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In order to reduce the influence of differences in human characteristics on the blood pressure prediction model and further improve the accuracy of blood pressure prediction, this paper establishes support vector machine regression model and random forest regression model for accurate blood pressure measurement. First, the photoelectric method is used to obtain the photoelectric plethysmography signal (PPG) and ECG signals from people of different ages, and the blood pressure value is roughly estimated based on the high-quality physiological signals and the vascular elastic cavity model; then the human body characteristics are used as the input parameters of the blood pressure prediction model, and the model parameters are used to find the best parameter combination to improve the prediction performance of the model; finally, through a lot of training and learning, the best blood pressure prediction model is selected to achieve accurate measurement of blood pressure values. It has been verified by experiments that the average absolute error of diastolic and systolic blood pressure based on the random forest optimization model meets the standard of less than 5mmHg formulated by AAMI (American Medical Instrument Promotion Association), which is better consistent with the method of mercury sphygmomanometer, and has more excellent performance than support vector machine regression model under the same conditions.

NEW FINDINGS: What is the central question of this study? Does chronic mountain sickness (CMS) alter sympathetic neural control and arterial baroreflex regulation of blood pressure in Andean (Quechua) highlanders? What is the main finding and its importance? Compared to healthy Andean highlanders, basal sympathetic vasomotor outflow is lower, baroreflex control of muscle sympathetic nerve activity is similar, supine heart rate is lower and cardiovagal baroreflex gain is greater in mild CMS. Taken together, these findings reflect flexibility in integrative regulation of blood pressure that may be important when blood viscosity and blood volume are elevated in CMS. ABSTRACT: The high-altitude maladaptation syndrome chronic mountain sickness (CMS) is characterized by excessive erythrocytosis and frequently accompanied by accentuated arterial hypoxaemia. Whether altered autonomic cardiovascular regulation is apparent in CMS is unclear. Therefore, during the 2018 Global REACH expedition to Cerro de Pasco, Peru (4383 m), we assessed integrative control of blood pressure (BP) and determined basal sympathetic vasomotor outflow and arterial baroreflex function in eight Andean natives with CMS ([Hb] 22.6 ± 0.9 g·dL(-1) ) and seven healthy highlanders ([Hb] 19.3 ± 0.8 g·dL(-1) ). R-R interval (RRI, electrocardiogram), beat-by-beat BP (photoplethysmography) and muscle sympathetic nerve activity (MSNA; microneurography) were recorded at rest and during pharmacologically induced changes in BP (modified Oxford test). Although [Hb] and blood viscosity (7.8 ± 0.7 vs. 6.6 ± 0.7 cP; d = 1.7, P = 0.01) were elevated in CMS compared to healthy highlanders, cardiac output, total peripheral resistance and mean BP were similar between groups. The vascular sympathetic baroreflex MSNA set-point (i.e. MSNA burst incidence) and reflex gain (i.e. responsiveness) were also similar between groups (MSNA set-point, d = 0.75, P = 0.16; gain, d = 0.2, P = 0.69). In contrast, in CMS the cardiovagal baroreflex operated around a longer RRI (960 ± 159 vs. 817 ± 50 ms; d = 1.4, P = 0.04) with a greater reflex gain (17.2 ± 6.8 vs. 8.8 ± 2.6 ms·mmHg(-1) ; d = 1.8, P = 0.01) versus healthy highlanders. Basal sympathetic vasomotor activity was also lower compared to healthy highlanders (33 ± 11 vs. 45 ± 13 bursts·min(-1) ; d = 1.0, P = 0.08). In conclusion, our findings indicate adaptive differences in basal sympathetic vasomotor activity and heart rate compensate for the haemodynamic consequences of excessive erythrocyte volume and contribute to integrative blood pressure regulation in Andean highlanders with mild CMS.

