This document provides an overview of mechanical ventilation including its history, types of ventilators, modes of ventilation, indications, complications, ventilator settings for specific diseases, weaning methods, and newer methods. It discusses positive pressure ventilation and various modes like CMV, A/C, IMV, SIMV, and PSV. Complications of mechanical ventilation include barotrauma, volutrauma, VAP, and oxygen toxicity. Optimizing ventilator settings can reduce organ failure and duration of ventilation. Non-invasive ventilation has increased and facilitates weaning. Newer modes continue to be developed to improve ventilation support.

1. Ventilator in
critical care
Presenter : Dr. Dhileeban Maharajan
Moderator : Prof. Lk. Sharatchandra

2. Contents
1. History
2. Types of Ventilators
3. Modes of Mechanical Ventilation
4. Indications
5. Complications
6. Ventilator setting in Specific diseases
7. Weaning
8. Newer methods

3. Introduction
• Mechanical Ventilation - Common life saving intervention
• Required for assisting and replacing spontaneous
breathing
• Poor ventilatory management can inflict serious pulmonary
and extra-pulmonary damage
• Optimizing ventilatory parameters reduces overall duration
of mechanical ventilation and organ failure
• Upsurge in utilization of non-invasive ventilation has

4. History
• 5th century – Hippocrates (Treatise on air)
• 1530 – Paracelus – Pump air into patients mouth
• 1653 – Andreas Vesalius – Tracheostomy in dog
• 1744 – John Fothergill – Mouth to mouth breathing
• 1880 – First endotracheal intubation tried
• 1929 – Drinker and Shaw – Negative pressure ventilation
• 1963 – Positive pressure ventilation
• 1971 – Gregory et al – CPAP

5. 1. Iron lung
2. Cuirass
3. Body suit
Negative Pressure Ventilation
Negative pressure outside thorax
Expansion of thoracic cage
Fall in pleural pressure
Air enter into the lungs
Examples:

6. Positive Pressure
Ventilation
Airway pressure is applied at the patient's airway through an
endotracheal or tracheostomy tube. The positive nature of the
pressure causes the gas to flow into the lungs until the ventilator
breath is terminated. As the airway pressure drops to zero, elastic
recoil of the chest accomplishes passive exhalation by pushing the
tidal volume out.
• Polio epidemic in Scandinavia – 1950
• Manual positive pressure ventilation
• Mortality reduced 80 to 25%

7. Positive Pressure
Ventilation - Cont
• Mode: (Flow, Pressure, Time)
o Manner in which ventilator breaths are triggered, cycled and
limited
• Trigger: (Flow, Pressure)
o Either an inspiratory effort or time based signal, defines
what the ventilator senses to initiate an assisted breath
• Cycle: (Volume, Flow, Pressure, Time)
o Factors that determine the end of inspiration
• Limiting factors:
o Operator specified values such as airway pressure, to
prevent injury to lungs

8. Types of support
• Control mode
o Delivers preset tidal volume once it triggered
regardless of patient effort
• Support mode
o Provides inspiratory assistance (Requires adequate
respiratory drive)

9. Methods of ventilatory
support
• Continuous mandatory ventilation (CMV)
• Assist – Control ventilation (A/C)
• Intermittent mandatory ventilation (IMV)
• Synchronous intermittent mandatory ventilation
(SIMV)
• Pressure support ventilation (PSV)
• Noninvasive ventilation
o CPAP
o BIPAP

10. Continuous Mandatory
Ventilation (CMV)
• Preset interval breath regardless of patients effort
• Patients should be sedated and paralysed (NM blockers)
• Used for patients fights the ventilator during initial
stages, tetanus, seizures, complete rest for 24 hours,
crushed chest injury.

