An association between heart rate variability and pediatric obstructive sleep apnea

BACKGROUND

There are different findings on heart rate variability (HRV) and pediatric obstructive sleep apnea (pOSA) by an overnight HRV or a 1-hr HRV. However, there is limited data of HRV and pOSA diagnosis by using a 24-h HRV test. This study aimed to evaluate if HRV had potential for OSA diagnosis by using a 24-h HRV test.

METHODS

This was a prospective study included children age between 5 and 15 years old, presenting with snoring, underwent polysomnography and a 24-h Holter monitoring. Predictors for pOSA diagnosis were analyzed using logistic regression analysis.

RESULTS

During the study period, there were 81 pediatric patients met the study criteria. Of those, 65 patients (80.25%) were diagnosed as OSA. There were three factors were independently associated with OSA: standard deviation of all normal interval (SDNN), high frequency (HF), and low frequency (LF). The adjusted odds ratios of these factors were 0.949 (95% confidence interval 0.913, 0.985), 0.786 (95% confidence interval 0.624, 0.989), and 1.356 (95% confidence interval 1.075, 1.709).

CONCLUSIONS

HRV parameters including SDNN, HF, and LF were associated with pOSA diagnosis in children by using the 24-h Holter monitoring.

Polymer self-assembly guided heterogeneous structure engineering towards high-performance low-frequency electromagnetic wave absorption

Magnetic-dielectric synergy is currently regarded as among the most effective approaches to achieve low-frequency electromagnetic wave absorption (EMA). However, designing and fabricating EMA materials with tunable magnetic-dielectric balance towards high-performance low-frequency EMA remains challenging. Herein, a polymer self-assembly guided heterogeneous structure engineering strategy is proposed to fabricate hierarchical magnetic-dielectric nanocomposite. Polymer assemblies not only can be employed as intermediates to encapsulate metal-organic frameworks and load metal hydroxide, but also that they play a crucial role for the in-situ formation of polycrystalline FeCo/Co composite nanoparticles. As a result, the minimum reflection loss (RLmin) can reach -59.61 dB at 5.4 GHz (4.8 mm) with a 20 wt% filler loading, while the effective absorption bandwidth (EAB, RLmin ≤ -10 dB) is 2.16 GHz, exhibiting excellent low-frequency EMA performance. Systematic investigations demonstrate that hierarchical mesoporous carbon matrix that supports FeCo/Co composite nanoparticles is beneficial for optimizing impedance matching and increasing attenuation capacity. In general, this study opens up new prospects for developing magnetic-dielectric EMA materials using a polymer self-assembly guided heterogeneous structure engineering strategy, which may receive significant attention in future research.

Subthalamic 85 Hz deep brain stimulation improves walking pace and stride length in Parkinson's disease patients

BACKGROUND

Mobile gait sensors represent a compelling tool to objectify the severity of symptoms in patients with idiopathic Parkinson's disease (iPD), but also to determine the therapeutic benefit of interventions. In particular, parameters of Deep Brain stimulation (DBS) with its short latency could be accurately assessed using sensor data. This study aimed at gaining insight into gait changes due to different DBS parameters in patients with subthalamic nucleus (STN) DBS.

METHODS

An analysis of various gait examinations was performed on 23 of the initially enrolled 27 iPD patients with chronic STN DBS. Stimulation settings were previously adjusted for either amplitude, frequency, or pulse width in a randomised order. A linear mixed effects model was used to analyse changes in gait speed, stride length, and maximum sensor lift.

RESULTS

The findings of our study indicate significant improvements in gait speed, stride length, and leg lift measurable with mobile gait sensors under different DBS parameter variations. Notably, we observed positive results at 85 Hz, which proved to be more effective than often applied higher frequencies and that these improvements were traceable across almost all conditions. While pulse widths did produce some improvements in leg lift, they were less well tolerated and had inconsistent effects on some of the gait parameters. Our research suggests that using lower frequencies of DBS may offer a more tolerable and effective approach to enhancing gait in individuals with iPD.

CONCLUSIONS

Our results advocate for lower stimulation frequencies for patients who report gait difficulties, especially those who can adapt their DBS settings remotely. They also show that mobile gait sensors could be incorporated into clinical practice in the near future.

Towards Characterization of Skin Melanoma in the Clinic by Electron Paramagnetic Resonance (EPR) Spectroscopy and Imaging of Melanin

The incidence of melanoma is continuously increasing over time. Melanoma is the most aggressive skin cancer, significantly reducing quality of life and survival rates of patients at advanced stages. Therefore, early diagnosis remains the key to change the prognosis of patients with melanoma. In this context, advanced technologies are under evaluation to increase the accuracy of the diagnostic, to better characterize the lesions and visualize their possible invasiveness in the epidermis. Among the innovative methods, because melanin is paramagnetic, clinical low frequency electron paramagnetic resonance (EPR) that characterizes the melanin content in the lesion has the potential to be an adjunct diagnostic method of melanoma. In this review, we first summarize the challenges faced by dermatologists and oncologists in melanoma diagnostic and management. We also provide a historical perspective on melanin detection with a focus on EPR spectroscopy/imaging of melanomas. We describe key elements that allow EPR to move from in vitro studies to in vivo and finally to patients for melanoma studies. Finally, we provide a critical view on challenges to meet to make EPR operational in the clinic to characterize pigmented lesions.

Measurement of Frontal Midline Theta Oscillations using OPM-MEG

Optically pumped magnetometers (OPMs) are an emerging lightweight and compact sensor that can measure magnetic fields generated by the human brain. OPMs enable construction of wearable magnetoencephalography (MEG) systems, which offer advantages over conventional instrumentation. However, when trying to measure signals at low frequency, higher levels of inherent sensor noise, magnetic interference and movement artefact introduce a significant challenge. Accurate characterisation of low frequency brain signals is important for neuroscientific, clinical, and paediatric MEG applications and consequently, demonstrating the viability of OPMs in this area is critical. Here, we undertake measurement of theta band (4-8 Hz) neural oscillations and contrast a newly developed 174 channel triaxial wearable OPM-MEG system with conventional (cryogenic-MEG) instrumentation. Our results show that visual steady state responses at 4 Hz, 6 Hz and 8 Hz can be recorded using OPM-MEG with a signal-to-noise ratio (SNR) that is not significantly different to conventional MEG. Moreover, we measure frontal midline theta oscillations during a 2-back working memory task, again demonstrating comparable SNR for both systems. We show that individual differences in both the amplitude and spatial signature of induced frontal-midline theta responses are maintained across systems. Finally, we show that our OPM-MEG results could not have been achieved without a triaxial sensor array, or the use of postprocessing techniques. Our results demonstrate the viability of OPMs for characterising theta oscillations and add weight to the argument that OPMs can replace cryogenic sensors as the fundamental building block of MEG systems.

