Effect of wheelchair tilt-in-space and recline angles on skin perfusion over the ischial tuberosity in people with spinal cord injury

Abstract

Objective: To investigate the efficacy of wheelchair tilt-in-space and recline on enhancing skin perfusion over the ischial tuberosity in wheelchair users with spinal cord injury (SCI).

Design: Repeated-measures, intervention, and outcomes-measure design.

Setting: A university research laboratory.

Participants: Wheelchair users with SCI (N=11; 9 men, 2 women; mean ± SD age, 37.7±14.2y; body mass index, 24.7±2.6kg/m(2); duration of injury, 8.1±7.5y).

Interventions: Protocols (N=6) of various wheelchair tilt-in-space and recline angles were randomly assigned to participants. Each protocol consisted of a 5-minute sitting-induced ischemic period and a 5-minute wheelchair tilt-in-space and recline pressure-relieving period. Participants sat in a position without tilt or recline for 5 minutes and then sat in 1 of 6 wheelchair tilted and reclined positions, including (1) 15° tilt-in-space and 100° recline, (2) 25° tilt-in-space and 100° recline, (3) 35° tilt-in-space and 100° recline, (4) 15° tilt-in-space and 120° recline, (5) 25° tilt-in-space and 120° recline, and (6) 35° tilt-in-space and 120° recline. A 5-minute washout period (at 35° tilt-in-space and 120° recline) was allowed between protocols.

Main outcome measures: Laser Doppler flowmetry was used to measure skin perfusion over the ischial tuberosity in response to changes in body positions caused by performing wheelchair tilt-in-space and recline. Skin perfusion response to wheelchair tilt-in-space and recline was normalized to skin perfusion of the upright seated position (no tilt/recline).

Results: Combined with 100° recline, wheelchair tilt-in-space at 35° resulted in a significant increase in skin perfusion compared with the upright seated position (no tilt/recline; P<.05), whereas there was no significant increase in skin perfusion at 15° and 25° tilt-in-space (not significant). Combined with 120° recline, wheelchair tilt-in-space at 15°, 25°, and 35° showed a significant increase in skin perfusion compared with the upright seated position (P<.05).

Conclusions: Our results indicate that wheelchair tilt-in-space should be at least 35° for enhancing skin perfusion over the ischial tuberosity when combined with recline at 100° and should be at least 25° when combined with recline at 120°. Although smaller angles of wheelchair tilt-in-space and recline are preferred by wheelchair users for functional purposes, wheelchair tilt-in-space less than 25° and recline less than 100° may not be sufficient for effective pressure reduction for enhancing skin perfusion over the ischial tuberosity in people with SCI.

Figure 1

Configurations of wheelchair tilt-in-space and recline. (a) The angle α indicates the wheelchair tilt-in-space angle. (b) The angle β indicates the wheelchair recline angle.

Figure 2

An example of a complete testing protocol for a resarch participant. It takes 90 minutes to complete all protocols for one participant.

Figure 3

Comparison of skin perfusion in response to wheelchair tilt-in-space (15°, 25°, and 35°) in combination with recline (100° and 120°). During tilted and reclined positions, 4 testing positions showed a significant increase in skin perfusion as compared with the upright seated position (p<0.05); while positions at 15° tilt-in-space and 100° recline and 25° tilt-in-space and 100° recline did not show a significant increase in skin perfusion. When combined with 100° recline, wheelchair tilt-in-space at 35° resulted in a significant increase in skin perfusion as compared with wheelchair tilt-in-space at 15° and 25° (p<0.05); while no significant difference between 15° and 25°. When combined with 120° recline, wheelchair tilt-in-space at 35 resulted in a significant increase in skin perfusion when compared with 15° tilt-in-space (p<0.05). (* indicates p<0.05; T means tilt-in-space and R means recline. Data are shown in the mean values plus standard error.)