Jiewen Zheng

Design of Automatic Fall Detector for Elderly Based on Triaxial Accelerometer

Falls in elderly people have been recognized as a major health problem in aging population. This paper describes the development of an accurate, accelerometer based fall detector capable of locating the wearer and sending alarm short messages (SMS). The device worn on the waist uses a two-stage fall detection algorithm, which senses rapid impact and body orientation of the wearer. To evaluate the device and the algorithm, an experiment on 5 subjects was conducted. The device is especially adapted to safely and accurately monitor elderly people without influencing their privacy and comfort. It is hoped that such a device will promote an integrated approach to the management of falls of elderly in the community.

Buccal partial pressure of carbon dioxide outweighs traditional vital signs in predicting the severity of hemorrhagic shock in a rat model.

BACKGROUNDnHemorrhagic shock (HS) is a leading cause of death in both military and civilian settings. Researchers have investigated different parameters as predictors of HS, but reached inconsistent conclusions. We hypothesized that buccal partial pressure of carbon dioxide (PCO2) was a better predictor of HS than traditional vital signs.nnnMATERIALS AND METHODSnTwenty-four anesthetized Wistar rats were randomly divided into four groups: one control group (no bleeding) and three surgical groups (25%, 35%, and 45% blood loss). Hemorrhage was induced by withdrawing blood from the left femoral artery over a period of 30xa0min. After that, resuscitation was performed on animals in surgical groups using the Ringer lactate solution. Buccal PCO2 was continuously measured by a newly designed sensor holder during the experiments. Traditional vital signs, cardiac output, base excess, and microvascular perfusion (MPF) were also measured or calculated.nnnRESULTSnBuccal PCO2 differed significantly among four groups beginning at 20xa0min, approximately 10xa0min earlier than the shock index and more earlier than the heart rate, systolic blood pressure, and mean arterial pressure. Buccal PCO2 correlated well with cardiac index and the changes in MPF. The correlation coefficients with cardiac index, chest MPF, and upper-limb MPF for buccal PCO2 were 0.781, -0.879, and -0.946, respectively. Besides, buccal PCO2 showed a good value for predicting mortality. Furthermore, an approximate critical threshold of buccal PCO2 was also identified for predicting the severity of HS.nnnCONCLUSIONSnBuccal PCO2 was a noninvasive, sensitive indicator of HS than traditional vital signs and may help on-scene rescuers administer early treatment of injured patients.

An optimal closed-loop control strategy for mechanical chest compression devices

OBJECTIVESnThe widespread application of chest compression (CC) as a first aid measure inevitably has the potential for both harm and benefit. The present study was therefore undertaken to design an optimal CC closed-loop control strategy (OCCCS) for mechanical CC devices that will present an effective trade-off between the risk of chest injury and the benefit of blood flow during CPR. Additionally, to evaluate the CC performance of the OCCCS, the differences between the OCCCS and the traditional mechanical CC method (TMCM) of performing standard CC were explored.nnnMETHODSnUsing the computer simulation technique, partial pressure of end-tidal CO₂ (PETCO2) and human chest stiffness are simulated based on the Babbs model in present study. PETCO2 was regarded as a benefit factor (BF), which was divided into 3 levels, while chest stiffness was regarded as a risk factor (RF), which was divided into 4 levels. A benefit versus risk index (BRI) was also constructed for the comprehensive evaluation of risk and benefit. An OCCCS was developed with the combination of the BF, RF, BRI and fuzzy control strategy. A comparison between the OCCCS and TMCM was then performed based on computer simulations.nnnRESULTSnThe OCCCS obtained a greater BRI and a better trade-off between risk and benefit than the TMCM in 6 out of a total 9 cases, and the OCCCS also resulted in a significantly improved cardiac output (CO) and PETCO2 in 6 of the 9 cases. The mean BRI, CO and PETCO2 resulting from the OCCCS were 5.69, 1.45 L/min and 15.51 mmHg, respectively, while the mean BRI, CO and PETCO2 resulting from TMCM were 4.76, 1.18 L/min and 13.26 mmHg, respectively.nnnCONCLUSIONSnThe OCCCS can provide safer and more effective CC during cardiopulmonary resuscitation (CPR) compared to the TMCM, and has great potential in the future mechanical CC device development.

A Novel Method of Measuring the Depth of Manual Chest Compressions During CPR

The present study offered a novel method to determine the depth of manual chest compressions during Cardiopulmonary Resuscitation (CPR). This method was based on the accelerometer and the gyroscopes. In our study, several algorithms of measuring the depth of compressions with one accelerometer and two gyroscopes were established. We also built an experimental platform to monitor the movement of rescuers hand. In order to validate our method, a series of tests based on our experimental platform were carried out. Results showed that this method of measuring the depth of chest compressions was feasible and simple, and that the data acquired by our method were reliable and accurate. This novel method will provide assistance and a real-time monitor for the rescuers during CPR.