Modes of Mechanical Ventilation Flashcards
peak inspiratory pressure
total pressure required to distend lungs and airways
used to calculate dynamic compliance
plateau pressure
distending pressure to expand only the lungs
measures redistribution of air flow through lungs
used to calculate static compliance
interdependent relationships exist between ___
variables we control (control variables)
RR, tidal volume, pressure, I:E ratio
total respiratory cycle components
each breath has 4 parts
- start of inspiration
- inspiration itself
- end of inspiration
- expiration
components: inspiratory time (ti), expiratory time (te), total cycle time (TCT)
total respiratory cycle variables
impact how each mechanical breath is initiated, sustained, and terminated
trigger variable
start of inspiration
affected by:
pressure - decrease stimulates ventilator to deliver a breath
volume - change can stimulate vent to deliver a breath
flow - change stimulates vent to deliver breath
time - set time interval triggers vent to deliver breath
limit variable
maintenance of inspiration
once threshold reached, variable won’t exceed set limit (does not cause termination of inspiration!)
pressure- upper pressure limit that cannot be exceeded
volume - upper volume limit that cant be exceeded
flow - max airflow that can’t be exceeded
cycling variable
transition to expiration
based on:
volume- vent delivers flow until set volume achieved
pressure - once pressure achieved flow will transition to expiration
flow- once inspiratory flow drops below set threshold will transition to expiration
time- terminates inspiratory breath after predetermined inspiratory time has been delivered
baseline variable
end expiration
used to prevent atelectasis
individualized to patient
PEEP
alveolar pressure above atmospheric
goal: improved oxygenation
intrinsic: secondary to incomplete expiration (autopeep)
extrinsic: provided by mechanical vent (applied peep)
autoPEEP
incomplete expiration prior to initiation of next breath
causes progressive air trapping
causes: high minute ventilation, expiratory flow limitation, expiratory resistance
volume control ventilation
set tidal volume at set respiratory rate time - trigger variable volume- limit variable time- cycling variable airway pressure will change on breath by breath basis airflow - constant
why choose volume control ventilation?
maintenance of set minute ventilation through direct manipulation of Vt and RR
set alarms for airway pressure to protect the patient
pressure control ventilation
delivers set inspiratory pressure at set respiratory rate
time - trigger variable
pressure- limit variable
time - cycle variable
airway pressures controlled by user, Vt can change on breath by breath basis
why choose pressure control ventilation?
set pressure limit to avoid barotrauma from delivery of excessive pressure
decelerating flow pattern allows for homogenous distribution of inspired gas throughout lungs
