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 900 mmHg
A difference of 100mmHg is required between any two levels.
When the menu key is pressed and the pressure option selected the user will be able to choose between any of the 3 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 syringe extension 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 900 mmHg
between 300 and 900 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 900 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 drug when the occlusion is cleared. To miminise this unintended bolus the Agilia Connect device will automatically initiate back flow pumping upon an occlusion alarm.
This back flow 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 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 SP PCA infusion pump will take to detect an occlusion depending on the flow rate and pressure limit set:
What happens to the pressure limit during a bolus?
During bolus administration (direct bolus or programmed bolus) the occlusion pressure is set to its maximum value of 900 mmHg, BUT this specification is valid only if the bolus rate is set above:
300 mL/hr for a 50/60mL syringe
240 mL/hr for a 30mL syringe
200 mL/hr for a 20mL syringe
120 mL/hr for a 10mL syringe
90 mL/hr for a 5mL syringe
If during bolus administration the bolus rate is set below the values above for each syringe size then the pressure limit will remain as currently set in either your Profile configuration or the individual protocol pressure setting if this has been configured.
As such, if you wish to minimise occlusion alarms during bolus administration and your bolus rates have been set to below the values detailed above then look to reduce the bolus rate, if possible, to reduce the pressure in the set. An alternative is to increase your pressure settings, if possible, to reduce the likelihood of the pressure limit being reached and an occlusion alarm happening.
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 and the mode in use.
PCA mode
In PCA mode the two bolus options are patient-initiated bolus using the bolus handset or Clinician bolus.
If it is a patient-initiated bolus which is interrupted partway through by an occlusion alarm then the device will stop and sound an alarm.
The nurse then needs to come to the pump, silence the alarm, clear any occlusion and will be given the option on the screen to continue with the rest of the patient-initiated bolus if required.
NOTE The patient cannot continue with the rest of the bolus they initiated by pressing the bolus handset. It can only be given from the pump directly by the nurse.
If a Clinician bolus is in the midst of being given and an occlusion alarm happens the same procedure as above applies. Once the alarm has been silenced and the occlusion cleared the nurse will be asked if they wish to continue with the remaining bolus or stop.
General mode (i.e. not a PCA mode)
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 backoff 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 backoff 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.
This increase in pressure resulting in the occlusion alarm could result in a bolus of the drug being infused to the patient to happen if the device does not perform the backoff procedure to minimise this 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 backoff procedure helps to reduce any bolus volume at occlusion release to between -0.05 ≤ X ≤ 0.35 mL.
To discuss the backoff feature in more detail please contact your local Fresenius Kabi Clinical Support Specialist or Account Manager.