Biomedical Instrumentation

The National Assessment and Accreditation Council (NAAC) has been set up to facilitate the volunteering institutions to assess their performance through introspection. NAAC is taking efforts for assessment and accreditation with an objective of continuous improvement of quality in higher education since two decade. It has made significant impact on improvement of quality in higher education. NAAC has revised its accreditation framework and made ICT enabled, objective, transparent, surmountable and robust. The self study report has been made qualitative and quantitative matrix oriented. AQAR is also proposed qualitative and quantitative matrix oriented from academic year 2020-21. This paper presents some points related to accreditation process of Indian higher education system with some of the revised accreditation framework of NAAC. This framework deals with various innovations and reforms brought in the accreditation process. The revised accreditation framework has introduced several concepts in quality assurance such as Student Satisfaction Survey (SSS), Data Validation and Verification (DVV), Quality bench-marking, Innovation, Ecosystem, Alumni Engagement, Institutional Values and Distinctiveness in the accreditation process. It is useful to all educational institutions for their quality management to create new policies of quality management and to inculcate innovation in the mind of stakeholders. It helps to improve the employing ability and new trends in the market of higher education for global competency.

Remote health monitoring system is one of the most challenging tasks in medical filed, there is an increase in the need of continuous health monitoring system, and to design an efficient module to monitor the patient health. In the proposed system the integration of pulse oximetry sensor with ECG and blood pressure sensor for efficient health monitoring system. Oxygen saturation is one of essential biomedical parameter used to monitor the oxygen content in the human blood. The module is integrated with Arduino board for signal processing and for data transmission and reception the Zigbee module is implemented. A MATLAB software tool is used for data analysis at both transmitter and receiver side. From the result section, it is proved that the integration of pulse oximetry sensor with ECG and blood pressure sensor enhances the system performance in real time application.

Ayurveda and Traditional Chinese Medicine approach uses pulse signals obtained from radial artery as a means for diagnosis of diseases. These conventional techniques are nowadays been replaced by devices using various sensors for detecting pulse signal from radial artery at wrist position. This paper gives a brief review on such diagnosing techniques developed till now for diagnosis of various diseases using the concepts of Nadi Vigyan. The use of different sensors and their results will also be discussed in this paper.

Mathematics is the only word that conquers the whole world. Mathematics comprises each and every concept that exists in this world. Statistics and probability are the two main concepts that are dealing with the statistical survey of this world. Of these two concepts, Probability has one of the Main applications of dealing with mathematics that is very much useful in real life applications. In this paper, Bayes’ Theorem and its applications are discussed deeply with its application problems using the data which was collected for the company named Appin Technology during the industrial exposure training. This application helped me to give some useful ideas to the company to improve their production level.

Wireless Sensor Networks (WSNs) are gaining popularity in our day-today lives because of its wide range of applications in health care monitoring, industrial applications, control networks, environmental sensing, etc. In this paper, we present a brief review on wireless technologies for choosing better, faster and reliable data transmission of medical parameters in health care monitoring systems of WSN. The sensors, which can be either wearable over body or implanted or embedded inside the body, help to monitor the health condition of a person in wireless body area networks (WBANs). WBAN assist in facilitating the on-demand services for patients at home (outpatients) and in clinic\hospital (in-patients), by providing the agile and better results of physiological status to nursing stations or monitoring sites with efficient utilization of wireless network technologies.

This paper presents a simple, low-cost, speedy and non-invasive method using Force Sensing Resistors (FSR) strategically placed over the Carotid and Radial arteries to evaluate various arterial wave pulse parameters like heart-rate, Stiffness Index (SI), Reflectivity Index (RI) and Pulse Wave velocity. The pulse rate and shape is used as an estimate of heart-rate. This is used for diagnosis of arrhythmias, tachycardia and bradycardia. The proposed method could be employed as a cheap and effective Cardiovascular disease screening technique, to be later integrated with small wrist watch-like monitors for suitable commercial purposes.

Pulse oximetry has been one of the most significant technological advances in clinical monitoring in the last two decades. Pulse oximetry is a non-invasive photometric technique that provides information about the arterial blood oxygen saturation (SpO 2) and heart rate, and has widespread clinical applications. When peripheral perfusion is poor, as in states of hypovolaemia, hypothermia and vasoconstriction, oxygenation readings become unreliable or cease. The problem arises because conventional pulse oximetry sensors must be attached to the most peripheral parts of the body, such as finger, ear or toe, where pulsatile flow is most easily compromised. Since central blood flow may be preferentially preserved, this review explores a new alternative site, the oesophagus, for monitoring blood oxygen saturation by pulse oximetry. This review article presents the basic physics, technology and applications of pulse oximetry including photoplethysmography. The limitations of this technique are also discussed leading to the proposed development of the oesophageal pulse oximeter. In the majority, the report will be focused on the description of a new oesophageal photoplethysmographic/SpO 2 probe, which was developed to investigate the suitability of the oesophagus as an alternative monitoring site for the continuous measurement of SpO 2 in cases of poor peripheral circulation. The article concludes with a review of reported clinical investigations of the oesophageal pulse oximeter.

This paper highlights inception with immense importance of the National Assessment and Accreditation Council (NAAC) policy to promote the concept of best practices benchmarking. The Benchmarking is an increasingly popular tool applied in particular area of Higher education and is used extensively by both Developers and Providers. Best practices are those which adds the value to human life and support main cause of an institution. It helps in development of an institution as source/means to perform and undertook social responsibility. Now a days, due to increasing competition, demands for accountability and higher volumes of available information are changing the methods of how institutions of higher education operate. For higher education to enact substantial and sustainable changes in efficiency and productivity a new way of thinking or paradigm that builds efficiency and a desire for continual learning must be integrated into institutional structures. Tools are also being developed that measure or benchmark the progress and success of these efforts. Among the improvement strategies and techniques, benchmarking has emerged as a useful, easily understood, and effective tool for staying competitive.

—In the last decades, photoplethysmography (PPG) has been used as a noninvasive technique for monitoring arterial oxygen saturation by pulse oximetry (PO), whereas near-infrared spec-troscopy (NIRS) has been employed for monitoring tissue blood perfusion. While NIRS offers more parameters to evaluate oxygen delivery and consumption in deep tissues, PO only assesses the state of oxygen delivery. For a broader assessment of blood perfusion, this paper explores the utilization of dual-wavelength PPG by using the pulsatile (ac) and continuous (dc) PPG for the estimation of arterial oxygen saturation (SpO 2) by conventional PO. Additionally, the Beer–Lambert law is applied to the dc components only for the estimation of changes in deoxyhemoglobin (HHb), oxyhemoglobin (HbO 2), and total hemoglobin (tHb) as in NIRS. The system was evaluated on the forearm of 21 healthy volunteers during induction of venous occlusion (VO) and total occlusion (TO). A reflectance PPG probe and NIRS sensor were applied above the brachioradialis, PO sensors were applied on the fingers, and all the signals were acquired simultaneously. While NIRS and forearm SpO 2 indicated VO, SpO 2 from the finger did not exhibit any significant drop from baseline. During TO, all the indexes indicated the change in blood perfusion. HHb, HbO 2 , and tHb changes estimated by PPG presented high correlation with the same parameters obtained by NIRS during VO (r 2 = 0.960, r 2 = 0.821, and r 2 = 0.974, respectively) and during TO (r 2 = 0.988, r 2 = 0.940, and r 2 = 0.938, respectively). The system demonstrated the ability to extract valuable information from PPG signals for a broader assessment of tissue blood perfusion. Index Terms—Beer–Lambert law, near-infrared spec-troscopy (NIRS), optical sensors, photoplethysmography (PPG), physiological monitoring, pulse oximetry (PO).

