bipap y aprv

8/12/2019 Bipap y Aprv

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HIGHLIGHTS OF MECHANICALVENTILATION UNIT 4

Modes and initiation of ventilationBy

Elizabeth Kelley Buzbee AAS, RRT-NPS


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The modes of ventilation: A spontaneous breathis one that the patient

triggers and cycles the breath, and he controlsthe VT. This breath could be assisted by theapplication of positive pressure.

A mandatory breathis defined as one that istriggered and cycled by the machine. All

mandatory breaths are assisted breaths.


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The modes of ventilation: full

support modes CMV: continuous mandatory ventilationin which

all breaths are mandatory.

VC-CMVvolume control also called

Assist/Control mode Set VT, f to get VE; guaranteed VT

Default ventilatory mode for full support with adults

PC-CMVpressure control mode. Patient can

trigger breaths just like with A/C Set PIP, f and TI no guaranteed VT

Default ventilator mode for full support for infants


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Indications for PC: the RCP selects

pressure ventilation when:

The adult patient who cannot be managed withVC In this case, we keep the PIP less than 30cmH20.

PC results in better distribution of ventilation inpersons with unequal RAW, but consistentcompliances.

There is such an airway leak so that the VTareunstable [most common with infants and smallchildren with uncuffed ET or tracheostomy tubes]


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Compare PC to VC

In PC, the airway pressures; mPAW and PIPwill stay the same, but the VE and VT can varybased on patients time constants

In VC the VE and VT are basically stable[patient can increase f so VE could vary] thePIP and the mPAW can be altered by patient

time constants


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Compare control mode to

Assist/control We control patients by giving them sedation

and paralytic agents so that the VE we set onVC-CMV is exactly the same

We can control their PaC02 thus their acidbase balance

In A/C, the patient can trigger breaths thatwill increase the VE, so that the VE based onset VT and f could be lower than the actualmeasured VE


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Controlling the chronic

hypercapnic patient If your patient has a hypoxic drive,

administrate enough Fi02to get his Pa02between 80-100 mmHg.

This will result in apnea and works as a formof sedation in the first 24 hours.

Must wean the Fi02 to get Pa02 between 55-65 mmHg before weaning


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Problems with A/C

Excessively high PAWcan cause problems withhemodynamics once patient starts to breath.

Another problem with A/C mode is the risk ofauto-PEEP and air trapping.


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Inverse Ratio Ventilation [with

PC or with VC] This is a form of full support that uses

increased Ti to raise the mPAW whenpatients compliance is so bad that PIP andPplateau are excessive

In IRV, the expiratory time is so short that thepatient never completely exhales. This works

like PEEP to recruit alveoli


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Raising mPAW with IRV

mPAW = PIP [I] + PEEP [E]

I + E

Because we raise the inspiratory time somuch we can decrease the PIP

Because we create auto-PEEP with the shortTE, we can decrease the PEEP


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Problems with Negative pressure

Ventilation: patient must be able to:

protect airway

Handle being supine all the time

hemodynamically stable

be comfortable in one position all the time

handle being disconnected from vacuum for

short time spans


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More problems with NPV

Patient can get skin lesions from movementof body inside the device

Patient can get cold from wind Best 02 device is nasal cannula because 02

can be sucked into the neck opening


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NPV

Classified as controllers, but newer modelscan be A/C if there is a flow sensor placed onthe patients nose

Old metal iron lungs have a constant I:E of I:I;newer fiberglass devices can have altered I:Eratios


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Setting parameters on NPV:

Change level of the vacuum to increase the VT[he could use a Wrights spirometer attachedto an IPPB mask to measure exhaled V

T

]

Change the respiratory rate.


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CSV

continuous spontaneous ventilationin whichall breaths are spontaneous.

patient who can completely control his VE and only needs a little help such as with

increased baseline pressures [CPAP]

or some application of assisted breaths suchas pressure support [PS]

or who might require monitoring of VE


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Pressure support ventilation

PSV is the most common form of pressurecycled CSV.

