Acoustical assessment of body water balance

Abstract

A new medical application of acoustics has recently emerged: assessment of body hydration status by ultrasonic measurement of muscle water content. The need for an easy-to-perform method for the detection of water imbalance is of the utmost clinical importance. Body hypohydration may cause severe health and performance problems, decreasing cognitive and physical work capabilities, while excessive hydration is a common symptom of many other diseases. The speed of longitudinal acoustic waves in muscle, as well as in other soft tissues, is defined by tissue molecular composition because both the density and bulk compressibility of tissue depend mainly on short range molecular interactions. Skeletal muscle is the largest water compartment in the body; it comprises 40% of body mass and 75% of muscle is water. The ultrasound velocity in muscle is a linear function of water content with the slope of about 3.0 m/s per 1% change in water content. We will describe the design, measurement principles, and testing results for new acoustic devices for assessment of hydration status of elderly and infants, two most vulnerable groups of population. Advantages and disadvantages of acoustical method of hydration over currently available methods are discussed.