This document discusses various modes of mechanical ventilation. It describes the goals of mechanical ventilation as safety, comfort, and liberation. The components of a breath are described as trigger, limit, and cycle. Various trigger, limit, and cycle variables are explained. Controlled mandatory ventilation is described as time-triggered with a preset tidal volume. Pressure control mode allows setting a maximum pressure level while maintaining oxygenation and ventilation. Pressure support ventilation applies a preset pressure plateau to lower the work of spontaneous breathing. Pressure regulated volume control is a closed-loop system that matches the patient's demand by regulating pressure to deliver a set tidal volume.

1. VARIOUS MODES OF
MECHANICAL
VENTILATION

2. GOALS
1. SAFETY – no VILI /CILI – acute phase
2. COMFORT – low sedation, good synchrony - stablisation
phase
3. LIBERATION – early weaning – stablisation and
recovery phase of disease

3. COMPONENTS OF BREATH
A. Start (inspiration) = TRIGGER
B. Maintain /fixed = LIMIT
C. End of inspiration =CYCLE
D. Expiration
A
B C

4. TRIGGER VARIABLES
1. Machine = time :- based on the set time interval
2. Pt – pressure / flow / neural
• Pressure - patient assisted :- based on the drop in airway
pressure
• Flow - patient assisted :- flow triggering strategy uses a
combination of continuous flow and demand flow
• Neural – newer modes (NAVA)

5. LIMIT VARIABLES
• If one of variables (pressure, volume or flow) is not allowed to
rise above a preset value during inspiratory time, it is termed a
limit variable.
• The breath delivery continues, but the variable is held at the fixed
preset value.
• TYPES-
Pressure limit
Flow limit
Volume limit

6. CYCLE VARIABLES
• A measurement that causes the end of inspiration. This
variable must be measured by the ventilator and used as
feedback signal to end inspiration and then allow
exhalation to begin.
It can be:-
Pressure-cycled
Volume-cycled
Flow-cycled
Time-cycled

8. BASICS SHAPES OF WAVEFORM
• Square
• Ramp
• Sine wave

9. SCALARS
Plotted against time( x axis)
Press-time
Flow-time
Volm-time

10. LOOPS
Plotted against volume
• Press-volm
• Flow-volm

11. CONTROLLED MANDATORY VENTILATION
(CMV)
Also known as continuous mandatory or control mode.
The ventilator delivers the preset tidal volume or pressure at a set
time interval (time-triggered frequency).
Indications: Initial stages of mechanical ventilation when patient
fights the ventilator.
DISADVANTAGES – NEED FOR EXESSIVE NMBs – cinm, muscle
atrophy

12. CHARACTERISTIC OF CONTROL MODE

13. ASSIST/CONTROL(AC)
• In assist/control(AC) mode the patient may increase the
frequency(assist) in addition to the preset mechanical
frequency(control). Each assist breath provides the preset mechanical
tidal volume.

14. Indications:
• Used to provide full ventilatory support for patients when they are first
placed on mechanical ventilation.
• Typically used for patients who have a stable respiratory drive( stable
spontaneous frequency of at least 10 to 12/min)& therefore trigger
ventilator into inspiration.
Requirement: synchrony

15. VOLUME CONTROL MODE
• Set volm is delivered with
each breath
• Volm delivery fixed,
pressure will very,
depending upon pulmonary
compliance and airway
resistance
TRIGGER – time
LIMIT – flow
CYCLE - volume

16. • Advantage – can regulate tidal
volm and minute ventilation
• Disadvantage –
1) Variable PIP based on lung
mechanics- Barotrauma

17. 2) Related to flow and sensitivity setting which may lead to pt
venti asynchrony.
Constant flow may not match pt demand.

18. PRESSURE TIME SCALAR IN VOLUME
CONTROL

20. PRESS CONTROL
• Allows clinicians to set a maximum
pressure level
• Using this mode would reduce the peak
inspiratory pressure while still
maintaining adequate oxygenation(PaO2)
and ventilation(PaCO2) therefore
reducing the risk of barotrauma in such
patients.
• The pressure controlled breaths are time
trigggered by a preset respiratory rate.
• Once inspiration begins, a pressure
plateau is created and maintained for a
preset inspiratory time.
• Pressure controlled breaths are therefore
time triggered, pressure limited and time
cycled.

21. • Decelerating flow pattern
• More comfortable for spontaneously breathing pts
• Disadvantage:
Volm delivery varies

22. PRESSURE SUPPORT VENTILATION (PSV)
• PSV is used to lower the work
of spontaneous breathing and
augment the spontaneous tidal
volume.
• PSV applies a preset pressure
plateau to the patient’s airway
for the duration of spontaneous
breathing.
1. TRIGGER - pt
2. LIMIT – pressure
3. CYCLE – flow (breath cycles
when flow reaches some
proportion of peak flow say
25%)

24. Dual Control Breath-to-Breath
pressure-limited time-cycled ventilation
Pressure Regulated Volume Control
Servo 300 Maquet Servo-i

25. PRESSURE REGULATED VOLUME CONTROL
• Closed loop system
• Matches pt.’s demand
• Ventilator measures VT delivered with VT set on the
controls. If delivered VT is less or more, ventilator
increases or decreases pressure delivered until set VT and
delivered VT are equal

26. • Delivers patient or timed
triggered, pressure-regulated
(volume controlled) and time-
cycled breaths

27. PRESSURE REGULATED VOLUME
CONTROL
• The ventilator will not allow delivered pressure to rise higher than
5 cm H2O below set upper pressure limit
Example: If upper pressure limit is set to 35 cm H2O and the ventilator
requires more than 30 cm H2O to deliver a targeted VT of 500 mL, an alarm
will sound alerting the clinician that too much pressure is being required to
deliver set volume (may be due to bronchospasm, secretions, changes in
CL, etc.)

28. PRVC
Measure VT
Compare
to set VT
Same inspiratory
pressure
 inspiratory
pressure
 inspiratory
pressure
Test breath
Less
Equal
More

29. PRVC (Pressure Regulated Volume Control)
PRVC. (1), Test breath (5 cm H2O); (2) pressure is increased to deliver set volume; (3), maximum available
pressure; (4), breath delivered at preset E, at preset f, and during preset TI; (5), when VT corresponds to set
value, pressure remains constant; (6), if preset volume increases, pressure decreases; the ventilator
continually monitors and adapts to the patient’s needs

30. PRVC (Pressure Regulated Volume Control)
• Disadvantages and Risks
• Varying mean airway pressure
• May cause or worsen auto-PEEP
• When patient demand is increased, pressure level may
diminish when support is needed
• A sudden increase in respiratory rate and demand may
result in a decrease in ventilator support

31. PRVC (Pressure Regulated Volume Control)
• Indications
• Patient who require the lowest possible
pressure and a guaranteed consistent VT
• ALI/ARDS

32. PRVC (Pressure Regulated Volume Control)
• Advantages
• Maintains a minimum PIP
• Guaranteed VT
• Decreases WOB
• Allows patient control of respiratory rate
• Decelerating flow waveform for improved gas
distribution
• Breath by breath analysis

37. THANK YOU!