Chapter 1 Patient monitoring syste1.docx

IT IS A TECHNICAL MANUAL FOR BMET

1. Chapter 1 Patient monitoring system
Duration: 6hrs
Chapter description
This chapter discuss the working principle, purpose, main components and them
Functions, troubleshooting techniques, maintenance, safety procedures and job aid
for Patient Monitoring Device.
Chapter objective: By the end of this session, the participants will be able to:
Explain the use and importance of patient monitor as well as to perform proper safety and
care, preventive maintenance, and corrective maintenance on patient monitoring device
Enabling objectives:
By the end of this chapter the participants will be able to:
Describe the clinical uses and importance of patient monitoring device
Explain the working principle and main parts of patient monitoring device
Apply and perform safe handling
Exercise basic preventive and corrective maintenance procedure of patient
monitoring
Chapter Outline
1.1Introduction to Patient monitor
1.2Working principle
1.3Basic Parts /Components and Functions
1.4Safety and care
1.5 Preventive maintenance
1.6Troubleshooting techniques and repair
1.7Summary

2. 1.1 Introduction to patient monitor
Activity 1: Individual reflection
What is patient monitoring and define its purpose and clinical application?
Time: 5mins
Patient Monitoring Device is a critical medical instrument designed to continuously or
periodically track, measure, and display a patient's vital physiological signs such as body
temperature, heart rate (pulse), respiratory rate, blood pressure (NIBP, IBP), oxygen
saturation. It functions as an electronic sentinel, providing clinicians with real-time data and
immediate alerts to swiftly identify life-threatening changes in a patient's condition. In essence,
these devices extend the senses of the healthcare team, enabling constant vigilance over a
patient's stability.
The fundamental purpose of patient monitoring is to move from intermittent, manual checks
to continuous, automated surveillance.
Monitoring is therefore a tool that provides early indication of changing patient status, and
allows for early intervention, but is also a means by which the effect of interventions and
therapies may be recorded, evaluated and controlled.
This is paramount in clinical environments where a patient's status can deteriorate rapidly and
without warning, such as in Intensive Care Units (ICUs), Neonatal ICUs (NICUs), Operating
Rooms (OR), and Emergency Departments
1.2 Working Principle of Patient Monitoring Device
A patient monitoring system operates on the principle of translating physiological phenomena
from the patient into intelligible data for clinical assessment. This process is achieved through
three sequential stages: Acquisition, Processing, and Output.
1. Acquisition (Signal Detection)
Specialized sensors, or transducers, are attached to the patient to detect specific physiological
signals and convert them into analog electrical signals.
Bioelectric Potential: Measured by electrodes to capture the heart's electrical activity
(ECG).
Photoplethysmography: A pulse oximeter probe uses red and infrared light to measure
blood oxygen saturation (SpO ) based on the differential light absorption of oxygenated
₂
and deoxygenated hemoglobin.
Oscillometry: An inflatable cuff detects pressure oscillations in an artery to determine
systolic, diastolic, and mean arterial pressure (NIBP).
Transthoracic Impedance: Electrodes measure the cyclical change in electrical
impedance across the chest cavity to derive respiratory rate.

3. Thermoelectric Effect: A thermistor probe measures temperature-dependent changes in
electrical resistance.
2. Processing (Signal Conditioning & Digitization)
The raw, weak, and noisy analog signals are conditioned and converted for digital analysis.
Amplification: The signal's amplitude is increased to a usable level.
Filtering: Electronic filters remove artifacts and interference (e.g., power line noise,
motion artifact).
Analog-to-Digital Conversion (ADC): The conditioned analog signal is sampled at a
high frequency and converted into a discrete digital data stream.
Algorithmic Analysis: Software algorithms analyze the digital data to extract parameters
(e.g., identifying QRS complexes for heart rate, analyzing pulse waveforms for SpO ).
₂
3. Output (Data Presentation & Alarming)
The processed information is presented to the clinician and used for automatic vigilance.
Display: Data is displayed numerically (e.g., HR: 75) and graphically as real-time,
scrolling waveforms (e.g., ECG trace).
Notification: Pre-set high and low limits for each parameter are continuously compared
to the real-time data. If a value breaches a limit, the system triggers visual and audible
alarms to alert clinical staff.
In essence, the system functions as a continuous data pipeline: Physiological Event →
Transduction → Signal Conditioning → Digital Analysis → Clinical Information.

