Evaluating the Effect of Leg Position and Negative Pressure Wound Therapy on Lower Extremity Oxygenation Measured by Noninvasive Tissue Oximetry: A Pilot Study

Abstract

Background Flap loss is a catastrophic complication following lower extremity reconstructions. Close monitoring can detect circulatory changes, particularly when introducing gravity through dangle protocols. Noninvasive near-infrared spectroscopy (NIRS) tissue oximetry is one such method used for continuous monitoring of tissue perfusion. Recently, negative pressure wound therapy (NPWT) has been for compromised flaps salvage. We used NIRS to study the impact of leg positioning and NPWT on lower extremity perfusion during a mock dangle protocol. Methods A tissue oximeter transcutaneous probe was placed on each lower limb of five normal patients at the location of the highest density of peroneal artery perforators along the distal one-third fibula. The experimental leg probe was covered with NPWT at 100 mm Hg. The contralateral leg served as control. Tissue oxygen saturation (StO2) was measured continuously for 140 minutes. Leg position was changed in every 20 minutes to mimic a dangle protocol. Results Our results showed higher StO2 with leg elevation, and lower StO2 in dependent positions in the control limb. StO2 was consistently higher in the limb with NPWT, which had a slower rate of deoxygenation with introduction of gravity. In both conditions, on returning to neutral position from the dependent, StO2 returned to levels close to baseline. Conclusion These data provide further information on hemodynamic changes introduced by gravity, and how NPWT might modulate these changes.

Keywords

• negative pressure wound therapy
• noninvasive tissue oximetry
• lower extremity oxygenation