New Limb Compression Device Increases Skin, Muscle, and Bone Microvascular Flows

1. New Limb Compression Device Increases Skin, Muscle, and Bone Microvascular Flows Alan R. Hargens, Brandon R. Macias, Timothy B. Neuschwander, and Qiuxia Zhang Department of Orthopaedic Surgery, University of California-San Diego San Diego, California UCSD UCSD INTRODUCTION: DISCUSSION AND CONCLUSIONS: Compression therapy is used to improve lower extremity wound healing.1 Various forms of compression are reported to increase local blood flows about 10-30%.2,3,4 Improved technology to reduce edema and to increase skin, muscle, and bone blood flows (Fig. 1) beyond the limits of current devices may enhance wound and possibly, bone fracture healing. We hypothesize that lower extremity compression with a new, simple and inflatable device will increase skin, muscle, and bone microvascular flows to levels significantly higher than previously documented with other devices. Our new compression device increases skin, muscle, and bone microvascular flows to levels greater than previously reported and thus, may enhance wound and bone- fracture healing. Although our results are counterintuitive, they may be explained by a myogenic response within arterioles of skin, muscle, and bone (Fig. 6). Bochmann and co-workers attribute a similar increase of arterial perfusion to a myogenic effect when the human forearm is compressed at pressures ranging from 13 to 23 mmHg.2 Morris and associates document a 10.6% increase in bone uptake of a radiopharmaceutical during 60 mmHg intermittent pneumatic compression of one- minute durations.3 Our new device may improve circulation and healing rates similar to inelastic compression leggings1 which generate compression levels over the skin of about 40 mmHg.6 In summary, our novel device raises microvascular flows in the leg to levels between 168 and 228% of normal at a compression level of 40 mmHg. Figure 1. Microcirculatory controland transcapillary fluid homeostasis Figure 3. Photoplethysmography (PPG). Green light detects skin microvascular blood flow. Near-infrared light detects muscle and bone microvascular blood flows (penetrates 13mm into tissue). PPG measures relative changes and is different from near infrared spectroscopy (NIRS). External Compression Arteriolar Dilation P P METHODS: P RESULTS: in in in A simple compression device was placed around the lower extremity of 10 normal subjects and inflated to 40 mmHg (Fig. 2). The device consisted of an inflatable plastic chamber with seal proximal to the subject’s knee. Seal tightness was important as a very tight seal impeded venous return from the leg. A noninvasive photoplethysmography (PPG) probe was placed on the skin overlying the tibialis anterior muscle to measure both skin and muscle microvascular flows continuously (Fig. 3).5 A second PPG probe was placed on the skin overlying the anterior surface of the tibial diaphysis to measure bone microvascular flow continuously. PPG peak-to-peak amplitudes were normalized to the baseline-control value before compression (100%) and mean data were compared using paired t-tests. During 40 mmHg compression with our new inflatable device in 10 subjects, skin microvascular blood flow (mean ± SE) increased significantly to 168±31% (Fig. 4, p<0.05 compared to 100% baseline-control value). Muscle microvascular flow increased significantly to 228±37% of the baseline-control value (p<0.01) and bone microvascular flow increased significantly to 184±19% of the baseline-control value during 40 mmHg compression (p<0.005). The device did not touch the skin when inflated except at the proximal seal and was comfortable at a compression level of 40 mmHg. P P out P out out Figure 6. Myogenic response mechanism for vasodilation and increased microvascular flow • REFERENCES: • Blecken SR, Villavicencio JL, and Kao TC. Comparison of elastic versus nonelastic compression in bilateral venous ulcers:a randomized trial. J Vasc Surg 42:1150-1155, 2005. • Bochmann RP, Seibel W, Haase E, Hietschold V, Rodel H, and Deussen A. External compression increases forearm perfusion. J Appl Physiol 99(6):2337-44, 2005. • Morris RJ, Elsaid M, Elgazzar AH, Zaid TM, Evans WD, and Woodcock JP. The effect of intermittent pneumatic compression on the bone uptake of (99m)Tc-labelled methylene diphosphonate in the lower limb. Arch Orthop Trauma Surg 125(5):348-54, 2005. • Junger M, Steins A, Hahn M, and Hafner HM. Microcirculatory dysfunction in chronic venous insufficiency (CVI). Microcirculation 7(6 Pt 2): S3-12, 2000. • Zhang Q, Lindberg LG, Kadefors R, and Styf J. A non-invasive measure of changes in blood flow in the human anterior tibial muscle. Eur J Appl Physiol 84(5):448-52, 2001. • Kline CN, Kraus E, Macias BR, Neuschwander TB, Angle N, Bergan J, and Hargens AR. Inelastic compression system produces a reverse-pressure gradient and significantly higher skin surface pressures as compared to an elastic compression legging. American Venous Forum, San Diego, CA, 9am talk, 15 February 2007. * in * * DEDICATION: This poster is dedicated to the memory of Frank D. Shaw (1919-2006) who invented and pioneered development of inelastic compression leggings. Figure 4. Significant increases of normalized skin, muscle and bone microvascular flows compared to baseline-control values without compression (100%) Figure 2. New Compression Device does not touch skin at the treatment site and can be sterilized internally.