4. 1.3 Basic Parts/Components and functions of
Patient Monitoring System
External parts and their function
Part Function
1. Main Display Screen
The primary interface that shows waveforms, numerical values, and alarm
messages.
2. Control Buttons / TouchscreenAllows user input for navigation, changing settings, and silencing alarms.
3. Parameter-Specific Ports
Connectors for patient cables and sensors (e.g., ECG, SpO , NIBP,
₂
Temperature).
4. Power Button & Indicator Switches the monitor on/off and shows power status.
5. Alarm Silence & Pause Buttons
Temporarily silences an active alarm or pauses alarm sounds for a short
period.
6. NIBP Start/Stop Button Manually initiates or stops a blood pressure measurement.
7. Handle For safely transporting the monitor.
8. Power Inlet & Cable Connects the monitor to AC mains power for operation and battery charging.
9. Battery Provides backup power for operation during transport or a power outage.
10. Data Ports
(e.g., USB, Network) For data export, software updates, and connection to
central stations.

5. Internal Parts & Their Functions
These are the core electronic subsystems inside the monitor's chassis.
Part Function
1. Power Supply Unit (PSU)
Converts AC mains power to stable, low-voltage DC power required by all internal
circuits. Provides electrical isolation for patient safety.
2. Mainboard / Motherboard
The central nervous system. Houses the CPU and manages data flow between
all other modules and components.
3. Parameter Modules

Specialized circuit boards that process specific signals:
- ECG Module: Amplifies, filters, and analyzes the electrical signal from
electrodes to calculate heart rate and detect arrhythmias.
- SpO Module:
₂
 Drives the sensor's LEDs, processes the light absorption
signal, and calculates oxygen saturation and pulse rate.
- NIBP Module: Controls the air pump and valves, analyzes pressure
oscillations in the cuff to determine blood pressure.
- Temperature Module: Measures the resistance from the temperature probe
and converts it to a temperature reading.
4. Digital Signal Processor
(DSP)
A specialized microprocessor that performs high-speed mathematical
calculations for real-time waveform analysis and parameter extraction.
5. Alarm System (Speaker &
Lights)
Generates audible tones and controls visual indicator lights to alert staff based
on signals from the processing modules.
6. Backlight Inverter/LED
Driver
Provides the power to illuminate the LCD/LED display screen.

6. Figure
1.2
Front
view of patient monitor
Figure
1.3
Left
and
Right
Side
View
of
Monitor

7. 1.3.1 Power unit
The Power Supply Unit provides regulated electrical power to all components of the patient
monitoring system. It converts high-voltage Alternating Current from a wall outlet into the low-
voltage Direct Current required by the device's internal electronics. This conversion is achieved
through a transformer, a rectifier, and voltage regulation circuits. A built-in, rechargeable battery
is maintained by this unit as a backup power source. In the event of an AC mains power failure,
the system automatically and seamlessly switches to battery power. This ensures the continuous
and uninterrupted operation of the patient monitor.
Figure 1.4 power supply
1.3.2 ECG measuring electrodes
The heart's electrical activity, which precedes its mechanical contraction, generates ionic currents.
These currents conduct through body tissues to the skin, creating potential differences between different
points on the body. An electrocardiogram (ECG) is the recording of these changing potential differences
over time, resulting in a dynamic waveform. A diagnostic 12-lead ECG provides a detailed view for
comprehensive analysis. In contrast, patient monitors typically use fewer leads (3 or 5) for continuous,
real-time tracking of heart rate and rhythm. These monitoring systems use simplified electrodes and
cables designed for rapid application and long-term reliability in a clinical setting.

