Classification of Sleep Apnea Severity by Electrocardiogram Monitoring Using a Novel Wearable Device.

Sleep apnea (SA) is a prevalent disorder diagnosed by polysomnography (PSG) based on the number of apnea-hypopnea events per hour of sleep (apnea-hypopnea index, AHI). PSG is expensive and technically complex; therefore, its use is rather limited to the initial diagnostic phase and simpler devices are required for long-term follow-up. The validity of single-parameter wearable devices for the assessment of sleep apnea severity is still debated. In this context, a wearable electrocardiogram (ECG) acquisition system (ECG belt) was developed and its suitability for the classification of sleep apnea severity was investigated using heart rate variability analysis with or without data pre-filtering. Several classification algorithms were compared and support vector machine was preferred due to its simplicity and overall performance. Whole-night ECG signals from 241 patients with a suspicion of sleep apnea were recorded using both the ECG belt and patched ECG during PSG recordings. 65% of patients had an obstructive sleep apnea and the median AHI was 21 [IQR: 7-40] h - 1 . The classification accuracy obtained from the ECG belt (accuracy: 72%, sensitivity: 70%, specificity: 74%) was comparable to the patched ECG (accuracy: 74%, sensitivity: 88%, specificity: 61%). The highest classification accuracy was obtained for the discrimination between individuals with no or mild SA vs. moderate to severe SA. In conclusion, the ECG belt provided signals comparable to patched ECG and could be used for the assessment of sleep apnea severity, especially during follow-up.

Applicability of a Textile ECG-Belt for Unattended Sleep Apnoea Monitoring in a Home Setting.

Sleep monitoring in an unattended home setting provides important information complementing and extending the clinical polysomnography findings. The validity of a wearable textile electrocardiography (ECG)-belt has been proven in a clinical setting. For evaluation in a home setting, ECG signals and features were acquired from 12 patients (10 males and 2 females, showing an interquartile range for age of 48-59 years and for body mass indexes (BMIs) of 28.0-35.5) over 28 nights. The signal quality was assessed by artefacts detection, signal-to-noise ratio, and Poincaré plots. To assess the validity, the data were compared to previously reported data from the clinical setting. It was found that the artefact percentage was slightly reduced for the ECG-belt from 9.7% ± 14.7% in the clinical setting, to 7.5% ± 10.8% in the home setting. The signal-to-noise ratio was improved in the home setting and reached similar values to the gel electrodes in the clinical setting. Finally, it was found that for artefact percentages above 3%, Poincaré plots are instrumental to evaluate the origin of artefacts. In conclusion, the application of the ECG-belt in a home setting did not result in a reduction in signal quality compared to the ECG-belt used in the clinical setting, and thus provides new opportunities for patient pre-screening or follow-up.

Clinical Applicability of a Textile 1-Lead ECG Device for Overnight Monitoring.

Even for 1-lead electrocardiography (ECG), single-use gel conductive electrodes are employed in a clinical setting. However, gel electrodes show limited applicability for long-term monitoring due to skin irritation and detachment. In the present study, we investigated the validity of a textile ECG-belt suitable for long-term measurements in clinical use. In order to assess the signal quality and validity of the ECG-belt during sleep, 242 patients (186 males and 56 females, age 52 (interquartile range 42-60) years, body mass index 29 (interquartile range 26-33) kg·m-2) with suspected sleep apnoea underwent overnight polysomnography including standard 1-lead ECG recording. The single intervals between R-peaks (RR-intervals) were calculated from the ECG-signals. We found a mean difference for average RR-intervals of -2.9 ms, a standard error of estimate of 0.39%, as well as a Pearson r of 0.91. Furthermore, we found that the validity of the ECG-belt decreases when lying on the side, which was potentially due to the fitting of the belt. In conclusion, the validity of RR-interval measurements using the ECG-belt is high and it may be further improved for future applications by optimizing wear fitting.

