ADVANCED VENT FINAL REVIEW

Waveform

is a shape

Scalar

shape graphed over time

Loop

pressure or flow graphed over volume

When do you suspect auto-PEEP?

Look at flow/time scalar and assess exhalation 

Trigger Assynchrony- Auto Triggering

Premature initiation of a breath independent of time or pt effort

• possible in all current triggering methods

Trigger Asynchrony- Auto Triggering is caused by

• random noise in the circuit 

• water in the circuit 

• leaks 

• cardiogenic oscillations

PRVC

is a dual control mode

Volume guarantee of VC- user sets a target tidal volume

PRVC is

Pressure safety of PC in PRVC

self regulates PIP from one breath tot he next based on the exhaled tidal volume( vtexh ) of the previous 3 breaths 

• ventilator uses Vtexh as feedback to control a continuously adjust pressure limit

Settings and alarms in PRVC

• Tidal volume 

• Inspiratory time 

• Respiratory time 

• Rise time 

• PEEP

• FiO2

• Trigger variable 

• High pressure limit alarm 

Waveforms in PRVC

DRE

Pressure Time: Rectangular 

Flow/Time: Decelerating 

Volume/Time: Exponential Rise

Classifications in PRVC

• Trime triggered- may also be pt triggered 

• Time cycled 

• Volume targeted

PRVC uses constant

pressure during the entire inspiration phase

( just like pressure control )

PRVC max available pressure

5 cmH20 below the preset upper pressure alarm limit

PRVC minimum inspiratory pressure limit

baseline setting ( PEEP )

Advantages of PRVC

• maintains a minimum PIP

• guaranteed Vt and Minute Ventilation ( Ve) - allows pt to control Ve

• Pt has a very little WOB requirement 

• Pt can trigger additional breaths above the set RR

• Variable inspiratory flow to meet pt demand 

• decelerating flow waveform improved gas distribution

• breath by breath analysis

Disadvantages of PRVC

• Upper pressure limit must be set appropriately 

• Usually available in AC mode ( some vents allow it in SIMV ) 

• May cause or worsen auto- PEEP

• Varying Mean Airway Pressure 

• May be tolerated poorly in awake non-sedated patients, especially if low tidal volumes are used 

Grande Disadvantage #1 of PRVC

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

• pressure waveform should be square… if not increase the set tidal volume or switch to an alternative mode of ventilation 

Grande Disadvantage #2 of PRVC

A sudden increase in RR and demand may result in a decrease in ventilator support 

Grande Disadvantage #3 of PRVC

Patients who assist the ventilator by taking larger Vt will cause inspiratory pressure to drop. If pt then tires, PIP may drop to PEEP and will not provide adequate support immediately

APRV

P- high

VC- Pplat

PC- Set pressure

Should not exceed 30

APRV

P- Low

0

APRV

T-high

minium

4

APRV

T- High

maximum during weaning 

12-15

APRV

T- Low

0.2-0.8

( mostly 0.6- 0.8 )

APRV

Sync window from P high to P low

0.25-.30 seconds

APRV provides two levels of 

continuous positive

• airway pressure CPAP and allow spontaneous breathing at both levels 

Two pressure levels are essentially pressure control and peep

P- High and P-low

Two time periods are essentially I-time and E-time

T high and T low

Hypoxemia in APRV

encourage recruitment and increase MAP

• create more auto-PEEP

• increase P-high 

• Apply PEEP

Hypercapnia in APRV

Increase Minute Ventilation

• Reduce TCT

• Increase P-high 

• Increase Delta P ( P-high and P-low ) 

• increase T-low- this would allow for longer time in exhalation 

• at what cost? de recruitment 

Weaning in APRV method

Drop and Stretch Method

Drop and Stretch Method

• Gradually reduces the P-high ( drop )

• Gradually reduce the number of releases by extending the T-high ( stretch) until the mode is converted to CPAP

Drop and Stretch method

P High is reduced in

2-3 cm H2O increments

Drop and Stretch method

T- High is lenghthed in 

0.5-2 sec increments 

In Drop and Stretch method

the p-low can be elevated slightly

• PS may be added to compensate 

Volume Support Ventilation is like

PRVC

In VSV

The ventilator gives a test breath with an inspiratory pressure that is 10 cm H20 above PEEP 

• it measures the Vt delivered and compliance 

• for each subsequent breath, the ventilator calculates compliance and adjusts pressure support level to ensure the set Vt is achieved 

• the vent will not change insp pressure more than 3 cm H2O from one breath to the next

• the maximum available support 5 cm H20 below the upper pressure limit 

• the minimum pressure setting is the baseline setting + 1.5 cm H20

Proportional Assist Ventilation amplifies

muscular effort

PAV

muscular effort ( Pmus ) and airway pressure assistance ( Paw ) are better matched for PAV than for PSV

