Summary of common ventilator alarm causes and solutions (Part 2)

The ventilator must have the function of issuing alarms for various events that require warning. The alarms include both voice-controlled alarms and light-controlled alarms.
The American Society for Respiratory Therapy recommends that ventilator alarms be divided into three levels according to their priority and urgency:
Level 1, immediately life-threatening situation;
Level 2, potentially life-threatening situations;
Level 3, conditions that are not life-threatening but may be harmful to the patient.
Most ventilators set the first-level alarm to a continuous screaming alarm, and set the second- and third-level alarms to intermittent, soft-sounding alarms. The alarm should be set in a state that is sensitive enough to detect critical events without causing false alarms.

7. Minute expiratory volume high limit alarm
Common reasons:
(1) Patient reasons: such as ARDS or other reasons (hypoxia, hypoventilation, endotracheal suction, elevated body temperature, pain stimulation, irritability) that cause the respiratory rate to increase.
deal with:
Increase oxygen concentration, increase ventilation, and use antipyretic, analgesic, sedatives, etc. to reduce oxygen consumption.
(2) Ventilator circuit or artificial airway factors: Water accumulates in the ventilator pipeline, causing frequent false triggers, inducing frequent air supply by the ventilator, and triggering an excessive minute ventilation alarm.
(3) The expiratory flow sensor is blocked by water.
deal with:
Clear the accumulated water and blockage in the sensor in time, and pay attention to pour out the accumulated water in the water bottle in time.
(4) Human factors: The tidal volume or respiratory frequency is set too high, the trigger sensitivity of the ventilator is too high, causing the respiratory frequency to be too fast, and the high limit alarm threshold of exhaled air volume per minute is set too low.
deal with:
Adjust the tidal volume or respiratory rate. If the condition requires it, adjust the alarm upper limit, reasonably adjust the trigger sensitivity, and set the alarm threshold appropriately. In addition, atomized inhalation during mechanical ventilation can increase the exhaled tidal volume and cause high-limit minute expiratory volume and high-limit alarms for exhaled tidal volume.

8. Time (ventilation frequency) alarm
Including ventilation frequency high limit or low limit alarm. Ventilation frequency high or low limit alarms, like minute expiratory volume alarms, can be caused by high ventilator frequency (automatic triggering of the ventilator, such as excessive trigger sensitivity or false triggering) or high spontaneous breathing frequency of patients caused by various reasons. Ventilation frequency high limit alarm.
Common reasons:
A low-limit alarm may occur due to suffocation alarm, low respiratory rate due to aggravation of the patient's condition, or low trigger sensitivity.
Others such as: improper inhalation time, the operator should be warned when the parameters of the ventilator cause the inhalation time to be too long, which may be caused by airway obstruction or failure of the expiratory duplex joint; inappropriate expiration time, if the exhalation time is too long, the operator should be warned. If the exhalation time is too long, this may be the "suffocation" time. If the exhalation time is too short, it indicates inverse ventilation or potential air trapping.
deal with:
Check the patient and corresponding parameter settings, as well as the corresponding fault-prone areas.

9. Suffocation alarm
An apnea alarm indicates that the ventilator is not detecting a breath, neither a spontaneous breath nor a ventilator-delivered breath. Some ventilators have a preset suffocation alarm time of 20 seconds, and some ventilators allow the operator to preset the suffocation alarm time. Air source alarms are often accompanied by suffocation alarms. For reasons and solutions, see Air source alarms. Asphyxiation alarms are often accompanied by low pressure or low Ve alarms.
Common reasons:
(1) The patient has no spontaneous breathing or the spontaneous breathing frequency is too low;
(2) The breathing tube and connections are detached or leaking;
(3) Machine failure, flow sensor detection function is poor or damaged, timing board and other mechanical failures;
(4) Inappropriate trigger sensitivity (or the occurrence of endogenous PEEP may prevent the patient from triggering, resulting in invalid trigger force); the set apnea alarm parameters are inappropriate; the flow sensor installation position is inappropriate; the minute ventilation is set too low, etc. .
deal with:
First, determine whether the patient is being ventilated. According to the patient's condition, reconnect the ventilator, change the ventilation mode (some ventilators automatically convert to backup ventilation, and once the patient is found to be exerting force, backup ventilation will be automatically canceled), simple respirator-assisted ventilation Wait for treatment; after it is clear that the patient is being ventilated, further identify and correct the cause (whether the frequency of commanded breathing, trigger sensitivity and other settings are appropriate, set them correctly according to the situation, correct the leakage of the circuit, check the function of the flow sensor or replace it, and replace the ventilator if necessary ).

