Obesity hypoventilation syndrome as a spectrum of respiratory disturbances during sleep

OBJECTIVE: To identify the spectrum of respiratory disturbances during sleep in patients with obesity hypoventilation syndrome (OHS) and to examine the response of hypercapnia to treatment of the specific ventilatory sleep disturbances. DESIGNS AND METHODS: Twenty-three patients with chronic awake hypercapnia (mean [+/- SD] PaCO(2), 55 +/- 6 mm Hg) and a respiratory sleep disorder were retrospectively identified. Nocturnal polysomnography testing was performed, and flow limitation (FL) was identified from the inspiratory flow-time contour. Obstructive hypoventilation was inferred from sustained FL coupled with O(2) desaturation that was corrected with treatment of the upper airway obstruction. Central hypoventilation was inferred from sustained O(2) desaturation that persisted after the correction of the upper airway obstruction. Treatment was initiated, and follow-up awake PaCO(2) measurements were obtained (follow-up range, 4 days to 7 years). RESULTS: A variable number of obstructive sleep apneas/hypopneas (ie, obstructive sleep apnea-hypopnea syndrome [OSAHS]) were noted (range, 9 to 167 events per hour of sleep). Of 23 patients, 11 demonstrated upper airway obstruction alone (apnea-hypopnea/FL) and 12 demonstrated central sleep hypoventilation syndrome (SHVS) in addition to a variable number of OSAHS. Treatment aimed at correcting the specific ventilatory abnormalities resulted in correction of the chronic hypercapnia in all compliant patients (compliant patients: pretreatment, 57 +/- 6 mm Hg vs post-treatment, 41 +/- 4 mm Hg [p < 0.001]; noncompliant patients: pretreatment, 52 +/- 6 mm Hg vs post-treatment, 51 +/- 3 mm Hg; [difference not significant]). CONCLUSIONS: This study demonstrates that OHS encompasses a variety of distinct pathophysiologic disturbances that cannot be distinguished clinically at presentation. Sustained obstructive hypoventilation due to partial upper airway obstruction was demonstrated as an additional mechanism for OHS that is not easily classified as SHVS or OSAHS.     

Acute respiratory failure in obesity

Obstructive sleep apnea, obesity-related hypoventilation - a hypoventilation which is independent of apneas and increased by sleep -, and hypoxemia related to local ventilation-perfusion disorders are the main mechanisms of respiratory failure occurring during acute respiratory decompensation following an often minimal triggering event. Non-invasive ventilation has been found to be an effective treatment, particularly with a ventilator capable of maintaining positive expiratory and pressure. The level of the expiratory positive airway pressure must be adapted to cure episodes of obstructive apnea or hypopnea. The level of the inspiratory positive airway pressure (pressure support ventilator), or the tidal volume (volume-controlled ventilator) must be adapted to correct the residual hypoventilation. These adaptations can be made by proper assessment of nocturnal SaO(2) recordings. In particularly severe cases, use of endotracheal ventilation may be necessary to control a state of shock or consciousness disorders incompatible with the patient cooperation necessary for non-invasive ventilation.     

Non‐invasive ventilation for obese patients with chronic respiratory failure: Are two pressures always better than one?

Obesity‐related respiratory failure is increasingly common but remains under‐diagnosed and under‐treated. There are several clinical phenotypes reported, including severe obstructive sleep apnoea (OSA), isolated nocturnal hypoventilation with or without severe OSA and OSA complicating chronic obstructive pulmonary disease (COPD). The presence of hypercapnic respiratory failure is associated with poor clinical outcomes in each of these groups. While weight loss is a core aim of management, this is often unachievable, and treatment of sleep‐disordered breathing with positive airway pressure (PAP) therapy is the mainstay of clinical practice. Although there are few long‐term clinical efficacy trials, the lack of equipoise would prevent the utilization of an untreated control group. The current data support the use of PAP therapy to improve respiratory failure and is associated with improvements in health‐related quality of life, reduced healthcare utilization and reduced mortality. Both continuous PAP (CPAP) and non‐invasive ventilation (NIV) appear safe and effective in patients with obesity‐related respiratory failure and OSA, with or without COPD, and the current evidence would not support a single therapy choice in all patients. There are no studies of CPAP in patients with isolated nocturnal hypoventilation, and NIV would be the current recommendation in this patient group. Whichever starting therapy is used, titration should be performed to correct sleep‐disordered breathing and reverse chronic respiratory failure, with consideration of step‐down of the treatment based on a clinical re‐evaluation. In contrast, failure to reach physiological and clinical treatment targets should lead to the consideration of treatment escalation.     

