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A pressure mat for preventing pressure sores
Abstract
Using a 0.4-mm thick Interlink conductive polymer pressure sensor,
the pressure distribution under the buttocks was measured. The measured
pressures under the ischial tuberosities were much higher when the
subject was seated on a table than when seated on a cushion. A pressure
mat incorporating an array of these sensors, to be placed under any bony
protuberance, is proposed. When the pressure-time profile of any sensor
exceeds safe limits, an alarm would be provided to the patient or
caregiver. It is believed that this pressure mat could reduce the
incidence of pressure sores in the spinal-cord injured, in the elderly,
and in the operating room
... IP involves mapping using sensors to quantify the pressure between two contacting objects, such as a person and their support surface. It is commonly used by clinician and by researchers investigating the surface, risk factors for ulceration and ulcer prevention protocol [9]. Frederick Shelton [10] compared different surfaces for elderly people (65-70 years) mannequins with Tekscan 5315 system in his test. ...
... The prominent pressure points causing PUs in Supine Position [9] Wheelchair bound patients constantly need to adjust positions in order to relieve pressure to decrease their chances of developing a pressure sore. The patient needs to adjust themselves at least every two hours in order to relieve the external pressure that is being applied to the capillaries. ...
... IP involves mapping using sensors to quantify the pressure between two contacting objects, such as a person and their support surface. It is commonly used by clinician and by researchers investigating the surface, risk factors for ulceration and ulcer prevention protocol [9]. Frederick Shelton [10] compared different surfaces for elderly people (65-70 years) mannequins with Tekscan 5315 system in his test. ...
... The prominent pressure points causing PUs in Supine Position [9] Wheelchair bound patients constantly need to adjust positions in order to relieve pressure to decrease their chances of developing a pressure sore. The patient needs to adjust themselves at least every two hours in order to relieve the external pressure that is being applied to the capillaries. ...
... IP involves mapping using sensors to quantify the pressure between two contacting objects, such as a person and their support surface. It is commonly used by clinician and by researchers investigating the surface, risk factors for ulceration and ulcer prevention protocol [12]. Frederick Shelton [13] compared different surfaces for elderly people (65-70 years) mannequins with Tekscan 5315 system in his test. ...
IDENTIFYING LOCATION OF MAXIMUM INTERFACE PRESSURE IN BEDRIDDEN PATIENT –A COMPARATIVE STUDY, www.ijates.com Volume No.03, Special Issue No. 02, February 2015 ISSN (online): 2348 – 7550 ,P a g e 113-121
... Interface pressure involves mapping using sensors to quantify the pressure between two contacting objects, such as a person and their support surface. It is commonly used by clinicians and by researchers investigating the surface, risk factors for ulceration and ulcer prevention protocols [5], [6]. Fredrick Shelton [7] com-pared different surfaces for elderly people (65-70 years) mannequins with Tekson 5315 system in his test. ...
An input interface utilizing a conductive polymer force sensor has been designed, developed and tested for use by handicapped children. The ability to easily fabricate a thin (c 1 mm) sensor with a relatively large surface area, as well as the relatively simple circuitry necessary for operation in comparison to other types of sensors makes the device attractive. As the threshold force level of the sensor to activate a device can be adjusted easily by the electrical circuitry, a single sensor can be used by various children with limited motor ability. The main application for the prototype has been single and multiple channel switching mainly to operate a variety of toys, tape recorders, and other such devices. The adjustability and flexibility of the device have aided special education professionals in working with handicapped children in various activities.
The sole of the foot acts as the interface between the ground and the body and is subjected to changing patterns of stress. These stresses will be accompanied by temporary or permanent strains within the tissues and may therefore be linked with those foot conditions which involve some degree of structural failure. One method of investigating the stresses is to measure the pressure distribution at the sole; an apparently simple task that continues to test scientific ingenuity and technological progress. Recent attempts to quantify shear stresses show that this extra goal may be even more challenging.
Previous reviews describe the technology but not the relationship between the sensor characteristics and the associated data. The apparent lack of understanding of this relationship is reflected in some published reports and has meant that clinical findings can be misinterpreted. This report reviews those sensor characteristics that have been recorded in the literature. It also shows how the sensor design influences the data and explains why a realistic appreciation of clinical findings requires a preliminary understanding of the chosen sensor.
