Electrocardiography Introduction to Iworx BIOL 204 – Week 5 Lab Electrocardiography Introduction to Iworx SB

Objective 1 ECG An electrocardiogram is a graphical recording of the hearts electrical changes during a cardiac cycle (heart beat). This animation shows how your heart pumps blood. Electrical changes are initiated and propagated through the myocardium by specialized cells of the heart’s intrinsic conduction system. Structures of the Intrinsic Conduction System Voltage changes seen

We will use limb leads to record ECGs in this lab The voltage changes are recorded by leads which can be placed in different locations on the body We will use limb leads to record ECGs in this lab Lead 1: RA -, LA + most sensitive to electrical activity spreading horizontally across the heart Lead 2 RA -, LL + most sensitive to electrical activity spreading vertically (from the base to the apex) Lead 3 LA - . LL + also records electrical activity spreading from the base to the apex, but from a different orientation LA RA RL LL

When an ECG tracing is recorded using these lead combinations, a series of wave forms are generated which respond to the spread of electricity through the heart after it originates at the SA node

A typical ECG tracing

Y (vertical) axis measure voltage 10 squares = 1 mV X axis measures time At a chart speed of 25 mm/sec.: each small block = 0.04 sec. each large block = 5 small blocks 5 X 0.04 sec. = 0.20 sec. 5 large blocks = 1 sec. Y X

To determine the heart rate from an ECG tracing:                                                                       Method #1: count the number of small squares from one R wave to the next R wave and divide that number into 1500 Heart Rate (bpm) = 1500/#small squares Method #2 locate an R wave on a bold line and identify the next R wave: HR = 72 bpm HR = 37 bpm

When performing an ECG, remember: In this exercise you will evaluate a baseline ECG, and then identify and discuss changes in the ECG after a period of exercise and after a period of breath holding When performing an ECG, remember: The leads are labeled to tell you where they should be placed Any movement of skeletal muscle will affect the reading, including talking and laughing Take readings quickly after the subject exercises – have a person hold the leads and be ready to reattach them right away Use the Manual Print button and print enough squares for each member of your group

Objective 2 Arterial Blood Pressure Video showing how to take blood pressure

How to Take Blood Pressure (3 parts, ad at beginning) Tips for Taking Blood Pressure Inflating a Blood Pressure Cuff Taking the Blood Pressure When taking blood pressures, remember: Subject’s arm must be bent and level with heart Inflate no higher than 150 mmHg, release slowly Do not inflate for more than 1 minute or take more than 3 readings from the same arm!

Objective 3: Introduction to Iworx This tutorial describes how to adjust the LabScribe software so that signals are sized and displayed properly. It also describes how to make simple measurements from recordings. In this activity, you will be familiarizing yourself with the Iworx hardware and the operation of the LabScribe software. All aspects of the program that would be used in other Iworx activities are covered. At the end of the activity : you should be able to load the appropriate lab setting group function to open the lab exercise and software 2. You should be able to use the software to move cursors, analyze data, record data to the journal, and use functions in the analysis window to determine values for pulse amplitude and heart rate.

Front Panel of IWorx 214 Rear Panel of IWorx 214

Equipment Required PC Computer IWX/214 data acquisition unit USB cable IWX/214 power supply PT-104 pulse plethysmograph

Sample of how a recording would look like: