Modes of ventilation or methods of ventilator support
- Controlled ventilation
- Assist control ventilation
- Synchronized intermittent mandatory ventilation (SIMV)
- Pressure support ventilation
- Controlled ventilation or controlled mandatory ventilation (CMV)
- Delivers preset tidal volume at preset respiratory rate
- This mode ventilates the patient regardless of inspiratory effort.
- This effectively "locks out" the patient's effort to breathe.
- May be ordered for the patients who have no inspiratory effort, such as high cervical spine injuries.
- Also used for those patients who receive chemical paralysis as part of their medical treatment.
- Eg. Flail chest injury or head injury.
- Rarely used mode
- Assist control (A/C) (ACV)
- Delivers preset tidal volume whenever patient exerts a negative inspiratory effort (trigger).
- A preset respiratory rate ensures that the patient receives adequate ventilation regardless of spontaneous efforts.
- For example: A/C respiratory rate may be set at 10 breaths per minute at tidal volume of 800ml. If the patient initiates a negative inspiratory effort 16 times per minute, he or she will receive 800ml of air for each of 16 efforts.
- If the patient does not initiate any inspiratory effort he or she receives 800 ml of tidal volume 10 times per minute.
- Useful for the patients with normal respiratory drive and who are unable to sustain a normal tidal volume.
- Complication is respiratory alkalosis, especially if the patient’s respiratory rate is very high.
- Synchronized intermittent mandatory ventilation (SIMV)
- This mode delivers a preset tidal volume at a preset mandatory respiratory rate and permits the patient to breathe spontaneously at his or her own respiratory rate and depth between the ventilator breaths.
- The preset breaths are synchronized with the patient’s spontaneous efforts and helps to prevent patient-ventilator dys-synchrony.
- Helps to prevent respiratory muscle weakness and hyperventilation.
- Often ordered as a method for weaning patients from mechanical ventilation.
- Pressure support ventilation (PSV)
- Preset level of positive pressure is applied for the duration of a spontaneous breath
- Allows more even distribution of inspired gas.
- Augments a patients spontaneous tidal volume and decreases the work of breathing (WOB) associated with spontaneous breathing through an artificial airway.
- Pressure controlled ventilation (PCV)
- Generates the preset pressure during a preset inspiratory time at the preset respiratory rate.
COMMENTS