S P Preejith

A novel system to tackle hospital acquired pressure ulcers

Hospital acquired pressure ulcers (HAPUs) is a major problem that affects around one in twenty patients who are admitted in hospital with sudden illness. These ulcers often occur when patients have limited mobility and cannot change positions in bed on their own. Traditionally, the occurrence of HAPUs has been minimized by turning the patient every 2 hours to alternating lateral and supine positions, and by using pressure redistributing mattresses. In many healthcare facilities, such a patient repositioning schedule is not always maintained owing to low caregiver compliance to turning protocols. Difficulty in monitoring patient position continuously, lack of turn reminders/alerts and suboptimal caregiver staffing ratio increases the occurrence of HAPUs. A novel method to address the need for improved pressure ulcer prevention is presented. The proposed method consists of a wearable device which continuously monitors the patients position and communicates wirelessly with a tablet which enables alerts to be sent to the caregiver when a patient turn is due in accordance with the protocol adopted by the hospital. The patients position is continuously monitored and the turning procedure carried out is logged and updated on the hospitals cloud system, thereby enabling centralized monitoring. Under a controlled setting, system was able to continuously monitor patients position and can accurately detect standard patient positions.Hospital acquired pressure ulcers (HAPUs) is a major problem that affects around one in twenty patients who are admitted in hospital with sudden illness. These ulcers often occur when patients have limited mobility and cannot change positions in bed on their own. Traditionally, the occurrence of HAPUs has been minimized by turning the patient every 2 hours to alternating lateral and supine positions, and by using pressure redistributing mattresses. In many healthcare facilities, such a patient repositioning schedule is not always maintained owing to low caregiver compliance to turning protocols. Difficulty in monitoring patient position continuously, lack of turn reminders/alerts and suboptimal caregiver staffing ratio increases the occurrence of HAPUs. A novel method to address the need for improved pressure ulcer prevention is presented. The proposed method consists of a wearable device which continuously monitors the patients position and communicates wirelessly with a tablet which enables alerts to be sent to the caregiver when a patient turn is due in accordance with the protocol adopted by the hospital. The patients position is continuously monitored and the turning procedure carried out is logged and updated on the hospitals cloud system, thereby enabling centralized monitoring. Under a controlled setting, system was able to continuously monitor patients position and can accurately detect standard patient positions.

Wearable ECG platform for continuous cardiac monitoring

An ultra-low power ECG platform for continuous and minimally intrusive monitoring for systems with minimal processing capabilities, is presented in this paper. The platform is capable of detecting abnormalities in the ECG signal by extracting and analyzing features related to various cardiac trends. The platform is built to continuously operate on any of the 12 leads and the presented work includes a single lead implementation that works on lead I or II. A single lead, wearable ECG patch that can detect rhythm based arrhythmias and continuously monitor beat-to-beat heart rate and respiratory rate has been developed. In addition, the device stores raw ECG waveform locally and is designed to run for 10 days on a single charge. The ECG patch works in conjunction with a front end device or tablet and updates the results on the tablet interface. Upon detection of an abnormality or an arrhythmia the device switches to an ECG visualization mode enabling manual analysis on the acquired signal. The front end device also functions as a gateway for remote monitoring. The functionality and processing capabilities of the platform along with the validation tests carried out in a controlled setting are presented.An ultra-low power ECG platform for continuous and minimally intrusive monitoring for systems with minimal processing capabilities, is presented in this paper. The platform is capable of detecting abnormalities in the ECG signal by extracting and analyzing features related to various cardiac trends. The platform is built to continuously operate on any of the 12 leads and the presented work includes a single lead implementation that works on lead I or II. A single lead, wearable ECG patch that can detect rhythm based arrhythmias and continuously monitor beat-to-beat heart rate and respiratory rate has been developed. In addition, the device stores raw ECG waveform locally and is designed to run for 10 days on a single charge. The ECG patch works in conjunction with a front end device or tablet and updates the results on the tablet interface. Upon detection of an abnormality or an arrhythmia the device switches to an ECG visualization mode enabling manual analysis on the acquired signal. The front end device also functions as a gateway for remote monitoring. The functionality and processing capabilities of the platform along with the validation tests carried out in a controlled setting are presented.

