The cardiac monitor displays cardiovascular waveforms and measurements at a patient's bedside. It continuously monitors the electrocardiogram and can also show oxygen saturation, blood pressure, and other parameters. Electrodes are attached to the patient's skin to detect electrical signals. The monitor allows for prompt treatment in response to any changes outside normal ranges. It is commonly used in emergency rooms and critical care units to continuously observe multiple patients.

1. Cardiac Monitoring

2. Cardiac Monitoring
The cardiac monitor is a device that shows the
electrical and pressure waveforms of the
cardiovascular system for measurement and
treatment. Because electrical connections are
made between the cardiac monitor and the
patient, it is kept at the patient's bedside.

3. .
Purpose
• The cardiac monitor continuously displays the cardiac
electrocardiogram (EKG) tracing. Additional monitoring
components allow cardiovascular pressures and cardiac
output to be monitored and displayed as required for
patient diagnosis and treatment.
• Oxygen saturation can also be monitored continuously.
• Most commonly used in emergency rooms and critical
care areas, bedside monitors can be interconnected to
allow for continual observation of several patients from a
central display.
• Continuous cardiovascular and pulmonary monitoring
allows for prompt identification and initiation of
treatment.

4. .
Description
The monitor provides a visual display of many patient
parameters. It can be set to sound an alarm if any
parameter changes outside of an expected range
determined by the physician.
Parameters to be monitored may include, but are not
limited to, electrocardiogram, noninvasive blood pressure,
intravascular pressures, cardiac output, arterial blood
oxygen saturation, and blood temperature.

5. Physiological basis of cardiac monitoring
• Preload
• Afterload
• Contractility

6. Types of cardiovascular monitoring equipment
All the monitoring systems comprise the same key elements,
➢ A sensor to detect the signal
➢ A transducer to convert the signal into an electrical form
➢ A monitor which displays and records the signal.
Cardiovascular monitoring,
❖Electrocardiogram
❖Arterial blood pressure
❖Central venous pressure
❖Left atrial pressure (PA wedge pressure)
❖Pulmonary artery pressures
❖Cardiac output

7. .
Respiratory system,
• Oxygen saturation
• Blood gases
Renal system,
• Urinary output
• Blood pH and acid-base status.

8. Preparation of patient
• The sites selected for electrode placement on the skin
will be shaved and cleaned causing surface abrasion for
better contact between the skin and electrode. The
electrode will have a layer of gel protected by a film,
which is removed prior to placing the electrode to the
skin.
• Electrode patches will be placed near or on the right arm,
right leg, left arm, left leg, and the center left side of the
chest. The cable will be connected to the electrode
patches for the measurement of a five-lead
electrocardiogram. Additional configurations are referred
to as three-lead and 12-lead electrocardiograms.

9. .
• If noninvasive blood pressure is being measured, a
blood pressure cuff will be placed around the patient's
arm or leg. The blood pressure cuff will be set to inflate
manually or automatically. If manual inflation is chosen,
the cuff will only inflate at the prompting of the health
care provider, after which a blood pressure will be
displayed. During automatic operation, the blood
pressure cuff will inflate at timed intervals and the
display will update at the end of each measurement.
• The arterial blood saturation probe will be placed on the
finger, toe, ear, or nasal septum of the patient.
• A 12 lead ECG recording will be obtained pre-
operatively in any patient with suspected cardiac
disease.

10. Lead Positions
The ECG may be used in two ways.
• A 12 lead ECG may be performed which analyses the
cardiac electrical activity from a number of electrodes
positioned on the limbs and across the chest. A wide
range of abnormalities may be detected.
• During anaesthesia, the ECG is monitored using only
3 (or occasionally 5) electrodes which provide a more
restricted analysis of the cardiac electrical activity
and cannot provide the same amount of information
that may be revealed by the 12 lead ECG.

11. 12-Lead Placement
• Limbs leads placed at
least 10 cm from heart.
• Chest leads must be
placed exactly.
Lead Location View
V1 4th intercostal space, right sternal border Ventricular septum
V2 4th intercostal space, left sternal border Ventricular septum
V3 Between V2 and V4 Anterior wall of left ventricle
V4 5th intercostal space, midclavicular line Anterior wall of left ventricle
V5 Lateral to V4 at anterior axillary line Lateral wall of left ventricle
V6 Lateral to V5 at midaxillary line Lateral wall of left ventricle

12. . During anaesthesia one of 3 possible 'leads' is
generally used. These leads are called bipolar leads as
they measure the potential difference (electrical
difference) between two electrodes. Electrical activity
travelling towards an electrode is displayed as a positive
(upward) deflection on the screen, and electrical activity
travelling away as a negative (downward) deflection.
• Lead I - measures the potential difference between the
right arm electrode and the left arm electrode. The third
electrode (left leg) acts as neutral.
• Lead II - measures the potential difference between the
right arm and left leg electrode.
• Lead III - measures the potential difference between the
left arm and left leg electrode.

13. .

14. Connecting an ECG monitor
• Electrodes attached in a variety of positions, conventionally they
are placed in a standard position each time so that abnormalities
are easier to detect. Most monitors have 3 leads and they are
connected as follows:
• Red - RA - right arm, (or second intercostal space on the right of
the sternum)
• Yellow - LA - left arm (or second intercostal space on the left of
the sternum)
• Green (or Black) - LL - left leg (or more often in the region of the
apex beat.)
• The cables from the electrodes usually terminate in a single cable,
which is plugged into the port on the ECG monitor. A good
electrical connection between the patient and the electrodes is
required to minimize the resistance of the skin. For this reason gel
pads are used to connect the electrodes to the patients skin.

