Comparison of Invasive vs. Noninvasive CVP Monitoring in Patients Undergoing Major Intra-Abdominal Surgery: A Prospective Comparative Pilot Study

Abstract

Background: The primary objective of the study was to compare central venous pressure (CVP) measured invasively to one measured non-invasively (NICVP) by monitoring upper arm blood flow changes in response to externally applied circumferential pressure to the upper arm veins. Methods: The NICVP monitor (NeuMeDx®) employs impedance plethysmography using 4 electrodes and a blood pressure cuff to determine a person's CVP. Three invasively measured CVP pressure measurements were compared to the NICVP taken during the same time period after induction of anesthesia in 29 patients. Results: Data from both methods were normally distributed and, in paired tests, were not significantly different (p=0.255). Over 95% of the values were within 3.0 mmHg of each other, the threshold estimate for clinical equivalence. The two measurements were highly correlated (r=0.657) and a Bland-Altman analysis showed good agreement. Conclusions: The non-invasive device was accurate and able to mirror the invasive CVP in our study population. Trial registration: #03705299, Clinical trials.gov