An integrated approach to develop, validate and operate thermo-physiological human simulator for the development of protective clothing.

Following the growing interest in the further development of manikins to simulate human thermal behaviour more adequately, thermo-physiological human simulators have been developed by coupling a thermal sweating manikin with a thermo-physiology model. Despite their availability and obvious advantages, the number of studies involving these devices is only marginal, which plausibly results from the high complexity of the development and evaluation process and need of multi-disciplinary expertise. The aim of this paper is to present an integrated approach to develop, validate and operate such devices including technical challenges and limitations of thermo-physiological human simulators, their application and measurement protocol, strategy for setting test scenarios, and the comparison to standard methods and human studies including details which have not been published so far. A physical manikin controlled by a human thermoregulation model overcame the limitations of mathematical clothing models and provided a complementary method to investigate thermal interactions between the human body, protective clothing, and its environment. The opportunities of these devices include not only realistic assessment of protective clothing assemblies and equipment but also potential application in many research fields ranging from biometeorology, automotive industry, environmental engineering, and urban climate to clinical and safety applications.

The combined use of heavy and light silicone oil in the treatment of complicated retinal detachment with 360º retinal breaks: tamponade effect or filling effect?

INTRODUCTION: This study aims to report the safety and effi cacy of the combined use of 70% Densiron®-68 and 30% polydimethysiloxane as a temporary vitreous substitute after pars plana vitrectomy (PPV) in selected cases of retinal detachment with superior and inferior retinal breaks. MATERIAL AND METHODS: Fifty consecutive eyes of 50 patients affected by complicated retinal detachment with retinal breaks of the superior and inferior quadrants associated with proliferative vitreoretinopathy (PVR) of grade C2 or more, underwent a pars plana vitrectomy and a combination internal tamponade with 70% Densiron®-68 and 30% silicone oil. The main outcome measures were visual acuity, retinal attachment, intraocular pressure (IOP) and incidence of complications. RESULTS: The mean best-corrected visual acuity rose from 1.4 logMAR to 0.7 logMAR (P <0.01). Initial retinal reattachment was achieved in 48 (96%) patients. In 15 patients (30%), IOP increased over 21 mmHg. The main complications were redetachment at the 3 month follow-up in 12/48 cases (25%) and cataract formation in 13/21 phakic eyes (62%). CONCLUSION: This combination tamponade comprised lighter and heavier oil compounds was well tolerated and effective. It may be a useful tool for the treatment of retinal detachment complicated with breaks and PVR involving the upper and lower quadrants.

Ocular tolerance and efficacy of short-term tamponade with double filling of polydimethyloxane and perfluoro-n-octane.

OBJECTIVE: The aim of the study was to evaluate the ocular tolerance and efficacy of double filling with perfluoro-n-octane (n-C8F18) (PFO) and polydimethyloxane (PDMS) as a temporary vitreous substitute in patients with retinal detachment complicated by proliferative vitreoretinopathy (PVR). MATERIAL AND METHODS: Tamponade was performed in 30 eyes of 30 patients by double filling with 30% PFO and 70% PDMS for an average of 23 (standard deviation 2.2) days. The follow-up visits were scheduled 1 week, 1 month, and 3 months after surgery. The main outcome measures were visual acuity, intraocular pressure (IOP), PVR reproliferation, and electrophysiological parameters. RESULTS: The primary success rate was 80% (24/30). Fourteen patients (46.7%) had a postoperative improvement in visual acuity, 12 patients (40.0%) maintained their preoperative visual acuity, and four patients (13.3%) experienced a reduction in visual acuity. The mean postoperative IOP was 19.7 mm Hg (11-32 mm Hg); nine cases (30.0%) developed an IOP increase that was treated with topical drops and/or systemic carbonic anhydrase inhibitors. The electroretinogram (ERG) and the bright flash electroretinogram (bf ERG) parameters showed a statistically significant difference of means between 4- and 8-week follow-up visits. CONCLUSION: Our experience with double filling in selected cases of retinal detachment has been positive. No electroretinographic signs of retinal toxicity and a low incidence of PVR reproliferation were observed.

