Preventative Maintenance Tips for Blood Pressure Monitors (Invasive)
Posted: April 30, 2013
Blood pressure monitors (Invasive) are most commonly used in special care units, emergency departments, operating rooms, cardiac catheterization laboratories; often included as a component of physiological monitoring systems.
Monitoring blood pressure, in addition to the electrocardiograph, provides a more comprehensive view of cardiovascular status than can be attained by the ECG alone. However, invasive blood pressure monitoring requires a significant amount more skill and involves a much greater risk. Blood pressure monitors are used to monitor systolic, diastolic, or mean arterial pressures, central venous pressures, and pulmonary artery wedge pressures.
As is the case with all medical equipment, it is extremely important that you maintain your blood pressure monitor. Routine preventative maintenance will not only prolong the life of your machine, but it will also ensure better quality monitoring on the whole.
Below, you will find a list of PM tips for your blood pressure monitor. Please remember to read the manufacturer’s instruction and service manuals. Often times each manufacturer has a specific set of guidelines that differ from one another.
- Chassis/Housing: Examine the exterior of the unit for cleanliness and general physical condition. Be sure that plastic housings are intact, that necessary assembly hardware is present and tight, and that there are no signs of spilled liquids or other serious abuse.
- Mount: If the device is mounted on a stand or cart, examine the condition of the mount. If it is attached to a wall or rests on a shelf, check the security of this attachment.
- AC Plug: Examine the AC power plug for damage. Attempt to wiggle the blades to determine that they are secure. Shake the plug and listen for rattles that could indicate loose screws. If any damage is suspected, open the plug and inspect it.
- Line Cord: Inspect the cord for signs of damage. If damaged, replace the entire cord or, if the damage is near one end, cut out the defective portion. Be sure to wire a new power cord or plug with the same polarity as the old one.
- Strain Reliefs: Examine the strain reliefs at both ends of the line cord. Be sure that they hold the cord securely.
- Circuit Breaker/Fuse: If the device has a switchtype circuit breaker, check that it moves freely. If the device is protected by an external fuse, check its value and type against that marked on the chassis, and ensure that a spare is provided.
- Cables: Inspect the cables and their strain reliefs for general condition. Examine cables carefully to detect breaks in the insulation and to ensure that they are gripped securely in the connectors of each end to prevent rotation or other strain.
- Fittings/Connectors: Verify that the connector for the transducer cable is secure, clean, and lacks any signs of damage.
- Transducers: If they are normally stored with the unit, confirm that transducers are on hand, and check their physical condition.
- Controls/Switches: Before moving any controls and alarm limits, check their positions. If any of them appear inordinate, consider the possibility of inappropriate clinical use or of incipient device failure. Record the settings of those controls that should be returned to their original positions following the inspection.Examine all controls and switches for physical condition, secure mounting, and correct motion. Where a control should operate against fixed limit stops, check for proper alignment, as well as positive stopping. Check membrane switches for membrane damage. During the course of the inspection, be sure to check that each control and switch performs its proper function.
- Indicators/Displays: During the inspection, confirm the operation of all lights, indicators, meters, gauges, and visual displays. Be sure that all segments of the digital display function.
- User Calibration: Verify that the zero-adjustment and any calibration controls function properly. Zero the monitor with a transducer or transducer simulator attached, making sure that the zero adjustment is not at an extreme setting. Confirm that the calibration function operates and that the calibration or gain adjustment, if user adjustable, provides an adequate range on both sides of the correct adjustment point. Some monitors have a calibration resistor inside the transducer cable connector. With such units, the monitor’s calibration function will not operate with a transducer simulator, which does not usually include this calibration resistor. Use the transducer intended for use with the monitor for this test.
- Alarms: Operate the device in such a way as to activate each audible and visual alarm. If the monitor has an alarm-silence feature, check the method of reset against the manufacturer’s specifications. Although it may not be possible to verify the operation of all alarms at this time it is important to understand all of the alarm capabilities and remember to check them at the appropriate time during the procedure.
- Pressure Modes: Verify that the monitor correctly indicates systolic, diastolic, and mean arterial pressures by switching the transducer simulator between two pressure settings and noting that the indicated pressure in the systolic mode is highest, the mean pressure lower, and the diastolic pressure lowest. The pulse pressure, if available, should be the difference between the systolic and diastolic pressures.Because some monitors do not compute the true mean, the indicated mean value may vary depending on the waveform and monitor used.
- Grounding Resistance: Using an ohmmeter, electrical safety analyzer, or multimeter with good resolution of fractional ohms, measure and record the resistance between the grounding pin of the power cord and exposed metal on the chassis. We recommend a maximum resistance of 0.5 ?. If the system is modular, verify grounding of the mainframe and each module. If the device has an accessory outlet, check its grounding to the main power cord.
- Leakage Current: Measure the leakage current from the monitor chassis with the grounding conductor temporarily opened. Check the monitor while on and off and record the maximum leakage current. Chassis leakage current to ground should not exceed 300 µA.
- Accuracy, High Pressure Range: This test checks the monitor’s accuracy and linearity. The most convenient method for testing the monitor’s accuracy is with a transducer simulator that contains a resistive network. Plug the transducer simulator into the monitor and zero it. Test pressures are 100 mm Hg and maximum for the systolic, diastolic, and mean arterial modes. Normally, the monitor will read approximately the same in each mode. Record values from only one mode and indicate on the form which mode was recorded. When using a pressure simulator, the pressure monitor should measure to within 2% of a given static pressure. Although considerably less convenient, an accurate pressure transducer, a 0 to 300 mm Hg pressure gauge or meter, a sphygmomanometer squeeze bulb, a Y connector, and tubing may be substituted for the transducer simulator. Connect the stem of the Y connector to the transducer and the Y connector arms to the sphygmomanometer squeeze bulb and pressure gauge. The monitor should be zeroed as it normally is during clinical use. Be sure that the dome is properly attached to the transducer, especially if a disposable dome is used. Test the monitor as described previously. The overall accuracy of the transducer monitor system should be within 5% of a given static pressure. If the error is excessive, determine whether it is introduced by the transducer, monitor, or both by using another transducer to test the monitor or another monitor to test the transducer.
- Accuracy, Low Pressure Range: Repeat the pressure accuracy test, as described in Item 2.10, for the venous and pulmonary ranges. Be sure the monitor is accurately zeroed in each range before taking measurements. Suggested test pressures are 10 mm Hg and maximum. Accuracy should be within 1 mm Hg if a blood pressure transducer is used or 2 mm Hg if a transducer is used.
- Alarm Accuracy: Set the alarm at appropriate low and high settings, and test for the actual alarm values by varying the applied or simulated pressure. Record the actual values on the form. Alternatively, set appropriate applied or simulated pressures and raise and lower the high and low alarm settings, respectively, until the alarm activates. The unit should alarm within 5% of the set value. Many monitors have an alarm delay, which must be taken into account when conducting this test. If the alarm delay is excessive, compare it to the manufacturer’s specification and arrange for adjustment or repair, if appropriate.
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