Mechanical ventilation involves the artificial ventilation of the lungs, primarily using a ventilator to maintain gas exchange and improve oxygenation, while also easing the work of breathing. Indications for mechanical ventilation include acute respiratory failure, pulmonary gas exchange abnormalities, and complications post-anesthesia or cardiac arrest. Different modes of mechanical ventilation exist, such as volume and pressure controls, which have specific clinical applications and operational parameters.

1. Mechanical Ventilation
Mechanical Ventilation
Dr. R.BRINDHA MD
Dr. R.BRINDHA MD
Assistant Professor
Assistant Professor
Anaesthesiology
Anaesthesiology

2. • Mechanical Ventilation is ventilation
Mechanical Ventilation is ventilation
of the lungs by artificial means
of the lungs by artificial means
usually by a
usually by a ventilator
ventilator.
.

3. Purposes
Purposes
:
:
• To maintain Gas exchange & improve
To maintain Gas exchange & improve
tissue oxygenation.
tissue oxygenation.
• To decrease the work of breathing &
To decrease the work of breathing &
improve patient
improve patient’
’s comfort.
s comfort.

4. Indications
Indications
:
:
1-
1- Acute respiratory failure due to:
Acute respiratory failure due to:
• Mechanical failure
Mechanical failure, includes neuromuscular
, includes neuromuscular
diseases as Myasthenia Gravis, Guillain-Barré
diseases as Myasthenia Gravis, Guillain-Barré
Syndrome, and Poliomyelitis (failure of the
Syndrome, and Poliomyelitis (failure of the
normal respiratory neuromuscular system)
normal respiratory neuromuscular system)
• Musculoskeletal abnormalities
Musculoskeletal abnormalities, such as chest wall
, such as chest wall
trauma (flail chest)
trauma (flail chest)
• Infectious diseases
Infectious diseases of the lung such as pneumonia,
of the lung such as pneumonia,
tuberculosis.
tuberculosis.

5. 2-
2- Abnormalities of pulmonary gas exchange
Abnormalities of pulmonary gas exchange
as in:
as in:
• Obstructive lung disease
Obstructive lung disease in the form of
in the form of
asthma, chronic bronchitis or emphysema.
asthma, chronic bronchitis or emphysema.
• Conditions such as pulmonary edema,
Conditions such as pulmonary edema,
atelectasis, pulmonary fibrosis.
atelectasis, pulmonary fibrosis.
• Patients who has received
Patients who has received general anesthesia
general anesthesia
as well as
as well as post cardiac arrest
post cardiac arrest patients often
patients often
require ventilatory support until they have
require ventilatory support until they have
recovered from the effects of the anesthesia
recovered from the effects of the anesthesia
or the insult of an arrest.
or the insult of an arrest.

6. Clinical Criteria for institution of
Clinical Criteria for institution of
ventilatory support
ventilatory support
:
:
Parameters
Parameters Ventilation
Ventilation
indicated
indicated
Normal
Normal
range
range
A- Pulmonary function
A- Pulmonary function
studies
studies
:
:
• Respiratory rate
Respiratory rate
(breaths/min).
(breaths/min).
• Tidal volume (ml/kg
Tidal volume (ml/kg
body wt)
body wt)
• Vital capacity (ml/kg
Vital capacity (ml/kg
body wt)
body wt)
• Maximum Inspiratory
Maximum Inspiratory
Force (cm HO
Force (cm HO2)
)
>
>
35
35
<
<
5
5
<
<
15
15
-<
-<
20
20
10-20
10-20
5-7
5-7
65-75
65-75
75-100
75-100

7. Criteria for institution of
Criteria for institution of
ventilatory support
ventilatory support
:
:
Parameters
Parameters Ventilation
Ventilation
indicated
indicated
Normal
Normal
range
range
B- Arterial blood
B- Arterial blood
Gases
Gases
• PH
PH
• PaO
PaO2 (mmHg)
(mmHg)
• PaCO
PaCO2 (mmHg)
(mmHg)
<
<
7.25
7.25
<
<
60
60
>
>
50
50
7.35-7.45
7.35-7.45
75-100
75-100
35-45
35-45

8. Types of Mechanical
Types of Mechanical
ventilators
ventilators
:
:
• Negative-pressure ventilators
Negative-pressure ventilators
• Positive-pressure ventilators.
Positive-pressure ventilators.

