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The impact of bioengineering on tissue viability research
EDITORIAL
The impact of bioengineering on tissue viability research uring a brief sunny period this summer, my mind went back to heady days in 1975 when there was a conference entitled Bed Sore Biomechanics held at the Bioengineering Centre at Strathclyde University. It reflected the long-term interest of the host group, headed by Professors Robert Kenedi and Joe Barbenel (a former president of the Tissue Viability Society) on the biomechanics of soft tissues in health and damage, in conjunction with surgical interest from such luminaries as Professors John Scales and Tom Gibson. The volume of the proceedings! includes an impressive list of contributions from a variety of scientific and medical disciplines. However, it is worth examining the impact of bioengineering on the subject in the subsequent years. First, it should be recorded that there has been a consistent core of about 10 bioengineering members of the Tissue Viability Society since its inception. Although this may appear small in number compared to the Society's overall membership, these bioengineers have always been active on both the editorial board and at Tissue Viability Society meetings. Perhaps the most recognised bioengineering activity in pressure ulcer research is in the development of a range of pressure monitoring systems to supersede the previous gold standard, the Talley-Scimedics single cell system (described by Reswick and Rogers in 19762). I was involved in the design of one such development in Oxford (the Oxford Mk IIII, later the Talley Pressure Monitoring system). Nowadays this system, using 96 sensors, has been largely consigned to history, being replaced by systems with a numerous array of sensors and elegant software to display pressure profiles produced by companies including Tekscan and Novel. Such systems are clearly useful in both research and clinical settings, but it is well recognised that pressure measurements alone are not able to alert the clinician to areas of tissue which are particularly vulnerable to ulcer initiation. Most bioengineering activities, based in either university or hospital settings, require funding from either Government agencies, such as the Engineering and Physical Sciences Research Council or the Department of Health (DoH); medical charities, including Action Research; or appropriate companies in the health-care industry. The latter have been forthcoming although such studies either involve assessing the performance of one product (often new) against its competitors or involve comparing a range of support products. Such research is valuable, but will not
D
© Tissue Viability Society 126
provide any insight into many fundamental aspects of the clinical problem, such as aetiology or identification of susceptible subjects. I am reminded of a time in 1993 when the DoH hastily arranged a meeting on pressure ulcers at their headquarters, after an enquiry from one of the Houses about what the Government's policy was about alleviating the clinical problem. A number of the most informed were invited to speak but as the day progressed it became increasingly apparent that this was a white-washing exercise - reinforced by phrases from session chairmen indicating that 'the research was fascinating, but was unlikely to receive future funding from the DoH'. The result was a DoH document3 about current practices, based in part on a financial assessment by Touche Ross. One of the findings that 'prevention was more expensive than treatment', a conclusion based on the premise that all hospital inpatients required a prevention strategy - a message that could have been directed by a political agenda. However, to obtain adequate funding for a 3-year project, proposed research needs to be both scientifically sound with a degree of innovation and be of relevance to areas of topical interest. This is the current situation when agencies are increasingly inclined to announce funding calls involving prescribed research areas. Thus proposals involving nanotechnology, tissue engineering, postgenomics and metabolomics are commonly highlighted. Where does fundamental research associated with a practical clinical problems, such as pressure ulcers, fit into this strategic rubric? Does this mean that we should give up any of our hope of pursuing fundamental research to develop successful preventative strategies for pressure ulcers? The answer must surely be no. An ·increasing trend in biomechanical research is to utilise the potential of fast computing techniques associated with finite element analysis, for example, to predict stresses and strains within structures. This would seem ideal to apply to internal stresses with soft tissues subjected to prolonged loading near bony prominences. Nonetheless attempts to produce realistic analyses are stymied by the lack of suitable material properties characterising the various layers which constitute the soft tissues covering bony prominences. For example, although several studies have examined uniaxial and biaxial properties of skin parallel to its surface, there are few reported studies examining the compressive properties of the soft tissue composite. Such studies have been hampered by the lack of
JOURNAL OF TISSUE VIABILITY VOL 12 NO.4 OCTOBER 2002
.. .
