Oximeter Sensor Research Articles

Optimising the Apnoea Classification Performance of a Neural Network Classifier Processing ECG-Oximetry Signals.

In this paper we investigate using principal components analysis to optimize the performance of a neural network system processing simultaneously acquired electrocardiogram (ECG) and oximetry signals. The algorithm identifies epochs of normal breathing, central apnoea (CA), and obstructive apnoea (OA) by processing a pooled feature set containing information capturing the desaturations from the oximeter sensor as well as time and spectral features from the ECG. Training and testing of the system was facilitated with a dataset of 125 scored polysomnogram recordings with accompanying respiratory event annotations. When classifying the three epoch types, our system achieved a specificity of 91%, a sensitivity to CA of 28% and sensitivity to OA of 63%. A sensitivity of 81% was achieved when the CA and OA epochs were combined into one class.

An effective cloud based personal emergency response system by providing privacy protection for the medical data

Timely access to the emergency medical services is challenging tasks due to the increasing percentage of population. Especially prehospital emergency situations are neglected for quite a long time. The agglomeration of medical gadgets and other system applications that bridges the gap to healthcare IT systems through Internet or computer networks is placed under the domain (IoMT) Internet Of Medical Things . In this project an efficient medical data monitoring and an emergency response system has been developed. IoT in healthcare is made to bridge the gap by providing the connectivity through internet making sure that the information is secured and available on the timely access. The wireless monitoring device collects data from various sensors, which is shared into the database using ZigBee cc2530 Transmitter Receiver through UART communication. The wireless device is embedded with sensors like Pulse oximeter (senses the heart beat rate and blood oxygen concentration)and temperature sensor. This data is monitored regularly and if there is any abnormality in the values then an alert is sent to the doctor to intimate the condition of the patient. This paper provides an interaction of the patient with the doctors. The interaction is enabled using public and private chat application where any number of patients can interact with a doctor. It is challenging task to personalize specific healthcare data i.e. medical records for various application users in an appropriate and secured fashion. Thus, the patient’s health records i.e. prescription, scan reports, etc. are uploaded by the patient which can be viewed by the doctor. These files are encrypted using an encryption algorithm before uploading it into the cloud. Similarly it is decrypted while downloaded by the doctor for reference. The data collected is used for the prediction of diseases like heart attack and the report is sent to the doctor. Hence the project’s aim is, when the recorded value exceeds the threshold range, an automatic intimation with the patient’s collected data is sent to the concerned doctor.

Assessment of MRI Induced Heating Effect for Pulse Oximeter Sensor

Assessment of MRI Induced Heating Effect for Pulse Oximeter Sensor

Effects of Changes in Arterial Carbon Dioxide and Oxygen Partial Pressures on Cerebral Oximeter Performance.

Cerebral oximetry (cerebral oxygen saturation; ScO2) is used to noninvasively monitor cerebral oxygenation. ScO2 readings are based on the fraction of reduced and oxidized hemoglobin as an indirect estimate of brain tissue oxygenation and assume a static ratio of arterial to venous intracranial blood. Conditions that alter cerebral blood flow, such as acute changes in PaCO2, may decrease accuracy. We assessed the performance of two commercial cerebral oximeters across a range of oxygen concentrations during normocapnia and hypocapnia. Casmed FORE-SIGHT Elite (CAS Medical Systems, Inc., USA) and Covidien INVOS 5100C (Covidien, USA) oximeter sensors were placed on 12 healthy volunteers. The fractional inspired oxygen tension was varied to achieve seven steady-state levels including hypoxic and hyperoxic PaO2 values. ScO2 and simultaneous arterial and jugular venous blood gas measurements were obtained with both normocapnia and hypocapnia. Oximeter bias was calculated as the difference between the ScO2 and reference saturation using manufacturer-specified weighting ratios from the arterial and venous samples. FORE-SIGHT Elite bias was greater during hypocapnia as compared with normocapnia (4 ± 9% vs. 0 ± 6%; P < 0.001). The INVOS 5100C bias was also lower during normocapnia (5 ± 15% vs. 3 ± 12%; P = 0.01). Hypocapnia resulted in a significant decrease in mixed venous oxygen saturation and mixed venous oxygen tension, as well as increased oxygen extraction across fractional inspired oxygen tension levels (P < 0.0001). Bias increased significantly with increasing oxygen extraction (P < 0.0001). Changes in PaCO2 affect cerebral oximeter accuracy, and increased bias occurs with hypocapnia. Decreased accuracy may represent an incorrect assumption of a static arterial-venous blood fraction. Understanding cerebral oximetry limitations is especially important in patients at risk for hypoxia-induced brain injury, where PaCO2 may be purposefully altered.

