Perceiving Synchrony: Determining Thermal-tactile Simultaneity Windows.

In cutaneous displays in which both tactile and thermal signals are presented, it is important to understand the temporal requirements associated with presenting these signals so that they are perceptually synchronous. Such synchrony is important to provide realistic touch experiences in applications involving object recognition and social touch interactions. In the present experiment the temporal window within which tactile and warm thermal stimuli are perceived to occur at the same time was determined. A Simultaneity Judgment Task was used in which pairs of tactile and thermal stimuli were presented on the hand at varying stimulus onset asynchronies, and participants determined whether the stimuli were simultaneous or not. The results indicated that the average simultaneity window width was 1041 ms. The average point of subjective simultaneity (PSS) was -569 ms, indicating that participants perceived simultaneity best when the warm thermal stimulus preceded the tactile stimulus by 569 ms. These findings indicate that thermal and tactile stimuli do not need to be displayed simultaneously for the two stimuli to be perceived as being synchronous and therefore the timing of such stimuli can be adjusted to maximize the likelihood that they will both be perceived.

Effect of a 4-Week Telerehabilitation Program for People with Post-COVID Syndrome on Physical Function and Symptoms: Protocol for a Randomized Controlled Trial.

OBJECTIVE: COVID-19 has led to significant morbidity and mortality globally. Post-COVID sequelae can persist beyond the acute and subacute phases of infection, often termed Post-COVID Syndrome (PCS). There is limited evidence on the appropriate rehabilitation for people with PCS. The aim of this study is to evaluate the effect on exercise capacity, symptoms, cognition, anxiety, depression, health-related quality of life (HRQoL), and fatigue, of a 4-week, twice-weekly supervised pulmonary telerehabilitation program compared to usual medical care for people with PCS with persistent respiratory symptoms. METHODS: The study will be a multi-site randomized controlled trial (RCT) with assessor blinding. Participants with confirmed previous COVID-19 infection and persistent respiratory symptoms who attend a post-COVID respiratory clinic will be randomized 1:1 to either an intervention group (IG) of 4 weeks, twice-weekly pulmonary telerehabilitation or a control group (CG) of usual medical care. Participants in the CG will be invited to cross-over into the IG after the week 4 assessment. Primary outcome: exercise capacity measured by the 1-minute sit-to-stand test. Secondary outcomes: 5 repetition sit-to-stand test; Montreal Cognitive Assessment; COVID-19 Yorkshire Rehabilitation Scale; COPD Assessment Test; 36-Item Short-Form Health Survey; Hospital Anxiety and Depression Scale; Fatigue Severity Scale; and the Kessler Psychological Distress Scale. Outcomes will be collected at baseline, after 4-weeks intervention or control period, after intervention in the cross-over group, and at 12-month follow-up. IMPACT STATEMENT: Research into effective rehabilitation programs is crucial given the substantial morbidity associated with PCS and the lack of long-term data for COVID-19 recovery. A short duration pulmonary telerehabilitation program, if effective compared to usual care, could inform practice guidelines and direct future clinical trials for the benefit of individuals with persistent respiratory symptoms post-COVID.

COVID-19 and collective trauma: Implementing a trauma-informed model of care for post-COVID patients.

AIM: To describe the implementation of a trauma-informed model of care in the Post COVID Respiratory Clinic of a large tertiary referral centre in NSW. DESIGN: Discussion paper. DATA SOURCES: Evidence gathered from a literature search (2008-2022) was used to develop a framework for management of patients presenting to this Post COVID Respiratory Clinic. This paper outlines the personal reflections of the clinic staff as they developed and implemented this framework. Ethical approval was obtained to report the data collected from patient reviews. DISCUSSION: The literature highlights the high prevalence of trauma in patients following COVID-19 infection, as well as the larger population both during and after the pandemic. This experience of trauma was observed in patients seen within the clinic, indicating a need for specialized care. In response, a trauma-informed model of care was implemented. CONCLUSION: Reconceptualizing COVID-19 as a 'collective trauma' can help healthcare workers understand the needs of post-COVID patients and enable them to respond empathetically. A trauma-informed model is complementary to this cohort as it specifically addresses vulnerable populations, many of whom have been further marginalized by the pandemic. IMPLICATIONS FOR NURSING AND PATIENT CARE: Frontline healthcare workers, particularly nurses, are well positioned to implement trauma-informed care due to their high-level of patient contact. Adequate allocation of resources and investment in staff is essential to ensure such care can be provided. IMPACT: The COVID-19 pandemic has led to adverse physical and mental health outcomes for many. Trauma-informed care is a way to promote reengagement with the healthcare system in this group. Post COVID patients globally may benefit from this approach, as it aims to build trust and independence. PATIENT OR PUBLIC CONTRIBUTION: Feedback was sought from a patient representative to ensure this paper adequately reflected the experience of the post-COVID patient.