Background: Fibromyalgia syndrome (FMS) is a condition characterised by the presence of chronic, widespread musculoskeletal pain, low pain threshold and hyperalgesia. Myofascial trigger points (MTrPs) may worsen symptoms in patients with FMS. Objective: The purpose of this randomised controlled trial was to compare the effects of dry needling and transcutaneous electrical nerve stimulation (TENS) on pain intensity, heart rate variability, galvanic response and oxygen saturation (SpO2). Methods: 74 subjects with FMS were recruited and randomly assigned to either the dry needling group or the TENS group. Outcomes measures (pain intensity, heart rate variability, galvanic skin response, SpO2 and photoplethysmography) were evaluated at baseline and after 6 weeks of treatment. 2×2 mixed-model analyses of variance (ANOVAs) were performed. Results: The mixed-model ANOVAs showed significant differences between groups for the sensory dimension of pain, affective dimension of pain, total dimension of pain, visual analogue scale (VAS) and present pain intensity (PPI) (P=0.001). ANOVAs also showed that significant differences between groups were achieved for very low frequency power of heart rate variability (P=0.008) and low frequency power (P=0.033). There were no significant differences in dry needling versus TENS groups on the spectral analysis of the photoplethysmography and SpO2. Conclusions: This trial showed that application of dry needling therapy and TENS reduced pain attributable to MTrPs in patients with FMS, with greater improvements reported in the dry needling group across all dimensions of pain. Additionally, there were between-intervention differences for several parameters of heart rate variability and galvanic skin responses. Trial registration number: NCT02393352

The system used three kinds of light emitting diode with different wave bands in MAX30105 reflex optical sensor, and measured human heart rate and blood oxygen saturation through photoelectric plethysmography. It also utilized DHT11 digital temperature humidity sensor to measure body surface temperature and humidity by using resistance type humidity sensor and negative temperature coefficient (NTC) temperature measuring element. The measuring results were finally and real-timely shown by organic light emitting diode (OLED). After systematic tests and result analysis, the portable physiological data detection system worked steadily. It can relatively precisely and stably measure heart rate, blood oxygen saturation and body surface temperature and humidity, and can monitor real-time change of the data. What is more, the four physiological parameters measured can provide effective references for cardiovascular and cerebrovascular diseases, such as obstructive sleep apnea syndrome and coronary heart disease, and thus can help people to monitor their real-time body situation in their daily lives, in order to more effectively preventing diseases from attacking and worsening in time.

Aim This study evaluated the association of Heart rate variability (HRV) measurements with diabetic peripheral neuropathy (DPN) in patients with type 2 diabetes. Methods This study included 102 Korean subjects with type 2 diabetes. The Michigan neuropathy screening instrument (MNSI) questionnaire score, the MNSI examination score (MNSIES) and the total symptom score were examined for DPN evaluation. Noninvasive HRV measurements were performed using photoelectric plethysmography. Patients with a MNSIES > 2 were considered to have DPN. Results The MNSIES showed significant negative associations with the high frequency (HF) (r = −0.212, p = 0.033) and low frequency (LF) (r = −0.286, p = 0.004) powers. Multiple linear regression analysis revealed that only HF power maintained a significant negative association with the MNSIES (β = −0.184; 95% CI −0.365 to −0.003; p = 0.047), after controlling for significant related confounders, with HRV parameters in male patients with type 2 diabetes. The HF (p = 0.010) and LF (p = 0.025) powers differed significantly between male patients without and those with DPN according to the MNSIES. Conclusions This study revealed a negative association of DPN, as assessed by the MNSIES, with HF power in male patients with type 2 diabetes. DPN defined by foot examination was predictive of cardiac autonomic neuropathy.

Aims Alpha-2 agonists are direct peripheral vasoconstrictors, which achieve these effects by activating vascular smooth muscle alpha-2 adrenoceptors. The impact of this response during dexmedetomidine infusion remains poorly quantified. Our goal was to investigate the pharmacokinetic (PK) and pharmacodynamic (PD, vasoconstriction) effects of a computer-controlled dexmedetomidine infusion in healthy volunteers. Methods After local ethics committee approval, we studied 10 healthy volunteers. To study the peripheral vasoconstrictive effect of dexmedetomidine without concurrent sympatholytic effects, sympathetic fibres were blocked with a brachial plexus block. Volunteers received a dexmedetomidine target-controlled infusion for 15 min, to a target concentration of 0.3 ng ml-1 . Arterial blood samples were collected during and for 60 min after dexmedetomidine infusion for PK analysis. Peripheral vasoconstriction (PD) was assessed using finger photoelectric plethysmography. PK/PD analysis was carried out using nonlinear mixed-effect models. Results We found that the computer-controlled infusion pump delivered mean concentrations greater than 0.3 ng ml-1 over the 15-min infusion duration. The peripheral vasoconstrictive effect correlated with dexmedetomidine plasma concentrations during and after the infusion. A three-compartment model provided a better fit to the data than a two-compartment model. Conclusions We found that dexmedetomidine-induced vasoconstriction is concentration dependent over time. Dexmedetomidine PK were best estimated by a three-compartment model with allometric scaling. Our results may contribute to future modelling of dexmedetomidine-induced haemodynamic effects.

