This ppt comprise of introduction to mechanical ventilation,modes of ventilation, weaning criteria and weaning process.

1. Modes Of Ventilation And
Weaning BY : Dr Bhanupriya P.V.V

2. Topics covered…
Introduction
Modes of ventilation
Weaning

3. Introduction
Mechanical Ventilation is ventilation of the lungs
by artificial means usually by a ventilator.
A ventilator delivers gas to the lungs with either
negative or positive pressure.

4. purpose
To maintain or improve ventilation, & tissue
oxygenation.
To decrease the work of breathing & improve
patient’s comfort

5. TYPES OF VENTILATION
Negative pressure ventilation
Positive pressure ventilation

6. Negative ventilation
Principle – creates a negative pressure on the chest wall
The pressure in the airways, alveoli, and pleura are decreased
during inspiration
Creates a transairway pressure gradient by decreasing the
alveolar pressures to a level below the airway opening
pressure
Two classic devices “IRON LUNG” & “CHEST CUIRASS”

7. Iron lung

8. • Negative-pressure
ventilators (“iron lungs”)
• first used in Boston
Children’s Hospital in
1928(drinker ventilator)
• Used extensively during
polio outbreaks in 1940s
– 1950s

9. The patient’s body is encased in an iron cylinder and
negative pressure was generated
Intermittent short-term negative-pressure ventilation is
sometimes used in patients with chronic diseases
The use of negative-pressure ventilators is restricted in
clinical practice, because they limit patient access,
positioning and movement and they lack adaptability to
large or small body torsos (chests)

10. Positive pressure ventilation
Concepts that the military developed during world war II
to deliver oxygen and gas volume to fighter pilots
operating at high altitude were incorporated into the
design of the modern positive-pressure ventilator
Intensive use of positive-pressure ventilation gained
momentum during the polio epidemic in Scandinavia in
1950’s

11. Positive pressure ventilation is achieved by applying
positive pressure at the airway opening
Increasing the pressure at airway opening produces a
transairway pressure gradient that generates an
inspiratory flow
This flow results in the delivery of a tidal volume

12. Ventilator mode
A ventilator mode can be defined as a set of operating
characteristics that control how the ventilator functions
Each mode is different in determining how much work of
breathing the patient has to do
An operating mode can be described by the way a
ventilator is triggered into inspiration and cycled into
exhalation, what variables are limited during insp, and
whether or not the mode allows only mandatory breaths,
spont breaths, or both

13. Modes of ventilation

14. Spontaneous Modes
Positive End Expiratory Pressure (PEEP)
CPAP
PSV
BiPAP

15. Positive end expiratory
pressure (PEEP)
Positive pressure applied at the end of expiration during mandatory
ventilator breath
positive end-expiratory pressure increase the end expiratory or
baseline airway pressure to a value greater than atm pr
It is applied in conjuction with other ventilator modes
Indications
1. intrapulmonary shunting and refractory hypoxemia
2. decreased FRC and lung compliance

16. Physiology
PEEP
increases alveolar distending pressure
increases FRC by alveolar recruitment
improves ventilation
-improves oxygenation
- decreases work of breathing

17. PEEP prevents complete collapse of the alveoli
and keep them partially inflated and thus
provide protection against the development of
shear forces during mechanical inflation
BENEFITS
1. Restore FRC/ Alveolar
recruitment
2. ↓ shunt fraction
3. ↓WOB
4. ↑PaO2 with low FiO2
DETRIMENTAL EFFECTS
1. Barotrauma
2. ↓ VR/ CO
3. ↑ MAP
4. ↓ Renal / portal bld flow

18. AUTO PEEP/ INTRINSIC PEEP
-Airflow limitation because of dynamic collapse
-No time to expire all the lung volume (high RR or Vt)
-Lesions that increase expiratory resistance

19. Disadv
1. Barotrauma / volutrauma
2. ↑WOB a) lung overstretching
↓contractility of diaphragm
3. ↑ MAP – CVS side effects
4. May ↑ PVR
Minimising Auto PEEP
1. ↓airflow res – secretion
management,
bronchodilation, large ETT
2. ↓Insp time ( ↑insp flow, sq
flow waveform, low TV)
3. ↑ exp time (low resp rate )
4. Apply PEEP to balance
AutoPEEP

20. Continuous Positive Airway
Pressure (CPAP)
Constant positive airway pressure is PEEP applied to the airway
of a patient who is breathing spontaneously
Same indications as PEEP
Pt must have adequate lung function that can sustain Eucapnic
ventilation
CPAP can be used for intubated and nonintubated patients.
In non invasive ventilation- CPAP is given via a tight fitting
nasal mask or face mask

22. Bilateral Positive Airway Pressure Ventilation (BiPAP)
BiPAP is a noninvasive form of mechanical ventilation
provided by means of a nasal mask or nasal prongs, or a
full-face mask.
The system allows the clinician to apply independent
positive airway pressures to both inspiration and
expiration
An inspiratory pressure support level referred to as IPAP
An expiratory pressure called EPAP.