Smith~Nephew
.
.
.
EDITORIAL
appropriate non-invasive techniques, which can characterise material properties of tissue under load. For example, ultrasound has offered much potential for many years but has, as yet, not proved reliable, although more sophisticated systems involving elastography in association with ultrasound imaging might prove successful in the future. Other imaging technologies involving infrared spectroscopy, magnetic resonance imaging and magnetic resonance spectroscopy may also provide valuable data under loading conditions for both healthy tissues and where tissue status is compromised. Further positive spin may be gleaned from the Dutch experience. In 1997, an audit of cost to the health service in the Netherlands indicated that pressure ulcer treatment was the fourth most costly procedure. Although well behind that of cancer, AIDS and cardiovascular disease, this placing has made a tremendous impact on funding for pressure ulcers. In particular, research is flourishing as evidenced by the large number of Dutch attendees at annual meetings of the European Pressure Ulcer Advisory Panel, supported by active research centres in Amsterdam, Maastricht and Eindhoven. Indeed in line with a panEuropean outlook, I have been associated with the Department of Biomedical Engineering in the Technical University of Eindhoven for the last 2 years. This part-time position enables me to investigate pressure ulcers at different hierarchical levels from cell damage4 to pathogenesis of the clinical condition. It has also enabled me to examine loaded tissue changes using advanced magnetic resonance imaging techniques on a system permanently available for research - such systems would be of great value in the UK. Conventional wisdom on the pathogenesis of pressure ulcers has focused on the effects of pressure-induced ischaemia of skin tissues5,6. Although important there are other major considerations, as outlined in a recent viewpoint article 7, involving the lymphatic system, interstitial transport, underlying tissues (particularly the muscle) and ischaemia-reperfusion injury. The latter mechanism has some major implications for the way patients with susceptibility to pressure ulcer
128
development are treated. Pressure relief may have to be re-examined, but I do not intend to alienate all manufacturers of alternating pressure air mattresses. I hope that many of the above issues will be raised at the conference 'Innovations in Pressure Ulcer Biomechanics and Pathophysiology'. It is being organised by the Medical Engineering group of the Institute of Mechanical Engineers, and held at their headquarters on November 25 2002. Its objective is to emphasise the importance of developing a sound scientific approach for understanding the aetiology of pressure ulcers, outlining promising approaches for their prevention. Granting agencies beware.
Dan Bader Professor of Medical Engineering Associate Director of the Interdisciplinary Research Centre in Biomedical Materials Department of Engineering Queen Mary University of London London El 4NS
References 2
3 4
5 6 7
Kenedi RM, Cowden JM, Scales JT, editors. Bed sore biomechanics. Basingstoke: Macmillan, 1976: 1-357. Reswick JB, Rogers JE. Experiences at Rancho Los Amigos Hospital with devices and techniques to prevent pressure sores. In: Kenedi RM, Cowden JM, Scales IT, editors. Bed sore biomechanics. Basingstoke: Macmillan, 1976: 301-310. Department of Health. Pressure sores: a key quality indicator. London: Department of Health, 1995. Bouten CVC, Lee DA, Knight MM, Bader DL. Compressive deformation and damage of muscle cell sub-populations in a model system. Journal of Biomechanical Engineering 2001; 29: 153-163. Knight SL, Taylor RP, Polliack AA, Bader DL. Establishing predictive indicators for the status of soft tissues. Journal of Applied Physiology 2001; 90: 2231-2237. Bader DL, editor. Pressure sores-clinical practice and scientific approach. London: Macmillan, 1990: 1-283. Bouten CVC, Oomens CWJ, Baaijens FPT, Bader DL. The aetiology of pressure sores: Skin deep or muscle bound? Archives of Physical Medicine and Rehabilitation 2002 (in press)
JOURNAL OF TISSUE VIABILITY VOL 12 NO. 4 OCTOBER 2002
