modes of ventilation Flashcards
Types of Breaths
- Mandatory
- Assisted
- Spontaneous
What does mandatory mean?
machine starts breath and machine controls and ends the breath. Vent does all the work.
What does assisted mean?
Patient starts the breath and the machine controls and ends the breath.
What does spontaneous mean?
Patient starts the breath, patient controls and end the breath. Machine augments breath.
What is the difference between volume controlled and pressure controlled?
- The term CMV usually refers to volume ventilation or VCV
- Pressure controlled CMV is usually called PCV or P-AC
- Most modes assume volume unless prefixed by “P”
Continuous Mandatory Ventilation (CMV)
- All breaths are mandatory-full support
- Only appropriate when a pt makes no effort at breathing or when you want to completely control ventilation.
- The machine only triggers by time. Pt cannot add rate by assisting.
- Can be used for frail chest (2 or more broken ribs in 2 or more places)
What are indications for CMV?
- tetanus/seizure
- complete rest-24hrs
- crushed chest injury w/paradoxical movements
- cerebral malfunction
- spinal cord/phrenic nerve injury
- paralysis
- drugs
What are some complications with CMV?
- potential for apnea/death with disconnection
- important alarms-low pressure, low exhaled volume
- therapist must recognize spontaneous effort by patient and correct
What triggers, limits, and cycles CMV?
- trigger–>time
- limit–>volume (flow)
- cycle–>time/volume
- expiration–>passive, PEEP
Assisted Control (A/C) Ventilation
- all mechanical breaths-full support
- may be poorly tolerated in awake pts
- COPD pt may air trap
- Pts with rapid drive may hyperventilate
What triggers, limits, and cycles AC?
- trigger–>time/pts
- limit–>volume
- cycle–>volume/time
What are some common causes of rapid drive?
- anxiety
- pain
- hypoxemia
- metabolic acidosis
- inappropriate ventilator settings
How do you correct the drive?
by switching modes or sedate the patient
Here is more info on Assist Control Ventilation
- machine has a guaranteed min
- Pt determines maximum
- set rate @ 2 like pt is in control mode
Assisited Control (P-AC) Ventilation (PRESSURE)
- can also be PCV or PC-AC
- May reduce WOB since pt chooses own flow
what is P-ramp?
sloping the inspiratory pressure curve
What does IMV stand for?
Intermittent Mandatory Ventilation
What triggers, limits, and cycles IMV?
trigger–>time
limit–>flow
cycle–>volume/time
Does IMV cause breath stacking?
yes, because even if the patient is spontaneous breathing the vent will still deliver a breath.
What is SIMV?
synchronized intermittent mandatory ventilation
What is the differnence between IMV and SIMV?
- IMV is both mechanical and spontaneous breath and gives partial ventilatory support
- SIMV is just like IMV but mechanical breaths are PT/time triggered. Pt can also regulate own CO2 and pH.
What are some disadvantages of SIMV?
- SIMV with high PSV may increase WOB
- Acute hypoventilation may occur at lower rates
- Weaning may be prolonged
- PSV is needed to overcome WOB
- Fatique may occur in pts who have rapid shallow breathing
What triggers, limits, and cycles P-SIMV?
- trigger–>pts/time
- limit–>pressure
- cycle–>time
- compliance/resistance–>flow/volume
- spontaneous breaths in between
- they are pt triggered and pt cycled
Pressure Support Ventilation (PSV)
- spontaneous mode on vent
- augmented spontaneous breathing
- like PCV delivers a high flow of gas at beginning and then it tapers when pressure gradient equalizes
- decrease WOB by overcoming resistance to tubing and circuit.