Design and preliminary analysis of a multifrequency bioimpedance measurement scheme

Bioimpedance Spectroscopy is a non-invasive, non-ionizing technique used for characterization of healthy and pathological tissues based on spectrum of their electrical properties. This can potentially be used as an adjunct diagnostic tool because spectral measurement provides much more clinically relevant information about the tissue than single frequency measurement. This paper presents a multifrequency bioimpedance measurement scheme to measure impedance varying from 1.6 Ω to 1.6 kΩ in the β dispersion region between 500 Hz and 1 MHz. In order to improve the accuracy of measurement, a three reference calibration algorithm based on quadratic Lagrange interpolation is employed which corrects the systematic errors mathematically. Preliminary experimental results show good agreement between calibrated values and standard values with a maximum relative magnitude error of 1.3 % and a maximum relative phase error of 0.6° over the entire frequency range.

Design, development and clinical validation of a wrist-based optical heart rate monitor

Development in the field of sensor technology, hardware miniaturization, ubiquitous computing and connected solutions paved the way for the development of wearables for continuous physiological parameter monitoring. Continuous heart rate monitoring with clinical accuracy using reflectance photoplethysmogram signals from wrist is highly challenging and presents a potential area of research. In this work, we present a wearable device in a wrist watch form factor for heart rate monitoring. The device runs on a low power ARM cortex M4 microcontroller and integrates a BLE (Bluetooth Low energy) module for wireless connectivity. A heart rate computation algorithm using reflectance photoplethysmography and a 3 axes accelerometer for motion artifact removal is presented in the paper. Heart rate computed by the wrist worn device was validated against heart rate measured using Masimo Radical-7 on 256 subjects. The validation study was conducted in a hospital setting for a duration of 1 month, after obtaining the ethics committee approval and informed consent from the subjects. Details of the experimental setup, clinical validation protocol and observations and inferences made from the study are presented.

Printed, skin-mounted hybrid system for ECG measurements

In this paper we report a design and fabrication process for a screen printed, skin-mounted hybrid system for electrocardiogram (ECG) measurements. The system consists of printed electrodes on a stretchable bandage substrate designed to be attached to the chest, an electronics module, and a data receiving device. The electronics unit is reversibly attached to the single-use electrode bandage to measure the ECG data. The ECG data is then transmitted to a mobile device via Bluetooth Low Energy and the mobile device then displays the data graphically and sends it further a cloud for storing and further analysis. The attained quality of the measured ECG signals is fully satisfactory to compute important cardiac parameters and after preprocessing the signal could be used for more profound analysis of ECG wave shapes.

Effectiveness of a continuous patient position monitoring system in improving hospital turn protocol compliance in an ICU: A multiphase multisite study in India

Purpose Hospital-acquired pressure ulcers are a significant cause of morbidity and consume considerable financial resources. Turn protocols (repositioning patients at regular intervals) are utilized to reduce incidence of pressure ulcers. Adherence to turn protocols is particularly challenging for nursing teams, given the high number of interventions in intensive care unit, and lack of widely available tools to monitor patient position and generate alerts. We decided to develop and evaluate usefulness of a continuous patient position monitoring system to assist nurses in improving turn protocol compliance. Methods We conducted a prospective, non-randomized, multiphase, multicentre trial. In Phase I (control group), the function of the device was not revealed to nurses so as to observe their baseline adherence to turn protocol, while Phase II (intervention group) used continuous patient position monitoring system to generate alerts, when non-compliant with the turn protocol. All consecutive patients admitted to one of the two intensive care units during the study period were screened for enrolment. Patients at risk of acquiring pressure ulcers (Braden score < 18) were considered for the study (Phase I (N = 22), Phase II (N = 25)). Results We analysed over 1450 h of patient position data collected from 40 patients (Phase I (N = 20), Phase II (N = 20)). Turn protocol compliance was significantly higher in Phase II (80.15 ± 8.97%) compared to the Phase I (24.36 ± 12.67%); p < 0.001. Conclusion Using a continuous patient position monitoring system to provide alerts significantly improved compliance with hospital turn protocol. Nurses found the system to be useful in providing automated turn reminders and prioritising tasks.

