Measuring sleep quality after adenotonsillectomy in pediatric sleep apnea

OBJECTIVES/HYPOTHESIS

The aim of this study was to demonstrate postoperative changes in sleep quality in children with obstructive sleep apnea (OSA), using both conventional sleep staging and electrocardiogram-based cardiopulmonary coupling (CPC) analysis. The hypothesis is that being electroencephalography (EEG)-independent, CPC may detect changes in sleep quality that traditional sleep architecture analysis cannot.

STUDY DESIGN

Retrospective outcome research.

METHODS

We included 37 children (aged 6.89 ± 2.76 years, 28 male) with OSA who underwent adenotonsillectomy, and analyzed standard polysomnography and CPC parameters from a full-night study before and after adenotonsillectomy. High-frequency coupling (HFC) and low-frequency coupling (LFC) were used as indices of stable and unstable sleep, respectively.

RESULTS

Adenotonsillectomy led to a significant change in CPC parameters (HFC, 50.3 ± 16.1% to 56.1 ± 14.7%, P = .03; LFC, 35.1 ± 14.5% to 27.3 ± 13.0%, P = .003), which was paralleled by improvements in the apnea-hypopnea (12.7 ± 13.7 to 1.0 ± 0.8, P < .001) and arousal index (20.8 ± 11.5 to 9.9 ± 3.9, P < .001). Polysomnographic sleep stage parameters other than the arousal index did not reflect postoperative resolution of OSA.

CONCLUSIONS

In pediatric OSA, postoperative improvement of sleep quality is more readily discernible by CPC analysis than EEG-based sleep staging. The CPC analysis may have potential advantages in the assessment of sleep quality in pediatric populations.

Assessment of therapeutic options for mild obstructive sleep apnea using cardiopulmonary coupling measures

OBJECTIVES

To examine the efficacy of various therapeutic modalities for mild obstructive sleep apnea using cardiopulmonary coupling variables of sleep quality.

METHODS

A 67-year-old Caucasian subject's sleep was recorded at home for 10 nights using a type 3 sleep recording device that measured ECG and body position, followed by generation of the cardiopulmonary sleep spectrogram. Three baseline nights, one night with a sleep jacket containing 3 tennis balls to restrict sleep in the supine position, 2 nights with oxygen only delivered via a nasal cannula at a flow rate of 2 L/minute, 2 nights with a mandible advancing appliance (MAA) only, and 2 nights using oxygen at 2 L/minute with the MAA were compared.

RESULTS

Baseline sleep quality estimated using the ratio of high-frequency and low-frequency coupling (1.03) was below the expected normal adult values ranging from 1.67-4.0. The sleep quality ratio was significantly higher (2.08) using the MAA alone compared to baseline, sleep position restriction (1.61), oxygen therapy (0.81), and the combination of MAA with oxygen (1.66).

CONCLUSION

Sleep quality measured objectively using cardiopulmonary coupling variables differentiated the efficacy of therapeutic options for mild obstructive sleep apnea. Such an approach may have practical utility.

Genetic association of short sleep duration with hypertension incidence--a 6-year follow-up in the Korean genome and epidemiology study

BACKGROUND

Hypertension (HT) is caused by complex interactions between genetic and environmental factors. Despite evidence for an association between short sleep duration and the development of HT, genetic factors associated with this effect have not been defined. Here we prospectively investigated the incidence of HT in subjects with short sleep duration over a 6-year follow-up period, and identified associated genetic variants in a genome-wide association study.

METHODS AND RESULTS

Sleep duration was determined by questionnaire and 3 categories were established: <5h, 5-7h, and >7h. Genotyping was carried out using the Affymetrix Genome-Wide Human Single Nucleotide Polymorphism (SNP) Array 5.0. Of the 4,965 individuals included in our study, 1,071 (543 of 2,330 men, 528 of 2,635 women) developed HT. The cumulative incidence of HT during the 6-year study period was 21.6%. Sleep duration <5h was associated with an increased risk of incident HT only in premenopausal women (adjusted hazard ratio 2.43, 95% confidence interval 1.36-4.35). The SNPs of rs6691577, rs2226284 and rs12756253 were associated with this increased risk.

CONCLUSIONS

This prospective communitywide study showed that premenopausal women with short sleep duration had an increased risk of incident HT, and found associations with specific genomic markers.

