Effects of non-invasive ventilation on sleep in chronic hypercapnic respiratory failure.

Chronic respiratory disease can exacerbate the normal physiological changes in ventilation observed in healthy individuals during sleep, leading to sleep-disordered breathing, nocturnal hypoventilation, sleep disruption and chronic respiratory failure. Therefore, patients with obesity, slowly and rapidly progressive neuromuscular disease and chronic obstructive airways disease report poor sleep quality. Non-invasive ventilation (NIV) is a complex intervention used to treat sleep-disordered breathing and nocturnal hypoventilation with overnight physiological studies demonstrating improvement in sleep-disordered breathing and nocturnal hypoventilation, and clinical trials demonstrating improved outcomes for patients. However, the impact on subjective and objective sleep quality is dependent on the tools used to measure sleep quality and the patient population. As home NIV becomes more commonly used, there is a need to conduct studies focused on sleep quality, and the relationship between sleep quality and health-related quality of life, in all patient groups, in order to allow the clinician to provide clear patient-centred information.

Treatment of obstructive sleep apnea with a simple CPAP device.

PURPOSE: CPAP is the "gold standard" treatment for obstructive sleep apnea (OSA). Current CPAP models have developed additional functions including automatic CPAP and pressure relief. However, CPAP adherence has not improved over the last three decades. Many patients in low-income countries cannot afford these CPAP devices. A novel simple CPAP device with a fixed pressure without pressure controller was developed. METHODS: Manual CPAP pressure titration was performed in 127 patients with OSA. Six patients with a titration pressure higher than 11 cmH2O and 14 patients who could not tolerate CPAP were excluded, leaving 107 participating in the following 2 studies. In study one, 54 of 107 patients were treated by both conventional fixed CPAP and simple CPAP in random order. In the second study, another 53 patients were treated by both autoCPAP in automatic function and simple CPAP in random order. Simple CPAP was fixed at 10 cmH2O, 8 cmH2O, and 6 cmH2O for patients whose titration pressure was between 9-10, 7-8, and ≤ 6 cmH2O, respectively. Conventional fixed CPAP device was set exactly the same as manual titration pressure. RESULTS: All patients whose manual titration pressure ≤ 10 cmH2O were effectively treated by simple CPAP (AHI 40.7 ± 2.3 events/h before vs 2.5 ± 0.3 events/h after, p < 0.001). Patients expressed similar preferences for simple CPAP, autoCPAP, and conventional fixed CPAP (p > 0.05). CONCLUSIONS: We conclude that a novel simple CPAP is an alternative treatment for most patients with OSA, which may widen access to CPAP therapy in the developing countries because of its low cost.

COVID-19-related changes in outpatient CPAP setup pathways for OSA are linked with decreased 30-day CPAP usage.

The COVID-19 pandemic changed continuous positive airway pressure (CPAP) setup pathways. We evaluated patients commenced on CPAP in 2019 (prepandemic) and 2020 (post-first UK wave). Face-to-face (F2F) setup numbers, with CPAP turned on, decreased from 613 patients (98.9%) in 2019, to 6 (1.1%) in 2020. In 2020, setups were F2F without CPAP turned on (403 (71.1%)), or remote (158 (27.9%)). Prepandemic median CPAP usage at first follow-up was 5.4 (2.7-6.9) hours/night and fell by 0.9 hours/night (95% CI 0.5 to 1.2, p<0.0001) in 2020. We found clinically relevant reductions in CPAP usage with pathway changes post-COVID-19.

Transcutaneous electrical stimulation in obstructive sleep apnoea: current developments and concepts of the TESLA-home programme.

PURPOSE OF REVIEW: Obstructive sleep apnoea (OSA) is a highly prevalent condition affecting about 1 billion people worldwide. The first line therapy for most patients with OSA is continuous positive airway pressure (CPAP) therapy. However, there are significant limitations with long-term adherence to CPAP therapy, which may be as low as 30-60%. RECENT FINDING: Electrical stimulation of the hypoglossal nerve has been studied in recent years. It achieves upper airway patency by causing a contraction of the genioglossus muscle, the strongest dilator of the upper airway, and by maintaining its neuromuscular tone in the asleep patient with OSA. Electrical stimulation can be delivered invasively, hypoglossal nerve stimulation (HNS), and noninvasively, transcutaneous electrical stimulation in OSA (TESLA). However, randomised controlled trials, the STAR and the TESLA trial, have provided promising results on efficacy and safety of the methods. SUMMARY: Patient and public involvement underlines the interest in TESLA and HNS and highlights the need to provide non-CPAP therapeutic options to those who may find it difficult to cope with first line therapies. The relatively low costs and the favourable safety profile of the TESLA approach provide the chance to offer this treatment to patients with OSA following further development of the evidence.

