Specialist home-based nursing services for children with acute and chronic illnesses.

BACKGROUND: Specialist paediatric home-based nursing services have been proposed as a cost-effective means of reducing trauma resulting from hospital admissions, while enhancing primary care and reducing length of hospital stay. OBJECTIVES: To evaluate specialist home-based nursing services for children with acute and chronic illnesses. SEARCH STRATEGY: Electronic searches were made of CENTRAL (Cochrane Central Register of Controlled Trials) 2005 (Issue 2); MEDLINE (1966 to August 2005); EMBASE (1980 to August 2005); PsycINFO (1887 to August 2005); CINAHL (1982 to August 2005); Sociological Abstracts (1963 to August 2005). Optimally sensitive search strategies for randomised controlled trials (RCTs) were combined with medical subject headings and text words specific for ambulatory paediatrics, nursing outreach and 'hospital in the home', and no language restrictions were applied. SELECTION CRITERIA: RCTs of children aged 0-18 with acute or chronic illnesses allocated to specialist home-based nursing services compared with conventional medical care. Outcomes included utilisation of health care, physical and mental health, satisfaction, adverse health outcomes and costs. DATA COLLECTION AND ANALYSIS: Meta-analysis was not appropriate because of the clinical diversity and lack of common outcomes measures MAIN RESULTS: 1655 titles yielded 5 RCTs with a total of 771 participants. Participants, interventions and outcomes were diverse. No significant differences were reported in health outcomes; two studies reported improvements in child and parental anxiety; one study reported no significant difference in readmissions; two studies reported significantly fewer bed days; increased satisfaction was reported ; home care was more costly for service providers, but less expensive for parents. AUTHORS' CONCLUSIONS: While current research does not provide definitive support for specialist home-based nursing services in reducing access to hospital services or length of stay, preliminary results show no adverse impact on physical health outcomes and a number of papers reported improved satisfaction with home-based care. Further trials are required, measuring health, satisfaction, service utilisation and long-term costs.

Sensor fusion by neural networks using spatially represented information.

A neural network model based on a lateral-inhibition-type feedback layer is analyzed with regard to its capabilities to fuse signals from two different sensors reporting the same event ("multisensory convergence"). The model consists of two processing stages. The input stage holds spatial representations of the sensor signals and transmits them to the second stage where they are fused. If the input signals differ, the model exhibits two different processing modes: with small differences it produces a weighted average of the input signals, whereas with large differences it enters a decision mode where one of the two signals is suppressed. The dynamics of the network can be described by a series of two first-order low-pass filters, whose bandwidth depends nonlinearly on the level of concordance of the input signals. The network reduces sensor noise by means of both its averaging and filtering properties. Hence noise suppression, too, depends on the level of concordance of the inputs. When the network's neurons have internal noise, sensor noise suppression is reduced but still effective as long as the input signals do not differ strongly. The possibility of extending the scheme to three and more inputs is discussed.

Vestibular perception of self-rotation in different postures: a comparison between sitting and standing subjects.

We investigated whether posture - either seated (S) or upright standing (O, orthostatic) - affects the vestibular perceptions of angular velocity (V) and displacement (D) in the horizontal plane. We also examined whether the two perceptions are equivalent, that is, whether perceived displacement can be viewed as the time integral of perceived velocity. Sinusoidal stimuli were delivered to subjects sitting on a Barany chair or standing on a turning platform. Frequencies ranged from 0.028 Hz to 0.45 Hz, peak-to-peak amplitudes from 11.3 degrees to 180 degrees, and peak velocities from 4 degrees/s to 64 degrees/s. Perceptions were measured by retrospective magnitude estimation in relation to a standard stimulus (STD) of 0.11 Hz, 45 degrees, 16 degrees/s. For D-estimates, two different moduli were assigned to the STD: Either "45 degrees" (allowing subjects to use the familiar degree scale, which can easily be related to the body scheme) or "10" (which bears no relation to an accustomed scale). For V-estimations the modulus was always "10" (there is no "natural" velocity scale). D-estimates exhibited only a marginal, non-significant dependence on posture (S larger than O); they were highly veridical (linear function of stimulus amplitude, gain close to 1) when subjects used the degree scale but had a reduced gain (approximately 0.76) with a modulus of 10. V-estimates, on the other hand, varied with posture (S significantly larger than O), particularly upon presentation of large stimuli; also, they deviated increasingly from veracity as stimulus magnitude increased (saturating function). Finally, posture had no effect upon the vestibular detection threshold. The frequency response of D-estimates, tested with stimuli of constant amplitude and varying frequency, was bimodal at low frequencies: stimuli were either not detected at all or were veridically estimated, on average (with a large scatter, though). The frequency response of V-estimates, tested with stimuli of constant peak velocity, exhibited a continuous increase with stimulation frequency. We conclude that published quantifications of vestibular self-motion perception, collected mostly with sitting subjects, are likely to be applicable also to the more natural situation of standing subjects provided they are based on displacement indications; in contrast, velocity indications appear to be modulated by posture. The different susceptibility of displacement and velocity estimates to posture and their incongruent frequency characteristics suggest that perceived displacement does not, or does not always, equal the time integral of perceived velocity. The persistence of nearly veridical displacement estimates at low frequencies suggests the intervention of cognitive processes.

