Mechanical Ventilation -Modes for Pediatrics

Mechanical Ventilation
Presenter:
Dr. Tirtha Raj Bhandari
2nd year Resident
Department of Pediatric Anesthesiology
KCH,Maharajguj
2/23/2019 Department of Anesthesiology, KCH 1

Objectives
• To discuss indication of mechanical ventilation
• To discuss different modes for mechanical ventilation

Indications
1) Can not oxygenate (low PaO2/SpO2)- Hypoxemic respiratory failure
2) Can not ventilate (high PCO2)- Hypercarbic Respiratory failure
3) Both
4) Can not protect airway/ secure airway( Low GCS)
5) When clinician/ physician confused, either patient need or not,
needs mechanical ventilation
6) Elective ventilation for GA

Goals/Principles of mechanical Ventilation
1) To provide adequate ventilation and oxygenation
2) To achieve adequate lung volume and recruitment
3) To improve lung compliance
4) To reduce work of breathing
5) To limit lung injury

Assessment for MV
We should know
1)History and physical examination
2) Laboratory and radiological finding of patient
3) Anatomical size and structure of airway and lungs
4) Disease severity

Classification
Both on inferior airway invasion
1) Non- invasive : No inferior airway invasion
2) Invasive: Invasion by endotracheal tube
Based on modes
1) Controlled Mechanical Ventilation: PCV, VCV, PRVC, HFV, CMV, IMV
2) Supported spontaneous breathing: PSV, VSV
3)Mixed Respiratory Support: SIMV/ or +PS
4) Assisted spontaneous breathing: CPAP, APRV

VCV
Volume is independent variable
Pressure varies with compliance of lung
Expiration is passive not affected by ventilator mode, rather affected
by compliance and resistance
Not a weaning mode
Peak airway Pressure= R*F+ Vt/compliance+ PEEP
Plateau Pressure= Vt/compliance+ PEEP

VCV
What do we set??
Vt and RR for Minute Ventilation For PaCO2 Management
PEEP and FiO2 For Pao2 Management
Flow/ I:E ratio- for both

PCV
Pressure is independent variable
Volume is dependent variable Depends on: level of pressure, I-time
also it is the function of compliance and airway resistance. That’s why
volume deliver can vary breath to breath.
Ventilator adjust flow to maintain pressure.
Flow decreases throughout the inspiratory cycle.
Good mode to use if patient has large air leak, the ventilator will
increase the flow to compensate it.
Not a weaning mode

PCV
What do we set??
Pressure limit, T-Insp, RR,FIO2,PEEP
P and RR for Minute ventilation PaCO2 management
FiO2 and PEEP for PaO2 management

VCV and PCV

A/C, V/C

PRVC= Pressure Regulated Volume Control
Actually a volume control assist control mode
Target minute ventilation is set
Ventilator will adjust the flow to deliver the volume without
exceeding a target inspiratory pressure
Very useful in patient with high airway pressure.

PRVC
Advantage:
1)No change in MV delivery even if pulmonary condition changes
2) The desired TV will be delivered at lowest PIP, thus minimizes risk of
barotrauma.
Disadvantage:
1)Hard to use on a spontaneously breathing patient or one with air leak
2)Not a weaning mode

Pressure Support=PS
Supports each spontaneous breath with supplemental flow to
achieve preset pressure
All breath are triggered by patient
Preset value  PIP, PEEP, FiO2
Patient determine Rate, Ti, I/E ratio, TV

PS
Needs intact respiratory drive
Helps to overcome airway resistance/ tube resistance, so that
spontaneous breathing will be easier
Can not be use in patient not having spontaneous breathing(i.e.
muscle relaxant)

SIMV= Synchronized intermittent mandatory
ventilation
Preset mechanical breath delivered within interval acc to preset and
wait for spontaneous in between, which it will use as a trigger to
deliver full breath.
If not sensed it will automatically give a breath
Vt on spontaneous breaths depends entirely upon the patient effort
and lung mechanics, can be pressure or volume controlled.

