Basics

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Basics principles of
mechanical ventilation

• g.k.kumar

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Basics principles of ventilation

• -What is ventilator
• -How ventilators work
• -How to use
  
  
  

?
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• Ventilator
• The Machine delivers O2 removes Co2 with out
  harming the patient.
• The Ventilator should have capacity of delivering
  a consistent tidal volume under all adverse
  conditions of lung disease.

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• Mechanical Ventilation
• The process / method by applying (intermittent)
  positive airway pressure supplementation of
  Inspired O2 to achieve desirable oxygenation.

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• GOALS of Mechanical Ventilation
• Good ventilation (known by pa Co2)
• Oxygenation (by pa O2).
• Alveolar recruitment by peep
• Lowest O2 supplement.
• Synchrony between patient Ventilation.
• Safe ? No Negative hemodynamic effect
  
• No Barotraumas
• No auto PEEP

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• Classification of Mechanical ventilation
• Positive / Negative pressure ventilation.
• Partial / full ventilation.
• Invasive / Non invasive ventilation.

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Components of ventilator

1. Power source-electrical/pneumatic/both
2. Control systems-circuits, control panel
3. Display systems

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V
Central unit
oxy
Exp.limb
Pt
blender
Insp. limb
V
P
Fio2
T
Humneb
compressor
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PHASES VARIABLES

• INITIATION OF INSPIRATION-TRIGGER
• INSPIRATION-LIMIT
• MAINTENANCE OF INSPIRATION-CONTROL
• CHANGING TO EXPIRATION-CYCLE

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• Triggering variable
• Triggering is a method of starting the
  inspiration
• Types Pressure Triggering
• Flow Triggering - No lag time
• Time Triggering -Less effort

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• Control Variable
• Setting that maintained thro out inspiration
• Type Volume control.
• Pressure control.

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• PCV
  VCV
• Vt. Variable set
• PIP SET lesser
  variable more
• Plateau pressure Set Variable
• Inspiratory flow decelerating type
  fixed flow type
  sinusoidal/square
• Inspiratory time set set
• Respiratory rate Set Set
• Barotrauma Less More
• Leak compensation for minor leak nil
• Patients acceptance good -

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• Limit Variable
• Setting that can't be exceeded during inspiration
• Type Pressure limit- psv
• volume limit
• Flow limit

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• Cycle variable
• Method of termination of inspiration, I.e.
  changing over from inspiration to expiration.
• Types Volume cycle
• Pressure cycle
• Time cycle
• flow cycle.

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Compliance-resistance-volume
Cl
Ccw
compliance
PAi
Vt
PA range
Raw
PAe
C?V /?P
RPIP-Pp / F
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(No Transcript)
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Normal resistance Un intubated patient 0.6 -
2.4 cm H20 / L / Sec, .
at 0.5L /sec Intubated patient
6cm H20 / L / Sec
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Ventilatory controls-inter relation
MV
Ti
T
IE
Te
Vt
f
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• Ventilator Modes
• Combination of breath type and phase
  variable.
• Conventional modes Recent modes
  Newer modes
• CMV MMV VAPS, PAug
• A/C MV APRV VS,
  PRVC
• IMV SIMV BIPAP
  AUTOFLOW
• CPAP PEEP IRV
  AUTOMODE
• VCV DLV PAV,PPS
• PSV HFJV ASV

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• Controlled mechanical ventilation
• 
  -CMV
• All breaths are delivered by ventilator.
• No Patient participation.
• Set Vt. Delivered at set RR
• Requires sedation neuromuscular blockade.
• Time initiated
• Volume limited
• Volume cycling

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• CMV
• Indications
• Patient with no efforts / complete respiratory
  failure.
• When negative inspiratory effort contra
  indicated.
• eg.flail chest.
• During anesthesia.
• Disadvantages
• Patient participation not
  allowed.
• Heavy sedation relaxant need
• Long term CMV ? Respiratory muscle weakness.
• Varying PIP according to lung compliance
  patient efforts.

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• Assist / Control Mechanical ventilation
• Patient can trigger ventilation at a rate more
  than set RR
• All breaths are delivered at set volume , set
  time set pressure
• Triggering ? pressure / flow (spontaneous)
• Time (Mandatory)
• Limiting ? Volume
• Cycling ? Volume
• Patient can vary RR only but not vt.

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Assist / Control Mechanical Ventilation

• Indications
• Patient with normal drive but with respiratory
  weakness ? Recovering patient.
• To preserve patient efforts
• Weaning.
• Disadvantages
• Rapid triggering ? Hyperventilation
• Hypotension
• Flow rare should be adjusted according to the
  need.
• If RR lt RR ? CMV mode.