23. IPAP- improves hypoxemia and hypercapnia
EPAP- improves oxygenation by increasing FRC and
enhancing alveolar recruitment
Indications
- BiPAP appears to be of value in preventing intubation of
the end-stage COPD patient
- in supporting patients with chronic ventilator failure
-restrictive chest wall diseases
-neuromuscular diseases
- Nocturnal hypoventilation

24. In a spont breathing patient the IPAP and EPAP may set at
8cm H2O and 4cm H2O respectively
In spont/timed mode- BPM is set 2-5 breaths below the pt’s
spont rate
In timed mode- BPM is set slightly higher than the pt’s spont
rate
A BIPAP device can be used as a CPAP device by setting IPAP
and EPAP at the same level
IPAP may be increased in increments of 2cm H2O to
enhance the pressure boost to improve alveolar vent,
normalize PaCO2, and reduce the work of breathing
EPAP may be increased in increments of 2cm H2O to
increase FRC and oxygenation in pts with intrapul shunting

25. Pressure support ventilation
(psv)
The patient breathes spontaneously while the ventilator applies
a pre-determined amount of positive pressure to the airways
upon inspiration
Helps to overcome airway resistance, reduces the work of
breathing and augments the tidal volume
Pressure supported breaths
- pt triggered, pressure limited, flow cycled
- tidal vol varies with the pt’s insp flow demand
- insp lasts only for long as the pt actively inspires
- insp is terminated when the the pts insp flow demand
decreases to a preset minimal value
• Breath – SPONTANEOUS
• Trigger – PATIENT
• Limit - PRESSURE
• Cycle – FLOW
( 5-25% OF
PIFR)

27. Indications
A. - is commonly applied along with SIMV mode when
the pt takes spont breaths
1. to increase tidal volume
2. to decrease resp rate
3. to decrease work of breathing
B- To facilitate weaning
The level of pressure support is titrated until
1. Tidal volume = 10 to 15ml/kg or
2. Spont resp rate < 25/min

28. VOLUME MODES
Controlled Mandatory Ventilation (CMV)
Assist Control (AC)
Intermittent Mandatory Ventilation (IMV)
Synchronized Intermittent Mandatory Ventilation (SIMV)
Mandatory Minute Ventilation (MMV)

29. Controlled mandatory ventilation(cmv)
The ventilator delivers the preset tidal volume
Every breath is time triggered
Inspiration is terminated by the delivery of a preset tidal
volume (volume cycled)
Patient cannot change the ventilator respiratory rate or
breath spontaneously
It is used only when the patient is properly medicated
with a combination of sedatives, neuromuscular blockers
• Breath - MANDATORY
• Trigger – TIME
• Limit - VOLUME
• Cycle – VOL / TIME

32. Indications
1. “fighting” or “bucking”
2. Tetanus or any other seizure activities that interrupt the
delivery of mechanical ventilation.
3. Complete rest
4. Pt with chest injury in which spontaneous inspiratory
efforts produce paradoxical chest movement.

33. Disadvantages
1. Apnoea & hypoxia- in case of accidental disconnection or
the ventilator should fail to operate.
2. If not paralysed completely- Any spont resp effort would
be like attempting to inspire through a completely
obstructed airway
3. Psychologically devastating- for the pt to realize that he or
she has no control over his or her breathing.

34. Assist control (ac)
In this mode patient can increase the ventilator resp rate
in addition to the preset mechanical resp rate.
Each control breath provides a preset, ventilator
delivered tidal volume
Each assist breath also results in a preset, ventilator
delivered tidal volume
This mode does not allow the patient to take spont resp
• Breath – MANDATORY
ASSISTED
• Trigger – PATIENT
TIME
• Limit - VOLUME
• Cycle – VOLUME / TIME

36. Control breath- time triggered
Assist breath- patient triggered
Inspiration is terminated by the delivery of a preset tidal
volume (volume cycled)
Indications
- pt who have stable resp drive with spont
inspiratory efforts of atleast 10-12/ min

