1. Electrocardiography Heart Sounds Blood Pressure
BIOL 204 – Week 5 Lab
Electrocardiography
Heart Sounds
Blood Pressure

2. Objective ECG
An electrocardiogram is a graphical recording of the hearts electrical changes during a cardiac cycle (heart beat)
- Electrical changes initiated and propagated through the myocardium by specialized cells of the heart’s intrinsic conduction system
Structures of the Intrinsic Conduction Voltage changes seen System

3. The voltage changes are recorded by leads which can be placed in different locations on the body
We will use limb leads, placed on the appendages 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 LA - . LL also records electrical activity spreading from the base to the apex, but from a different orientation

4. 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

5. A typical ECG tracing

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

7. 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

8. In this exercise you will evaluate a baseline ECG, and then identify and discuss changes in the ECG after a period of rest and exercise.
Lab 6 activities will provide data for your formal lab report.
You will test the effects of 2 variables on BP and HR
The 2 variables are: Exercise and Postural changes.

10. Objective 2 Heart Sounds
In this lab activity you will record the ECG and heart sounds from a subject and, with the aid of an electronic stethoscope, hear those characteristic sounds of the heartbeat, typically described as a "lub-dub."
Equipment Required
PC Computer
IWX/214 data acquisition unit
USB cable
IWX/214 power supply
C-AAMI-504 ECG cable and electrode lead wires
ES-100 electronic stethoscope
Alcohol swabs; Disposable ECG electrodes

12. Objective 3 Arterial Blood Pressure

13. Measuring Blood Pressure
– Tips
– Inflating the blood pressure cuff
–interpreting the values