Pulse oximetry utilizes the technique of photoplethysmography to estimate arterial oxygen saturation (SpO 2) values. During hypothermia, the amplitude of the photoplethysmograph (PPG) is compromised which can lead to inaccurate estimation of SpO 2. A new mutlimode PPG/pulse oximeter sensor was developed to investigate the behaviour of PPGs during conditions of induced hypothermia (hand immersed in an ice bath). PPG measurements from 20 volunteers were conducted and SpO 2 values were estimated at all stages of the experiment. Good quality PPG signals were observed from the majority of the volunteers at almost all hand temperatures. At low temperature ranges, from 13 to 21 • C, the failure rate to estimate SpO 2 values from the multimode transreflectance PPG sensor was 2.4% as compared to the commercial pulse oximeter with a failure rate of 70%.

Photoplethysmography (PPG) is a non-invasive electro-optical technique widely used in the monitoring of the pulsations associated with changes in blood volume in a peripheral vascular bed. The technique is based on the absorption properties of vascular tissue when it is transilluminated by light. Photoplethysmography is also used in the estimation of arterial blood oxygen saturation ðSpO 2 Þ by pulse oximetry where the technique relies on the presence of adequate peripheral arterial pulsations. The aim of this study was to investigate (14 healthy volunteers) the effect of pressure cuff-induced hypoperfusion on PPG signals and SpO 2 s using a custom made finger blood oxygen saturation PPG=SpO 2 sensor and a commercial finger pulse oximeter. PPG signals with high signal-to-noise ratios were obtained from all induced pressures prior to full brachial occlusion. An Analysis of Variance (ANOVA) on ranks showed that there are statistically significant differences ðp < 0:05Þ between the PPGs in the low pressures (0–80 mmHg) than those in the upper pressures (90–150 mmHg). Both pulse oximeters showed gradual decrease of saturations during induced hypoperfusion which demonstrate the direct relation between blood volumes (PPG amplitudes), arterial vessel stenosis and blood oxygen saturation. The custom made pulse oximeter was found to be more sensitive to SpO 2 changes than the commercial pulse oximeter especially at high occluding pressures.

The study presented here targets the development of a low power hearing aid that helps an individual, with conductive type of deafness, to hear naturally, clearly and intelligibly. It uses a piezoelectric actuator that helps in direct oscillation of the stapes with the arrival of sound wave resulting in sound demonstration much superior to that of conventional hearing aid. The hydraulic amplification of the piezoelectric device generates sufficient stapes displacement and an ICP sensor detects corresponding sound pressure level. Additionally, in order to avoid the unwanted interference of the incoming sound frequency with the vibrating frequency of the piezoelectric element, the later is kept within acceptable limits by resonant frequency bandwidth control technique. Owing to its micro power consumption, the proposed design undoubtedly has the potential to replace the battery powered conventional hearing aids, thereby diminishing the recurring losses and making the system cost-effective.

This paper describes the structure for ubiquitous healthcare system by means of wireless biosensors. In this system the wireless biosensor network has been used for monitoring vital signals. It consists of two sections; first biomedical sensor wireless network has been used to collect the body parameter signals, the signals then processed using wireless communication system that utilizes a number of biosensors and in the second section local base station transmits the collected biosensor signal using ZigBee transreceiver. The base station is constituted using a receiver ZigBee modem. The system has been tested in real time where data was processed, recorded and displayed successfully.

