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Assignment 11

Egan chapter 45 1007 to 1010


Pilbeam mechanical vent chapter 9 151 to 155, WB 81 to 84

Dual control modes

VAPS" volume assured pressure supported, set volume and pressure is variable, The base is PSVVolume support: varialbe pressure support

PRVC, pressure regulated, volume controlled

you set the target volume and the pressure moves

Dual control breaths

Volume assured pressure support


:This mode allows a feedback loop based on the volum


Volume assured pressure support

RT adjusts the vent with these settings


:Pressure limit = plateau seen during a volume breath


:Ventilator rate


:Peak flow (the flow if V(T) is less than target)


:PEEP


:FiO2


:Trigger sensitivity


:minimum V(T)


Volume assured pressure support

If pressure is too high, all breaths are pressure limited


If the peak flow setting is too high, all breaths will be volume controlled


Volume assured pressure support

If peak flow set too low


:the switch from ressure to volume is late in the breath


:inspiratory time is too long


Comparing VAPS and AC volume ventilation


:Lower WOB


:Lower Raw


Less Peep(i)


Dual control breaths

Volume support: pressure limited flow variable ventilation


:V(T) is used as feedback control to adjust the pressure support level


:all breaths are patient triggered, pressure support, and flow variable


Automatic weaning of pressure support as long as tidal volume matches minimu required V(T)


:V(T) set in a feedback loop to adjust

Volume support ventilation vs Volume assured pressure supported


How does colume suppor tdiffer from VAPS?


:In volume support: adjusts pressure so that within a few breaths, desired V(T) is reached


:In VAPS, we are amining for desired V(T)


::Volume is added to the end of a breath is a pressure limited breath is going to fail to achieve V(T)


Volume support

Spontaneous mode


Delivers a patient triggered (pressure or flow), pressure targeted, flow generated breath


:Can also be timed cycled (if T(I) is extedned for some reason) or pressure cycled (if pressure rises too high)

Volume support

Similar to rpessure support except VS also targets set (V(t)


:It adjusts pressure (up or down) to ach9eve the set volume


:The maximum pressure change is less than 3 cm H2O and ranges from 0 cmh20 to 5 cm h2 below the high pressure alarm setting


Weaning mode of vent


:Patients who are breathing spontanteously


:But cannot do all the WOB


Volume support

LIttle data to show it actually works


If PSV level increases to maintain V(T) in patient with increases R(AW), Peep(I) may increases


If minimum V(T) set too high, weaning may be delayed


VOlume support

Indiacations


:Spontanous breathing patient who require minimum V(E)



Advantages


:Guarantess Vt and Ve


:PSV breaths using lowest required pressure


:Decreases the patients RR


:Decreases patients WOB


:allows patient control of I:E time


:Breath by breath analysis


:Variable V(T) to mee tthe patients demand


Volume support VS


Disadvantages


:spontaneous ventilation required, VT selected may be too large or small for patient, varying mean airway pressures


:Auto peep may affect vent response to aptient need


:A sudden increase in RR and flow may result in a decrease in vent support


Dual control breaths

Pressure regulated volume control (PRVC) delivers patient or timed triggered, pressure targeted controlled and time cycled breaths


Ventilator measures (VT) delivered with VT set on the controls, If delivered VT is less or more, ventilator increaes or decreases pressure delivered until set VT an delivered VT are equal


Pressure regulated volume control (PRVC)

The ventil will not allow delivered pressure to rise higher than 5 cmh20 elow set upper pressure lmit


:If upper pressure limit is set to 35 cmh20 and the vent requires more than 30 cmh20 to deliver a targeted VT or 500 ml, an alarm will sound


:Therefore, too much pressure is being required to deliver VT (may be due to bronchospasm, secretions, changes in CL)

PRVC

Indications


:Patients who require the lowest possible pressure and a guranteed consistent V(T)


:ALI/ARDS


:Patients requiring high and or varialbe V(T), PIP or T(I)


:Patient with the possibility of CL or Raw changes


PRVC

Advantages


:Maintains a miminum PIP


:Guaranteed VT and VE


:Patient has very little WOB requirement


:Variable VE to meet patient demand


:Decelerating flow waveform for improed has distribution


PRVC

Disadvantages


:Varying mean airway pressure


:May cause or worsen auto PEEP


:When patient demand is increased, pressure level may diminish when support is needed


:May be tolereated poorly in awake non sedated patients


:A sudden episode of tachypnea and increased demand may result in a decrease in vent support

Adaptive support ventilaition (ASV)

Dual control mode that uses pressure ventl


:Utilizes PCV and PSV to maintain a set minimum V(E) (volume target)


