The relationship between women's subjective and physiological sexual arousal

Previous literature presents discordant results on the relationship between physiological and subjective sexual arousal in women. In this study, the use of hierarchical linear modeling (HLM) revealed a significant concordance between continuous measures of physiological and subjective sexual arousal as assessed during exposure to erotic stimuli in a laboratory setting. We propose that past studies that have found little or no association between the two measures may have been in part limited by the methodology and statistical analyses employed.     

Right-left correlation of the sympathetically induced fluctuations of photoplethysmographic signal in diabetic and non-diabetic subjects

Photoplethysmography (PPG) records the cardiac-induced changes in tissue blood volume by light-transmission measurements. The baseline and amplitude of the PPG signal show very low-frequency (VLF) spontaneous fluctuations, which are mediated by the sympathetic nervous system, and high correlation between right and left extremities of healthy subjects. As sympathetic neuropathy is one of the diabetic complications, the right-left correlation of the PPG fluctuations was examined in diabetic patients. The PPG signal was simultaneously measured in the two index fingers and the two second toes of 35 diabetic patients and 33 non-diabetic subjects. For each PPG pulse, the baseline and amplitude were determined, and the right-left correlation coefficients of the VLF fluctuations in the baseline and amplitude were derived. The VLF fluctuations in the baseline showed high right-left correlation, both for fingers (0.93±0.05) and toes (0.93±0.06), for the non-diabetic subjects, and significantly lower correlation (0.78±0.22 and 0.84±0.17, respectively) for the diabetic patients. Similar results were obtained for the amplitude VLF fluctuations. The right-left correlation coefficients for diabetic patients decreased with the disease duration for the toe baseline and toe amplitude fluctuations and correlated with heart rate response to deep breathing for the finger baseline and toe amplitude fluctuations. The right-left correlation coefficients of the PPG fluctuations provide a simple and convenient means for assessing the adequacy of the sympathetic nervous system function.     

Effect of postural changes on lower limb blood volume,detected with non-invasive photoplethysmography

This paper describes the effect of passive leg raising on blood volume change in the lower limb, using a dual probe photoplethysmography (PPG) system employing a tissue optics model. The normalized AC/DC ratio and DC value are introduced from the model to evaluate the dynamic pulsation and total blood volume changes due to postural effects. The AC and DC components of PPG signals were collected from a passive leg raising protocol. With the leg raised, the normalized AC/DC ratio significantly decreased when supine, while the normalized DC value increased significantly in both supine and reclining positions. The parameters from the stationary leg showed similar but smaller responses. These results demonstrate a local and systemic physiological phenomenon in the lower limb blood volume change caused by postural changes. The normalized AC/DC ratio and DC value derived from the tissue optics model could be applied to assess the blood volume change.     

On the analysis of fingertip photoplethysmogram signals

Photoplethysmography (PPG) is used to estimate the skin blood flow using infrared light. Researchers from different domains of science have become increasingly interested in PPG because of its advantages as non-invasive, inexpensive, and convenient diagnostic tool. Traditionally, it measures the oxygen saturation, blood pressure, cardiac output, and for assessing autonomic functions. Moreover, PPG is a promising technique for early screening of various atherosclerotic pathologies and could be helpful for regular GP-assessment but a full understanding of the diagnostic value of the different features is still lacking. Recent studies emphasise the potential information embedded in the PPG waveform signal and it deserves further attention for its possible applications beyond pulse oximetry and heart-rate calculation. Therefore, this overview discusses different types of artifact added to PPG signal, characteristic features of PPG waveform, and existing indexes to evaluate for diagnoses.     

基于高频中值滤波的小波滤波在脑动脉色素浓度谱特征信号提取中的应用

近年来,近红外光谱技术(mear infrared spectrometry,NIRS)在脑科学研究领域倍受青睐。为了更好地满足参数的后续使用并提取出有效特征信号,前期尝试了多种常用滤波方法,为了解决滤后信号易失真以及不能有效滤除低频或者高频噪声的问题,提出了基于高频中值滤波的小波滤波,并采用高度还原真实信号特点的仿真信号以及利用脑血流动力学参数采集系统获得的真实光电容积脉搏波(photoplethysmography,PPG)信号,基于中值滤波的小波滤波进行分析。将实验测试数据与其他滤波方法的特征信号提取效果进行对比,并对处理数据进行信噪比和频谱分析。结果表明,采用中值滤波与小波滤波相结合的滤波方式,对脑动脉色素浓度谱特征信号进行滤波处理,能获得有效、精准的脑血流动力学参数,为后续的测量精度打下基础。该方法有效结合了中值滤波能够剔除粗差的特性和小波滤波在光电容积脉搏波中有效滤除高斯信号的特性,改善了采用单一方式的局限性,提供了一种新的PPG滤波的思路,对比传统方法更加优化。     