—Peripheral perfusion is often poor and barely pulsatile in patients undergoing prolonged major surgery. Hence, the arterial blood oxygen saturation (SpO 2) readings from commercial finger pulse oximeters can become unreliable or cease when they are most needed. To overcome this limitation, the esophagus has been investigated as an alternative measurement site, as perfusion may be preferentially preserved centrally. A reflectance esophageal pulse oximeter probe, and a processing system implemented in LabVIEW were developed. The system was evaluated in clinical measurements on 49 cardiothoracic surgery patients. The SpO 2 values from the esophagus were in good agreement with arterial blood oxygen saturation (SaO 2) values obtained from blood gas analysis and CO-oximetry. The means (SD) of the differences between the esophageal SpO 2 and SaO 2 results from blood gas analysis and CO-oximetry were 0.02 0.88% and 0.73 0.72%, respectively. In five (10.2%) of the patients , the finger pulse oximeter failed for at least 10 min while the esophageal SpO 2 readings remained reliable. The results confirm that the esophagus may be used as an alternative monitoring site for pulse oximetry even in patients with compromised peripheral perfusion.

In order to further understand the contribution of venous and arterial effects to the photoplethysmographic (PPG) signal, recordings were made from 20 healthy volunteer subjects during an exercise in which the right hand was raised and lowered with reference to heart level. Red (R) and infrared (IR) PPG signals were obtained from the right index finger using a custom-made PPG processing system. Laser Doppler flowmetry (LDF) signals were also recorded from an adjacent fingertip. The signals were compared with simultaneous PPG signals obtained from the left index finger. On lowering the hand to 50 cm below heart level, both ac and dc PPG amplitudes from the finger decreased (e.g. 18.70 and 63.15% decrease in infrared dc and ac signals respectively). The decrease in dc amplitude most likely corresponded to increased venous volume, while the decrease in ac PPG amplitude was due to regulatory adjustments on the arterial side in response to venous distension. Conversely, ac and dc PPG amplitudes increased on raising the arm above heart level. Morphological changes in the ac PPG signal are thought to be due to vascular resistance changes, predominately venous, as the hand position is changed.

Pulse oximeter probes placed peripherally may fail to give accurate values of arterial blood oxygen saturation (SpO 2) when peripheral perfusion is poor. Since central blood flow may be preferentially preserved, the oesophagus was suggested as an alternative monitoring site. A reflectance oesophageal photoplethysmographic (PPG) probe and a multiplexed data acquisition system, operating simultaneously at two wavelengths and incorporating an external three-lead electrocardiogram (ECG) reference channel, has been developed. It has been used to investigate the suitability of the oesophagus as a possible monitoring site for SpO 2 in cases of compromised peripheral perfusion. Oesophageal PPG signals and standard ECG traces were obtained from 16 anaesthetized patients and displayed on a laptop computer. Measurable PPG signals with high signal-to-noise ratios at both infrared and red wavelengths were obtained from all five oesophageal depths investigated. The maximum PPG amplitude occurred at 25 cm from the upper incisors in the mid-oesophagus. The measured pulse transit times (PTTs) to the oesophagus were consistent with previous measurements at peripheral sites and had a minimum value of 67 ± 30 ms at a depth of 30 cm. There was broad agreement between the calculated values of oesophageal SpO 2 and those from a commercial finger pulse oximeter.

Pulse oximeter probes attached to the finger may fail to estimate blood oxygen saturation (SpO 2) in patients with compromised peripheral perfusion (e.g. hypothermic cardiopulmonary bypass surgery). The measurement of SpO 2 from a central organ such as the oesophagus is suggested as an alternative to overcome this problem. A reflectance oesophageal pulse oximeter probe and a processing system implemented in LabVIEW were developed. The system was evaluated in clinical measurements on 50 cardiothoracic surgery patients. Oesophageal photoplethysmographic (PPG) signals with large amplitudes and high signal-to-noise ratios were measured from various depths within the oesophagus from all the cardiothoracic patients. The oesophageal PPG amplitudes from these patients were in good agreement with previous oesophageal PPG amplitude measurements from healthy anaesthetized patients. The oesophageal pulse oximeter SpO 2 results agreed well with the estimated arterial oxygen saturation (SaO 2) values inferred from the oxygen tension obtained by blood gas analysis. The mean (± SD) of the differences between the oesophageal pulse oximeter SpO 2 readings and those from blood gas analysis was 0.02 ± 0.88%. Also, the oesophageal pulse oximeter was found to be reliable and accurate in five cases of poor peripheral perfusion when a commercial finger pulse oximeter probe failed to estimate oxygen saturation values for at least 10 min. These results suggest that the arterial blood circulation to the oesophagus is less subject to vasoconstriction and decreased PPG amplitudes than are the peripheral sites used for pulse oximetry such as the finger. It is concluded that oesophageal SpO 2 monitoring may be of clinical value.