Electrical stimulation as a therapeutic approach in obstructive sleep apnea - a meta-analysis.

PURPOSE: Electrical 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. METHODS: A 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. RESULTS: Of 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). CONCLUSION: Both 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.

Long-term survival following initiation of home non-invasive ventilation: a European study.

INTRODUCTION: Although home non-invasive ventilation (NIV) is increasingly used to manage patients with chronic ventilatory failure, there are limited data on the long-term outcome of these patients. Our aim was to report on home NIV populations and the long-term outcome from two European centres. METHODS: Cohort analysis including all patients established on home NIV from two European centres between 2008 and 2014. RESULTS: Home NIV was initiated in 1746 patients to treat chronic ventilatory failure caused by (1) obesity hypoventilation syndrome±obstructive sleep apnoea (OHS±OSA) (29.5%); (2) neuromuscular disease (NMD) (22.7%); and (3) obstructive airway diseases (OAD) (19.1%). Overall cohort median survival following NIV initiation was 6.6 years. Median survival varied by underlying aetiology of respiratory failure: rapidly progressive NMD 1.1 years, OAD 2.7 years, OHS±OSA >7 years and slowly progressive NMD >7 years. Multivariate analysis demonstrated higher mortality in patients with rapidly progressive NMD (HR 4.78, 95% CI 3.38 to 6.75), COPD (HR 2.25, 95% CI 1.64 to 3.10), age >60 years at initiation of home NIV (HR 2.41, 95% CI 1.92 to 3.02) and NIV initiation following an acute admission (HR 1.38, 95% CI 1.13 to 1.68). Factors associated with lower mortality were NIV adherence >4 hours per day (HR 0.64, 95% CI 0.51 to 0.79), OSA (HR 0.51, 95% CI 0.31 to 0.84) and female gender (HR 0.79, 95% CI 0.65 to 0.96). CONCLUSION: The mortality rate following initiation of home NIV is high but varies significantly according to underlying aetiology of respiratory failure. In patients with chronic respiratory failure, initiation of home NIV following an acute admission and low levels of NIV adherence are poor prognostic features and may be amenable to intervention.

Obstructive sleep apnoea treatment and blood pressure: which phenotypes predict a response? A systematic review and meta-analysis.

The treatment for obstructive sleep apnoea (OSA) with continuous positive airway pressure (CPAP) or mandibular advancement devices (MADs) is associated with blood pressure (BP) reduction; however, the overall effect is modest. The aim of this systematic review and meta-analysis of randomised controlled trials (RCTs) comparing the effect of such treatments on BP was to identify subgroups of patients who respond best to treatment.The article search was performed in three different databases with specific search terms and selection criteria. From 2289 articles, we included 68 RCTs that compared CPAP or MADs with either passive or active treatment. When all the studies were pooled together, CPAP and MADs were associated with a mean BP reduction of -2.09 (95% CI -2.78- -1.40) mmHg for systolic BP and -1.92 (95% CI -2.40- -1.43) mmHg for diastolic BP and -1.27 (95% CI -2.34- -0.20) mmHg for systolic BP and -1.11 (95% CI -1.82- -0.41) mmHg for diastolic BP, respectively. The subgroups of patients who showed a greater response were those aged <60 years (systolic BP -2.93 mmHg), with uncontrolled BP at baseline (systolic BP -4.14 mmHg) and with severe oxygen desaturations (minimum arterial oxygen saturation measured by pulse oximetry <77%) at baseline (24-h systolic BP -7.57 mmHg).Although this meta-analysis shows that the expected reduction of BP by CPAP/MADs is modest, it identifies specific characteristics that may predict a pronounced benefit from CPAP in terms of BP control. These findings should be interpreted with caution; however, they are particularly important in identifying potential phenotypes associated with BP reduction in patients treated for OSA.

BPAP is an effective second-line therapy for obese patients with OSA failing regular CPAP: A prospective observational cohort study.