Acoustic radiation force dependence on properties of elastic spherical shells in standing waves

In this study, we theoretically investigate the acoustic radiation force acting on elastic spherical shells in standing waves in the dimensionless frequency range of 0<ka<0.7 (k is the wave number in the host fluid and a is the outer radius of the spherical shells), we show that in the low-frequency range (0<ka<0.2), the acoustic radiation force on core-shell spheres can vary from positive to negative by decreasing the effective density and effective bulk modulus of the spherical shells, while the effective density and bulk modulus are dependent on the hollow ratio of the core-shell spheres, the density and bulk modulus ratios of the shell to the core. Thus, the core-shell spheres cannot only be trapped from the pressure node to the pressure antinode by increasing the hollow ratio or decreasing the shell's density or longitudinal or shear velocity, but are also unresponsive to ultrasound waves with an optimal hollow ratio, density, or acoustic velocity of the shell. We further show that in the relatively low-frequency range of0<ka<0.7, the acoustic radiation force on core-shell spheres can be significantly enhanced around resonant frequencies. The acoustic radiation force could be enhanced at lower frequencies by increasing the hollow ratio or decreasing the shell's density or shear wave velocity. Our results pave the way for optimising the design of core-shell particles for efficient ultrasound-mediated drug delivery.

Efficacy optimization of low frequency microbubble-mediated sonoporation as a drug delivery platform to cancer cells

Ultrasound insonation of microbubbles can be used to form pores in cell membranes and facilitate the local trans-membrane transport of drugs and genes. An important factor in efficient delivery is the size of the delivered target compared to the generated membrane pores. Large molecule delivery remains a challenge, and can affect the resulting therapeutic outcomes. To facilitate large molecule delivery, large pores need to be formed. While ultrasound typically uses megahertz frequencies, it was recently shown that when microbubbles are excited at a frequency of 250 kHz (an order of magnitude below the resonance frequency of these agents), their oscillations are significantly enhanced as compared to the megahertz range. Here, to promote the delivery of large molecules, we suggest using this low frequency and inducing large pore formation through the high-amplitude oscillations of microbubbles. We assessed the impact of low frequency microbubble-mediated sonoporation on breast cancer cell uptake by optimizing the delivery of 4 fluorescent molecules ranging from 1.2 to 70 kDa in size. The optimal ultrasound peak negative pressure was found to be 500 kPa. Increasing the pressure did not enhance the fraction of fluorescent cells, and in fact reduced cell viability. For the smaller molecule sizes, 1.2 kDa and 4 kDa, the groups treated with an ultrasound pressure of 500 kPa and MB resulted in a fraction of 58% and 29% of fluorescent cells respectively, whereas delivery of 20 kDa and 70 kDa molecules yielded 10% and 5%, respectively. These findings suggest that low-frequency (e.g., 250 kHz) insonation of microbubbles results in high amplitude oscillation in vitro that increase the uptake of large molecules. Successful ultrasound-mediated molecule delivery requires the careful selection of insonation parameters to maximize the therapeutic effect by increasing cell uptake.

Design and Construction of a Low-Frequency Ultrasound Acquisition Device for 2-D Brain Imaging Using Full-Waveform Inversion

The main techniques used to image the brain and obtain structural data are magnetic resonance imaging and X-ray computed tomography. These techniques produce images with high spatial resolution, but with the disadvantage of requiring very large equipment with special installation needs. In addition, X-ray tomography uses ionizing radiation, which limits their use. Ultrasound imaging is a safe technology that is delivered using compact and mobile devices. However, conventional ultrasound reconstruction techniques have failed to obtain images of the brain because of, fundamentally, the presence of the skull and the distortion that it produces on ultrasound. Recent studies have indicated that full-waveform inversion, a computational technique originally from Earth science, has the potential to generate accurate 3-D images of the brain. This technology can overcome the limitations of conventional ultrasound imaging, but a prototype for transcranial applications does not yet exist. Here, we investigate different designs of an annular array of ultrasound transducers to optimize the number of elements and rotations needed to conduct transcranial imaging with full-waveform inversion. This device uses small-diameter, low-frequency transducers that readily propagate ultrasound through the skull with good signal-to-noise ratios. It also incorporates the use of rotations to produce a high-density coverage of the target and acquire redundant traces that are beneficial for full-waveform inversion. We have built a ring of 40 transducers to illustrate that this design is capable of reconstructing images of the brain, retrieving its anatomy and acoustic properties with millimeter resolution. Laboratory results reveal the ability of this device to successfully image a 2.5-D brain- and skull-mimicking phantom using full-waveform inversion. To our knowledge, this is the first prototype ever used for transcranial-like imaging. The importance of these findings and their implications for the design of a 3-D reconstruction system with possible clinical applications are discussed.

Numerical investigation of vibration and noise radiation of a water supply pipeline

The vibration and noise radiation from underwater structures can be harmful for aquatic ecosystems, especially for endangered species which are sensitive to particle motion and sound pressure. In this study, a water supply pipeline was chosen to investigate the flow-induced vibration and underwater noise radiation. A finite element model was developed to predict the vibration of the pipeline-tunnel-soil coupling system using fluid-structure interaction analysis. Next, a three-demission boundary element acoustic model was developed to simulate underwater noise radiation and propagation. Parametric analysis was conducted to investigate the influence of scouring depth on vibration and acoustic radiation. The results showed the flowing fluid-induced vibration produced broad band noise radiation, with dominant frequency range from 3 to 25 Hz. The sound pressure radiated from the model with once-in-a-century scouring depth was about 3 dB larger than the model with normal depth due to thinner sediment. The sourcing depth has significant influence on the noise distribution and radiation directivity. The simulated sound pressure level and water particle motion can exceed the threshold of some underwater species in certain frequency range, especially for the once-in-a-century scouring depth. The proposed methodology can be used for acoustic radiation prediction in further study to reduce the influence on aquatic environment.

