Unconstrained detection of ballistocardiogram and heart rate based on vibration acceleration / 生物医学工程学杂志

The requirement for unconstrained monitoring of heartbeat during sleep is increasing, but the current detection devices can not meet the requirements of convenience and accuracy. This study designed an unconstrained ballistocardiogram (BCG) detection system using acceleration sensor and developed a heart rate extraction algorithm. BCG is a directional signal which is stronger and less affected by respiratory movements along spine direction than in other directions. In order to measure the BCG signal along spine direction during sleep, a 3-axis acceleration sensor was fixed on the bed to collect the vibration signals caused by heartbeat. An approximate frequency range was firstly assumed by frequency analysis to the BCG signals and segmental filtering was conducted to the original vibration signals within the frequency range. Secondly, to identify the true BCG waveform, the accurate frequency band was obtained by comparison with the theoretical waveform. The J waves were detected by BCG energy waveform and an adaptive threshold method was proposed to extract heart rates by using the information of both amplitude and period. The accuracy and robustness of the BCG detection system proposed and the algorithm developed in this study were confirmed by comparison with electrocardiogram (ECG). The test results of 30 subjects showed a high average accuracy of 99.21% to demonstrate the feasibility of the unconstrained BCG detection method based on vibration acceleration.

Smart technologies toward sleep monitoring at home

With progress in sensors and communication technologies, the range of sleep monitoring is extending from professional clinics into our usual home environments. Information from conventional overnight polysomnographic recordings can be derived from much simpler devices and methods. The gold standard of sleep monitoring is laboratory polysomnography, which classifi es brain states based mainly on EEGs. Single-channel EEGs have been used for sleep stage scoring with accuracies of 84.9%. Actigraphy can estimate sleep effi ciency with an accuracy of 86.0%. Sleep scoring based on respiratory dynamics provides accuracies of 89.2% and 70.9% for identifying sleep stages and sleep effi ciency, respectively, and a correlation coeffi cient of 0.94 for apnea–hypopnea detection. Modulation of autonomic balance during the sleep stages are well recognized and widely used for simpler sleep scoring and sleep parameter estimation. This modulation can be recorded by several types of cardiovascular measurements, including ECG, PPG, BCG, and PAT, and the results showed accuracies up to 96.5% and 92.5% for sleep effi ciency and OSA severity detection, respectively. Instead of using recordings for the entire night, less than 5 min ECG recordings have used for sleep effi ciency and AHI estimation and resulted in high correlations of 0.94 and 0.99, respectively. These methods are based on their own models that relate sleep dynamics with a limited number of biological signals. Parameters representing sleep quality and disturbed breathing are estimated with high accuracies that are close to the results obtained by polysomnography. These unconstrained technologies, making sleep monitoring easier and simpler, will enhance qualities of life by expanding the range of ubiquitous healthcare.

Complications and Revision Rate as the Type of Prosthesis of Total Elbow Replacement: Long-term Follow-up in Korea / 대한정형외과학회잡지

PURPOSE: Few studies have compared the outcomes, complications and revision rate of a total elbow replacement (TER) prosthetic design. This study examined a series of patients with semiconstrained and unconstrained total elbow replacements (TER) and evaluated them for any functional differences, complications and revision rates that might be attributable to the prosthetic design. MATERIALS AND METHODS: A total 78 cases of primary TER was performed in 71 patients. Their mean age at TER was 54 years. The causes of TER were rheumatoid arthritis in 42, post-traumatic arthritis and osteoarthritis 24 and 5 patients, respectively. Unconstrained and semiconstrained TER was employed in 35 and 43 cases, respectively. The end results of TER by the Mayo elbow performance score (MEPS), their elbow range of motion before and after surgery, their complications and revision rates after an average 13 year follow-up were evaluated. RESULTS: The MEPS was improved from 33 points pre-operatively to 87 points post-operatively (p<0.001). Active flexion-extension elbow motions were also improved markedly from 27degrees-86degrees pre-operatively to 16degrees-128degrees postoperatively (p<0.001). There was no significant difference between the semiconstrained and unconstrained TER in the post-operative MEPS (p=0.764) and range of motion (p=0.728). The complication rate was much higher in the unconstrained groups than in the semiconstrained group (p=0.014). The mean total revision rate was 29.5%. There was no significant difference in revision rate between the unconstrained and semiconstrained groups (p=0.402). Loosening was found in a total of 12 cases (15.4%). There was also no significant difference in loosening between the semiconstrained and unconstrained groups (p=0.382). CONCLUSION: Favorable results of MEPS and elbow motion were obtained in both the unconstrained and semiconstrained types after an average 13 year follow up after TER. However, the semiconstrained type of TER showed a lower complication rate than the unconstrained type of TER.

Total Ankle Arthroplasty : Short Term follow up Results of Semiconstrained Type and Unconstrained Type / 대한족부족관절학회지

PURPOSE: The purpose of this study is to compare the two prosthesis that used for total ankle arthroplasty. MATERIALS AND METHODS: From Sept. 2003 to Jun 2006, 13 patients and 14 ankles that could be follow up more than 1 months. Semiconstrained type (Group I, 7 cases) and Unconstrained type (Group II, 7 cases) were used for total ankle arthroplasty. Mean age was 63.2 year-old, 12 ankles are men and 2 ankles were women. Mean follow up periods were 29 months. The criteria to compare the clinical result were postoperative range of motion, AOFAS score and residual bone stock of medial malleolus. RESULTS: Postoperative range of motion of group I was 43.6+/-9.4 degrees and of group II was 50.7+/-7.3 degrees (p=0.115). Postoperative AOFAS score of group I was 77.1+/-13.0 points and of group II was 86.0+/-5.7 points (p=0.094). Resected bone stock in medial malleolus of group I was 10.7+/-2.5 mm and of group II was 5.1+/-1.2 mm (p=0.003). Total number of complication in our study was 9 cases. 3 cases were a malleolar fracture, two occurred at intra-operation, the other at follow-up period. Re-operation was done in 6 cases, 3 cases were calcaneal corrective osteotomy, 2 cases were resection of a heterotopic bone and one case was pedicular flap operation for skin problem. CONCLUSION: In our hospital, mobile bearing type prosthesis shows good result than a semiconstrained type in respect of residual bone stock in medial malleolus. Postoperative range of motion and AOFAS score between two groups shows no significant difference. But small number of patients and short term follow up period is a defect in our study, afterward more population and long term follow up period are needed.

AN OPTIMAL SELF-SCALING STRATEGY TO THE MODIFIED SYMMETRIC RANK ONE UPDATING / 药物分析学报

In the paper, the optimal self-scaling strategy to the modified symmetric rank one (HSR1) update, which satisfies the modified quasi-Newton equation, is derived to improve the condition number of the updates. The scaling factors are derived from minimizing the estimate of upper bounds on the condition number of the updating matrix. Theoretical analysis, and numerical experiments and comparisons show that introducing the optimal scaling factor into the modified symmetric rank one update preserves the positive definiteness of updates, and greatly improves the stability and numerical performance of the modified symmetric rank one algorithm.

Comparison of biomechanics between constrained and unconstrained anterior cervical plate under vertical load / 第二军医大学学报

constrained plate group(P