37. Advantages
1. work of breathing – very small
2. This mode allows the patient to control the resp rate and
therefore the minute volume required to normalize the
patient’s PaCO2
Complications
1. Alveolar hyperventilation- resp centre damage-high drive
2. Hypocapnia
3. Resp alkalosis

38. Intermittent mandatory ventilation (imv)
IMV is a mode in which the ventilator delivers mandatory
breaths and allows the patient to breath spontaneously at any
tidal volume the patient is capable of in between the
mandatory breaths
Partial ventilator support
Complication- breath stacking if spont breath and mandatory
breath delivered at same time barotrauma
Barotrauma can be minimized by setting appropriate high
pressure limits
Replaced by SIMV mode
• Breath – MANDATORY
SPONTANEOUS
• Trigger – PATIENT
time
• Limit - VOLUME
• Cycle - VOLUME

40. Synchronized Intermittent mandatory ventilation (simv)
This mode also allows the patient to breath spontaneously at
any tidal volume the patient is capable of in between the
mandatory breaths
The mandatory breaths are synchronized with the patient’s
spontaneous breathing efforts so as to avoid breath stacking
Mandatory breath- time triggered or patient triggered
Spontaneous breaths- resp rate and tidal vol are totally
dependent on the pt’s breathing effort
Synchronization window- 0.5 sec
• Breath – SPONTANEOUS
ASSISTED
MANDATORY
• Trigger – PATIENT
TIME
• Limit - VOLUME
• Cycle – VOLUME/ TIME

42. Indications
- to provide partial ventilator support.. ie., a desire to have
the patient actively involved in providing part of the minute
ventilation
- weaning
Advantages
1. maintains resp ms strength/ avoids ms atrophy
2. Reduces ventilation- perfusion mismatch
3. Decreases mean airway pressure
4. Facilitates weaning
Complications- ms fatigue if the patient is weaned too
rapidly

43. MANDATORY minute ventilation
(mmv)
Also called minimun minute ventilation
This mode provides a predetermined minute ventilation
when the pt’s spontaneous breathing efforts become
inadequate
It is an additional function of the SIMV mode
It is intended to prevent hypercapnia by automatically
insuring that the pt receives a minimum preset minute
ventilation

44. Esp useful in the final stages of weaning with SIMV
During weaning, if the pt becomes apneic, then without
MMV the reduced minute ventilation would cause
hypercania and and resp acidosis
However, om MMV-equipped ventilators , a decrease in the
pt’s spont minute volume would trigger an automatic
increase in the ventilators mandatory resp rate
Important to monitor alveolar minute vol in distressed pt..
Increased resp rate.. Minute vol will be normal but high rate
low tidal vol increases dead space… so decreased alveolar
minute volume .. So high resp rate alarm should be set at
approximately 10/min greater than the patient’s baseline
spont resp rate
Exception: Hamilton Veolar ventilator: every breath is
pressure supported.. No mandatory breaths

45. PRESSURE MODES
Pressure control ventilation (PCV)
Pressure support ventilation (PSV)
Continuous Positive Airway Pressure (CPAP)
Bilateral Positive Airway Pressure Ventilation (BiPAP)

46. Pressure control ventilation
(PCV)
Invasive ventilation
Full ventilator support… gives only mandatory breaths
Pt should be properly medicated with a combination of
sedatives, neuromuscular blockers
Time triggered, pressure limited, time cycled
Pressure controlled breaths.. Once inspiration begins, a
pressure plateau is created and maintained for a preset
inspiratory time
• Breath – MANDATORY
• Trigger – TIME
• Limit - PRESSURE
• Cycle – TIME/ FLOW

48. It is usually indicated for pts with severe ARDS who
require high peak inspiratory pressures in volume mode
 in this mode the peak inspiratory pressures can be
reduced while still maintaining adequate oxygenation
and ventilation
Reduces risk of barotrauma

49. OTHER newer modes
Inverse Ratio Ventilation (IRV)
Airway Pressure Release Ventilation (APRV)
Proportional Assist Ventilation (PAV)
Neurally Adjusted Ventillatory Assist (NAVA)
 Dual modes-
1. Volume assured pressure support (VAPS)
2. Volume support (VS)
3. Pressure regulated volume controlled (PRVC)

50. Proportional assist ventilation
(pav)
 it is a mode of assisted ventilation where pressure is applied by the
ventilator in proportion to the patient generated flow and volume
Flow assist or Volume assist
Occurs during assisted breaths only
The adv of PAV is its ability to track changes of ventilator effort and
promotes pt- ventilator synchrony
Improves ventilation and decreased work of breathing
PAV with CPAP – reduction of inspiratory muscle work- improves
exercise tolerance

