Function Test of Baxter Colleague Infusion Pump Under
Hyperbaric Conditions
Stephen Goble
Hyperbaric Medicine Unit, Royal Adelaide Hospital
Objective:
To determine the suitability of the Baxter Colleague Infusion Pump for use under hyperbaric conditions by subjecting the pump to a number of tests under pressure in a hyperbaric chamber.
Modifications:
The following modifications were made to 2 pumps by the Biomedical Engineering Department to improve their suitability for use in the Hospital's hyperbaric chambers.
Both pumps had their keypads vented with a 0.65mm drill. This included areas on the decal that contained pockets of air, which may make contact while under pressure and affect its operation. The pumps did not contain any visible grease in their modules. The leads to the battery connector board were soldered and this board was secured to the battery terminals by insulating tape.
The motors in the pumps are self-contained units and would only contain a minimal amount of oil if any. The risk of combustion occurring at these sites was considered low and hence the motors were not dismantled
Measurement Method:
For the first test, measurements were made by measuring the amount of fluid infused in a measuring container. For better accuracy, subsequent test measurements were made by measuring and weighing the fluid. The fluid was weighed on an electronic Mettler PJ3000 laboratory scale which measures to 100 th of a gram. The empty receptacle was weighed before testing and its weight recorded, at the end of the test it was weighed containing the infused fluid and the initial weight taken from the result.
TEST 1: 2.8 Atmospheres Absolute (ATA)
The pump was subject to a 2.8ATA function test in an unmanned chamber.
Settings:
The pump was set at an infusion rate of 100ml/hr with a volume to be infused (VTB) of 100ml.
Method:
The pump and a time clock set to 1 hour were started simultaneously and the chamber was compressed to 2.8ATA. There were no changes noted and no alarms were activated. After 43 minutes decompression was commenced with the chamber arriving at 1ATA 59 minutes after the pump was started.
Result:
At exactly 1 hour the pump reverted to keep vein open (KVO) mode and according to its display had infused 100mls of fluid. The amount infused was measured and was exactly 100mls.
TEST 2: 2.0ATA
The pump was subjected to a standard 10.90.30 (2ATA) treatment table and parameters were changed during the time at pressure by a Registered Nurse attendant. This treatment involves compression to 2.0 ATA over approximately 6 minutes followed by a chamber pressure of 2.0 ATA for 90 minutes and then a linear decompression to 1ATA over 30minutes.
Settings:
Pre compression the pump was set at a rate of 100ml/hr with a VTB of 125ml.
Results:
At 65 minutes the pump read 104.1ml infused with 20.9 remaining and the amount infused was measured at 104.2ml, a discrepancy of +0.1%.
At this stage the pumps was stopped and reset to ensure that the pump's touch pad controls were able to function correctly while under pressure. There was some trouble restarting the pump, due to unfamiliarity with the panel lockout switch. The pump was reset to a rate of 20ml/hr and the VTB was left unchanged. During this last hour the chamber was decompressed over 30minutes to 1ATA.
After reaching 1ATA at 60minutes the pump reverted to KVO and displayed it had completed the 20ml, the amount infused was measured at 19.95ml, a discrepancy of -0.25%.
TEST 3: 6.0ATA
The pump was then subjected to a pressure test of 6ATA in a manned chamber.
Settings:
The pump was set at a rate of 1000ml/Hr with a VTB of 1000ml and was started immediately prior to starting compression.
Method:
Compression to 6ATA took 12 minutes and 4minutes were spent at 6ATA before decompression to 2.2ATA was commenced.
Results:
The pump was turned off after 41min 22seconds as it was out of fluid. It displayed 312ml remaining, meaning 688ml had been infused. Upon weighing, the amount infused was determined to be 660.8ml which is a 4% discrepancy of 27.2ml less than indicated by the amount infused display.
TEST 4: 1.0ATA
To determine if this discrepancy was due to the high infusion rate, the same settings were used to run the pump at 1ATA for the same amount of time.
Settings:
The pump was set at a rate of 1000ml/Hr with a VTB of 1000ml.
Result:
When the pump was stopped it read volume remaining 310ml, a volume infused of 690ml. On weighing the amount infused was determined to be 695.6ml which is a discrepancy of 0.8% greater than that indicated on the pump display.
TEST 5: 6.0ATA
Due to the Baxter's 4% discrepancy using high infusion rates at 6.0ATA it was decided to repeat the 6.0ATA test using smaller numbers and also to alter the rate at depth.
Method:
The dive profile used was; 11minute compression, 4 minutes at 6ATA, 6 minutes @2.2ATA, 6 minutes @ 1.9ATA, 8 minutes @ 1.6ATA and 25 minutes @ 1.3ATA.
Settings:
The pump was set at a rate of 125ml/hr with a VTB of 250mls. The pump was started at 1535 and at 1552 at a depth of 6.0ATA the rate was changed to 100mls/hr. The pump was turned off at 1647 after the chamber arrived back at surface.
Results:
At this time the pump read a VTB of 123 meaning 127 ml had been infused and the amount infused was measured at 128.05 ml, a discrepancy of +0.83%.
Conclusion:
Although Test 4 showed a 4% discrepancy while using very high flow rates at 6.0ATA it was confirmed through Biomedical Engineering that this is within normal limits. It was also felt that this test was not a sensitive indicator of pump performance, as the pump would not normally be operating at such high rates and volumes. The rest of the testing showed discrepancies within 1% and the pump operated very well under hyperbaric conditions.
As a result of this testing the Baxter Colleague infusion pump has been accepted into service at the Royal Adelaide Hospital Hyperbaric Medicine Unit.
DISCLAIMER:
Baxter Healthcare wish to advise that the testing we have undertaken is not an approved use of the Baxter Colleague Infusion Pump according to manufacturers' recommendations and they have no regulatory approval for the pump's use in Hyperbaric conditions.
POSTSCRIPT:
Since completing this testing we have been informed that there is a cold cathode fluorescent tube powered by a 260V AC inverter used to supply the backlight for the LCD display. This was missed by our Biomedical Engineers during the initial assessment. At the RAH we have decided to keep it in place, in Christchurch, New Zealand, they have elected to remove it. It is up to individual units to do a risk assessment and make up their own minds.
Contributing Author: Stephen John Goble
Steve
has held the position of head hyperbaric technical officer at Royal Adelaide
Hospital, in Adelaide, Australia, since 1985. He arrived in Adelaide by way
of the British Royal Navy (Clearance Diver) and the offshore commercial diving
industry. Steve is a founding member of the Hyperbaric Technicians and Nurses
Association (HTNA) and edits their journal (‘Offgassing’). Steve
is closely associated with, and intimately involved in, HIMS (Hyperbaric Incident
Monitoring Study), and is extensively published on topics ranging from technical
and safety issues, standards, incident reporting and decompression accidents.
