Mv Flashcards
Ventilation
Movement of 02 in and co2 out
Inspiration
Contraction causes negative pressure, active process
Expiration
Passive process, positive pressure causes recoil
Tidal volume
Amount of air moved in and out in one breath
Minute volume
Amount of air moved in a minute
FRC
Functional residual capacity - the amount of air left at the end of expiration.
Anatomical dead space
air not involved in gas exchange in upper airway and tubing
Physiological dead space
Air not involved in gas exchange at the alveoli level. Ventilation but no perfusion
Pip
Peak inspiratory pressure- the maximum pressure required to inflate the lungs. Determined by compliance and resistance in vol control
Peep
Maintained positive pressure at the end of expiration
Peep benefits
Increase FRC
Prevent airway collapse
Maximise alveoli recruitment
Increase surface for gas exchange
Disadvantages of peep
Hyperinflation
Co2 retention
Impaired venous return
Decreased CO
Ti
Inspiratory time: time for gas flow/gas exchange before expiration
Compliance
- Extent to which lungs/thoracic cavity can be distended
- determined by elasticity
- high: min pressure required to expand the lungs
- low: max pressure “” “
Resistance
Amount of pressure required to move gas
Smaller airway- > resistance
Cmv and indications
Control mandatory ventilation:
- preset tv and f
- breaths are machine trigger, limited, and cycled
Full control and no real effort eg gbs
Machine cycled mandatory breath
Mandatory- machine trigger limited and cycled
Machine cycled assisted breadth
Assisted - triggered by pt, limited and cycled by ventilator
Patient cycled supporter breath
A spont breath with added inspiratory pressure
Spont breath
Pt performs all work of ventilation
Volume control
Volume is constant pressure is variable
-depends on compliance and resistance
Cmv disadvantages
No spont breaths
A synchrony and atrophy, muscle weakness
Volume assist control a/c mode & indications
Set f and tv
Pt can trigger own breaths and is assisted with set tv
- heavily sedated pt
Unstable resp drive or weak/fatigue
A/c advantages and disadvantages
A-pt can control rate
Prevents muscle fatigue
D- asynchrony
Auto peep
Simv
Preset tv or pressure
Can initiate spont breaths between mandatory, synchronised
Spont breaths assisted by ps
Window of time
Window of time
Delivers mandatory breaths with pts inspiratory effort
simv vol
Indications
Advantages disadvantages
Normal resp drive, weaning
A-Improved synchrony Increased comfort Decreased breath stacking B-fixed flow variable pressure Constant despite compliance resistance
Compliance
The stretch on the lungs
The pressure required to explans lungs and thoracic cavity
Increased compliance = deceased elasticity (emphysema)
Resistance
The amount of pressure required to move gas.
Degree of inhibition to gas flow
Pressure control ventilation
A and d
Pressure constant vol variable
Volume dependant on patients compliance and resistance
A-good at opening airways Good pt vent synchrony Better gas flow and distribution D-no guaranteed volumes More haemodynsmic effects
PSV
Pressure support ventilation
Spontaneous mode
Preset pressure achieved when pt inspires
Volumes variable - effort, c, r
Auto flow
Regulates inspiratory pressure and flow
Delivers volume at lowest possible pressure reducing airway pressure
Peep Pro and con
-increase Frc
-> surface area and gas exchange
Prevent alveoli collapse
< airway resistance
< wob
< cyclic atelectrauma
< l) vent after load
Con:
Haemodynsmic compromise Barotrauma from over distension
Gas trapping and hyperinflation
> icp
Lung protective strategies
< tv
< pplat 30
Check peep
Volutrauma
Hyperinflation and shearing
Barotrauma
Alveoli rupture
Pnumo
BiotraumA
Release Inflam mediators