51. Airway Pressure Release Ventilation (APRV)
APRV is similar to CPAP in that the patient is allowed to
breathe spontaneously without restriction
During spont exhalation, the PEEP is dropped to a lower
level and this action simulates an effective exhalation
maneuver
Pressure release time- 1-2sec

52. The ventilator must have a high flow CPAP circuit that has
been modified with the addition of a release valve
The airway pressure increases during insp to CPAP pressure
and is maintained for the duration of insp
APRV breaths are pressure lmited
With APRV, pt’s tidal volume will vary directly with changes in
lung compliance and inversely with airway resistance
Provides effective partial vent support with lower peak airway
pressure than the PSV and SIMV modes in ARDS pts

53. Inverse ratio ventilation
(irv)
I:E ratio – the ratio of inspiration time to expiration time
In conventional mech ventilation- I:E ratio ranges from
about 1:1.5 to 1:3
This resembles normal I:E ratio during spont breathing,
and it is considered physiologically beneficial to normal
cardiopulmonary function
Increasing inspiratory time promotes oxygenation
The inverse ratio in use is between 2:1 to 4:1 and often it
is used in conjunction with pressure control ventilation

54. The increase in mean airway pressure and presence
of auto-PEEP during IRV helps to reduce shunting
and improves oxygenation in ARDS pts
 USES:
1. Reduction of intrapulmonary shunting
2. Improvement of V/Q matching
3. Decrease of dead space ventilation
Adverse effects
- barotrauma
- pulmonary edema –because of transvascular fluid
flow induced by increase alveolar pressure

55. weaning
Weaning is the gradual reduction in the level of ventilatory
support. A systemic approach to wean a patient off
mechanical ventilation by using a set of clinical
measurements as a guide
Weaning success: effective spontaneous breathing without
any mechanical assisstance for 24 hrs or more.
Weaning failure: when pt is returned to mechanical
ventilation after any length of weaning trial.
Signs of weaning failure: abnormal blood gases, diaphoresis,
tachycardia, tachypnea, arrhythmias, hypotension.

56. WEANING CRITERIA
Used to evaluate the readiness of a patient for weaning
trial.
Common weaning criteria:
Ventilatory criteria
Oxygenation criteria
Pulmonary reserve
Pulmonary measurements
Other factors

57. VENTILATORY CRITERIA
PaCO2: < 50 mmhg with pH >/= 7.35
VC: > 10 to 15 ml/kg
Spontaneous VT: > 5 to 8 ml/kg
Spontaneous RR: < 30/min
Minute ventilation: < 10 lts

58. OXYGENATION CRITERIA
PaO2 without PEEP > 60 mmhg @FiO2 upto 0.4
PaO2 with PEEP > 100 mmhg @ FiO2 upto 0.4
SaO2 > 90% @ FiO2 upto 0.4
Qs/Qt < 20%
P(A-a)O2 < 350 mmhg
PaO2/FiO2 > 200 mmhg

59. PULMONARY RESERVE AND MEASUREMENTS
Pulmonary reserve:
Max. voluntary ventilation – 2×min. vent@FiO2 upto
0.4
Max. Insp. Pressure < -20 to -30 cmH2O in 20
sec.
Pulmonary measurements:
Static compliance > 30 ml/cm H2O
Vd/Vt < 60%

60. COMBINED WEANING INDICES
Simplified weaning index: evaluates efficiency of gas
exchange.= ( f * (PIP – PEEP)/MIP) × PaCO2/40
should be < 9/min 93% success
CROP index: evaluates pulmonary gas exchange and
balance b/w respiratory demands and respiratory
neuromuscular reserve. = ( Cd × MIP × PaO2/PAO2)/f.
Should be > 13 ml/breath/min.
RSBI: should be < 100 cycles/min/lt = f/Vt.
Most accurate test to predict weaning success.

61. others
 Metabolic factors
• Inadequate nutrition – protein catabolism
• Overfeeding - ↑ CO2 production
• Phosphate, ? Magnesium deficiency - ↓respi pump functn
• Impaired O2 delivery - ↓respi pump functn.
 Renal function:
• Patient should have adeq renal output (> 1000 ml/day)
• Monitor electolytes to ensure adequate respi msl functn
 Cardiovascular function
• Ensures sufficient O2 delivery to tissues
• Cardiac rate, rhythm, BP, CO should be optimal with minimal pressure support
 CNS assessment
• Assess for LOC, anxiety, dyspnea, motivation
• CNS should be intact for protection of airway.