The impact of bioengineering on tissue viability research uring a brief sunny period this summer, my mind went back to heady days in 1975 when there was a conference entitled Bed Sore Biomechanics held at the Bioengineering Centre at Strathclyde University. It reflected the long-term interest of the host group, headed by Professors Robert Kenedi and Joe Barbenel (a former president of the Tissue Viability Society) on the biomechanics of soft tissues in health and damage, in conjunction with surgical interest from such luminaries as Professors John Scales and Tom Gibson. The volume of the proceedings! includes an impressive list of contributions from a variety of scientific and medical disciplines. However, it is worth examining the impact of bioengineering on the subject in the subsequent years. First, it should be recorded that there has been a consistent core of about 10 bioengineering members of the Tissue Viability Society since its inception. Although this may appear small in number compared to the Society's overall membership, these bioengineers have always been active on both the editorial board and at Tissue Viability Society meetings. Perhaps the most recognised bioengineering activity in pressure ulcer research is in the development of a range of pressure monitoring systems to supersede the previous gold standard, the Talley-Scimedics single cell system (described by Reswick and Rogers in 19762). I was involved in the design of one such development in Oxford (the Oxford Mk IIII, later the Talley Pressure Monitoring system). Nowadays this system, using 96 sensors, has been largely consigned to history, being replaced by systems with a numerous array of sensors and elegant software to display pressure profiles produced by companies including Tekscan and Novel. Such systems are clearly useful in both research and clinical settings, but it is well recognised that pressure measurements alone are not able to alert the clinician to areas of tissue which are particularly vulnerable to ulcer initiation. Most bioengineering activities, based in either university or hospital settings, require funding from either Government agencies, such as the Engineering and Physical Sciences Research Council or the Department of Health (DoH); medical charities, including Action Research; or appropriate companies in the health-care industry. The latter have been forthcoming although such studies either involve assessing the performance of one product (often new) against its competitors or involve comparing a range of support products. Such research is valuable, but will not
D
© Tissue Viability Society 126
provide any insight into many fundamental aspects of the clinical problem, such as aetiology or identification of susceptible subjects. I am reminded of a time in 1993 when the DoH hastily arranged a meeting on pressure ulcers at their headquarters, after an enquiry from one of the Houses about what the Government's policy was about alleviating the clinical problem. A number of the most informed were invited to speak but as the day progressed it became increasingly apparent that this was a white-washing exercise - reinforced by phrases from session chairmen indicating that 'the research was fascinating, but was unlikely to receive future funding from the DoH'. The result was a DoH document3 about current practices, based in part on a financial assessment by Touche Ross. One of the findings that 'prevention was more expensive than treatment', a conclusion based on the premise that all hospital inpatients required a prevention strategy - a message that could have been directed by a political agenda. However, to obtain adequate funding for a 3-year project, proposed research needs to be both scientifically sound with a degree of innovation and be of relevance to areas of topical interest. This is the current situation when agencies are increasingly inclined to announce funding calls involving prescribed research areas. Thus proposals involving nanotechnology, tissue engineering, postgenomics and metabolomics are commonly highlighted. Where does fundamental research associated with a practical clinical problems, such as pressure ulcers, fit into this strategic rubric? Does this mean that we should give up any of our hope of pursuing fundamental research to develop successful preventative strategies for pressure ulcers? The answer must surely be no. An ·increasing trend in biomechanical research is to utilise the potential of fast computing techniques associated with finite element analysis, for example, to predict stresses and strains within structures. This would seem ideal to apply to internal stresses with soft tissues subjected to prolonged loading near bony prominences. Nonetheless attempts to produce realistic analyses are stymied by the lack of suitable material properties characterising the various layers which constitute the soft tissues covering bony prominences. For example, although several studies have examined uniaxial and biaxial properties of skin parallel to its surface, there are few reported studies examining the compressive properties of the soft tissue composite. Such studies have been hampered by the lack of
JOURNAL OF TISSUE VIABILITY VOL 12 NO.4 OCTOBER 2002
.. .
