Introduction

Pulmonary Edema (PE) is a pathology involving the transfer of an excessive amount of watery fluids from the pulmonary capillaries to the pulmonary interstitium or into the alveoli due to a rise in the pulmonary interstitial fluid pressure from the negative to the positive range (Guyton AC 1991).

A major initiating mechanism for PE is Congestive Heart Failure (CHF).

“Even in severe CHF there are no agreed standard diagnostic criteria and no reliable methods for quantifying the associated pulmonary edema.” (Eur J Heart Failure 1999)

The periodic chest radiographs, most commonly used for assessing the patient condition, do not correlate directly to the edema severity, use ionizing radiation, cannot be used on a daily basis and are not practical outside the hospital settings.

“A method for both confirming the diagnosis and assessing the severity of pulmonary edema would be clinically useful.” (Eur J Heart Failure 1999)

The electrical properties of edemic lungs are considerably different from those of healthy lungs due to the change in the proportion of fluids and air, which is much higher in the former case. As lung fluids are characterized by a lower impedivity than air, monitoring the development of lungs' resistivity (measured in Ohms x cm) is expected to indicate their amount.