9. Negative-Pressure Ventilators
Negative-Pressure Ventilators
• Early negative-pressure ventilators
Early negative-pressure ventilators
were known as
were known as “
“iron lungs.
iron lungs.”
”
• The patient
The patient’
’s body was encased in an
s body was encased in an
iron cylinder and negative pressure
iron cylinder and negative pressure
was generated .
was generated .

11. Positive-pressure ventilators
Positive-pressure ventilators
• Positive-pressure ventilators deliver
Positive-pressure ventilators deliver
gas to the patient under positive-
gas to the patient under positive-
pressure, during the inspiratory
pressure, during the inspiratory
phase.
phase.

13. Types of Positive-Pressure
Types of Positive-Pressure
Ventilators
Ventilators
1-
1- Volume Ventilators.
Volume Ventilators.
2-
2- Pressure Ventilators
Pressure Ventilators

14. • The volume ventilator is
The volume ventilator is commonly used
commonly used in
in
emergency situations.
emergency situations.
• The basic principle of this ventilator is that
The basic principle of this ventilator is that
a designated volume of air is delivered
a designated volume of air is delivered
with each breath.
with each breath.
• With this mode of ventilation, a
With this mode of ventilation, a respiratory
respiratory
rate, inspiratory time, and tidal volume
rate, inspiratory time, and tidal volume are
are
selected for the mechanical breaths.
selected for the mechanical breaths.
1-
1- Volume Ventilators
Volume Ventilators

15. • The amount of
The amount of pressure
pressure required to deliver
required to deliver
the set volume
the set volume depends on :-
depends on :-
- Patient
- Patient’
’s lung compliance
s lung compliance
- Patient
- Patient–
–ventilator resistance factors.
ventilator resistance factors.
• Therefore,
Therefore, peak inspiratory pressure
peak inspiratory pressure (PIP )
(PIP )
must be monitored
must be monitored in volume modes
in volume modes
because it varies from breath to breath.
because it varies from breath to breath.

16. • The use of pressure ventilators
The use of pressure ventilators is increasing
is increasing
in critical care units.
in critical care units.
• A typical pressure mode
A typical pressure mode delivers a selected
delivers a selected
gas pressure to the patient early in
gas pressure to the patient early in
inspiration, and sustains the pressure
inspiration, and sustains the pressure
throughout the inspiratory phase.
throughout the inspiratory phase.
• By meeting the patient
By meeting the patient’
’s inspiratory flow
s inspiratory flow
demand throughout inspiration,
demand throughout inspiration, patient
patient
effort is reduced and comfort increased.
effort is reduced and comfort increased.
2-
2- Pressure Ventilators
Pressure Ventilators

17. • Although
Although pressure is consistent
pressure is consistent with these
with these
modes, volume is not.
modes, volume is not.
• Volume will change with changes in
Volume will change with changes in
resistance or compliance,
resistance or compliance,
• Therefore,
Therefore, exhaled tidal volume is the
exhaled tidal volume is the
variable to monitor closely.
variable to monitor closely.
• With pressure modes,
With pressure modes, the pressure level to
the pressure level to
be delivered is selected, and with some
be delivered is selected, and with some
mode options
mode options (i.e., pressure controlled [PC],
(i.e., pressure controlled [PC],
described later),
described later), rate and inspiratory time
rate and inspiratory time
are preset as well.
are preset as well.

18. Ventilator mode
Ventilator mode
• The way the machine ventilates the
The way the machine ventilates the
patient
patient
• How much the patient will participate
How much the patient will participate
in his own ventilatory pattern.
in his own ventilatory pattern.
• Each mode is different in determining
Each mode is different in determining
how much work of breathing the
how much work of breathing the
patient has to do.
patient has to do.

