Singular Value Decomposition for Removal of Cardiac Interference from Trunk Electromyogram.

A new algorithm based on singular value decomposition (SVD) to remove cardiac contamination from trunk electromyography (EMG) is proposed. Its performance is compared to currently available algorithms at different signal-to-noise ratios (SNRs). The algorithm is applied on individual channels. An experimental calibration curve to adjust the number of SVD components to the SNR (0-20 dB) is proposed. A synthetic dataset is generated by the combination of electrocardiography (ECG) and EMG to establish a ground truth reference for validation. The performance is compared with state-of-the-art algorithms: gating, high-pass filtering, template subtraction (TS), and independent component analysis (ICA). Its applicability on real data is investigated in an illustrative diaphragm EMG of a patient with sleep apnea. The SVD-based algorithm outperforms existing methods in reconstructing trunk EMG. It is superior to the others in the time (relative mean squared error < 15%) and frequency (shift in mean frequency < 1 Hz) domains. Its feasibility is proven on diaphragm EMG, which shows a better agreement with the respiratory cycle (correlation coefficient = 0.81, p-value < 0.01) compared with TS and ICA. Its application on real data is promising to non-obtrusively estimate respiratory effort for sleep-related breathing disorders. The algorithm is not limited to the need for additional reference ECG, increasing its applicability in clinical practice.

Nocturnal apnea in Chiari type I malformation.

UNLABELLED: A 4-year-old girl presented with sleep-disordered breathing. Her parents described breathing pauses of up to 20 s and progressive tiredness during the day. Obstructive apneas from an enlarged adenoid were thought to be the most probable cause. However, an adenotomy did not resolve the problem. Polysomnography demonstrated central apneas, and cerebral magnetic resonance imaging revealed a Chiari type I malformation. We describe the differential diagnosis of apnea in children and the role of polysomnography in the distinction between obstructive and central apneas. CONCLUSION: This case illustrates that, in children with apnea, it is important to consider central causes as well as the more common obstructive causes, even in the absence of additional neurological signs or symptoms.

Adherence to continuous positive airway pressure in adults with an intellectual disability.

STUDY OBJECTIVES: This retrospective study evaluated the feasibility of continuous positive airway pressure (CPAP) therapy in adults with intellectual disabilities (ID). METHODS: CPAP therapy of 24 obstructive sleep apnea syndrome (OSA) patients with ID were compared to age- and sex-matched adults with normal cognitive functioning. All ID patients received an intensive in-hospital training protocol to stimulate adherence. Good adherence was defined as a use of >70% of the nights and >4 h/night. Influencing factors were assessed. RESULTS: Baseline apnea-hypopnea index (AHI) was significantly higher in ID patients compared to controls (median 34/h (range 6-101) versus 17/h (range 5-50), p = 0.013). The required average duration of in-hospital training was four nights (range 1-8 days). At six weeks, 60% of the ID patients showed good adherence and 65% at six months, compared to 71% and 50% respectively in the control group. Mean CPAP use per night was equal in both groups both at six weeks (5 h in both groups) and six months (ID 6:30 h vs control 5 h (p = 0.18)). CPAP adherence correlated with baseline AHI in the control patients, but not in ID patients. There was no correlation between CPAP adherence and the level of ID or the degree of support at home. CONCLUSIONS: Using an intensive training protocol it is very well feasible to apply CPAP therapy in OSA patients with any degree of ID. CPAP adherence in ID patients was comparable to the control patients in this study as well as to previously published adherence numbers.

Assessment of respiratory effort during sleep: Esophageal pressure versus noninvasive monitoring techniques.

Monitoring of respiratory effort is paramount in the clinical diagnostic recording of sleep. Increased respiratory effort is a sign of obstructive sleep-disordered breathing and is associated with arousals from sleep. Respiration is the result of muscle activity that induces negative intrathoracic pressure and expansion of the thoracic and abdominal cavities. Therefore respiratory effort may be recorded from mechanical, electrical and electromechanical signals. Several techniques are available for the recording of respiratory effort. Monitoring of esophageal pressure is still the method of choice, as the pressure signal directly reflects the respiratory muscle force. However, esophageal pressure monitoring is cumbersome and may be replaced with noninvasive techniques. In order to be reliable, these techniques must be validated against the esophageal pressure standard. The present review presents a concise description of the technical principles and, if available, a comparison with esophageal pressure data, based on a systematic literature search. Most data are available on respiratory inductance plethysmography, and confirm that this technique is suitable for routine diagnostic investigation of respiratory effort during sleep. Pulse transit time, diaphragmatic electromyography, snoring loudness, suprasternal pressure monitoring, midsagittal jaw movement and forehead venous pressure monitoring are promising alternative techniques although only limited validation is available.