More than Heart Failure: Central Sleep Apnea and Sleep-Related Hypoventilation

Central sleep apnea (CSA) comprises a variety of breathing patterns and clinical entities. They can be classified into 2 categories based on the partial pressure of carbon dioxide in the arterial blood. Nonhypercapnic CSA is usually characterized by a periodic breathing pattern, while hypercapnic CSA is based on hypoventilation. The latter CSA form is associated with central nervous, neuromuscular, and rib cage disorders as well as obesity and certain medication or substance intake. In contrast, nonhypercapnic CSA is typically accompanied by an overshoot of the ventilation and often associated with heart failure, cerebrovascular diseases, and stay in high altitude. CSA and hypoventilation syndromes are often considered separately, but pathophysiological aspects frequently overlap. An integrative approach helps to recognize underlying pathophysiological mechanisms and to choose adequate therapeutic strategies. Research in the last decades improved our insights; nevertheless, diagnostic tools are not always appropriately chosen to perform comprehensive sleep studies. This supports misinterpretation and misclassification of sleep disordered breathing. The purpose of this article is to highlight unresolved problems, raise awareness for different pathophysiological components and to discuss the evidence for targeted therapeutic strategies. (C) 2019 S. Karger AG, Base

Effects of respiratory muscle training (RMT) in patients with mild to moderate obstructive sleep apnea (OSA)

Purpose Different forms of training focusing on the muscles of the upper airways showed limited effects on obstructive sleep apnea (OSA) and/or snoring. We investigated the effect of generalized respiratory muscle training (RMT) in lean patients with mild to moderate OSA. Methods Nine male subjects (52.0 +/- 10.8 years, BMI 29.1 +/- 2.1 kg/m(2)) with obstructive sleep apnea (apneahypopnea index (AHI) 9-29) participated in an open, singlearm pilot study. After a 1-week build-up phase, patients underwent 4 weeks of normocapnic hyperpnea RMT five times a week for 30 min each. The initial and final measurements comprised polysomnography, pulmonary function tests, Epworth sleepiness scale (ESS), and SF-36 questionnaire (quality of life (QoL) self-assessment). The investigational site was a university-affiliated hospital for pulmonary diseases and sleep medicine, Solingen/Germany. Results Patients trained effectively, seen by a significant (p < 0.01) increase of breathing frequency (23.3 +/- 1.5/min vs. 30.6 +/- 2.9 / min) and minute volume (81.2 +/- 13.7 L vs. 109.1 +/- 21.9 L). AHI, snoring and ESS remained unchanged after training. QoL as measured by SF-36 significantly (p < 0.05) improved after the training in the subscales Bbodily pain'' (79 +/- 21 vs. 90 +/- 12) and Bchange of health'' (3.1 +/- 0.3 vs. 2.4 +/- 0.5). Conclusions There is no evidence that AHI, pulmonary function or daytime sleepiness are affected by 5 weeks of RMT. Nevertheless, there is an improvement of parameters of quality of life

Sleep-related breathing disorders in idiopathic pulmonary fibrosis are frequent and may be associated with pulmonary vascular involvement