10. Oxygen concentration alarm
The alarm limit is 10% to 20% higher or lower than the actual set oxygen concentration.
Common reasons:
(1) The power supply of the air compressor is not connected properly or the switch is not turned on, resulting in pure oxygen supply. Check the air compressor power supply and start it.
(2) Machine failure, oxygen battery exhausted, oxygen battery needs calibration, air-oxygen mixer failure, air compressor failure.
(3) The alarm limit setting is wrong.
deal with:
Ask an engineer to recalibrate the oxygen battery or replace/turn off the oxygen battery, replace the air-oxygen mixer, and replace the air compressor.
Pay attention to setting the alarm limits correctly. Check the patient and oxygen supply.
If necessary, perform alternative ventilation methods (such as breathing bag pressure).

11. Gas source alarm
The ventilator does not have enough oxygen or air supply, and the working pressure gauge pointer reads zero or swings greatly during inhalation, with a swing amplitude exceeding 20cmH2O. A stable supply of gas (oxygen and compressed air) is very important for the normal operation of the ventilator.
Common reasons:
(1) Mechanical failure. The air supply pressure of the oxygen/air compressor is insufficient, the air compressor is over-pressure or overheated, the air-oxygen mixer is faulty, and the suction valve is disconnected. Check the oxygen cylinder or central air supply pressure and air compressor pressure to ensure the air supply pressure is 3.0~5.5kg/cm2, restore the overpressure or overheating protection button, replace the air-oxygen mixer, and adjust the suction valve.
(2) Human factors. The air compressor power supply is not connected or the switch is not turned on, the air/oxygen plug is not connected properly, the plug does not match or slips off, the oxygen switch is not fully opened, the air compressor air inlet filter sponge dust is blocked, etc.
deal with:
Check the condition of the patient and oxygen source, and handle accordingly. If necessary, perform alternative ventilation methods (such as breathing bag pressure).

12.Power alarm
The external power supply fails or the battery power is insufficient.
deal with:
The ventilator should be immediately disconnected from the patient's artificial airway, artificial ventilation should be provided, and treatment should be carried out in a timely manner. It is recommended to purchase a ventilator with a built-in battery and configure a regulated power supply to facilitate mechanical ventilation in the event of a sudden power outage. You can still proceed.

13. Humidifier alarm
Humidifier is an important part of the ventilator. Good heating and humidification can prevent and reduce secondary respiratory infections in patients with mechanical ventilation, make the airways less likely to produce phlegm scab, reduce the viscosity of secretions, and promote sputum excretion.
Common reasons:
There is no heating, overheating; the fuse is burned out; the heating wire is damaged; the temperature sensor is damaged; the humidification effect is unsatisfactory; air leakage, water leakage, etc.
High temperature alarms are often caused by improper temperature settings, late addition of water, instrument failure, etc.;
In addition to instrument failure, low temperature alarms should also pay attention to the following issues: improper connection of the ventilator pipeline, such as mistakenly connecting the humidifier to the exhalation circuit, connecting the temperature probe to the exhalation end of the Y-shaped tube or the common end of breathing, etc.; Y The temperature probe on the line tube has fallen off or is facing downwards; the heating wire power cord is disconnected from the ventilator humidifier; there is leakage in the ventilator circuit, etc., which should be dealt with in time. If the instrument fails, please contact the equipment personnel for repair in time.

14. Others
Study on the setting of ventilator tidal volume and airway high pressure alarm value during cardiopulmonary resuscitation and continuous chest compression. The mode adopts volume-controlled ventilation, respiratory rate 10 times/min, inspired oxygen concentration 100%, inspiratory time >1s, and trigger sensitivity turned off. Or adjust to the highest value, with a tidal volume (VT) of 6 to 7 mL/kg and a high-pressure alarm value of 60 cmH2O, which has better ventilation effects than conventional VT and conventional high-pressure alarm values, and the incidence of barotrauma has not been significantly increased. Continuous and rapid heart compressions cause intrathoracic pressure to increase, and the ventilator provides air
When the patient encounters resistance from the passive movement of the thorax, the PIP rises sharply. Once it exceeds the conventional high-pressure alarm value, the ventilator will automatically open the exhalation valve, significantly reducing the patient's inhaled VT, affecting the effect of CRP, such as increasing the Airway high pressure alarm value to ensure VT, may lead to an increase in the incidence of barotrauma. Recent studies have proven that PIP generally only acts on the larger bronchi rather than the alveoli, and is not the main factor causing barotrauma. At the same time, continuous and rapid heart compression can easily This may cause the ventilator to be accidentally triggered. Therefore, the trigger sensitivity should be turned off or adjusted to the highest value.
remind:
Ventilator alarms are a common problem encountered clinically. The alarms send out sounds or signals (such as red light flashes) to alert medical staff of situations that need to be known or paid attention to. If you just turn off the alarm button without eliminating the cause of the alarm, it will be very dangerous for the patient.

Although the ventilator types and operating panels are different, the general principles for handling ventilator alarms are the same. The most basic principle is that when the ventilator alarms, the patient's cause must be eliminated first. The most important principle is that if you cannot eliminate the cause of the alarm immediately, you should take the patient off the machine immediately, squeeze a ball and give 100% pure oxygen, and others will continue to investigate the cause.