Fluke-biomedical MPS450 User Manual download pdf (Page 35)

Cardiac Functions

Introduction 2

2-3

Introduction

This chapter covers the MPS450 functions that are related to the heart: ECG, Arrhythmia,

ECG Testing, Blood Pressure, and Cardiac Output.

ECG Functions

An electrocardiogram (ECG) is a recording of the electrical activity of the muscles of the

heart—the depolarization and repolarization of the myocardium. Wires running from an

ECG machine are connected to small plastic or metal-terminated cables called leads, or

electrodes. Placed on the chest, on the wrists of the right and left arms, and on the left leg

at the ankle, the electrodes transmit signals to a pen that draws lines in the form of waves

onto graph paper in the ECG machine, tracing the heart's electrical activity (rate) and its

rhythm (beat). Each contraction of a normal heart causes a consistent waveform, referred

to as the P QRS T waveform, normal sinus rhythm, or NSR.

The MPS450 sets the simulated heartbeat to NSR, offering adjustable settings for heart

rate, amplitude, and ST measurement.

Normal Sinus Rhythm (NSR)

The NSR heartbeat, exhibiting the P-QRS-T wave, as defined in standard ECG textbooks:

When the heartbeat is normal, with a standard QRS waveform shape and height, it is

referred to as having a normal sinus rhythm. In normal sinus conditions, the SA

(sinoatrial) node—which lies just in front of the opening of the superior vena cava—

sends an electrical impulse through the nerves of the heart to the AV (atrioventricular)

node, through the bundle of His, down the left- and right-bundle branches, and on to the

fibers in the Purkinje network, where the impulse finally depolarizes in the ventricular

myocardium. At rest, the heart pumps an average of approximately two ounces (59 cc) of

blood per beat, or about five quarts per minute.

The MPS450 simulates NSR with a P-R interval of 0.16 seconds. Whenever the

instrument is turned on, the LCD screen displays the defaults (which remain active during

a session until the settings are changed) for heart rate (80 BPM), ECG amplitude on Lead

II (1.0 mV), and patient type (ADULT):

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Beats-per-minute, ECG amplitude, and patient type are adjustable. (Adjusting the BPM

rate does not affect simulations for arrhythmias, which set their own rates.)

Adjusting the ECG Heart Rate

The MPS450 offers seventeen preprogrammed settings (BPM) for heart rate: 30, 40, 45,

60, 80, 90, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, or 300.

Action in the Menu-Control Mode

1. Press the top-menu key labeled NSR. (The top-menu screen for normal sinus rhythm

displays automatically whenever the MPS450 is turned on.)

2. Select SEL to toggle to the screen for adjusting beats-per-minute (BPM/ampl), with

BPM in upper-case letters.

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Fluke-biomedical MPS450 User Manual Page 35