Smith~Nephew
.
.
.
EDITORIAL
appropriate non-invasive techniques, which can characterise material properties of tissue under load. For example, ultrasound has offered much potential for many years but has, as yet, not proved reliable, although more sophisticated systems involving elastography in association with ultrasound imaging might prove successful in the future. Other imaging technologies involving infrared spectroscopy, magnetic resonance imaging and magnetic resonance spectroscopy may also provide valuable data under loading conditions for both healthy tissues and where tissue status is compromised. Further positive spin may be gleaned from the Dutch experience. In 1997, an audit of cost to the health service in the Netherlands indicated that pressure ulcer treatment was the fourth most costly procedure. Although well behind that of cancer, AIDS and cardiovascular disease, this placing has made a tremendous impact on funding for pressure ulcers. In particular, research is flourishing as evidenced by the large number of Dutch attendees at annual meetings of the European Pressure Ulcer Advisory Panel, supported by active research centres in Amsterdam, Maastricht and Eindhoven. Indeed in line with a panEuropean outlook, I have been associated with the Department of Biomedical Engineering in the Technical University of Eindhoven for the last 2 years. This part-time position enables me to investigate pressure ulcers at different hierarchical levels from cell damage4 to pathogenesis of the clinical condition. It has also enabled me to examine loaded tissue changes using advanced magnetic resonance imaging techniques on a system permanently available for research - such systems would be of great value in the UK. Conventional wisdom on the pathogenesis of pressure ulcers has focused on the effects of pressure-induced ischaemia of skin tissues5,6. Although important there are other major considerations, as outlined in a recent viewpoint article 7, involving the lymphatic system, interstitial transport, underlying tissues (particularly the muscle) and ischaemia-reperfusion injury. The latter mechanism has some major implications for the way patients with susceptibility to pressure ulcer
128
development are treated. Pressure relief may have to be re-examined, but I do not intend to alienate all manufacturers of alternating pressure air mattresses. I hope that many of the above issues will be raised at the conference 'Innovations in Pressure Ulcer Biomechanics and Pathophysiology'. It is being organised by the Medical Engineering group of the Institute of Mechanical Engineers, and held at their headquarters on November 25 2002. Its objective is to emphasise the importance of developing a sound scientific approach for understanding the aetiology of pressure ulcers, outlining promising approaches for their prevention. Granting agencies beware.
Dan Bader Professor of Medical Engineering Associate Director of the Interdisciplinary Research Centre in Biomedical Materials Department of Engineering Queen Mary University of London London El 4NS
References 2
3 4
5 6 7
Kenedi RM, Cowden JM, Scales JT, editors. Bed sore biomechanics. Basingstoke: Macmillan, 1976: 1-357. Reswick JB, Rogers JE. Experiences at Rancho Los Amigos Hospital with devices and techniques to prevent pressure sores. In: Kenedi RM, Cowden JM, Scales IT, editors. Bed sore biomechanics. Basingstoke: Macmillan, 1976: 301-310. Department of Health. Pressure sores: a key quality indicator. London: Department of Health, 1995. Bouten CVC, Lee DA, Knight MM, Bader DL. Compressive deformation and damage of muscle cell sub-populations in a model system. Journal of Biomechanical Engineering 2001; 29: 153-163. Knight SL, Taylor RP, Polliack AA, Bader DL. Establishing predictive indicators for the status of soft tissues. Journal of Applied Physiology 2001; 90: 2231-2237. Bader DL, editor. Pressure sores-clinical practice and scientific approach. London: Macmillan, 1990: 1-283. Bouten CVC, Oomens CWJ, Baaijens FPT, Bader DL. The aetiology of pressure sores: Skin deep or muscle bound? Archives of Physical Medicine and Rehabilitation 2002 (in press)
JOURNAL OF TISSUE VIABILITY VOL 12 NO. 4 OCTOBER 2002