Mitochondrial capacity is affected by glycemic status in young untrained women with type 1 diabetes but is not impaired relative to healthy untrained women.

In this study, we examined whether glycemic status influences aerobic function in women with type 1 diabetes and whether aerobic function is reduced relative to healthy women. To this end, we compared several factors determining aerobic function of 29 young sedentary asymptomatic women (CON) with 9 women of similar age and activity level with type 1 diabetes [DIA, HbA1c range = 6.9-8.2%]. Calf muscle mitochondrial capacity was estimated by (31)P-magnetic resonance spectroscopy. Capillarization and muscle fiber oxidative enzyme activity were assessed from vastus lateralis and soleus muscle biopsies. Oxygen uptake and cardiac output were evaluated by ergospirometry and N(2)O/SF(6) rebreathing. Calf muscle mitochondrial capacity was not different between CON and DIA, as indicated by the identical calculated maximal rates of oxidative ATP synthesis [0.0307 (0.0070) vs. 0.0309 (0.0058) s(-1), P = 0.930]. Notably, HbA1c was negatively correlated with mitochondrial capacity in DIA (R(2) = 0.475, P = 0.040). Although HbA1c was negatively correlated with cardiac output (R(2) = 0.742, P = 0.013) in DIA, there was no difference between CON and DIA in maximal oxygen consumption [2.17 (0.34) vs. 2.21 (0.32) l/min, P = 0.764], cardiac output [12.1 (1.9) vs. 12.3 (1.8) l/min, P = 0.783], and endurance capacity [532 (212) vs. 471 (119) s, P = 0.475]. There was also no difference between the two groups either in the oxidative enzyme activity or capillary-to-fiber ratio. We conclude that mitochondrial capacity depends on HbA1c in untrained women with type 1 diabetes but is not reduced relative to untrained healthy women.

Cardiac output but not stroke volume is similar in a Wingate and VO2peak test in young men.

Wingate test (WT) training programmes lasting 2-3 weeks lead to improved peak oxygen consumption. If a single 30 s WT was capable of significantly increasing stroke volume and cardiac output, the increase in peak oxygen consumption could possibly be explained by improved oxygen delivery. Thus, we investigated whether a single WT increases stroke volume and cardiac output to similar levels than those obtained at peak exercise during a graded cycling exercise test (GXT) to exhaustion. Fifteen healthy young men (peak oxygen consumption 45.0 ± 5.3 ml kg(-1) min(-1)) performed one WT and one GXT on separate days in randomised order. During the tests, we estimated cardiac output using inert gas rebreathing (nitrous oxide and sulphur hexafluoride) and subsequently calculated stroke volume. We found that cardiac output was similar (18.2 ± 3.3 vs. 17.9 ± 2.6 l min(-1); P = 0.744), stroke volume was higher (127 ± 37 vs. 94 ± 15 ml; P < 0.001), and heart rate was lower (149 ± 26 vs. 190 ± 12 beats min(-1); P < 0.001) at the end (27 ± 2 s) of a WT as compared to peak exercise during a GXT. Our results suggest that a single WT produces a haemodynamic response which is characterised by similar cardiac output, higher stroke volume and lower heart rate as compared to peak exercise during a GXT.

Non-invasive haemodynamic assessments using Innocor during standard graded exercise tests.

