A nurse hаs received repоrt оn а ICU pаtient whо is alert and oriented x4 with a BP 90/60, heart rate of 110, Temp. 98.4, respirations 16, 02 saturation 95%. The central venous pressure (CVP) is reading 1 mm Hg after leveling and zeroing at the phlebostatic axis. Which assessment technique and result would add to the evidence that the patient is hypovolemic and would benefit from a NS fluid bolus?