Mechanistically informed non-invasive peripheral nerve stimulation for peripheral neuropathic pain: a randomised double-blind sham-controlled trial

BACKGROUND

Induction of long-term synaptic depression (LTD) is proposed as a treatment mechanism for chronic pain but remains untested in clinical populations. Two interlinked studies; (1) A patient-assessor blinded, randomised, sham-controlled clinical trial and (2) an open-label mechanistic study, sought to examine therapeutic LTD for persons with chronic peripheral nerve injury pain.

METHODS

(1) Patients were randomised using a concealed, computer-generated schedule to either active or sham non-invasive low-frequency nerve stimulation (LFS), for 3 months (minimum 10 min/day). The primary outcome was average pain intensity (0-10 Likert scale) recorded over 1 week, at 3 months, compared between study groups. (2) On trial completion, consenting subjects entered a mechanistic study assessing somatosensory changes in response to LFS.

RESULTS

(1) 76 patients were randomised (38 per group), with 65 (31 active, 34 sham) included in the intention to treat analysis. The primary outcome was not significant, pain scores were 0.3 units lower in active group (95% CI - 1.0, 0.3; p = 0.30) giving an effect size of 0.19 (Cohen's D). Two non-device related serious adverse events were reported. (2) In the mechanistic study (n = 19) primary outcomes of mechanical pain sensitivity (p = 0.006) and dynamic mechanical allodynia (p = 0.043) significantly improved indicating reduced mechanical hyperalgesia.

CONCLUSIONS

Results from the RCT failed to reach significance. Results from the mechanistic study provide new evidence for effective induction of LTD in a clinical population. Taken together results add to mechanistic understanding of LTD and help inform future study design and approaches to treatment. Trial registration ISRCTN53432663.

Fast and slow effective waves across dilute random distributions of elastic spheres in a poroelastic medium

A dilute random distribution of identical elastic spheres in a poroelastic isotropic matrix obeying Biot's theory is considered. Using Luppe, Conoir and Norris (LCN) multiple scattering formula up to the corrective second order term in concentration, approximations are sought in the low frequency domain (Rayleigh limit) for the fast and slow effective wavenumbers. The contribution of the corrective second order term - which contains the coupling (i.e. mode conversions) between the fast, slow and shear waves and accounts for multiple scattering - is discussed. Considering the fast and slow wavenumbers, some effective quantities (bulk modulus, mass density and diffusion coefficient) are estimated.

Redox and autonomic responses to acute exercise-post recovery following Opuntia ficus-indica juice intake in physically active women

BACKGROUND

The aim of this study was to investigate if the supplementation with Opuntia ficus-indica (OFI) juice may affect plasma redox balance and heart rate variability (HRV) parameters following a maximal effort test, in young physically active women.

METHODS

A randomized, double blind, placebo controlled and crossover study comprising eight women (23.25 ± 2.95 years, 54.13 ± 9.05 kg, 157.75 ± 0.66 cm and BMI of 21.69 ± 0.66 kg/m2) was carried out. A juice containing OFI diluted in water and a Placebo solution were supplied (170 ml; OFI = 50 ml of OFI juice + 120 ml of water; Placebo = 170 ml beverage without Vitamin C and indicaxanthin). Participants consumed the OFI juice or Placebo beverage every day for 3 days, before performing a maximal cycle ergometer test, and for 2 consecutive days after the test. Plasma hydroperoxides and total antioxidant capacity (PAT), Skin Carotenoid Score (SCS) and HRV variables (LF, HF, LF/HF and rMSSD) were recorded at different time points.

RESULTS

The OFI group showed significantly lower levels of hydroperoxides compared to the Placebo group in pre-test, post-test and 48-h post-test. PAT values of the OFI group significantly increased compared to those of the Placebo group in pre-test and 48-h post-test. SCS did not differ between groups. LF was significantly lower in the OFI group 24-h after the end of the test, whereas rMSSD was significantly higher in the OFI group 48-h post-test.

CONCLUSION

OFI supplementation decreased the oxidative stress induced by intense exercise and improved autonomic balance in physically active women.

Experimental and numerical study on underwater noise radiation from an underwater tunnel

The hydro-acoustic noise radiating from underwater tunnels during vehicle passage may be harmful to aquatic fauna, and this is a particular concern for endangered species. Therefore, the effects of underwater noise radiation and propagation on aquatic biodiversity must be investigated. In this study, the dynamic response of the sediment and tunnel structure in the Yangtze River in China was explored by conducting a field test, and the associated noise radiation from the tunnel was recorded and investigated. A three-dimensional numerical model was then developed to simulate the vibration of the tunnel-sediment coupling system induced by random traffic-flow models. Next, a modal acoustic transfer vector-based method was used to predict underwater noise radiation by use of a three-dimensional finite-element acoustic model. Finally, the accuracy of the simulated results was verified by comparison with measurements. The results showed that the noise radiation induced by passing vehicles was approximately 14 dB greater than the background noise, with a main frequency range of 12-25 Hz. The random traffic-flow model had obvious influence of the simulated noise level above 20 Hz. Vehicle-induced underwater noise may thus have a direct effect on fish species that can perceive low-frequency sound pressure. The proposed method can be used for further investigation of methods to reduce the effect of underwater noise on aquatic fauna, especially endangered species.