Cerebral oxygenation during electroconvulsive therapy

Objective: Electroconvulsive therapy (ECT) is an effective and life-saving treatment modality, while its effects and side effects are still being discussed. In our study, we aimed to demonstrate the effect of O2 administration on the cerebral oxygenation measured by Near Infrared Spectroscopy and the complications after ECT in the apnea period of ECT. Methods: This prospective, observational study was carried out with 40 patients whom ECT had been planned and who were undergoing ECT for the first time. Cerebral oximeter sensors and Bispectral index (BIS) monitoring were applied in all patients as well as routine monitoring. The participants were randomly divided into two groups. The patients who received administration of 6 L/min O2 through nasal cannula were included in Group O (n=20), and the patients who were not administered O2 were included in Group C (n=20). Hemodynamic data after induction, during the seizures and at the 10th min after the seizures, EtCO2, regional cerebral tissue oxygen saturation (rSO2), BIS values and complications after ECT were recorded in both groups. Results: No significant difference was determined between the groups with regard to rSO2 alteration values measured during the seizures and demographic characteristics. Desaturation (SpO2

Development of a wearable wireless body area network for health monitoring of the elderly and disabled

Novel advancements in systems miniaturization, electronics in health care and communication technologies are enabling the integration of both patients and doctors involvement in health care system. A Wearable Wireless Body Area Network (WWBAN) provides continuous, unobtrusive ambulatory, ubiquitous health monitoring, and provide real time patient’s status to the physician without any constraint on their normal daily life activities. In this project we developed a wearable wireless body area network system that continuously monitor the health of the elderly and the disabled and provide them with independent, safe and secure living. The WWBAN system monitors the following parameters; blood oxygen saturation using a pulse oximeter sensor (SpO2), heart rate (HR) pulse sensor, Temperature, hydration, glucose level and fall detection. When the wearable system is put on, the sensor values are processed and analysed. If any of the monitored parameter values falls below or exceeds the normal range, there is trigger of remote alert by which an SMS is send to a doctor or physician via GSM module and network. The developed system offers flexibility and mobility to the user; it is a real time system and has significance in revolutionizing health care system by enabling non-invasive, inexpensive, continuous health monitoring.

Physiologic Considerations in Detection of Hypoxemia during Vasoconstriction: Radial Artery Compared to Various Pulse Oximeter Sensor Sites

Physiologic Considerations in Detection of Hypoxemia during Vasoconstriction: Radial Artery Compared to Various Pulse Oximeter Sensor Sites

Reproducibility of the Pleth Variability Index in premature infants

The aim was to assess the reproducibility of the Pleth Variability Index (PVI), developed for non-invasive monitoring of peripheral perfusion, in preterm neonates below 32 weeks of gestational age. Three PVI measurements were consecutively performed in stable, comfortable preterm neonates in the first 48 h of life. On each occasion, pulse oximeter sensors were attached to two different limbs for 5 min. Reproducibility was assessed with the intra-class correlation coefficient (ICC) and Bland–Altman analysis. A total of 25 preterm neonates were included. Inter-limb comparison showed fair to moderate ICC’s with 95%-confidence intervals (95%-CI). Left hand–right hand ICC = 0.498, 95%-CI (0.119–0.753); right foot–right hand ICC = 0.314 (−0.088–0.644); right foot–left foot ICC = 0.315 (−0.089–0.628). Intra-limb comparison showed fair to moderate ICC for right foot–right foot ICC = 0.380 (−0.014–0.677); and good ICC for right hand–right hand ICC = 0.646 (0.194–0.852). Bland–Altman plots showed moderate reproducibility of measurements between different limbs and of the same limb in consecutive time periods, with large biases and wide limits of agreement. The findings from this study indicate that PVI measurement is poorly reproducible when measured on different limbs and on the same limb in stable and comfortable preterm neonates.