Ventilación mecánica no invasiva en pacientes con síndrome de obesidad-hipoventilación. Evolución a largo plazo y factores pronósticos

IntroductionObesity is associated with 2 closely related respiratory diseases: obesity hypoventilation syndrome (OHS) and obstructive sleep apnea-hypopnea syndrome (OSAHS). It has been shown that noninvasive ventilation during sleep produces clinical and functional improvement in these patients. The long-term survival rate with this treatment, and the difference in clinical progress in OHS patients with and without OSAHS are analyzed.MethodologyLongitudinal, observational study with a cohort of patients diagnosed with OHS, included in a home ventilation program over a period of 12 years, divided into 2 groups: pure OHS and OSAHS-associated OHS. Bi-level positive airway pressure ventilation was administered. During the follow-up period, symptoms, exacerbations and hospitalizations, blood gas tests and pulmonary function tests, and survival rates were monitored and compared.ResultsEighty-three patients were eligible for analysis, 60 women (72.3%) and 23 men (27.7%), with a mean survival time of 8.47 years. Fifty patients (60.2%) were included in the group without OSAHS (OHS) and 33 (39.8%) in the OSAHS-associated OHS group (OHS-OSAHS). PaCO₂ in the OHS group was significantly higher than in the OHS-OSAHS group (P < .01). OHS patients also had a higher hospitalization rate (P < .05). There was a significant improvement in both groups in FEV₁ and FVC, and no differences between groups in PaCO₂ and PaO₂ values. There were no differences in mortality between the 2 groups, but low FVC values were predictive of mortality.ConclusionsThe use of mechanical ventilation in patients with OHS, with or without OSAHS, is an effective treatment for the correction of blood gases and functional alterations and can achieve prolonged survival rates.     

Impaired objective daytime vigilance in obesity-hypoventilation syndrome: impact of noninvasive ventilation

BACKGROUND: Obesity-hypoventilation syndrome (OHS) is efficiently treated by noninvasive ventilation (NIV). Sleep respiratory disturbances, reduced ventilatory drive, and excessive daytime sleepiness (EDS) are commonly reported, but their relationships remain unclear. OBJECTIVES: To characterize sleep breathing disorders encountered in patients with OHS, to compare low and normal CO(2) responders in terms of sleep abnormalities, subjective and objective measures of EDS, and to measure the changes induced by NIV on these parameters. METHODS: At baseline and after 5 nights of NIV, 15 consecutive patients (mean [+/- SD] age, 55 +/- 9 years; mean body mass index, 38.7 +/- 6.1 kg/m(2); Paco(2), 47.3 +/- 2.3 mm Hg) prospectively underwent polysomnography, CO(2) ventilatory response testing, Epworth sleepiness scale scoring, and the Oxford Sleep Resistance (OSLER) test, which is an objective vigilance test. RESULTS: OHS patients exhibited obstructive sleep apnea syndrome (mean apnea-hypopnea index, 62 +/- 32 events per hour) and rapid eye movement (REM) sleep hypoventilation (mean REM sleep time, 35 +/- 33%). Baseline CO(2) sensitivity was significantly related to the proportion of hypoventilation during REM sleep (r = 0.54; p = 0.037). Six patients showed abnormal sleep latencies during the OSLER test (71% of the low CO(2) responders vs 14% of the normal CO(2) responders). Low CO(2) responders exhibited significantly shorter sleep latencies during the OSLER test (23 +/- 14 vs 37 +/- 8 min, respectively; p = 0.05). Using NIV, diurnal blood gas levels were improved and REM sleep hypoventilation were suppressed. Objective sleepiness was improved in low CO(2) responders (p = 0.04). CONCLUSION: In OHS patients, the lower the daytime CO(2) response, the higher the proportion of REM sleep hypoventilation and daytime sleepiness. Short-term therapy with NIV improves all of these parameters.     