[Analysis of prognostic factors of low-frequency type of sudden sensorineural hearing loss]

Objective: To investigate the prognostic factors of patients with low-frequency type of sudden sensorineural hearing loss. Methods: From February 2017 to February 2019, adult patients with unilateral low-frequency type of sudden sensorineural hearing loss in Department of Otological Medicine, Shandong Provincial ENT Hospital, Shandong University were selected. All patients were examined by audiology, vestibular function evaluation, imaging examination and serum thyroid function test; the same treatment program was given, the curative effect was recorded and followed up for more than 3 months. SPSS 20.0 software was used to analyze concomitant symptoms (tinnitus, ear tightness, echo, rotatory vertigo), degree of deafness, inducement of deafness, basic disease, vestibular function (caloric test), electrocochleogram, inner ear gadolinium enhanced MRI radiography and thyroid function on prognosis of patients. Results: Among the 155 patients, 76 cases were cured (49.0%), 1 case was markedly effective (0.6%), 19 cases were effective (12.3%), and 59 cases were ineffective (38.1%). The total effective rate was 61.9%. Among them, 24 cases (15.5%) had hearing fluctuations during follow-up, and 1 case (0.6%) developed Meniere's disease. Univariate analysis showed that vestibular function, electrocochleogram and inner ear MRI were correlated with prognosis. Multivariate logistic analysis showed that ear tightness, vestibular function, electrocochleogram and inner ear MRI were correlated with the prognosis of the patients. The two analyses showed that tinnitus, echo, rotational vertigo, degree of deafness, predisposing factors and underlying diseases were not significantly correlated with the prognosis of the patients (all P>0.05). Rotational vertigo was closely related to gender, and women had a high incidence. There was a significant correlation between the degree of deafness and prognosis in patients with course of less than 1 week (P<0.05). The abnormal rate of vestibular function in patients with course of disease ≤ 1 week was significantly different from that>1-≤2 and>2-≤4 weeks (P<0.05). The rate of abnormal thyroid function was significantly higher than that of normal people (P<0.05), but there was no significant correlation between thyroid dysfunction and hearing prognosis (χ(2)=0.009, P=0.923) . Conclusions: The prognosis of low-frequency sudden sensorineural hearing loss is not related to clinical symptoms, inducements, underlying diseases and serological abnormalities of thyroid function, but the degree of deafness is positively related to the prognosis within 1 week from onset. Abnormal thyroid function is one of the risk factors of happening with low-frequency descending sudden deafness. Abnormal vestibular caloric test, electrocochleogram and endolymph hydrops are the factors of poor prognosis.

TERT-rs33963617 and CLPTM1L-rs77518573 reduce the risk of non-small cell lung cancer in Chinese population

BACKGROUND

Genome-wide association studies (GWAS) have identified 5p15.33 as a susceptible locus for lung cancer. However, for non-small cell lung cancer (NSCLC), low-frequency risk variants in this region have not been systematically studied. We intended to explore the associations between low-frequency variants on 5p15.33 and NSCLC using a next-generation sequencing based approach in this study.

METHODS

We have acquisited the variation spectrum of 400 NSCLC patients on 5p15.33 by sequencing the targeted region before. Candidate variants were primarily selected by restricting the minor allele frequency (MAF 1-5%) and then by comparing their frequency in 400 NSCLC patients with 1008 East Asians from The genome Aggregation Database (gnomAD). The associations between candidate variants and NSCLC were discovered and replicated in two case-control sets: discovery stage with 960 cases and 916 controls, and replication stage with 1596 cases and 1614 controls in total.

RESULTS

Five low-frequency variants were selected as our candidates and subsequent association analyses showed that 2 polymorphisms were significantly associated with risk of NSCLC, including rs33963617 (OR = 0.63, 95% CI: 0.53-0.76, P = 3.80 × 10^-7) in TERT and rs77518573 (OR = 0.73, 95% CI: 0.63-0.84, P = 2.00 × 10^-5) in upstream of CLPTM1L. When stratified by histologic subtype, a significant association was only investigated in adenocarcinoma for rs77518573. We also observed an obvious cumulative effect of the two significant variants.

CONCLUSIONS

We newly identified two NSCLC related variants on chromosome 5p15.33. Both TERT-rs33963617 and CLPTM1L-rs77518573 conferred reduced risk for NSCLC in Chinese Han population.

Using extracellular low frequency signals to improve the spike sorting of cerebellar complex spikes

BACKGROUND

The challenge of spike sorting has been addressed by numerous electrophysiological studies. These methods tend to focus on the information conveyed by the high frequencies, but ignore the potentially informative signals at lower frequencies. Activation of Purkinje cells in the cerebellum by input from the climbing fibers results in a large amplitude dendritic spike concurrent with a high-frequency burst known as a complex spike. Due to the variability in the high-frequency component of complex spikes, previous methods have struggled to sort these complex spikes in an accurate and reliable way. However, complex spikes have a prominent extracellular low-frequency signal generated by the input from the climbing fibers, which can be exploited for complex spike sorting.

NEW METHOD

We exploited the low-frequency signal (20-400 Hz) to improve complex spike sorting by applying Principal Component Analysis (PCA).

RESULTS AND COMPARISONS

The low-frequency first PC achieves a better separation of the complex spikes from noise. The low-frequency data facilitate the detection of events entering into the analysis, and therefore can be harnessed to analyze the data with a larger signal to noise ratio. These advantages make this method more effective for complex spike sorting than methods restricted to the high-frequency signal (> 600 Hz).

CONCLUSIONS

Gathering low frequency data can improve spike sorting. This is illustrated for the case of complex spikes in the cerebellum. Our characterization of the dendritic low-frequency components of complex spikes can be applied elsewhere to gain insights into processing in the cerebellum.

Enhanced osteogenesis of bone marrow stem cells cultured on hydroxyapatite/collagen I scaffold in the presence of low-frequency magnetic field

As a non-invasive biophysical therapy, electromagnetic fields (EMF) have been widely used to promote the healing of fractures. In the present study, hydroxyapatite/collagen I (HAC) loaded with rabbit bone marrow mesenchymal stem cells (MSCs) were cultured in a dynamic perfusion bioreactor and exposed to EMF of 15 Hz/1mT. Osteogenic differentiation of the seeded cells was analyzed through the evaluation of ALP activity and osteogenesis-related genes expression in vitro. The in vivo osteogenesis efficacy of the cell laden HAC constructs treated with/without EMF was evaluated through a rabbit femur condyle defect model. The results showed that EMF of 15 Hz/1mT could enhance the osteogenic differentiation of the cells seeded on HAC scaffold. Furthermore, the in vivo experiments demonstrated that EMF exposure could promote bone regeneration within the defect and bone integration between the graft and host bone. Taking together, the MSCs seeded HAC scaffold combined with EMF exposure could be a promising approach for bone tissue engineering.