19. 1- Control Mode (CM)
1- Control Mode (CM)
Continuous Mandatory Ventilation
Continuous Mandatory Ventilation
( CMV)
( CMV)
• Ventilation is completely provided by the mechanical
Ventilation is completely provided by the mechanical
ventilator with
ventilator with a preset tidal volume, respiratory rate
a preset tidal volume, respiratory rate
and oxygen concentration
and oxygen concentration
• Ventilator
Ventilator totally controls the patient
totally controls the patient’
’s ventilation
s ventilation i.e.
i.e.
the ventilator initiates and controls both the volume
the ventilator initiates and controls both the volume
delivered and the frequency of breath.
delivered and the frequency of breath.
• Patient does not breathe spontaneously.
Patient does not breathe spontaneously.
• It can be both
It can be both volume controlled or pressure
volume controlled or pressure
controlled.
controlled.

20. Pressure-Controlled
Pressure-Controlled
Ventilation Mode ( PCV)
Ventilation Mode ( PCV)
• In pressure controlled ventilation the breathing gas
In pressure controlled ventilation the breathing gas
flows under constant pressure into the lungs during
flows under constant pressure into the lungs during
the selected inspiratory time.
the selected inspiratory time.
• The flow is highest at the beginning of inspiration( i.e
The flow is highest at the beginning of inspiration( i.e
when the volume is lowest in the lungs).
when the volume is lowest in the lungs).
• As the pressure is constant the flow is initially high
As the pressure is constant the flow is initially high
and then decreases with increasing filling of the
and then decreases with increasing filling of the
lungs.
lungs.

21. Assist Control Mode A/C
Assist Control Mode A/C
• The ventilator provides the patient with a
The ventilator provides the patient with a
pre-set tidal volume at a pre-set rate .
pre-set tidal volume at a pre-set rate .
• The patient may
The patient may initiate a breath on his
initiate a breath on his
own
own, but the
, but the ventilator assists by delivering
ventilator assists by delivering
a specified tidal volume to the patient.
a specified tidal volume to the patient.
Client can initiate breaths that are
Client can initiate breaths that are
delivered at the preset tidal volume.
delivered at the preset tidal volume.
• Client can breathe at a higher rate than the
Client can breathe at a higher rate than the
preset number of breaths/minute
preset number of breaths/minute

22. • Often used as initial mode of
Often used as initial mode of
ventilation
ventilation
Disadvantages:
Disadvantages:
• Hyperventilation,
Hyperventilation,

23. Synchronized Intermittent
Synchronized Intermittent
Mandatory Ventilation (SIMV)
Mandatory Ventilation (SIMV)
• The ventilator provides the patient with a pre-set
The ventilator provides the patient with a pre-set
number of breaths/minute at a specified tidal
number of breaths/minute at a specified tidal
volume and FiO
volume and FiO2.
.
• In between the ventilator-delivered breaths
In between the ventilator-delivered breaths, the
, the
patient is able to
patient is able to breathe spontaneously at his
breathe spontaneously at his
own tidal volume and rate
own tidal volume and rate with no assistance
with no assistance
from the ventilator.
from the ventilator.
• However, unlike the A/C mode,
However, unlike the A/C mode, any breaths taken
any breaths taken
above the set rate are spontaneous breaths taken
above the set rate are spontaneous breaths taken
through the ventilator circuit.
through the ventilator circuit.

24. • The tidal volume of these breaths can vary
The tidal volume of these breaths can vary
drastically from the tidal volume set on the
drastically from the tidal volume set on the
ventilator
ventilator, because the tidal volume is
, because the tidal volume is
determined by the
determined by the patient
patient’
’s spontaneous
s spontaneous
effort.
effort.
• Adding pressure support
Adding pressure support during
during
spontaneous breaths can
spontaneous breaths can minimize the risk
minimize the risk
of increased work of breathing.
of increased work of breathing.
• Ventilators breaths are
Ventilators breaths are synchronized
synchronized with
with
the patient spontaneous breathe.
the patient spontaneous breathe.
( no fighting)
( no fighting)

25. • Used to wean the patient from the
Used to wean the patient from the
mechanical ventilator.
mechanical ventilator.
• Weaning
Weaning is accomplished by
is accomplished by
gradually lowering the set rate and
gradually lowering the set rate and
allowing the patient to assume more
allowing the patient to assume more
work
work

26. 3
3
-
-
Pressure Support Ventilation
Pressure Support Ventilation
( PSV)
( PSV)
• Pressure support ventilation augments
Pressure support ventilation augments
patient
patient’
’s spontaneous breaths with
s spontaneous breaths with
positive pressure boost during inspiration
positive pressure boost during inspiration
i.e. assisting each spontaneous inspiration.
i.e. assisting each spontaneous inspiration.
• Helps to overcome airway resistance and
Helps to overcome airway resistance and
reducing the work of breathing
reducing the work of breathing.
.
• It is a mode
It is a mode used primarily for weaning from
used primarily for weaning from
mechanical ventilation.
mechanical ventilation.