Although this does raise the airway pressure sothat we have a higher and lower pressure, wecall this PS rather than PIP because of thespecific characteristics of PS

Flow triggered and flow cycled Patient controls his VT, f and inspiratory time


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Indications for PS:

When used with SIMV to reduce the WOB byincreasing the spontaneous VT. We generallyselect the PS that will deliver a reasonable VT

[watch the spontaneous RR] Can be used alone during weaning. Once a

patient is on a PS of 5-10 cmH20, he is

considered at a level that only compensatesfor RAW of the tubing, so is consideredconsistent with spontaneous breathing.


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PSV flow patterns

The flow pattern is descending till it reaches5 LPM [or 25% of the peak flow] in which theflow stops abruptly.

The flow slows down as the device attemptsto keep the PS at the preset pressure.


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VT on PS

There is no guaranteed VT, nor VE, but we canincrease the VT by increasing the PS pressure

We need to set VE & high f alarms closely towarn us of problems

The patient sends more air to Zone IIIbecause he is using his diaphragm more with

PS


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To choose the correct level of PSV

there are three methods: get an appropriate VT [10-15 ml/kg] and titrate the PS level toachieve this VT

increase the PS level till the respiratory rate is normalized [25

bpm or less]

increase the PSV until you decrease the work of breathingthrough the ET tube

To select the appropriate level of PSV to overcome the R

AWuse this

formula

PSV= (PIP - Pplateau) x spont insp. Flow rate [l/sec]

Ventilator flow rate [l/sec]


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PSmax

or straight pressure support or stand alone PS [PS without SIMV.] In this case, the PS is not usedas a weaning modality but for initial ofmechanical ventilation.

We generally select a PS level that will deliver 10-12 ml kg IBW.

The RCP must remember that this mode is anassist only and the patients VTand VE will vary

base on lung dynamics. There is no guaranteedVT.

Patient must have an intact ventilatory drivefor this to work


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CPAP mode

spontaneous mode

application of PEEP without any positivepressure breathes.

CPAP is merely a raised baseline with a flow rate

with adjustable Fi02 recruits alveoli which will improve diffusion of 02 CPAP can help return a low compliant lung back

to normal once atelectasis has been resolved.The FRC should rise.

should decrease WOB.

proper application of CPAP should decreaseWOB- watch respiratory rates on this


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CPAP interfaces

CPAP via the ET tube or a trach tube is calledCPAP

CPAP via a nose mask, face mask or full facemask is called nasal-CPAP [n-CPAP]

Obviously we select the interface based onthe patients ability to protect his airway


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n-CPAP indications

The successful candidate for n-CPAP would

be the patient who is oriented, has good ventilatory drive without excessive

WOB

and who has the ability to protect his airway.


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n-CPAP contraindications

Persons at risk for vomiting and aspiration

persons with skin necrosis,

claustrophobia.


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CPAP indications

Management of the person who is in hypoxemia respiratory failure.This patient will have refractory hypoxemia without respiratoryacidosis..

Treatment of Congestive Heart Failure[CHF] in the patient whohas an intact ventilatory drive and can keep his PaC02down. CPAP of8-12 with Fi02 100% is suggested. [Egans pp, 1095]

A weaning modalityThis invasive CPAP may be the last step beforeextubation. Generally a patient can be extubated from a CPAP of 5-7cmH20 [or can be extubated at a stand-alone PSV of 5-7 cmH20.

Non-invasive management of persons with obstructive sleep apnea[OSA


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APRV

a spontaneous mode

airway pressure release ventilation

Patient is breathing on two different levels ofCPAP


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Initial settings for APRV for

ARDS: The higher CPAP is set with the Phigh, while the Plowsets the

lower pressure.

The RCP should also set the time interval [Thigh] for Phighand the time interval [Tlow]for Plow

To initial APRV, the RCP looks to the patients PplateauonPPV and uses that figure for the Phigh.

The Thighis started at 4 seconds for adults and can beprogressively increased to 10-15 seconds

Set the Plow at zero and use the release time [Tlow] to keep

the pressure from dropping to zero Set the Tlow at about.5 to .8 [one time constant] so that the

breath ends with the expiratory flow at 50-75% of peak flow


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What happens if the patient

goes apnic?

During APRV ventilation if the patient wasstop breathing, the time-cycling betweenhigh and low pressures would appear similarto PC-IRV.