Neue Methoden der nasalen Überdrucktherapie bei der Schlafapnoe

Today, we can differentiate between various forms of sleep apnea and sleep-related hypoventilation syndrome. These can be treated with different modes of nasal positive pressure therapy. Bi-level systems are used for patients with a combination of obstructive sleep apnea and obesity hypoventilation syndrome. In patients with obstructive sleep apnea with high pressures, modern pressure relief systems may be employed to ease expiration and reduce mouth leakage. With auto-continuous positive airway pressure (CPAP) systems, the mean treatment pressure may be significantly reduced, especially in patients with positional sleep apnea. Special ventilation modes such as adaptive servo-ventilation are increasingly used, for instance in patients with chronic heart failure and Cheyne-Stokes respiration or “complex sleep apnea”. Such modern differential treatment requires adequate differential diagnostics based on profound pathophysiological understanding.     

Chronic hypoventilation syndromes and sleep-related hypoventilation

Chronic hypoventilation affects patients with disorders on any level of the respiratory system. The generation of respiratory impulses can be impaired in congenital disorders, such as central congenital alveolar hypoventilation, in alterations of the brain stem or complex diseases like obesity hypoventilation. The translation of the impulses via spinal cord and nerves to the respiratory muscles can be impaired in neurological diseases. Thoraco-skeletal or muscular diseases may inhibit the execution of the impulses. All hypoventilation disorders are characterized by a reduction of the minute ventilation with an increase of daytime hypercapnia. As sleep reduces minute ventilation substantially in healthy persons and much more pronounced in patients with underlying thoraco-pulmonary diseases, hypoventilation manifests firstly during sleep. Therefore, sleep related hypoventilation may be an early stage of chronic hypoventilation disorders. After treatment of any prevailing underlying disease, symptomatic therapy with non-invasive ventilation (NIV) is required. The adaptation of the treatment should be performed under close medical supervision. Pressure support algorithms have become most frequently used. The most recent devices automatically apply pressure support and vary inspiratory and expiratory pressures and breathing frequency in order to stabilize upper airways, normalize ventilation, achieve best synchronicity between patient and device and aim at optimizing patients’ adherence.     

Treatment of obesity hypoventilation syndrome and serum leptin

BACKGROUND: Leptin is a protein produced by adipose tissue that circulates to the brain and interacts with receptors in the hypothalamus to inhibit eating. In obese humans, serum leptin is up to four times higher than in lean subjects, indicating that human obesity is associated with a central resistance to the weight-lowering effects of leptin. Although the leptin-deficient mouse (ob/ob) develops obesity hypoventilation syndrome (OHS), in humans with OHS, serum leptin is a better predictor of awake hypercapnia in obesity than the body mass index (BMI). This suggests that central leptin resistance may promote the development of OHS in humans. We speculated that the reversal of OHS by regular non-invasive ventilation (NIV) therapy decreases leptin levels. OBJECTIVES: The aim of this study was to investigate whether ventilatory treatment of OHS would alter circulating leptin concentrations. METHOD: We measured fasting serum leptin levels, BMI, spirometry and arterial blood gases in 14 obese hypercapnic subjects undergoing a diagnostic sleep study. RESULTS: The average age of the subjects was (mean +/- SE) 62 +/- 13 years, BMI 40.9 +/- 2.2 kg/m(2), PaCO(2) 6.7 +/- 0.2 kPa, PaO(2 )8.9 +/- 0.4 kPa and total respiratory disturbance index 44 +/- 35 events/hour. Subjects were clinically reviewed after a median of 2.3 years (range 1.6-3) with repeat investigations. Nine patients were regular NIV users and 5 were non-users. NIV users had a significant reduction in serum leptin levels (p = 0.001), without a change in BMI. In these patients, there was a trend towards an improved daytime hypercapnia and hypoxemia, while in the 5 non-users, no changes in serum leptin, BMI or arterial blood gases occurred. CONCLUSION: Regular NIV use reduces serum leptin in OHS. Leptin may be a modulator of respiratory drive in patients with OHS.     

Home Non-Invasive Ventilation for COPD: How,Who and When?