Electrocardiogram-based sleep spectrogram measures of sleep stability and glucose disposal in sleep disordered breathing

STUDY OBJECTIVES

Sleep disordered breathing (SDB) is independently associated with insulin resistance, glucose intolerance, and type 2 diabetes mellitus. Experimental sleep fragmentation has been shown to impair insulin sensitivity. Conventional electroencephalogram (EEG)-based sleep-quality measures have been inconsistently associated with indices of glucose metabolism. This analysis explored associations between glucose metabolism and an EEG-independent measure of sleep quality, the sleep spectrogram, which maps coupled oscillations of heart-rate variability and electrocardiogram (ECG)-derived respiration. The method allows improved characterization of the quality of stage 2 non-rapid eye movement (NREM) sleep.

DESIGN

Cross-sectional study.

SETTING

N/A.

PARTICIPANTS

Nondiabetic subjects with and without SDB (n = 118) underwent the frequently sampled intravenous glucose tolerance test (FSIVGTT) and a full-montage polysomnogram. The sleep spectrogram was generated from ECG collected during polysomnography.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Standard polysomnographic stages (stages 1, 2, 3+4, and rapid eye movement [REM]) were not associated with the disposition index (D(I)) derived from the FSIVGTT. In contrast, spectrographic high-frequency coupling (a marker of stable or "effective" sleep) duration was associated with increased, and very-low-frequency coupling (a marker of wake/REM/transitions) associated with reduced D(I). This relationship was noted after adjusting for age, sex, body mass index, slow wave sleep, total sleep time, stage 1, the arousal index, and the apnea-hypopnea index.

CONCLUSIONS

ECG-derived sleep-spectrogram measures of sleep quality are associated with alterations in glucose-insulin homeostasis. This alternate mode of estimating sleep quality could improve our understanding of sleep and sleep-breathing effects on glucose metabolism.

Chemically Specific Imaging Through Stimulated Raman Photoexcitation and Ultrasound Detection: Minireview

A powerful combination of chemically specific Raman excitation and deep tissue ultrasound imaging holds the promise to attain spatially resolved distribution of chemical compounds inside the scattering medium. In this report, an attempt is made to evaluate the recent achievements and possible challenges with an eye on potential clinical applications.

Probabilistic sleep architecture models in patients with and without sleep apnea

Sleep fragmentation of any cause is disruptive to the rejuvenating value of sleep. However, methods to quantify sleep architecture remain limited. We have previously shown that human sleep-wake stage distributions exhibit multi-exponential dynamics, which are fragmented by obstructive sleep apnea (OSA), suggesting that Markov models may be a useful method to quantify architecture in health and disease. Sleep stage data were obtained from two subsets of the Sleep Heart Health Study database: control subjects with no medications, no OSA, no medical co-morbidities and no sleepiness (n = 374); and subjects with severe OSA (n = 338). Sleep architecture was simplified into three stages: wake after sleep onset (WASO); non-rapid eye movement (NREM) sleep; and rapid eye movement (REM) sleep. The connectivity and transition rates among eight 'generator' states of a first-order continuous-time Markov model were inferred from the observed ('phenotypic') distributions: three exponentials each of NREM sleep and WASO; and two exponentials of REM sleep. Ultradian REM cycling was accomplished by imposing time-variation to REM state entry rates. Fragmentation in subjects with severe OSA involved faster transition probabilities as well as additional state transition paths within the model. The Markov models exhibit two important features of human sleep architecture: multi-exponential stage dynamics (accounting for observed bout distributions); and probabilistic transitions (an inherent source of variability). In addition, the model quantifies the fragmentation associated with severe OSA. Markov sleep models may prove important for quantifying sleep disruption to provide objective metrics to correlate with endpoints ranging from sleepiness to cardiovascular morbidity.

Expansion of human mesenchymal stem cells on microcarriers

The effects on human mesenchymal stem cell growth of choosing either of two spinner flask impeller geometries, two microcarrier concentrations and two cell concentrations (seeding densities) were investigated. Cytodex 3 microcarriers were not damaged when held at the minimum speed, N(JS), for their suspension, using either impeller, nor was there any observable damage to the cells. The maximum cell density was achieved after 8-10 days of culture with up to a 20-fold expansion in terms of cells per microcarrier. An increase in microcarrier concentration or seeding density generally had a deleterious or neutral effect, as previously observed for human fibroblast cultures. The choice of impeller was significant, as was incorporation of a 1 day delay before agitation to allow initial attachment of cells. The best conditions for cell expansion on the microcarriers in the flasks were 3,000 microcarriers ml(-1) (ca. 1 g dry weight l(-1)), a seeding density of 5 cells per microcarrier with a 1 day delay before agitation began at N(JS) (30 rpm), using a horizontally suspended flea impeller with an added vertical paddle. These findings were interpreted using Kolmogorov's theory of isotropic turbulence.

