Richard Eric Rothman, M.D., Ph.D.
- Vice Chair of Research, Department of Emergency Medicine
- Professor of Emergency Medicine
https://www.hopkinsmedicine.org/profiles/results/directory/profile/0007064/richard-rothman
The microprocessor generates and shapes trains of stimulation pulses that are multiplexed and directed by the algorithm imbedded in that microcomputer to 6 output channels erectile dysfunction and diabetes ppt purchase cialis jelly 20 mg otc, which are individually controlled by the microcomputer erectile dysfunction 70 year olds order 20 mg cialis jelly with amex, in response to menu selection by the patient to avoid robot-like movements erectile dysfunction treatment in unani buy cheap cialis jelly 20mg on-line. They are to be attached by the patient himself in the morning and removed each evening or as desired at locations that the patient has been taught to remember diabetes erectile dysfunction wiki order cialis jelly 20mg mastercard. The same microchip also controls optic isolation chips to allow using a single power amplifier for all channels. The additional two stimulation channels (at the paraspinals for trunk stability) play a major role in enhancing standing time, ambulation distances, and speeds as compared with four channel systems. Higher pulse width speeds up the rate of muscle fatigue and therefore reduces the maximal ambulation distance (see Table 31. It also sends into the body more electrical charge than is needed and requires higher battery power and hence higher battery weight. The inter-pulse repetition rate (frequency) is set higher than the average pulse rate in the able-bodied individual, but is still kept as low as possible (22 to 24 pulses/sec) to reduce rate of fatigue (see Table 31. It is determined by considerations of fatigue, tetanization, and force (note that while standing or walking, the body weight dampens vibrations considerably). Higher frequencies also imply that a higher electrical charge enters the body and requires higher battery power and heavier batteries. Furthermore higher pulse rates speed up the rate of muscle fatigue to reduce duration and range of ambulation. Both pulse widths and rates, while constant, can be adjusted if necessary (see Figure 31. Therefore, a combination of a short pulse duration, low stimulation levels, and low pulse rate is essential to reduce muscle fatigue, thus extending walking distance (walking time) per walk [5]. The consequences of lower battery power needs, of lower system weight, and of the resultant effect on compactness are of course also significant for a patient-borne system and for user friendliness, especially, in a body-borne system. The menus are those for standing up, for right step, for left step, and for sitting down (see Figure 31. Pulse-amplitude shaping is dynamic and varies for each of the six stimulation channels and as per each menu, as does the distribution of output signal to each output channel [5,11]. Finally, two electrodes are placed over the right paraspinals at right and two at left, for upper trunk stability in patients with lesions at T7 or higher (to be placed approximately 1 in. These alternatives involve other branches of the sciatic nerve, which trigger the hip flexion reflex. However, when increasing the number of channels, say from six to eight, the patient must place (every morning) 16 electrodes instead of 12 and for a paraplegic patient this involves a lot of additional effort and time. Paraspinal signal envelopes correspond in shape to quadriceps channels except for peaks. Hence, human factor considerations imply to limit the system to the most important functions (channels) as far as performance is concerned. Pulse-amplitude shaping is dynamic and varies for each of the six stimulation channels and per each menu, as does the distribution of output signal to each output channel [6,27]. The time variation of the pulse amplitudes in each menu and per each channel, as in Figure 31. At the end of this period T, stimulation to the left common peroneal stops and the left quadriceps and left paraspinals/gluteus are stimulated. However, during the step period, the level of stimulation at the right quadriceps is automatically increased by the sequencing program to compensate for the fact that full body weight is borne by the right leg over that period. If a right step is selected, then the same menu is employed, with a reversal of roles of right and left. When a sit-down menu is selected, then the sequencing program first triggers an audible and a visual warning to allow the patient to abort the sit-down if he is not ready to sit and to allow for time to 31-10 Biomedical Engineering Fundamentals reach a chair and to comfortably sit down.
