About Ventilation

Ventilator Modes

Assist/Control (A/C)

• Breaths delivered by the ventilator control either volume or pressure
• Ventilator delivers the same measured breath every time
• Breath can be initiated by the patient or the ventilator

Spontaneous (SPONT)

• Patient-initiated and sustained breathing
• Ventilator controls oxygen amount, and pressure
• Delivers flow and volume as needed to help the patient breathe
• Patient can breathe at a continuous positive airway pressure

Synchronized Intermittent Mandatory Ventilation (SIMV)

• Combination of set patient or ventilator-initiated breaths delivered by the ventilator that control volume or pressure, and the patient’s own spontaneous breaths.

Ventilator Breath Types

Volume Control Ventilation (VCV/VC)

• Mandatory breath
• Can be used in either A/C or SIMV modes
• Targets a specific lung volume during inspiration

Pressure Control Ventilation (PCP/PC)

• Mandatory breath
• Can be used in either A/C or SIMV modes
• Targets a specific pressure during inspiration

Pressure Support Ventilation

• Spontaneous breath
• Can be used in either SPONT or SIMV modes
• Targets a specific pressure to achieve adequate tidal volume

Common Alarms

If an alarm occurs, the caregiver should always evaluate the patient before checking the ventilator. Always check to make sure the patient is still connected to the ventilator and all circuits/tubing are tightly connected, and not kinked or blocked in any way.

There are important differences in alarm setup and responses between ventilators and even between the different circuit types on the same ventilator.

It is vitally important to be aware of the type of breathing circuit setup in use and whether, with that setup, the volume alarms are related to inspiratory or expiratory volume measurements.

Always refer to the Ventilator's user manual.

High Airway Pressure Alarms

If the ventilator pressure reaches the set limit, an audible and / or visual alarm activates, and in most cases, the breath ends.

Some causes for high pressure alarms are:

• Kinks in the patient circuit or tracheostomy tube
• Water in the ventilator circuit
• Increased or thicker mucus or other secretions blocking the airway (caused by not enough humidity)
• Bronchospasm
• Coughing, gagging, or “fighting” the ventilator breath

Low airway pressure alarms

If the pressure inside the breathing circuit drops below the Low Airway Pressure Alarm limit set on the ventilator, an audible and / or visual alarm activates.

Some causes for low pressure alarms are:

• The patient becomes disconnected from the ventilator circuit
• Inadequate inflation of the tracheostomy tube cuff
• Poorly fitting noninvasive masks or nasal pillows/prongs
• Loose circuit and tubing connections
• The patient demands higher levels of air than the ventilator is putting out

High and low rate alarms

If the rate increases or decreases beyond the set alarm rate (the limit for the alarm), these alarms will trigger an audible and/or visual alert alarm. In the case of a Low Rate Alarm (often labeled "Apnea" alarm), back up ventilation may be provided, depending on settings.

• An agitated or fatigued patient may have an increase in respiratory rate. Sedated patients or patients with impaired neuromuscular function may also have a decreased respiratory rate.

High and low expiratory volume alarms

High volume expiratory alarms may indicate a high respiratory rate, as well as increased patient demand for air because of pain, anxiety, or improper ventilator settings.

• Low volume expiratory alarms typically are caused by air leaks.

High and low inspiratory volume alarms

High volume inspiratory alarms may indicate a leak or disconnect, high respiratory (breathing) rate, or increased patient demand for air because of pain, anxiety, or improper ventilator settings.

• Low volume inspiratory alarms may be caused by mucous plugging, a need for suctioning, tube obstruction, a slower respiratory rate or shallow breathing.