Tonometry of Deep Tissues for Setting Effective Compression Pressures in Lymphedema of Limbs.

Background: The therapeutic intermittent pneumatic compression (IPC) pressures are usually set arbitrarily at levels between 40 and 60mmHg. However, it is not known how much force has been transferred to edema fluid. There is a need to know how high edema fluid pressures should be generated to evacuate the stagnant fluid. The externally applied compression force dissipates in hard tissues and only a portion of it is conveyed to tissue fluid. Simultaneous measuring of compression force using deep tissue tonometry and recording edema fluid pressures under a tonometer would give hints of how high should therapist or patient set IPC pressures to mobilize fluid. Aim: (1) To simultaneously measure the applied tonometer force and the generated edema fluid pressures under the tonometer, (2) to plot tonometer force against fluid pressure data to create a correlation curve for setting pressure of IPC at levels initiating fluid flow, (3) to work out a formula for setting pressures in the pneumatic device for individual patient, based on tonometry, (4) to prove the value of formula on a cohort of patients treated with IPC. Methods: Deep tissue tonometry force and tissue fluid pressures under the tonometer indentor were measured in lower limbs in a group of 20 patients with lymphedema stages I-III. Results: (1) Deep tissue tonometry penetrating to a depth of 10mm provided data on pressure generated in tissue fluid under the tonometer indentor. (2) Plotting the applied tonometer force against the tonometer-generated tissue fluid pressures revealed that force to reach the threshold of 30mmHg fluid pressure necessary for initiation of flow should be >1000g/sq. cm. (3) A formula, based on tonometry values, for setting ICP pressures at levels generating pressures for initiating edema fluid flow was worked out. (4) Usefulness of the formula for setting IPC at effective levels was proved on a cohort of patients. Conclusions: Deep tissue tonometry of limbs is useful for setting IPC devices at compression pressures for mobilizing edema fluid.