Preventative Maintenance Tips for Anesthesia Unit Ventilators

Procedure

Before beginning preventative maintenance inspection, carefully read the manufacturer’s instruction and service manuals. Preventative maintenance varies with different models as well as different manufacturer's. It is wise to be sure that you understand how to operate the equipment and the significance of each control/indicator. Also determine whether any special inspection or preventative maintenance procedures or frequencies are recommended by the manufacturer. It is VITAL to identify the type and/or application of the aspirator to be inspected in order to define the performance criteria for the inspection. This is often difficult because most devices bear only a model or catalog number. Obtain this information from the manufacturer’s literature, previous inspection forms, or clinical personnel. Once the type of aspirator has been identified or when new units are purchased, enter  this information on the equipment control or inventory record so that it can be determined quickly from the control number on the device in future inspections.

Qualitative Test Tips

• Chassis/ Housing - Examine the exterior of the unit for cleanliness and general physical condition. Be sure that housings are intact, that all assembly hardware is present and tight, and that there are no signs of spilled liquids or other abuse.
• Mount - If the device is mounted on a stand or cart, examine the condition of the mount.
• Casters/ Brakes - If the device moves on casters, check their condition. Look for accumulations of lint and thread around the casters, and be sure that they both turn and swivel, as appropriate. Check the operation of brakes and swivel locks, if the unit is so equipped.
• AC Plug - Examine the AC power plug for dam-age. Attempt to wiggle the blades to determine that they are secure. Shake the plug and listen for rattles that could indicate loose screws.
• 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. Also check line cords of battery chargers. 
• Circuit Breaker/ Fuse - If the device has a switch-type 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 fuse is provided.
• Filters - Check the condition of all liquid and pneumatic (air) filters.
• Battery/ Charger - Inspect the physical condition of batteries and battery connectors, if readily accessible. Check operation of battery-operated power-loss alarms, if so equipped. Operate the unit on battery power for several minutes to check that the battery is charged and can hold a charge. Check remaining battery capacity by activating the battery test function or measuring the output voltage. Check the condition of the battery charger and, to the extent possible, confirm that it does, in fact, charge the battery. When it is necessary to replace a battery, label it with the date.
• Labeling - Check that all necessary placards, labels, conversion charts, and instruction cards are present and legible.

Quantitative Test Tips

• Grounding Resistance - Using an ohmmeter, electrical safety analyzer, or multi meter 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 of 0.5?.
• Leakage Current - Measure chassis leakage cur-rent to ground with the grounding conductor of plug-connected equipment temporarily opened. Record the maximum leakage current with the unit off and on. Leakage current should not exceed 300µ.
• Maximum Flow - Measure the maximum free airflow with the flow meter and compare it with recommended values in the table.Set the unit for maximum suction. Test the aspirator with the collection bottle(s) or canister(s) in place, but without patient catheters. Use a short piece of large-diameter tubing from the flow meter to the device, with the correct size adapters inserted at the aspirator end. Any restrictions will tend to reduce the free airflow.
• Rate of Vacuum Rise - This test is necessary only on tracheal, emergency, and intrauterine aspirators, where rapid vacuum rise is essential. Connect the vacuum gauge or pressure meter to one side of a T fitting and attach the T to the canister or collection bottle patient connector. Turn the unit on and set the unit for maximum suction. Occlude the open port of the T with a finger while using a stopwatch or watch with a second hand to measure the time required to reach maximum vacuum. 
• Maximum Vacuum - Connect the vacuum gauge or pressure meter to the canister or collection bottle patient connector. Turn on the aspirator, adjust it to provide maximum vacuum, and record this value. If a unit does not provide the expected maximum vacuum (see the Aspirator Performance Values table above), look for air leaks, especially in the collection bottle caps and hoses. Some low-volume aspirators have “low” and “high” settings; record the vacuum attained for each, measuring the low level first. Thermal intermittent aspirators do not reach maximum vacuum during the first few cycles, and it is necessary to wait 5 to 10 min until maximum vacuum isreached.
• Vacuum Gauge Accuracy - Check the accuracy of the vacuum gauges on units so equipped at a vacuum level typical for primary usage. To make this measurement, connect the vacuum gauge or pressure meter to the fitting on the collection bottle intended for the patient catheter or tubing. Turn the unit on and adjust it to the desired vacuum reading on the machine’s gauge. Record this reading and that of the test gauge or meter. Readings should be within 10%.

Finally, do not forget to clean the exterior and interior, and lubricate the motor/pump, if needed. Replace filter(s), hoses/tubing, fittings/connectors, if required.