Patients with chronic obstructive pulmonary disease (COPD) and chronic respiratory failure have high levels of morbidity and mortality. The clinical efficacy of long term home oxygen therapy has been well documented in this patient group but despite the efficacy of non-invasive ventilation (NIV) during acute decompensated respiratory failure the addition of home NIV has been associated with equivocal results. The physiological efficacy of home NIV to improve gas exchange in chronic stable hypercapnic respiratory failure has been proven in small studies but larger clinical trials failed to translate this into clinical efficacy. Criticisms of early clinical trials include the use of marginally hypercapnic patients and failure to demonstrate effective delivery of home NIV. When considering recent trial data it is important to clearly evaluate the patient phenotype and timing and delivery of NIV. Recent data supports the delivery of home NIV in patients with chronic hypercapnia (PaCO₂ > 7 kPa or 50 mmHg) and the frequent or infrequent exacerbator phenotype. Importantly in the frequent exacerbator the timing of the assessment needs to be in the recovery phase, 2-4 weeks after resolution of acute acidosis, to delineate transient from persistent hypercapnia. In patient with persistent hypercapnia NIV must be titrated to achieve control of sleep disordered breathing with the aim of improving daytime respiratory failure. Furthermore there are observational data to support the use of home positive airway pressure therapy (NIV or continuous positive airway pressure; CPAP) in patients with COPD and obstructive sleep apnoea (OSA) both with and without hypercapnia.     

Effectiveness of CPAP vs. Noninvasive Ventilation Based on Disease Severity in Obesity Hypoventilation Syndrome and Concomitant Severe Obstructive Sleep Apnea

RationaleObesity hypoventilation syndrome (OHS) with concomitant severe obstructive sleep apnea (OSA) is treated with CPAP or noninvasive ventilation (NIV) during sleep. NIV is costlier, but may be advantageous because it provides ventilatory support. However, there are no long-term trials comparing these treatment modalities based on OHS severity.ObjectiveTo determine if CPAP have similar effectiveness when compared to NIV according to OHS severity subgroups.MethodsPost hoc analysis of the Pickwick randomized clinical trial in which 215 ambulatory patients with untreated OHS and concomitant severe OSA, defined as apnoea-hypopnea index (AHI) ≥ 30 events/h, were allocated to NIV or CPAP. In the present analysis, the Pickwick cohort was divided in severity subgroups based on the degree of baseline daytime hypercapnia (PaCO₂ of 45–49.9 or ≥50 mmHg). Repeated measures of PaCO₂ and PaO₂ during the subsequent 3 years were compared between CPAP and NIV in the two severity subgroups. Statistical analysis was performed using linear mixed-effects model.Results204 patients, 97 in the NIV group and 107 in the CPAP group were analyzed. The longitudinal improvements of PaCO₂ and PaO₂ were similar between CPAP and NIV based on the PaCO₂ severity subgroups.ConclusionIn ambulatory patients with OHS and concomitant severe OSA who were treated with NIV or CPAP, long-term NIV therapy was similar to CPAP in improving awake hypercapnia, regardless of the severity of baseline hypercapnia. Therefore, in this patient population, the decision to prescribe CPAP or NIV cannot be solely based on the presenting level of PaCO₂.     

Quality of Life in Obesity Hypoventilation Syndrome

The first paper of this issue of Sleep and Breathing reports that the quality of life (QOL) assessed by the SF-36 and the Epworth Sleepiness Scale (ESS) in obesity hypoventilation syndrome (OHS) was compared with age- and body mass index-matched patients without hypoventilation (obese OSA), nonobese OSA patients, and healthy subjects. The QOL in OHS was worst among these four groups. After 3 to 6 months of nasal continuous positive airway pressure (CPAP) treatment, the QOL in OHS improved to the normal level similar to the two other OSA groups. We have observed severe nonobese OSA patients with hypoventilation. One of the risk factors, which related to a severe general condition, seems to be a small craniomandibular structure, which could induce an increase in upper airway resistance during sleep. Characteristics of Japanese OSA patients may be different from those in other countries. Although belatedly, the clinical study and management of sleep disordered breathing have just begun.     

