Christian Tronstad, Jan Olav Høgetveit, Ole Elvebakk and Håvard Kalvøy
Impedance cardiography (ICG) is a non-invasive method of hemodynamic measurement, mostly known for estimation of stroke volume and cardiac output based on characteristic features of the signal. Compared with electrocardiography, the knowledge on the morphology of the ICG signal is scarce, especially with respect to age-dependent changes in ICG waveforms. Based on recordings from ten younger (20–29 years) and ten older (60–79) healthy human subjects after three different levels of physical activity, the typical interbeat ICG waveforms were derived based on ensemble averages. Comparison of these waveforms between the age groups indicates the following differences: a later initial upward deflection for the younger group, an additional hump in the waveform from many older subjects not presented in the younger group, and a more pronounced second wave in the younger group. The explanation for these differences is not clear, but may be related to arterial stiffness. Further studies are suggested to determine whether these morphological differences have clinical value.
Jan-Hugo Andersen, Olav Bjerke, Fatos Blakaj, Vilde Moe Flugsrud, Fredrik Alstad Jacobsen, Marius Jonsson, Eirik Nobuki Kosaka, Petter André Langstrand, Øyvind Grannes Martinsen, Alexander Stene Moen, Emily Qing Zang Moen, Øyvind Knutsen Nystad, Eline Olesen, Mahum Qureshi, Victor Jose Østrem Risopatron, Simen Kristoffer Ruud, Nikolai Stensø, Fredrik Lindseth Winje, Eirik Vetle Winness, Sisay Abie, Vegard Munkeby Joten, Christian Tronstad, Ole Elvebakk and Ørjan Grøttem Martinsen
Sixteen volunteers each drank 700 ml sugar-containing soft drink during two successive periods and the blood sugar was measured at 10 min intervals together with electrical impedance spectroscopy and near infrared spectroscopy (NIR). A maximum correlation of 0.46 was found for the electrical measurements but no clear separation between low and high blood glucose levels were found in the NIR measurements. The latter was attributed to the experimental design where the NIR probe was removed from the skin between each measurement.