Classification algorithms for predicting sleepiness and sleep apnea severity

Identifying predictors of subjective sleepiness and severity of sleep apnea are important yet challenging goals in sleep medicine. Classification algorithms may provide insights, especially when large data sets are available. We analyzed polysomnography and clinical features available from the Sleep Heart Health Study. The Epworth Sleepiness Scale and the apnea-hypopnea index were the targets of three classifiers: k-nearest neighbor, naive Bayes and support vector machine algorithms. Classification was based on up to 26 features including demographics, polysomnogram, and electrocardiogram (spectrogram). Naive Bayes was best for predicting abnormal Epworth class (0-10 versus 11-24), although prediction was weak: polysomnogram features had 16.7% sensitivity and 88.8% specificity; spectrogram features had 5.3% sensitivity and 96.5% specificity. The support vector machine performed similarly to naive Bayes for predicting sleep apnea class (0-5 versus >5): 59.0% sensitivity and 74.5% specificity using clinical features and 43.4% sensitivity and 83.5% specificity using spectrographic features compared with the naive Bayes classifier, which had 57.5% sensitivity and 73.7% specificity (clinical), and 39.0% sensitivity and 82.7% specificity (spectrogram). Mutual information analysis confirmed the minimal dependency of the Epworth score on any feature, while the apnea-hypopnea index showed modest dependency on body mass index, arousal index, oxygenation and spectrogram features. Apnea classification was modestly accurate, using either clinical or spectrogram features, and showed lower sensitivity and higher specificity than common sleep apnea screening tools. Thus, clinical prediction of sleep apnea may be feasible with easily obtained demographic and electrocardiographic analysis, but the utility of the Epworth is questioned by its minimal relation to clinical, electrocardiographic, or polysomnographic features.

Monitoring stimulated Raman scattering with photoacoustic detection

A capability of high-frequency ultrasound detection to monitor the process of energy deposition into a molecular system via Raman excitation is experimentally demonstrated. It is shown that the generated ultrasound signal is directly proportional to the optical signal generated in stimulated Raman scattering. Ultrasound detection provides a simple way to discriminate against laser-induced breakdown and allows for the quantification of the stimulated Raman scattering process where direct optical detection is not available. Additionally, it can be used for stimulated Raman imaging in deep tissue, provided that the generated photoacoustic signal is sufficiently strong.

Spatially correlated microthermography maps threshold temperature in laser-induced damage

We measured threshold temperatures for cell death resulting from short (0.1-1.0 s) 514-nm laser exposures using an in vitro retinal model. Real-time thermal imaging at sub-cellular resolution provides temperature information that is spatially correlated with cells at the boundary of cell death, as indicate by post-exposure fluorescence images. Our measurements indicate markedly similar temperatures, not only around individual boundaries (single exposure), but among all exposures of the same duration in a laser irradiance-independent fashion. Two different methods yield similar threshold temperatures with low variance. Considering the experimental uncertainties associated with the thermal camera, an average peak temperature of 53 ± 2 °C is found for laser exposures of 0.1, 0.25, and 1.0 s. Additionally, we find a linear relationship between laser exposure duration and time-averaged integrated temperature. The mean thermal profiles for cells at the boundary of death were assessed using the Arrhenius rate law using parameter sets (frequency factor and energy of activation) found in three different articles.

Mathematical model that describes the transition from thermal to photochemical damage in retinal pigment epithelial cell culture

We propose a rate process model for describing photochemical damage to retinal cells by short wavelength laser exposures. The rate equation for photochemical damage contains a positive rate that is temperature independent, and a negative (quenching) rate that is temperature dependent. Using the traditional Arrhenius integral to describe thermal damage, we derive damage threshold doses for both thermal and photochemical mechanisms, and show that the model accounts for the sharp transition from thermal to photochemical damage thresholds that have recently been observed in an in-vitro retinal model.

Current understanding and challenges in bioprocessing of stem cell-based therapies for regenerative medicine

BACKGROUND

A novel manufacturing industry is emerging to translate unique cellular therapy bioprocesses to robust, scaled manufacturing production for successful clinical translation.

SOURCE OF DATA

This review summarizes key translational issues, and current and future perspectives to improve translation of cell-based therapy bioprocessing, based on literature search and author research.

AREAS OF AGREEMENT

It is widely recognized that cell-based therapies could revolutionize health care for a range of diseases, and that there are gaps in the overarching framework and technologies to generate clinical success.

AREAS OF CONTROVERSY

There is limited understanding of how to fulfil requirements as regulatory and manufacturing guidelines are incomplete and few have achieved commercialization.

GROWING POINTS

Recent developments are encouraging adoption of automation and quality engineering approaches for bioprocessing of cell-based therapies.

AREAS TIMELY FOR DEVELOPING RESEARCH

Include technology development to improve the cost and purity of manufacture and final product quality.