:uses least required P for minimal WOB


:Dependent patients condition and effort


::Automatically adapts to patient demand by increasing or decreasing support, depending on the patients elastic and resistive loads


Adaptive support ventilation

RCP enters the patients IBW, which allows the vent algorith to choose a require Ve


:the vent then delivers 100 ml/min/kg


A series of test breaths meausre the system C, Raw, and auto peep


If no spontatnous effort occurs


:The vent determines the appropriate respiratory rate, VT, and pressure limit


:Delivered for the mandatory breaths


Adaptive support vent (ASV)


IE ratio and T(I) of the mandatory breaths are continually being optimized by the ventialtor to prevent auto peep


If the patient beings having spontaneous efforts, the number of mandatory breaths derease the the vent switches to PSV at the same pressure level. patient controls their own I time an flow


Pressure limits for both mandatory and spontanous breahts are always being automatically adjusted to meet the VE target


ASV

Indications


:Full or patieal vent support


:Patient requiring a lowest possible PIP and a guaranteed V(T)


:ALI/ARDS


:Patient requireing high and or variable rate



Indications


:Patients not breathing spontaneously and not triggering the vent


:Patient with possiblity of work land changes (CL and RAW)


:Facilitiates weaning


Advantages of ASV

Guaranteed VT and VE


Minimal patient WOB


Vent adapts to the patient


:Meet patient demand


Weaning is done auto and continuously


Decelerating flow waveform or increase gas distribution

ASV disadavantages and risks

Inability to recognize and adjust to changes in alveolar V(D)


Possible respiratory muscle atrophy


Varying mean airway pressure


In patients with COPD, a longer TE may be required


A suddend increase in RR and demand may reselt in blank

Auto mode

The vent switches etween mandatory and spontaneous breahing modes


Combines


:Volume support and


: pressure regulated volume control (PRVC)


If patient is paralyzing, the vent will provide PRVC


;aLL BREATHS ARE MANDATORY THAT ARE VENT TRIGGERED, PRESSURE CONTROLLED AND TIME CYCLED, THE PRESSURE IA DJUSTED TO MAINTAIN THE SET VT


Automode

If the patient breaths spontaneous for two consecutive breaths


:The vent switches to VS


:All breaths are patient triggered, rpessure lmimited and flow cycled


If the patient bcomes apneic for 12 seconds then


:The vent switches back to PRVC

Mandatory minute ventilation MMV

Minimum minute ventilation or augmented minute ventilation


MInimum Ve which usually is 70 to 90% of patients current VE


:Vent provides whatever part of the VE that the patient is unable to accomplish


:The backup rate is increased or preset pressure in increased

Mandatory minute vent MMV

Similar to PSV


:PS level is not set, but is automatically varaible according to the patients need


:decrased VE leads to increase PSV


MMV indications

Patients who spontaneously breath and ready to wean, or


Variable ventilatory drive


Advantages


:Full or partial vent support


:Spontaneous and manadatory ventilation


:Patients V(E) remains stable


:Prevents hypoventilation

MMV

Disadvantages


:An adequate VvE may not equal sufficient (EG rapid shallow breathing)


:The high rate alarm must be set low enough to alert clinician of rapid shallow breathing


:Variable mean airway pressure

Mandatory minute ventilation MMV

Disadvantages


:An adequate preset V(E)


(greater spontaneous VE) can lead to inadequate support and patient fatigue


An excessive set VE


:

Proportional assist ventilation PAV

Provides pressure, flow assist and volume assist in proportion to the patients spontaneous effort


:The greater the patients effort then the more the vent flow, volume and pressure: proportional

PAV

The operator sets


:vent volume and fllow assist


:Approximately 80% of the patients elastance and resistance


The vent then generates proportional flow and volume assist to augment the patients own effort



Indications


:Patients who have increase WOB associated with decrease CL


:asynchornous patients who are stable and have inspiratory effort


:Ventilator dependant patients



Advantages


:The patient controls vent variables (PIP, Ti, Te, Vt)


:Trends the changes of vventilatory effort


:With CPAP, inspiratory muscle work is near normal


::May decrese or prevent muscle atrophyLowers airway pressure


y



yLowers airway pressure


Lowers airway pressure


PAV proportionall assist vent

Disadvanteges


:patient must have an adequate spontaneous respirtaootyr drive


Variable Vt and or PIP


CL and RAW is essential


Inaccurate estimates of CL and RAW during ventlaot setup may significalntly impair proper synchyrony



The pressure delivered from the vent can exceed the pressure needed to overcome the system impedance (CL and RAW)


Air leak could cause automatic cycling


Trigger effort may increase with auto peep