27. • Constant positive airway pressure
Constant positive airway pressure during spontaneous
during spontaneous
breathing
breathing
• CPAP allows the nurse to observe the ability of the patient
CPAP allows the nurse to observe the ability of the patient
to breathe spontaneously while still on the ventilator.
to breathe spontaneously while still on the ventilator.
• CPAP can be used
CPAP can be used for intubated and nonintubated patients.
for intubated and nonintubated patients.
• It may be used as
It may be used as a weaning mode
a weaning mode and for
and for nocturnal
nocturnal
ventilation
ventilation (nasal or mask CPAP)
(nasal or mask CPAP)
4
4
-
-
Continuous Positive Airway
Continuous Positive Airway
Pressure (CPAP)
Pressure (CPAP)

28. 5
5
-
-
Positive end expiratory
Positive end expiratory
pressure (PEEP)
pressure (PEEP)
• Positive pressure applied at the end
Positive pressure applied at the end
of expiration during mandatory
of expiration during mandatory
ventilator breath
ventilator breath
• positive end-expiratory pressure with
positive end-expiratory pressure with
positive-pressure (machine) breaths.
positive-pressure (machine) breaths.

29. Uses of CPAP & PEEP
Uses of CPAP & PEEP
• Prevent atelactasis or collapse of alveoli
Prevent atelactasis or collapse of alveoli
• Treat atelactasis or collapse of alveoli
Treat atelactasis or collapse of alveoli
• Improve gas exchange & oxygenation
Improve gas exchange & oxygenation
• Treat hypoxemia refractory to oxygen
Treat hypoxemia refractory to oxygen
therapy.(prevent oxygen toxicity
therapy.(prevent oxygen toxicity
• Treat pulmonary edema ( pressure help
Treat pulmonary edema ( pressure help
expulsion of fluids from alveoli
expulsion of fluids from alveoli

30. 6
6
-
-
Noninvasive Bilateral Positive
Noninvasive Bilateral Positive
Airway Pressure Ventilation (BiPAP)
Airway Pressure Ventilation (BiPAP)
• BiPAP is a noninvasive form of mechanical
BiPAP is a noninvasive form of mechanical
ventilation
ventilation provided by means of a nasal mask
provided by means of a nasal mask
or nasal prongs, or a full-face mask.
or nasal prongs, or a full-face mask.
• The system allows the clinician to select
The system allows the clinician to select two
two
levels of positive-pressure support
levels of positive-pressure support:
:
• An inspiratory pressure support level (referred
An inspiratory pressure support level (referred
to as IPAP)
to as IPAP)
• An expiratory pressure called EPAP (PEEP/CPAP
An expiratory pressure called EPAP (PEEP/CPAP
level).
level).

31. Common Ventilator Settings
Common Ventilator Settings
parameters/ controls
parameters/ controls
• Fraction of inspired oxygen (FIO
Fraction of inspired oxygen (FIO2)
)
• Tidal Volume (VT)
Tidal Volume (VT)
• Peak Flow/ Flow Rate
Peak Flow/ Flow Rate
• Respiratory Rate/ Breath Rate /
Respiratory Rate/ Breath Rate /
Frequency ( F)
Frequency ( F)
• Minute Volume (VE)
Minute Volume (VE)
• I:E Ratio (Inspiration to Expiration
I:E Ratio (Inspiration to Expiration
Ratio)
Ratio)
• Sigh
Sigh

32. ●
●
Fraction of inspired oxygen
Fraction of inspired oxygen
(FIO
(FIO2)
)
• The percent of oxygen concentration that
the patient is receiving from the
ventilator. (Between 21% & 100%)
(room air has 21% oxygen content).
• Initially a patient is placed on a high level
of FIO2 (60% or higher).
• Subsequent changes in FIO2 are based on
ABGs and the SaO2.

