术前连接气管插管下体位摆放的改进与护理

目的减少体位变动过程中增加气道阻力,防止术后麻醉恢复过程中气道损伤。方法将临床60例体位翻动患者按照体位翻动变化过程分为平卧搬动、侧卧搬动、俯卧搬动3阶段,分别比较改进前后体位移动时动态阻力变化隋况,比较改进前后体位移动后管道移位率及麻醉后护理评分。结果改进前后平卧搬动、侧卧搬动、俯卧搬动阶段分别比较体位移动前后安全纬度动态阻力、麻醉后护理评分及咽通气道使用率,差异均有统计学意义（P〈0.05）。结论术前连接气管插管下改进体位摆放方法可增加安全纬度,减少口咽通气道使用率。     

Modelling stabilograms with hidden Markov models

Hidden Markov models are an effective computational method for modelling and interpreting digital signals of biological, as well as other, origin. In the current investigation, we explored whether hidden Markov models can be used to control and represent phenomena in human balance signals recorded from subjects standing on a force platform. Additionally, our aim was to classify healthy controls and patients who suffered from Menière's disease into their own classes. Hidden Markov models were capable of these tasks and of overcoming such disturbances as noise and other unforeseen perturbations in balance signals, which are inherently complex and possibly difficult to visually specify.     

Muscle synergies during shifts of the center of pressure by standing persons

Movements by a standing person are commonly associated with adjustments in the activity of postural muscles to cause a desired shift of the center of pressure (COP) and keep balance. We hypothesize that such COP shifts are controlled (stabilized) using a small set of central variables (muscle modes, M-modes), while each M-mode induces changes in the activity of a subgroup of postural muscles. The main purpose of this study has been to explore the possibility of identification of muscle synergies in a postural task using the framework of the uncontrolled manifold (UCM) hypothesis employing the following three steps in data analysis: (i) Identification of M-modes: Subjects were asked to release a load from extended arms through a pulley system, resulting in a COP shift forward prior to load release. Electromyographic (EMG) activity of eleven postural muscles on one side of the body was integrated over a 100 ms interval corresponding to the early stage of the COP shift, and subjected to a principal component (PC) analysis across multiple repetitions of each task. Three PCs were identified and associated with a push-back M-mode, a push-forward M-mode and a mixed M-mode. (ii) Calculation of the Jacobian of the system, which relates changes in the magnitude of M-modes to COP shifts using regression techniques: Subjects performed three different tasks (releasing different loads at the back, voluntarily shifting body weight forward and backward, at different speeds) to verify if the relationship between magnitudes of M-modes and COP shifts is task or direction specific. (iii) UCM analysis: Three tasks were chosen (load release in the front, arm movement forward and backward) which were associated with an early shift in COP. A manifold was identified in the M-mode space corresponding to a certain average (across trials) shift of the COP and variance per degree of freedom within the UCM (V_UCM) and orthogonal (V_ORT) to the UCM was computed. Across subjects, V_UCM was significantly higher than V_ORT when analysis at the third step was performed using a Jacobian computed based on a set of tasks associated with a COP shift in the same direction but not in the opposite direction. This result confirms our hypothesis that the M-modes work together as a synergy to stabilize a desired shift of the COP. Forward and backward COP shifts are associated with different synergies based on the same three M-modes.An erratum to this article can be found at     

重型颅脑损伤患者鼻饲体位及时间的探讨及护理

重型颅脑损伤患者由于伤后意识障碍不能自行进食,且机体处于高分解、高代谢状态,胃肠处营养往往不能满足机体需要,因此胃肠内营养就显得尤为重要。传统的神经外科常用体位鼻饲易发生吸人性肺炎,往往不能按计划给予饮食,导致营养不良,影响预后。我们经过探索,改善了营养不良状况,减少了并发症,现介绍如下。     

Stance and sensory feedback influence on postural dynamics

This study examined the effects of ice-induced plantar desensitization and the withdrawal of visual feedback on the magnitude and time-dependent structure of postural sway variability. The magnitude of variability was quantified as the area of an ellipse enclosing 95% of the center of pressure (COP) time-series during normal and tandem stances. The same time-series were also analyzed using Approximate Entropy (ApEn) and Cross-Approximate Entropy (CrossApEn) as indices of irregularity and asynchrony between the mediolateral and anteroposterior COP motions. Variability increased during tandem stance and this increase was compounded by both visual feedback withdrawal and cutaneous desensitization. Both ApEn (mediolateral and anteroposterior COP motion) and CrossApEn increased with the withdrawal of visual feedback during the tandem stance, but decreased significantly during normal stance. The results of the study demonstrate that plantar desensitization only affected the magnitude of sway variability but did not alter its time-dependent structure. Contrasting effects on the structure of postural sway variability with visual feedback withdrawal were observed during the different stances, highlighting the role of task demands in postural dynamics.     

