A mechanical ventilator is a machine that helps a patient breathe (ventilate) when they are having surgery or cannot breathe on their own due to a critical illness. The patient is connected to the ventilator with a hollow tube (artificial airway) that goes in their mouth and down into their main airway or trachea

1. MECHANICAL VENTILATOR –
SETTINGS & MODES
DR.ASHUTOSH KUMAR SINGH

2. Introduction
A ventilator is a machine which is designed to mechanically move
breathable air into and out of the lungs, to provide the mechanism of
breathing for a patient who is physically not able to breathe sufficiently.

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5. Indication for ventilation
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1. Acute lung injury
2. Acute severe asthma, requiring intubation
3. Chronic Obstructive Pulmonary Disease.
4. Apnoea with respiratory arrest.
5. Hypoxemia.
6. Acute respiratory acidosis.
7. Respiratory distress addressing increased work of breathing.
8. Hypotension including sepsis, shock, CHF.
9. Neurological conditions such as Muscular Dystrophy, Amyotrophic Lateral
Sclerosis.

6. Application & duration of ventilation
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• It can be used as a short-term measure, for e.g., during an
operation,procedure.
• Long-term ventilatory assistance are required in chronic illness, and may
be used at home care.
• In positive pressure ventilator, The common employed method is
intubation which provides clear route for the air.
• Where as, In negative pressure or non-invasive ventilator, there is no
need to use any adjunct.

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Low flow nasal cannula

10. 10Criteria for ventilating a patient

11. Factors that should be observed in
case of ventilation
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• Vital Signs.
• Oxygen Saturation in the blood.
• Consciousness of the Patient.
• Checks alarm function of the ventilator.
• Secretions should be removed periodically.

12. Setting up a ventilator
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• Vital signs- Pulse, Blood Pressure, Respiratory Rate, Heart Rate.
• Ensure adequate sedations, opioids and muscle relaxants.
• Tidal volume- 6-8 ml/kg body weight.
• Fraction of inspired oxygen: Usually 100% oxygen to start there
decreases slow. Ensure the airway is secure.

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14. Phases of ventilation
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• Trigger phase
• Inspiratory phase.
• Cycling to inspiration phase
• Expiratory phase

15. Inspiration phase
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During the inspiratory phase positive pressure is
delivered to the lungs.
• The inspiratory phase lasts between .8 seconds to 2
seconds.
• The inspiratory phase can be adjusted depending
upon the clinical situation.

16. Cycling phase
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Volume cycled (or limited) will end the
inspiratory phase at a set volume (i.e.
500cc).
• Pressure cycled (or limited) will end the
inspiratory phase at a set pressure (i.e. 30
cmH20).

17. Expiratory phase
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The expiratory phase begins when the
inspiratory phase ends.
The person can manipulate various setting
to increase or decrease the expiratory
phase.

18. Respiration cycle
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Let us review:
 The trigger marks the start of the inspiratory phase.
 Positive pressure is applied to the lungs during the inspiratory phase.
 The inspiratory phase lasts between 0.8 and 2 seconds.
 The inspiratory phase ends (or cycled) at a preset volume (vT), pressure
(cmH2O) or flow (l/pm).
 At the end of the expiratory phase the ventilator is ready to start another
respiratory cycle.
Trigger
Inspiratory
phase
Cycling
Expiratory
phase

19. MODES OF MECHANICAL
VENTILATOR
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20. Introduction
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Ventilator mode is a set of operating characteristics that controls how the
ventilator functions.
An operating mode describes the way a ventilator is-
• triggered into inspiration
• cycled into exhalation
• what variables are limited during inspiration
• allowing mandatory or spontaneous breaths or both

21. Controlled mode ventilation
volume control
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• The ventilator delivers a preset TV at a specific R/R and inspiratory flow rate.
• It is irrespective of patients’ respiratory efforts.
• In between the ventilator delivered breaths the inspiratory valve is closed so
patient doesn’t take additional breaths.
• PIP developed depends on lung compliance and
respiratory passage resistance.

22. Controlled mode ventilation
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23. Volume controlled CMV
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Indications-
• In initial stage when patients “fighting” or “bucking” with the ventilator
• Tetanus or other seizure activity
• Crushed chest injury
Disadvantages-
• Asynchrony
• Barotrauma d/t high PAW & dec. lung compliance
• Hemodynamic disturbances
• V/Q mismatch
• Total dependence on ventilator

24. Pressure controlled CMV
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Ventilator gives pressure limited, time cycled breaths thus preset inspiratory
pressure is maintained.
Decelerating flow pattern.
Peak airway/alveolar pressure is controlled but TV,
minute volume & alveolar volume depends on lung
compliance, airway resistance, R/R & I:E ratio.