Emotions are affective states related to physiological responses. This study proposes a model for recognition of three emotions: amusement, sadness, and neutral from physiological signals with the purpose of developing a reliable methodology for emotion recognition using wearable devices. Target emotions were elicited in 37 volunteers using video clips while two biosignals were recorded: photoplethysmography, which provides information about heart rate, and galvanic skin response. These signals were analyzed in frequency and time domains to obtain a set of features. Several feature selection techniques and classifiers were evaluated. The best model was obtained with random forest recursive feature elimination, for feature selection, and a support vector machine for classification. The results show that it is possible to detect amusement, sadness, and neutral emotions using only galvanic skin response features. The system was able to recognize the three target emotions with accuracy up to 100% when evaluated on the test data set. © 2019 Elsevier Ltd

Raynaud's phenomenon (RP) is often the first sign of systemic sclerosis (SSc). Molecular mechanisms involved are incompletely understood, but reactive oxygen, nitrogen, and sulfur species are thought to play an important role in the pathogenesis of SSc. Free thiol groups play a protective role against oxidative stress and may represent an attractive therapeutic target. We aimed to investigate the effects of hypothermia‐induced vasoconstriction on the responsiveness of redox‐related markers. Thirty participants (n = 10/group [SSc, primary Raynaud's phenomenon (PRP), healthy controls (HC)]) were included in this study. Fingertip photoelectric plethysmography was performed during a standardized cooling and recovery experiment. Venous blood was collected at four predetermined time points. Free thiols, NO‐derived species (nitros(yl)ated species, nitrite, nitrate), sulfate and endothelin‐1 were measured. Lower baseline concentrations of free thiols were observed in PRP and SSc patients (HC: 5.87 [5.41–5.99] μmol/g; PRP: 5.17 [4.74–5.61]; SSc 5.28 [4.75–5.80], P = 0.04). Redox‐related markers remained unchanged during cooling. However, an unexpected increase in systemic free thiol concentrations was observed in all groups during the recovery phase. The response of this marker differed between groups, with a higher increase found in SSc patients (HC Δ = 1.30 [1.48–1.17]; PRP Δ = 1.04 [1.06–1.03]; SSc Δ = 1.72 [1.13–1.49], P = 0.04). NO‐derived species, sulfate and endothelin‐1 levels remained unchanged throughout the recovery phase. This exploratory study sheds light on the rapid responsiveness of systemic free thiol concentrations following reperfusion, which may reflect overall redox balance. The robust response to reperfusion in SSc patients suggests that reductive systems involved in this response are functionally intact in these patients.

Objective. The aim of the study was to assess the association between plethysmographically measured vasospasms during stepwise cooling and recovery, as an index for digital ischaemia, and nailfold capillaroscopic pattern (NCP) severity in patients with primary or secondary RP, including SSc.Methods. In 381 consecutive patients with suspected RP without a history of digital ulcers, NCP (assessed by widefield videocapillaroscopy), fingertip photoelectric plethysmography during cooling and recovery and clinical characteristics were analysed. NCPs were graded as follows: normal, non-specific, early and active. The mean ischaemic time was defined as the mean time of perfusion loss during cooling and recovery of five fingers.Results. In the patients with loss of perfusion during cooling and recovery, the NCP was normal in 152, non-specific in 96, early in 61 and active in 39 patients. The mean ischaemic time was positively associated with the severity of NCP, with P Conclusion. We demonstrate that the degree of vasospasm and ischaemia provoked by stepwise cooling and recovery are positively associated with NCP in patients with RP of different aetiologies and without a history of digital ulcers.

Keisaku Fujimoto,1 Haruna Yamazaki,2 Akikazu Uematsu2 1Department of Clinical Laboratory Sciences, Shinshu University School of Health Sciences, Matsumoto, Nagano, Japan; 2Department of Biomedical Laboratory Sciences, Graduate School of Medicine, Shinshu University, Matsumoto, Nagano, Japan Objective/background: This study was performed to evaluate the association of nocturnal autonomic nerve (AN) dysfunction, especially parasympathetic nerve (PN) function instability, and nocturnal oxygen desaturation (NOD) in patients with chronic lung diseases (CLD).Patients and methods: Twenty-nine stable CLD patients with irreversible pulmonary dysfunction and mild-to-moderate daytime hypoxemia, 13 CLD patients receiving long-term oxygen therapy (LTOT) with maintained SpO2 >90%, and 17 senior healthy volunteers underwent two-night examinations of nocturnal AN function by pulse rate variability (PRV) instead of heart rate variation using a photoelectrical plethysmograph simultaneously monitoring SpO2 and the presence of sleep disordered breathing at home. AN function was examined by instantaneous time–frequency analysis of PRV using a complex demodulation method.Results: There were no significant differences in mean low frequency/high frequency (HF) ratio (index of sympathetic nerve activity) or mean HF amplitude (index of PN activity) among controls and CLD patients with and without NOD (defined as SpO2