Skin moisture relates to the state of multiple skin constituents and aspects, but unfortunately, a device which could provide comprehensive and in vivo analysis is not available. Nevertheless, several reports have demonstrated accurate estimations of dermal water content using near-infrared spectroscopy (NIRS), and the potential of employing this technique in skin analysis. We aim to investigate whether NIRS could detect changes in skin barrier function through evaluation of skin water uptake in relation to moisturizer application. NIR and capacitance data were collected from 20 volunteers at both forearms, prior to and after seven days of regular moisturizer use. Results indicated lower peak intensities at the 1940-nm minima and higher intensities at the 1450-nm equivalent minima with moisturizer abstinence, while the opposite was true with regular moisturizer application. As the light beam would have traveled deeper into the skin at 1450 nm, it has been concluded that long-term, frequent moisturizer use had limited the penetration of extrinsic water. Partial least squares analysis showed that separation of sample's scores increased with abstinence of moisturizer use. Thus, NIRS can provide valuable information not only on dermal water contents but also on additional parameters such as skin barrier function.

Background A pilot investigation was undertaken to assess the performance of a novel fiber-optic cerebral pulse oximetry system. A fiber-optic probe designed to pass through the lumen of a cranial bolt of the type used to make intracranial pressure measurements was used to obtain optical reflectance signals directly from brain tissue. Methods Short-duration measurements were made in six patients undergoing neurosurgery. These were followed by a longer duration measurement in a patient recovering from an intracerebral hematoma. Estimations of cerebral arterial oxygen saturation derived from a frequency domain-based algorithm are compared with simultaneous pulse oximetry (SpO 2) and hemoximeter (SaO 2) blood samples. Results The short-duration measurements showed that reliable photoplethysmographic signals could be obtained from the brain tissue. In the long-duration study, the mean (±SD) difference between cerebral oxygen saturation (ScaO 2) and finger SpO 2 (in saturation units) was-7.47(±3.4)%. The mean (±SD) difference between ScaO 2 and blood SaO 2 was-7.37(±2.8)%. Conclusions This pilot study demonstrated that arterial oxygen saturation may be estimated from brain tissue via a fiber-optic pulse oximeter used in conjunction with a cranial bolt. Further studies are needed to confirm the clinical utility of the technique.

A new system for measuring the oxygen saturation of blood within tissue has been developed, for a variety of patient monitoring applications. A particular unmet need is in the central nervous system, and this project aims to devise a means for measuring blood oxygen saturation in the brain tissue of patients recovering from neurosurgery or head injury. Coupling light sources and a photodetector to optical fibres results in a probe small enough to pass through a cranial bolt of the type already in use for intra-cranial pressure monitoring. The development and evaluation of a two-wavelength fibre-optic reflectance photoplethysmography (PPG) system are described. It was found that good quality red and near-infrared PPG signals could be obtained from the finger using a fibre-optic probe. Experiments were conducted to find the inter-fibre spacings that yield signals most suitable for calculating oxygen saturation. Reliable signals could be obtained for inter-fibre spacings between 2 mm and 5 mm, the latter being the size of the maximum aperture in the cranial bolt. A preliminary measurement from human brain tissue is also presented.

