Objective To investigate the changes of respiratory mechanics in response to elevated respiratory central drive and their impacts on the inspiratory signals detection.Methods 10 normal volunteers were recruited for the study from the colleagues of the State Key Laboratory of Respiratory Disease. Rebreathing method was used to increase the end expiratory PCO2 ( PCO2 -ET) to the subject’s maximal tolerance in order to stimulate the increase of respiratory central drive. The changes of respiratory mechanics in response to elevated respiratory central drive and their impacts on the initiation signals of inspiration were observed.Results After re-breathing, the average maximal tolerated PCO2 -ET was ( 81. 2 ±6. 6) mm Hg. As the PCO2 -ET rising, electromyogram of diaphragmatic muscle ( RMSdi ) ,transdiaphragmatic pressure ( Pdi ) and tidal volume ( VT ) increased progressively while the time of respiratory cycle ( Ttot ) shorten gradually. As the PCO2 -ETlevel increased frombaseline [ PCO2 -ET( level-0) ] to the maximal level [ PCO2 -ET( level-4) ] , RMSdi increased from( 17. 17 ±12. 41) μV to ( 147. 99 ±161. 64) μV,Pdi and VT increased from ( 7. 5 ±1. 7) cmH2O and ( 0. 68 ±0. 27) L to ( 26. 13 ±11. 51) cm H2O and ( 2. 21 ±0. 37) L respectively, while Ttot shorten from ( 2. 91 ±0. 85) s to ( 1. 92 ±0. 39) s. These four parameters of respiratory mechanics, RMSdi, Pdi, VT and Ttot, were highly correlated linearly with PCO2 -ET ( r value was 0. 956, 0. 973,0. 956 and 0. 89 respectively, all P lt;0. 001) . At the start of inspiration, the first detectable signal was electromyogramof diaphragmatic muscle ( RMSdi) , followed by mouth pressure ( Pm)and inspiratory flow ( Flow) on time sequence. As the rising of PCO2 -ET, the time lag of Pmand Flow from RMSdi after the initiation of inspiration increased gradually. However, the time lag between Flow and Pm remained constant. Conclusions At the start of inspiration, the signal of RMSdi appears first as compared with Pm and Flow. As the rising of PCO2 -ET, the time lag of Pmand Flow fromRMSdi after the initiation of inspiration increased gradually, suggesting RMSdi is more sensitive inspiratory signal, which might be used for triggering of ventilator in order to improve the synchronization, especially in the situation of elevated respiratory central drive.
The validity and reasonableness of emotional data are the key issues in the cognitive affective computing research. Effects of the emotion recognition are decided by the quality of selected data directly. Therefore, it is an important part of affective computing research to build affective computing database with good performance, so that it is the hot spot of research in this field. In this paper, the performance of two classical cognitive affective computing databases, the Massachusetts Institute of Technology (MIT) cognitive affective computing database and Germany Augsburg University emotion recognition database were compared, their data structure and data types were compared respectively, and emotional recognition effect based on the data were studied comparatively. The results indicated that the analysis based on the physical parameters could get the effective emotional recognition, and would be a feasible method of pressure emotional evaluation. Because of the lack of stress emotional evaluation data based on the physiological parameters domestically, there is not a public stress emotional database. We hereby built a dataset for the stress evaluation towards the high stress group in colleges, candidates of postgraduates of Ph.D and master as the subjects. We then acquired their physiological parameters, and performed the pressure analysis based on this database. The results indicated that this dataset had a certain reference value for the stress evaluation, and we hope this research can provide a reference and support for emotion evaluation and analysis.
Surface electromyogram (sEMG) may have low signal to noise ratios. An adaptive wavelet thresholding technique was developed in this study to remove noise contamination from sEMG signals. Compared with conventional wavelet thresholding methods, the adaptive approach can adjust thresholds based on different signal to noise ratios of the processed signal, thus effectively removing noise contamination and reducing distortion of the EMG signal. The advantage of the developed adaptive thresholding method was demonstrated using simulated and experimental sEMG recordings.
In this paper, the response of individual's physiological system under psychological stress state is discussed, and the theoretical support for psychological stress assessment research is provided. The two methods, i.e. the psychological stress assessment of questionnaire and physiological parameter assessment used for current psychological stress assessment are summarized. Then, the future trend of development of psychological stress assessment research is pointed out. We hope that this work could do and provide further support and help to psychological stress assessment studies.
