10.3 – Patient Monitors

Introduction to Patient Monitors

Patient (physiologic) monitors can be both wired or wireless depending upon their need. We will begin with the wired monitors. Continuous monitoring is a valuable tool that helps provide additional information to the medical and nursing staff about the physiologic condition of the patient. Using this information, the clinical staff can better evaluate a patient’s condition and make appropriate treatment decisions.  These systems usually include a central station monitor that receives, consolidates, and displays the information and a set of monitors that are deployed near the patient (bedside monitors) to provide the required data from each patient (ECG, respiratory rate, noninvasive blood pressure (NIBP) and invasive blood pressure (IBP) (systolic, diastolic, and mean), body temperature, (SpO2), mixed venous oxygenation (SvO2), cardiac output, (ETCO2), intracranial pressure, and airway gas concentrations). See Video 10.3.1 for an overview of these metrics on a patient monitor.

Patient monitors can be configured, modular, or both. Configured monitors have all their capabilities already built-in. Modular systems feature individual modules for each monitoring parameter or group of parameters; these modules can be used in any combination with each bedside monitor or be interchanged from monitor to monitor. Some devices have the capabilities of both modular and configured systems. Many physiologic monitoring systems include a central station capable of displaying ECG waveforms and other information from any bedside within the system, and many are equipped with alarms that are coordinated with those at the bedside monitor.

Poor electrode preparation and attachment are most commonly reported. Cables and lead wires should be periodically inspected for breaks and cracks. Loss of patient alarms, misleading alarms,
and parameter errors have been the causes of most monitor recalls. Even monitors that are functioning reliably cannot substitute for frequent direct observation. Many devices
produce frequent “false alarms” which can lead to alarm fatigue and missed critical events.

Wireless or Telemetric monitors designed for continuous measurement and transmission of several vital physiologic parameters to a central station or a bedside monitor. These monitors typically consist of transmitters and electrodes, an antenna system or access points, receivers, and a display screen and recorder. Telemetry systems transmit physiologic parameters like ECG, NIBP, SpO2. Telemetric monitoring systems transmit patients’ physiologic parameters to a central station display and/or a bedside monitor. Data transfer is done to a remote location by means of radio waves. Because they use radio-wave transmission, cables are not required to connect the patient and transmitter to the display monitor, thereby allowing greater patient mobility.

The frequency bands used by wireless medical telemetry are getting crowded, putting medical telemetry at risk for interference. Signal fading, during which the ECG signal is momentarily lost, results in inaccurate ECG signals, false alarms, and monitoring data loss. To reduce the potential of interference from noise, hospitals should survey the installation site to ensure that the antennae are properly placed, that no other equipment operates at that frequency, and that no outside interference impede telemetry signals.

Watch

Video: Introduction to patient monitors

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Troubleshooting Monitors

There are many different types of physiologic monitors; however, the troubleshooting and maintenance procedures remain relatively similar. Below is a following example of the inspection an preventative maintenance procedures for an electrocardiogram monitor.

1. Inspect exterior of equipment for damage or missing hardware.
2. Inspect the power cord, strain relief and plug/s for any signs of damage.
3. Turn unit off, open user-accessible covers and inspect unit for damage.
4. Clean unit interior components and exterior with vacuum or compressed air.
5. Inspect interior for signs of corrosion or missing hardware. Repair as required.
6. Inspect electrical components for signs of excessive heat or deterioration.
7. Inspect patient cable and connectors for mechanical or electrical damage.
8. Verify correct detenting and lead shorting of lead selector switch.
9. Verify vertical gain and calibration pulse. Inspect monitor/diagnostic switch.
10. Verify correct sweep size, linearity, centring, speed and vertical spacing.
11. Verify correct amplifier frequency response and common mode rejection.
12. Verify correct brightness and focus of trace.
13. Verify correct operation of freeze and cascade controls if applicable.
14. Verify accuracy of heart rate meter at 3 points for ±3% accuracy.
15. Verify operation of high and low alarms for correct trigger and response time.
16. Cycle alarms and verify correct operation of audio and visual indicators.
17. Verify correct operation of all buttons, controls, displays and/or indicators.
18. Verify correct operation of unit in all functional modalities.
19. Clean exterior of unit including all accessories, cables, controls and displays.