OVERVIEW OF VENTILATOR MODES by Nick Mark MD ONE onepagericu.
com Link to the
most current
@nickmmark version →
Goals for mechanical ventilation:
Define treatment goals
goals (e.g. permissive hypercapnia)
1. Oxygenation – support PaO2/SpO2
If unable to achieve, can redefine
Measurement and optimization:
2. Ventilation – maintain pH
3. Patient comfort – vent synchrony, ↓ sedation ABG Pulse Ox
Choose a ventilator mode & initial 4. Facilitate weaning – minimize muscle loss,
settings promote readiness to wean from support
Measure
ABG/SpO2
/ pH PCO2 / PaO2 / HCO3 SpO2
Ventilator Modes:
Measure ABG/VBG/Spo2 Fall into two broad categories: pressure and
Ask am I achieving my goals? VENTILATION OXYGENATION
v1.0 (2020-04-03)
volume modes. Each mode has three features: Adjust If you want to change the PaO2
If you want to increase
• Trigger (T) – what initiates a breath? Settings or SpO2 adjust oxygenation
the pH ! increase the
Try a • Cycle (C) – what ends a breath? parameters (FiO2 and PEEP)
Adjust Try adjunct ventilation parameters
different • Limit (L) – what stops a breath early?
(sedation, NMB,
Settings Each mode has Pros and Cons to consider.
mode bronchodilator, etc)
Mode Description Pros Cons Major settings / example Monitor
Every breath delivered (mandatory and patient Good general-purpose mode; Requires you to Pressures
VC triggered) is the same set volume (TV) Ensures a minimum MV is monitor pressures to RR, TV, PEEP, FIO2 (Ppeak,
Volume Control achieved. Good mode for lung avoid barotrauma. Pplat)
(a.k.a. assist control T – time/pressure/flow, C – volume, L – volume protective ventilation (LPV) (See my OnePager on 12 bpm, 450cc, +8, 60%
volume) ARDS for details.) (RR – respiratory rate, TV – tidal volume)
Every breath delivered (mandatory & patient Good for limiting pressure; may Requires you to RR, IP, TI, Risetime, PEEP, FIO2 Volumes
PC triggered ) is a set pressure (IP) for a set time (Ti) be more comfortable for select monitor volumes to (TV, MV)
Pressure Control patients. Also can be used for LPV avoid volutrauma or 12 bpm, 25 cmH2O, 0.9 sec, 0.15 sec, +8, 60%
(a.k.a. assist control T - time/pressure/flow, C – time, L - pressure (no difference in mortality) hypoventilation
pressure) (IP – inspiratory pressure, TI – inspiratory time)
Hybrid PC mode that dynamically changes Guarantees TV but delivers In patients who are Pressures
PRVC inspiratory pressure to deliver a desired volume pressure-controlled breaths; (e.g. struggling (e.g. high RR, TV, TI, Risetime, Pmax, PEEP, FIO2 &
Pressure Regulated low risk of causing VILI), which WOB) this mode will volumes
Volume Control T - time/pressure/flow, C – volume, L - volume potentially may be more provide less support 12 bpm, 450cc, 0.9 sec, 0.15 sec, 30 cmH2O, +8,60%
(a.k.a. VC+, APV, comfortable for patients
Autoflow) (Pmax – maximum pressure)
Delivers mandatory breaths with a fixed volume May be useful for patients with Seldom used; not Pressure
SIMV but patient can’t trigger (patient breaths are not hiccups to avoid alkalemia effective for RR, TV, PEEP, FIO2 (Ppeak
Synchronous the same as mandatory breaths); can use PS weaning; often found Pplat)
Intermittent to be uncomfortable
Mandatory Ventilation T – time , C – volume, L - volume 12 bpm, 450 cc, +8, 60%
All breaths are patient initiated; ventilation Ideal weaning mode (used in SBTs Does not guarantee a Note that PS is Volumes
PS determined solely by patient (no backup rate). and for prolonged periods); most rate; need to monitor PS, PEEP, FiO2 above PEEP so (TV, MV)
comfortable because it allows to ensure adequate “Ten over Five”
Pressure Support PIP = 15cmH2O
T – pressure/flow, C – flow, L - pressure patient to control ventilation ventilation +10, +5, 40%
Inverse ratio ventilation (e.g. I time > E time) Great for ARDS patients who are Complex Volumes
THigh, TLow, Phigh, Plow, FIO2
APRV that allows patient to breath spontaneously; can spontaneously breathing (e.g. not mode/settings; Risk & gas
Airway Pressure combine w/ PS on NMB); may improve comfort & of VILI if settings are exchange
oxygenation (but no mortality done improperly;
5.5 sec, 0.5 sec, 25 cmH2O, 0 cmH2O, 60% PCO2 /
Release Ventilation
T – time, C – time, L - pressure benefit) doesn’t make sense if (THigh/low – time high/low, PHigh/low – pressure high/low, EtCO2
(a.k.a. Bi-Vent)
on NMB also note that Plow is analogous to PEEP)
VOLUME ASSIST/CONTROL VENTILATION by Nick Mark MD ONE onepagericu.com Link to the
most current
@nickmmark version →
How does this mode work?