Detecting mineral content in turbid medium using nonlinear Raman imaging: feasibility study

Osteoporosis is a bone disease characterized by reduced mineral content with resulting changes in bone architecture, which in turn increases the risk of bone fracture. Raman spectroscopy has an intrinsic sensitivity to the chemical content of the bone, but its application to study bones in vivo is limited due to strong optical scattering in tissue. It has been proposed that Raman excitation with photoacoustic detection can successfully address the problem of chemically specific imaging in deep tissue. In this report, the principal possibility of photoacoustic imaging for detecting mineral content is evaluated.

Infrared skin damage thresholds from 1940-nm continuous-wave laser exposures

A series of experiments are conducted in vivo using Yucatan mini-pigs (Sus scrofa domestica) to determine thermal damage thresholds to the skin from 1940-nm continuous-wave thulium fiber laser irradiation. Experiments employ exposure durations from 10 ms to 10 s and beam diameters of approximately 4.8 to 18 mm. Thermal imagery data provide a time-dependent surface temperature response from the laser. A damage endpoint of minimally visible effect is employed to determine threshold for damage at 1 and 24 h postexposure. Predicted thermal response and damage thresholds are compared with a numerical model of optical-thermal interaction. Results are compared with current exposure limits for laser safety. It is concluded that exposure limits should be based on data representative of large-beam exposures, where effects of radial diffusion are minimized for longer-duration damage thresholds.

In-vitro retinal model reveals a sharp transition between laser damage mechanisms

We use laser damage thresholds in an in-vitro retinal model, and computational simulations to examine the laser exposure durations at which damage transitions from photothermal to photochemical at 413 nm. Our results indicate a dramatic shift in 1-h damage thresholds between exposure durations of 60 and 100 s. The trend in our in-vitro results is similar to a trend found in a recent study where retinal lesions were assessed 1-h post laser exposure in the rhesus eye Our data suggest that nonthermal mechanisms did not significantly contribute to cell death, even for exposures of 60 s. Knowledge of the transition point, and lack of concurrent thermal and nonthermal damage processes, are significant for those wishing to devise a comprehensive computational damage model.

Heritability of abnormalities in cardiopulmonary coupling in sleep apnea: use of an electrocardiogram-based technique

RATIONALE

Studies of the genetics of obstructive sleep apnea may be facilitated by identifying intermediate traits with high heritability that quantify etiological pathways, such as those related to respiratory control. Electrocardiogram (ECG)-based sleep spectrograms, measuring the coupling between respiratory modulation of ECG QRS-wave amplitude and heart rate variability, may provide measures of sleep state and ventilatory dynamics during sleep. We evaluated the familial aggregation of distinctive spectrographic biomarkers of unstable sleep, related to elevated-low frequency cardiopulmonary coupling (e-LFC), to assess their utility in genetic studies.

METHODS

622 participants from 137 families from the Cleveland Family Study underwent standardized polysomnography (PSG). From the ECG signal on the PSG, the interbeat interval time series and the corresponding ECG-derived respiratory signal were extracted, and the low frequency (0.01-0.1 Hz) component of their coupling was computed using a fully automated method. Narrow sense heritability of e-LFC was calculated using variance component methods.

RESULTS

A spectral marker of abnormal low frequency cardiopulmonary coupling (e-LFC) demonstrated moderate correlation with apnea hypopnea index (AHI; r = 0.35, P < 0.0001). The heritability estimate for e-LFC, after adjusting for age and sex was 0.32 (P < 10-5) and remained unchanged after additionally adjusting for body mass index or AHI. In biological relatives of those with sleep apnea, a related marker of e-LFC was more prevalent than in controls (P = 0.05).

CONCLUSIONS

Approximately 30% of the variability of e-LFC, measured from a continuous ECG during sleep, is explained by familial factors other than BMI. ECG-based spectrographic measures of cardiopulmonary coupling may provide novel phenotypes for characterizing subgroups of individuals with different propensities and genetic etiologies for sleep apnea or for other conditions associated with sleep fragmentation.

Epidermal laser stimulation of action potentials in the frog sciatic nerve

Measurements of laser-stimulated action potentials in the sciatic nerve of leopard frogs (Rana pipiens) are made using two infrared lasers. The dorsal sides of the frog's hind limbs are exposed to short-pulsed 1540- and 1064-nm wavelengths at three separate spot sizes: 2, 3, and 4 mm. Energy density thresholds are determined for eliciting an action potential at each experimental condition. Results from these exposures show similar evoked potential thresholds for both wavelengths. The 2-mm-diam spot sizes yield action potentials at radiant exposure levels almost double that seen with larger beam sizes.