Validity of Commonly Used Heart Rate Variability Markers of Autonomic Nervous System Function

BACKGROUND

Despite strong reservations regarding the validity of a number of heart rate variability (HRV) measures, these are still being used in recent studies.

AIMS

We aimed to compare the reactivity of ostensible sympathetic HRV markers (low and very low frequency [LF and VLF]) to that of electrodermal activity (EDA), an exclusively sympathetic marker, in response to cognitive and orthostatic stress, investigate the possibility of LF as a vagal-mediated marker of baroreflex modulation, and compare the ability of HRV markers of parasympathetic function (root mean square of successive differences [RMSSD] and high frequency [HF]) to quantify vagal reactivity to cognitive and orthostatic stress.

RESULTS

None of the purported sympathetic HRV markers displayed a reactivity that correlated with electrodermal reactivity. LF (ms2) reactivity correlated with the reactivity of both RMSSD and HF during baroreflex modulation. RMSSD and HF indexed the reactivity of the parasympathetic nervous system under conditions of normal breathing; however, RMSSD performed better as a marker of vagal activity when the task required breathing changes.

CONCLUSIONS

Neither LF (in ms2 or normalized units [nu]) nor VLF represent cardiac sympathetic modulation of the heart. LF (ms2) may reflect vagally mediated baroreflex cardiac effects. HRV linear analysis therefore appears to be restricted to the determination of vagal influences on heart rate. With regard to HRV parasympathetic markers, this study supports the suggestion that HRV frequency domain analyses, such as HF, should not be used as an index of vagal activity in study tasks where verbal responses are required, as these responses may induce respiratory changes great enough to distort HF power.

Taste the Bass: Low Frequencies Increase the Perception of Body and Aromatic Intensity in Red Wine

Associations between heaviness and bass/low-pitched sounds reverberate throughout music, philosophy, literature, and language. Given that recent research into the field of cross-modal correspondences has revealed a number of robust relationships between sound and flavour, this exploratory study was designed to investigate the effects of lower frequency sound (10 Hz to 200 Hz) on the perception of the mouthfeel character of palate weight/body. This is supported by an overview of relevant cross-modal studies and cultural production. Wines were the tastants - a New Zealand Pinot Noir and a Spanish Garnacha - which were tasted in silence and with a 100 Hz (bass) and a higher 1000 Hz sine wave tone. Aromatic intensity was included as an additional character given suggestions that pitch may influence the perception of aromas, which might presumably affect the perception of wine body. Intensity of acidity and liking were also evaluated. The results revealed that the Pinot Noir wine was rated as significantly fuller-bodied when tasted with a bass frequency than in silence or with a higher frequency sound. The low frequency stimulus also resulted in the Garnacha wine being rated as significantly more aromatically intense than when tasted in the presence of the higher frequency auditory stimulus. Acidity was rated considerably higher with the higher frequency in both wines by those with high wine familiarity and the Pinot Noir significantly better liked than the Garnacha. Possible reasons as to why the tones used in this study affected perception of the two wines differently are discussed. Practical application of the findings are also proposed.

Fast, Low-Frequency Plane-Wave Imaging for Ultrasound Contrast Imaging

Plane-wave ultrasound contrast imaging offers a faster, less destructive means for imaging microbubbles compared with traditional ultrasound imaging. Even though many of the most acoustically responsive microbubbles have resonant frequencies in the lower-megahertz range, higher frequencies (>3 MHz) have typically been employed to achieve high spatial resolution. In this work we implement and optimize low-frequency (1.5-4 MHz) plane-wave pulse inversion imaging on a commercial, phased-array imaging transducer in vitro and illustrate its use in vivo by imaging a mouse xenograft model. We found that the 1.8-MHz contrast signal was about four times that acquired at 3.1 MHz on matched probes and nine times greater than echoes received on a higher-frequency probe. Low-frequency imaging was also much more resilient to motion. In vivo, we could identify sub-millimeter vasculature inside a xenograft tumor model and easily assess microbubble half-life. Our results indicate that low-frequency imaging can provide better signal-to-noise because it generates stronger non-linear responses. Combined with high-speed plane-wave imaging, this method could open the door to super-resolution imaging at depth, while high power pulses could be used for image-guided therapeutics.

Effect of compliant layers within piezoelectric composites on power generation providing electrical stimulation in low frequency applications

For patients that use tobacco or have diabetes, bone healing after orthopedic procedures is challenging. Direct current electrical stimulation has shown success clinically to significantly improve bone healing in these difficult-to-fuse populations. Energy harvesting with piezoelectric material has gained popularity in the last decade, but is challenging at low frequencies due to material properties that limit total power generation at these frequencies. Stacked generators have been used to increase power generation at lower voltage levels but have not been widely explored as a load-bearing biomaterial to provide DC stimulation. To match structural compliance levels and increase efficiency of power generation at low frequencies, the effect of compliant layers between piezoelectric discs was investigated. Compliant Layer Adaptive Composite Stacks (CLACS) were manufactured using five PZT discs connected electrically in parallel and stacked mechanically in series with a layer of low modulus epoxy between each disc. The stacks were encapsulated, keeping PZT and overall volume constant. Each stack was electromechanically tested by varying load, frequency, and resistance. As compliant layer thickness increased, power generation increased significantly across all loads, frequencies, and resistances measured. As expected, increase in frequency significantly increased power output for all groups. Similarly, an increase applied peak-to-peak mechanical load also significantly increased power output. The novel use of CLACS for power generation under load and frequencies experienced by typical orthopedic implants could provide an effective method to harvest energy and provide power without the use of a battery in multiple low frequency applications.

In vivo preclinical cancer and tissue engineering applications of absolute oxygen imaging using pulse EPR

The value of any measurement and a fortiori any measurement technology is defined by the reproducibility and the accuracy of the measurements. This implies a relative freedom of the measurement from factors confounding its accuracy. In the past, one of the reasons for the loss of focus on the importance of imaging oxygen in vivo was the difficulty in obtaining reproducible oxygen or pO₂ images free from confounding variation. This review will briefly consider principles of electron paramagnetic oxygen imaging and describe how it achieves absolute oxygen measurements. We will provide a summary review of the progress in biomedical EPR imaging, predominantly in cancer biology research, discuss EPR oxygen imaging for cancer treatment and tissue graft assessment for regenerative medicine applications.