Cardiac output (Q) and stroke volume (V(S)) represent primary determinants of cardiovascular performance and should therefore be determined for performance diagnostics purposes. Since it is unknown, whether measurements of Q and V(S) can be performed by means of Innocor during standard graded exercise tests (GXTs), and whether current GXT stages are sufficiently long for the measurements to take place, we determined Q and V(S) at an early and late point in time on submaximal 2 min GXT stages. 16 male cyclists (age 25.4 +/- 2.9 years, body mass 71.2 +/- 5.0 kg) performed three GXTs and we determined Q and V(S) after 46 and 103 s at 69, 77, and 85% peak power. We found that the rebreathings could easily be incorporated into the GXTs and that Q and V(S) remained unchanged between the two points in time on the same GXT stage (69% peak power, Q: 18.1 +/- 2.1 vs. 18.2 +/- 2.3 l min(-1), V(S): 126 +/- 18 vs. 123 +/- 21 ml; 77% peak power, Q: 20.7 +/- 2.6 vs. 21.0 +/- 2.3 l min(-1), V(S): 132 +/- 18 vs. 131 +/- 18 ml; 85% peak power, Q: 21.6 +/- 2.4 vs. 21.8 +/- 2.7 l min(-1), V(S): 131 +/- 17 vs. 131 +/- 22 ml). We conclude that Innocor may be a useful device for assessing Q and V(S) during GXTs, and that the adaptation of Q and V(S) to exercise-to-exercise transitions at moderate to high submaximal power outputs is fast enough for 1 and 2 min GXT stage durations.

Individualised treatment of proliferative diabetic retinopathy: optimal surgical timing improves long-term outcomes.

Ocular treatment of progressing proliferative diabetic retinopathy is based on retinal laser photocoagulation and pars plana vitrectomy. Improvements in instrumentation and advances in techniques and procedures have increased indications for vitrectomy. These include vitreous haemorrhage preventing laser photocoagulation, severe nonclearing vitreous haemorrhage, subhyaloid and premacular haemorrhage, tractional retinal detachment involving or threatening the macula, combined tractional and rhegmatogenous retinal detachment, progressive fibrovascular proliferation, clinically significant macular oedema and rubeosis iridis. Together with the increasing number of indications, timing for vitrectomy has also changed. The beneficial effect of early vitrectomy for these indications has been clinically shown and supported by several studies. The benefit is evident in case of type I diabetes and when the duration of the diabetes is less than 20 years. Long-term outcomes can therefore be improved when individualised treatment algorithms are applied.

Time to exhaustion at maximal lactate steady state is similar for cycling and running in moderately trained subjects.

We compared time to exhaustion (t(lim)) at maximal lactate steady state (MLSS) between cycling and running, investigated if oxygen consumption, ventilation, blood lactate concentration, and perceived exertion differ between the exercise modes, and established whether MLSS can be determined for cycling and running using the same criteria. MLSS was determined in 15 moderately trained men (30 +/- 6 years, 77 +/- 6 kg) by several constant-load tests to exhaustion in cycling and running. Heart rate, oxygen consumption, and ventilation were recorded continuously. Blood lactate concentration and perceived exertion were measured every 5 min. t (lim) (37.7 +/- 8.9 vs. 34.4 +/- 5.4 min) and perceived exertion (7.2 +/- 1.7 vs. 7.2 +/- 1.5) were similar for cycling and running. Heart rate (165 +/- 8 vs. 175 +/- 10 min(-1); P < 0.01), oxygen consumption (3.1 +/- 0.3 vs. 3.4 +/- 0.3 l min(-1); P < 0.001) and ventilation (93 +/- 12 vs. 103 +/- 16 l min(-1); P < 0.01) were lower for cycling compared to running, respectively, whereas blood lactate concentration (5.6 +/- 1.7 vs. 4.3 +/- 1.3 mmol l(-1); P < 0.05) was higher for cycling. t(lim) at MLSS is similar for cycling and running, despite absolute differences in heart rate, ventilation, blood lactate concentration, and oxygen consumption. This may be explained by the relatively equal cardiorespiratory demand at MLSS. Additionally, the similar t(lim) for cycling and running allows the same criteria to be used for determining MLSS in both exercise modes.