So this is a spontaneous mode that happensto have a back up of sorts


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Contraindications to APRV

persons with COPD or other problemsassociated with air trapping.

persons with excessively high intracranialpressures [high ICP]


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Bilevel ventilation

An alternative to APRV is bilevel ventilation.The only difference between bilevelventilationand APRVis that the patientspends more time at the [Plow] lower airwaypressure than at the high airway pressure[Phigh].


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BiPap- NIPPV

Non-invasive positive pressure ventilation

These BiPap breathes tend to be flow or time

triggered, flow cycled off with the operator selecting PIP [called IPAP]

and PEEP [called EPAP] and bleeding insupplementary 02.

The newer Visioncan get a Fi02. http://emedicine.medscape.com/article/1417959-treatment
http://emedicine.medscape.com/article/1417959-treatmenthttp://emedicine.medscape.com/article/1417959-treatmenthttp://emedicine.medscape.com/article/1417959-treatmenthttp://emedicine.medscape.com/article/1417959-treatment


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contraindications/hazards of NIPPV

do not put this device on an apnic patient because itis NOT a ventilatorit is a breath augmenter.

Persons who cannot protect their airways

Hemodynamically unstable patients Facial burns or trauma

Uncooperative patients

Persons at risk for aspiration: vomiting, nose bleeds,

unconscious, poor gag reflex

Copious secretions

Anatomical problems with gas exchange


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Indications for NIPPV: acute

care of:

congestive heart disease [n-CPAP or BiPap]

COPD patient who doesnt want to be

intubated recently extubated patient who is at risk of

failing.

immune-suppression for whom we may notwant to risk VAP


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Indications for long-term NIPPV

Long-term management of both obstructivesleep apnea and central sleep apnea

Long-term management of patients withskeletal or neuromuscular disorders

Long-term management of the COPD patientwho has s/s of chronic hypoventilation

[especially at night] and who is optimallytreated with drugs and other care.


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Initial settings for BiPap:

IPAP at 8 cmH20 and EPAP at 4 cmH20.

. Increase IPAP in increments of 2 cmH20 todeliver more VT.

To hypoxemia, increase the EPAP in incrementsof 2 cm H20.

Oddly enough, if the EPAP is raised withoutraising the IPAP, the VT might decrease becausethe VTis a function of the change in pressure orthe delta P [ P]


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The BiPap ST/D

EPAP/CPAP: in this mode, all you get is CPAP

IPAP: in this mode, again, all you get is CPAP.

Spontaneous modethis is a form of PSV in which

you select the PS with the IPAPand the PEEP withthe EPAP. All breaths are patient triggered

Spontaneous/timed: is their version of A/C PCwith each breath patient or time triggered. In this

mode you select the bpm Timed mode: their version of control ventilation

in which you now select the rate and theinspiratory time


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What is so strange about the

BiPAP ST/D circuit? only a single, large-bore tubing going from

the compressor to the patients mask.

constant leak at the Whisper swivel thiswill leak a minimal amount of gas out of thecircuit and between the very high flow rates

and the leak, the patient doesnt rebreathehis C02. Never plug up this hole!


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Adding extra 02to the BiPap STD

without starting a fire

add 02at the mask,

start machine first before adding 02so gaswill not leak back into machine

never exceed 15 LPM


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Compare the BiPap STD to the Vision

BiPap machine

The BiPAP ST/D has no 02inlet

The Respironics Visionplugs into 50 psig 02&can get 21% to 100% Fi0

2

The BiPAP ST/D has no internal alarm, youmust buy a separate alarm

The Respironics Visioncan be used forinvasive ventilation with A/C, SIMV +PSV andCPAP as well as NIPPV [CPAP and S/T]


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Use of critical care ventilators such as

BiPap machines in the ICU.

As a rule, we would operate these machinesin the PSV mode with PEEP to mimic theBiPap.

It is important to understand that the alarmson these machines may have to be adjusted

out of range


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Dual modes

combinemandatory ventilation withspontaneous ventilation

IMV:intermittent mandatory ventilation: inwhich some breaths are mandatory and

others are spontaneous. In this type of breath, the ventilator will give

a PPV usually based on VC at timed intervals.The patient can breathe off a constant flowrate or from a demand valve at a VT and flowrate determined by his muscle strength,ventilatory drive and lung mechanics.


