EXAM #2: MECHANICAL AND NONMECHANICAL VENTILATION Flashcards
What are the indications for mechanical ventilation?
1) Airway protection
2) ARDS
3) Shock
4) NM disorder
5) Respiratory/cardiac arrest
6) Acute elevation in ICP
7) Tachy or bradypnea
8) Respiratory acidosis
What lung units are poorly ventilated on mechanical ventilation?
Inferior and dependent lung units
*Gases are preferentially delivered to the anterior lung units with least resistance
How did the iron-lung work?
Negative pressure developed in the environment of the apparatus
*Did not move the diaphragm; therefore, it didn’t work very well
What is the difference between a mandatory and spontaneous breath on the ventilator?
Mandatory= ventilator will generate a pre-set number of breaths at a certain volume/pressure
- “Controlled”= initiated by the ventilator
- “Assisted”= patient effort initiates
Spontaneous= patient effort dictates INITIATION AND DURATION of breath
What are the three T’s to keep in mind when setting a ventilator?
1) Target (control)= aspect of inspiration that is primarily controlled by the ventilator
- Volume ( or “flow”)
- Pressure
2) Trigger= signal to initiate the breath
- Time
- Pressure
- Flow
3) Termination (cycling)= criteria that signals the end of the breath
- Volume
- Flow
- Time
What is a volume targeted breath?
Also known as “flow,” this is when the volume/flow of inspiration is the main variable controlled by the ventilator
*Airway pressure is variable in volume targeting
What is a pressure targeted breath?
This is when airway pressure is the main variable targeted during inspiration
*Tidal volume is and flow are variable
What is the most common mode of ventilator setting?
Assist control mode
What is the assist control mode?
- This is a mix of mandatory and fully assisted breaths, such that each breath gets the same tidal volume
- Can be pressure or volume targeted
*Generally, most commonly accepted; minimizes patient work of breathing
What are the disadvantages of assist control mode?
1) Can result in high minute ventilation and respiratory alkalosis
- Remember, control + assisted breaths get full support
2) Possible hyperinflation/barotrauma
What is intermittent mandatory ventilation or SIMV?
This is a mix of mandatory breaths, plus partially supported spontaneous breaths from the patient
*AC= spontaneous breaths outside mandatory are FULLY supported SIMV= spontaneous breaths outside mandatory are PARTIALLY supported
What is spontaneous ventilation (PSV)?
In this mode, there are NO MANDATORY BREATHS
- Patient initiated breaths are supported to a certain pressure
*Most comfortable mode for alert patient
What is the utility of PSV?
Used to determine if a patient is ready to come off the ventilator
How can you improve oxygenation in a patient on a ventilator?
1) Increase FiO2
2) PEEP
3) Increased inspiratory time
What are the drawbacks to increased airway pressure?
1) Increased deadspace from overdistended alveoli
2) Decreased venous return, CO, oxygen delivery from increased intrathoracic pressure
3) VALI from overstretching alveoli
4) Barotrauma
What determines PCO2 on the ventilator?
- Minute ventilation i.e. TV x RR
- Increased minute ventilation causes a DECREASE in PCO2
What is the normal TV for a patient on a ventilator? How does this change for a patient with ARDS?
6-8ml/kg/IBW
*This DECREASES in ARDS
In a patient with ARDS, how do TV vent. setting need to be changed?
ARDS= 4-6ml/kg/IBW
What is the goal for plateau pressure in the adult patient on a ventilator?
Less than 30 cm H20
What is the target pH for a patient on a ventilator?
Greater than 7.1
What are the ABCDEFs of ventilator liberation?
A= Assess and manage pain B= Breathing trial daily C= Choice of analgesics/sedation D= manage Delerium E= Early mobilization/exercise F= family engagement
What are the criteria for liberation?
1) Improving clinical status
2) Stable
3) Awake and interactive
4) Secretions controlled
5) Normal oxygenation
Roughly what ratio of patients have to be re-intubated after they are taken off the vent.?
1/5
What is the difference between difficult and prolonged liberation from the vent.?
Difficult= 1-3 failures in first 7x days
Prolonged= on vent. for more than 7x days