25. PC-CMV
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Advantages
• Less PAW, thus chances of Barotrauma and hemodynamic disturbances are
less.
• Even distribution of gases in alveoli
• In case of leakage, compensation for loss of ventilation is better as gaseous
flow increases to maintain preset pressure.
Disadvantages
• Asynchrony
• TV dec. if there is dec. lung compliance or inc. airway resistance, thus causes
hypoventilation and alveolar collapse.

26. Assisted control ventilation
(AC Mode)
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• Ventilator assists patient’s initiated breath, but if not triggered, it will deliver
preset TV at a preset respiratory rate (control).
• Mandatory mechanical breaths may be either
patient triggered (assist) or time triggered
(control)
• If R/R > preset rate, ventilator will assist,
otherwise it will control the ventilation.

27. AC mode ventilation
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Advantages
• Dec. patients work of breathing.
• Better patient ventilator synchrony.
• Less V/Q mismatch.
• Prevents disuse atrophy of diaphragmatic muscle.
Disadvantages
• Alveolar hyperventilation
• Development of high intrinsic PEEP in pts with obstructive ds.
• Inc . mean airway pressure causes hemodynamic disturbances.

28. Intermittent mandatory ventilation
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Ventilator delivers preset number of time cycled mandatory breaths & allows
patient to breath spontaneously at any tidal volume in between.
Advantages
• Lesser sedation
• Lesser V/Q mismatch
• Lesser hemodynamic disturbances
Disadvantage
• Breath stacking- lung volume and pressure could increase significantly, causing
Barotrauma

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30. Synchronized intermittent
mandatory ventilation (SIMV)
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Ventilator delivers either assisted breaths to the patient at the beginning of a
spontaneous breath or time triggered mandatory breaths.
Synchronization window- time interval just prior to time triggering.
Breath stacking is avoided as mandatory breaths are synchronized with
spontaneous breaths.
In between mandatory breaths patient is allowed to take spontaneous breath at
any TV.

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It provides partial ventilatory support

33. SIMV mode
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Advantages
• Maintain respiratory muscle strength and avoid atrophy.
• Reduce V/Q mismatch d/t spontaneous ventilation.
• Decreases mean airway pressure d/t lower PIP & inspiratory time
• Facilitates weaning.
Disadvantages
• Desire to wean too rapidly results in high work of spontaneous breathing &
muscle fatigue & thus weaning failure.

34. Positive End expiratory pressure
mode
(PEEP)
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An airway pressure strategy in ventilation that increases the end expiratory or
baseline
airway pressure greater than atmospheric pressure.
 Used to treat refractory hypoxemia caused by intrapulmonary shunting.
 Not a stand-alone mode, used in conjugation with other modes.
Indications
• Refractory hypoxemia d/t intrapulmonary shunting.

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PEEP reinflates collapsed alveoli & maintain alveolar inflation during
exhalation.
PEEP

Increases alveolar distending pressure

Increases FRC by alveolar recruitment

Improves ventilation

Increases V/Q

Improves oxygenation

PEEP Physiology

36. PEEP Complications
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Complications
• Dec. venous return and cardiac output.
• Barotrauma
•  ICP d/t impedance of venous return from head.
• Alteration of renal function & water imbalance.

37. Continuous positive airway
pressure (CPAP)
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PEEP applied to airway of patient breathing spontaneously
Indications are similar to PEEP, to ensure patient must have adequate lung
functions that can sustain eucapnic ventilation.

38. Pressure support ventilation
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• Supports spontaneous breathing of the patients.
• Each inspiratory effort is augmented by ventilator at a preset level of
inspiratory pressure.
• Applies pressure plateau to patient airway during spontaneous br.
• Can be used in conjugation with spontaneous breathing in any ventilator
mode.

39. PSV
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Commonly applied to SIMV mode during spontaneous ventilation to
facilitate weaning
With SIMV, PS Inc.
• patient’s spontaneous tidal volume.
• Dec. spontaneous respiratory rate.
• Decreases work of breathing.
• Addition of extrinsic PEEP to PS increases its efficacy.

40. PSV
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Disadvantages
• Not suitable for patients with central apnea. (hypoventilation)
• Development of high airway pressure. (hemodynamic disturbances)
• Hypoventilation, if inspiratory time is short.

41. Inverse ratio ventilation
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Used to promote oxygenation esp. in ARDS.
Normal I:E ratio is 1:1.5 – 1:3, in IRV I:E is 2:1 – 4:1
Improves oxygenation by
• Reducing intrapulmonary shunting.
• Improving V/Q mismatch.
• Decreasing dead space ventilation.
• Increasing mean airway pressure.
• Presence of auto PEEP.

42. Criteria for weaning from
ventilation
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• Obtain ABG (Arterial Blood Gas) analysis.
• Obtain chest x-ray.
• Ensure stable hemodynamic status.
• Ensure adequate neuromuscular control to
perform adequate ventilation.
• No neuromuscular blocking agents
needed.

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