Simultaneous primary invasive cutaneous aspergillosis in two preterm twins: case report and review of the literature

BackgroundPrimary invasive cutaneous aspergillosis is a rare fungal infection that occurs mostly in immunocompromised patients. Newborns of very low birth weight present a high risk for this type of infection due to an immaturity of the cutaneous barrier and of the immune system.Case presentationWe describe here a case of simultaneous invasive cutaneous aspergillosis in two preterm twins. Two male preterm bichorionic biamniotic twins (A & B) were born at a general hospital by spontaneous normal delivery at 24 weeks and 6 days of gestation. They were transferred to our hospital where they receive surfactant, antibiotics and hydrocortisone. Six days later, twin A showed greenish lesions in the umbilical region. The spectrum of antibiotic therapy was broadened and fluconazole was added. The umbilical catheters of the two twins were removed and replaced by epicutaneo-cava venous catheters and the cultures were positive for Aspergillus fumigatus. Fluconazole was replaced in both twins by liposomal amphotericin B and the incubators were changed. The serum galactomannan was also positive for both twins. At day 10, yellowish lesions appeared in the abdominal region in twin B. He died on day 18 following complications related to his prematurity. Concerning the twin A, serum galactomannan was negative on day 30; liposomal amphotericin B was stopped 1 week later, with a relay by econazole (cream). His condition improved and on day 66 he was transferred for follow-up at the general hospital where he was born.ConclusionThe source of contamination by A. fumigatus was not identified, but other similar cases from the literature include construction work at or near the hospital, oximeter sensors, latex finger stalls, non-sterile gloves, humidifying chambers of incubators, bedding and adhesive tapes. The skin fragility of preterm newborns is an excellent potential entry point for environmental fungal infections. These cases highlight the importance of suspecting primary cutaneous aspergillosis in extremely low birth weight neonates with rapidly progressive necrotic lesions.

Optimizing Portable Pulse Oximeter Measurement Accuracy and Consistency During Exercise

Purpose: Monitoring oxygen saturation (SpO2) in some patient populations during exercise is vital. The objectives of this study were to determine whether under conditions of artificial hypoperfusion pulse oximeter performance during exercise was influenced by sensor type, attachment clip reinforcement, or a low pressure arm cuff. Methods: Six different portable oximeter models were tested on study participants at rest with a control (normothermic) and experimental (hypothermic) hand. Oximeters were then tested during treadmill walking at 1 and 2 mph with the experimental hand remaining hypothermic. Electrocardiographic measurements of heart rate were also taken simultaneously. Results: There were differences in SpO2 values between oximeter pairs following cold exposure at rest for most models (5 out of 6) but during walking for only 1 model. There were also differences between oximeter and electrocardiographic heart rate measurements for some models when study participants walked on a treadmill at 1 mph (1 out of 6) and 2 mph (3 out of 6). Conclusions: Results suggest that oximeter performance is better when measuring SpO2 than heart rate. Cold-induced hypoperfusion caused inaccuracies in SpO2 measurements, which were greater at rest than during exercise. Study results also suggest that some pulse oximeters perform better when the oximeter sensor attachment clip is reinforced with an elastic band.

