3.6 Ventilator Alarms
Every ventilator has alarms that are set for the safety of the patient. We have talked a lot about the danger of applying pressure to the fragile alveoli. Using alarms on the ventilator will make sure that the pressures and volumes stay in safe ranges. After setting up your patient and initiating ventilation with your settings, go into your alarm screen and ensure your alarms are appropriate to your settings and patient.
The standard alarms that are set for all ventilation modes are as follows:
|
Type of Alarm |
Alert |
Significance |
|---|---|---|
| Input Alarms | Loss of electric power | Activated when the power supply is interrupted while the ventilator is on |
|
Loss of pneumatic power
|
Activated when either the O2 or air supply pressure is reduced below a specified point
|
|
| Control Alarms |
The set parameters are incompatible
|
Activated when operator makes errors in set up
|
|
Part of the self-test failed
|
Activated during self test prior to initiating ventilation: Ex. Leak in the circuit, or failed flow sensor calibration
|
|
|
There is something wrong with the ventilator control circuitry
|
Activated when ventilator microprocessor fails to function (usually alarms “vent inop”)
|
|
| Output Alarms |
Volume Alarms
|
High and Low Expired Tidal Volume
|
|
Flow Alarms
|
High and Low Expired Minute Volume
|
|
| Time Alarms |
High and Low Ventilatory Frequency
|
|
|
Inappropriate Inspiratory Time
|
||
|
Inappropriate Expiratory Time
|
||
| Pressure Alarms |
High and Low Peak Airway Pressure
|
|
|
High and Low Mean Airway Pressure
|
||
|
High and Low Baseline Pressure
|
It is important that you ensure your alarms are adequately set for all patients. Do not set your alarms too close to what your normal numbers are. These alarms are your safety net that your patient will not be exposed to volutrauma or barotrauma, but if your alarm ranges are set too tightly, it could cause any patient movement or change to trigger an alarm. Frequent alarms are disturbing for patients as well as the clinician. We also know that if things are alarming too often, it can cause alarm fatigue in healthcare workers and sometimes important alarms can be overlooked. Suggested ranges for alarm settings are below, but always defer to your health centre’s guidance when it differs from these recommendations:
| Alarm | Suggested Setting | Rationale |
|---|---|---|
| High RR | [latex]30\text{ - }35\text{ bpm}[/latex] | Patient can wake up or rouse from sedation and increase their RR. This alarm is mostly used for spontaneous modes |
| High Pressure | [latex]35\text{ cmH}_2\text{O (max)}[/latex] or [latex]+10\text{ cmH}_2\text{O}[/latex] above your Peak Pressure |
If this limit is hit, it will cut off the breath that is being delivered. This can be very uncomfortable for the patient and cause coughing and asynchrony. Monitor your pressures carefully and try to stay below [latex]30\text{ cmH}_2\text{O}[/latex] if possible. This is just the maximum limit. |
| Low Pressure | Set [latex]2\text{ cmH}_2\text{O}[/latex] below PEEP | Not set on every ventilator. It is good for sensing a leak or disconnect in the circuit. |
| High Volume | [latex]+200\text{ mL}[/latex] from your target volume | Monitor your volumes breath to breath. This alarm is set wide to avoid alarm fatigue. We as clinicians want to monitor our tidal volumes tighter than this when we are present, but this alarm will come into play when clinicians are not present. |
| Low Volume | [latex]-200\text{ mL}[/latex] from target tidal volume | Not important in control modes. Usually used for spontaneous modes |
| High Minute Volume | [latex]20\text{ Lpm}[/latex] | Set widely on purpose. Usually used in spontaneous modes |
| Low Minute Volume | [latex]3\text{ - }4\text{ Lpm}[/latex] or [latex]-1\text{ Lpm}[/latex] below the MV reading on the ventilator. |
Set widely on purpose. Usually used in spontaneous modes |
| Apnea time | [latex]20\text{ seconds}[/latex] | Standard used in adult patients. |
“Ventilator Alarms” from Basic Principles of Mechanical Ventilation by Melody Bishop, © Sault College is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.