12. Assist Control
Ventilation (A/C)
• Preset breath in coordination with respiratory effort
• Delivers full assisted tidal volume
• Spontaneous breathing not allowed
• If patient had appropriate ventilator drive, allows patient to
control frequency and minute volume to normalize PaCO2
• To provide full ventilatory support for patients (full work of
breathing)
• Used for patients having stable respiratory drive (at least 10
/min)

14. Intermittent Mandatory
Ventilation (IMV)
• Breaths at preset interval
• Spontaneous breath allowed
• Allow patients breath in addition to ventilator delivered
breaths.
• Breath stacking – increased risk of barotrauma

16. Synchronous Intermittent
Mandatory Ventilation (SIMV)
• Preset breaths in coordination with respiratory effort
• Spontaneous breathing allowed
• Time interval just prior to time triggering in which
ventilator is responsive to patients spontaneous
inspiratory efforts is called as synchronization window
mostly 0.5 sec (manufacturer set)
• SIMV maintains respiratory muscle strength, reduces V/Q
mismatch, decreases mean airway pressure, facilitates
weaning

18. Pressure support
ventilation• For spontaneously breathing patient
• To limit barotrauma and work of breathing
• Pressure support according to inspiratory flow
• when the patient triggers ,pressure supported breath is
delivered by demand valves which generates high flow
to increase airway pressure to pressure limit and
maintains pressure plateau (demand and servo valves)
for the duration of patients spontaneous inspiratory
efforts.
• PSV used with SIMV to facilitate weaning

20. Noninvasive ventilation
(NPPV)
• Ventilatory support through mask
• Decreases the intubation by 20%
• CPAP and BiPAP
• Used in
o COPD acute exacerbation
o Cardiogenic pulmonary edema
o Post-extubation respiratory
failure in hypercapnic patients
o Pneumonia in
immunocompromised patients
Contraindications :
• Cardiac or Respiratory arrest
• Severe encephalopathy
• Hemodynamic instability
• Facial trauma or surgery
• Upper airway obstruction
• High risk aspiration
• Inability to clear secretions

21. Noninvasive ventilation –
Cont..
• Place the patient in upright or sitting position
• Choose a proper fitting mask
• Attach the interface and circuit to ventilator
• Allow the patient to hold the mask
• Monitor oxygen saturation
• Secure the mask
• Titrate the pressure settings
• Check for any leaks
• Monitor RR, HR, Saturation, Minute ventilation, Exhaled Tt
• Obtain ABG within one hour
(Protocol for initiating NIV)

22. • Higher level consciousness
• Younger age
• Less severe abnormalities
• Minimal air leakage
• Intact dentition
• Synchronous breathing
• Absence of pneumonia
• Positive initial response
o Correction of pH
o Decreased respiratory rate
o Reduced PaCO2
Noninvasive ventilation –
Cont..
• Nasal bridge ulcer and necrosis
• Conjunctival irritation
• Gastric insufflation
• Ventilator asynchrony
• Claustrophobia
• Risk of aspiration
Predictors of success
Disadvantages

23. Indications for mechanical
ventilation
• Bradypnoea or apnoea with respiratory arrest
• Acute lung injury and acute respiratory distress syndrome
• Tachypnoea (respiratory rate >30 breaths per minute)
• Vital capacity less than 15 mL/kg
• Minute ventilation greater than 10 L/min
• PaO2 with a supplemental FIO2 of less than 55 mm Hg
• Alveolar-arterial gradient of oxygen tension (A-a DO2) with
100% oxygenation of greater than 450 mm Hg

24. Indication – Cont…
• Clinical deterioration
• Respiratory muscle fatigue
• Obtundation or coma
• Hypotension
• Acute partial pressure of carbon dioxide (PaCO2) greater than
50 mm Hg with an arterial pH less than 7.25
• Neuromuscular disease

25. Indications

26. Positive End Expiratory
Pressure (PEEP)
• Positive end expiratory pressure (PEEP) refers to the
application of a fixed amount of positive pressure during mechanical
ventilation cycle
• Continuous positive airway pressure (CPAP) refers to the
addition of a fixed amount of positive airway pressure to spontaneous
respirations, in the presence or absence of an endotracheal tube.
• PEEP and CPAP are not separate modes of ventilation as they do not
provide ventilation. Rather they are used together with other modes of
ventilation or during spontaneous breathing to improve oxygenation,
recruit alveoli, and / or decrease the work of breathing

27. PEEP - Advantages
• Ability to increase functional residual capacity (FRC) and keep
FRC above Closing Capacity
• The increase in FRC is accomplished by increasing alveolar
volume and the recruitment of alveoli that would not otherwise
contribute to gas exchange. Thus increasing oxygenation and
lung compliance
• The potential ability of PEEP and CPAP to open closed lung
units increases lung compliance and tends to make regional
impedances to ventilation more homogenous.

