Chapter 30
- Fundamental Principles of Monitoring Instrumentation
- James F. Szocik
- Steven J. Barker
- Kevin K. Tremper
Introduction
Patient monitoring has been a key aspect of anesthesiology since
its beginnings as a medical specialty. As anesthesiology has grown more sophisticated
and complex, so have the monitors and the data that they produce. The anesthesiologist's
senses of sight, hearing, and touch, at first expanded with the stethoscope, sphygmomanometer,
and electrocardiography, are now supplemented by the pulse oximeter, expired gas
analyzer, evoked potential monitor, and transesophageal echocardiograph, to name
a few. The complexity of some of these devices can be intimidating, and we are tempted
to regard them as incomprehensible "black boxes" that provide us with clinical data.
However, to do so would be to shirk an important part of our clinical responsibility.
We must be
able to not only understand and interpret the data from our monitors but also anticipate
and recognize errors associated with their use. We cannot accomplish this goal without
understanding how these devices work.
The purpose of this chapter is to provide an understanding of
the scientific principles underlying the design and function of our most commonly
used monitors. An introduction defining some concepts of basic physics is followed
by more detailed descriptions of the principles. The text and figures explain these
principles predominantly in a qualitative manner. For those desiring a more quantitative
explanation, the relevant equations are provided in the appendices to this chapter.