Background Although the exact etiology of systemic sclerosis (SSc) remains unknown, a current hypothesis is that reactive species (including reactive oxygen species (ROS), reactive nitrogen species (RNS and reactive sulfur species (RSS)) play an important role in the pathogenesis. In addition, the chemical interactions between these molecules, also known as the reactive species interactome, may lead to the formation of more harmful free radicals, thus leading to more damage. We have previously shown a rapid free thiol increase in SSc patients during a cooling and recovery experiment, however the implications of RNS and RSS in this process remain uncharacterized. Objectives The aim of the current study was to explore nitric oxide and sulfate response, as a measure of the unified reactive species interactome, during hypothermia induced Raynaud’s attack in systemic sclerosis (SSc), primary Raynaud’s phenomenon (PRP) and healthy controls (HC). Methods Healthy controls (n=10), PRP patients (n=10) and SSc patients (n=10), all aged ≥18 years, were included. All SSc patients fulfilled the ACR/EULAR 2013 criteria. Fingertip photoelectric plethysmography was performed during a standardised cooling and recovery experiment. Patient characteristics were obtained and blood was drawn at four predetermined time points (T0, T1, T2 and T3). In addition to the previously mentioned free thiols, the following markers were also measured: nitros(yl)ated species, nitrite, nitrate, sulfate and the vascular leakage related molecules angiopoietin-1 and angiopoietin-2). Results Our results revealed a significantly longer median duration of hypoperfusion and longer recovery time in SSc patients compared to PRP patients and HC. This coincided with stable levels of angiopoietin-1/angiopoietin-2 throughout the experiment. In regards to the thiol modification related molecules, (nitrate, nitrite and RXNO) an increased median level of nitrate (T2: median 29.6 µmol, range 21.99–41.70 µmol, p=0.041) was found in SSc patients. Correspondingly, the same trend was observed for the median plasma concentrations of sulfate (p>0.05 at all time points). Conclusions We have previously shown an increase of free thiols in all patients during the reperfusion phase. This finding sheds new light on the possibility that processes related to oxidative thiol modification, are rapidly reversible. The current findings revealed also a trend in increased levels of nitrate and sulfate in SSc patients. Therefore, it is plausible that these markers of the redox system interact with one another through the same pathway, underlining the complexity of the redox interactome and suggesting potential novel approaches for therapeutic intervention. Disclosure of Interest None declared

Cuffless evaluation of arterial blood pressure (BP) using pulse wave velocity (PWV) has received attraction over the years. Local PWV based techniques for cuffless BP measurement has more potential in accurate estimation of BP parameters. In this work, we present the design and experimental validation of a novel single-source Photoplethysmograph (PPG) transducer for arterial blood pulse detection and cycle-to-cycle local PWV measurement. The ability of the transducer to continuously measure local PWV was verified using arterial flow phantom as well as by conducting an in-vivo study on 17 volunteers. The single-source PPG transducer could reliably acquire dual blood pulse waveforms, along small artery sections of length less than 28 mm. The transducer was able to perform repeatable measurements of carotid local PWV on multiple subjects with maximum beat-to-beat variation less than 12%. The correlation between measured carotid local PWV and brachial BP parameters were also investigated during the in-vivo study. Study results prove the potential use of newly proposed single-source PPG transducers in continuous cuffless BP measurement systems.

With the continuous aging of the populations in developed countries, the medical requirements of the aged are expected to increase. In this paper, a ring-type pulse oximeter finger sensor and a 24-hour ambulatory heart rate monitoring system for the aged are presented. We also demonstrate the feasibility of extracting accurate heart rate variability measurements from photoelectric plethysmography signals gathered using a ring-type pulse oximeter sensor attached to the finger. We designed the heart rate sensor using a CPU with built-in ZigBee stack for simplicity and low power consumption. We also analyzed the various distorted signals caused by motion artifacts using a FFT, and designed an algorithm using a least squares estimator to calibrate the signals for better accuracy.