8. Figure 1.5 ECG measuring electrode
1.3.3 Respiration Measurement via Impedance
Thoracic impedance respiration measurement uses ECG electrodes to pass a high-frequency, low-
amperage current across the chest. The impedance of the thoracic cavity cyclically changes with
inhalation and exhalation, and the monitor calculates the respiration rate from these variations.
ECG/RESP Processing Module
This dedicated microcontroller, featuring a high-speed Digital Signal Processor (DSP), performs the
following core functions:
It acquires the analog signals from the patient electrodes.
It converts these signals to digital format and processes them to filter noise.
The DSP analyzes the digital data to detect the QRS complex for heart rate calculation and the impedance
cycle for respiration rate.
Finally, it outputs the calculated rates and waveforms to the system's display for clinical viewing.
Figure 1. module and PCB
kit
1.3.4 SPO2
measuring transducer
The SPO2 processing module is found inside the mother board of the
patient monitoring system. It is a microcontroller with a very high-speed
Digital signal processing (DSP) IC chip which is programmed to perform a
specific application. This module:

9. Accepts analog signal from SPO2 measuring transducer,
Converts the analog signal to digital signal,
Process the digital signal
Use various filters and signal correlation techniques to extract
useful information from the SPo2 pulse waveform signals
Record the extracted blood oxygen saturation and carbon dioxide level
Display the result on the monitor
1.3.5 Temperature probes
This probe is a sensor that detects the temperature of the patient ‘s body by
using thermistor, a resistor whose resistance value varies with temperature.
The temperature range in which the sensors can detects generally varies
from device to device.

10. 1.3.6 Temperature module
This module is a Digital signal processing (DSP) IC chip which is found in
the mother board of the patient monitoring device. The module:
Accepts analog signal from the temperature sensors,
Converts the analog signal to digital signal
1.3.7 NIBP and IBP measuring transducers
NIBP/IBP Processing Module This specialized module on the monitor's mainboard uses a high-
speed Digital Signal Processor (DSP) to manage blood pressure measurements.
NIBP (Non-Invasive) Function:
Uses the oscillometric method during cuff deflation
Estimates systolic, diastolic, and mean pressures by analyzing pressure oscillations
Automatically inflates/deflates with safety limits:
oAdult: 315±10 mmHg
oChild: 255±10 mmHg
oNeonate: 170±10 mmHg
Maximum inflation time: 90 seconds
Provides measurement failure alerts
IBP (Invasive) Function:
Directly measures blood pressure via fluid-coupled catheter
Provides continuous real-time pressure waveform
Includes user interface for parameter selection and zeroing
The module automatically handles multiple measurement attempts and supports all standard cuff
sizes.

11. 1.4 Safe and care Procedure
Assume All Equipment is Contaminated: This is the default mindset before handling any
patient-returned monitor.
Hand Hygiene
Perform Hand Hygiene Immediately AFTER removing gloves following
decontamination or handling contaminated equipment.
Wash hands with soap and water or use an alcohol-based hand rub before moving to
the bench repair or testing phase.
Make hand hygiene a deliberate step when transitioning from a "dirty"
(decontamination) area to a "clean" (test bench) work area.
Minimum PPE for Decontamination:
Wear Nitrile Gloves to protect from bloodborne pathogens and harsh disinfectants.
Wear a Lab Coat or Gown to prevent contamination of personal clothing.
Electrical Safety: Inspect the power cord and patient cables regularly for damage to prevent
electric shock or fire hazards.
Proper Placement: Ensure the monitor is securely positioned on a stable stand to prevent it
from falling.
Cleaning & Disinfection: Clean the monitor and its sensors with manufacturer-approved
disinfectants after each use to prevent cross-contamination.
Secure Connections: Verify all patient cables and electrodes are firmly connected to ensure
accurate readings and avoid alarm fatigue.
Alarm Management: Set appropriate patient-specific alarm limits and ensure the volume is
audible to enable timely clinical response.
Infection Prevention & Control (IPC) Focus
Decontaminate on Arrival: Clean the entire external surface of the monitor with
a hospital-approved disinfectant (e.g., 70% IPA wipes, hydrogen peroxide wipes) as
the first step in the workflow.
Focus on High-Touch/High-Risk Areas:
oMonitor casing, screen, and all control buttons.
oEntire length of all patient cables (ECG, SpO , NIBP, temp).
₂
oCable connectors and ports on the monitor.
1.5Preventive maintenance
Frequency Maintenance Tasks
Daily (By - Wipe down exterior surfaces with approved disinfectant.