持续气道正压通气治疗肥胖低通气综合征

目的探讨持续气道正压通气治疗肥胖低通气综合征（ＯＨＳ）的疗效。方法用ＣＰＡＰ（经鼻持续气道正压通气）及ＢｉＰＡＰ（双水平气道正压通气）呼吸机分别对２１例及１４例肥胖低通气综合征患者治疗２个月,比较治疗前后的呼吸紊乱指数（ＡＨＩ）、低通气指数（ＨＩ）、体块指数（ＢＭＩ）、４％的血氧饱和度降低次数（ＯＤＩ４）以及最低血氧饱和度（ｍｉｎＳａＯ２）,并将ＢＭＩ与ＡＨＩ、ＨＩ及ｍｉｎＳａＯ２作相关性分析。结果肥胖低通气患者治疗后ＡＨＩ、ＨＩ、ＢＭＩ、ＯＤＩ４、ｍｉｎＳａＯ２均有明显改善（Ｐ＜００５）;而ＢＭＩ与ＨＩ、及ｍｉｎＳａＯ２的相关性检验无显著性（相关系数分别为ｒ＝０．０３４６８和ｒ＝０．０５５８１,Ｐ＞００５）,提示单纯降低ＢＭＩ并不能有效地改善ＨＩ及ｍｉｎＳａＯ２。结论持续气道正压通气是治疗ＯＨＳ一种无创、有效的措施,且能在短期内明显改善临床症状,提高生活质量。     

Obesity hypoventilation syndrome: from sleep-disordered breathing to systemic comorbidities and the need to offer combined treatment strategies

Obesity hypoventilation syndrome (OHS) is defined as a combination of obesity (body mass index ≥ 30 kg/m(2)), daytime hypercapnia (partial arterial carbon dioxide concentration ≥45 mm Hg) and sleep-disordered breathing after ruling out other disorders that may cause alveolar hypoventilation. Through the prism of the International Classification of Functioning, OHS is a chronic condition associated with respiratory, metabolic, hormonal and cardiovascular impairments, leading to a decrease in daily life activities, a lack of social participation and high risk of hospitalization and death. Despite its severity, OHS is largely underdiagnosed and the health-related costs are higher than those of apnoeic or obese eucapnic patients. The present review discusses the definition, epidemiology, physiopathology and treatment modalities of OHS. Although nocturnal positive airway pressure therapies represent first-line treatment and are effective in improving patient outcomes, there is a need to offer combined treatment strategies and to assess the effect of multimodal therapeutic strategies on morbidity and mortality.     

Respiratory Center Function and Its Impact in Obesity Hypoventilation Syndrome Treatment

IntroductionPatients with obesity hypoventilation syndrome (OHS) need treatment with positive pressure either with continuous (CPAP) or double pressure (NIV). The apnea–hypopnea index (AHI) is considered a key data for making therapeutic decisions. We hypothesized that HR may be an useful tool to establish different phenotypes and individualize treatment in patients with OHS. Our objective was to analyze the role of the respiratory center response to hypercapnia (HR) in the adequacy of positive airway pressure therapy.MethodWe included subjects with OHS treated with CPAP or NIV according to AHI and baseline pCO₂. We analyzed therapeutic effectiveness and treatment changes prioritizing CPAP if AHI > 30/h. Therapy was considered adequate if it was effective after two years. HR was measured with the p0.1/pEtCO₂ ratio and its capability to select therapy was analyzed. The statistical study was performed by means comparison (Student's t) and multivariate analysis (logistic regression).Results67 subjects were included of 68(11) years old, 37 (55%) males, initially 45 (67%) treated with NIV and 22 (33%) with CPAP, one case was excluded and in 25 (38%) the treatment was changed. Finally, CPAP was adequate for 29 subjects (44%) and NIV for 37 (56%). The CPAP group showed AHI 57/h (24) and p0.1/pEtCO₂ 0.37 cmH₂O/mmHg (0.23), NIV group AHI 43/h (35) and p0.1/pEtCO₂ 0.24 (0.15) with p = 0.049 and 0.006. In multivariate analysis, p0.1/pEtCO₂ (p = 0.033) and AHI > 30 (p = 0.001) were predictors of adequate therapy.ConclusionMeasuring the RH of the respiratory center helps to select the most appropriate treatment for patients with OHS.     

