Breath design and delivery 2 (mechanical ventilation)

What is a limit variable?

The maximum value a variable can attain in mechanical ventilation

all ventilators have a maximum __________ limit regardless of what the limit variable

pressure

the high-pressure limits alarm is set to _______CMH20 above what pressure?

10CMH2o above-average peak inspiratory pressure

what two ways can a ventilator respond when the pressure limit/pressure alarm is hit?

1. ending inspiration by opening the exhalation valve

2. allow inspiration continue and only open the exhalation valve enough to vent the excess pressure

ventilators which allow the excess pressure to be vented off instead of ending inspiration when the high-pressure alarm is hit use a _______________ valve

floating exhalation valve

what happens when the maximum pressure limit is reached and the ventilatory end inspiration (what is the consequence of this?)

the patient will not receive entire tidal volume

why is a ventilator with a floating exhalation valve better when the pressure limit alarm is hit?

The floating exhalation valve will allow the excess pressure to be vented off and the patient will still receive the total tidal volume

the ventilator circuit external and internal all contribute the patients compliance and resistance. True or False?

True

What is the cycle variable?

The variable that ends inspiration when it is achieved

The cycle variable can be?

volume

pressure

flow

time

for each ventilator mode there is a _________ cycle variable

primary

describe volume as a cycle variable

the ventilator ends inspiration after a predetermined volume has been reached

volume cycles occurs in _________-Control ventilation (when no inspiratory pause is set)

Occurs in volume control

what does the cycle variable change to in volume-controlled ventilation when an inspiratory pause is set?

time cycled (breath will cycle when the inspiratory pause time is elapsed)

A bellows system is a _________ cycling ventilator

volume

in a bellows system when full excursion of the bellows is reached ___________ stops

inspiration

2 ways a bellows stops inspiration is due to?

1. microswitch activated and sends signal to circuitry

2. touch sensor

A ventilator can use _____ sensors in volume cycling

flow

volume is a product of ____/_____

flow/time

the ventilator ends inspiration after a predetermined time has been reached. This can be defined as a ________ cycled breath

time

describe flow cycling

the ventilator ends inspiration after a predetermined flow has been reached

what is the primary cycling mechanism for spontaneously breathing patients?

flow cycling

when does inspiration end in a flow cycled breath?

when a low "terminal" flow is reached (flow decreases to a certain percentage of peak flow that is set to trigger the end of inspiration)

describe pressure cycling

the ventilator will end inspiration when a certain pressure has been reached

_______ is not a common primary cycling mechanism

pressure

_______ is not a common primary cycling mechanism but is always available as a back0-up cycling mechanism

pressure

The baseline variable is the parameter that is controlled during _________

expiration

what is a baseline variable

the parameter that is controlled during exhalation

what is the most common baseline parameter that is controlled

pressure

baseline pressures are always relative to _____________ pressure

atmospheric

baseline pressure is not affected by compliance or resistance. true or false? what can affect the baseline pressure in the patient

true. Air trapping

ZEEP

zero end expiratory pressure

ZEEP is the default baseline during positive pressure ventilation. True or False?

True

PEEP

positive end expiratory pressure

this is the application of positive pressure throughout expiration. What is this describing?

PEEP

PEEP can maintain the patients ________ and can help improve oxygenation

FRC

PEEP is referred to as _______ when using with spontaneous breathes only

CPAP

CPAP

continuous positive airway pressure

CPAP is used with non _________ ventilation

mechanical

draw an airway pressure/time graph showing normal CPAP (no extra pressure support)

okay

Draw an airway pressure/time graph showing CPAP with ventilatory support (BIPAP)

okay

how can you tell a breath is spontaneous in mechanical ventilation?

a negative deflection on inspiration (would be positive in a mandatory breath)

what are the 3 benefits of PEEP

1. prevent alveolar collapse at end expiration

2. increased FRC

3. improves oxygenation

FRC increases approximately ______ml per 5 cm H2O

400ml

describe the Underwater column external PEEP device

Expiratory limb is routed into a basin filled with water witch an outlet that allows gas flow out to ambient. The amount of water in the basin controls the level of peep provided (backpressure)

what is a threshold resistor?

An external PEEP device

On which part of the ventilator would an external PEEP device be attached to?

The expiratory limb

the levels of PEEP on an external PEEP =device are adjusted on the ____________ and the level of PEEP is read off of the ventilators _____________

valve itself, manometer

describe the weighted ball external PEEP device

The patient exhales through the expiratory limb against a weight ball valve. depending on the weight of the ball indicates how much PEEP is provided

what is a disadvantage for the weighted ball external PEEP device

It is gravity dependent and must be in the upright position to work

how does the spring loaded external PEEP device work?

patient exhales against a spring and the tightness of the spring indicates the amount of PEEP provided

describe the magnetic external PEEP device

patient exhales against a valve with a magnet in it. the strength of the magnet is adjustable and indicates the level of PEEP

the balloon style PEEP device in an internal or external PEEP device?

internal

how does the balloon internal PEEP device work?

balloon ins inflated or deflated and determines the amount of air allows to escape and the level of PEEP

the __________ internal PEEP device uses a current and magnet applied to a solenoid that is attached to a shaft and the shaft pushes against a diaphragm to adjust the amount of expiratory flow allowed to escape

electromagnetic

NEEP

negative end expiratory pressure

the application of sub-atmospheric pressures to the airway during expiration. what is this describing ?

NEEP/negative end expiratory pressure

what was NEEP originally intended to be used for

to avoid the cardiovascular effects of PPV

what is the danger of using NEEP

causing alveolar collapse

on a pressure-time waveform, the expiratory pressure goes falls faster than usual and below the baseline. What does this indicate?

there was application of NEEP (negative end expiratory pressure)

APRV

airway pressure release ventilation

what is time limited expiration

a special circumstance where I time and E time is controlled

what is are the benefits of continuous gas flow during expiration

- minimize resistance to exhalation

- provide flow on demand to patient

what maneuver is used to measure pressures at end expiration ?

an expiratory hold

Intrinsic PEEP

also called auto-PEEP, is trapped air caused by inadequate expiratory time

Extrinsic PEEP

positive end-expiratory pressure applied by the operator Mechanical application of PEEP.

the ________ variables work on the "if-the" principle

conditional

describe a conditional variable

if the value of a set conditional variable is reached than some action occurs to change the ventilatory pattern

VE =

RR X VT

the Sigh function is considered a _____________ variable

conditional variable

what happens when the sigh function is activated ?

the ventilator will deliver multiple breathes with larger tidal volumes every few minutes

what is the conditional variable of the sigh function?

time

what does the conditional variable of time in the sigh function mean

if a certain amount of time is reached then the ventilator will deliver a sigh breath (larger)

Mandatory ventilation/SIMV describe the conditional variable in this mode

If a certain time has elapsed, then a mandatory breath is delivered

SIMV

synchronized intermittent mandatory ventilation