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• IMV / SIMV
• The patient receives the Mandatory set Vt at set
  RR.
• The set Mandatory breaths are synchronized with
  patient efforts.
• Between the mandatory breaths the patient can
  breath spontaneously
• Spontaneous breath vt depends on
• ? Patients respiratory effort
• ? PS
• Triggering - Pressure
• Limiting - Volume
• Cycling - Time

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• IMV / SIMV
• Advantages
• The mandatory breaths are synchronized
  with patients Spontaneous efforts.
• Hyperventilation is less
• More active participation of patient
• Disadvantages
• More WOB

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• A/CMV SIMV
• Patient decides only RR lt -- gt patient effort
  decides RR vt.
• Less WOB as only lt -- gtmore WOB as
  Initiation by patient patient
  has to .
  operate demand
• . flow
  system
• Possibility of hyper ventilation lt -- gt No

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• CPAP
• A mode is which positive pressure is applied tho
  out the respiratory cycle using during
  spontaneous ventilation.
• (Pr applied in mechanical ventilation PEEP)
• No Ventilatory assistance
• Positive Pressure causes
• Prevention of alveolar collapse alveolar
  recruitment
• Î FRC Atelecasis
• FlO2 requirement

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• CPAP PEEP
• Pr applied and base line Pr. Applied with
• Pr elevated when ventilatory some ventilatory
  Assistance is nil.
  Assistance present.

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• PEEP
• Applied when Fio2 requirement is 50 - 60.
• Best Peep PEEP titrated to achieve optimal
  respiratory system compliance.
• Optimal Peep Titration of PEEP until Qs /Qt is lt
  15

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• Volume Control Ventilation
• Vt. Delivery is constant according to pressure
  regardless of changes in airway resistance or
  respiratory system compliance.
• VCV is given when constant MV is needed (eg,
  patient with Î ICT)

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• Pressure control ventilation
• The pressure applied to the airways is constant
  regardless of airway resistance and compliance.
• Constant pressure is delivered throughout
  inspiration at set RR
• Time initiated pressure limiting time cycling.
• Vt may vary according to patient lung conditions.
• PCV avoids over distention in patient with ALI,
  because PIP can be set.
• Settings
• Preset pressure is equal to half of present PIP.
• PEEP half of present PEEP (if gt 8cm H2 O)
• I E is 12

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• PCV
  VCV
• Vt. Variable set
• PIP SET lesser
  variable more
• Plateau pressure Set Variable
• Inspiratory flow decelerating type
  fixed flow type
  sinusoidal/square
• Inspiratory time set set
• Respiratory rate Set Set
• Barotrauma Less More
• Leak compensation for minor leak nil
• Patients acceptance good -

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• Pressure Support Ventilation (Psv)
• Patients spontaneous activity is assisted by
  delivery of a preset amount of inspiratory
  positive pressure.
• Patient triggers ? set pressure is maintained
  throughout inspiration.
• Pressure initiated.
• Pressure limiting .
• Flow Cycling
• As flow reaches 25 of peak inspiratory flow /5
  litres / min

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• Pressure Support Ventilation (Psv)
• Low PSV to overcome the patients WOB
  associated with ETT and circuits.
• PSV max to achieve Vt of 10 -12 ml / Kg
• - may require upto 40 -50 cm H2O
• Can be used alone as full ventilatory support
  or with SIMV.
• Can be used as non invasive ventilatory support
  up to 20cm H2O2 for transient Ventilatory
  support ( Narcotic overdose, asthma, acute
  exacerbation of COPD).

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• Mandatory Minute Ventilation (MMV)
• Preset MV is selected.
• The Ventilator calculates the patients
  spontaneous MV.
• It patients spontaneous MV lt set MV, ventilator
  assists to achieve set MV
• Ventilatory assisstance may be
• - Volume controlled SIMV breaths Î RR
  /Vt
• - Î PSV

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Mandatory Minute Ventilation (MMV)

• ADVANTAGES
• MV guaranteed
• Useful as weaning mode
• DISADVANTAGES
• RR may cause dead space ventilation even with
  acceptable MV.
• Respiratory muscle fatigue may develop (so high
  RR alarm should be activated.

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Mandatory Minute Ventilation (MMV)

• INDICATIONS
• During weaning period
• To aspiratory flow and WOB
• To overcome ETT/circuit resistance

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BILEVEL POSITIVE AIRWAY PRESSURE
VENTILATION(BIPAP)

• A pressure controlled ventilation
• Allows unrestricted spontaneous breathing at any
  point of ventilatory cycle
• Time cycled changes of pressure application.
• Independent positive airway pressure to
  inspiration expiration
• Inspiratory set pressure is called IAP/T high
  Expiratory set pressure is called EAP/T low
• Usual IAP is 8 cm H2O EAP is 3 cm H2O
• Triggerflow, Limitpressure
  Cycletime

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BILEVEL POSITIVE AIRWAY PRESSURE
VENTILATION(BIPAP)

• IAP causes better ventilation Paco2
• EAP causes better oxygenation Pao2
• Types
• --CPAPPS
• --Two alternating CPAP level
• --APRV

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BILEVEL POSITIVE AIRWAY PRESSURE
VENTILATION(BIPAP)

• ADVANTAGES
• Non invasive ventilation
• Useful inend stage COPD
• ---restricted chest wall diseases
• ---neuromuscular diseases
• ---nocturnal hypo ventilation
• A weaning mode.