Purpose Sleep-related breathing disorders (SRBD) may be associated with a worse prognosis in idiopathic pulmonary fibrosis (IPF). However, the prevalence of sleep disorders in IPF and the pathophysiological link between SRBD and IPF is unclear. Patients and methods In this prospective trial, consecutive patients with stable IPF underwent polysomnography and cardiopulmonary exercise testing. Epworth sleepiness scale, Regensburg insomnia scale, and Pittsburgh sleep quality index were evaluated. Exclusion criteria were oxygen supplementation therapy, lung emphysema, and heart failure. For pairwise comparison of categorical data, the two-proportion z-test was applied. Correlation between continuous variables was assessed via the Pearson correlation coefficient. Patients without and with SRBD were compared. To find predictors for SRBD in IPF, multivariable logistic regression was applied. Results A total of 74 IPF patients were evaluated and 45 patients (11 female, median age 74 years, forced vital capacity 71.3%, DLCO 53.9%) were analyzed. Any kind of sleep disorder was found in 89% of patients. SRBD was present in 49% (81% obstructive sleep apnea, 19% central sleep apnea), insomnia in 40%, and periodic leg movements in 47% of subjects. The SRBD subgroup presented with a significantly lower performance (workload(peak)%pred 86.5 vs. 101.0 (p = 0.036); V ' O-2(AT) 618.5 ml/min vs. 774.0 ml/min (p = 0.043)) and exhibited a significantly higher V ' E/V ' CO2(peak) of 43.0 l/l vs. 38.5 l/l (p = 0.037). In search of predictors for SRBD by logistic regression, workload(peak)%pred was identified as a significant variable (p = 0.033). Conclusions SRBD is frequent in IPF. Pulmonary vascular limitations may represent the pathophysiological link between IPF and SRBD. Workload(peak)%pred may be an independent risk factor for the occurrence of SRBD

Noninvasive Prediction of Twitch Transdiaphragmatic Pressure: Insights from Spirometry, Diaphragm Ultrasound, and Phrenic Nerve Stimulation Studies

Background: Twitch transdiaphragmatic pressure (twPdi) following magnetic stimulation (MS) of the phrenic nerves is the gold standard for non-volitional assessment of diaphragm strength. Expiratory muscle function can be investigated using MS of the abdominal muscles and measurement of twitch gastric pressure (twPgas). Objectives: To investigate whether twitch pressures following MS of the phrenic and lower thoracic nerve roots can be predicted noninvasively by diaphragm ultrasound parameters and volitional tests of respiratory muscle strength. Methods: Sixty-three healthy subjects underwent standard spirometry, measurement of maximum inspiratory (PImax) and expiratory pressure (PEmax), and diaphragm ultrasound. TwPdi following cervical MS of the phrenic nerve roots and twPgas after lower thoracic MS (twPgas-Thor) were measured using esophageal and gastric balloon catheters inserted transnasally. Using surface electrodes, compound muscle action potentials (CMAP) were simultaneously recorded from the diaphragm or obliquus abdominis muscles, respectively. Results: Forced expiratory flow (FEF25-75) was significantly correlated with twPdi (r = 0.37; p = 0.003) and its components (twPgas and twitch esophageal pressure, twPes). Diaphragm excursion velocity during tidal breathing was correlated to twPes (r = 0.44; p = 0.02). No prediction of twitch pressures was possible from CMAP amplitude, forced vital capacity (FVC), or PImax. TwPgas-Thor was correlated with FEF25-75 (r = 0.46; p = 0.05) and diaphragm thickness at total lung capacity (r = 0.38; p = 0.04) but could not be predicted from CMAP amplitude, FVC, or PEmax. Conclusions: TwPdi and twPgas-Thor cannot be predicted from volitional measures of respiratory muscle strength, diaphragm and abdominal CMAP, or diaphragm ultrasound. Invasive recording of esophageal and gastric pressures following MS remains indispensable for objective assessment of respiratory muscle strength

Transbronchial cryobiopsy in fibrosing interstitial lung disease: modifications of the procedure lead to risk reduction

Sixty-one subjects with fibrosing interstitial lung disease were prospectively analysed to determine the efficacy of transbronchial cryobiopsy (CryoTBB) and the effect of procedural modifications which were introduced after an interim analysis of the first 19 subjects. The modifications significantly reduced complication rates from 84% to 14% (p<0.001). 30-day-mortality was 2%. The algorithm with initial CryoTBB and surgical lung biopsy (SLB) as optional step-up procedure was feasible. CryoTBB led to a confident diagnosis in 46/61 subjects (75%). Only 21% out of all subjects were forwarded for SLB. As the modified CryoTBB reduced but not eliminated the risk of severe complications, tissue sampling should be limited to patients where confident diagnosis enables life prolonging therapy