62. Weaning methods
Spontaneous breathing trial
SIMV with pressure support.
PSV
Rapid ventilator discontinuation (off the ventilator)

63. Rapid ventilator discontinuation
 pt.on vent for < 72 hrs., has good spont RR, MV, MIP,
f/Vt
EXTUBATE if no other limiting factor

64.  T-Tube trial: allows spont. breathing several times per day interspersed
with periods of ventilatory support.
 Initial SBT’s may last only 5 to 30 min.
 Resume mechanical ventilation at night or if distress occurs.
 ADVANTAGES
-Tests pt’s spon breathing ability
-Allows periods of work and rest
-Weans faster than SIMV
 DISADVANTAGES
-Abrupt transition difficult for some pts
-No alarms, unless attached to vent so requires careful observation
Spontaneous Breathing Trial

65. Weaning protocol for a SBT with a T-Tube
Pt is put on T-piece for 5min every 30- 180 min
Return pt to mechanical ventilation
The duration of T-tube is gradually increased as tolerated
by the patient for upto 2hrs
If pt tolerates – he can be extubated if ABG, vital signs are
normal

66. Signs of intolerance of SBT
Agitation, anxiety, diaphoresis or change in mental status
RR > 30 to 35/min
SpO2 < 90%
> 20% ↑ or ↓ in HR or HR > 120 to 140/min
SBP > 180 or < 90 mmhg.
Such pts are returned to full ventilatory support for 24
hrs. to allow the ventilatory msls. to recover.

67. Weaning with SIMV
Involves gradual reduction in machine rate based on ABG and
clinical assessment.
Rate is decrease by 2 breaths/min…followed by pt assessment and
ABG after 30min
Rate decreased upto 0… if pt tolerates.. extubate
 ADVANTAGES
-Gradual transition
-Easy to use
-Minimum MV guaranteed
-Alarm system may be used
-Should be used in comb. with
PSV/CPAP
 DISADVANTAGES
- Pt. – ventilator asynchrony
- Prolonges weaning and may
worsen fatigue

68. Pressure Support
Ventilation (PSV)
 Patient determines RR, VE, inspiratory time – a purely spontaneous mode
• Parameters
• Triggered by pt’s own breath
• Limited by pressure
• Affects inspiration only
• Uses
• used along with SIMV mode
• Does not augment TV but overcomes resistance created by ventilator tubing
• Helps reduce the airway resistance imposed on the pt by the ET tube and
ventilator circuit
• Augments inflation volumes.

69. Begin with PSV(5 – 15cm H2O)
Adjust pressure(upto 40cmH2O) to achieve a TV of 8 to
10 ml/kg or spont rate of <25BPM
Reduce PSV 3 to 6 cm H2O intervals until a level of close
to 0 is achieved
Consider extubation when pt. tolerates weaning with no
apparent distress and with normal ABG and vital signs

70. ADVANTAGES
 Gradual transition
 Prevents fatigue
 Increased pt comfort
 Weans faster than SIMV alone
 Every breath is supported
 Pt can control cycle length,
rate
 and inspiratory flow.
 Overcomes resistive WOB due
to ET tube and circuit
DISADVANTAGES
DISADVANTAGES
DISADVANTAGES
 Large changes in MV can
occur
 ↑ed MAP versus T-Tube
 TV not guaranteed

71. CPAP
ventilation without artificial airway : -Nasal , face mask
 Advantages
 Avoid intubation / c/c
 Preserve natural airway
defences
 Comfort
 Speech/ swallowing +
 Less sedation needed
 Intermittent use
 Disadvantages
 Cooperation
 Mask discomfort
 Air leaks
 Facial ulcers, eye irritation,
dry nose
 Aerophagia
 Limited P support
 e.g. BiPAP, CPAP

72. Extubation failure
Defined as need for reinstitution of vent support
within 24 – 72 hrs of ETT removal.
Occurs in 2 – 25 % of pts.
Predisposing factors
- advanced age
-duration of mech. Vent.
- anemia
-use of cont. IV sedation
Find & manage the cause

73. Terminal weaning
Defined as withdrawal of mechanical ventilation that results
in death of the pt.
pt’s informed consent
TERMINAL WEANING is justified
-if medical interventions futile or hopeless
- to stop pain and suffering
Carries many ethical and legal implications.

74. Thank u

75. References
1. David W Chang, Clinical application of mechanical
ventilation 2nd ed.
2. Paul L Marino, The ICU Book, 3rd ed.
3. Susan P. Pilbeam, Mechanical ventilation, 4th ed.