Haptic Communication of Language.

In this review, the development of communication systems and devices that convey language tactually is examined, first from an historical perspective focusing on the communities who use the tactile modality to substitute for impairments in vision and/or hearing. Then, the more recent developments in wearable tactile communication systems for conveying text and speech to those without sensory impairments are reviewed. The performance of tactile display technology developed for these user communities is discussed in the context of the proficiency achieved by skilled users of natural methods of tactile communication. In tracing the history of tactile devices used to convey language, it is evident that technological advances in other domains, such as screen readers and speech synthesizers for the visually impaired and cochlear implants for those with hearing loss, have had a profound impact on the requirements for effective tactile language systems. For some communities, such as the Deafblind, it is essential that the tactile communication platform is bi-directional so that the user can both send and receive language. Devices developed to address such needs have yet to achieve commercial success. Recent research on wearable tactile displays has highlighted the importance of extensive training for learning and retaining languages presented tactually.

Acute pleiotropic effects of dapagliflozin in type 2 diabetic patients with heart failure with reduced ejection fraction: a crossover trial.

AIMS: This study aimed to explore the rapid effects of dapagliflozin in heart failure with reduced ejection fraction (HFrEF). METHODS AND RESULTS: We studied the functional, echocardiographic, electrophysiological, lung ultrasound, ambulatory blood pressure (BP), microvascular and macrovascular function, and biochemical effects of 2 week treatment with dapagliflozin in 19 type 2 diabetic HFrEF patients in a double-blind, crossover, placebo-controlled trial. Dapagliflozin had no significant effect on clinical, functional, or quality of life parameters. Dapagliflozin reduced systolic BP [114 (105, 131) vs. 106 (98, 113) mmHg, P < 0.01] and diastolic BP [71 (61, 78) vs. 62 (55, 70) mmHg, P < 0.01]. There was no effect on cardiac chamber size, ventricular systolic function, lung ultrasound, or arterial wave reflection. Dapagliflozin increased creatinine [117 (92, 129) vs. 122 (107, 135) µmol/L, P < 0.05] and haemoglobin [135 (118, 138) vs. 136 (123, 144) g/L, P < 0.05]. There was a reduction in ventricular ectopy [1.4 (0.1, 2.9) vs. 0.2 (0.1, 1.4) %, P < 0.05] and an increase in standard deviation of normal heart beat intervals [70 (58, 90) vs. 74 (62, 103), P < 0.05]. Unexpectedly, dapagliflozin increased high-sensitivity troponin T [25 (19, 37) vs. 28 (20, 42) ng/L, P < 0.01] and reduced reactive hyperaemia index [1.29 (1.21, 1.56) vs. 1.40 (1.23, 1.84), P < 0.05]. CONCLUSIONS: After 2 weeks, while multiple parameters supported BP reduction and haemoconcentration with dapagliflozin, reduction in cardiac filling pressure, lung water, and functional improvement was not shown. Reduced ventricular ectopic burden suggests an early antiarrhythmic benefit. The small increase in troponin T and the reduction in the reactive hyperaemia index warrant further mechanistic exploration in this treatment of proven mortality benefit in HFrEF.

Presenting Surface Features Using a Haptic Ring: A Psychophysical Study on Relocating Vibrotactile Feedback.

In the context of wearable technologies, it is often important for the fingers to be unconstrained so that they can be used to explore the environment. In this paper, we explored the feasibility of presenting vibrotactile cues that represented different textures to one of three locations on the hand and forearm using a wearable device. The first experiment indicated that vibrotactile signals of varying frequency rendered by the tactile display could be encoded by participants in terms of changes along a roughness-smoothness dimension. The differential thresholds measured for vibrotactile frequency were significantly higher on the wrist as compared to the fingerpad and the distal phalanx of the index finger. In two subsequent experiments vibrotactile signals were presented by a tactile ring worn on the distal phalanx and participants evaluated real textures explored by the fingerpad and virtual textures rendered by the ring. It was found that participants could compare and rank in terms of roughness two spatially distributed inputs with reasonable accuracy. In the context of the haptic ring being developed, these findings indicated that it is feasible to display information experienced at the fingertip on a more proximal location on the hand, thus freeing the fingers for other tasks.

