Thoracic Impedance Gradient with Respect to Breathing

Validation of the thoracic impedance derived respiratory signal using multilevel analysis

“…This suggests that the thoracic impedance signal obtained from four spot electrodes does not substantially differ from the thoracic impedance signal obtained from tetrapolar circum-ferential mylar-band electrodes. In support of this, Khalafalla et al (1970) directly compared the thoracic impedance respiratory signal obtained from pairs of spot electrodes with spirometric values and found an almost linear relationship between changes in the thoracic impedance using spot electrodes and changes in lung volume.…”

Impedance pneumography: Noise as signal in impedance cardiography

“…The present study builds on earlier research that documented the linearity between lung volume and transthoracic impedance, and explored the impact of alternative electrode configurations e.g., Allison et al, 1964;Baker et al, 1966;Khalafalla et al, 1970;Kubicek et al, 1964!. Results demonstrate that standard tetrapolar band electrodes can provide viable respiratory monitoring in psychophysiological studies, over a wide range of respiratory amplitudes and frequencies. Although the linearity of the impedance-lung volume relation may break down at respiratory extremes~peak inspiration and forced expiration; Allison et al, 1964!, the respiratory signal was captured accurately over a range of inspiratory volumes and frequencies representative of those ranges likely encountered in psychophysiological studies.…”

“…Previous research has found that the electrode configuration can impact on the amplitude of the impedance pneumographic signal~Baker et al, 1966;Khalafalla et al, 1970;Kubicek et al, 1964! reported that sagittal placements of spot electrodes gave larger impedance changes than other configurations, such as the common cardiography spot-electrode arrangement that has been used in psychophysiological studies~Sherwood, Royal, Hutcheson, & Turner, 1992!.…”

“…An alternative impedance pneumographic approach was developed by early physiologists, based on the relatively linear changes in thoracic impedance observed with changes in lung volumẽ Allison, Holmes & Nyboer, 1964;Baker, Geddes, Hoff, & Chaput, 1966;Khalafalla, Stackhouse, & Schmitt, 1970;Kubicek, Kinnen & Edin, 1964!. With the increasing application of impedance cardiography in psychophysiological studies, this approach may be particularly useful if relevant respiratory measures could be derived from standard thoracic impedance signals. Although respiratory-related changes in thoracic impedance are recognized in impedance cardiography, they have been considered a source of noise to be extracted or otherwise dealt with~Kelsey & Guethlein, 1990;Sherwood et al, 1990!.…”

“…This advantage is particularly important for phase-sensitive comparisons such as crosscorrelational analyses or the peak-to-trough method of deriving RSA~Grossman, van Beek, & Wientjes, 1990!. Further, there appears to be minimal between-subjects variability in the gain relationship between impedance and respiration, as subject-to-subject variability does not appear to be appreciably greater than withinsubject variance~see also Khalafalla et al, 1970!. Consequently, even without calibration, impedance values can be used to quantify relative respiratory parameters across subjects.…”