VOLUME OF EXTRAVASCULAR LUNG FLUID DETERMINED BY BLOOD ULTRASOUND VELOCITY AND ELECTRICAL-IMPEDANCE DILUTION

A hypertonic sodium chloride bolus passing through the lung has a soun d velocity transient that is biphasic when it reaches the carotid arte ry. This transient is compatible with water moving into the hypertonic bolus from the lung parenchyma, thereby leaving the lung parenchyma h ypertonic. Subsequently, as the bolus leaves the lung vasculature, wat er passes from the blood into the tissue to return the lung tonicity t o baseline, giving a moment when net movement is zero, an instant of o smotic equilibrium. Concurrent measurements of impedance track the sod ium chloride transient. A theoretic basis for the calculation of extra vascular lung water is derived from the water transferred to the blood , the amount of sodium chloride moved from blood to the lung, and the increase in blood osmolarity measured at the moment of equilibrium. Ex amples from measurements on sheep suggest that two intravenous injecti ons of hypertonic and isotonic sodium chloride, with observations of s ound velocity and electrical impedance in the systemic arterial circul ation (which could also provide the cardiac output), provide a basis f or calculation of lung permeability, water and salt movements, and ext ravascular lung water estimation.