Proof of concept non-invasive estimation of peripheral venous oxygen saturation

BackgroundPulse oximeters continuously monitor arterial oxygen saturation. Continuous monitoring of venous oxygen saturation (SvO2) would enable real-time assessment of tissue oxygen extraction (O2E) and perfusion changes leading to improved diagnosis of clinical conditions, such as sepsis.MethodsThis study presents the proof of concept of a novel pulse oximeter method that utilises the compliance difference between arteries and veins to induce artificial respiration-like modulations to the peripheral vasculature. These modulations make the venous blood pulsatile, which are then detected by a pulse oximeter sensor. The resulting photoplethysmograph (PPG) signals from the pulse oximeter are processed and analysed to develop a calibration model to estimate regional venous oxygen saturation (SpvO2), in parallel to arterial oxygen saturation estimation (SpaO2). A clinical study with healthy adult volunteers (n = 8) was conducted to assess peripheral SvO2 using this pulse oximeter method. A range of physiologically realistic SvO2 values were induced using arm lift and vascular occlusion tests. Gold standard, arterial and venous blood gas measurements were used as reference measurements. Modulation ratios related to arterial and venous systems were determined using a frequency domain analysis of the PPG signals.ResultsA strong, linear correlation (r2 = 0.95) was found between estimated venous modulation ratio (RVen) and measured SvO2, providing a calibration curve relating measured RVen to venous oxygen saturation. There is a significant difference in gradient between the SpvO2 estimation model (SpvO2 = 111 − 40.6*R) and the empirical SpaO2 estimation model (SpaO2 = 110 − 25*R), which yields the expected arterial-venous differences. Median venous and arterial oxygen saturation accuracies of paired measurements between pulse oximeter estimated and gold standard measurements were 0.29 and 0.65%, respectively, showing good accuracy of the pulse oximeter system.ConclusionsThe main outcome of this study is the proof of concept validation of a novel pulse oximeter sensor and calibration model to assess peripheral SvO2, and thus O2E, using the method used in this study. Further validation, improvement, and application of this model can aid in clinical diagnosis of microcirculation failures due to alterations in oxygen extraction.

A Comparison of Wireless Pulse Oximetry Technologies during SustainedShivering in Post-Operative Patients

Background: Pulse oximetry measures oxygen saturation in arterial blood non-invasively and is routinely practiced in many clinical settings. Technological advancements have expanded the performance capabilities of these devices to operate wirelessly, making pulse oximetry measures more convenient to obtain. Factors such as patient motion however can potentially complicate the ability to retrieve these measures. We examined the performance of two wireless pulse oximeters in patients who shiver postoperatively. Methods: Two additional pulse oximeter sensors (Masimo and Nonin) were added to 30 patients who shivered post-operatively and met eligibility criteria. Dropout rates were calculated by dividing the number of times that each instrument displayed no SpO2 or pulse rate value by the total time both sensors were in camera view for that subject. We used Wilcoxon matched pairs tests to compare the average time until the first reading displayed on the sensor for each device as well as dropout times. Dropout events were also compared using McNemar's test. Results: Drops in signal occurred in thirteen subjects. The Masimo sensor had more dropouts and a longer average drop duration, which was found to be statistically significant (p=0.02). Masimo's sensor required more s on average than Nonin's (8.86>8.78) to display the first reading, but this was not found to be statistically significant (p=0.90). Masimo also had a higher percentage of drops however this was not statistically significant (p=0.07). Conclusion: Overall incidence of shivering was low among patients in this setting (0.1%). More than 1/3 of subjects experienced drops during identical time intervals indicating that motion artifact may impact results regardless of technology. Additionally, Masimo's sensor is not meant for clinical use thereby raising questions regarding our statistically significant result in this particular setting. Combined with results from part I of this study, we cannot confidently detect a statistically significant difference between manufacturers.

SpO2 and Pulse Rate Data: A Comparison of Current Technologies during Sustained Shivering in Post-Operative Patients