Wearable Tactile Display Based on Thermal Expansion of Nichrome Wire.

A wearable tactile display needs to be compact and lightweight, and ideally should be able to present vibration, force, and temperature information to the hand. In many contexts spatially distributed tactile information is needed such as when identifying the shape of objects. In this paper, a multi-element tactile display is described based on the thermal expansion and contraction of nichrome wire. The device comprises elastic rods that are pulled by nichrome wires (30 µm in diameter). When an electrical current is applied to the wire, displacement of the elastic rod occurs with thermal elongation of the wire. The wire cools quickly and vibration results. The nichrome wire that is the basis of this display overcomes many of the material restrictions associated with shape memory alloys that have often been used for thermally driven tactile displays. Experiments that characterized the performance of the tactile display indicated that perceptible vibrations up to 320 Hz can be presented. Psychophysical studies revealed that both position and movement cues can be displayed effectively with the device. A miniaturized version of this display for wearable applications has been built and undergone preliminary evaluation.

Shape Localization and Recognition Using a Magnetorheological-Fluid Haptic Display.

Smart materials such as magnetorheological fluids (MRF) offer an interesting technology for use in haptic displays as changes in the magnetic field are rapid, reversible, and controllable. These interfaces have been evaluated in a number of medical and surgical simulators where they can provide cues regarding the viscoelastic properties of tissues. The objective of the present set of experiments was first to determine whether a shape embedded in the MRF could be precisely localized and second whether 10 shapes rendered in a MRF haptic display could be accurately identified. It was also of interest to determine how the information transfer associated with this type of haptic display compares to that achieved using other haptic channels of communication. The overall performance of participants at identifying the shapes rendered in the MRF was good with a mean score of 73 percent correct and an Information Transfer (IT) of 2.2 bits. Participants could also localize a rigid object in the display accurately. These findings indicate that this technology has potential for use in training manual palpation skills and in exploring haptic shape perception in dynamic environments.

Multidirectional In Vivo Characterization of Skin Using Wiener Nonlinear Stochastic System Identification Techniques.

A triaxial force-sensitive microrobot was developed to dynamically perturb skin in multiple deformation modes, in vivo. Wiener static nonlinear identification was used to extract the linear dynamics and static nonlinearity of the force-displacement behavior of skin. Stochastic input forces were applied to the volar forearm and thenar eminence of the hand, producing probe tip perturbations in indentation and tangential extension. Wiener static nonlinear approaches reproduced the resulting displacements with variances accounted for (VAF) ranging 94-97%, indicating a good fit to the data. These approaches provided VAF improvements of 0.1-3.4% over linear models. Thenar eminence stiffness measures were approximately twice those measured on the forearm. Damping was shown to be significantly higher on the palm, whereas the perturbed mass typically was lower. Coefficients of variation (CVs) for nonlinear parameters were assessed within and across individuals. Individual CVs ranged from 2% to 11% for indentation and from 2% to 19% for extension. Stochastic perturbations with incrementally increasing mean amplitudes were applied to the same test areas. Differences between full-scale and incremental reduced-scale perturbations were investigated. Different incremental preloading schemes were investigated. However, no significant difference in parameters was found between different incremental preloading schemes. Incremental schemes provided depth-dependent estimates of stiffness and damping, ranging from 300 N/m and 2 Ns/m, respectively, at the surface to 5 kN/m and 50 Ns/m at greater depths. The device and techniques used in this research have potential applications in areas, such as evaluating skincare products, assessing skin hydration, or analyzing wound healing.

Needle-free delivery of macromolecules through the skin using controllable jet injectors.

INTRODUCTION: Transdermal delivery of drugs has a number of advantages in comparison to other routes of administration. The mechanical properties of skin, however, impose a barrier to administration and so most compounds are administered using hypodermic needles and syringes. In order to overcome some of the issues associated with the use of needles, a variety of non-needle devices based on jet injection technology has been developed. AREAS COVERED: Jet injection has been used primarily for vaccine administration but has also been used to deliver macromolecules such as hormones, monoclonal antibodies and nucleic acids. A critical component in the more recent success of jet injection technology has been the active control of pressure applied to the drug during the time course of injection. EXPERT OPINION: Jet injection systems that are electronically controllable and reversible offer significant advantages over conventional injection systems. These devices can consistently create the high pressures and jet speeds necessary to penetrate tissue and then transition smoothly to a lower jet speed for delivery of the remainder of the desired dose. It seems likely that in the future this work will result in smart drug delivery systems incorporated into personal medical devices and medical robots for in-home disease management and healthcare.