Muscle synergies involved in shifting the center of pressure while making a first step

We used the framework of the uncontrolled manifold (UCM) hypothesis to analyze multi-muscle synergies involved in making a step by a standing person. We hypothesized that leg and trunk muscles are organized into stable groups (muscle modes, M-modes) related to shifts of the center of pressure (COP) in the anterior-posterior and medio-lateral directions. Another hypothesis was that the magnitudes of the modes co-vary across repetitive trials to stabilize a certain magnitude of the COP shift in both directions. M-modes were defined using principal component analysis applied to indices of changes in the electromyographic (EMG) activity prior to releasing variable loads that were held by the subject using a pulley system. For the task of releasing the load behind the body three M-modes associated with a backward COP shift were defined. Four M-modes were defined for the task of releasing the load at the body side associated with a lateral COP shift. Multiple regression analysis was used to relate changes in the M-mode magnitudes to COP shifts. EMG changes prior to making a step were quantified over five 100 ms time windows before the lift-off of the stepping leg. Two components of the variance in the M-mode space computed across repetitions of a stepping task were quantified—a component that did not affect the average COP shift in a particular direction (variance within the UCM, V _UCM), and a component that affected the COP shift (variance orthogonal to the UCM, V _ORT). V _UCM was significantly higher than V _ORT for both directions of the COP shifts. This relation was observed for the M-modes in the stepping leg as well as in the support leg. The stepping leg showed a different time evolution of the ratio V _UCM/V _ORT such that the difference between the two variance components disappeared closer to the time of the lift-off. The findings corroborate both main hypotheses. The study supports a view that control of whole-body actions involves grouping the muscles, using fewer elemental variables to scale the muscle activity, and forming synergies in the space of the elemental variables that stabilize time profiles of important performance variables.     

Can Quiet Standing Posture Predict Compensatory Postural Adjustment?

OBJECTIVE

The aim of this study was to analyze whether quiet standing posture is related to compensatory postural adjustment.

INTRODUCTION

The latest data in clinical practice suggests that static posture may play a significant role in musculoskeletal function, even in dynamic activities. However, no evidence exists regarding whether static posture during quiet standing is related to postural adjustment.

METHODS

Twenty healthy participants standing on a movable surface underwent unexpected, standardized backward and forward postural perturbations while kinematic data were acquired; ankle, knee, pelvis and trunk positions were then calculated. An initial and a final video frame representing quiet standing posture and the end of the postural perturbation were selected in such a way that postural adjustments had occurred between these frames. The positions of the body segments were calculated in these initial and final frames, together with the displacement of body segments during postural adjustments between the initial and final frames. The relationship between the positions of body segments in the initial and final frames and their displacements over this time period was analyzed using multiple regressions with a significance level of p ≤ 0.05.

RESULTS

We failed to identify a relationship between the position of the body segments in the initial and final frames and the associated displacement of the body segments.

DISCUSSION

The motion pattern during compensatory postural adjustment is not related to quiet standing posture or to the final posture of compensatory postural adjustment. This fact should be considered when treating balance disturbances and musculoskeletal abnormalities.

CONCLUSION

Static posture cannot predict how body segments will behave during compensatory postural adjustment.     

Cardiovascular regulation during upright standing behavior in conscious rats

Although rats often show an upright standing behavior the cardiovascular response during the behavior has not yet been fully clarified. In this study we quantified the activity of upright standing behavior in rats using infrared beam detectors and measured cardiovascular variables during the behavior. Rats demonstrated a high level of upright standing activity as they showed the upright posture more than 500 times per day at 10 weeks of age. The average upright standing duration time was less than 10s. Arterial pressure slightly decreased while heart rate increased in response to the behavior and these responses were not affected by sino-aortic denervation. Our results indicate that other mechanisms such as the vestibulo-cardiovascular reflex may completely compensate the lack of the baroreceptor reflex to maintain cardiovascular homeostasis in response to acute positional changes in rats. Moreover rats demonstrate complex integrative mechanisms maintaining cardiovascular homeostasis against the upright standing behavior which frequently occurs in rats.