Mechanical Ventilation Flashcards
Define the trigger variable
Parameter that initiates inspiration; how the ventilator determines when to deliver a breath
What is the trigger variable in patients not trying to breathe? Trying to breathe?
Time; a change in airway pressure or gas flow as a result from the patients attempt to breathe
What is the cycle variable?
Parameter by which ventilation is terminated; typically time; determined by preset RR and I:E ratio. I of 1 commonly recommended
What is the limit variable? How does it differ from the time variable?
Parameter that the breath cannot exceed during inspiration; it does not terminate the breath
What is the baseline variable?
Controlled during exhalation; airway pressure most common baseline variable manipulated
What are the 3 possible breath patterns on a ventilator?
Continuous mandatory ventilation, continuous spontaneous ventilation, intermittent mandatory ventilation
In continuous mandatory ventilation the ventilator is responsible for__________________.
All components of the breath.
Assist controlled ventilation provides _____________ and is used in patients with ____________ or ____________.
Maximal support of the respiratory system; severe pulmonary disease or no respiratory drive.
Define continuous spontaneous ventilation
Ventilation is triggered and cycled by the patient
________________ is the breath pattern used in patients with a reliable, adequate respiratory drive
Continuous spontaneous ventilation
CPAP is most appropriately used when?
As part of a spontaneous breathing trial to determine a patients suitability for weaning
What is PSV?
Pressure support ventilation; the ventilator augments inspiration during spontaneous breaths by increasing airway pressure
_________ is designed for use in patients with normal respiratory drive but inadequate ventilator ability
PSV (usually with CPAP)
What is SIMV? When is it used?
Synchronized intermittent mandatory ventilation - machine tries to synchronize mandatory breaths with patient inspiratory efforts; unreliable respiratory drive or those that do not require maximal respiratory support
What is the basic definition of a ventilator mode?
Identification of a control variable and the breath pattern (ideally including any phase variables)
What factors affect the I:E ratio?
inspiratory time, % inspiratory time, inspiratory flow rate in conjunction with respiratory rate
Why is an I:E ratio of 1:2 ideal?
To ensure the patient has fully exhaled before the next breath
What is breath stacking?
Animal is not able to fully exhale before the next breath, some degree of pressure/air remains in the alveoli at the beginning of the next breath
CPAP does what to lung function parameters?
Increases FRC and compliance, enhances gas exchange and oxygenation (does not augment airflow during inspiration more than baseline pressure provides)
CPAP alone is only suitable when?
In patients with a strong respiratory drive and adequate ventilatory function
PEEP does what to FRC?
Increases it
What is intrinsic vs extrinsic PEEP?
Extrinsic set by machine, intrinsic develop as a consequence of inadequate exhalation time or small airway collapse during exhalation
What are some positive effects of PEEP?
Recruit collapsed alveoli, prevent collapse of unstable alveoli, improve V/Q, improve pulmonary compliance, reduce work of breathing, reduce VALI
How does PEEP reduce VALI?
Preventing injury associated with cyclic re opening and collapse of alveoli with each breath