Fluke Biomedical MPS450 - Manual (Page 35)

Cardiac Functions
Introduction
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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):
gje012.eps
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.