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Advantages of IMV/ SIMV

patient comfort

maintains muscle coordination & musclestrength

reduces V/Q mismatch;Zone III is beingutilized,

[4] lower PAW and is an excellent weaning

modality less likely to cause air-trapping


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Disadvantage of IMV/ SIMV:

If the patients PPV support is removed tooquickly the patient can suffer increased WOB

We need to monitor the spontaneous VE , RRand VT, we may need to increase support by:

increasing the SIMV rate

adding PS


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Indications for IMV/SIMV:

IMV is a partial mode of ventilation thatusually includes dual modes.

weaning from CMV when the patients

ventilator muscles are weakened an initial ventilatorsetting when the patient is

at risk for air trapping and is breathing on hisown,

or if the patient who is able to breathe partiallyfor himself is at risk for decreased CO.


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The difference between SIMV and IMV:

SIMV stands for synchronized intermittentmandatory ventilation.

The mandatory breath can come in sooner ifpatient triggers within the synchronizationwindowof fractions of seconds.


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In apressure regulated volume controlmode,we are attempting to deliver the VT[becausewe are in VC mode] but we want to keep the

airway pressures low.

ventilator will attempt to deliver the VTat 5

cmH20 below a preset pressure setting.

Special modes: PRVC

PRVC


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Special modes: VAPS

volume assured, pressure support,the ventilatorwill be attempting to deliver a stable VTwith PSbreaths so that the patient has the advantage of

stable VEas well as the advantages of If a PS breath fails to reach the pre-set VT, the

breath will continue at a constant flow until thevolume is reached. If the patient got the pre-set VT

with the PS breath, it stays PS. Unlike normal PS, these breaths arent just flow

triggered, but can be time triggered.


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Special modes: MMV

Mandatory minute ventilation gives the patient extra breaths or extra PS

pressure to keep a predetermined minimal VE.

This differs from apnea parameters in thatthe patient doesnt have to actually go apneic

for 20 seconds or more for this to activate. Hemerely needs to have hypoventilation.


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One problem with MMV

when the patient starts the rapid, shallowbreathing associated with respiratorydistress.

If a patient keeps the VEup with rate only, hecan be in a lot of distress

It is suggested to keep the maximal high

respiratory rate 10 BPM above the average


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Special modes: ASV adaptive support ventilation: the RCP inputs

the patients IBW and a percentage of the VE.

The ventilator will deliver a VEbased on thepatients IBW.

As the patient takes over more of the breathingthe VE is maintained with PS breaths.

The level of PS changes to give the VT calculated

by the machine, The VT will be determined bythe patients IBW and VD ventilation.


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Special modes: PAV

In proportional assist ventilation modesimilar to ASV in that the ventilator willcollect data about patients elasticity and

resistance and flow or volume demands inorder to arrive at PS levels that varies.


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High frequency ventilation

controlled ventilation- the patient is sedatedand paralyzed

VT of less or equal to the VDanatomical

respiratory frequencies of 60 BPM-3600 bpm

All HFV counts on the gas stream going downthe ET tube (inside) AT THE SAME TIME andthe gas flow existing (outside stream).


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How does HFV work

Penduluft action due to various timeconstants of different portions of the lungs,the gas moves from one lobe to another ,

there is some bulk transfer


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What are the types of HFV

high frequency jet ventilation

high frequency positive pressure

ventilation

high frequency oscillation

combination of HFJ with CMV


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Special modes: PRVC

Inpressure regulated volume control, aneffort is made to maintain both a safe levelof airway pressure and delivered V

T

.

In PRVC, the RCP selects a PIP that willnot be exceeded.

To keep the VT, at this safe PIP, the

inspiratory time and the flow rate mustvary.


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Special modes:Auto-mode:

in some ventilators selection of the auto-mode will allow the ventilator to decreasesupport as a patient starts to take over the

WOB.

The ventilator reverts between a CMV modeand a spontaneous mode based on breath by

breath assessment of the patient


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Special modes: ATC

Automatic tubing compensation, in thismode the ventilator will compensate for theRAW of the ET tube.