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AIRWAY PRESSURE RELEASE VENTILATION(APRV)

• A CPAP circuit with release valve at expiratory
  limb driven by time device
• APRV is a CPAP system causing .
  alveolar ventilation by briefly interrupting
  CPAP.

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APRV.,

• Release valve opens for 1-2sec.
• Pr drops to lower level-low CPAP(0to-2cmH2O)
• Lung volume less than FRC in expiration
• alveolar ventilation CO2 elimination
• Reapplication of CPAP by closing valve- Higher
  CPAP(10to 12 cm H2O)
• FRC oxygenation.

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APRV.,

• ADVANTAGES
• Lesser PIP ,so less hemo dynamic changes.
• To alveolar ventilation in ALI of mild to
  moderate.
• A weaning mode.

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INVERSE RATIO VENTILATION(IRV)

• IE gt1
• PC-IRV / VC-IRV
• Ti with set pr opening of stiff alveoli
  units improved oxygenation
• Te not allowing alveoli to collapse
• development of intrinsic PEEP
• reduction of shunting

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IRV,

• Improve oxygenation by
• Reducing intra pulmonary shunting
• Improvement of V/Q matching
• Decreased dead space ventilation
• Increased MAP intrinsic PEEP
• Useful when high FiO2 high PEEP to be avoided

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NEWER MODES

1. Dual modes VAPS, Paug,
   
   -
   VS, PRVC, Autoflow, VPC
2. Switching modes Automode
3. Proportional modes PAV,PPS.
4. Adaptive modes ASV

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DUAL MODES

• Combination of 2modes of ventilation(PCVVCV)
  to deliver guaranteed Vt/MV
• Volume guaranteed pr targeted ventilation
• Mode changes occur
• with in a breath-VAPS,Paug
• over several breaths-VS,PRVC,Auto
  flow,VPC

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DUAL MODES - CHANGES WITH IN BREATH

• VAPSvolume assured pr support-T bird,bird8400st
• Paug pr augmented ventilation-bear 1000
• Vt guaranteed variable pr limited modes
• During inspiration,the ventilator monitors Vt
• if desired Vt delivered before flow drops---PSV
• if desired Vt not delivered before flow drops
• flow continued at set pr support level till
  adequate
• Vt delivered.

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DUAL MODES - CHANGES WITH IN BREATH

• Trigger patient
  patient
• Limit -- pressure
  variable pr
• Cycle -- flow
  volume
• PSV
  Paug
• 
  VAPS

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DUAL MODES - CHANGES OVER SEVERAL BREATHS

• PRVCPr regulated VC-siemen300
• VSvolume supportservo 300
• Auto flowDragerE4
• VS-volume assured PSV
• PRVC-volume assured PCV
• Vt measured over several breathsadequate MV
  achieved by changing PS/PC mode for remaining
  breaths.

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DUAL MODES - CHANGES OVER SEVERAL BREATHS

• AUTOFLOW
• Autoflow alters the function of inspiratory and
  expiratory valves
• Allowing patient to receive inspiratory flow
  demand
• Auto flow provides better ventilatory tolerance
• A weaning mode

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Switching modes

• Ventilator can switch modes according to
  monitored information
• Automodeservo300
• Switching between control /support mode depending
  on patients respiratory pattern
• Monitoring of patients respiration over fixed
  time period if 2consecutive effort PSV
  . -- if no efforts - PCV

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Proportional modes

• PAVproportional assist ventilation-PB840
• PPS proportional PS-Evita-E4
• Proportional modes are assisting spontaneous
  ventilation
• PPVa support mode in which pr, flow,volume are
  set proportional to patients inspiratory efforts

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Proportional modes

• The more effort pt exerts-the more support the
  machine provides
• PAV allows patients to comfortably reach
  whatever the ventilatory pattern that suit their
  need.

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Adaptive modes

• ASV-Adaptive support ventilation
• Uses pr targeted breaths to assure a target MV
  with decreased WOB
• ASV adapts to the changing capabilities of
  patients lung conditions.
• More efforts the patient does less
  - support the
  machine provides.

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Adaptive modes

• ASV calculate the over all MV combination of
  volume guaranteed PSV(VS) volume guaranteed
  PCV(PAVC)
• ASV can ventilate the patient from acute stage to
  a weaning stage.

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Weaning

• Wearing off primary pathology
• Elimination of effects of sedation relaxants
• Absence of sepsis
• No metabolic / electrolyte abnormality
• Involvement of patient
• Nutritionally stable
• Good stable CVS