Continuous monitoring of blood oxygen saturation (SpO2) level and heart rate is critical in surgery, ICUs and patients suffering from Chronic Obstructive Pulmonary Diseases. Pulse oximeters which compute SpO2 using transmittance photoplethysmography (PPG), is widely accepted for continuous monitoring. Presence of motion artifacts in PPG signals is a major obstacle in the extraction of reliable cardiovascular parameters, in real time and continuous monitoring applications. In this paper, a wrist worn device with a custom finger probe with an integrated accelerometer to remove motion artifacts is presented. An algorithm which can run on low power systems with processing constraints is implemented on the device. The device does continuous acquisition of PPG and accelerometer waveforms and computes SpO2 using the proposed light weight algorithm. The measurement results are continuously synced with an Android tablet, which acts as a gateway and is pushed on to the cloud for further analysis. The accuracy in SpO2 measured by the device was validated using Fluke ProSim 8 SpO2 simulator and the efficiency in accurately computing SpO2 in the presence of motion was validated over 40 healthy volunteers in a controlled setting.

A study has been made of the changes in the amplitudes shown on photoelectric plethysmographs of the fingers of one hand of controls (17 men and 17 women without Raynaud's phenomenon) during cooling and warming up of the hand. This is called the cooling and warming up test. The hands of the women appeared to cool more quickly than of the men, besides getting warm more quickly and remaining warm for a longer period. This difference is already apparent at the lowest water temperatures (6 and 3 degrees C) and may be ascribed to a difference in hand volume, with a hunting reaction due to extreme cold. The lowest values of controls appear to be useful for the clinical differentiation of patients with a serious Raynaud's phenomenon. The test is said to be positive when the values are below the lowest values of the controls. The test was performed on 50 of 58 out-patients suffering from Raynaud's phenomenon. In serious cases the severity of the disease could be assessed objectively. In less serious cases the test was sometimes negative.

As low power, low cost wireless communication technology like Bluetooth, Zigbee, RFID has been put to practical use together with the wellbeing trend, the concern about ubiquitous health care has been greatly increased and u-Health is becoming one of the most important application in the sensor network field. Especially, development of the medical services to be able to cope with a state of emergency for solitary senior citizens and the aged in silver town is very meaningful itself and their needs are also expected to continuously increase with a rapid increase in an aging population. In this paper we demonstrate the feasibility of extracting accurate heart rate variability (HRV) measurements from photoelectric plethysmography(PPG) signals gathered by a ring type pulse oximeter sensor attached to the finger. For this, we made 2 types of ring sensor, that is reflective and pervious type, and developed the remote monitoring system which is able to collect HR data from ring sensor, analyze and cope with a state of emergency.

The main aim of the biomedical signal processing is to extract information from a biological signal. Biomedical signal processing involves recording of the biological events such as heart-beats etc. The feasibility of extracting accurate Heart-Rate is demonstrated by measuring the variability in the photoelectric plethysmography signals. The Pulse Rate is obtained from the systolic peaks of the pulse wave measured from a Heart-Beat sensor. From the Pulse Rate the Heart-Rate can be calculated. Digital Data Processing system involves real-time processing of Heart-Beat pulses. The captured data is processed in real time using Pulse Shape Discrimination Algorithm and verified on a field programmable gate array device. This study opens a way to derive heart rate from pulse rate with a simple assessment which can be applied to many persons suffering with various heart diseases. It is also analyzed the various distorted signals caused by motion artifacts are removed using morphological operators such as erosion and dilation without the help of any filters, and designed a PSD algorithm to calibrate the signals for better accuracy. The main focus is on the operation of Correlation with which the PSD has been designed. The proposed Algorithm is designed using Xilinx ISE 13.4.

