Figure 29.
Electrical impedance tomography (EIT) data obtained from the dorsal region of the dependent (A) and nondependent lungs (B) in a single subject. The relative impedance (rel. ΔZ) changes due to ventilation are greater than those associated with heartbeat which are seen during apnea. Changes in rel. ΔZ during breathing are great in the dependent than in the nondependent lung consistent with the gravitational gradient in regional specific ventilation (283). The decrease in EIT signal during breath holding is consistent with loss of gas volume consistent with ongoing gas exchange in the presence of a RER less than 1, such that less CO2 is produced than O2 is taken up. Reused, with permission, from Frerichs I, et al. 2017 (90).