Viva Crash Course Flashcards
Phases of breath delivery/variables:
- Trigger (how it begins)
- Control or target (preset)
- Cycling (how it ends)
Common triggers:
- Time trigger
- Flow trigger
- Pressure trigger
Control variable
Defines which aspect of inspiration is the primary variable controlled by the ventilator during inspiration
(pressure and flow)
What is a trigger variable?
Variable which determines when a ventilator initiates a machine-driven breath
2 control variables:
- Flow
2. Pressure
Calculate compliance
Compliance= ^Volume/ ^Pressure
3 Cycling variables:
- Flow
- Volume
- Time
3 breath types:
- Mandatory
- Assisted
- Spontaneous
Describe mandatory breaths (trigger/support)
Triggered by the ventilator with full level of support
Describe assisted breaths (trigger/support)
Triggered by the patient, either full support or partial support
Describe spontaneous breaths (trigger/support)
Non-triggered and no support
Tidal volume
Volume of each breath
Respiratory rate:
I:E Ratio
The ratio of inspiratory time to expiratory time
Fi02
The fraction of inspired oxygen delivered on inspiration to the patient
PEEP is?
Residual airway pressure at the end of inspiration
Why is humidification important
- Warm and moisten gas to facilitate cilia action and mucous removal
- Prevent drying and irritation or mucosa
- prevent solidification of secretions
Describe CMV
Controlled mandatory ventilation
Breaths = mandatory; nil pt trigger
Requires deep sedation and paralysis so is not usually used outside of OT
Describe assist-control ventilation
breath type, trigger, cycle
Mix of machine (mandatory) or patient (assisted) triggered breaths, but ALL ARE CYCLED by the VENTILATOR.
Ventilator senses inspiratory effort by the patient and responds by delivering breath.
Patient can vary RR, but a backup rate is set to prevent hypo ventilation.
Disadvantages of assist-control ventilation:
Can lead to:
- Resp alkalosis
- Auto-peep
- Hypotension in ^ventilating pts
Advantages of Assist control ventilation
activation of the diaphragm with patient triggering
SIMV (stands for?) uses what breaths?
Synchronized intermittent mandatory ventilation
Preset minimum number of mandatory breaths (Pi or VC) AND also allows spont breaths inbetween
Describe the 3 breaths in SIMV
Mandatory breaths: non-synchronized, time triggered, time cycled)
Synchronized breaths: non-sychronized, pressure or flow triggered, time cycled)
Non- Synchronized breaths: Pressure or flow triggered, flow cycled)
Difference between AC & SIMV spontaneous breaths?
AC- Full support
SIMV - Partial support
Cycling variable:
What signals the ventilator to terminate ventilation
Volume controlled ventilation
Flow (preset tidal volume) delivered to the airway is constant. Changes in airway resistance or compliance results in
variable pressures
Pressure control
Pressure delivered to the airway is constant regardless of airway resistance or compliance
(variable tidal volumes)
Pressure control ventilation indications:
Patients with particularly high chance of barotrauma
Pressure control ventilation
Mandatory breaths only, patient unable to trigger
Time: pressure:time
Pressure support ventilation
No mandatory breaths, all patient triggered
Pressure applied by the vent augments patient effort during the breath
Time variable
COPD patients may do better with what trigger?
Flow
With volume controlled ventilation, when will the ventilator cease inspiration?
After the preset volume has been delivered
With flow cycled ventilation, when will the ventilator cease inspiration?
After airflow drops below a preset threshold, typically approx 25% peak flow
With time cycled ventilation, when will the ventilator cease inspiration?