Practical Insight to Monitor Home NIV in COPD Patients

Home noninvasive ventilation (NIV) is used in COPD patients with concomitant chronic hypercapnic respiratory failure in order to correct nocturnal hypoventilation and improve sleep quality, quality of life, and survival. Monitoring of home NIV is needed to assess the effectiveness of ventilation and adherence to therapy, resolve potential adverse effects, reinforce patient knowledge, provide maintenance of the equipment, and readjust the ventilator settings according to the changing condition of the patient. Clinical monitoring is very informative. Anamnesis focuses on the improvement of nocturnal hypoventilation symptoms, sleep quality, and side effects of NIV. Side effects are major cause of intolerance. Screening side effects leads to modification of interface, gas humidification, or ventilator settings. Home care providers maintain ventilator and interface and educate patients for correct use. However, patient's education should be supervised by specialized clinicians. Blood gas measurement shows a significant decrease in PaCO₂ when NIV is efficient. Analysis of ventilator data is very useful to assess daily use, unintentional leaks, upper airway obstruction, and patient ventilator synchrony. Nocturnal oximetry and capnography are additional monitoring tools to assess the impact of NIV on gas exchanges. In the near future, telemonitoring will reinforce and change the organization of home NIV for COPD patients.     

Current perspectives on the obesity hypoventilation syndrome

PURPOSE OF REVIEW: Identifying and treating obesity hypoventilation syndrome is an important therapeutic goal, especially given the high morbidity and mortality associated with untreated disease. Significant weight loss or effective treatment of upper airway obstruction will reverse daytime hypoventilation, suggesting that these two mechanisms play key roles in the development and progression of this disorder. Only a subset of morbidly obese patients will develop awake hypercapnia, however, even in the presence of sleep disordered breathing. This implies that complex interplay between a number of known and unknown mechanisms is needed to produce daytime respiratory failure in this patient population. RECENT FINDINGS: Work in the mouse model of obesity has been central in advancing our understanding of the role leptin plays in stimulating ventilation. Leptin deficiency or development of leptin resistance in obesity leads to alterations in central respiratory drive and reduced ventilatory responsiveness, permitting development of carbon dioxide retention. Changes in neuromodulators resulting from the effects of hypoxia may further exacerbate the problem by depressing arousal from sleep in the face of abnormal breathing. SUMMARY: Understanding the various mechanisms contributing to development of obesity hypoventilation is important in order to identify new approaches to effective long-term management of this disorder.     

Current concepts in the pathogenesis of the obesity-hypoventilation syndrome. Mechanical and circulatory factors

The pathogenesis of carbon dioxide retention associated with obesity, the obesity hypoventilation syndrome (OHS), remains obscure. In an attempt to Identify factors which might Initiate or contribute to this syndrome, we reviewed respiratory and circulatory function in two groups of obese subjects: those who were not hypercapnic (simple obesity) and those who were (OHS).Obese subjects in both groups display reduction of lung and chest wall compliance, normal airway resistance, closure of peripheral lung units and increased energy cost of breathing. These abnormalities are more severe in those who hypoventilate, especially the reduction In compliance. Respiratory muscle efficiency is reduced in both groups. Inspiratory muscle strength of patients with OHS is 60 to 70 per cent of normal. In OHS arterial carbon dioxide tension (PaCO₂), vital capacity and maximum voluntary ventilation improve significantly with weight toss, whereas in simple obesity there Is little change in these factors with weight loss.In both groups the major circulatory findings are increased total and pulmonary blood volume, with preservation of a normal ratio between the two; and good perfusion but marked underventilation of dependent regions of the lung. These changes are more pronounced In OHS. Left ventricular end diastolic pressure is elevated in some patients, but the rise is not confined to those with OHS. In OHS alveolar hypoxia and acidemia produce pulmonary arterial vasoconstriction and pulmonary arterial hypertension. As a consequence pulmonary artery pressure exceeds left ventricular pressure at the end of diastole.We suggest that excessive reduction of chest wall compliance and inspiratory muscle weakness interact with the circulatory abnormalities already present in simple obesity to generate carbon dioxide retention. The contribution of altered central nervous system function to this process remains controversial.     

