Analysis of cardiovascular responses to passive head-up tilt using continuous pulse wave analysis and impedance cardiography.

OBJECTIVE

To non-invasively measure central haemodynamics, arterial stiffness, cardiac function and vascular resistance, with the subject in the supine position and during head-up tilt, in order to examine the haemodynamic changes associated with alterations in the augmentation index, and to investigate repeatability and reproducibility of the measurement protocol.

MATERIAL AND METHODS

Thirty-three healthy volunteers (21-51 years) were investigated using continuous pulse wave analysis from the radial artery with a tonometric sensor, whole-body impedance cardiography and plethysmographic blood pressure (BP) recordings from the fingers. The measurements were performed with the subject supine and during passive head-up tilt, and repeated during the same session and on four separate days.

RESULTS

During the head-up tilt, diastolic BP (5.2+/-0.6%), heart rate (27.6+/-1.9%) and vascular resistance (12.5+/-1.7%) increased (all p<0.05), while systolic BP (-3.2+/-0.6%), aortic pulse pressure (-23.3+/-1.4%), augmentation index (-11.6+/-0.7%), aortic reflection time (-7.0+/-1.0%), ejection duration (-21.4+/-0.7%), stroke volume (-26.1+/-1.2%) and cardiac output (-5.0+/-1.5%) decreased (all p<0.05). Augmentation index at rest correlated with aortic systolic BP (r = 0.423), aortic reflection time (r = -0.647), pulse wave velocity (r = 0.287) and age (r = 0.480). The change in augmentation index during head-up tilt correlated with the change in aortic systolic BP (r = 0.469), aortic pulse pressure (r = 0.606), ejection duration (r = 0.374) and heart rate (r = -0.445). According to Bland-Altman and repeatability index analyses, repeatability and reproducibility of the measurements were good during the same session and on separate days.

CONCLUSIONS

Combined pulse wave analysis and impedance cardiography with the subject in the supine position and during head-up tilt is a repeatable and reproducible method for comprehensive investigation of the cardiovascular function.