Alarms warn of possible dangers related to medical ventilator system.

 

Low-pressure alarms are usually set at about 5 to 10 cm H2O below PIP. They are used to detect patient disconnections and leaks in the system.

 

High-pressure alarms are set at about 10 cm H20 above PIP and usually end inspiration when activated. They indicate when the patient coughs, and if secretions increase, compliance drops, or there are kinks in the ET or circuit tubing.

 

Low PEEP/continuous airway pressure (CPAP) alarms are usually set at about 2 to 5 cm H20 below the PEEP level and indicate when the PEEP or CPAP level has dropped, usually because of leaks.

 

Apnea alarms are used to monitor mandatory and/or spontaneous breaths. An apnea period of no more than 20 sec is the most accepted maximum. In some situations apnea alarms are set so the patient will not miss two consecutive machine breaths (apnea time> total cycle time[TCT] and < [TCT x2]). Apnea settings provide full medical ventilator support for the patient if apnea occurs and should be set appropriately.

 

Most medical ventilators have a ratio alarm or indicator that warns when the inspiratory time (T I ) is more than half the set TCT. Some medical ventilators, such as the Bird 8400, will automaticallv end inspiration if the T E gets so short that patient does not have time to exhale.

 

Low gas-source alarms alert the operator that the available high pressure gas source is no longer functional. This alarm can be critical for newer microprocessor medical ventilators that rely on high-pressure gas to function. This is particularly true when they do not come with a built-in compressor. This alarm cannot be silenced if gas is critical to medical ventilator operation.

 

Other medical ventilator alarms include low V T , low and high V E , low and high rate (f), and low and high oxygen percentage. There are no predetermined levels for setting these parameters; operators must use their judgment when setting alarms to indicate possible changes in patient condition.

 

Alarms should not be set so sensitively that they are constantly being triggered. Suggestions are as follows:

Low exhaled VT 10% to 15% below set VT.

Low exhaled minute volume: 10% to 15% below average minute volume.

Oxygen percentage: 5% above and below set oxygen percent.