Dr. Kannan, resident, pediatrics, MGMCRI

1. THEBASICSOF
VENTILATOR SETTINGS
SERIES2
DR. C. KANNAN
POST GRADUATE
PEDIATRICS
MGMCRI

2. REVISION OF PART 1
TIDAL VOLUME (VT)
• Volume of gas that flows in and out of the chest during quiet breathing .
• Normal tidal volume in children – 6-12ml/kg
MINUTE VENTILATION (MV)
• Product of tidal volume and ventilator rate.
PEAK INSPIRATORY PRESSURE (PIP)
• Highest that can be met during the inspiratory period

3. POSITIVE END EXPIRATORY PRESSURE (PEEP)
• PEEP is the baseline positive pressure in the airway during expiration.
• It is designed to keep alveoli from collapsing at the end of expiration.
• PEEP prevents derecruitment of alveoli and it has protective effect in
prevention of ventilator associated lung injury.
• Normal PEEP 3-5cmH2O
INSPIRATORY TIME AND I:E RATIOS
• Normal I:E ratio is usually 1:1.5 to 1:2
• Altered by adjusting the inspiratory time.

4. DICUSSION
• Anatomy of the ventilator
• Modes in ventilator
• How to start a ventilator ?
• Disease based strategy

5. ANATOMY
• Purified compressed air & oxygen
• Either inbuilt cylinders or from wall outlet
• Sophisticated software
• Ensures the pattern of breath delivery
• As set by the caregiver
• Humidifier / Heat & Moist exchanger (HME)

6. Contd.,
• Ventilator hardware
• Monitors
• Pressure gauges / Flow & Volume sensors / Alarms / Graphics
• Circuits – Reusable / Disposable
• Two limbs – Inspiratory / expiratory
• Heated wire present in both limbs - Prevents condensation
• Water traps in dependent position in both limbs

8. MODES

9. DETERMINANTS OF MODES
• BREATH TYPE
• Mandatory
• Spontaneous
• Assisted
• CONTROL VARIABLE
• Pressure control
• Volume control
• Dual control
• TIME OF BREATH DELIVERY
• CMV
• Spontaneous
• Assisted

10. MODES/ACTION BY TRIGGERING LIMITING CYCLING
MANDATORY Ventilator ventilator ventilator
ASSISTED Patient / venti Patient / venti Patient / venti
SPONTANEOUS Patient Venti / patient Patient
1. BREATH TYPE

11. 2. CONTROL VARIABLE
A. PRESSURE CONTROLLED BREATHS
• Pressure is set by clinician (Independent variable)
• PIP / PEEP / Rate / Inspiratory time (Ti)
• Volume (VT) can change (Dependent variable)
• Determined by
• Delta P (PIP – PEEP)
• Compliance / Airway resistance / Circuit / Patient effort
• Flow waveform is decelerating ( Pressure gradient )

12. PRESSURE CONTROL FLOW CHART

13. • Advantages
• Risk of barotrauma is less
• Improves gas distribution in heterogeneous lung mechanics
• Satisfy patient demands in spontaneous breaths
• Where airway is not fully sealed
• Uncuffed tracheal tubes
• Bronchopleural fistulas
• Airleak syndromes

14. • Disadvantages
• PC does not guarantee minute volume
• Tidal volume changes depends upon compliance
• If lung is stiff - TV reduces
• If lung compliance improves - TV increases - Volutrauma
• Hence close clinical monitoring is essential
• To prevent hypo / hyperventilation

15. B. VOLUME CONTROLLED BREATHS
• Used in older children
• Part of mandatory controlled mode (CMV / SIMV)
• Tidal volume is set by clinician (Independent variable)
• Pressure can change (Dependant variable)
• Cycling mechanism is controlled by
• Pre-set time (Ti) / Pre-set Volume
• Flow wave form is constant