It has been necessary to engineer useful measurement tools and processes without complete science to serve a wide variety of purposes that have demanded attention in both clinical and nonclinical contexts erectile dysfunction treatment protocol cheap cialis jelly 20mg with amex. Whether purposeful or accidental occasional erectile dysfunction causes order cialis jelly 20 mg with amex, methods of systems engineering have been incorporated and have proven useful in dealing with the complexity of human brain structure and function erectile dysfunction protocol download pdf buy cialis jelly 20mg cheap. While scientific controversies continue to exist erectile dysfunction freedom book cialis jelly 20 mg otc, much research has contributed to the now common view of separate (both in function and location) processing subsystems that make up the whole. Various versions of a general distributed, multiprocessor model of human brain function have been popularly sketched [Gazzaniga, 1985; Minsky, 1986; Ornstein, 1986]. For example, it is widely known that the occipital lobe of the brain is responsible for visual information processing while other areas have been found to correspond to other functions. It is not possible to do justice here to the tremendous scope of work that has been put forth and therefore to the brain itself. Nonetheless, this compartmentalistic or systems approach, which stresses major functional systems that must exist based on overwhelming empirical evidence, has proven to be useful for explaining many normal and pathologic behavioral observations. This approach is essential to the development of meaningful and practical performance measurement strategies such as those described. Furthermore, much of this research has been aimed at uncovering the general operational frameworks of normal human information processing and not the measurement of performance capacities and their use, either alone or in combination with other capacity metrics, to characterize humans of various types. However, representative models and theories provide direction for, and are themselves shaped by, subsequent measurement efforts. While there are many principles and basic observations that have some relevance, the scope of material presented later is limited to topics that more specifically support the understanding of human informationprocessing performance capacity measurement. With this figure, attention is called to systems, their functions, and major interconnectivities. As can be seen from the diagram, information from the environment is provided to the information-processing subsystems through human sensor subsystems. The capacity to process information input from multiple sources at a conscious level is finite. Overload is prevented by limiting the amount of information simultaneously received; specific sensory information of high priority is controlled by what may be termed an attention processor. Information associated with a given sensor system is processed by a corresponding processor. The model further suggests that there are memory subsystems for each sensory modality in bidirectional communications with the associated processor. As information is received and processed at modality-specific levels it is combined at a higher level by integrative processors to generate situationspecific responses. These may be in the form of a musculoskeletal, cognitive, or attention-modifying events, as well as any combination of these. General measurement issues of fidelity, validity, and reliability are natural concerns in measurement of information-processing performance capacities. Special issues emerge that increase the overall complexity of the problem when attempting to measure attributes that reflect just the information-processing subsystems. Unlike a computer where one may remove a memory module, place it in a special test unit, and determine its capacity, the accessibility of the subsystems within the human brain is such that it is impossible to perfectly isolate and directly measure any of the individual components. When measuring characteristics of human information-processing subsystems, it is necessary to address measurement goals that are similar to those applied to analogous artificial system within the constraint that human sensors and motoric subsystems must also be utilized. This model for human performance encompasses all types of human subsystems and is the result of the application of a general theoretical framework for system performance to the human system and its subsystems. A central idea incorporated in this framework, universal to all types of systems, is that of performance capacity. In this framework, system performance capacities are characterized by availability of performance resources along each of the identified dimensions. These performance resources are to be distinguished from less rigorously defined general processing resources described by others [e. However, many of the important basic constructs associated with the idea of "a resource" are employed in a similar fashion in each of these contexts. Other important attributes of performance capacities are discussed in other sections of this chapter. Many aspects of information-processing performance have been investigated resulting in discoveries that have provided insight to the capacities of subsystems as well as refinement to both system structure and function definitions [Lachman et al. One of the oldest studies in which the basic concept of information-processing performance capacity was recognized addressed "speed of mental processes" [Donders, 1868]. The basic idea of capacity has been a central topic of interest in human informationprocessing research [Moray, 1967; Posner and Boies, 1971; Schneider and Shiffrin, 1977; Shiffrin and Schneider, 1977].
