Noninvasive assessment of cardiac output: a validation study comparing pulse contour analysis with impedance cardiography
Open Access
- Author:
- Pokorney, Paige Elizabeth
- Area of Honors:
- Biobehavioral Health
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Sheila Grace West, Thesis Supervisor
Dr. Lori Anne Francis, Thesis Honors Advisor - Keywords:
- cardiac output
blood pressure
impedance cardiography
Nexfin
cardiovascular disease - Abstract:
- Accurate assessment of cardiovascular risk is imperative in both clinical and research settings to manage care and analyze research findings. The present study assessed the accuracy of pulse contour analysis from fingertip plethysmography (Nexfin formally known as Finapress) against thoracic impedance cardiography (ICG) in measuring both absolute and changes in systolic blood pressure (SBP), diastolic blood pressure (DBP), cardiac output (CO), stroke volume (SV), and total peripheral resistance (TPR). Validation studies comparing ICG and more invasive methods have shown that it is a reliable method for estimating change in CO. ICG requires patients to undress and/or undergo hair removal. Some studies have suggested that the Nexfin device can accurately index changes in CO without this inconvenience. To our knowledge this is the first study to compare hemodynamic measurements from Nexfin to those obtained with ICG. On average, the Nexfin SBP value was 12.2 ± 4.1 mmHg higher than the same measurement collected via ICG. For DBP, the discrepancy was 2.7 ± 1.7 mmHg on average. As expected, we observed robust correlations for resting SBP (r = 0.67, P = 0.01) and DBP (r = 0.59, P = 0.03) measured between the two systems. There were no significant correlations for resting TPR, CO, and SV between the two methods. Correlation values ranged from -0.19 to +0.09 (all P’s > 0.54). Between-method measurements of SBP and DBP during stress were significantly correlated, while measures of TPR, CO, and SV were uncorrelated. We found a robust correlation between CO change scores collected with the two methods (r = 0.57, P = 0.05). This correlation was not evident for change in TPR and SV. Change in SBP and DBP during stress were correlated between the two methods (r = 0.85, P = 0.0002; r = 0.73, P = 0.005 respectively). Our study shows Nexfin is a reliable method of measuring both absolute and change in SBP and DBP. Results confirm previous findings of the accuracy of fingertip plethysmography in measuring changes in CO. However, the systematic variability between methods observed does not make the Nexfin device conducive to critical clinical use.