There is a need for reliable continuous monitoring of abdominal organ oxygen saturation (SpO 2). Splanchnic ischaemia may ultimately lead to cellular hypoxia and necrosis and contribute to the development of multiple organ failure and increased mortality. A reflectance electro-optical photoplethysmographic (PPG) probe and signal processing system were developed. Satisfactory PPG signals from abdominal organs (bowel, liver and kidney) and the finger were obtained from 12 anaesthetised patients. There were no statistically significant differences between the average PPG amplitudes recorded from the abdominal organs and those obtained simultaneously from the finger. These observations suggest that pulse oximetry can be a valid monitoring technique for abdominal organs such as the bowel, liver and kidney.

The monitoring of arterial blood oxygen saturation in patients with compromised peripheral perfusion is often difficult, because conventional non-invasive techniques such as pulse oximetry (Sp02) can fail. Poor peripheral circulation commonly occurs after major surgery including cardiopulmonary bypass. The difficulties in these clinical situations might be overcome if the sensor were to monitor a better perfused central part of the body such as the oesophagus. A new oesophageal photoplethysmographic (PPG) probe and an isolated processing system have been developed to investigate the pulsatile signals of anaesthetised adult patients undergoing routine surgery. Measurements were made in the middle third of the oesophagus, 25cm to 30cm from the upper incisors. The AC PPG signals are sampled by a data acquisition system connected to a laptop computer. The signals recorded correspond to infrared and red AC PPGs from the middle third oesophagus and the finger. Preliminary results from 20 patients show that good quality AC PPG signals can be measured in the human oesophagus. The ratio of the oesophageal to finger AC PPG amplitudes was calculated for the infrared and red wavelengths for each patient. The mean (+standard deviation) of this ratio was 2.9+2.1 (n = 19) for the infrared wavelength and 3.1 • (n = 16) for the red wavelength. The red and infrared wavelengths used are appropriate for pulse oximetry and this investigation indicates that the mid-oesophagus may be a suitable site for the reliable monitoring of SpO 2 in patients with poor peripheral perfusion.

Pulse oximetry is being used in everyday clinical practice in anaesthesia utilising a peripheral probe. However, it may be unreliable in certain clinical situations such as hypothermia, hypovolemia, vasoconstriction and decreased cardiac output. Similar situations occur in burns patients and, more importantly, burns to extremities which limit the sites available for measurement of peripheral oxygen saturation (SpO 2). To overcome these limitations, the oesophagus has been investigated as an alternative measurement site, as perfusion may be preferentially preserved centrally. A miniaturised reflectance oesophageal saturation (SpO 2) probe has been constructed utilising infrared and red photodiodes and a photodetector. Our study was aimed at evaluating the reliability of oesophageal pulse oximetry in major burns patients. Seven adult patients (five males, two females) were studied. They were sedated and ventilated as part of their routine care. Measurable photoplethysmographic (PPG) traces and SpO 2 values were obtained in the oesophagus of all patients at a mean depth of 15.6 AE 1.8 cm (measured from the lips). It was found that the oesophageal pulse oximeter results were in good agreement with oxygen saturation measurements obtained by a CO-oximeter. The mean (AES.D.) of the differences between the oesophageal oxygen saturation results and those from CO-oximetry was 0.50 AE 0.69%. A Bland and Altman analysis showed that the bias and the limits of agreement between the oesophageal and commercial toe pulse oximeters were 0.4% and À3.6% to 4.6%, respectively. This study suggests that the oesophagus can be used as an alternative site for monitoring arterial blood oxygen saturation by pulse oximetry in burned patients. Crown

A base-4 leading zero detector (LZD) design is proposed in this paper. The design is similar to the approach originally proposed by V.G. Oklobdzija with a different technique. The circuit modules used in the base-4 LZD approach are designed and several N-bit LZD circuits are implemented with a standard-cell realization in the Taiwan Semiconductor Manufacturing Company (TSMC) 0.65um CMOS process. The performance and layout area of the base-4 LZD realization is compared for implementations that contain only 4-to-1 and 2-to-1 multiplexers.