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It seems unlikely that transfer of memories to stable long-term neocortical storage takes decades erectile dysfunction treatment options natural cheap cialis jelly 20 mg visa. More probably impotence mayo purchase cialis jelly 20mg without a prescription, if transfer exists erectile dysfunction pills at gnc buy cheap cialis jelly 20 mg online, it occurs over a period of weeks erectile dysfunction lyrics cheap cialis jelly 20 mg on line, months or a few years at most. If so, it would be more appropriate to investigate slow consolidation by studying patients of the kind described by Kapur et al. It has not often been proposed that amnesics encode and store factual and episodic information at least as well as controls, but this view was advanced by Warrington & Weiskrantz (1970, 1974), although later rejected by them (Warrington & Weiskrantz, 1978), and is still supported by Gray & McNaughton (2000). This was interpreted as evidence that amnesics suffer from excessive interference during retrieval and have problems with suppressing incorrect competing responses. According to Gray & McNaughton, amnesics, or at least those amnesics with functional deficits of the same kind that are caused by hippocampal lesions, fail to inhibit competing incorrect responses to the same extent as normal subjects. On their view, the extent of amnesic deficits is a simple function of how much any memory task involves competition between responses rather than specific kinds of memory. In other words, amnesia arises when retrieval fails in certain situations because of a non-memory problem with active response suppression. This view is hard to investigate because very similar findings would be expected if amnesics fail to store certain kinds of information. In other words, failure to store certain information could be causing susceptibility to interference during retrieval, rather than susceptibility to interference causing poor retrieval. In general, although frontal neocortex lesions can disrupt the search and checking operations that are important for retrieval (Shimamura, 1995), there is little evidence that the main lesions implicated in amnesia disrupt these directed and effortful retrieval processes. The automatic retrieval processes in which cues directly reactivate a memory representation 182 A. Nevertheless, despite the lack of evidence, there are two circumstances in which the possible contribution to anterograde amnesia of impairments to certain kinds of retrieval processes cannot be discounted. First, if a common functional deficit underlies some aspects of both anterograde and retrograde amnesia, and it turns out that retrograde amnesia does not involve disruption of previously stored memories, then deficits in retrieval processes could still be a contributory factor in anterograde amnesia. Second, if, contrary to much evidence, priming is preserved in amnesia and retrieval is construed broadly to include processes which signal that a representation is of something old or familiar, then anterograde amnesia might be caused by a deficit in this signalling process (see Mayes & Roberts, 2002), rather than in an automatic or effortful search or monitoring process. However, Buckner & Wheeler (2001) have argued that functional neuroimaging data suggest that this familiarity signal is provided by structures in the parietal and frontal neocortex, rather than the brain regions usually associated with amnesia. The long-term aim is to identify all these functional deficits and the lesions or neural dysfunctions which underlie them, and to create realistic models of how the damage causes the functional deficits. One promising but controversial first step towards fulfilling this aim has been made by Aggleton & Brown (1999). According to their hypothesis, intra-item associations are stored in the perirhinal cortex through interactions with posterior and frontal neocortical as well as midline thalamic structures. Damage to this system should severely impair familiarity memory for experienced items. In contrast, the hippocampus stores certain kinds of association through interactions with the medial temporal cortices and other structures in the Papez circuit. Damage to this system causes impairments in recollection, but not familiarity memory. In this model, the hippocampus makes memory representations that emphasize the differences between similar patterns (pattern separation), whereas the cortices make memory representations that emphasize similarities between similar patterns. Only pattern separation leads naturally to pattern completion (recall and recollection) when partial cues are provided at retrieval. This model provides a detailed mechanism for the processes of recollection/recall and familiarity memory and makes predictions of a kind that cannot be made by neuropsychological hypotheses about the causes of amnesia. This is radically different from the proposal of Gray & McNaughton, that the hippocampus stores no episodic or semantic information even briefly but is critically involved in inhibiting incorrect, competing responses. The key to this understanding is knowing where different components of episodic and semantic information are stored and what brain regions mediate the initial and slow consolidation of such storage. Although there are quite well supported hypotheses, such as that of Aggleton & Brown (1999), the disagreement that remains will only be resolved by developing and testing the predictions of hypotheses that indicate how specific brain regions mediate memory functions and how lesions disrupt these functions. Eventually, such hypotheses must also indicate how functionally distinct regions interact. Differential cognitive effects of colloid cysts in the third ventricle that spare or compromise the fornix.