BACKGROUND AND OBJECTIVE: Continuous positive airway pressure (CPAP) is the most common treatment for obstructive sleep apnoea (OSA), but many patients fail long-term therapy. Bilevel positive airway pressure (BPAP) is a potential alternative. We hypothesized that BPAP could improve treatment adherence and outcomes in patients who cannot tolerate CPAP. METHODS: Patients with OSA who failed CPAP (usage < 4 h/day) and were referred to a tertiary sleep centre between 2014 and 2017 for BPAP were included. Age, gender, body mass index (BMI), co-morbidities, CPAP use and reasons for failure, Epworth Sleepiness Scale (ESS), sleep study data, spirometry data and average maximum nightly compliance were recorded. RESULTS: A total of 52 patients with OSA requiring CPAP > 15 cm H2 O (71% male, age: 58 (15) years, BMI: 42.6 (10.1) kg/m2 , apnoea-hypopnoea index (AHI): 51.1 (30.4)/h) were studied; 62% had respiratory co-morbidities affecting nocturnal breathing including obesity hypoventilation syndrome and COPD; 25% had neuromuscular conditions; and 17% had cardiovascular disease. CPAP was used for 199 (106-477) days prior to referral for BPAP. Reasons for CPAP failure were intolerant pressures (23%), uncontrolled symptoms (23%), mask problems (21%), adverse effects (13%), claustrophobia (8%), co-morbidities (8%) and other issues (4%). Lower expiratory positive airway pressures were needed with BPAP compared to CPAP (10 (8-12) vs 16.8 (15.7-19.2) cm H2 O, P = 0.001); patients achieved better adherence to BPAP (7.0 (4.0-8.5) vs 2.5 (1.6-6.7) h/night, P = 0.028) and better symptom control (ESS: 4.0 (1.0-7.0) vs 10.0 (6.0-17.0) points, P = 0.039). CONCLUSION: In patients with moderate-severe OSA who fail CPAP therapy due to low adherence, BPAP is well tolerated and achieves sufficient control of sleep-disordered breathing and its symptoms.

Self-reported sleepiness in the context of fitness-to-drive.

BACKGROUND: Excessive daytime sleepiness (EDS) is a contributing factor to road traffic accidents. It is commonly assessed using self-administered questionnaires. These assessments are important information when discussing with the Driver and Vehicle Licensing Agency (DVLA) about fitness-to-drive. We hypothesised that patients may be confounded in their assessments after being informed about these potential implications. PATIENTS AND METHODS: This was a prospective single-centre study. Patients attending clinics for sleep-disordered breathing were asked to fill in the Epworth Sleepiness Scale (ESS) and the Stanford Sleepiness Scale (SSS). Following their consultation, patients were informed about EDS in the context of driving and that the DVLA might request information based on their self-assessed sleepiness. They were then asked to complete the same questionnaires again. Parameters recorded included age, gender, body mass index (BMI), driving licence holder, and collar size. An ESS score above 10 points was defined as EDS. RESULTS: One hundred twenty-two subjects were studied (age 59.4 years (15.2); 72 males; BMI 32.1 kg/m2 (8.3), driving licence held for 25.2 years (20.6) (n = 94); collar size 42.7 cm (5.0)). There was no difference in the ESS [8 (8) vs 8 (8) points; p = 0.289] or the SSS [2 (2) vs 2 (2) points; p = 0.320] between the two occasions, although seven patients (5.7%) changed their scores from "sleepy" to "non-sleepy" and four patients (3.3%) from "non-sleepy" to "sleepy". CONCLUSION: Providing patients with information about the risk of driving in the context of sleepiness does not significantly change how they score their symptoms using self-administered questionnaires; only about 9.0% of the patients had inconsistent results.

Effectiveness and side-effect profile of stimulant therapy as monotherapy and in combination in the central hypersomnias in clinical practice.

Effectiveness and side-effect profile data on pharmacotherapy for daytime sleepiness in central hypersomnias are based largely upon randomized controlled trials. Evidence regarding the use of combination therapy is scant. The aim of this study was to examine the effectiveness and occurrence of drug-related side effects of these drugs in routine clinical practice. Adult patients diagnosed with a central hypersomnia during a 54-month period at a tertiary sleep disorders centre were identified retrospectively. Side effects were recorded at every follow-up visit. A total of 126 patients, with 3275 patient-months of drug exposure, were categorized into narcolepsy type 1 (n = 70), narcolepsy type 2 (n = 47) and idiopathic hypersomnia (n = 9). Modafinil was the most common drug used as a first-line treatment (93%) and in combination therapy (70%). Thirty-nine per cent of the patients demonstrated a complete, 25% partial and 36% a poor response to treatment. Combination treatment improved daytime sleepiness in 55% of the patients with residual symptoms despite monotherapy. Sixty per cent of patients reported side effects, and 30% reported treatment-limiting side effects. Drugs had similar side-effect incidence (P = 0.363) and their side-effect profile met those reported in the literature. Twenty-seven per cent of the patients received combination treatment and had fewer side effects compared to monotherapy (29.4% versus 60%, respectively, P = 0.001). Monotherapy appears to achieve satisfactory symptom control in most patients with central hypersomnia, but significant side effects are common. Combination therapy appears to be a useful and safe option in patients with refractory symptoms.

