal reflux disease (GORD). These conditions appear to be inter-related and continual positive airway pressure (CPAP) therapy, the gold standard treatment for OSA to prevent airway collapse, has been shown to reduce GORD. As the impact of mandibular advancement devices, a second-line therapy for OSA, on GORD has yet to be investigated, a feasibility study is needed prior to a definitive trial.MethodsThis will be a single-centre, single-blinded, tertiary-care based, interdisciplinary, parallel randomised controlled study. Potential OSA participants presenting to the sleep department will be pre-screened for GORD using validated questionnaires, consented and invited to receive simultaneous home sleep and oesophageal pH monitoring. Those with confirmed OSA and GORD (n=44) will be randomly allocated to receive either CPAP (n=22) or MAD therapy (n=22). Following successful titration and 3 weeks customisation period, participants will repeat the simultaneous sleep and oesophageal pH monitoring while wearing the device. The number of patients screened for recruitment, drop-out rates, patient feedback of the study protocol, costs of interventions and clinical information to inform a definitive study design will be investigated.Ethics and disseminationHealth Research Authority approval has been obtained from the Nottingham 2 Research Ethics Committee, ref:22/EM/0157 and the trial has been registered on ISRCTN (https://doi.org/10.1186/ISRCTN16013232). Definitive findings about the feasibility of doing 24 hour pH oesophageal monitoring while doing a home sleep study will be disseminated via clinical and research networks facilitating valuable insights into the simultaneous management of both conditions.Trial registration numberISRCTN Reg No: 16013232.

IntroductionObstructive Sleep Apnoea (OSA) is commonly treated with Continuous Positive Airway Pressure (CPAP) therapy. Over the last decade, hypoglossal nerve stimulation in OSA has been tested in randomised controlled trials (RCT) to maintain the neuromuscular tone of the genioglossus muscle and treat OSA. We sought to analyse the qualitative feedback of patients who were included in an RCT using transcutaneous electrical stimulation (TESLA-home) for three months. Method & PatientsWe analysed the feedback of patients included in the TESLA-home trial (NCT03160456, 2018–2023) undertaken at Guy’s & St Thomas’ Hospital, London following patients for 3 months. The intervention arm received domiciliary TESLA, while the control arm received usual care (CPAP). Patients with OSA (apnoea-hypopnoea index 5–35/hour) who failed effective CPAP usage (<4 hours/night) were included. This is an interim analysis on 46/56 patients. ResultsThe trial randomised 56 randomised patients, 29 patients into the intervention arm (TESLA), while 27 patients were assigned to usual care (CPAP). In total, this interim analysis included exit interview feedback from 46 patients. 89% (41) of patients reported no skin discomfort, the rest had mild skin discomfort; some patients experienced improved headaches, while one patient discontinued the intervention (TESLA) due to mild headaches. Out of the entire group, 59% (27) of patients reported dryness of the mouth (both trial arms). 67% (31) of the patients reported limited sleep quality as well as not feeling refreshed (both trial arms), caused by either being non-responders to TESLA or non-adherence to CPAP. DiscussionTESLA is well tolerated but may cause mild skin sensation and mild headaches in some patients. Other related issues (dry mouth, sleep quality) match the problems experienced with usual care (CPAP).