For the questions of deeply researching abnormal neuromuscular coupling and better evaluating motor function of stroke patients with motor dysfunction, an effective intermuscular coherence analysis method and index are studied to explore the neuromuscular oscillation and the pathomechanism of motor dysfunction, based on which an assessment standard of muscle function is established. Firstly, the contrastive analysis about the intermuscular coherence of antagonistic muscle of affected and intact upper limbs of stroke patients was conducted. Secondly, a significant indicator of Fisher's Z-transformed coherence significant indicator was defined to quantitatively describe the coupling differences in certain functional frequency domain between surface electromyogram (sEMG) of affected and intact sides. Further more, the relationship between intermuscular coherence and motor task was studied. Through the analysis of intermuscular coherence during elbow flexion-extension of affected and intact sides, we found that the intermuscular coherence was associated with motor task and the stroke patients exhibited significantly lower beta-band intermuscular coherence in performing the task with their affected upper limbs. More conclusion can be drawn that beta-band intermuscular coherence has been found concerned with Fugle-Meyer scale, which indicates that beta-band intermuscular coherence could be an index assisting in evaluating motor function of patients.
We carried out study on surface electromyogram (sEMG) signal generated from cluster muscles in trunk and lower limbs on condition of human body walking with heavily burdened shoulder to explore functional status and fatigue property of human muscles and to offer an important reference for finding better ways of loading, improving the performance and design of backpack as well as weight-bearing system more suitable for ergonomics. We measured and obtained surface electromyography signals from the primary muscles clusters in neck, shoulder, back and leg of 20 test recipients loaded with different burdens on their shoulders. The eigenvalue of mean power frequency (MPF) were processed with SPSS 16.0. It could be concluded that with the increase of loading weights, male are more likely to be fatigued due to dramatic decrease of trapezius' MPF. While for the female test recipients, the cervical extensor muscles' MPF dropped significantly and were more easily fatigued. Moreover, there was a remarkable difference in terms of electromyography signal before and after the weight reaches certain limit (P<0.05) . The maximum weight limit loaded on shoulders for man is 12% of the total bodyweight while such limit for woman is just 9%.
Extraction uterine contraction signal from abdominal uterine electromyogram (EMG) signal is considered as the most promising method to replace the traditional tocodynamometer (TOCO) for detecting uterine contractions activity. The traditional root mean square (RMS) algorithm has only some limited values in canceling the impulsive noise. In our study, an improved algorithm for uterine EMG envelope extraction was proposed to overcome the problem. Firstly, in our experiment, zero-crossing detection method was used to separate the burst of uterine electrical activity from the raw uterine EMG signal. After processing the separated signals by employing two filtering windows which have different width, we used the traditional RMS algorithm to extract uterus EMG envelope. To assess the performance of the algorithm, the improved algorithm was compared with two existing intensity of uterine electromyogram (IEMG) extraction algorithms. The results showed that the improved algorithm was better than the traditional ones in eliminating impulsive noise present in the uterine EMG signal. The measurement sensitivity and positive predictive value (PPV) of the improved algorithm were 0.952 and 0.922, respectively, which were not only significantly higher than the corresponding values (0.859 and 0.847) of the first comparison algorithm, but also higher than the values (0.928 and 0.877) of the second comparison algorithm. Thus the new method is reliable and effective.
Muscle fatigue has widespread application in the field of rehabilitation medicine. The paper studies the muscle fatigue using surface electromyogram (sEMG) in the background of rehabilitation training system. The sEMG and ventilatory threshold of vastus lateralis, rectus femoris and erector spinae are collected synchronously and the electromyogram fatigue threshold (EMGFT) of different sEMG was analyzed by increasing load cycling experiments of 10 healthy subjects. This paper also analyzes the effect of isotonic and isometric contraction on EMGFT. Results showed that the appeared time of EMGFT was earlier than that of ventilatory threshold in the incremental load cycling. While the differences were subtle and EMGFT was verified to be effective. EMGFT has been proven effective for different muscle contraction by comparing the EMGFT of vastus lateralis and erector spinae. EMGFT could be used to keep muscle injuries from overtraining in the process of rehabilitation. Therefore, EMGFT has a great significance for femoral shaft fractures’s fatigue monitoring in rehabilitation training.
The tilted supine position has been evaluated to be one of the significantly effective approaches to prevent bedsore of the patients in the bedridden state. Thus, it has deeply positive influences that in view of dynamics this study explores how the position works. Based on the anatomical theories, this study formulates the human dynamic model. Furthermore, the dynamic simulation of three usual postures in tilted supine position including lying on back, lying with one knee bent and lying with the upper and lower limb on one side lifted is carried out. Therefore, the changes of the three driving forces named as chest force, waist force and thigh force in the tilted supine position can be observed. In order to verify the validity of this simulation, this study obtains the electromyogram measurements of ectopectoralis, external obliques and thigh muscles which are respectively close to the chest, waist and thigh by conducting the human force measurements experiment. The result revealed that in terms of range and trend, the experimental data and simulation’s data were consistent. In conclusion, the changes of these muscles in the supine position movements are researched efficiently by both this experiment and the dynamic simulation. Besides, the result is crucially key to find the mechanism of human’s tilted supine position movements.