It cannot be overemphasized that these processes are complex and interrelated [Kroemer et al age related erectile dysfunction treatment proven 20 mg cialis jelly. Other factors that may affect the performance of patients are misunderstanding of the degree of effort needed in maximal testing erectile dysfunction foods to eat generic cialis jelly 20 mg without a prescription, test anxiety erectile dysfunction natural cures purchase cialis jelly 20mg with mastercard, depression erectile dysfunction over 50 discount cialis jelly 20 mg on-line, nociception, fear of pain and reinjury, as well as unconscious and conscious symptom magnification. The following sections review some methods to quantify performance and lifting capability of isolated trunk muscles during a multilink coordinated manual materials handling task. Relevant factors that 83-4 Biomedical Engineering Fundamentals influence the static and dynamic strength and endurance measures of trunk muscles will be addressed, and the clinical applications of these assessment techniques will be illustrated. Hence the functional evaluation of muscles cannot be performed without the characterization of the interfaced mechanical environment. The four fundamental types of muscle exertion or action are isometric, isokinetic, isotonic, and isoinertial. In isometric exertion, the muscle length is kept constant, and there is no movement. Although mechanical work is not achieved, physiologic work, that is, static work, is performed, and energy is consumed. When the internal force exerted by the muscle is greater than the external force offered by the resistance, then concentric, that is, shortening, muscle action occurs, whereas if the muscle is already activated and the external force exceeds the internal force of the muscle, then eccentric, that is, lengthening, muscle action occurs. When the muscle moves, either concentrically or eccentrically, dynamic work is performed. If the rate of shortening or lengthening of the muscle is constant, the exertion is called isokinetic. When the muscle acts on a constant inertial mass, the exertion is called isoinertial. Isotonic action occurs when the muscle tension is constant throughout the range of motion. These definitions are very clear when dealing with isolated muscles during physiologic investigations. However, terminology employed in the literature of strength evaluation is imprecise. The terms are intended to refer to the state of muscles, but they actually refer to the state of the mechanical interface, that is, the dynamometer. Isotonic exertion, as defined, is not as realizable physiologically because muscular tensions change as its lever arm changes despite the constancy of external loads. Special designs may vary the resistance level in order to account for changes in mechanical efficiency of the muscles. In addition, the rate of muscle length change may not remain constant even when the joint angular velocity is regulated by the dynamometer during isokinetic exertions. During isoinertial action, the net external resistance is not only a function of the mass (inertia) but also a function of the acceleration. Hence, to fully characterize the net external resistance, we need to have both the acceleration and the inertial parameters (mass and moment of inertia) of the load and body parts. Future research should better quantify the inertial effects of the dynamometers, particularly during nonisometric and nonisokinetic exertions. For any joint or joint complex, muscle performance can be quantified in terms of the basic dimensions of performance: strength, speed, endurance, steadiness, and coordination. Muscle strength is the capacity to produce torque or work by voluntary activation of the muscles, whereas muscle endurance is the ability to maintain a predetermined level of motor output - for example, torque, velocity, range of motion, work, or energy - over a period of time. Fatigue is considered to be a process under which the capability of muscles diminish. Coordination, in this context, is the temporal and spatial organizations of movement and the recruitment patterns of the muscle synergies. Despite the proliferation of various technologies for measurement, basic questions such as "What needs to be measured and how can it best be measured? However, there is a consensus on the need to measure objectively the performance capability along the following dimensions: range of motion, strength, endurance, coordination, speed, acceleration, etc. Strength is one of the most fundamental dimensions of human performance and has been the focus of many investigations.
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