Pressure management
With the Agilia Connect portfolio of infusion devices there are two ways to manage pressure limits:
-
3 level mode
-
variable mode
Please note that the choice of using either the 3 level mode or the variable mode, is made by your hospital before we deliver the pumps. Once delivered your Profile within the pump will be locked to one of these modes and you will not be able to switch between them.
3 level mode
In 3 level mode, the pressure limit is adjustable according to three pre-set values specified in your Profile configuration.
Values for low, medium, and high must be specified in millimetres of mercury (mmHG) as per the following rules:
Low
Medium
High
between 50 and 300 mmHg
between 150 and 600 mmHg
between 250 and 750 mmHg
A difference of 100mmHg is required between any two levels.
When the dedicated pressure key is pressed the user will be able to choose between any of the three pre-set values configured for your Profile.
These pressure limits will apply to all drug protocols within your Profile unless a specific pressure limit has been set within an individual protocol. This may have been done for drugs or solutions that are thick or viscous where the pressure limit may have to be increased to reduce false occlusion alarms.
The "Current" pressure value displayed on the screen indicates the measured pressure level in the downstream portion of the infusion giving set.
Variable mode
In variable pressure mode, the limit is adjustable within a pre-defined range.
Values for default and a max hard limit must be specified in mmHg as per the following rules:
Default
Max hard
between 50 and 750 mmHg
between 300 and 750 mmHg
The default and max hard limits can be the same if required which would allow the user to only reduce the pressure limit if needed.
Again, when the dedicated pressure key is pressed the user will be able to change the pressure limit if required.
In variable pressure mode if the user does change the pressure limit then they will be unable to go above the max hard limit set for their profile but will be able to change the pressure limit anywhere between the max hard limit and the lower limit of 50 mmHg.
When changing the pressure limit in variable mode the values will increment, or decrement, in 25 mmHg intervals between 50 and 250 mmHg and in 50 mmHg intervals between 250 and 750 mmHg.
If variable pressure mode is enabled, a pre-alarm is triggered when the pressure reaches 50 mmHg below maximum pressure (25 mmHg when maximum pressure is set to 50 mmHg).
Occlusion alarm
When the pressure limit is reached, an occlusion alarm is triggered. You must silence the alarm, resolve the occlusion and start the infusion again.
When addressing or clearing an occlusion, ensure the fluid flow to the patient has been stopped by pressing the STOP key preventing administering an unintended bolus.
An occlusion may pressurise the administration set, which can result in an unintended bolus of a drug when the occlusion is cleared. To minimise this unintended bolus the Agilia Connect device will automatically initiate backflow pumping upon an occlusion alarm.
This backflow pumping helps to reduce any bolus volume at occlusion release to between -0.05 ≤ X ≤ 0.35 mL.
What pressure limit should I set?
If other pumps are used at the same time it is recommended that their pressure limits be adjusted to the same level.
The lower the occlusion pressure limit setting, the shorter the occlusion detection time. However, when infusing viscous or thick fluids (e.g. lipids), the occlusion pressure threshold setting may need to be increased to reduce false alarms.
To avoid the presence of air and minimise the amount of time it takes the pump to recognise an occlusion and generate an alarm while infusing at low rates (e.g. less than 5 mL per hour, and especially flow rates less than 0.5 mL per hour) consider your occlusion pressure threshold setting and adjust it as necessary.
The table below shows you how long the Agilia VP MC infusion pump will take to detect an occlusion depending on the flow rate and pressure limit set:
What happens if I am giving a bolus and it is stopped by an occlusion alarm?
This depends on the type of bolus being given.
If it is a direct bolus, which is when the device will only deliver a bolus when the user is physically holding the bolus button down if the device alarms for an occlusion the bolus will be stopped.
When the occlusion is cleared the bolus will not continue.
If it is a programmed bolus where the user has set the device to deliver a set bolus volume, let's say 10 mL in this example, then the device will again stop upon an occlusion being detected.
When the occlusion is cleared the user will be asked if they want to continue with the programmed bolus. If they say no then the bolus will stop. If they say yes then the programmed bolus will continue.
You may notice that the programmed bolus volume after an occlusion that still has to be delivered is higher than the remaining programmed bolus volume on the screen before the occlusion was detected.
This is related to an algorithm within the device mentioned earlier that will initiate backflow pumping to minimise any bolus volume at occlusion release.
As the device has performed this backflow pumping it will subtract the calculated backflow volume from the previously shown programmed bolus delivered volume and the new remaining programmed bolus to be infused volume will reflect this.
In some instances where the programmed bolus has been initiated and the device has alarmed almost immediately for an occlusion then you may find that the displayed remaining programmed bolus to be infused has returned to its starting value after the clearing of the occlusion.
After an occlusion, my volume infused has gone backwards. Why?
When the device detects an occlusion, it performs an automatic "back off" procedure.
This back off procedure causes the pump to reduce the current pressure measured back to 0 mmHg by pumping backwards.
As a result, the volume calculated by the back off procedure will be subtracted from the volume infused shown just before the occlusion happened.
This is done as a safety measure.
When an occlusion is detected, and an alarm sounds it is because the measured pressure has reached your set pressure limit. e.g. 700 mmHg.
The increase in pressure which triggered the occlusion alarm could result in a bolus of the drug being infused to the patient. The pump is designed to perform the back off procedure to minimise the post occlusion bolus release.
The volume subtracted from the volume infused shown just before the occlusion happened depends on various factors such as the length of the set, the diameter of the tubing and the set pressure limit.
This back off procedure helps to reduce any bolus volume at occlusion release to between -0.05 ≤ X ≤ 0.35 mL.
To discuss the back off feature in more detail please contact your local Fresenius Kabi Clinical Support Specialist or Account Manager.