Aerial low-frequency hearing in captive and free-ranging harbour seals (Phoca vitulina) measured using auditory brainstem responses

The hearing sensitivity of 18 free-ranging and 10 captive harbour seals (Phoca vitulina) to aerial sounds was measured in the presence of typical environmental noise through auditory brainstem response measurements. A focus was put on the comparative hearing sensitivity at low frequencies. Low- and mid-frequency thresholds appeared to be elevated in both captive and free-ranging seals, but this is likely due to masking effects and limitations of the methodology used. The data also showed individual variability in hearing sensitivity with probable age-related hearing loss found in two old harbour seals. These results suggest that the acoustic sensitivity of free-ranging animals was not negatively affected by the soundscape they experienced in the wild.

Comparing average levels and peak occurrence of overnight sound in the medical intensive care unit on A-weighted and C-weighted decibel scales

PURPOSE

Sound levels in the intensive care unit (ICU) are universally elevated and are believed to contribute to sleep and circadian disruption. The purpose of this study is to compare overnight ICU sound levels and peak occurrence on A- vs C-weighted scales.

MATERIALS AND METHODS

This was a prospective observational study of overnight sound levels in 59 medical ICU patient rooms. Sound level was recorded every 10 seconds on A- and C-weighted decibel scales. Equivalent sound level (Leq) and sound peaks were reported for full and partial night periods.

RESULTS

The overnight A-weighted Leq of 53.6 dBA was well above World Health Organization recommendations; overnight C-weighted Leq was 63.1 dBC (no World Health Organization recommendations). Peak sound occurrence ranged from 1.8 to 23.3 times per hour. Illness severity, mechanical ventilation, and delirium were not associated with Leq or peak occurrence. Equivalent sound level and peak measures for A- and C-weighted decibel scales were significantly different from each other.

CONCLUSIONS

Sound levels in the medical ICU are high throughout the night. Patient factors were not associated with Leq or peak occurrence. Significant discordance between A- and C-weighted values suggests that low-frequency sound is a meaningful factor in the medical ICU environment.

Enhancement of Neuromodulation with Novel Pulse Shapes Generated by Controllable Pulse Parameter Transcranial Magnetic Stimulation

BACKGROUND

Standard repetitive transcranial magnetic stimulation (rTMS) devices generate bidirectional biphasic sinusoidal pulses that are energy efficient, but may be less effective than monophasic pulses that induce a more unidirectional electric field. To enable pulse shape optimization, we developed a controllable pulse parameter TMS (cTMS) device.

OBJECTIVE

We quantified changes in cortical excitability produced by conventional sinusoidal bidirectional pulses and by three rectangular-shaped cTMS pulses, one bidirectional and two unidirectional (in opposite directions), and compared their efficacy in modulating motor evoked potentials (MEPs) produced by stimulation of motor cortex.

METHODS

Thirteen healthy subjects completed four sessions of 1 Hz rTMS of the left motor cortex. In each session, the rTMS electric field pulse had one of the four shapes. Excitability changes due to rTMS were measured by applying probe TMS pulses before and after rTMS, and comparing resultant MEP amplitudes. Separately, we measured the latency of the MEPs evoked by each of the four pulses.

RESULTS

While the three cTMS pulses generated significant mean inhibitory effects in the subject group, the conventional biphasic cosine pulses did not. The strongest inhibition resulted from a rectangular unidirectional pulse with dominant induced current in the posterior-anterior direction. The MEP latency depended significantly on the pulse shape.

CONCLUSIONS

The pulse shape is an important factor in rTMS-induced neuromodulation. The standard cosine biphasic pulse showed the smallest effect on cortical excitability, while the greatest inhibition was observed for an asymmetric, unidirectional, rectangular pulse. Differences in MEP latency across the various rTMS pulse shapes suggest activation of distinct subsets of cortical microcircuitry.

Great Ears: Low-Frequency Sensitivity Correlates in Land and Marine Leviathans

Like elephants, baleen whales produce low-frequency (LF) and even infrasonic (IF) signals, suggesting they may be particularly susceptible to underwater anthropogenic sound impacts. Analyses of computerized tomography scans and histologies of the ears in five baleen whale and two elephant species revealed that LF thresholds correlate with basilar membrane thickness/width and cochlear radii ratios. These factors are consistent with high-mass, low-stiffness membranes and broad spiral curvatures, suggesting that Mysticeti and Proboscidea evolved common inner ear adaptations over similar time scales for processing IF/LF sounds despite operating in different media.

Effect of Different Phases of Menstrual Cycle on Heart Rate Variability (HRV)

BACKGROUND

Heart Rate Variability (HRV), which is a measure of the cardiac autonomic tone, displays physiological changes throughout the menstrual cycle. The functions of the ANS in various phases of the menstrual cycle were examined in some studies.

AIMS AND OBJECTIVES

The aim of our study was to observe the effect of menstrual cycle on cardiac autonomic function parameters in healthy females.

MATERIALS AND METHODS

A cross-sectional (observational) study was conducted on 50 healthy females, in the age group of 18-25 years. Heart Rate Variability (HRV) was recorded by Physio Pac (PC-2004). The data consisted of Time Domain Analysis and Frequency Domain Analysis in menstrual, proliferative and secretory phase of menstrual cycle. Data collected was analysed statistically using student's pair t-test.

RESULTS

The difference in mean heart rate, LF power%, LFnu and HFnu in menstrual and proliferative phase was found to be statistically significant. The difference in mean RR, Mean HR, RMSSD (the square root of the mean of the squares of the successive differences between adjacent NNs.), NN50 (the number of pairs of successive NNs that differ by more than 50 ms), pNN50 (the proportion of NN50 divided by total number of NNs.), VLF (very low frequency) power, LF (low frequency) power, LF power%, HF power %, LF/HF ratio, LFnu and HFnu was found to be statistically significant in proliferative and secretory phase. The difference in Mean RR, Mean HR, LFnu and HFnu was found to be statistically significant in secretory and menstrual phases.

