LEARNING OBJECTIVES

After reading this chapter, you should:

• Describe the common components of a measurement system.

• Understand the different types of sensors and the mechanism by which each converts its detected signals into electrical signals.

• Describe the principle of operation of instruments used to monitor patient body temperature, blood pressure, oxygen saturation, cardiac function, and blood glucose levels.

• Describe the principle of operation of instruments used in the laboratory such as a pH meter and spectrophotometer.

• Understand the importance of the emerging areas of biosensors and microelectromechanical systems (MEMS).

Prelude

Modern health care has benefited enormously from the work of biomedical engineers to create instruments that are used in clinical monitoring and laboratory analysis. Hospital operating rooms, emergency rooms, and doctors' offices each contain an array of instruments used to measure and record a patient's vital signs such as temperature, blood pressure, pulse, and oxygen saturation (Figure 11.1). Many of the most popular instruments enable non-invasive monitoring of vital signs of patient health: The stethoscope allows doctors to listen reliably to the beating heart, the sphygmomanometer allows them to estimate pressure within vessels deep in the body (Figure 11.2), and the ophthalmoscope allows them to see structures on the retina. It is impossible to estimate the number of lives that have been lengthened or improved by these devices.

The medical device industry—the constellation of large and small companies that design, manufacture, and sell medical devices and instruments—is one of the largest and most rapidly growing sectors of the U.S. economy.