Measuring Tissue Perfusion During Pressure Relief Maneuvers: Insights Into Preventing Pressure Ulcers

Abstract

Background/Objective: To study the effect on tissue perfusion of relieving interface pressure using standard wheelchair pushups compared with a mechanical automated dynamic pressure relief system. Design: Repeated measures in 2 protocols on 3 groups of subjects.Participants: Twenty individuals with motor-complete paraplegia below T4, 20 with motor-complete tetraplegia, and 20 able-bodied subjects.Methods: Two 1-hour sitting protocols: dynamic protocol, sitting configuration alternated every 10 minutes between a normal sitting configuration and an off-loading configuration; wheelchair pushup protocol, normal sitting configuration with standard wheelchair pushup once every 20 minutes.Main Outcome Measures: Transcutaneous partial pressures of oxygen and carbon dioxide measured from buttock overlying the ischial tuberosity and interface pressure measured at the seat back and buttocks. Perfusion deterioration and recovery times were calculated during changes in interface pressures.Results: In the off-loading configuration, concentrated interface pressure during the normal sitting configuration was significantly diminished, and tissue perfusion was significantly improved. Wheelchair pushups showed complete relief of interface pressure but incomplete recovery of tissue perfusion. Conclusions:Interface pressure analysis does not provide complete information about the effectiveness of pressure relief maneuvers. Measures of tissue perfusion may help establish more effective strategies. Relief achieved by standard wheelchair pushups may not be sufficient to recover tissue perfusion compromised during sitting; alternate maneuvers may be necessary. The dynamic seating system provided effective pressure relief with sustained reduction in interface pressure adequate for complete recovery of tissue perfusion. Differences in perfusion recovery times between subjects with spinal cord injury (SCI) and controls raise questions about the importance of changes in vascular responses to pressure after SCI.

Development of intelligent model for personalized guidance on wheelchair tilt and recline usage for people with spinal cord injury: Methodology and preliminary report

“…The protocol consisted of six clinically recommended testing conditions, the combination of three tilt angles at 15°, 25°, and 35°, and two recline angles at 100° and 120°. Each testing condition was divided into three equal periods starting with a 5 min sitting-induced ischemic period without performing tilt or recline, followed by a 5 min pressure reduction period by means of tilt and recline, and concluding with a 5 min washout period, which was designed to allow participants to fully recover skin blood flow and reduce the carryover effect [6]. The details of protocols are described in our previous study [17].…”

“…Clinical evidence shows that turning patients regularly (e.g., every 2-4 h) can lower the incidence of pressure ulcers [3], and sitting-induced pressure can be relieved by performing wheelchair tilt and recline functions [3,[5][6]. The wheelchair tilt function refers to the adjustment of the seat orientation angle (measured against the ground) while keeping the seat-to-back angle unchanged.…”

“…The rationale is that skin blood flow response to loading pressure has been widely used to determine the effectiveness of seating conditions [6,[17][18][19]. The purpose of periodically performing wheelchair tilt and recline is to develop reactive hyperemia to reperfuse the ischemic tissues because prolonged tissue ischemia has been determined to be critical factor leading to pressure ulcers.…”

Development and initial validation of the Seated Posture Scale

“…Upright positioning in wheelchairs that influences posture affects key health outcomes such as breathing, eating, and pressure ulcer development [1][2][3][4][5][6][7][8]. Posture and outcomes will be poor if the wheelchair is inadequate.…”

Physical activity and transcutaneous oxygen pressure in men with spinal cord injury

“…However, the mechanical properties are not the only characterizations that indicate the risk of tissue damage. Note that not only the absolute values of pressure can vary from person to person, but also the variations in tissue composition of the high-risk areas can determine how soft tissues change in order to bear certain pressures [21]. In that sense, the cushion's mechanical behavior does not have much significance as a single determination of threshold value to determine the risk of tissue injury.…”