CONCLUSION

From the study it can be concluded that sympathetic nervous activity in secretory phase is greater than in the proliferative phase, whereas parasympathetic nervous activity is predominant in proliferative phase.

The effects of percutaneous ethanol injection followed by 20-kHz ultrasound and microbubbles on rabbit hepatic tumors

OBJECTIVE

Low-frequency ultrasound (US) in combination with microbubbles (MBs) is able to inhibit the growth of VX2 rabbit liver tumors. In this study, we investigated the feasibility of using percutaneous ethanol injection (PEI) followed by low-frequency ultrasound and microbubbles (USMB) to inhibit VX2 tumor growth.

METHODS

Eighteen New Zealand rabbits with hepatic VX2 tumors were divided into three groups: PEI, low-frequency ultrasound and MBs followed by PEI (USMB + PEI), and PEI followed by USMB (PEI + USMB). PEI was performed by ultrasound-guided injection of 95% anhydrous alcohol into internal liver tumors in rabbits twice a week for 2 weeks. The US parameters were 20 kHz, 2 W/cm(2), 40% duty cycle, 5 min, and once every other day for 2 weeks. Magnetic resonance imaging (MRI) was used to observe tumors before and after treatment, to examine changes in the tumors, and to measure the diameters of the tumors. All animals were followed up for 180 days after tumor implantation. Autopsy was performed at the end of the scheduled follow-up or immediately after death. Anatomically observed metastatic sites included the liver, lung, abdomen, and pelvic cavity. The survival time of all rabbits was recorded.

RESULTS

After 4 weeks of treatment, on MRI, the tumor diameters in the PEI, USMB + PEI, and PEI + USMB groups were 8.33 ± 1.83, 19 ± 2.61, and 4.5 ± 1.22 mm, respectively. There was a significant difference in tumor size indicated by MRI in the three groups. Tumor size was smaller in the PEI + USMB group than in the PEI and USMB + PEI groups, with t = 4.54, p = 0.0062, and t = 16.38, p < .0001, respectively. The PEI + USMB group showed the fewest metastasis sites (χ(2) = 11.7333, p = 0.0194) and the longest survival period (χ(2) = 7.448, p = 0.0241).

CONCLUSION

Percutaneous ethanol injection followed by low-frequency ultrasound and microbubbles can be effective in inhibiting rabbit liver tumors and prolonging survival time.

Impact of acoustic airflow on intrasinus drug deposition: New insights into the vibrating mode and the optimal acoustic frequency to enhance the delivery of nebulized antibiotic

AIM

We investigated the impact of vibrating acoustic airflow, the high frequency (f≥100 Hz) and the low frequency (f≤45 Hz) sound waves, on the enhancement of intrasinus drug deposition.

METHODS

(81m)Kr-gas ventilation study was performed in a plastinated human cast with and without the addition of vibrating acoustic airflow. Similarly, intrasinus drug deposition in a nasal replica using gentamicin as a marker was studied with and without the superposition of different modes of acoustic airflow.

RESULTS

Ventilation experiments demonstrate that no sinus ventilation was observed without acoustic airflow although sinus ventilation occurred whatever the modes of acoustic airflow applied. Intrasinus drug deposition experiments showed that the high frequency acoustic airflow led to 4-fold increase in gentamicin deposition into the left maxillary sinus and to 2-fold deposition increase into the right maxillary sinus. Besides, the low frequency acoustic airflow demonstrated a significant increase of 4-fold and 2-fold in the right and left maxillary sinuses, respectively.

CONCLUSION

We demonstrated the benefit of different modes of vibrating acoustic airflow for maxillary sinus ventilation and intrasinus drug deposition. The degree of gentamicin deposition varies as a function of frequency of the vibrating acoustic airflow and the geometry of the ostia.

Low frequency noise impact from road traffic according to different noise prediction methods

The European Noise Directive 2002/49/EC requires to draw up noise action plans. Most of the implemented solutions consist in using barriers, even if some studies evidenced that annoyance could increase after their installation. This action dumps the high frequencies, decreasing the masking effect on low ones. Therefore, people annoyance and complaints may increase despite the mitigation. This can happen even in pedestrian zones near main roads due to the screening effect of first buildings row. In this paper, the authors analyze the post-operam screening effects in terms of low frequency noise. The difference between C- and A-weighted levels is calculated as annoyance indicator (LC-A). Different methods able to map noise with octave bands detail are tested in order to establish differences in the estimates of annoyance exposure. In particular, a comparison is carried out between data from interim method NMPB 96, its updated version 2008, NORD 2000 and those provided by a customized procedure through ISO 9613 propagation and Statistical Pass By measurements. Test sites are simulated in order to validate each model results through measurements. Results are discussed for real locations in Pisa city center and virtual scenarios in a rising scale of complexity.

Ocular vestibular-evoked myogenic potentials (oVEMPs) in response to bone-conducted vertex vibration

OBJECTIVE

To investigate low-frequency vertex bone-conducted (BC) vibration for evoking ocular vestibular myogenic potentials (oVEMPs) and its ability to discriminate between lesioned and healthy ears.

METHODS

oVEMPs were analysed in response to 125-Hz single cycle vertex BC vibration in healthy subjects (n=50) and in patients with severe unilateral vestibular loss (n=10). Both positive and negative initial stimulus motions were used.

RESULTS

In most healthy subjects, vertex BC vibration oVEMPs was successfully and symmetrically evoked from both ears. The response was dependent on the direction of the stimulus motion. The latency was shorter with negative initial stimulus motion; however, a positive initial stimulus motion generated somewhat larger amplitudes. Furthermore, there was no significant response from lesioned ears, whereas oVEMPs from the patients' healthy ears were similar to the responses in healthy subjects.

CONCLUSION

The oVEMP low-frequency BC response was dependent on the direction of the initial stimulus motion. Testing oVEMPs in response to low-frequency vertex vibration can discriminate patients with unilateral vestibular function loss from healthy controls.

SIGNIFICANCE

Low-frequency vertex BC vibration oVEMPs should be considered a possible clinical screening test to evaluate vestibular function.