Assessment of photoplethysmographic signals for the determination of splanchnic oxygen saturation in humans

The need for a clinically applicable method of detecting splanchnic hypoxia has led to experimental animal studies which indicated the usefulness of intestinal pulse oximetry. Pulse oximetry relies on detection of photoplethysmographic signals. Before developing a pulse oximeter for the measurement of organ oxygen saturation peri-operatively, we designed a system based on a reflectance photoplethysmographic probe to investigate photoplethysmographic signals from human viscera (bowel, liver, and kidney). Recordings were obtained simultaneously from the abdominal viscera and the finger using identical probes. The probe was held sequentially for up to 2 min on the surface of viscera of 12 patients during routine laparotomy. Measurable splanchnic photoplethysmographic signals were recorded for the first time in humans. There were no statistically significant differences between photoplethysmographic amplitudes from viscera and those from the finger. Our results indicate the feasibility of pulse oximetry for the measurement of visceral oxygenation in humans.     

The use of photoconductive cells in photoplethysmography

Photoplethysmography (p.h.p.l.) is a noninvasive method of monitoring changes in peripheral blood volume. The method consists of illuminating the skin with a light flux, and detecting transmitted or backscattered light from the vascular bed by a photosensor. Experience and measurements show that the photoconductor (p.h.c.) is among the most sensitive of photosensors, and it is also small, cheap, and does not require high voltages. The p.h.c., however, has the unfavourable characteristics of temperature and light-history dependence, which contribute to drift, and dynamic characteristics that change with different levels of ambient light and temperature level. This paper investigates these unfavourable electrical properties and shows how they can be dealt with so that the p.h.c. can be used with a high level of confidence, and photoplethysmograms obtained with minimum artefact.     

Effects of acupuncture on skin and muscle blood flow in healthy subjects

In 14 healthy female subjects, the effects of needle stimulation (acupuncture) on skin and muscle blood flow were investigated using a non-invasive custom-designed probe and photoplethysmography (PPG). In randomised order, 2–7 days apart, three modes of needle stimulation were performed on the anterior aspect of the tibia: superficial insertion (SF), insertion into the anterior tibial muscle (Mu), and insertion into the muscle including manipulation of the needle in order to elicit a distinct sensation of distension, heaviness or numbness (DeQi). Before intervention, the subjects rested for 30 min. After the intervention, the needle was left in situ for 20 min. Blood flow recordings were performed intermittently from 10 min prior to the intervention to the end of the trial. In a fourth session, serving as control, corresponding measurements were performed without any needle stimulation. Area under curve was calculated for 5-min periods prior to and after stimulation, respectively, and for the remaining 15-min period after stimulation. Compared to the control situation, muscle blood flow increased following both Mu and DeQi for 20 min, with the latter being more pronounced for the initial 5 min. Skin blood flow increased for 5 min following DeQi. However, no increase was found following SF. The DeQi stimulation was preceded by higher visual analogue scale ratings of anxiety prior to stimulation, which might have influenced skin blood flow to some extent. The results indicate that the intensity of the needling is of importance, the DeQi stimulation resulting in the most pronounced increase in both skin and muscle blood flow.     

Noninvasive assessment of arterial distensibility in adolescents using the second derivative of photoplethysmogram waveform

To clarify the clinical usefulness of the second derivative of the waveform of the fingertip photoplethysmogram (SDPTG), we examined the relationship between the pattern of the SDPTG waveform and risk factors related to atherosclerosis in 1,495 boys and girls aged 9–17 years. The fingertip photoplethysmogram and its second derivative wave were automatically recorded from the second digit of the right hand with the subjects lying in a supine position. The SDPTG waveform consisted of a, b, c and d waves in systole and an e wave in diastole. The heights of the a and d waves were measured from the baseline, and the ratio of the height of the d wave to that of the a wave (d/a ratio) was calculated. The d/a ratio had a negative correlation with the systolic (SBP) and diastolic blood pressures (DBP), atherogenic index (AI) and immunoreactive insulin concentrations (IRI) after adjustment for age. Multiple linear regression analysis revealed that the d/a ratio was associated more with body height than the risk factors for atherosclerosis in boys and girls at the growth period. The effect of sex- and height-specific cutoff values of the 10th percentile for the d/a ratio was therefore tested. The results showed that subjects with d/a ratios lower than the 10th percentile had significantly higher SBP, DBP, AI and IRI values compared to those with higher d/a ratios. These findings suggest that differences in the length of the vascular system, which are related to increases in body height, may modify the SDPTG waveform pattern during adolescence. When the body height as well as age and sex is adequately allowed for, the d/a ratio may be useful for the evaluation of arterial distensibility and for identification of individuals at an increased risk of developing atherosclerosis. Electronic Publication