Figure 1. Air plethysmography data obtained from tracings. EF: ejection fraction; EV: ejected volume; RV: residual volume; RVF: residual volume fraction; VFI: venous filling index; VFT: venous filling time; VV: venous volume. (A) Baseline with leg elevated 45 degrees; (B) The patient stands and a plateau in leg volume is reached; (C) The patient is then asked to perform a single heel-raise maneuver and a decrease in volume is recorded; (D) The patient is asked to perform 10 heel-raise maneuvers and a new plateau is recorded; (E) Finally, the patient is asked to remain standing.