33. ●
●
Tidal Volume (VT)
Tidal Volume (VT)
• The volume of air delivered to a patient
The volume of air delivered to a patient
during a ventilator breath.
during a ventilator breath.
• The amount of air inspired and expired
The amount of air inspired and expired
with each breath.
with each breath.
• Usual volume selected is between
Usual volume selected is between 5 to 15
5 to 15
ml/ kg body weight)
ml/ kg body weight)

34. • In the volume ventilator, Tidal volumes of
In the volume ventilator, Tidal volumes of
10 to 15 mL/kg of body weight were
10 to 15 mL/kg of body weight were
traditionally used.
traditionally used.
• the large tidal volumes may lead to
the large tidal volumes may lead to
(volutrauma)
(volutrauma) aggravate the damage
aggravate the damage
inflicted on the lungs
inflicted on the lungs
• For this reason, lower tidal volume targets
For this reason, lower tidal volume targets
(6 to 8 mL/kg) are now recommended.
(6 to 8 mL/kg) are now recommended.

35. ●
●
Peak Flow/ Flow Rate
Peak Flow/ Flow Rate
• The speed of delivering air per unit of
The speed of delivering air per unit of
time, and is expressed in liters per
time, and is expressed in liters per
minute.
minute.
• The higher the flow rate, the faster
The higher the flow rate, the faster
peak airway pressure is reached and
peak airway pressure is reached and
the shorter the inspiration;
the shorter the inspiration;
• The lower the flow rate, the longer the
The lower the flow rate, the longer the
inspiration.
inspiration.

36. ●
●
Respiratory Rate/ Breath
Respiratory Rate/ Breath
Rate / Frequency ( F)
Rate / Frequency ( F)
• The number of breaths the ventilator will
The number of breaths the ventilator will
deliver/minute
deliver/minute (10-16 b/m).
(10-16 b/m).
• Total respiratory rate equals
Total respiratory rate equals patient rate
patient rate
plus ventilator rate.
plus ventilator rate.
• The nurse double-checks the functioning of
The nurse double-checks the functioning of
the ventilator by observing the patient
the ventilator by observing the patient’
’s
s
respiratory rate.
respiratory rate.

37. ●
●
Minute Volume (VE)
Minute Volume (VE)
• The volume of expired air in one
The volume of expired air in one
minute .
minute .
• Respiratory rate times tidal volume
Respiratory rate times tidal volume
equals minute ventilation
equals minute ventilation
VE = (VT x F)
VE = (VT x F)
• In special cases, hypoventilation or
In special cases, hypoventilation or
hyperventilation is desired
hyperventilation is desired

38. ●
●
I:E Ratio (Inspiration to
I:E Ratio (Inspiration to
Expiration Ratio)
Expiration Ratio)
-:
-:
• The ratio of inspiratory time to
The ratio of inspiratory time to
expiratory time during a breath
expiratory time during a breath
(Usually = 1:2)
(Usually = 1:2)

39. ●
●
Peak Airway Pressure
Peak Airway Pressure
-:
-:
• In adults
In adults if the peak airway pressure
if the peak airway pressure
is persistently
is persistently above 45 cmH
above 45 cmH2O, the
O, the
risk of barotrauma is increased
risk of barotrauma is increased and
and
efforts should be made to try to
efforts should be made to try to
reduce the peak airway pressure.
reduce the peak airway pressure.
• In infants and children
In infants and children it is unclear
it is unclear
what level of peak pressure may
what level of peak pressure may
cause damage.
cause damage. In general, keeping
In general, keeping
peak pressures below 30 is desirable
peak pressures below 30 is desirable.
.

40. ●
●
Pressure Limit
Pressure Limit
• On volume-cycled ventilators, the pressure
On volume-cycled ventilators, the pressure
limit dial
limit dial limits the highest pressure
limits the highest pressure
allowed in the ventilator circuit.
allowed in the ventilator circuit.
• Once the high pressure limit is reached,
Once the high pressure limit is reached,
inspiration is terminated.
inspiration is terminated.
• Therefore, if the pressure limit is being
Therefore, if the pressure limit is being
constantly reached,
constantly reached, the designated tidal
the designated tidal
volume is not being delivered to the
volume is not being delivered to the
patient.
patient.