Displaying shape haptically using MRF-based device.

Smart materials such as magnetorheological fluids (MRF) offer an interesting medium to present viscoelastic cues in haptic displays as changes in the magnetic field are rapid, reversible and controllable. These interfaces have been evaluated in a number of medical and surgical simulators where they can provide cues regarding the viscoelastic properties of tissues. The present experiment determined whether eight different shapes could be identified reliably with a MRF haptic display and compared the information transfer (IT) associated with this type of display with that achieved by other forms of haptic communication. The overall performance of participants at identifying the shapes was good with a mean score of 70% correct and an IT of 2.13 bits. This type of display shows promise as a training tool for simulating tissue properties.

Evaluating vibrotactile dimensions for the design of tactons.

Vibrotactile stimuli are defined in terms of their amplitude, frequency, waveform and temporal profile all of which have been varied to create tactons. A number of approaches have been adopted to design tactons including multidimensional scaling, iterative empirical methods and using perceptual processing models. The objective of the present set of experiments was to create sets of tactons based on the properties of the dimensions of vibrotactile stimuli. An absolute identification paradigm was used in which each of nine tactons was presented eight times using a tactor mounted on either the index finger or forearm. It was found that tactons created by varying the frequency, amplitude and temporal profile of the vibrotactile stimuli were correctly identified on 73-83 percent of the trials, with a mean information transfer of 2.41 bits. The latter metric indicates that for these sets of nine tactons between five and six could be reliably identified. The vibrotactile stimuli delivered in the experiments were identified as consistently on the forearm as the hand and the IT values were similar at the two locations. This suggests that sites other than the hand can be used effectively in tactile communication systems and that it is channel capacity that ultimately determines performance on this type of task.

Tactile sensory system: encoding from the periphery to the cortex.

Specialized mechanoreceptors in the skin respond to mechanical deformation and provide the primary input to the tactile sensory system. Although the morphology of these receptors has been documented, there is still considerable uncertainty as to the relation between cutaneous receptor morphology and the associated physiological responses to stimulation. Labelled-line models of somatosensory processes in which specific mechanoreceptors are associated with particular sensory qualities fail to account for the evidence showing that all types of tactile afferent units respond to a varying extent to most types of natural stimuli. Neurophysiological and psychophysical experiments have provided the framework for determining the relation between peripheral afferent or cortical activity and tactile perception. Neural codes derived from these afferent signals are evaluated in terms of their capacity to predict human perceptual performance. One particular challenge in developing models of the tactile sensory system is the dual use of sensory signals from the skin. In addition to their perceptual function they serve as inputs to the sensorimotor control system involved in manipulation. Perceptions generated through active touch differ from those resulting from passive stimulation of the skin because they are the product of self-generated exploratory processes. Recent research in this area has highlighted the importance of shear forces in these exploratory movements and has shown that fingertip skin is particularly sensitive to shear generated during both object manipulation and tactile exploration.

Application of psychophysical techniques to haptic research.

Various psychophysical methods have been used to study human haptic perception, although the selection of a particular method is often based on convention, rather than an analysis of which technique is optimal for the question being addressed. In this review, classical psychophysical techniques used to measure sensory thresholds are described as well as more modern methods such as adaptive procedures and those associated with signal detection theory. Details are provided as to how these techniques should be implemented to measure absolute and difference thresholds and factors that influence subjects' responses are noted. In addition to the methods used to measure sensory thresholds, the techniques available for measuring the perception of suprathreshold stimuli are presented. These scaling methods are reviewed in the context of the various stimulus and response biases that influence how subjects respond to stimuli. The importance of understanding the factors that influence perceptual processing is highlighted throughout the review with reference to experimental studies of haptic perception.

Mechanical and psychophysical studies of surface wave propagation during vibrotactile stimulation.

Tactile displays are often used to present spatial cues about the environment, although the optimal configuration of a display used for spatial cuing is not known. The objective of the present set of experiments was to characterize the properties of surface waves induced by vibrotactile stimulation and to determine if the propagation of surface waves was a factor influencing the ability to localize a point of stimulation in a tactile display. Three sites on the body were tested: the palm of the hand, the forearm, and the thigh. An accelerometer array was fabricated and used to measure the surface waves. The results indicated that there were significant differences between glabrous and hairy skin in terms of the frequency and amplitude of oscillation of the motor. Analyses of the motion of the surface waves across the skin indicated that they were markedly attenuated at 8 mm from the motor, but even at 24 mm the amplitude was still above perceptual threshold. The localization experiment indicated that subjects were much better at identifying the site of stimulation on the palm as compared to the forearm and thigh, and that the latter two sites were not significantly different.