16. VC – FLOW CHART

17. • Advantages
• Minute ventilation is guaranteed
• Important in airway diseases ( B. Asthma / Bronchiolitis)
• Disadvantages
• High risk of barotrauma (Pressure fluctuates)
• Flow is constant
• Hence cant satisfy patient demand in spontaneous breaths
• Smaller tidal volume will not be accurately delivered
• In case of altered lung mechanics
• Divided B/W circuit / Airways / Lungs

18. • Disadvantages
• If the patient worsens by
• Eg., Takes more tidal volume by increased WOB
• Ventilator senses high exhaled TV and reduces pressure
• Reduced pressure support, further worsens WOB

19. 3. TIMING OF BREATH DELIVERY
A. CONTROLLED MANDATORY / MECHANICAL VENTILATION (CMV)
• CMV may utilise pressure / Volume / Dual control
• Breaths initiated, limited and cycled by ventilator
• Patient has no active role
• Used in
• Insufficient / Absent respiratory drive
• Completely sedated patients

20. B. ASSISTED MODES
• Used, when patient is making some effort
• Breath may be triggered by patient / pre-set time
• Whichever comes first
• Rest of the breath completed by ventilator
• Two types of assisted modes
• Intermittent mandatory ventilation
• Synchronised Intermittent Mandatory Ventilation

21. • Intermittent mandatory ventilation(IMV)
• Gives partial ventilator support
• Gradually increases patient’s WOB
• Thereby strengthens respiratory muscles
• Concurrently IMV breaths delivered to prevent fatigue
• IMV breaths are delivered at set intervals
• IMV breaths gradually reduced to CPAP, if patient improves

22. • Disadvantages
• Breath stacking
• Ventilator & Patient breaths at same time
• Leads to high airway pressure
• Breathing against the ETT – Burden for injured lungs

23. • Synchronised Intermittent Mandatory Ventilation (SIMV)
• Allows mechanical breaths to be given on patient demand
• Breath stacking solved by inbuilt sensor, which
• Synchronises patient’s spontaneous breaths to set rate
• SIMV along with pressure or volume support is widely used
• SIMV+PS / SIMV+VS

24. C. SPONTANEOUS MODES (CPAP / PSV / VS)
Pressure Support Ventilation (PSV)
• Used for patients with reliable and stable respiratory drive
• To set PIP / PEEP / FiO2
• Setting VT / Ti / Rate is not required
• Patient initiates breaths, F/B ventilator completes
• Patient triggered / pressure limited / flow cycled
• VT can be changed depending on compliance / resistance
• If patient effort improves, pre-set PS may be reduced
• Hence monitor RR / VTe / Patient effort

25. PSV – FLOW CHART

26. • CPAP
• Elevation of baseline pressure during spontaneous breathing
• PEEP is elevation of baseline pressure during mech. Ventilation
• Open ups the collapsed alveoli

27. CPAP – FLOW CHART

28. HOW TO START A
VENTILATOR ?

29. BEFORE CONNECTING TO VENTILATOR
• System self check with circuit and test lung
• Calculates the compressible volume
• Thereby determines the VT
• Pressure controlled ventilators are preferred in weight < 8kg
• Ensure functioning humidifier / HME
• Set an average PIP ( 10 – 12 cmH2O)

30. • Optimal PIP will be determined by
• Adequate chest rise
• Good oxygenation
• Hemodynamic stability
• Blood gas
PROVISION OF ALVEOLAR VENTILATION
• Ventilator rate - According to age / Disease
• VC
• VT – 6-8 ml/kg
• Further adjusted acc. to chest rise / air entry / bld. gases

31. • PC
• PIP – 10 to 20 cmH2O / Above PEEP
• Should produce adequate chest rise
• VT will be generated from PIP – PEEP
• I:E ratio - 1:2
• In obstructive disease
• Keep prolonged expiratory time
• Reduced rate