Advances in non‐invasive positive airway pressure technology

Non‐invasive ventilation (NIV) has become the standard of care for patients with a range of respiratory and sleep breathing disorders. Technological advances have enabled the development of several newer modes of automatically adapting NIV suitable for patients with more complex breathing abnormalities that may be difficult to manage effectively with more traditional positive airway pressure therapy. These modes allow for more stable ventilation when fluctuating ventilation requirements occur such as in positional upper airway obstruction or state‐related variations in respiratory mechanics and drive. Adaptive servoventilation (ASV) is designed for patients with periodic breathing and central apnoeas in whom carbon dioxide levels are normal to low, with the goal of therapy to dampen and stabilize ventilation. In contrast, volume‐assured pressure support is used in diagnostic groups characterized by hypoventilation, where targeting an effective level of ventilation irrespective of sleep stage or body position is required. These newer modes have the potential to simplify and optimize ventilation, although at present there is no evidence that they are clinically superior to standard home ventilation techniques. The complexity and differences in algorithms and features of various device brands, along with a limited evidence base documenting longer term outcomes, complicate decisions around which patient phenotypes are best suited to these newer modes. In‐built sensor and data storage capabilities of newer home ventilation devices provide the opportunity for earlier recognition of issues with ventilation and to guide corrective action. Further work is needed to determine how this impacts longer term clinical outcomes.     

Sleep-related breathing disorders in facioscapulohumeral dystrophy

Purpose

Severe manifestations of facioscapulohumeral dystrophy (FSHD) may be associated with sleep-disordered breathing (SDB), including obstructive sleep apnea (OSA) and nocturnal hypoventilation (NH), but prevalence data are scarce. In patients with respiratory muscle weakness, detection of NH can be facilitated by transcutaneous capnometry, but respective data derived from FSHD patients have not yet been published.

Methods

We collected sleep studies and capnometry recordings from 31 adult patients with genetically confirmed FSHD who were admitted to our sleep laboratory for first-ever evaluation of sleep-related breathing. Indications for admission included non-restorative sleep, morning headache, or excessive daytime sleepiness. In addition, sleep studies were initiated if symptoms or signs of respiratory muscle weakness were present. Thirty-one subjects with insomnia served as controls for comparison of respiratory measures during sleep.

Results

In the FSHD group, 17/31 (55%) patients showed OSA and 8 (26%) had NH. NH would have been missed in 7/8 patients if only oximetry criteria of hypoventilation had been applied. Capnography results were correlated with disease severity as reflected by the Clinical Severity Score (CSS). Non-invasive ventilation (NIV) was started in 6 patients with NH and 3 individuals with OSA. Nocturnal continuous positive airway pressure was administered to 2 patients, and positional therapy was sufficient in 4 individuals. In patients initiated on NIV, nocturnal gas exchange already improved in the first night of treatment.

Conclusions

SDB is common in adult patients with FSHD complaining of sleep-related symptoms. It may comprise OSA, NH, and most often, the combination of both. Sleep-related hypercapnia is associated with disease severity. Transcutaneous capnometry is superior to pulse oximetry for detection of NH.

     

Volume‐targeted pressure support and automatic EPAP for chronic hypoventilation syndromes: An advance in‐home ventilation or just more noise?

Early in the history of non‐invasive ventilation (NIV) for disorders of hypoventilation, treatment was provided by volume‐limited (VL) devices. Currently, NIV is commonly provided by pressure‐limited (PL) devices because of greater portability, lower cost and studies showing increased patient comfort. There are now volume‐targeted (VT) devices, which aim to combine the advantages of more stable ventilation associated with VL and greater comfort of PL mode. VT devices automatically adjust pressure support, within a defined range, to target a preset level of ventilation. This review focuses on current evidence, as provided by clinical randomized controlled trial (RCT) data, for the effectiveness of VT devices. The RCT data have significant methodological limitations, including lack of study blinding, recruitment of patients who are not naïve to NIV and failure to optimize PL settings with recent polysomnography (PSG) titration. However, the data broadly show that VT has similar short‐term clinical outcomes to standard PL mode with regard to measures of nocturnal and daytime ventilation and sleep quality. The literature has not clearly identified if there are subgroups that benefit from VT. Recently, automatic expiratory positive airway pressure (AutoEPAP) algorithms, which aim to automatically control the upper airway during sleep, have been added to VT devices which may obviate the need for PSG to manually titrate EPAP. VT mode has the potential to reduce reliance on PSG and so save on healthcare costs; however, to date, a clear benefit of VT over PL NIV has not been demonstrated.