Effects of Intermittent Pneumatic Compression on Leg Vascular Function in People with Spinal Cord Injury: A Pilot Study

Abstract

Objective: The purpose of this pilot study was to determine whether 60 mins of intermittent pneumatic compression therapy (IPC) could acutely increase leg blood flow-induced shear stress and enhance vascular endothelial function in persons with spinal cord injury (SCI). Design: Pretest with multiple posttests, within subject randomized control design. Setting: University of Southern Mississippi, Spinal Cord Injury Research Program within the School of Kinesiology, recruiting from the local community in Hattiesburg, Jackson, and Gulfport, MS. Participants: Eight adults with SCI (injury level: T3 and below; ASIA class A-C; age: 41±17 yrs). Interventions: A 60-min IPC session was performed in one leg (experimental leg; EXP), with the other leg serving as a control (CON). Outcomes Measures: Posterior-tibial artery shear rate (Doppler-ultrasound) was examined at rest, and at 15 and 45 mins during IPC. Endothelial function was assessed using the flow-mediated dilation (FMD) technique, before and after IPC. Results: Resting FMD (mm) was similar between legs at rest. A two-way repeated measures ANOVA (leg x time) revealed that during IPC, peak shear rate increased in the EXP leg (215±137 to 285±164 s^-1 at 15 mins; +39±29%, P = 0.03), with no change occurring in the CON. In addition, FMD significantly increased in the EXP leg (Pre IPC: 0.36±0.14 vs. Post IPC: 0.47±0.17 mm; P = 0.011, d = 0.66), with no change occurring in the CON leg. Conclusion: These preliminary findings suggests that IPC therapy may acutely increase leg shear stress within 15 mins, with a resultant moderate-large improvement in vascular endothelial function after 60 mins in people with SCI.

Keywords: Compression Therapy; Endothelial Function; Spinal Injury.

Figure 1.

Doppler-ultrasound image of posterior-tibial artery blood velocity (cm/sec) response to 15 mins of IPC in the EXP leg of a representative subject (Panel A). Note the increase in blood velocity (i.e., increase in shear rate) following IPC cuff deflation. Panel B expands the 16 sec Doppler blood velocity sweep to highlight metrics (i.e., bracketed regions) used for calculating mean, peak, and oscillatory shear index—OSI profiles.

Figure 2.

Representation of shear rate response to IPC. Panel A depicts mean shear (3 compression cycle average); Panel B depicts peak shear (peak response from 3 compression cycles averaged); Panel C depicts the oscillatory index (ratio of retrograde to mean shear). *Denotes P<0.05 between Pre and Post IPC within EXP leg.

Figure 3.

Individual (left side panel) and mean summary data (right side panel) for absolute FMD (mm) at baseline (pre) and 60-minutes post-IPC (post) for the EXP (Panel A) and CON leg (Panel B), respectively. Dashed lines represent subjects with documented cardio-metabolic disease (type-2 diabetes, obesity, and coronary artery disease). *Denotes P<0.05 between Pre and Post IPC within EXP leg.

Figure 4.

Summary of relative FMD (%) between EXP and CON legs following 60 mins IPC. *Denotes P<0.05 between Pre and Post IPC within EXP leg.