Introduction Arterial stiffness is an independent risk factor for cardiovascular morbidity and can be assessed by applanation tonometry by measuring pulse wave velocity (PWV) and augmentation index (AIX) by pressure pulse wave analysis (PWA). As an inexpensive and operator independent alternative, photoelectric plethysmography (PPG) has been introduced with analysis of the digital volume pulse wave (DPA) and its second derivatives of wave reflections. Objective The objective was to investigate the repeatability of arterial stiffness parameters measured by digital pulse wave analysis (DPA) and the associations to applanation tonometry parameters. Methods and Results 112 pregnant and non-pregnant individuals of different ages and genders were examined with SphygmoCor arterial wall tonometry and Meridian DPA finger photoplethysmography. Coefficients of repeatability, Bland-Altman plots, intraclass correlation coefficients and correlations to heart rate (HR) and body height were calculated for DPA variables, and the DPA variables were compared to tonometry variables left ventricular ejection time (LVET), PWV and AIX. No DPA variable showed any systematic measurement error or excellent repeatability, but dicrotic index (DI), dicrotic dilatation index (DDI), cardiac ejection elasticity index (EEI), aging index (AI) and second derivatives of the crude pulse wave curve, b/a and e/a, showed good repeatability. Overall, the correlations to AIX were better than to PWV, with correlations coefficients >0.70 for EEI, AI and b/a. Considering the level of repeatability and the correlations to tonometry, the overall best DPA parameters were EEI, AI and b/a. The two pansystolic time parameters, ejection time compensated (ETc) by DPA and LVET by tonometry, showed a significant but weak correlation. Conclusion For estimation of the LV function, ETc, EEI and b/a are suitable, for large artery stiffness EEI, and for small arteries DI and DDI. The only global parameter, AI, showed a high repeatability and the overall best correlations with AIX and PWV.

The aim of this study is to examine the efficacy of alprostadil liposomal preparation in the treatment of blue toe syndrome. As many as 32 patients with blue toe syndrome were randomized into the test group and a control group. Patients out of the test group were treated with alprostadil liposomal preparation, while those out of the control group received placebo administration. Inter-group comparisons were conducted for the post-therapeutic changes of microcirculation and improvements of clinical symptoms. In the test group, there were eight subjects with marked response (50.0 %), six subjects with partial response (37.5 %), and two subjects with no response (12.5 %), with the overall response rate of 87.5 %. In the control group, there were three cases (18.8 %), one case (6.4 %), and 12 cases (75 %), respectively, with the overall response rate of 25.0 %. The inter-group difference of response was statistically significant (Χ (2) = 12.987, P = 0.0020.05). In the test group, there was one case of administration site redness which could be resolved spontaneously. No other adverse drug reactions were reported. No any complaints were reported for the control group. The inter-group difference of nail-fold microcirculation was not statistically significant (P0.05). The post-therapeutic points of nail-fold microcirculation in the test group decreased significantly (P0.05), but no significant changes were observed for the control group (P0.05). The post-therapeutic waveform changes of photoelectric plethysmography were significant for the test group in comparison to the control. The safety and efficacy of alprostadil liposomal preparation have been demonstrated in the treatment of blue toe syndrome.

We evaluated the accuracy of modern infrared photosensors (IPs) from a photoplethysmography (PPG) machine as flow detector in determining the systolic arterial pressures and ankle/brachial indices (ABIs) in comparison to the traditional continuous wave Doppler (Doppler) method. Pressures were obtained by placing an appropriate pneumatic cuff above the elbow and ankle. The Doppler probe was placed at brachial artery, posterior tibial artery and dorsalis pedis artery, and the IP was placed on the pad of the index finger and great toe. The two techniques were compared in 181 limbs in our non-invasive vascular laboratory, 133 limbs with normal and 48 limbs with abnormal ABIs. The accuracy of absolute ankle pressure measurements was also compared by both methods. We found that IPs from PPG machine have a good correlation (linear regression r=0.96 for normal and r=0.95 for abnormal ankle pressures) with the Doppler method. There was no significant difference (P< or =0.0001) in the ABIs calculated by two methods in either normal or abnormal subjects. The PPG method was easier, quicker and automated as compared with the cumbersome Doppler method. While PPG method does not differentiate between occlusive disease of posterior tibial and anterior tibial/dorsalis pedis arteries, it is better suited for non-compliant patients and is superior to Doppler method in advanced occlusive arterial disease. We recommend that it be used on a routine basis.

