Trigonometric Functions in My Heart: Modeling PPG Pulses with Basic Trigonometric Functions
Fingertip pulse oximeters are devices that provide important vascular and circulatory information. These devices are very cheap and do not require any special training to use them.Copyright 2011 UusiAjaja, Public Domain, Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Wrist-oximeter.jpg
Students learn that trigonometric functions can model how their hearts work and can provide important information about their cardiovascular condition. Students analyze their own photoplethysmogram (PPG) obtained from a fingertip pulse oximeter. Using a graphic user interface (GUI) developed in Microsoft Excel, students visualize a linear combination of sine functions to their PPG data. Once they obtain the best possible fit, students can use the GUI to determine important information about their hearts such as cardiac period and pulse interval.
Healthcare providers use sophisticated equipment for diagnostic, surgery or monitoring. From a simple digital thermometer to a bulky and expensive computed tomography scanner, these technologies are the result of the work of thousands of engineers applying physics and mathematics to develop precise health diagnostic and monitoring devices. Engineering design has made possible to have small equipment like pulse oximeters to monitor heart activity without putting a patient in a doctor’s office or a hospital. In this activity, students use a similar mathematical analysis to obtain information about their personal cardiovascular condition.
After this activity, students should be able to:
- Understand how a photoplethysmogram (PPG) analyzes and outputs information.
- Use a digital pulse oximeter.
- Identify important cardiovascular information contained in a PPG graph.
- Learn that a superposition of basic trigonometric functions like sines and cosines can be used to describe a more complex periodic function.