12. Frequency Maintenance Tasks
Clinical Staff) - Visually inspect cables and connectors for obvious damage.
Weekly
- Perform a full functional test using a patient simulator (ECG, SpO , NIBP).
₂
- Check battery status and run-time.
Monthly
- Perform detailed visual inspection of all patient cables for fraying, cracking, or pin
corrosion.
- Clean air filters and vents to prevent overheating.
Quarterly /
Bi-Annually
- Perform full performance verification and calibration using a multi-parameter
simulator.
- Conduct complete electrical safety tests (Ground Resistance, Leakage Current).
Annually
- Open chassis (by trained BMET) and remove internal dust with compressed air.
- Check for bulging capacitors or signs of component stress on PCBs.
- Update firmware as per manufacturer's recommendations.

13. 1.6 troubleshooting, maintenance and repair
Prepare:
Appropriate PPE (personal protective equipment)
Cleaning material
Multimeter to check electrical parameters
Mechanical and electrical tool kits to trouble shoot
Service manual
Checklists to check qualitative and quantitative data
Blower to remove dusts on the interior and exterior part of the device
Physical inspection:
Smell for burning cables and components
Hearing for abnormal noise
Looking at physical breakage of system components
Inspect cables
Performance check and verification
Pre-Test Setup & Safety
oBegin by decontaminating the monitor and donning appropriate PPE.
oVerify all test equipment (simulators, analyzers) are within their calibration
period.
Electrical Safety Analysis
oUtilize an Electrical Safety Analyzer to perform mandatory tests per NFPA 99
and IEC 60601-1.
oDocument results for protective earth resistance, enclosure leakage current, and
patient lead leakage current.
ECG & Arrhythmia Analysis
oConnect a multi-parameter patient simulator to the monitor's ECG leads.
oVerify heart rate accuracy from bradycardia to tachycardia ranges (e.g., 30 to 300
BPM).
oTest the monitor's arrhythmia detection by simulating life-threatening rhythms
like V-Fib and Asystole to confirm proper alarm generation.
Non-Invasive Blood Pressure (NIBP) Validation
oUse the simulator's dynamic NIBP function to test systolic/diastolic accuracy
across pressures (e.g., 80/50, 120/80, 200/150 mmHg).
oEmploy a static pressure manometer to verify the monitor's transducer accuracy
and check for system leaks.

14. Pulse Oximetry (SpO ) Performance
₂
oConnect a dedicated SpO simulator
₂
 to the monitor's sensor port.
oValidate saturation accuracy at critical levels (70%, 85%, 97%) and pulse rate
correlation.
oTest the monitor's response to low-perfusion and motion artifact simulations.
Invasive Pressure (IBP) Module Calibration
oConnect an IBP simulator to the pressure module.
oPerform a zero calibration and verify static pressure accuracy across the clinical
range (-50 to 300 mmHg).
Temperature & Respiration Verification
oUse a temperature simulator or precision resistors to validate probe accuracy.
oTest impedance-based respiration monitoring using the ECG simulator's
respiration function.
Alarm System Stress Test
oMethodically use the simulator to trigger every parameter-specific alarm.
oVerify both audible and visual alarms are distinct, unambiguous, and function at
all priority levels.
Data & Documentation
oRecord all "as-found" and "as-left" data in your CMMS.
oAffix a dated calibration sticker and update the device's service history.

