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Studies on sitting pressure and buttock microcirculation: aiming at developing an alarm in the prevention of pressure ulcers in patients with spinal cord injuries
Linköping University, Department of Biomedicine and Surgery. Linköping University, Faculty of Health Sciences.
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Pressure ulcers in patients with spinal cord injuries are a major problem, the prevalence in this group being reported as high as 20 – 30 percent. Most pressure ulcers develop around the pelvic girdle, and the key-contributing factor in the development of pressure ulcers is ischaemia due to longstanding pressure. Loss of mobility and lack of sensation below the level of injury are prominent risk factors for the development of pressure ulcers. Although many factors are known to contribute to pressure ulcer development, the exact aetiology is not completely clear. Prevention is suggested as the best way to deal with the problem. The studies in this thesis investigate some aspects of the physiology of sitting in patients with spinal cord injuries and healthy controls, aiming at developing a pressure ulcer alarm device to aid in the prevention of pressure ulcers. Methods used are laser Doppler perfusion imaging (LDPI) for measurement of superficial skin blood flow, as well microdialysis and a microelectrode (Licox®) to measure direct and indirect signs of ischaemia. In addition sitting pressures are mapped. The main findings are that patients with spinal cord injuries have almost four-fold mean maximum sitting pressures 43 and 49 N/cm2, left and right buttock) compared with healthy controls 12 and 13 N/cm2, left and right buttock). In the subcutaneous fat in healthy individuals, the tissue oxygen pressure decreases significantly during 30 minutes of sitting on a wheel chair cushion 13,7 mmHg) compared with 30 minutes of sitting on a hard surface 19,8 mmHg) implying that the tissues deep in the skin are exposed to a reduction in blood supply. This is also confirmed by a decrease in extracellular glucose during sitting for 30 minutes on a hard surface 1,8 mmol/L) and on a wheel chair cushion 1,7 mmol/L). The post-sitting reactive hyperaemia is dependent on duration of sitting in both patients and healthy subjects. It seems to be attenuated in patients in the sitting position but intensified while lying prone. Furthermore, four repeated loadings on a hard surface 15 minutes of sitting followed by five minutes of rest) without allowing the tissues to return to resting perfusion results in a significantly increasing reactive hyperaemia for each loading in healthy subjects, suggesting that it is important to unload the buttock skin completely before the next sitting period starts. This thesis also describes the construction of an alarm device that measures surface interface pressures during sitting continuously in eight predefined points, to alert the user by an audible signal after a given period of time when the pressure has reached a dangerously high level. It is concluded that the reactive hyperaemia that is observed in the buttock skin after sitting, as well as the reduction in glucose and oxygen in adipose tissue during sitting, are due to a reduction in blood supply relative or absolute ischaemia) caused by a compression of the vasculature by the ischial tuberosities. These findings imply a multilayer aetiology in pressure ulcer development. The altered hyperaemic reaction in patients with spinal cord injuries after sitting is possibly related to alterations in sympathetic activity due to the cord lesion. Lastly, the alarm device is supposed to be an aid to pressure ulcer prevention in patients with spinal cord injuries who lack normal sensory feedback.

Place, publisher, year, edition, pages
Institutionen för biomedicin och kirurgi , 2006. , 83 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 950
Keyword [en]
Blood supply, Buttocks, Hyperemia, Ischemia, Laser-Doppler flowmetry, Microcirculation, Posture physiology, Pressure, Skin blood supply
National Category
Clinical Science
Identifiers
URN: urn:nbn:se:liu:diva-7469ISBN: 91-85497-90-8 (print)OAI: oai:DiVA.org:liu-7469DiVA: diva2:22464
Public defence
2006-06-08, Elsa Brändströmsalen, Campus US, Linköpings Universitet, Linköping, 13:00 (English)
Opponent
Supervisors
Available from: 2006-09-28 Created: 2006-09-28 Last updated: 2012-10-23Bibliographically approved
List of papers
1. Sitting pressure and perfusion of buttock skin in paraplegic and tetraplegic patients, and in healthy subjects: a comparative study
Open this publication in new window or tab >>Sitting pressure and perfusion of buttock skin in paraplegic and tetraplegic patients, and in healthy subjects: a comparative study
2002 (English)In: Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery, ISSN 2000-656X, E-ISSN 2000-6764, Vol. 36, no 5, 279-283 p.Article in journal (Refereed) Published
Abstract [en]

