Impact of Heart Rate on Ventilation and Pulmonary Perfusion Associated Impedance Changes

Abstract

The potential of electrical impedance tomography (EIT) to assess perfusion changes in the lung has already been demonstrated in several studies. Methods like frequency domain filtering, principal component analysis or breath holding have been introduced. Since EIT is noninvasive and radiation-free, it depicts a promising supplement to current methods such as single photon emission computed tomography. In our study we investigated ventilation and pulmonary perfusion associated impedance changes as a function of heart rate in four healthy spontaneously breathing subjects. EIT measurements were conducted during physical exercises on a bicycle ergometer to get various heart rates. EIT data were acquired at three to four different heart rates in the 3^rd and 5^th intercostal space (ICS), respectively. Spirometry was performed simultaneously to determine tidal ventilation. A Fast Fourier Transform and frequency domain filtering were applied to separate ventilation from pulmonary perfusion signals. Ratios of ventilation and pulmonary perfusion related impedance changes ∆I_V/∆I_Q were calculated in a predefined region of interest within the different thorax planes. All subjects showed a higher gain in ∆I_V/∆I_Q dependent on heart rate in the 3^rd ICS than in the 5^th ICS. It was observed that in all subjects pulmonary perfusion associated impedance amplitudes increased stronger in the 5^th ICS compared to the 3^rd ICS. Minute volumes determined by spirometry (MV_spiro) featured similar trends like minute variations calculated with ventilation related impedance amplitudes (MV_EIT). EIT measurements could reliable conducted on spontaneously breathing subjects during physical exercises. Separation of ventilation and pulmonary perfusion associated impedance changes was successfully achieved by frequency domain filtering within the different thorax planes for all subjects.

The original version of this chapter was inadvertently published with an incorrect chapter pagination 1264–1269 and DOI 10.1007/978-3-319-32703-7_242. The page range and the DOI has been re-assigned. The correct page range is 1270–1275 and the DOI is 10.1007/978-3-319-32703-7_243. The erratum to this chapter is available at DOI: 10.1007/978-3-319-32703-7_260

An erratum to this chapter can be found at http://dx.doi.org/10.1007/978-3-319-32703-7_260