Effects of Low-frequency Current Sacral Dermatome Stimulation on Idiopathic Slow Transit Constipation

[Purpose] This study aimed to determine whether low-frequency current therapy can be used to reduce the symptoms of idiopathic slow transit constipation (ISTC). [Subjects] Fifteen patients (ten male and five female) with idiopathic slow transit constipation were enrolled in the present study. [Results] Bowel movements per day, bowel movements per week, and constipation assessment scale scores significantly improved after low-frequency current simulation of S2-S3. [Conclusion] Our results show that stimulation with low-frequency current of the sacral dermatomes may offer therapeutic benefits for a subject of patients with ISTC.

rTMS in resistant mixed states: an exploratory study

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) has shown efficacy in resistant unipolar depression, but its efficacy in bipolar disorders has not yet been extensively investigated. Mixed episodes are reported in up to 40% of acute bipolar admissions and are associated with severe psychopathology, comorbidity, high risk of suicide and poor treatment response. Right low-frequency rTMS (LF-rTMS) as an augmentation treatment might be effective for mixed states.

METHODS

Forty patients were treated during a 4-week period with a mood stabilizer and subsequent rTMS (low frequency stimulation - 1Hz - applied to the right Dorso-Lateral Prefrontal Cortex (DLPFC)) as add-on treatment for 3 weeks. Response to LF-rTMS was assessed by the Hamilton Depression Rating Scale (HAM-D), the Young Mania Rating Scale (YMRS) and the Clinical Global Impressions-Bipolar Version (CGIBP) subscales. ANOVA with repeated measures performed on HAM-D, YMRS and CGI-BP subscales "change from the preceding phase" and "severity of illness" showed a statistically significant time effect from the baseline to the endpoint.

RESULTS

For the HAM-D there was a 46.6% responder rate, of which 28.6% was remitted, while for the YMRS there was a 15% responder rate, all of which was remitted.

LIMITATIONS

The open label-design of our study and the lack of a sham-controlled group represent a methodological limitation.

CONCLUSIONS

The results suggest that LF-rTMS on the right DLFC might be a potential augmentation strategy in the treatment of both depressive and manic symptoms in mixed states.

Potential health impacts of residential exposures to extremely low frequency magnetic fields in Europe

Over the last two decades residential exposure to extremely low frequency magnetic fields (ELF MF) has been associated with childhood leukaemia relatively consistently in epidemiological studies, though causality is still under investigation. We aimed to estimate the cases of childhood leukaemia that might be attributable to exposure to ELF MF in the European Union (EU27), if the associations seen in epidemiological studies were causal. We estimated distributions of ELF MF exposure using studies identified in the existing literature. Individual distributions of exposure were integrated using a probabilistic mixture distribution approach. Exposure-response functions were estimated from the most recently published pooled analysis of epidemiological data. Probabilistic simulation was used to estimate population attributable fractions (AFP) and attributable cases of childhood leukaemia in the EU27. By assigning the literature review-based exposure distribution to all EU27 countries, we estimated the total annual number of cases of leukaemia attributable to ELF MF at between ~50 (95% CIs: -14, 132) and ~60 (95% CIs: -9, 610), depending on whether exposure-response was modelled categorically or continuously, respectively, for a non-threshold effect. This corresponds to between ~1.5% and ~2.0% of all incident cases of childhood leukaemia occurring annually in the EU27. Considerable uncertainties are due to scarce data on exposure and the choice of exposure-response model, demonstrating the importance of further research into better understanding mechanisms of the potential association between ELF MF exposure and childhood leukaemia and the need for improved monitoring of residential exposures to ELF MF in Europe.

Long-term outcomes of pediatric sinus bradycardia

OBJECTIVES

To delineate the long-term outcomes and mechanisms of pediatric sinus bradycardia.

STUDY DESIGN

Participants with sinus bradycardia who were identified from a survey of 432,166 elementary and high school students, were enrolled 10 years after the survey. The clinical course, heart rate variability, and hyperpolarization-activated cyclic nucleotide-gated potassium channel 4 (HCN4) gene were assessed.

RESULTS

A total of 104 (male:female was 60:44; prevalence, 0.025%) participants were observed to have sinus bradycardia at age 15.5 ± 0.2 years with a mean heart rate of 48.4 ± 0.4 beats per minute; 86 study participants (83%) responded to clinical assessment and 37 (36%) underwent laboratory assessment. Athletes composed 37.8% of the study participants. During the extended 10-year follow-up, 15 (17%) of the participants had self-limited syncopal episodes, but none had experienced life-threatening events. According to Holter recordings, none of the participants had heart rate <30 beats per minute or a pause longer than 3 seconds. Compared with 67 age- and sex-matched controls, the variables of heart rate based on the spectral and time domain analysis of the participants with sinus bradycardia were all significantly higher, indicating higher parasympathetic activity. The results of mutation analysis were negative in the HCN4 gene in all of our participants.

CONCLUSIONS

The long-term outcomes of the children and adolescents with sinus bradycardia identified using school electrocardiographic survey are favorable. Parasympathetic hyperactivity, instead of HCN4 gene mutation, is responsible for the occurrence of sinus bradycardia.

Automated identification of normal and diabetes heart rate signals using nonlinear measures

Diabetes mellitus (DM) affects considerable number of people in the world and the number of cases is increasing every year. Due to a strong link to the genetic basis of the disease, it is extremely difficult to cure. However, it can be controlled to prevent severe consequences, such as organ damage. Therefore, diabetes diagnosis and monitoring of its treatment is very important. In this paper, we have proposed a non-invasive diagnosis support system for DM. The system determines whether or not diabetes is present by determining the cardiac health of a patient using heart rate variability (HRV) analysis. This analysis was based on nine nonlinear features namely: Approximate Entropy (ApEn), largest Lyapunov exponet (LLE), detrended fluctuation analysis (DFA) and recurrence quantification analysis (RQA). Clinically significant measures were used as input to classification algorithms, namely AdaBoost, decision tree (DT), fuzzy Sugeno classifier (FSC), k-nearest neighbor algorithm (k-NN), probabilistic neural network (PNN) and support vector machine (SVM). Ten-fold stratified cross-validation was used to select the best classifier. AdaBoost, with least squares (LS) as weak learner, performed better than the other classifiers, yielding an average accuracy of 90%, sensitivity of 92.5% and specificity of 88.7%.