Pulse oximetry is a noninvasive method of measuring the oxygen saturation (SpO2) of the arterial blood and is considered standard-of-care in post-operative settings. Patient motion or low perfusion can present challenges in obtaining accurate readings. Postoperative shivering occurs in anywhere from 5-65% of patients who have received general anesthesia and can manifest as continuous tremors and/or sporadic muscle movements. Objective: Compare the effect of post-operative shivering on functioning capabilities of two commercially available pulse oximeters. Methods: Two additional pulse oximeter sensors (Nonin 7500 Pulse Oximeter with 8000AA Sensor and Masimo Rad-8 with Rainbow DCI SC-200 Adult Reusable Sensor) were added to 40 shivering patients who met eligibility criteria. Shivering episodes were documented by recording the start and stop times for each episode as it occurred. Dropout rates for each device were calculated by dividing the amount of time that each instrument displayed no SpO2 or pulse rate value by the total time of the test. A 2-sample T-test was performed to compare dropout times of the devices and dropout rates were compared using a z-test for 2 proportions. Results: Drops in signal occurred in fourteen subjects. The Masimo sensor dropped 21 times, for an average of 40 seconds per drop and Nonin's dropped 16 times averaging 29 seconds per drop. Nonin's dropout rate of 0.108 was less than that of Masimo's at 0.149, however this difference was not found to be statistically significant (p=0.87). Conclusion: The incidence of shivering was very low among patients in this particular study setting (0.1%) For 5 different subjects, both sensors experienced drops during identical time intervals indicating that motion artifact may impact readings regardless of specific technology. Clinically significant shivering varied in duration among subjects therefore individual shiver rates varied as well. This preliminary analysis shows no significant difference between Nonin and Masimo sensors.

A Robust Motion Artifact Detection Algorithm for Accurate Detection of Heart Rates From Photoplethysmographic Signals Using Time-Frequency Spectral Features.

Motion and noise artifacts (MNAs) impose limits on the usability of the photoplethysmogram (PPG), particularly in the context of ambulatory monitoring. MNAs can distort PPG, causing erroneous estimation of physiological parameters such as heart rate (HR) and arterial oxygen saturation (SpO2). In this study, we present a novel approach, "TifMA," based on using the time-frequency spectrum of PPG to first detect the MNA-corrupted data and next discard the nonusable part of the corrupted data. The term "nonusable" refers to segments of PPG data from which the HR signal cannot be recovered accurately. Two sequential classification procedures were included in the TifMA algorithm. The first classifier distinguishes between MNA-corrupted and MNA-free PPG data. Once a segment of data is deemed MNA-corrupted, the next classifier determines whether the HR can be recovered from the corrupted segment or not. A support vector machine (SVM) classifier was used to build a decision boundary for the first classification task using data segments from a training dataset. Features from time-frequency spectra of PPG were extracted to build the detection model. Five datasets were considered for evaluating TifMA performance: (1) and (2) were laboratory-controlled PPG recordings from forehead and finger pulse oximeter sensors with subjects making random movements, (3) and (4) were actual patient PPG recordings from UMass Memorial Medical Center with random free movements and (5) was a laboratory-controlled PPG recording dataset measured at the forehead while the subjects ran on a treadmill. The first dataset was used to analyze the noise sensitivity of the algorithm. Datasets 2-4 were used to evaluate the MNA detection phase of the algorithm. The results from the first phase of the algorithm (MNA detection) were compared to results from three existing MNA detection algorithms: the Hjorth, kurtosis-Shannon entropy, and time-domain variability-SVM approaches. This last is an approach recently developed in our laboratory. The proposed TifMA algorithm consistently provided higher detection rates than the other three methods, with accuracies greater than 95% for all data. Moreover, our algorithm was able to pinpoint the start and end times of the MNA with an error of less than 1s in duration, whereas the next-best algorithm had a detection error of more than 2.2s. The final, most challenging, dataset was collected to verify the performance of the algorithm in discriminating between corrupted data that were usable for accurate HR estimations and data that were nonusable. It was found that on average 48% of the data segments were found to have MNA, and of these, 38% could be used to provide reliable HR estimation.