The distribution of sitting pressure and ability to respond with reactive hyperaemia were studied in a group of paraplegic and tetraplegic patients (n = 8) with spinal cord lesions and healthy controls (n = 10) using a pressure sensitive plate and laser Doppler perfusion imager. The results show that the mean sitting pressure of the patients was 9.9 N/cm2 (left) and 11.7 N/cm2 (right) compared with 3.5 N/cm2 (left) and 3.6 N/cm2 (right) in controls. The differences were significant on both the left (p < 0.01) and right (p < 0.05) sides. The maximum pressure in patients was 42.9 N/cm2 (left) and 48.7 N/cm2 (right), and in controls 12.0 N/cm2 (left) and 12.9 (right) (p < 0.01). Both groups showed a reduction in skin perfusion in the seat area during sitting compared with unloaded resting, and in the controls it was significantly increased (p < 0.001 on both sides) during the reactive hyperaemic phase immediately after sitting. Compared with the preload values, the patients showed a similar but slightly weaker picture significant on the right side (p < 0.05), but not on the left. The hyperaemia was not uniformly distributed, but occurred where the pressure was greater than 2 N/cm2. There was no correlation between the amount of reactive hyperaemia and absolute values of sitting pressures. We conclude that tetraplegic and paraplegic patients have significantly higher sitting pressures than normal controls, and that the hyperaemic response in the buttock region in the upright position after pressure load is slightly weaker in the patients, which could be of importance for the development of decubitus ulcers.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-25222 (URN)10.1080/028443102320791824 (DOI)9661 (Local ID)9661 (Archive number)9661 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13Bibliographically approved
2. Perfusion of the skin of the buttocks in paraplegic and tetraplegic patients, and in healthy subjects after a short and long load
Open this publication in new window or tab >>Perfusion of the skin of the buttocks in paraplegic and tetraplegic patients, and in healthy subjects after a short and long load
2006 (English)In: Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery, ISSN 2000-656X, E-ISSN 2000-6764, Vol. 40, no 3, 153-160 p.Article in journal (Refereed) Published
Abstract [en]

In patients with spinal cord injuries (n=8) and healthy controls (n=8) the hyperaemic response in the buttock skin after sitting on a hard surface was studied using a laser Doppler perfusion imager. They sat for three minutes (short load), or 15 minutes (long load). An exponential mathematical function was used to compare the mean perfusion during the observed interval. The results showed that preloading perfusion is significantly higher among patients than healthy subjects. In both groups, the microcirculation of the skin increased significantly after loading, and peak perfusion was significantly lower after the short load. The mean perfusion was higher among the patients after both loadings, which suggests that there was stronger ischaemic provocation. The main outcome was that there was a dose-response relation between duration of loading and intensity of reactive hyperaemia, and that patients with spinal cord injuries have greater perfusion before and after loading than healthy controls.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-37630 (URN)10.1080/02844310600693179 (DOI)36825 (Local ID)36825 (Archive number)36825 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13Bibliographically approved
3. Perfusion of buttock skin in healthy volunteers after long and short repetitive loading evaluated by laser Doppler perfusion imager
Open this publication in new window or tab >>Perfusion of buttock skin in healthy volunteers after long and short repetitive loading evaluated by laser Doppler perfusion imager
2007 (English)In: Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery, ISSN 2000-656X, E-ISSN 2000-6764, Vol. 41, no 6, 297-302 p.Article in journal (Refereed) Published
Abstract [en]

Frequent unloading is vital to avoid pressure ulcers of the seat area in patients with injuries to the spinal cord. The duration of unloading is probably as important as that of the sitting period in the prophylaxis of pressure ulcers. The aim of this study was to investigate the microcirculatory reactions after occlusion of the buttock skin after repeated ischaemic provocation. The perfusion of buttock skin was studied with a laser Doppler perfusion imager (LDPI) in healthy people after short and long periods of sitting (repeated four times). The perfusion increased significantly during the consecutive loadings compared with the first loading, and this effect was more profound after the long load. Repeated periods of ischaemia of the buttock skin without allowing the tissues to recover resulted in increasing reactive hyperaemia, and are therefore probably more damaging than single loadings. This is important when establishing clinical guidelines for the prophylaxis of pressure ulcers in patients with spinal cord injuries.