Estimation of self-turning in the dark: comparison between active and passive rotation.

The present work compares passive and active rotations in darkness with the aim of characterizing the contribution of efferent and proprioceptive information to the perception of angular displacement. The perception of angular displacements was measured in 12 naive subjects (Ss), who either stood on a rotating platform (passive mode, P) or actively turned about their vertical axis by stepping around "on the spot" on a stationary platform (active mode, A). Rotations consisted of short acceleration epochs followed by constant velocity periods of 18.5, 37, and 55 degrees /s, with angular displacements ranging from 30 degrees to 810 degrees (presented in a randomized order); in the case of active turning, Ss had learned to approximately produce any of these three velocity levels on command. Ss indicated perceived displacement either verbally (verbal estimation mode, E), or by stopping their rotation when self-displacement appeared to match the magnitude specified by the experimenter (targeting, T). The resulting four conditions (PE, PT, AE, AT) were administered blockwise. In none of the four conditions was there a systematic dependence of perception on turning velocity. Therefore, the results were pooled across velocities, and the Ss' performance was summarized in the form of estimation curves showing median estimates as a function of physical displacement. There were several differences between the passive and active modes: AE- and AT-estimation curves were linear, close to veracity, and fairly similar to each other. In contrast, the PE-curve was curved rightwardly ("saturation"), with small displacements being overestimated and large ones underestimated, whereas the PT-curve was linear and indicated a pronounced overestimation of large displacements. Moreover, both the random and the systematic errors (measures of individual consistency and correctness of individual calibration, respectively) were significantly smaller in the active than in the passive modes. The observed independence of Ss' perception from turning velocity also during passive rotation suggests that the perceptual time constant was significantly longer than 16 s (a value cited as typical for vestibular perception), being possibly "enhanced" by contextual implications and by expectations of the Ss. The clear improvement of perceptual performance in the active mode testifies to the importance of the efferent and proprioceptive signals arising during active motion. On the assumption that these signals are about as "noisy" as the vestibular ones, the smaller errors during active turning could result from their combination with the vestibular signal. Alternatively, they could also be intrinsically less noisy than the vestibular signal and simply replace the latter during active motion. In the context of these alternatives (which are not exhaustive), the general problem of sensory fusion is discussed, that is, by which mechanisms are signals from different sensory sources combined to obtain a unified representation of the self's orientation.

Podokinetic after-rotation does not depend on sensory conflict.

Humans who have been stepping for 10 min or more about their vertical axis on a counterrotating platform while fixating on a stationary visual scene continue to circle in the same direction when they attempt, thereafter, to step on firm ground in darkness without turning ("podokinetic after-rotation": PKAR). In the present report, we investigate whether PKAR is due to: (1) a sensory reinterpretation triggered by the conflict between the visual signal of stationarity and the somatosensory message of feet-on-platform rotation, or (2) an adaptation of the somatosensory afferents to prolonged unilateral stimulation irrespective of visual stimulation. Subjects (Ss) circled for 10 min about their vertical axis on an either stationary or counterrotating platform while they were either in darkness, or exposed to an optokinetic stimulus, or to a "head-fixed" stationary pattern. Thereafter, Ss first stood motionless in darkness for 30 s, allowing vestibular after-effects to decay, and then tried (still without vision) to step in place on the stationary platform without turning while their body rotation was recorded by a potentiometer coupled to the head. All conditions involving podomotor activity without concomitant optokinetic stimulation evoked similar PKAR. With optokinetic stimulation, PKAR became larger, apparently because it was summed with an optokinetically induced after-rotation (oPKAR). This oPKAR could be demonstrated in isolation when Ss were passively rotated in front of the OKN-pattern instead of actively circling. PKAR could not be "dumped"; it reappeared after 30 s of straight stepping under visual control. We suggest that PKAR is caused by adaptation of the somatosensory channel and not by a sensory conflict.