15. Principles of the ECG
• The ECG is a recording of the electrical
activity of the heart. An electrical recording
made from one myocardial muscle cell will
record an action potential (the electrical
activity which occurs when the cell is
stimulated). The ECG records the vector sum
(the combination of all electrical signals) of
all the action potentials of the myocardium
and produces a combined trace.
• At rest the potential difference across the
membrane of a myocardial cell is -90mv. This
is due to a high intracellular potassium
concentration, which is maintained by the
sodium/potassium pump.

16. .
• Depolarization of a cardiac cell occurs when there
is a sudden change in the permeability of the
membrane to sodium. Sodium floods into the cell
and the negative resting voltage is lost. Calcium
follows the sodium through the slower calcium
channels resulting in binding between the
intracellular proteins action and myosin which
results in contraction of the muscle fibre. The
depolarization of a myocardial cell causes the
depolarization of adjacent cells and in the normal
heart the depolarization of the entire myocardium
follows in a co-ordinated fashion. During
repolarisation potassium moves out of the cells and
the resting negative membrane potential is
restored.

17. Formation of the ECG (1 of 4)

18. Formation of the ECG (2 of 4)

19. Formation of the ECG (3 of 4)

20. Formation of the ECG (4 of 4)

21. The Conducting System of the Heart
Conducting tissue is made up of modified
cardiac muscle cells which have the property
of automaticity, that is they can generate their
own intrinsic action potentials (nerve
impulses) as well as responding to stimulation
from adjacent cells. The conducting pathways
within the heart are responsible for the
organized spread of action potentials within
the heart and the resulting co-ordinated
contraction of both atria and ventricles.

22. .

23. .

24. Graphical recording on a paper trace,

25. .
• The ECG is usually recorded on a time scale of 0.04
seconds/mm on the horizontal axis and a voltage sensitivity
of 0.1mv/mm on the vertical axis. Therefore, on standard
ECG recording paper, 1 small square represents 0.04seconds
and one large square 0.2 seconds.
• In the normal ECG waveform the P wave represents atrial
depolarisation, the QRS complex ventricular depolarisation
and the T wave ventricular repolarisation.
• The P - R Interval is taken from the start of the P wave to the
start of the QRS complex. The Q - T interval is taken from
the start of the QRS complex to the end of the T wave. This
represents the time taken to depolarise and repolarise the
ventricles. The S - T segment is the period between the end
of the QRS complex and the start of the T wave. All cells are
normally depolarised during this phase.

26. .
ECG Normal Values
• P - R interval 0.12 - 0.2 seconds (3-5 small
squares of standard ECG paper)
• QRS complex duration less than or equal to
0.1 seconds (2.5 small squares)
• Q - T interval corrected for heart rate (QTc)
QTc = QT/ RR interval less than or equal to
0.44 seconds

27. .

28. .
After care
• After connecting all equipment, the health care provider will
observe the monitor and evaluate the quality of the tracings,
while making size and position adjustments as needed.
• The provider will confirm that the monitor is detecting each
heartbeat by taking an apical pulse and comparing the pulse
to the digital display. The upper and lower alarm limits
should be set according to physician orders, and the alarm
activated.
• A printout may be recorded for the medical record and
labeled with patient name, room number, date, time, and
interpretation of the strip.
• Maintenance and replacement of the disposable components
may be necessary as frequently as every eight hours.
• The arterial saturation probe can be repositioned to suit
patient comfort and to obtain a tracing.
• All connections will be treated in a gentle manner to avoid
disruption of the signal and to avoid injury to the patient.

29. .
Normal results
• The monitor will provide waveforms and/or numeric values
associated with the patient status. These may include, but
are not limited to, heart rate, arterial blood pressure, central
venous pressure, pulmonary artery pressure, pulmonary
capillary wedge pressure, left atrial pressure, cardiac output,
arterial blood saturation, and blood temperature.
Furthermore, these values can be used to calculate other
values used to diagnose and treat the patient's condition.
• Patient movement may cause measurement errors; the
patient will be requested to remain motionless.
• As the patient's condition improves, the amount of
monitoring equipment may be decreased. However, the
electrocardiogram and arterial blood saturation probe
should be expect to remain attached until discharge is
imminent.

30. Modes of cardiac monitoring
Modern ECG monitors have electronic filters to decrease
environmental artifacts. They usually can operate in two
modes, each with a different frequency response.
• The monitoring mode (0.5 to 40 Hz) eliminates both
low and high frequency artifacts such as wandering
baseline but also distorts the height of the QRS complex
and the degree of ST-segment depression or elevation.
The monitor mode may not accurately display ECG
changes.
• The diagnostic mode (0.05 to 100 Hz) does not filter
the highet-frequency signals but is more subject to
artifact. The ECG in diagnostic mode will reflect
abnormal (i.e., ischemic) changes accurately.

31. .

32. .

33. Problems with cardiac monitoring
• Problems with the trace
• Incorrect heart rate display
• Wandering baseline
• Artifacts and interference
• Low voltage ECGs
• Inappropriate setting of the gain control