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.
What triggers, limits, and cycles PSV?
- trigger–>patient
- limit–>pressure
- cycle–>flow
What is expiratory time sensitivity?
- ETS adjusts the flow cycle level of pressure supported breaths.
- In the event of leak, ETS % can be adjusted that pressure supported breaths will end. Maximum setting is 45% which will be effective for all but large leaks.
What are 2 applications for PSV?
- PSV and SIMV: used to overcome resistance in tubing, poor demand flow and airways.
- Stand alone PSV: what ever is needed to achieve VT of 10-12 mL/Kg than titrated to let pt do more work.
What does CPAP and PEEP mean?
Continuous Positive Airway Pressure and Positive End Expiratory Pressure
- used to describe baseline
- CPAP is used with spontaneous breathing
- PEEP is used with mechanical breathing
SIMV with PSV
- combines 2 modes of A/C (with limit # of breaths) and PSV during the spontaneous breaths
- used all the time
PSIMV with PSV
-a combination of pressure assist/control breaths and PSV during spontaneous breaths
SIMV c PSV and CPAP
- add PEEP to the mix
- remember they are volume targeted machine breaths
- machine breaths are pressure targeted
Mandatory Minute Ventilation
- used for weaning
- set MV at 70-90% of current VE
- vent provides rest
- vent monitors spontaneous MV when it drops below set level the vent provides mechanical support to make up difference
Two ways of Mandatory Minute Ventilation
- increasing the breath rate (bear 1000)
- increasing the preset pressure (Hamilton)
- machine reads total volume in one minute, pt can breath at low volume very fast and keep same Min volume
- must set high flow and low Vt correctly
What are other terms for trigger?
- trigger
- sensitivity
- initiate
- start
- change from E to I
- begin the breath
What are other terms for inspiration (pressure limited)?
- pressure controlled
- pressure targeted
- pressure limited
- pressure oriented
- the machine reaches a set pressure and maintains that pressure during the breath
- flow varies with lung changes
- volume varies with lung changes
What are other terms for inspiration ( volume limited)?
- volume oriented
- volume targeted
- volume limited
- volume controlled
- flow controlled
- volume does not change with lung
- pressure varies with lung changes
What are other terms for cycle?
- cycle
- end of breath
- terminated
- extinguish
- begin expiration
- change from I to E
what mode is started by the machine or pt, pressure is guaranteed, inspiration is terminated when a set time has elapsed?
- pressure mode
- pressure assist control
What are all the volume modes?
- control
- A/C
- IMV (control and spont)
- SIMV (assist/control and spont)
- SIMV c PSV (assist/control and PSV)
What are all the pressure modes?
- PSV
- PC/AC, P-AC, PCV
- PSIMV-PAC(PC) and spon
- PSIMV c PSV
What mode of ventilation is a mixture of assist/control, pressure oriented, time cycled breaths and flow triggered, pressure oriented, flow cycled breaths?
PSIMV/PSV
What mode of ventilation begins inspiration with flow, allows volume to vary during the breath, and begins expiration after a predetermined low flow is reached?
PSV