SIMV
Tb(time for breathing) = Tm(mandatory)+Ts(spontaneous)
If patient tries to breath during Tm, ventilator gives a fully assisted
breath
If Patient tries to breath during Ts, the ventilator will allow the
patient to take breath

SIMV+PS
SIMV+PS= provides assistance for spontaneous breath to overcome tube resistance

CPAP
Provides continuous positive pressure throughout the respiratory
cycle
So gives supports to inspiration and resistance to expiration
Can be use both in invasive and non-invasive form.
Very similar to PEEP

PEEP
PEEP is a residual pressure above atmospheric pressure maintained
at the end of expiration.
PEEP can be added to any mode
PEEP helps to recruit alveoli, increase FRC , Redistribute pulmonary
edema, Decrease intrapulmonary shunt, Increase PaO2.(GOOD)
PEEP , decreases venous return/CO, increase ICP/intensify cerebral
ischemia/ risk of barotrauma(Bad)

NASAL CPAP FOR NEONATE/INFANT
Nasal prong/Nasopharyngral tube/ET tube can be use for nasal cpap2/23/2019 Department of Anesthesiology, KCH 26

Indication
Disease condition;
1)Retained lung fluid
2)Post-extubation (if risk of airway collapse)
3)Atelectasis
4)Respiratory distress syndrome
5) For administration of controlled concentration of nitric oxide

CONTD
Physical findings:
1)Increase WOB ,indicated by increase RR by 30-40%
2)Sub-sternal/suprasternal retraction
3)Grunting and nasal flaring
4)Pale or cyanotic skin color
5)Agitation

Contraindication/ Should 'Not Try
C/I:
Choanal atresia
Untreated diaphragmatic hernia
Cleft palate
TEF
Should 'not try:
Cardiovascular instability
Severe ventilatory impairment
Severe hypoxemia
Frequent apnea
High level of sedation

How it Helps??
Reduces grunting and tachypnea
Increases FRC and PaO2
Decreases intrapulmonary shunting
Improves lung compliance
Aids in stabilization of floppy infant chest wall

CONTD
Improves distribution of ventilation
Reduce WOB
Reduces central and obstructive sleep apnea by mechanically
splinting the upper airway.
Better recruitment and oxygenation
Stimulation of infant/neonate for breathing

APRV= Airway Pressure Release Ventilation
It is a form of CPAP with release of pressure in between
It is a inverse ration ventilation
Uses lower PIP to maintain oxygenation and ventilation without
compromising venous return
Improves V/Q matching

APRV
Improves renal perfusion and urine output
Maintaining normal cyclic decrease in pleural pressure augmenting
venous return and improving CO
Need for sedation less
Chance of respiratory muscle atrophy and atelectasis less(as
spontaneous breath is present)
C/I Increase ICP, brocho-pleural fistula and Obstructive Lung Disease

APRV Settings
• P High= Inspiratory Pressure
• T high= time for inspiration
• P low/PEEP= expiratory pressure
• T low/PEEP= time spent in exp. Phase = allows
High mean airway pressure maintained

APRV

Initial setting for APRV
P high:
20-25 cm H2O- mean airway
pressure
30cmh2o if pplat is >=30cmh2o
Higher setting may be required
for morbid obesity and if thoracic
and abdominal compliance
decrease(ascites)
T high: minimum 2-3 seconds,
progressively increase to 10-15 sec
Helps in oxygenation
P low: Peep set at zero, provides
high Pressure difference for
unimpeded expiratory flow
T low/PEEP: 50-70% of peak
expiratory flow.
0.2 to 0.6 sec

NAVA= Neurally Adjusted Ventilatory Assistance
• It is a spontaneous or supported mode
• Patient initiated synchronized breathing mode
• Breathing support is triggered by the electrical activity of the
diaphragm(EADi)
• NAVA setting(1-4 cm H2o/uv) multiplies measures EADi to provide
pressure, which is proportional and synchronized to patient effort
• It avoids over/under assistance
• Lung protective mode in spontaneous breath
• Avoids asynchrony, so less sedation required and better sleep.

Any Questions???

Summary
We should know
When to start mechanical ventilation
Which mode would be better for particular patient
Setting should be appropriate according to patient to minimize injury
to lung
Steps of changing modes for weaning

References
• Clinical Application of Mechanical Ventilation(Chang)
• Miller Anesthesia- 8th edition
• Barash anesthesia- 8th edition

Mechanical Ventilation -Modes for Pediatrics

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