The Science Journal of the American Association for Respiratory Care

2001 OPEN FORUM Abstracts

Evaluationof Vacuum Outlet Performance

Mark Siobal BS RRT,Roger Kraemer CRT, Respiratory Care Services, San Francisco General Hospital, UCSFDept. of Anesthesia.

Background: Hospitalvacuum system performance is dependent on the function of a duplex of two ormore vacuum pumps which alternately or simultaneously supply vacuum on demand.Functional maintenance of vacuum systems is focused toward maintaining vacuumpressure via vacuum pump maintenance and repairing leaks. The performance ofindividual vacuum outlets, in regards to suction effectiveness, is dependenton the flow rate through the outlet at any given vacuum pressure. Flow ratethrough a suction outlet is limited by the resistance across the outlet valve.Following observations of inefficient vacuum outlet performance in the intensivecare unit with closed tracheal suction catheter use, vacuum outlet flow rateswere measured to determine the extent of the problem.

Methods: A threadedvacuum outlet nut with a 1/4 inch barbed nipple was attached via a one footlength of suction tubing to the outlet end of a Boehringer handheld spirometerusing a 22 mm OD, 15 mm ID adapter and a 5.0 mm endotracheal tube connector.The vacuum outlet nut was attached directly to the vacuum outlet on the wallpanel until the outlet check valve was fully opened. The volume of air in litersaspirated through the vacuum outlet was measured on the Boehringer spirometerfor 15 - 30 seconds. The flow rate through the outlet was calculated in litersper minute. The measurement was repeated three times for each outlet and theresults were averaged. A total of 52 vacuum outlets in 18 intensive care unitrooms were assessed. The results were reported to hospital engineering. Themeasurements were repeated four months later following cleaning and replacementof component parts in the vacuum outlet check valves.

Results: Themedian and mean ± standard deviation of vacuum outlet flow rates pre and postmaintenance were 48 and 47 ± 21 L/min, and 86 and 82 ± 14 L/min respectively.Vacuum outlet flow rate markedly improved following maintenance in all but oneoutlet. Vacuum outlet flow rates of ³ 60 L/min were determined to be functionallyadequate. The initial measurements revealed that prior to maintenance 63% ofthe vacuum outlets performed below this threshold vs 6% following cleaning andreplacement of parts.

Conclusions:Based on our experience we recommend that preventative maintenance of vacuumoutlets occur on a regular basis with specific focus on maintaining functionallyadequate flow rates (³ 60 L/min). Preventative maintenance should include cleaningand or replacement of component parts. Maintenance of adequate vacuum outletflow rates may also impact the user perception of the effectiveness of closedtracheal suction catheters.


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