A novel sensor for wrist based optical heart rate monitor

The growing demands of continuous healthcare and hence physiological monitoring necessitates a system with high reliability and accuracy. Wearable used for continuous cardiological parameter estimation from wrist use reflective photoplethysmography technique that has certain limitations which are imperative. One such constraint is skin pigmentation of the subject. In the present work a sensor module design is proposed addressing to the anomalies due to optical properties of skin. A novel 590 nm (yellow-orange) wavelength based optical system is tailored suitably to maximize the signal quality acquired. The proposed setup is validated on a conglomeration of subjects in terms of age, gender and skin tone. A generous agreement between coherent measures for signal quality shows that the proposed wavelength holds an advantage over its shorter counterpart when subjected to varied skin pigmentation levels. A maximum improvement factor of 71 is observed in case of perfusion index, 31 for pulsatile strength and 3 for SNR. The details of sensor design, experimental setup, validation protocol, observations and inferences drawn from the study are presented.

Design and implementation of a hand-to-hand multifrequency bioimpedance measurement scheme for Total Body Water estimation

Human body has an intricate regulatory mechanism to maintain the Total Body Water (TBW) content and thereby sustain normal hydration levels. However, chronic fluid variations can occur and are often associated with pathological conditions like renal insufficiency and/or medications. Hence, a sensitive and precise estimation of TBW is of much clinical significance. Recent years have seen the emergence of Bioimpedance Spectroscopy (BIS) as a potential tool for TBW estimation with a unique capacity to differentiate between the extracellular and intracellular water content. The design and implementation of a hand-to-hand bioimpedance spectrometer for TBW estimation which can measure impedances within the range of 5.3 Ω to 5.3 kΩ in the β dispersion region of tissue between 500 Hz and 1 MHz is presented in this paper. A three reference calibration algorithm based on quadratic Lagrange interpolation is employed in order to mathematically correct the systematic errors in the measurements. The Cole parameters are extracted from the calibrated spectroscopy measurements by applying a Non-Linear Least Square (NLLS) iterative fitting on the resistance spectrum and further used to determine the extracellular, intracellular and total body water content. Measurements are done on 18 subjects (9 males and 9 females, age 23.3 ± 2.5 years, mean ± SD) at 17 different frequencies within the range of 3 kHz to 1 MHz. TBW estimated using the implemented BIS device prototype is validated against an FDA approved segmental body composition monitor from TANITA. The estimates show a strong positive correlation with Pearsons r of 0.83. The Bland-Altman analysis done on two systems indicate a similarity in TBW estimations with a bias of only 0.17 L while the 95% limits of agreement lie between −6.47 L and 6.81 L.

A wrist worn SpO 2 monitor with custom finger probe for motion artifact removal

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.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 reflectance photoplethysmography based device to detect circulatory disruptions

We study the potential of reflectance photoplethysmography (PPG) in monitoring free flaps for arterial and venous thrombosis in post-surgical scenarios. Circulatory disruptions due to thrombosis were simulated using limb ischemia method on 30 volunteers. Arterial and venous occlusions were conducted in this study. The variation in blood flow in the region of interest was captured by a custom built sensor and data acquisition system using dual wavelength reflectance photoplethysmography. The main chromophores in blood, oxygenated and reduced hemoglobin, showed good variation to visible - near infrared wavelengths with concentration and volume changes. Sensitivity of the prototype device in detecting arterial and venous circulation disruptions was evaluated at various different threshold levels of signal parameters. The device showed strong capability to accurately detect circulatory disruptions and has potential in post-surgical monitoring of free flaps.