Multi-channel electrical bioimpedance: a non-invasive method to simultaneously measure cardiac output and individual arterial limb flow in patients with cardiovascular disease

Abstract

Cardiac output is the fundamental determinant of peripheral blood flow however; optimal regional tissue perfusion is ultimately dependant on the integrity of the arterial conduits that transport flow. A complete understanding of tissue perfusion requires knowledge of both cardiac and peripheral blood flow. Existing noninvasive devices do not simultaneously assess the cardiac and peripheral circulations. Multi-channel electrical bioimpedance (MEB) measures cardiac output and peripheral flow simultaneously. Assessment of the accuracy of MEB to measure cardiac output in patients with clinical heart failure (group 1) and to measure regional arterial limb flow in patients with exertional leg pain clinically thought to have peripheral arterial disease (group 2). Cardiac output was measured by MEB in 44 patients with moderate to severe clinical heart failure (group 1) and was compared to a cardiac output measured by 2D-Echo Doppler. Peripheral blood flow (regional ankle and arm flow) was measured by MEB in another group of 25 patients with exertional leg pain clinically thought to be claudication (group 2). The MEB ankle/arm flow ratio (AAI index) was then compared to a conventional ankle/brachial pressure ratio (ABI index). There was excellent correlation between the mean cardiac index by MEB (2.01 l/min/m(2)) and by 2D-Echo Doppler (2.06 l/min/m(2)) and bias and precision was 0.05 (2.4%) and +/-0.48 l/min/m(2) (+/-23%), respectively. The correlation was maintained for each measurement over a wide range of cardiac indices. There was good correlation between AAI and ABI measurements (P < 0.05). MEB accurately measures cardiac output in patients with moderate to severe clinical heart failure and accurately measures regional arterial limb flow in patients with peripheral arterial disease.