15. Corrective Maintenance
Activity 1.4: Group
Arrange yourself in Power unit repair
a group where each group can have a maximum of five persons. Then within your group perform a
troubleshooting activity on the system components of a patient monitoring device. After finishing the
troubleshooting identify the system failures/problems (if there is any) of the device.
Time: 80 min
Symptom /
Problem
Probable Cause Troubleshooting & Corrective Actions
1. No Power / Will
Not Turn On
- Faulty power outlet
- Damaged power cable
- Blown internal fuse
- Failed Power Supply Unit
(PSU)
1. Verify: Test outlet with another device.
2. Check: Inspect power cable for damage; test continuity.
3. Inspect: Check and replace blown fuses on PSU/mainboard.
4. Test: Use a multimeter to check for DC output voltages from the PSU.
Replace PSU if faulty.
2.Intermittent
Power / Random
Shutdowns
- Loose internal power
connections
- Failing backup battery
- Overheating due to clogged air
vents
1. Inspect: Open chassis and reseat all power connectors.
2. Test & Replace: Test battery voltage under load; replace if it cannot
hold a charge.
3. Clean: Use compressed air to clear dust from vents, fans, and internal
components.
3.No ECG
Waveform / Poor
Signal
- Dry or disconnected
electrodes
- Broken or frayed ECG patient
cable
- Poor skin preparation
- 50/60 Hz electrical
interference
1. Replace: Apply new, fresh electrodes.
2. Inspect & Test: Check cable for breaks; test continuity. Replace if
faulty.
3. Prepare Skin: Clean and gently abrade skin for better contact.
4. Eliminate Interference: Ensure monitor is properly grounded. Check
for broken Right-Leg-Drive (RLD) circuit. Keep cables away from
power cords.

16. Symptom /
Problem
Probable Cause Troubleshooting & Corrective Actions
4. SpO not
₂
reading / No Pulse
- Poor perfusion (cold patient,
low BP)
- Incorrect sensor placement
- Damaged SpO sensor or cable
₂
- Ambient light interference
1. Reposition: Try a different site (other hand, foot). Warm the
extremity.
2. Reapply: Ensure sensor is snug and aligned (LED opposite
photodetector).
3. Replace Sensor: If cracked or damaged. Test with a known-good
sensor.
4. Shield: Cover the sensor with an opaque material to block ambient
light.
5. NIBP
Error / No
Reading
- Air leak in tubing or
cuff
- Kinked or obstructed
tubing
- Incorrect cuff size
- Patient movement
during measurement
1. Leak Test: Inflate cuff manually and listen/observe for leaks. Replace
faulty components.
2. Inspect: Check entire air path for kinks or blockages.
3. Select Cuff: Ensure cuff width is ~40% of limb circumference.
4. Retry: Ensure patient is still and initiate a new measurement.
6. NIBP Over-
inflates / Fails
to Deflate
- Stuck or faulty deflate
valve
- Occluded pressure vent
tube
- Faulty pressure
transducer
1. Listen: You should hear a click from the solenoid valve during
deflation. If not, replace the valve assembly.
2. Inspect: Check for blockages in the air path.
3. Calibrate/Replace: Use a pressure meter to test transducer accuracy.
Replace if out of specification.
7. No
Temperature
Reading
- Disconnected or
damaged temp probe
- Failed temperature
module
1. Inspect & Test: Check probe for damage. Test probe resistance with a
multimeter (should be in the kΩ range).
2. Replace: Swap with a known-good probe. If problem persists, the
temperature input circuit on the mainboard is likely faulty.
8. False or
Persistent
Alarms
- Incorrect alarm limits
set
- Sensor/Probe
disconnection
- Low battery warning
- Software glitch
1. Verify Limits: Check and adjust alarm limits for the specific patient.
2. Check Connections: Ensure all sensors are properly connected to the
patient and monitor.
3. Address Power: Connect to AC power or replace battery.
4. Reboot: Perform a power cycle. If persistent, check for firmware
updates.

17. 1.6summary
Patient Monitoring devices are used to monitor patient ‘s physiological parameters
such as Electrocardiogram (ECG), respiration rate (RESP), blood oxygen and carbon
dioxide saturation level (SPO2 and CO2), non-invasive and invasive blood pressure
(NIBP and IBP), and temperature (TEMP)continuously in a dynamic and long-time
range.
Patient safety and infection prevention is a must to follow.
Patient monitoring systems detects/sense, transduce, process, record and display the
various physiological parameters of the patient.
Troubleshooting is a form of problem-solving technique, often applied to repair failed
products or processes of a system or a device following different steps we can
troubleshoot patient monitor machines.
Professionals should follow different steps to perform both preventive and
corrective maintenance on patient monitor machines