28. Physiology of PEEP
Reinflates
collapsed alveoli
and maintains
alveolar inflation
during exhalation
PEEP
Decreases alveolar distending pressure
Increases FRC by alveolar recruitment
Improves ventilation
Increases V/Q, improves
oxygenation, decreases work of
breathing

29. Complications of Mechanical
Ventilation
• Laryngeal injury
• Pharyngeal laceration
o Infection of the retro
pharyngeal space
o Mediastinitis
o Pneumothorax
• Tracheal rupture
• Nasal injury and epistaxis
• Dental trauma
• Cervical spine injury
• Esophageal intubation
• Right mainstem intubation
• Cardiac arrhythmia
• Aspiration
• Bronchospasm
Peri- intubation complication

30. • Endotracheal tube obstruction
• Endotracheal tube migration
• Self-extubation
• Cuff leak
• Barotrauma and Volutrauma
o Subpleural air cyst
o Pneumothorax
o Pneumomediastinum
o Pneumoperitoneum
o Subcutaneous emphysema
Acute complications that can occur at any time
during mechanical ventilation
• Biotrauma
• Hypotension
• Dynamic hyperinflation
• Atelectasis
• Alveolar hypoventilation or
hyperventilation
• Gastric dilation
• Inadvertent disconnection
from ventilator
• Machine failure

31. • Peri-oral pressure sores
• Nasal necrosis
• Sinusitis
• Serous or purulent otitis media
• Pneumonia
• Tracheomalacia
• Tracheo-esophageal fistula
• Oxygen toxicity
Mechanical Ventilation - Delayed complications

32. Ventilator induced lung injury
(Barotrauma)
• Prevalence – 10%
• Large Tidal volume and elevated peak inspiratory and plateau
pressure – Risk factors
• Barotrauma refers to rupture of the alveolus with subsequent
entry of air into the pleural space (pneumothorax) and/or the
tracking or air along the vascular bundle to the mediastinum
(pneumomediastinum)
• Decrease the inspiratory-to expiratory ratio is important to
prevent barotrauma

33. • local overdistention of normal alveoli
• lung-protective ventilation strategy is recommended
Ventilator induced lung injury
(Volutrauma)

34. Oxygen Toxicity
• Oxygen toxicity is due to the production of oxygen free radicals
such as superoxide anion, hydroxyl radical, and hydrogen
Peroxide
• Reported in patients given a maintenance FIO2 of 50% or
greater
• Clinician should attempt to attain an FIO2 of 60% or less within
the first 24 hours of mechanical ventilation
• PEEP should be considered a means to improve oxygenation
while a safe FIO2 is maintained

35. Ventilator Associated
Pneumonia (VAP)
• Incidence 1 to 4 cases per 1000 ventilator days
• Rate of 3% per day for the first 5 days, 2% per day for next 5
days
• VAP is defined as a new infection of the lung parenchyma that
develops within 48 hours after intubation
• Fever, leukocytosis, and purulent tracheobronchial secretions.
• Qualitative and quantitative cultures of protected brush and
bronchoalveolar lavage specimens may help
• First 48 hours after intubation - Flora of the upper airway,
including Haemophilus influenza and Streptococcus pneumonia

36. VAP – cont..
• After this early period, gram-negative bacilli such as
Pseudomonas aeruginosa, Escherichia coli, Acinetobacter,
Proteus, and Klebsiella species predominate
• Staphylococcus aureus, especially methicillin-resistant S aureus
(MRSA), typically becomes a major infective agent after 7 days
• Initial therapy - with broad-spectrum antibiotics and change the
antibiotic after the culture sensitivity report

37. Intrinsic PEEP
• Most frequently occurs in patients with COPD or asthma who
require prolonged expiratory phase of respiration
• This problem occurs, a portion of each subsequent tidal volume
may be retained in the patient's lungs, a phenomenon sometimes
referred to as breath stacking
• Results in barotrauma, volutrauma
• The normal inspiratory to expiratory ratio (I:E ratio) is 1:2. In
patients with obstructive airway disease, the target I:E ratio
should be 1:3 to 1:4.