Phenotyping the pathophysiology of obstructive sleep apnea using polygraphy/polysomnography: a review of the literature.

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.

The acute effect of continuous positive airway pressure titration on blood pressure in awake overweight/obese patients with obstructive sleep apnoea.

OBJECTIVES: Continuous positive airway pressure (CPAP) improves upper airway obstruction in patients with obstructive sleep apnoea (OSA), who often are overweight-obese. Although it is thought that CPAP improves long-term blood pressure control (BP), the impact of acute and short-term CPAP use on the cardiovascular system in obese patients has not been described in detail. METHODS: Obese patients (body mass index, BMI > 25 kg/m2) with OSA were studied awake, supine during incremental CPAP titration (4-20 cmH2O, +2 cmH2O/3 mins). BP was measured continuously with a beat-to-beat BP monitor (Ohmeda 2300, Finapres Medical Systems, Amsterdam/NL), BP variability (BPV) was calculated as the standard deviation of BP at each CPAP level, the 95% confidence interval (95%CI) was calculated and changes in BP and BPV were reported. RESULTS: 15 patients (12 male, 48 ± 10) years, BMI 38.9 ± 5.8 kg/m2) were studied; the baseline BP was 131.0 ± 10.2/85.1 ± 9.1 mmHg. BP and BPV increased linearly with CPAP titration (systolic BP r = 0.960, p < .001; diastolic BP r = 0.961, p < .001; systolic BPV r = 0.662, p = .026; diastolic BPV r = 0.886, p < .001). The systolic BP increased by +17% (+23.15 (7.9, 38.4) mmHg; p = .011) and the diastolic BP by +23% (+18.27 (2.33, 34.21) mmHg; p = .009), when titrating CPAP to 20 cmH2O. Systolic BPV increased by +96% (+5.10 (0.67, 9.53) mmHg; p < .001) and was maximal at 14 cmH2O, and diastolic BPV by +97% (+3.02 (0.26, 5.78) mmHg; p < .001) at 16 cmH2O. CONCLUSION: Short-term incremental CPAP leads to significant increases in BP and BPV in obese patients with OSA while awake. Careful titration of pressures is required to minimise the risk of nocturnal awakenings while improving BP control.

Coexistence of OSA may compensate for sleep related reduction in neural respiratory drive in patients with COPD.

BACKGROUND: The mechanisms underlying sleep-related hypoventilation in patients with coexisting COPD and obstructive sleep apnoea (OSA), an overlap syndrome, are incompletely understood. We compared neural respiratory drive expressed as diaphragm electromyogram (EMGdi) and ventilation during stage 2 sleep in patients with COPD alone and patients with overlap syndrome. METHODS: EMGdi and airflow were recorded during full polysomnography in 14 healthy subjects, 14 patients with OSA and 39 consecutive patients with COPD. The ratio of tidal volume to EMGdi was measured to indirectly assess upper airway resistance. RESULTS: Thirty-five patients with COPD, 12 healthy subjects and 14 patients with OSA completed the study. Of 35 patients with COPD, 19 had COPD alone (FEV1 38.5%±16.3%) whereas 16 had an overlap syndrome (FEV1 47.5±16.2%, AHI 20.5±14.1 events/hour). Ventilation (VE) was lower during stage 2 sleep than wakefulness in both patients with COPD alone (8.6±2.0 to 6.5±1.5 L/min, p<0.001) and those with overlap syndrome (8.3±2.0 to 6.1±1.8 L/min). Neural respiratory drive from wakefulness to sleep decreased significantly for patients with COPD alone (29.5±13.3% to 23.0±8.9% of maximal, p<0.01) but it changed little in those with overlap syndrome. The ratio of tidal volume to EMGdi was unchanged from wakefulness to sleep in patients with COPD alone and healthy subjects but was significantly reduced in patients with OSA or overlap syndrome (p<0.05). CONCLUSIONS: Stage 2 sleep-related hypoventilation in COPD alone is due to reduction of neural respiratory drive, but in overlap syndrome it is due to increased upper airway resistance.