Keyword
Decubitus ulcer, Laser Doppler perfusion imaging, Reactive hyperaemia, Repetitive loading, Sitting pressure, Spinal cord injury
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-47789 (URN)10.1080/02844310701633249 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13Bibliographically approved
4. Sitting can cause ischaemia in the subcutaneous tissue of the buttocks, which implicates multilayer tissue damage in the development of pressure ulcers
Open this publication in new window or tab >>Sitting can cause ischaemia in the subcutaneous tissue of the buttocks, which implicates multilayer tissue damage in the development of pressure ulcers
2009 (English)In: Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery, ISSN 2000-656X, E-ISSN 2000-6764, Vol. 43, no 2, 82-89 p.Article in journal (Refereed) Published
Abstract [en]

A better understanding of how pressure ulcers develop in the buttocks will improve prophylactic measures. Our aim was to investigate signs of reduced perfusion and ischaemia in the subcutaneous fat in the buttocks during sitting. A microelectrode was used to quantify oxygen (pO2). Metabolites that indicate aerobic or anaerobic metabolism (glucose, lactate, pyruvate, and glycerol) were quantified using microdialysis. Sixteen healthy people were studied while they sat on a wheel chair cushion, and a hard surface. Sitting pressures were mapped, and the thickness of the subcutaneous fatty layer was measured. The results showed that pO2 and glucose were significantly reduced during sitting, and for pO2 the effect is significantly more profound during sitting on a hard surface. After loading, both glucose and pO2 increased significantly. We conclude that the subcutaneous adipose tissue covering the ischial tuberosities becomes ischaemic during sitting. This finding supports the theory that not only is the skin involved in early development of pressure ulcers, but also the deeper tissues.

Keyword
Pressure ulcer development, spinal cord injury, ischaemia, reperfusion, microdialysis, microelectrode, adipose tissue, sitting pressure
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-17697 (URN)10.1080/02844310902749455 (DOI)
Available from: 2009-04-16 Created: 2009-04-14 Last updated: 2017-12-13Bibliographically approved
5. A pressure-controlled alarm and monitoring device for pressure ulcer prophylaxis in patients with traumatic spinal cord injury: a prototype
Open this publication in new window or tab >>A pressure-controlled alarm and monitoring device for pressure ulcer prophylaxis in patients with traumatic spinal cord injury: a prototype
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Patients with spinal cord injury are prone to develop pressure ulcers, especially around the pelvic girdle and in the buttocks. Treatment of pressure ulcer is demanding for the health care system in terms of personal and economic resources, and for the patient because of extensive conservative or surgical treatments to achieve healing. The prevention of pressure ulcers is therefore of major importance for this patient group. A contributing factor to the development of pressure ulcers is the lack of biosensory feedback below the level of injury, that results in a lack of impulses to the patient to change body position. In this paper we describe the construction of a technical device that monitors sitting pressures in a wheel chair cushion, and alerts the user when the pressure has reached a critical level for a period of time long enough to risk tissue damage. This device also saves pressure data continuously for retrospective analysis to evaluate the patients' sitting and unloading behaviour, and to study the effect of pressure relieving wheel chair cushions over longer periods of time.

Keyword
Pressure ulcer prevention, alarm device, sitting pressure, spinal cord injury, prototype
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-84827 (URN)10.1007/978-3-642-03885-3_184 (DOI)
Available from: 2012-10-23 Created: 2012-10-23 Last updated: 2014-08-29Bibliographically approved

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Thorfinn, Johan

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