38. Breath stacking

39. Ventilator Setup
• Assist – Control mode
• Tidal volume depending upon the lung status
o Normal - 12mL/kg; COPD – 10mL/kg; ARDS – 6-8mL/kg
• Rate of 10 – 12 breaths/min
• FIO2 of 100%
• PEEP only as indicated

40. Ventilator setting in COPD
and asthma
• Permissive hypercapnia
• Reduce the expiratory rate
• Low set tidal volume
• Increase the expiratory flow time
• NPPV reduced the endotracheal
intubation by 59%
High airway pressure
Breath stacking
Intrinsic PEEP
Barotrauma

41. • Compliance reduced and dead space increased
• Lung protective ventilation
o Low tidal volume ( Close to 6ml/kg BW)
o Prevent plateau pressure exceeding 30cmH2O
o Lowest possible FIo2 to keep the Spo2 at >90%
o Adjust the PEEP to maintain alveolar patency
• Early prone positioning
Ventilator setting in ARDS

42. • To decrease the work of breathing and oxygen demand of
the respiratory muscles
• Arrhythmia common with hypocapnia
• In CHF - CPAP or BiPAP reduce preload
• Potential effects of PEEP in LV dysfunction
o Reduce venous return and preload
o Increased FRC lead to increased pulmonary patency
o Compression may increase afterload
Ventilator setting in Heart
Disease

43. • Prevent aspiration
• Hyperventilation  Reduce the intracranial pressure
• Maintain PaCO2 between 30 to 39mmHg
• Recent studies suggest poor outcome
Ventilator setting in Traumatic
Brain Injury

44. Weaning
• Unsupported spontaneous breathing trials(SBT)
o The machine support is withdrawn
o T-Piece (or CPAP) circuit can be attached
• Intermittent mandatory ventilation (IMV) weaning
o The ventilator delivers a pre-set minimum minute volume
o Synchronized (SIMV) to the patient's own respiratory efforts
• Pressure support weaning
o Patient initiates all breaths and these are 'boosted' by the ventilator.
o Gradually reducing the level of pressure support,
o Once the level of pressure support is low (5-10 cmH2O above PEEP), a
trial of T-Piece or CPAP weaning should be started

45. Weaning- Cont…
• Lung injury is stable or resolving
• Gas exchange adequate
o Low PEEP (<8cmH2O)
o Low FIO2 (<0.5)
• Stable hemodynamic variables
• Able to initiate spontaneous breath
• Absence of infection or fever
Indications Failed SBT
• Resp. Rate >35 for >5min
• Heart Rate >140/min
• SPO2 <90% for >30sec
• Systolic BP >180 or <90
• Sustained increased WOB
• Cardiac dysrhythmia
• pH <7.32
10 to 15% patient require reintubation

46. Newer Modes
• Dual modes
o Pressure regulated volume control(PRVC) ventilation
o Volume support ventilation (VSV)
o Variable pressure control mode
o Volume assured pressure support ventilation
• Proportional assist ventilation
• Inverse ratio ventilation
• High frequency jet ventilation
• Neurally adjusted ventilatory assist ventilation (NAV)
• Extracorporeal membrane oxygenation (ECMO)

47. Summary
• Technological advances added new methods in MV
• NPPV is an important treatment modality prevents the
need for endotracheal intubation
• Recent guidelines suggest that the use of low tidal
volume in ARDS associated with favorable outcome
• Weaning guidelines have shown improved outcome
• Although MV is life saving, it is fraught with a plethora of
complications

48. Thank you
REFERENCE
• Pittsburgh critical care medicine – Mechanical Ventilation; Second Edition
• Ashfaq Hasan – Understanding mechanical ventilation;
• Harrison’s Principles of internal medicine; 20th Edition
• API Textbook of Medicine; 11th Edition
• Medicine Update 2019; Volume 29