The use of an online Epworth Sleepiness Scale to assess excessive daytime sleepiness.

PURPOSE: Excessive daytime sleepiness is the most common complaint reported in sleep clinics. We hypothesised that utilising modern media to deliver an online Epworth Sleepiness Scale, age- and gender-related differences in subjective daytime sleepiness could be assessed. METHODS: Age, gender and online Epworth Sleepiness Scale (range 0-24 points) of 39,448 subjects were recorded between January 2013 and November 2015. RESULTS: A significant trend, for males but not females, was found between age and Epworth score (p < 0.001). Average scores were higher for female subjects in their 1st and 2nd (p = 0.014), 3rd (p < 0.011) and 4th lifetime decade (p = 0.011), whereas male subjects conveyed significantly higher levels of sleepiness in their 7th lifetime decade (p < 0.001). Individual item analysis found differences between gender; females scored significantly higher than males in items 1, 4 and 5, while male subjects had higher scores for items 3, 6, 7 and 8. Lowest levels of sleepiness were reported for item 8 and highest scores for item 5. CONCLUSIONS: The use of an online Epworth Sleepiness Scale identifies gender- and age-specific differences and facilitates new pathways in the delivery of chronic care.

Neural respiratory drive and symptoms that limit exercise in chronic obstructive pulmonary disease.

BACKGROUND: Exercise capacity in chronic obstructive pulmonary disease (COPD) is limited by both breathlessness and leg muscle fatigue. Neural respiratory drive, measured as diaphragm electromyogram (EMGdi) activity expressed as a proportion of maximum (EMGdi%max), quantifies the mechanical load on the respiratory muscles and relates closely to breathlessness. We tested the hypothesis that end-exercise EMGdi%max would be higher in patients stopping because of breathlessness than in those limited by leg fatigue. METHODS: EMGdi, ventilation, rate of oxygen consumption (VO2), and ventilatory reserve (ventilation/maximum ventilatory volume ratio [VE/MVV]) were measured continuously in patients with COPD during exhaustive cycle ergometry. EMGdi was measured with a multipair oesophageal catheter passed per-nasally. Differences in physiological variables between groups of patients stopping because of breathlessness, leg fatigue, or both were assessed with one-way ANOVA. FINDINGS: 23 patients were included (median FEV1, 39% of predicted, IQR 30·0-56·8). End-exercise EMGdi%max was significantly higher in patients stopping exercise because of breathlessness (n=12, median EMGdi%max 75·7% [IQR 69·5-77·1]) than in those stopping because of leg fatigue (n=8, 44·1 [39·4-63·3]) or both (n=3, 74·1 [63·6-81·2]) (p=0·02). There were no significant differences between the groups in end-exercise ventilation (breathlessness 25·7 L/min [16·3-32·0] vs leg fatigue 31·5 [20·9-39·6] vs both 22·0 [17·7-35·7]), VO2, (13·4 mL/min per kg [11·6-14·2] vs 12·1 [10·4-14·8] vs 9·4 [9·1-12·4]), or VE/MVV (80·4% [72·6-88·3] vs 57·8 [52·1-92·6] vs 63·9 [34·5-88·9]). INTERPRETATION: These results suggest that patients limited by breathlessness due to ventilatory constraints can be identified as those reaching near-maximum levels of neural respiratory drive during exercise. Measurement of EMGdi%max during exercise could prove useful in identifying patients whose functional performance would be best optimised by improvment in pulmonary mechanics rather than interventions to train peripheral muscle groups. FUNDING: None.

Randomised sham-controlled trial of transcutaneous electrical stimulation in obstructive sleep apnoea.