The relationships between peripheral blood pressure and blood volume pulse waveforms can provide valuable physiological data about the peripheral vascular system, and are the subject of this study. Blood pressure and volume pulse waveforms were collected from 12 normal male subjects using non-invasive optical techniques, finger arterial blood pressure (BP, Finapres: Datex-Ohmeda) and photoelectric plethysmography (PPG) respectively, and captured to computer for three equal (1 min) measurement phases: baseline, hand raising and hand elevated. This simple physiological challenge was designed to induce a significant drop in peripheral blood pressure. A simple first order lag transfer function was chosen to study the relationship between blood pressure (system input) and blood volume pulse waveforms (system output), with parameters describing the dynamics (time constant, tau) and input-output gain (K). Tau and K were estimated for each subject using two different system identification techniques: a recursive parameter estimation algorithm which calculated tau and K from a linear auto-regressive with exogenous variable (ARX) model, and an artificial neural network which was trained to learn the non-linear process input-output relationships and then derive a linearized ARX model of the system. The identification techniques allowed the relationship between the blood pressure and blood volume pulses to be described simply, with the neural network technique providing a better model fit overall (p < 0.05, Wilcoxon). The median falls in tau following the hand raise challenge were 26% and 31% for the linear and neural network based techniques respectively (both p < 0.05, Wilcoxon). This preliminary study has shown that the time constant and gain parameters obtained using these techniques can provide physiological data for the clinical assessment of the peripheral circulation.

A 56-year-old man presented with intermitted lower extremity claudication (after walking about 500 meters). On examination, his right femoral artery was palpable, while the popliteal artery and more distal peripheral arteries were not palpable. The peripheral arteries of the left lower extremity were palpable throughout. Using photoelectric plethysmography, a pulse wave was recorded in the left third toe, but not in the right. Angiography demonstrated a complete occlusion of the right femoral artery as well as a complete occlusion of the left common iliac artery with well developed colleteral blood flow in the pelvic region. We performed a right fomoro-popliteal bypass grafting with an in-situ saphenous vein. The postoperative course was uneventful. A postoperative angiogram indicated good patency of the graft. There have been no signs or symptoms of ischemia in the left lower extremity. The finding of complete occlusion of the left common iliac artery without ischemic symptoms or signs due to well developed collateral blood flow was very interesting. Though the limb-threatening ischemia by interruption of critical collaterals during nonvascular operation is a rare occurrence, the recognition and appropriate management of this occurrence in patients with arteriosclerosis obliterans should minimize the morbidity of this unusual but serious complication.

A pulse oximeter is a noninvasive, accurate, continuous indicator of arterial oxygen saturation. It is considered one of the American Society of Anesthesia (ASA) standard monitors. The basic technology behind the pulse oximeter is photoelectric plethysmography, as reported by Hertzman. There are two components of the waveforms: the pulsatile component or AC portion and the static component or DC. Time and frequency domain are two different methods available for plethysmographic waveform analysis. Variability of the plethysmographic waveforms with ventilation provides an insight about functional volume status of the subjects. Plethysmographic waveform analysis provides more clinical information, and this what we are going to explore in this chapter.

The arterial pressure elevations that accompany sleep apneas may be caused by chemoreflex stimulation, negative intrathoracic pressure, and/or arousal. To assess the neurocirculatory effects of arousal alone, we applied graded auditory stimuli during non-rapid-eye-movement (NREM) sleep in eight healthy humans. We measured muscle sympathetic nerve activity (intraneural microelectrodes), electroencephalogram (EEG; C4/A1 and O1/A2), arterial pressure (photoelectric plethysmography), heart rate (electrocardiogram), and stroke volume (impedance cardiography). Auditory stimuli caused abrupt increases in systolic and diastolic pressures (21 +/- 2 and 15 +/- 1 mmHg) and heart rate (11 +/- 2 beats/min). Cardiac output decreased (-10%). Stimuli that produced EEG evidence of arousal evoked one to two large bursts of sympathetic activity (316 +/- 46% of baseline amplitude). Stimuli that did not alter EEG frequency produced smaller but consistent pressor responses even though no sympathetic activation was observed. We conclude that arousal from NREM sleep evokes a pressor response caused by increased peripheral vascular resistance. Increased sympathetic outflow to skeletal muscle may contribute to, but is not required for, this vasoconstriction. The neurocirculatory effects of arousal may augment those caused by asphyxia during episodes of sleep-disordered breathing.