ATC- automatic tube compensation is NOT

a mode but a feature

ATC delivers the

exact amount of pressure required to overcome resistive load imposed by the ETT for the flow measured at the time 

ATC Advantages

• addresses the vent support need to compensate for artificial airway 

• superior to PS for compensation of resistance of artificial airway 

• supports inspiration as well as expiration 

ATC Disadvantages

Adding ATC to PS may result in over assist

Mandatory Minute Ventilation is also known as

• minimum minute ventilation

• augmented minute ventilation

In MMV the operator sets a minimum minute ventilation of

70-90% of patients current minute ventilation ( MV )

In mandatory minute ventilation the vent provides

whatever part of the MV that the pt is unable to accomplish

• accomplished by increasing the breathing rate or the preset pressure 

Adaptive Support Ventilation recommended starting %

100%

In Adaptive support ventilation the clinician can adjust targeted ventilation based on:

Decreased Vent need:

< 100% of targeted minute ventilation 

• weaning 

In Adaptive support ventilation the clinician can adjust targeted ventilation based on:

Increased vent need:

>100% of targeted minute ventilation

• sepsis

ASV how does it work?

Need to determine Optimal breath frequency

• vent delivers a test breath

• to determine expiratory time constant ETC

• ETC used with estimated dead space volume and calculated minute ventilation 

• To calculate optimal breath frequency

• tries to ensure delivery of acceptable minute ventilation  

Optimal Vt=

calculated minute ventilation divded by optimal breath frequency 

Closed Loop in ASV

increases or decreases support based on ( monitored parameters )

• pressure

• flow

• inspiratory and exp time 

• compliance and resistance 

• time constants

Measurement of drive to breath 

p 0.1 or p 100

measurement of airway occlusion pressure 

• airway is occluded during first 100 milliseconds 

• reflects drive to breath and ventilator muscle strength 

Normal range for P 0.1 or P 100

0 to -2 cmH2O 

• pt is breathing comfortably 

Values below -6 cmH20 means

a high drive to breath and weaning is not likely to succeed

Value greater than 0 means

strong resp muscles and vigorous respiratory drive

Ramsay sedation scale Level one

patient is anxious and agitated or less or both

Ramsay sedation scale Level Two

Patient is co-operative, oriented and trnaquil

Ramsay sedation scale Level Three

Patient responds to commands only

Ramsay sedation scale Level Four

Patient exhibits brisk response to light glabellar tap or loud auditory stimulus

Ramsay sedation scale Level Five

Patient exhibits sluggish response to light glabellar tap or loud auditory stimulus

Ramsay sedation scale Level Six

Patient exhibits no response to light glabellar tap or loud auditory stimulus

Drug of choice for the ICU

benzos

Benzos binds to

Y- aminobutyric acid GABA receptor complex

Benzos have a potency, onset uptake and distribution affected by:

• age 

• underlying pathology 

• concurrent drug therapy 

• renal insufficiency 

• hepatic insufficiency 

Reversal Drug for Benzodiazepine

Romazicon ( flumazenil )

Reversal Drug for Opiate

Narcan ( naloxone )

Paralytic neuromuscular blockade

chemically paralyzes patients- not sedative or analgesic

Depolarizing agents 

Bind to acetylcholine receptors and causes prolonged depolarization of motor endplate 

• binds and activates- over and over again ——— desensitized 

Nondepolarizing agents

Bind to acetylcholine receptors but cause paralysis by competitively inhibiting action of acetylcholine at the neuromuscular junction

A paralytic helps

with invasive procedures ( intubation )

• prevents movements

• stabilize airway 

advanced strategies during mechanical ventilation

Antibiotics

Penicillin – Ampicillin, Amoxicillin, Nafcillin
• Cephalosporins – Cephalexin, Cefazolin
• Aminoglycosides – Amikacin, Gentamicin, Tobramycin (TOBI)
• Used for gram-negative coverage and usually used concurrently with another drug
• Fluoroquinolones – Levofloxacin, Ciprofloxacin
• Broad spectrum coverage for respiratory, urinary tract, and abdominal infections

Penicillin 

• Ampicillin 

• amoxicillin 

• nafcillin 

Cephalosporins 

• cephalexin 

• cefazolin 

Aminoglycosides

• amikacin

• gentamicin

• tobramycin ( TOBI ) 

Aminoglycosides are used for

gram negative coverage and usually used concurrently with another drug

Fluoroquinolones 

• Levofloxacin

• Ciprofloxacin

Fluoroquinolones is used for

a broad spectrum coverage for respiratory, urinary tract and abdominal infections

Antibiotics

Vancomycin and protein synthesis inhibitors- erythromycin and azithromycin

Vancomycin

indicated for serious life threatening infections by gram positive cocci

• most effected antibiotic to treat MRSA 

Protein synthesis inhibitors- erythromycin, azithromycin

used to treat pulmonary infections