41. SCENARIO-1
SCENARIO-1
In a patient with head injury
In a patient with head injury,
,
• Respiratory alkalosis may be required to
Respiratory alkalosis may be required to
promote cerebral vasoconstriction, with a
promote cerebral vasoconstriction, with a
resultant decrease in ICP.
resultant decrease in ICP.
• In this case, the tidal volume and
In this case, the tidal volume and
respiratory rate are increased
respiratory rate are increased
( hyperventilation) to achieve the desired
( hyperventilation) to achieve the desired
alkalotic pH by manipulating the PaCO
alkalotic pH by manipulating the PaCO2.
.

42. SCENARIO-2
SCENARIO-2
In a patient with COPD
In a patient with COPD
• Baseline ABGs reflect an elevated PaCO
Baseline ABGs reflect an elevated PaCO2
should not hyperventilated. Instead, the
should not hyperventilated. Instead, the
goal should be restoration of the baseline
goal should be restoration of the baseline
PaCO
PaCO2.
.
• These patients usually have a large
These patients usually have a large
carbonic acid load, and lowering their
carbonic acid load, and lowering their
carbon dioxide levels rapidly may result in
carbon dioxide levels rapidly may result in
seizures.
seizures.

43. SCENARIO-3
SCENARIO-3
In a patient in SHOCK
In a patient in SHOCK
• Low PEEP.
Low PEEP.
• Higher FiO2.
Higher FiO2.
• Peak pressure to be limited.
Peak pressure to be limited.

44. SCENARIO-4
SCENARIO-4
In a patient in ARDS:
In a patient in ARDS:
• LUNG PROTECTIVE VENTILATION.
LUNG PROTECTIVE VENTILATION.
• Low Tidal volume.
Low Tidal volume.
• High respiratory rate.
High respiratory rate.
• High PEEP.
High PEEP.
• Inverse ratio ventilation.
Inverse ratio ventilation.

45. Complications
Complications
of Mechanical Ventilation:-
of Mechanical Ventilation:-
I-
I- Airway Complications,
Airway Complications,
II-
II- Mechanical complications,
Mechanical complications,
III-
III- Physiological Complications,
Physiological Complications,
IV-
IV- Artificial Airway Complications.
Artificial Airway Complications.

46. I- Airway Complications
I- Airway Complications
1-
1- Aspiration
Aspiration
2-
2- Decreased clearance of secretions
Decreased clearance of secretions
3-
3- Nosocomial or ventilator-acquired
Nosocomial or ventilator-acquired
pneumonia
pneumonia

47. II- Mechanical complications
II- Mechanical complications
1-
1- Hypoventilation with atelectasis with respiratory
Hypoventilation with atelectasis with respiratory
acidosis or hypoxemia.
acidosis or hypoxemia.
2-
2- Hyperventilation with hypocapnia and respiratory
Hyperventilation with hypocapnia and respiratory
alkalosis
alkalosis
3-
3- Barotrauma
Barotrauma
a- Closed pneumothorax,
a- Closed pneumothorax,
b- Tension pneumothorax,
b- Tension pneumothorax,
c- Pneumomediastinum,
c- Pneumomediastinum,
d- Subcutaneous emphysema.
d- Subcutaneous emphysema.
4-
4- Alarm
Alarm “
“turned off
turned off”
”
5-
5- Failure of alarms or ventilator
Failure of alarms or ventilator
6-
6- Inadequate nebulization or humidification
Inadequate nebulization or humidification
7-
7- Overheated inspired air, resulting in hyperthermia
Overheated inspired air, resulting in hyperthermia

48. III- Physiological Complications
III- Physiological Complications
1-
1- Fluid overload with humidified air and
Fluid overload with humidified air and
sodium chloride (NaCl) retention
sodium chloride (NaCl) retention
2-
2- Depressed cardiac function and
Depressed cardiac function and
hypotension
hypotension
3-
3- Stress ulcers
Stress ulcers
4-
4- Paralytic ileus
Paralytic ileus
5-
5- Gastric distension
Gastric distension
6-
6- Starvation
Starvation
7-
7- Dyssynchronous breathing pattern
Dyssynchronous breathing pattern

49. Thank you
Thank you