A silicon sensor is developed and its ability to measure both compressive and shear forces at the skin-object interface is characterized. The sensor is designed based on the piezoresistive effect and fabricated using integrated circuit and microelectromechanical systems technologies. The sensor utilizes a mesa structure that leads to asymmetric diaphragm deformations in response to nonnormal loading. Four independent ion-implanted piezoresistors are used to detect the stresses induced in diaphragm and resolve both the compressive- and shear-force components. The sensor is calibrated on human subjects over a range of applied force (5- to 40-N shear force at increments of 1.25 N; 0- to 30-N compressive force). Force measurement via a tracking experiment is evaluated at four shear (9, 18, 25, and 35 N) and three compressive (7, 15, and 26 N) force levels. The sensor has good repeatability (SD approximately 1.7 N) with an average error of 12.1%.
The clinically significant causes of decubitus ulceration are briefly surveyed. This is followed by discussion of preventive regimes and the treatment of established sores. Good nursing as the basic factor in all preventive treatment is emphasised.
Since this paper is a contribution to a symposium dealing with many aspects of tissue trauma, we propose to limit our discussion to experience only at Rancho Los Amigos Hospital in Downey, California. We do not wish to imply that our methods are superior to all others but we hope that some different and useful ideas may obtain from our limited experience.
The Tissue Trauma Group of the Rehabilitation Engineering Center has been actively involved in research, development and patient service for both the sitting and the recumbent (or prostrate) patient. The approaches to these two types of problem are fundamentally different for the following reasons:
(i)
The projected area of support of a prostrate human being, when divided into his body weight, yields an average pressure of around so mm Hg. This is below the 30-35 mm Hg usually accepted as necessary to cause ischaemia.
(ii)
The projected area of support, including the feet (but not the back) of a sitting person when divided into his body weight, yields an average pressure of about 50 mm Hg. This is above the 30-35 mm Hg ‘ischaemic pressure’.
The logic of reason (i) has led us to develop devices to attempt to distribute the support pressure of the recumbent patient as uniformly as possible, so that such patients may lie in any position in definitely (usually through the night) without being turned. This approach has resulted in the Rancho Flotation Bed (mud bed) and the Poly-Flotation Mattress to be described later.
The problems of the seated patient suggested in reason (ii) have led to an approach that involves the development of optimum seat cushions, coupled with clinical service which relies on special pressure measurement techniques and procedures for custom modification of seat cushions and sitting positions. These will be discussed in detail.
Research and development have focused on new instrumentation to indicate the potential for tissue damage, studies of various support material characteristics and the development of support systems, both passive (viscoelastic seat cushions with or without cutouts, and flotation systems) and active (devices requiring external power) systems.
The performance of the Interlink force sensor for measuring force under insensate feet of diabetics has been tested. Embedded in a rubber insole, seven of these sensors measure the force under high-pressure points on the sole of the foot during walking. In sensor operation, force compresses a conductive polymer film against a printed conductive pattern and hence decreases the resistance of the sensor. Using the described sensor and electronics, an umbilical system has been constructed to monitor the pressure under the center of the heel, the five metatarsal heads, and the big toe of each foot. The response of the sensor under the center of the heel for two consecutive steps is shown.
The authors have characterized the performance of the commercially available Interlink pressure sensor. The sensor costs less than $1. It is 0.25-mm thick, is light and flexible, and can be customized for a wider range of applications. The resistance-versus-pressure characteristic of the sensor is logarithmic. The operating range is from 0 to 2 MPa. The hysteresis is 8% and the nonrepeatability is less than 7% of full scale. The temperature drift is -0.5%/ degrees C of full scale. Using the Interlink sensors and electronics, the authors developed a portable data acquisition system to monitor the pressure under the bony prominences of the feet during normal gait. The advantages and drawbacks of the sensor are indicated.< >
A pressure sore is an ulceration of the skin and/or deeper tissues due to unrelieved pressure, shear force(s), and/or frictional force(s). This paper reviews the literature from 1977-1987 on the etiology and pathophysiology of pressure sores, factors contributing to their formation, diagnostic and pressure-measuring devices, and cushions and devices designed to prevent sores. The authors hope this review will show that many current assumptions may be invalid and should be re-examined.
Tactile sensors for robotics and medicine
- J G Webster