Pulse oximetry probes placed peripherally may fail to give accurate values of blood oxygen saturation when the peripheral circulation is poor. Because central blood flow may be preferentially preserved, we investigated the oesophagus as an alternative monitoring site. A reflectance blood oxygen saturation probe was developed and evaluated in 49 patients undergoing cardiothoracic surgery. The oesophageal pulse oximeter results were in good agreement with oxygen saturation measurements obtained by a blood gas analyser, a CO-oximeter and a commercial finger pulse oximeter. The median (IQR [range]) difference between the oesophageal oxygen saturation results and those from blood gas analysis were 0.00 ()0.30 to 0.30 [)4.47 to 2.60]), and between the oesophageal oxygen saturation results and those from CO-oximetry were 0.75 (0.30 to 1.20 [)1.80 to 1.80]). Bland–Altman analysis showed that the bias and the limits of agreement between the oesophageal and finger pulse oximeters were)0.3% and)3.3 to 2.7%, respectively. In five (10.2%) patients, the finger pulse oximeter failed for at least 10 min, whereas the oesophageal readings remained reliable. The results suggest that the oesophagus may be used as an alternative monitoring site for pulse oximetry even in patients with compromised peripheral perfusion.

BACKGROUND: In this pilot study we explored the suitability of the esophagus as a new measuring site for blood oxygen saturation (Spo 2) in neonates. METHODS: A new miniaturized esophageal pulse oximeter has been developed. Five patients (one child and four neonates) were studied. RESULTS: Spo 2 values were obtained in the esophagus of all patients. A Bland and Altman plot of the difference between Spo 2 values from the esophageal pulse oximeter and a commercial toe pulse oximeter against their mean showed that the bias and the limits of agreement between the two pulse oximeters were 0.3% and 1.7% to 1.0%, respectively. CONCLUSIONS: This study suggests that the esophagus can be used as an alternative site for monitoring blood oxygen saturation in children and neonates.

A new, continuous method of monitoring splanchnic organ oxygen saturation (SpO 2) would make the early detection of inadequate tissue oxygenation feasible, reducing the risk of hypoperfusion, severe ischaemia, and, ultimately, death. In an attempt to provide such a device, a new fibre optic based reflectance pulse oximeter probe and processing system were developed followed by an in vivo evaluation of the technology on seventeen patients undergoing elective laparotomy. Photoplethysmographic (PPG) signals of good quality and high signal-to-noise ratio were obtained from the small bowel, large bowel, liver and stomach. Simultaneous peripheral PPG signals from the finger were also obtained for comparison purposes. Analysis of the amplitudes of all acquired PPG signals indicated much larger amplitudes for those signals obtained from splanchnic organs than those obtained from the finger. Estimated SpO 2 values for splanchnic organs showed good agreement with those obtained from the finger fibre optic probe and those obtained from a commercial device. These preliminary results suggest that a miniaturized 'indwelling' fibre optic sensor may be a suitable method for pre-operative and post-operative evaluation of splanchnic organ SpO 2 and their health.

Photoplethysmography (PPG) signals have been investigated at a new anatomical site, the anterior fontanelle (ANTF), on the hypothesis that blood supply at this location is preferentially preserved during cases of poor peripheral circulation which might cause the commercial pulse oximeters to fail to estimate accurately arterial blood oxygen saturation (SpO2). Two custom built reflectance PPG sensors have been developed, one for placement on the fontanelle and one on the periphery (foot). A PPG processing system and software were also developed to process the raw PPG signals and to estimate SpO2. A pilot study on sixteen babies, (9 male, 7 female) with a median age of 15.5 days (interquartile range = 46.8 days) and a median weight of 3.15 kg (SD = 0.93kg), on a neonatal intensive care unit (NICU) has been carried out. PPG signals from the ANTF were of good quality and high signal-to-noise ratio. The amplitudes of the ANTF PPGs were found to be sensitive to changes in amplitude when amplitudes were observed at the reference PPG site. Bland-Altman analysis of the gold standard blood gas analysis reveals that all three sensors are inaccurate at SaO2 < 85-90 %, but the ANTF sensor shows better mean difference than the commercial device.