INTRODUCTION: Obstructive sleep apnoea (OSA) is characterised by a loss of neuromuscular tone of the upper airway dilator muscles while asleep. This study investigated the effectiveness of transcutaneous electrical stimulation in patients with OSA. PATIENTS AND METHODS: This was a randomised, sham-controlled crossover trial using transcutaneous electrical stimulation of the upper airway dilator muscles in patients with confirmed OSA. Patients were randomly assigned to one night of sham stimulation and one night of active treatment. The primary outcome was the 4% oxygen desaturation index, responders were defined as patients with a reduction >25% in the oxygen desaturation index when compared with sham stimulation and/or with an index <5/hour in the active treatment night. RESULTS: In 36 patients (age mean 50.8 (SD 11.2) years, male/female 30/6, body mass index median 29.6 (IQR 26.9-34.9) kg/m(2), Epworth Sleepiness Scale 10.5 (4.6) points, oxygen desaturation index median 25.7 (16.0-49.1)/hour, apnoea-hypopnoea index median 28.1 (19.0-57.0)/hour) the primary outcome measure improved when comparing sham stimulation (median 26.9 (17.5-39.5)/hour) with active treatment (median 19.5 (11.6-40.0)/hour; p=0.026), a modest reduction of the mean by 4.1 (95% CI -0.6 to 8.9)/hour. Secondary outcome parameters of patients' perception indicated that stimulation was well tolerated. Responders (47.2%) were predominantly from the mild-to-moderate OSA category. In this subgroup, the oxygen desaturation index was reduced by 10.0 (95% CI 3.9 to 16.0)/hour (p<0.001) and the apnoea-hypopnoea index was reduced by 9.1 (95% CI 2.0 to 16.2)/hour (p=0.004). CONCLUSION: Transcutaneous electrical stimulation of the pharyngeal dilators during a single night in patients with OSA improves upper airway obstruction and is well tolerated. TRIAL REGISTRATION NUMBER: NCT01661712.

Parasternal electromyography to determine the relationship between patient-ventilator asynchrony and nocturnal gas exchange during home mechanical ventilation set-up.

INTRODUCTION: Patient-ventilator asynchrony (PVA) can adversely affect the successful initiation of non-invasive home mechanical ventilation (HMV). The aim of this observational study was to quantify the prevalence of PVA during initiation of HMV and to determine the relationship between PVA and nocturnal gas exchange. METHOD: Type and frequency of PVA were measured by surface parasternal intercostal muscle electromyography, thoracoabdominal plethysmography and mask pressure during initiation of HMV. Severe PVA was defined, as previously, as asynchrony affecting ≥10% of breaths. RESULTS: 28 patients (18 male) were enrolled aged 61±15 years and with a body mass index of 35±9 kg/m(2). Underlying diagnoses were neuromuscular disease with or without chest wall disease (n=6), obesity related chronic respiratory failure (n=12) and COPD (n=10). PVA was observed in all patients with 79% of patients demonstrating severe PVA. Triggering asynchrony was most frequent, observed in 24% (IQR: 11-36%) of breaths, with ineffective efforts accounting for 16% (IQR: 4-24%). PVA types were similar between disease groups, with the exception of auto-triggering, which was higher in patients with COPD (12% (IQR: 6-26%)). There was no correlation observed between PVA and time spent with oxygen saturations ≤90%, mean oxygen saturations or transcutaneous carbon dioxide levels during overnight ventilation. CONCLUSIONS: Severe PVA was identified in the majority of patients, irrespective of pathophysiological disease state. This was not associated with ineffective ventilation as evidenced by gas exchange.

Neural respiratory drive and breathlessness in COPD.

The aim of this study was to test the hypothesis that neural respiratory drive, measured using diaphragm electromyogram (EMGdi) activity expressed as a percentage of maximum (EMGdi%max), is closely related to breathlessness in chronic obstructive pulmonary disease. We also investigated whether neuroventilatory uncoupling contributes significantly to breathlessness intensity over an awareness of levels of neural respiratory drive alone. EMGdi and ventilation were measured continuously during incremental cycle and treadmill exercise in 12 chronic obstructive pulmonary disease patients (forced expiratory volume in 1 s±sd was 38.7±14.5 % pred). EMGdi was expressed both as EMGdi%max and relative to tidal volume expressed as a percentage of predicted vital capacity to quantify neuroventilatory uncoupling. EMGdi%max was closely related to Borg breathlessness in both cycle (r=0.98, p=0.0001) and treadmill exercise (r=0.94, p=0.005), this relationship being similar to that between neuroventilatory uncoupling and breathlessness (cycling r=0.94, p=0.005; treadmill r=0.91, p=0.01). The relationship between breathlessness and ventilation was poor when expansion of tidal volume became limited. In chronic obstructive pulmonary disease the intensity of exertional breathlessness is closely related to EMGdi%max. These data suggest that breathlessness in chronic obstructive pulmonary disease can be largely explained by an awareness of levels of neural respiratory drive, rather than the degree of neuroventilatory uncoupling. EMGdi%max could provide a useful physiological biomarker for breathlessness in chronic obstructive pulmonary disease.