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INITIAL VENTILATOR SETTINGS


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VT, set f and VE

Full support A/C or SIMV rate 12-16 BPM

Partial support SIMV below 10 BPM

8-10 ml/Kg IBW normal lungs

6-8 ml/kg IBW asthma

5-8 ml/ kg IBW for ARDS & COPD

VE needs to be 80-100 ml/KgIBW


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TI and Flow rates

Inspiratory flow ratesof 60-80 LPM for most

If air hungry raise above 80

COPD- 60-100 LPM

Inspiratory times .80-1.2 seconds


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Flow wave pattern

Constant flowswill decrease inspiratory timeand help with I:E ratios, but can raise the PIP.

Descendingflow curve has the advantage ofbetter distribution of gas into the lung, butwill increase the TIand increase the mPAW

Sine wave: while considered more

physiological, a classic sine wave may nothave enough initial flow to satisfy a patient.Like the descending flow pattern it will raise

the TIand change the I:E ratio


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Rise time or Ramp

: in an effort to fine-tune flow patterns, theconstant flow can be damped by a rise timeadjustments. When set high, this almost

mimics an ascending flow pattern.


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Inspiratory pause

The temporary use of the inspiratory pauseat about .5 to 1 second is generally reservedfor gathering Pplateau


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Fi02

100% is a good place to

Weaning rapidly to 40-50% after ABG

Fi02 needs to be weaned about 20% at a step.


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PEEP

may be started at zero, PEEP at 5 or lesscmH20 is considered physiologicaland shouldnot result in CV problems-but-- remember

any PEEP that causes hemodynamicproblems is excessive.

Increase or decrease by units of 2


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Humidification by HME

is limited to persons with good fluid balances,normal secretions and VEless than 10 LPMand normal body temperatures.

If the patient has a gross leak so that 30% ofthe delivered VTis lost, the HME will notwork.


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Humidification by heated

humidifier can be used with everyone but are necessaryfor patients with secretions. Keep thetemperatures close to 330C +/- 2


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Sighs:

multiple sighs every hour or so. These sighvolumes were about 1.5 x the VT.

important if VT is less than 7 ml/kg


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s/p lung resection or lung

transplants

need lower VTand faster rates to protect the

torn lung from rupture. Keep the Pplateauat or below 30 cmH20 [old

Egans 1011]


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lobar pneumonia:

place patient on the good lung sideso gas goesto the bad lung

avoid PEEP in lobar pneumonia if possible

Try to prolong the Ti

Consider double lumen ET tube so we can settwo ventilators on the patient


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long-term neuromuscular

patients more comfortable at higher than usual VT[decrease the RR] of 10-12 ml/kg. Thesepatients also tend to want higher flow rates.

They can be managed with low Fi02-even .21as long as Sp02 is above 90-92%

low PEEP of 3-5 to prevent atelectasis are ok


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Persons with Congestive

Heart failure We can start with normal settings, but if thePIP and Pplateauare excessive, we need todecrease the VT

PEEP at 10 cmH20 and wean the

Once the patients compliance gets better, wemust wean the PEEP

If the patient has an intact ventilatory drive, &good VE, he could be maintained on CPAP


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Initial parameters when High RAW

is an issue?

start with SIMV because this mode is lesslikely to cause air trapping.

minimize air trapping and auto-PEEP


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COPD SIMV rate between 10-12 BPM : decrease this to 6-8 to

allow time to exhale start at 60 and raise to100 LPM].

A COPD patient can be started at 40-50% Fi02

Use of PEEP with COPD is dangerous, but if the set PEEP

and the auto-PEEP are kept about the same, the gas ismore likely to leave the lung

, keep Sp02 at 90-92% and keep the PaC02and pH closeto baseline so the patient will not sufferpost-hypercapnic

alkalosis

A th ti [AHI 2005 CPR CPG IV 141]


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Asthmatic [AHI 2005 CPR CPG pp IV 141]

Alert? may do well on BiPap machine

SIMV rate 6-10 BPM

VTof 6-8 ml/ kg IBW

80-100 LPM with a descending flow pattern to

get 1:4 or 1:5 Start Fi02 at 100%.

Use of PEEP with asthmatics is dangerous, but if

the set PEEP and the auto-PEEP are kept thesame, the gas is more likely to leave the lung.

permissive hypercapnia,

bipap y aprv

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