Apparatuses and methods for determining lung wetness

A non-invasive patch sensor, the patch sensor comprising:

• a substrate;
• a plurality of electrodes on the substrate, wherein the substrate maintains a predetermined spacing between the electrodes;
• and
• a plurality of alignment tabs extending from a lateral side of the substrate wherein the alignment tabs are between about 0.2 inches (0.5 cm) and about 2 inches (5 cm) long and greater than about 0.1 inches (0.3 cm) wide,
• wherein the plurality of electrodes are configured to form a plurality of pairs of current-injecting electrodes and a plurality of pairs of voltage detection electrodes.

A method of determining tissue wetness, the method comprising:

• attaching a patch sensor comprising a plurality of drive electrodes and sensing electrodes to a skin surface of a subject's body;
• measuring a curvature of the skin surface of the subject's body;
• applying drive currents at a plurality of different frequencies to the drive electrodes and measuring voltages at a plurality of different sensing electrodes;
• determining an estimate of electrical properties for a plurality of regions beneath the patch sensor using the applied drive currents and measured voltages;
• and
• determining an estimate of tissue wetness from a frequency response of the determined electrical properties.