TFC (Thoracic Fluid Content): A New Parameter for Assessment of Changes in Chest Fluid Volume

Abstract

Clinical assessment of cardiac status can be difficult and incomplete without an assessment of fluid volume status, especially of the lungs. Now, a new parameter is available, thoracic fluid content (TFC). It is an indicator of total fluid volume, both intracellular and extracellular. Because it is measured noninvasively using impedance cardiography (ICG), it could be a welcome addition to the physician's assessment. An evaluation of TFC was performed beginning with 1) an examination of chest impedance (Z) as an accurate means of following fluid changes, 2) the relationship of TFC to Z using both loop and spot electrodes, and 3) clinical applications of TFC. In 1) 12 dogs, Z was superior (r = 0.935, P < 0.006) to 10 traditional hemodynamic and gas transfer parameters in trending a lactated Ringer's infusion; 2) a plastic model, changes in TFC values derived from Z measurements using both loop and spot electrodes were virtually identical and paralleled infused saline (r = 0.999, P < 0.001); 3) the clinical setting, TFC trended fluid changes well. From these results, we conclude that TFC is a reliable measurement of chest fluid status and of changes in that fluid. Along with cardiac index (CI), also provided by the ICG monitor, TFC can be very helpful to the clinician.