Mechanical Ventilation Flashcards
What are the goals of mechanical venilation?
- Improve ventilation
- Improve oxygenation
What are common indications for mechanical ventilation
- Failure to maintain/protect airway
- Failure to ventilate/oxygenate
- Anticipation of need based on clinical course/likely deterioration
Define compliance
- Amount of work required to inflate the lungs (i.e. stretch)
Define resistance
- Amount of work required to move air through the lungs (i.e. airway diameter)
Define elasticity
- Ability of lungs to recoil and expand
Define deadspace
- Inhaled air that does not take part in gas exchange
Define FiO2
- O2 concentration of air
Define I:E
Inspiratory/Expiratory ratio
- Inspiratory Time compared to expiratory time
IE TE = total cycle time
Define tidal volume
- Volume of gas moved in/out of lungs in single inspiration (VTI) or expiration (VTE)
What is tidal volume roughly equal to?
6-8mLs/kg
Define expired minute volume
- Total volume of gas moved out of the lungs in a minute
Define rate
- Mandatory breaths to be delivered in a minute
Define total rate
(fTotal)
- Total breaths taken in a minute
= rate + spontaneous breaths
Define flow trigger
- Inspiratory flow in L/min that triggers ventilator to deliver a breath
Define expiratory trigger sensitivity (ETS)
- % of peak inspiratory flow that triggers ventilator to cycle from inspiration to exhalation
Define peak airway pressure (Ppeak)
- Highest pressure reached during last breath
(affected by airway resistance and compliance)
Define Pressure control (Pcontrol)
Amount of pressure applied during inspiration in addition to PEEP
Define Pressure support (Psupport)
Amount of pressure delivered to support spontaneous breaths
What does VC SIMV+ stand for
Volume Controlled Synchronised Intermittent Mandatory Ventilation
How does VC SIMV+ work
- Ventilator delivers a set tidal volume at specific rate and supports patient’s own breathing
- Ventilator detects patient’s spontaneous breath and either augments this and synchronises it with the pre-set breath OR supports breath with pre-set pressure support
What does PC SIMV+ stand for?
Pressure Controlled Synchronised Intermittent Mandatory Ventilation
How does PC SIMV+ work
- Pressure and rate are set
- Patient determines their own tidal volume to reach pre-set pressure target and can take spontaneous breaths
What are the benefits of VC SIMV+
- Less change of respiratory muscle atrophy as patient can self-ventilate
- Level of sedation can be lower
- Less haemodynamic compromise as lower pressures are used
- Decreased risk of barotrauma
What are the benefits of PC SIMV+
- Reduces risk of barotrauma
- Compensates for air leak when using uncuffed ETT tube (such as in paeds)
- Can be used with patients requiring higher airway pressures (i.e. non-complaint lungs ARDS, chronic lung diseases)
