The document outlines the essentials of mechanical ventilation, focusing on various modes, terminologies, and classifications. It discusses basic and advanced ventilator modes, including control mode ventilation, assist mode ventilation, and synchronous intermittent mandatory ventilation (SIMV), detailing their mechanics, indications, advantages, and disadvantages. Key phase variables such as trigger, limit, and cycle are described, providing a comprehensive understanding of how ventilators function in supporting patients' respiratory needs.

1. BASICS OF MECHANICAL
VENTILATION
PART - II
Dr. Tapas Ghose, MD
School of Digestive & Liver Diseases
IPGME & R, Kolkata

2. Understanding basic ventilator
Modes

3. Core Concepts:
What is a ventilator Mode?

4. • A ventilator mode can be thought of as a
classification based on how to control the
ventilator breath.
• Traditionally ventilators were classified based on
how they determined when to stop giving a
breath.

5. Basic Terminology
• Trigger-
– variable which initiates inspiration
• Limit:
– variable which limits the volume of inspiratory gas
• Cycle:
– Variable which determines cycling of inspiration to
expiration
• Remember “TLC”

6. • All ventilatory modes can be described using 4
phase variables:
– Time
– Pressure
– Flow
– Volume

7. Ventilator classifications
• Positive and negative pressure ventilators
• Pressure and flow generators
• Hand controlled ventilators
– Manual self inflatable resuscitator bag
– Continuous flow anaesthesia bag
• Mechanical ventilators
– Gas powered
– Electric powered
– combined

8. Basic ventilator modes
• Control mode ventilation
• Assist mode ventilation
• Assist/control mode ventilation
• Intermittent mandatory ventilation
• Pressure support ventilation
• PEEP
• CPAP
• Mandatory minute ventilation (MMV)

9. Advanced Ventilation modes
• High frequency ventilation
• Airway pressure release ventilation
• Inverse ratio ventilation
• Continuous flow apneic ventilation
• Differential lung ventilation
• Proportional assist ventilation
• Neurally adjusted ventilatory assist (NAVA)
• Extracorporeal membrane oxygenation

10. Describing a ventilatory mode
• Name , basic/advanced mode
• Type- control, assist, partial assist, spontaneous
• Phase variables
• Mechanics
• Clinical indications
• Advantages
• Disadvantages
• Graphics

11. Control Mode Ventilation
• Basic mode- volume preset, patient does not
participate in any phase of the ventilation cycle.
• Time triggered, volume limited, time/volume
cycled.
• Full support mode– hence advantageous in
critically ill patients who require a guaranteed
minute ventilation
• Reduces respiratory WOB and minimizes
oxygen consumption of respiratory muscles

12. • Used in
– After 1st intubation, prior to full evaluation
– Patients who require high minute ventilation
– Patients with unstable respiratory drives
– Patients with respiratory muscle fatigue
– Patients with poor cardiac output to reduce oxygen
consumption of resp. muscles
• Two modes– volume cycled, pressure cycled
Control Mode Ventilation

13. • Problems
– Dysphoric to the patient as he cannot participate in
the ventilatory process. Requires sedation and
paralysis resulting in intentional overventilation,
alkalosis, apnea during disconnection
– This mode is unresponsive to patient’s changing
minute ventilation demands. Requires intensive
monitoring
– makes respiratory muscles prone to atrophy.
Control Mode Ventilation

14. Controlled Mode
(Volume-Targeted Ventilation)
Preset VT
Volume Cycling
Dependent on
CL & Raw
Time (sec)
Flow
(L/m)
Pressure
(cm H2O)
Volume
(mL)
Preset Peak Flow
Time triggered, Flow limited, Volume cycled Ventilation

15. Controlled Mode (Pressure-Targeted
Ventilation)
Press
ure
Flow
Volume
(L/min)
(cm H2O)
(ml)
Time (sec)
Time-Cycled
Set PC level
Time Triggered, Pressure Limited, Time Cycled Ventilation

16. Assist Mode Ventilation
• Basic mode, patient participates only during triggering
machine breath.
• Pressure/flow triggered, volume/pressure limited,
volume/time cycled.
• Patients participate in process of breathing but do not
contribute to WOB- better tolerated than CMV
• May result in apnea if patient is unable to trigger a
breath
• Not used in ITUs anymore, but is conventional in Ors.

17. Assisted Mode
(Volume-Targeted Ventilation)
Time (sec)
Flow
(L/m)
Pressure
(cm H2O)
Volume
(mL)
Preset VT
Volume Cycling
Patient triggered, Flow limited, Volume cycled Ventilation

18. Pressure Control ventilation
• Basic Mode, independent of patient effort.
• Time triggered, pressure limited, time cycled.
• Since it is time cycled, allows for any I:E setting.
Suitable for IRV.
• Less chance of barotrauma because PIP is
preset.
• Does not guarantee delivery of fixed tidal
volume.

19. Controlled Mode (Pressure-Targeted
Ventilation)
Press
ure
Flow
Volume
(L/min)
(cm H2O)
(ml)
Time (sec)
Time-Cycled
Set PC level
Time Triggered, Pressure Limited, Time Cycled Ventilation

20. Assist/Control Mode ventilation
• Basic mode. Bimodal form of ventilation where
ventilator works in assist mode when patient’s rate is
higher than preset ‘backup’ rate and goes into control
mode when trigger falls below it.
• Time/pressure triggered, volume/pressure limited,
volume/time cycled.
• Patients can adjust their ventilatory needs provided they
have an intact respiratory drive and muscle strength
• ‘Backup rate’ is a safety feature. Should be set at 80 %
of initial patient rate/ minute ventilation

21. • ‘Backup rate’ should be set above respiratory
rate if
– Patient’s drive is unstable
– Tight control of pH or PaCO2 is required
– In patients with flail chest
• Respiratory muscles continue to consume
oxygen and contribute to WOB
Assist/Control Mode ventilation

22. • Problems
– Patients respiratory rate increases mean intrathoracic
pressures which in turn decreases cardiac output. An
assist rate above 16 is associated with AutoPEEP
– Results in more barotrauma associated lung injury
– May produce alkalemia in patients with high
respiratory drives
Assist/Control Mode ventilation

23. Assisted vs Controlled
Time (sec)
Assisted Controlled
Pressure
(cmH20)

24. Synchronous Intermittent Mandatory
Ventilation (SIMV)
• Basic Mode. Allows spontaneous ventilations through a
continuous flow device. Machine breaths are delivered
at preset time intervals. Machine breaths are
synchronized with patient’s efforts.
• Time/pressure triggered, Volume/pressure limited,
volume/time cycled + spontaneous ventilation
• Total support, full support and partial support can be
provided.
• Usually used along with PSV to support spontaneous
breaths.

25. • Weaning is a controlled and gradual process
• Advantages:
– Avoidance of respiratory alkalosis
– Decreased requirement of sedation/paralysis. Better
tolerated
– Lower mean airway pressures
– Better ventilation and perfusion matching
– Expedited weaning
– Prevention of resp. muscle atrophy
Synchronous Intermittent Mandatory
Ventilation (SIMV)

26. • Problems
– Increased risk of CO2 retention
– Increased WOB
– Respiratory muscle fatigue
– Prolongation of weaning
– Chances of cardiac decompensation
Synchronous Intermittent Mandatory
Ventilation (SIMV)

27. SIMV
(Volume-Targeted Ventilation)
Spontaneous Breaths
Flow
(L/m)
Pressure
(cm H2O)
Volume
(mL)

28. THANK YOU FOR YOUR
PATIENT HEARING. . . . .