Early detection of hypovolemia by venous pulse wave velocity and vena cava ultrasound imaging

Purpose: Non-invasive assessment of the volemic status is still an open and urgent clinical need. The pulse wave velocity in the venous compartment (vPWV) has recently been re-proposed as a possible indicator but still needs to be tested in different settings including hypovolemic conditions. Methods: The present study aims at investigating the response of the vPWV to hypovolemic changes of different magnitude, as provided by the lower body negative pressure (LBNP) and using the ultrasound monitoring of the inferior vena cava (IVC) as a reference. In 28 healthy subjects, vPWV was measured at the arm during exposure to short (90 s at -10, -20, -30, -40 mmHg) and long (5 min at -30 mmHg) exposure to LBNP, along with arterial blood pressure (ABP) and heart rate (HR). In a subgroup of 17 subjects IVC was successfully monitored and the full-time course of IVC diameter (dIVC) and collapsibility indices were extracted from the recording. Results: While collapsibility indices were little responsive, vPWV and dIVC were significantly affected by LBNP, decreasing by 19.5 ± 9.7 and 20.9 ± 21.3% at -10 mmHg, respectively. Only the respiratory caval index exhibited significant increases at LBNP ≤ 30mmHg. As compared to other variables vPWV exhibited best reproducibilty: coefficient of variation < 5%. Conclusion: vPWV appears to be a promising non-invasive indicator of blood volume decrease with early high sensitivity and reproducibilty.