Which apnea monitor uses electrical currents to obtain images of the lungs and can help determine PEEP levels?

• A. Respiratory inductance plethysmography
• B. Fiberoptic plethysmography
• C. Electrical impedance tomography
• D. Piezoelectric plethysmography

Answer: (C)

Electrical impedance tomography uses small electrical currents to image how air fills the lungs in real time. A belt with electrodes around the chest sends tiny alternating currents and measures the resulting voltages. Because air-filled lung tissue conducts electricity differently than fluid or tissue, changes in air content change the impedance, which the monitor translates into images showing regional ventilation. When titrating PEEP, you look for a setting that recruits collapsed areas without causing overdistension. EIT provides a visual map of how well each region is ventilated at different PEEP levels, helping you find the point where ventilation is most homogeneous across the lungs. Other monitors mainly track chest wall motion or airway or flow signals and do not produce imaging of regional lung aeration to guide PEEP, so they’re less capable of directly informing PEEP adjustments.