Orthostatic stress and area under the curve of photoplethysmography waveform

Background. Recent studies have shown that shape and morphology of photoplethysmography (PPG) waveform can provide useful information about cardiovascular system. These parameters namely pulse amplitude, pulse width, pulse rise time and pulse reflected delay have been studied independently and there is information about the interaction of these parameters. There is no detailed description of calculating these parameters. We have described a detailed algorithm for calculating these parameters. We also investigated a new parameter calculated using area under the curve of PPG waveform (AUCPPG). All parameter were calculated using finger probe oximeter sensor from 22 subjects before and after orthostatic stress. Changes in AUCPPG were compared against pulse interval, amplitude, width, rise time of PPG pulse and pulse reflection delay (PRD). Results. We found that all parameters showed a decrease with orthostatic stress. PPG pulse width parameter was very inconsistent and changed significantly based on small change in shape of PPG waveform. AUCPPG showed strong correlation with pulse amplitude (r 0.85) in supine position, but that relationship decreased in upright position (r 0.64) as reflected peaks became more distinct and separated. Multivariable regression showed that PRD and rise had negative influence on AUCPPG. Male subjects showed higher AUCPPG values. Conclusion. We conclude that all PPG based parameters are effected by subject’s position. Although AUCPPG is correlated with PAP width, it is an independent parameter that can be calculated more consistently than pulse width. From the results of our sample population we conclude AUCPPG is a better indicator of change in vascular tone than PAP amplitude or PAP width. Unlike other parameters AUCPPG incorporates the influence of both PAP and reflected waves.

The influence of external factors on the accuracy of non-invasive measuring of oxygen in blood

In this paper we investigated a pulse oximetry-based method for mobile devices. This method obtains bio-signals related to blood pulsation in transparent parts of body. The most widely accepted field for use of this method is hospital care. In these cases a pulse oximeter is the best solution for the monitoring of emergency patients. A promising field for pulse oximetry is physical exercise. It only requires simple clips such as ear-clips, finger-clips, headbands etc. However this method presents some difficulties: weak signal, noise ratio, motion artefacts, low perfusion. We used a MAX30100 Oximeter and Heart Rate Sensor integrated circuit to obtain signals of blood pulse waves from red and infrared light emission diodes (LED). This device measures the oxygen saturation of a person’s blood by placing an LED and a photodetector against the thin skin of a person’s body, such as a fingertip, wrist or earlobe. The MAX30100 is a 14-pin surface mount integrated circuit that contains sensors for measuring a person’s heart rate. It can also indirectly determine the oxygen saturation of a person’s blood. The MAX30100 provides a complete pulse oximetry and heart rate measurement solution for medical monitors and wearable fitness devices. As each LED emits light into a person’s finger, the integrated photodetector measures variations in light caused by changes in blood volume. An integrated 16-bit analog to digital converter (ADC) with programmable sample rate converts the photodetector output to a digital value. The MAX30100 filters out ambient light that can interfere with an accurate reading. Data are read through a serial I2C interface to computer for further processing. The LED current can be programmed from 0 to 50 mA with proper supply voltage. The LED pulse width can be programmed from 200 µs to 1.6 ms to optimize measurement accuracy and power consumption based on use cases. The SpO2 algorithm is relatively insensitive to the wavelength of the infrared LED, but the red LED’s wavelength is critical to correct interpretation of the data. The temperature sensor data can be used to compensate errors with ambient temperature changes. During the experiments we registered oxygen concentration values under different conditions. With low muscular activity we observed high stability and repeatability of measuring values under various exterior conditions. However, with high muscular activity there were various artefacts in the gauged signals that led to contortion of effects. We identified the boundaries of the validity of measuring and propose the use of an adapted filter in order to distinguish pulse waves from optical signals more reliably. These devices can be applied in fitness training , medical monitoring and used as wearable devices.

Effect of Sleep State and Position on Obstructive Respiratory Events Distribution in Adolescent Children.

This study aimed to examine the effect of sleep state (rapid eye movement [REM] versus non-rapid eye movement [NREM]) and position (supine versus non-supine position) on obstructive respiratory events distribution in adolescent population (ages 12 to 18 y). This was a retrospective study that included 150 subjects between the ages of 12 to 18 y with an apnea-hypopnea index (AHI) > 1/h. Subjects using REM sleep-suppressant medications and subjects with history of genetic anomalies or craniofacial syndromes were excluded. The median age was 14 y with interquartile range (IQR) of 13 to 16 y, 56% of patients were males and the median body mass index (BMI) z-score was 2.35 (IQR: 1.71-2.59) with 77.3% of patients fulfilling obesity criteria. Respiratory obstructive events were more common in REM sleep. The median REM obstructive AHI (OAHI) was 8.9 events per hour (IQR: 2.74-22.8), whereas the median NREM OAHI was 3.2 events per hour (IQR: 1.44-8.29; p < 0.001). African American adolescents had more REM obstructive events with median REM OAHI of 13.2 events per hour (IQR: 4.88-30.6), which was significantly higher than median REM OAHI of 4.94 (IQR: 2.05-11.36; p = 0.004) in white adolescents. Obstructive events were more common in supine position with higher median supine OAHI of 6.55 (IQR: 4-17.73) when compared to median non-supine OAHI of 2.94 (IQR: 1-6.54; p < 0.001). This study shows that sleep related obstructive respiratory events in the adolescents (12 to 18 y of age) occur predominantly in REM sleep and in supine position.

