Principles of Pressure Management Douglas A. Hobson, Ph.D. RERC on Wheeled Mobility* Department of Rehabilitation Science and Technology University of Pittsburgh *support by: the National Institute on Disability and Rehabilitation Research     Pressure Sore Incidence and Costs 40% occur in hospital- (lying ulcers-sacrum, heels, elbows) 30% occur post discharge (sitting ulcers -sacrum, ischium) Cause of mortality in about 4% of SCI people Repair costs-$15-60k/ incident Social/psychological costs immeasurable!!   Populations at Risk Spinal Cord Injured Immobile Elderly Diabetics ALS, MS, MD Immobility is greatest risk factor Risk assessment scales have been developed (e.g., Braden scale, Norton scale)       The Etiology of Pressure Ulcers (prime factors) If repeated assault occurs, the breakdown process will begin. Deep tissue distortion due to shear forces also major contributing factor. Surface sores can result from repeated surface friction/abrasion.         Pressure Tolerance Guidelines   The Etiology of Pressure Ulcers (prime factors) If repeated assault occurs, the breakdown process will begin. Deep tissue distortion due to shear forces also major contributing factor. Surface sores can result from repeated surface friction/abrasion.     Other Contributing Factors Immobility- close correlation between onset and frequency of movement. Loss of sensation-evidence that denervated tissue has reduced nutrition and oxygen perfusion. Body Type- does not seem to be any relationship between body-type and deep ulcers. Surface friction may increase with heavier people. Nutrition-inadequate dietary intake can result in muscle atrophy, anemia, low protein levels and vitamin C deficiency reducing skin integrity. Infection-increased metabolic rate, higher oxygen demand endangers ischemic tissue.     Typical Superficial Ulcer Development       Development of Typical Deep Ulcer           Five Clinical Stages of Pressure Development Stage I - blanching of reddened area experiencing reactive hyperemia circulation intact, redness disappears in reasonable time (1-2 hrs) Stage II - blanching does not occur, redness remains Stage III - ulceration progresses beyond the dermis to subcutaneous tissue redness remains around edges, hardening of tissue occurs Stage IV - ulceration progresses to fat layer and muscle becomes swollen. Stage V - necrosis (dying tissue) penetrates deep fascia, muscle and sometimes bone. Surgical repair necessary, requires 2-6 months of inactivity.       Pressure Ulcer Risk Factors     Principles of Clinical Pressure Management Maximize the surface area: decrease the pressure on any one location (peak pressures) Redistribute body weight: use support surface shape and materials with required properties. Minimize asymmetries: i.e., unequal loading of pelvic structures and tissues. Training for pressure relief: i.e., regular weight relieving movements Dietary instruction: critical to both good health and skin integrity Instruction for lifting/ transferring: whenever possible person should instruct care-givers Personal hygiene and skin care: very important!       Skin Viability Measurement Techniques Skin blanching Measurement of interface pressure (single site and mapping) Thermography Oxygenation of blood flow Measurement of tissue deformation - Brienza Measurement tissue stiffness - Brienza     Pressure Measurement Technologies   Electropneumatic bladder   Pneumatic bladder Fluid filled bladder Thick film resist. Element   Capacitive element     Single Cell vs. Mapping Devices   Single bladder type devices are: more accurate and repeatable more difficult to use provide limited information allow single or continuous measurements Mapping devices: provide posture and relative pressure information allow graphical displays are quicker to use and provide much more information are more expensive allow single or continuous measurements       Clinical Applications (Lipka, 1997) Objective representation of peak pressure Differential comparison of support surfaces Effectiveness of weight shifting interventions Wheelchair configuration set-up Clinical validation     Pressure Mapping Systems     Pressure Mapping as Biofeedback     Shifting to One Side     Shifting Forward   Comparative Study Ferguson-Pell & Cardi (1992) Three computer-based devices. Four different cushion types. Results, comparisons of readings between different cushions, same subject, may produce errors as much as 10mmHg.       Interpretation of Pressure Data: A Few Precautions Comparison of absolute pressure values can be misleading. Measurement device may be altering the distribution of surface forces (e.g, hammocking). Relative pressure comparisons are probably most useful.     Cushion Types     Key Properties of Cushion Materials (Sprigle, 1992) Density - weight/volume ratio. Stiffness - measure of softness. Resilience - ability to recover shape. Dampening - absorb impact loads. Envelopment - surface area covered.     Positioning for Pressure and Postural Management planer vs. sling seat surface provide appropriate pressure relieving cushion incline seat (5-10°) firm contoured back, reclined 10-20° match backrest height to user needs. add lumbar pad (optional). adjust arm and foot rests for optimal weight distribution. provide weight relief accessories to wheelchair (recline/tilt) as necessary. provide training on weight relief and use of seating and/or wheelchair system.     References: Ferguson-Pell, M. & Cardi. (1992). Pressure Mapping, XXX, Oct., 30-35 Ferguson-Pell, M. & Cardi. (1993). Development and comparative evaluation of W/C pressure mapping. Assistive Technology. 5:78-91 Sprigle, S. (1993). Using Seat Contour during Seating Evaluations of Individuals with SCI, Assistive Technology. 5:24-35. Brienza, D.; Karg, P. & Brubaker, C. (1996). Seat cushion design for elderly wheelchair users based on minimization of soft tissue deformation using stiffness and pressure measurements. IEEE Transactions on Rehabilitation Engineering, 4(4)320-328.