The importance of determining skin hydration has over the years prompt the development of many instruments and methods, specifically designed to assess this parameter or water contents especially in the stratum corneum, and have greatly matured to suit different anatomical sites and measure multiple attributes. Of those, Near Infrared Spectroscopy (NIRS) has gained wide interest as a precise, safe, fast and noninvasive technique for determining skin hydration due to its high sensitivity to hydrogen bonding and ability to measure the amount of water in skin directly using the intensities of overtone and combination bands of OH and HOH water bonds occurring in the NIR region, that are good indicators of the state of skin hydration. This paper reports near infrared spec-trophotometric measurements using a highly sophisticated spectrophotometer in the region of 1000-2500 nm to study the water uptake and dehydration properties of skin in vitro using samples of porcine skin. Initial results of pure liquid water and skin samples have clearly displayed the prominent bands associated with water content, and desorption tests have been able to verify changes in these bands associated with water content, although a clear correlation between the rates of weight loss and absorbance loss at various hydration periods has not yet been established. These preliminary results are expected to further explain the relationship between water and skin, and its role within, in hope to aid the future development of a portable instrument based on near infrared spectroscopy that would be capable of directly measuring skin hydration and/or water content in a fast and noninvasive manner.

Introduction: The Perception Sensory Threshold (ST) for sinusoidal current stimuli at 5, 250, and 2,000 Hz
is commonly used in the assessment of peripheral nerve fibers (C, Aδ, and Aβ, respectively). However, the
neuroselectivity of these frequencies is far from consensus. In addition, Reaction Time (RT) measurements
suggest that 2,000 Hz stimuli excite Aβ-fibers, 250 Hz Aβ- or Aδ-fibers, as well as 5 Hz Aβ-, Aδ- or C-fibers.
Therefore, we suppose that the sinusoidal current neuroselectivity may be better observed if ST and RT
parameters are jointly evaluated. In addition, we have investigated whether there are other sets of frequencies
that could be used. Methods: Thus this work investigates ST and RT for stimuli with frequency ranging from 1
to 3,000 Hz, on 28 healthy subjects aged from 19 to 44 years old (27.1 ± 5.49). ST and RT dissimilarity among
different frequencies was evaluated applying bi-dimensional Fisher Quadratic Discriminant. Results: The
lowest classification error (3.6%) was obtained for 1, 250, and 3,000 Hz. Error for 5, 250, and 2,000Hz was
16.7%. Stimulation frequency at 1 Hz evoked more sensations related to C-fibers (53% of reports) than to
Aβ-fibers (36%). However, this behavior did not repeat itself at 5 Hz (only 21% of perceptions were related
to C-fibers against 64% to Aβ-fibers). Sensations related to Aβ-fibers prevailed for the highest frequencies
presented to the subjects (2,000 Hz – 82% and 3,000 Hz – 93%). Mean RT values showed a decreasing
trend with frequency. Conclusion: These results suggest that frequencies 1, 250, and 3,000 Hz are more
neuroselective than 5, 250, and 2,000 Hz for the evaluation of peripheral sensitive fibers. Furthermore, they
show RT usefulness.

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 re¯ectance photoplethysmographic probe to investigate photoplethysmographic signals from human viscera (bowel, liver, and kidney). Recordings were obtained simultaneously from the abdominal viscera and the ®nger 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 ®rst time in humans. There were no statistically signi®cant differences between photoplethysmographic amplitudes from viscera and those from the ®nger. Our results indicate the feasibility of pulse oximetry for the measurement of visceral oxygenation in humans.