32. MAINTANANCE OF ADEQUATE OXYGENATION
• FiO2
• In hypoxemic patients - Set initial FiO2 to 0.6 – 1.0
• Once improves reduce to non-toxic levels (< 0.5)
• PEEP
• 5 cmH2O or higher as needed
• Optimal PEEP
• Recruits collapsed alveoli / Maintains hemodynamics
• Heterogeneous lung disease = 7-10 cmH2O
• Diffuse lung disease = 10-15 cmH2O
• Target SaO2 90% with FiO2 0.5 – 0.6

33. SETTING APPROPRIATE ALARM SETTINGS
• Set alarm after final settings are made
• Too narrow range - Frequent alarms / Ignored by care givers
• Too wide range - Life threatening events will be missed
• High pressure alarm
• Set 8-10 cmH2O above the PIP
• Once alarm rings
• Inspiratory flow stopped / Gases vented out

34. • New onset high pressure alarm indicates
• Worsening of lung mechanics
• Increase in resistance / decrease in compliance
• ETT issues – secretions / patient biting the tube
• Low pressure alarms
• Set 5-10 cmH2O below PIP
• Common causes
• Tube leaks / ventilator disconnections

35. DISEASE BASED STRATEGY

36. SETTINGS IN NORMAL LUNG
CNS PATHOLOGY (POOR RESPIRATORY DRIVE)
• Ideal mode – SIMV – PC (Depends upon the patient’s effort)
• PIP: 10-12 cmH2O
• PEEP: 4-6 cmH2O
• FiO2: 0.2-0.3
• PS: 10-12 cmH20
• I:E Ratio – 1:2

37. PARENCHYMAL LUNG DISEASES
• ARDS / Pneumonia / Aspiration
• Heterogeneous pathology
• Atelectatic segment interspersed normal segments
• CV > FRC / VQ Mismatch / Intrapulmonary shunting
• Goals
• Lung protective strategy
• Reduce pressure / VT / Toxic oxygen levels

38. • Settings
• Low VT - 6 ml/kg to maintain plateau pressure <30 cmH20
• Optimal PEEP, which gives
• Saturation 86-90 % with FiO2 <0.6
• Optimal compliance with least over-inflation
• Least hemodynamic instability

39. • How to determine optimal PEEP ?
• Gradually increase the PEEP with fixed Delta P
• Monitor – Compliance (VTe) / O2 Saturation / Hemodynamics
• After maximum recruitment (opening alveoli)
• Oxygenation becomes static / Hemodynamics start worsens
• Optimal PEEP achieved – Maintain PEEP slightly above this point
• Same time risk of over inflation should be monitored
• Ideal PEEP 7-10 in heterogeneous lung disease
• 10-15 cmH2O in non pulmonary ARDS

40. AIRWAY DISEASES
UPPER AIRWAY OBSTRUCTION
• Epiglottitis / Croup / Post Extubation stridor / Burns
• Use ETT size less than for age
• Remove ETT when there is adequate peritubal leak
LOWER AIRWAY OBSTRUCTION
• Bronchiolitis
• CPAP is better option with PEEP 6-10 cmH2O
• If deteriorates after CPAP support
• Go for mechanical ventilation

41. • Bronchial asthma
• Goals
• Relieve respiratory muscle fatigue
• Reverse hypoxemia
• Avoid worsening hyperinflation
• Improve hemodynamic function
• Settings
• Use low tidal volumes (5-7 ml/kg)
• To reduce plateau pressure <30-35cmH2O
• PIP can be high
• Accept high PCO2 / if Ph >7.2

42. • PRVC mode is appropriate
• Set upper limit pressures / Reduced rate
• Long exhalation time to prevent air trapping
• Avoid reduction in inspiratory time < 0.5-0.6 sec
• Set PEEP of two third of auto PEEP ( not >7-8 cmH2O)
• Measured by expiration hold
• Deep sedation / avoid suctions / pharmacotherapy
• Early weaning and extubation is wise
• While recovering tube may activate wheeze

43. THANK YOU