• Delivers a set volume of air with each breath; patient triggered
breaths are identical to machine triggered breaths
• Time and patient triggered, volume cycled, volume limited mode
Pressure
What are the variables I set?
• RR – respiratory rate
• TV – tidal volume (better to express in terms of cc/kg PWB than ccs)
• PEEP – positive end expiratory pressure (typically at least +5)
• FiO2 – fraction of inhaled oxygen (typically at least 30%)
Flow
• V – (“v dot) inspiratory flow rate (typically 30-60 lpm) Decerating
pattern breaths
• Flow pattern – is the flow constant (e.g. takes longer
square wave) or decelerating (‘decel’)
Decel may be more comfortable but Patient
it prolongs the inspiratory phase
Volume
triggered
breath
When should I use this mode?
• Ensures that a patient receives a minimum MV
• This is a good general-purpose mode; good for providing Inhalation Exhalation I E
Lung Protective Ventilation (LPV)
• PRVC may have lower peak pressures; pressure modes
may be more comfortable for select patients
ABG: pH / PCO2 / PaO2 / HCO3
What do I need to monitor? Advanced settings
• Need to make sure the peak pressure and plateau
VENTILATION OXYGENATION I:E RATIO TRIGGER
pressure do not exceed safe limits.
→ If Pplat is too high decrease the Tv
• You will also need to monitor MV. If the patient is
triggering excessively (or auto-triggering), they can
SETTINGS: RR Tv PEEP FiO2 "̇ Flow Pattern
become alkalemic.
Choosing Initial settings EXAMPLE: bpm 12 cc/kg 6 +5 50% 40lpm Square wave Flow
• RR - Try to match the persons initial minute ventilation by Decelerating Pressure
selecting a rate to match their pre-intubation MV needs. If you want to increase If you want to increase If you want to decrease Flow trigger is
• TV - Use 8cc/kg PBW and adjust as needed. For patients the pH ! increase the the PaO2 or SpO2 Inhalation time (increase may be more
v1.0 (2020-04-09)
with ARDS (or at high risk) consider starting at 6cc/kg PBW. minute ventilation increase the FiO2 and the I:E ration) ! increase sensitive that
(MV) by changing the PEEP the inspiratory flow rate pressure; adjust
• Start with low PEEP and high FiO2 and wean to maintain to limit
RR and TV (V) and use square wave
SpO2 goal (typically > 90%). flow pattern autotriggering
WEANING FROM THE VENTILATOR by Nick Mark, MD ONE onepagericu.com Link to the
most current
@nickmmark version →
Have I fixed the cause of Daily “Wean screen” Do a spontaneous
respiratory failure? Pt should have airway reflexes
Yes
breathing trial (SBT) Combined with a Sedation
(cough, gag), require FiO2 ≤ 0.5 on Settings: PS 5 bpm, PEEP 5 cmH2O Vacation (stop sedating
(e.g. successful diuresis of a pt with
PEEP ≤ 8, breath spontaneously, for 30 min. Perform once daily. medications prior to SBT)
heart failure, effects of overdose
wore off, ARDS improving, etc) w/ stable hemodynamics (OK if on For patients with severe HF
stable dose of vasopressors) consider zero PEEP
Setting up for extubation success
• Decrease demand – correct metabolic If failure, try to
acidosis, decrease CO2 production identify root How does the patient
(fever, overfeeding, etc), reduce dead cause and try
Fail look?
space. again the next Failure if: patient looks
• Optimize mechanics - sit patient up, day. extremely distressed (anxiety,
avoid gastric distension, consider agitation) or using accessory
draining pleural effusions muscles
• Improve strength – physical therapy, Pass
wean or avoid steroids & NMB
• Respiratory drive – stop or reduce What does the monitor
long lasting pain meds, combine with show?
sedation vacation Fail
Failure if: Arrythmias including If no cuff leak present treat potential
• Optimize Nutrition – feeding w/o
tachycardia or bradycardia, airway swelling with corticosteroids
overfeeding, correct electrolyte
Hypo/Hypertension, or (methylpred 60 mg IV) then repeat test
derangements (including Mg and PO4)
Desaturation in 6 hours. Can consider extubation
• Diuresis – Dry lungs are happy lungs
Pass even if cuff leak is still absent
What does the ventilator Check for cuff leak
Fail show? Pass
Failure if consistently low TV Passing if >110 ml or <25% of
(<300) MV too high (>10 lpm) or TV lost or if audible leak is
MV too low (<2 lpm) heard
Other pro-tips
• Rapid shallow breathing index (RSBI) Pass
= freq / TV (L); RSBI >105 is a specific
but insensitive predictor of What does the ABG
extubation failure Extubate
• Drop in ScvO2 by >4.5% is a highly Fail show? (optional)
v1.0 2020-03-24
specific and fairly sensitive predictor Failure if new hypercarbia or
respiratory alkalosis Typical reintubation rate is ~10%
of extubation failure
Only check ABG on select patients. (if you are not reintubating you
are not extubating enough!)