Peripheral pulse waveforms can become stretched and damped with increasing severity of peripheral vascular disease (PVD) and hence could provide valuable diagnostic information. This study compares the diagnostic performance of 3 established classification techniques (a linear discriminant classifier, a k-nearest neighbour classifier, and an artificial neural network) for the detection of lower limb arterial disease from pulse waveforms obtained using photoelectric plethysmography (PPG). Pulse waveforms and pre- and post-exercise Doppler ultrasound ankle to brachial pressure indices (ABPI) were obtained from patients attending a vascular measurement laboratory. A single PPG pulse from each big toe was recorded direct to computer, pre-processed, and then used as classifier input data. The correct classifier outputs were the corresponding ABPI diagnostic classification. Pulse and ABPI measurements from 100 legs were used as training data for each classifier, and the computed classifications for pulses from a further 266 legs were then compared with their ABPI diagnoses. The diagnostic accuracy of the artificial neural network (80%; was higher than for the optimized k-nearest neighbour classifier (k = 27, accuracy 76% and the linear discriminant classifier (71%). The Kappa measure of agreement which excludes chance was highest for the artificial neural network (57%) and significantly higher than that of the linear discriminant classifier (Kappa 40%, p0.05). The value of Kappa for the optimized k-nearest neighbour classifier (k = 27) was intermediate at 47%. This study has shown that classifiers can be taught to discriminate between small, and perhaps subtle, differences in features. We have demonstrated that artificial neural networks can be used to classify arterial pulse waveforms, and can perform better overall than k-nearest neighbour or linear discriminant classifiers for this application.

182 patients treated with cisplatin-based chemotherapy for testicular cancer at Hannover University Medical School who were in complete remission (CR) for more than 1 year after therapy were randomly selected for the evaluation of late vascular toxicity. 90 patients with a mean age of 28 years (19-53) and a median follow-up of 57.9 months (15-159) participated in this examination. Patients were examined clinically and digital photoelectric pulse plethysmography (PP) and Doppler-flow of the digital arteries after cold exposure were performed. Thirty seven per cent of patients developed symptoms of Raynaud's phenomenon (RP) after chemotherapy, which were transient in 7%. PP proved to be highly diagnostic for RP with a sensitivity of 95% and a specificity of 100%. As significant risk factors for the development of RP, the cumulative dose of bleomycin (P0.05) and the use of bleomycin in combination with vinblastine (PVB-regimen) instead of etoposide (PEB-regimen) (P0.01) were found. A trend for an increased frequency of RP was observed in patients who received bleomycin as a bolus instead of continuous infusion. No significant correlation was seen with the cumulative or single doses of cisplatin, etoposide or vinblastine, serum magnesium levels during or after chemotherapy or a history of smoking. RP was not associated with the occurrence of neuro- or ototoxicity. All 7 patients with hypertensive blood pressure before chemotherapy developed RP. Furthermore, the median postchemotherapy diastolic blood pressure had increased by 8 mmHg compared to prechemotherapy values, leading to significant hypertension in 8 patients (20 mmHg increase). 2 patients developed major vascular events with myocardial infarctions at 4 years and 5 years after chemotherapy, respectively. No cerebral infarction was registered. In summary, RP is the main late vascular toxicity affecting one third of patients after curative chemotherapy for testicular cancer. However, the incidence of RP following PEB-therapy in contrast to PVB-therapy appears to be lower. Major vascular events seem to be rare. The prospective evaluation of late toxicity should be part of current chemotherapy treatment for testicular cancer, and long-term follow-up of surviving patients is recommended.

Breathing-coordinated exercise is a traditional Chinese exercise. These exercise maneuvers consist of slow diaphragmatic breathing, end-inspiratory pause, and Kegel's exercise. A total of 30 patients were enrolled in this study, with 12 patients as controls, to evaluate its effect on hemodialysis patients. Exercise was performed for 25 to 30 min twice a day for at least 3 months. Results from the exercise group showed a subjective improvement in appetite and physical strength, and an increase in the frequency of bowel movements, in addition to enhanced sexual activity and a significant increase in Karnofsky scores. Six patients in the exercise group underwent bicycle ergometry and demonstrated a stable maximal oxygen consumption, whereas the control group revealed a decline in maximal oxygen consumption. Photoelectric plethysmography and laser-Doppler flowmetry demonstrated a pulsatile enhancement of the peripheral microcirculation. Abdominal sonography revealed an oscillatory change in the diameter of the inferior vena cava. It was concluded that these gentle exercise maneuvers may improve the quality of life in hemodialysis patients, especially weak dialysis patients. The mechanism may be partly related to an improvement in microcirculation.

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.

Photoplethysmography is one of the optical techniques has been developed for experimental use in vascular disease. It has several advantages over other traditional experimental approaches. Because of its non-invasive, safe, cost- effective and easy-to-use properties, it is considered as a useful diagnostic tool. The further developments in the Photo- plethysmograph may replace it among other tools used in the assessment of vascular diseases such as blood test and ultra- sound. This overview discusses the different terminologies used for the photoplethysmograph and reveals the research discontinuity among different disciplines. Moreover, it suggests standard terminologies as a resolution for a confusion persisted for more than 50 years.