Capturing skin properties from dynamic mechanical analyses.

BACKGROUND/PURPOSE: Existing skin mechanical testing devices focus on measuring skin elasticity and are not tailored to assess the dynamic behavior of skin. Additionally, the mathematical techniques used in existing devices are often not optimal. METHODS: A new dynamic mechanical device that measures the linear dynamics of skin was developed and tested. The mechanical properties of skin were evaluated in experiments in which stiffness and damping parameters were measured (i) at different locations on the arm and hand, (ii) when stratum corneum hydration was varied by controlled changes in environmental humidity, and (iii) following the application of film-forming polymers. Parallel measurements were made with the Cutometer so that the two devices could be compared. RESULTS: The findings revealed that reliable and valid measurements of skin mechanical properties can be obtained from the device. The stiffness of the skin was shown to vary significantly as a function of skin site, changes in stratum corneum hydration and following application of the polymer films. Changes in the damping parameter were less consistently associated with varying the condition of the skin. CONCLUSION: The high reliability and speed of measurement make this device and analytic procedure an attractive option for testing skin mechanics.

Tactile communication systems optimizing the display of information.

Tactile communication systems based on vibrotactile signals have been developed as sensory substitution devices for those with visual, auditory, or vestibular impairments and to assist users in spatial orientation and navigation in unfamiliar environments. One of the main challenges in using tactile displays to compensate for sensory loss in other modalities or to overcome the limitations of visual and auditory information overload is in determining what type of information can be presented tactually and which parameters of stimulation can be used to convey these messages effectively. Psychophysical studies of vibrotactile perception provide a framework that assists in determining which stimulus dimensions and ranges of values can be used to create tactile patterns, known as tactons. A number of experiments have been conducted in which the ability of participants to identify tactons presented at different sites on the body has been measured. The results from this research indicate that tactons created by varying the spatial location, number, and temporal sequence of activation of motors in a tactile display can be accurately identified. They further demonstrate the potential of using two-dimensional tactile displays to present information, and the feasibility of creating tactile communication systems that are easily learned.

Thermal cues and the perception of force.

Two experiments were conducted to examine the effect of temperature on force perception. The objective of the first experiment was to quantify the change in skin temperature of the finger as a function of contact force, in order to characterize how much temperature changes under normal contact conditions. The decrease in temperature ranged from 2.3 to 4.2 degrees C as the force increased from 0.1 to 6 N, averaging 3.2 degrees C across the nine force levels studied. The changes in temperature as a function of force were well above threshold, which suggests that thermal cues could be used to discriminate between contact forces if other sources of sensory information were absent. The second experiment examined whether the perceived magnitude of forces (1-8 N) generated by the index finger changed as a function of the temperature of the contact surface against which the force was produced. A contralateral force-matching procedure was used to evaluate force perception. The results indicated that the perceived magnitude of finger forces did not change as a function of the temperature of the reference contact surface which varied from 22 to 38 degrees C. These results provide further support for the centrally generated theory of force perception and indicate that the thermal intensification of tactually perceived weight does not occur when forces are actively generated.

Walking speed at self-selected exercise pace is lower but energy cost higher in older versus younger women.

BACKGROUND: Walking is usually undertaken at a speed that coincides with the lowest metabolic cost. Aging however, alters the speed-cost relationship, as preferred walking speeds decrease and energy costs increase. It is unclear to what extent this relationship is affected when older women undertake walking as an exercise modality. The aim of this study was to compare the energetic cost of walking at a self-selected exercise pace for a 30 minute period in older and younger women. METHODS: The energetic cost of walking was assessed using the energy equivalent of oxygen consumption measured in 18 young (age 25 to 49 years) and 20 older (age 50 to 79 years) women who were asked to walk at their 'normal' exercise pace on a motorized treadmill for 30 minutes duration. RESULTS: The mass-specific net cost of walking (Cw) was 15% higher and self-selected walking speed was 23% lower in the older women than in the younger group. When speed was held constant, the Cw was 0.30 (J.kg-1.m-1) higher in the older women. CONCLUSIONS: Preferred exercise pace incurs a higher metabolic cost in older women and needs be taken into consideration when recommending walking as an exercise modality.