Vascular Occlusion Test to Dynamically Assess Microcirculation During Normothermic Pulsatile Cardiopulmonary Bypass.

To evaluate parameters of the vascular occlusion test (VOT) before, during, and after pulsatile cardiopulmonary bypass (CPB). Prospective, observational study. Single-center university hospital. Adult patients undergoing elective cardiac surgery with pulsatile CPB. An oximeter sensor and adult-sized pneumatic tourniquet were positioned at the right forearm. A VOT with a predefined ischemic time of 3 minutes was performed before, during, and after CPB. Changes in tissue oxygen saturation were recorded. Thirty-four patients who underwent cardiac surgery were enrolled in the study. The lowest tissue oxygen saturation measured during the ischemic challenge differed among all 3 stages of surgery, with median values of 62.9% before, 57.5% during, and 59.3% after perfusion (p<0.05). Both occlusion (p<0.001) and reperfusion (p<0.05) slopes were steeper after bypass compared with before initiating bypass, whereas the reperfusion time remained constant among the different time points. The microcirculatory function as demonstrated by changes in VOT parameters was enhanced during and after normothermic pulsatile CPB. Clinical relevance, however, needs to be further explored.

Body Sensor Network for Mobile Health Monitoring, a Diagnosis and Anticipating System

A system capable of mobile heath monitoring was designed and implemented from the first principles. The system is capable of measuring vital physiological parameters, interpret the measured signals, and provide a sense of monitoring and biofeedback to the user. In the case, a medical emergency is detected notifications are sent to a medical team for the analysis. The system was designed through the investigation of various biosignal extraction methods. An optical pulse oximeter sensor was designed along with the required software algorithms. The photoplethysmographic signals were extracted and used to calculate heart rate, saturation of oxygen, and pulse transits time. The pulse transit time was utilized in the estimation of continuous blood pressure measurement. The pulse oximetry implementation applies reflectance-based sensing on the user’s fingertip and palm. Skin temperature is also measurable through the use of a digital temperature sensor. The system is capable of providing feedback to the user by means of a smartphone application receiving data from the device through Bluetooth. The measurement of the proposed physiological parameters were successfully measured with the appropriate degree of accuracy required by medical standards. The system is capable of health monitoring through accurate measurements, providing the user with feedback and successfully identifying medical stress resulting in the sending of a notification to a medical doctor.

Efficacy of commercially available wipes for disinfection of pulse oximeter sensors

This study examined the effectiveness of commercially available disinfecting wipes and cosmetic wipes in disinfecting pulse oximeter sensors contaminated with pathogenic bacterial surrogates. Surrogates of potential biological warfare agents and bacterial pathogens associated with hospital-acquired infections (HAIs) were spotted on test surfaces, with and without an artificial test soil (sebum), allowed to dry, and then cleaned with different commercially available cleaning and disinfecting wipes or sterile gauze soaked in water, bleach (diluted 1:10), or 70% isopropanol. The percentage of microbial survival and an analytical estimation of remaining test soil on devices were determined. Wipes containing sodium hypochlorite as the active ingredient and gauze soaked in bleach (1:10) were the most effective in removing both vegetative bacteria and spores. In the presence of selective disinfectants, sebum had a protective effect on vegetative bacteria, but not on spores. The presence of sebum reduces the cleaning efficiency of some commercially available wipes for some select microbes. Various commercial wipes performed significantly better than the designated cleaning agent (70% isopropanol) in disinfecting the oximetry sensor. Cosmetic wipes were not more effective than the disinfecting wipes in removing sebum.