The document discusses the basics of neonatal ventilation. It explains that ventilation is used to provide oxygenation, remove carbon dioxide, and assist breathing in neonates. Key parameters discussed include peak inspiratory pressure, positive end expiratory pressure, compliance, resistance, tidal volume, and minute volume. Different modes of ventilation are also summarized, including their advantages and limitations. The importance of synchronization between the ventilator and patient's breathing is emphasized to reduce work of breathing and other complications.

1. BASICS OF
NEONATAL VENTILATION
Dr Abid Ali Rizvi

2. Why do we ventilate neonates?
 Oxygenation
 CO2 elimination
 Overwhelming Work of Breathing
 Poor respiratory drive
 Others: Transport of sick baby, pre-op etc.

3. Applied Mechanics
 Flow of gas Generates the inflating pressure.
 PIP minus PEEP Creates a pressure gradient [DP].
 Compliance [C] and
 Airway Resistance [Raw] Dictate the PIP and PEEP required.
 Tidal Volume [TV] Is proportional to the DP size.
 TV x Rate = Minute volume Quantifies the CO2 removal.
 Mean Airway Pressure [Paw] Quantifies the adequacy of
alveolar recruitment & oxygenation.
 Time Constant = [C] x [Raw] Decides optimum Ti and Te
 Dead Space [VD]
 Right to Left Shunting
 Work of Breathing [WOB]
 Endotracheal Leak

4. Start here:
 A pressure gradient between the airway opening
(mouth) and the alveoli must be present to drive the
flow of gases during both inspiration and
expiration.
 Peak Inspiratory Pressure [PIP]: Opens the alveoli.
 Positive End Expiratory Pressure [PEEP]: Prevents the
alveoli from collapsing during exhalation; thereby
maintains adequate Functional Residual Capacity
[FRC].

5. Components of the inflating pressure
Mean Airway Pressure =
area under the Pressure Time Curve
Pressure PIP
(cm of H2O)
PEEP

6. PIP wave form is shaped by the gas flow
rate during inspiration.

7. Compliance
 Compliance describes the elasticity or distensibility
of the respiratory structures (alveoli, chest wall, and
pulmonary parenchyma).
 A measure of the ease of expansion of the lungs and
thorax.
 Compliance = Δvolume  Δpressure
 Low Compliance means Stiff lungs [as in Hyaline
Membrane Disease]. It will need higher pressure
gradient for pushing air inside.

8. Elastance [E] :Recoil Tendency
 Elastance is reciprocal of compliance [C].
 It measures the ease with which a distended
structure return back to its original size.
 E=1/C
 Alveoli with low compliance are difficult to inflate,
but their elastance is high, so they deflate easily.
Such alveolar units are prone to atelectasis during
expiration.

9. Compliance

10. Airway resistance
 Airway resistance is the opposition to gas flow.
 Ratio of driving pressure to the rate of air flow.
 ET is the most important contributor of Raw
 Airway resistance depends on:
 Radii of the airways (total cross-sectional area)
 Lengths of the airways
 Flow Type: Laminar or Turbulent
 Density and viscosity of gas

11. Airway resistance

12. ET resistance increases with flow

13. Time Constant [Kt] = C x Raw
 One time constant of a respiratory system is
defined as the time required by the alveoli to
empty 63% of its tidal volume through the airways
into the mouth/ventilator circuit.
 At the end of three [Kt ] 95% of the tidal volume is
emptied.
 Airway diameter during inspiration: Raw .
Therefore inspiratory [Kt ] are ~ half of the
expiratory [Kt ].

14. % filling and emptying of alveoli after
every Time Constant.

15. Time Constant [Kt] = C x Raw
 Stiff alveoli (eg HMD) have very short [Kt ], so small Ti is
sufficient to fill them, and they will empty quickly also.
 Conditions with high Raw ( eg MAS, BPD) have long
expiratory time constant, so they will empty adequately
with longer Te, and will be slow to fill too.
 It is also dependent on the patient`s size. Every thing
being equal, larger infants have longer time constant
than the extremely premature ones.
 Therefore premature neonate will have normal
breathing faster than a term AGA newborn.

16. Anatomic Dead Space
 Anatomic dead space:
 The total volume of the conducting airways from the
nose or mouth down to the level of the terminal
bronchioles.
 This volume does not participate in the gas exchange.
 Extrathoracic : 2-2.5 ml/kg in neonates.
 Intrathoracic : 1.03 ml/kg, age independent.

17. Intrapulmonary RL shunting [ V/Q ]
 Alveolar Dead Space [Collapsed alveoli]

18. Instrumental dead space
In babies <1000 g, the extra
dead space may slightly
increase PaCO2 levels.
The advantages of using flow
sensors for monitoring, volume
targeting and flow triggering,
outweigh the small effect on
PaCO2.
Instrumental dead space
imposes a ventilatory burden
during SIMV weaning in small
preterm infants.

19. Work of Breathing
 Work = Pressure x Volume
 Work against Elastic Recoil
 Work against Resistance
 Airway resistance:
Mainly the narrow ET
 Tissue resistance
Viscous forces within tissues
Metabolic cost of WOB in spont.
as they slide over each other.
breathing in normal lungs is 1-2%
of total O2 consumption, but can
increase to >30% in ventilated
baby with premature lungs.

20. 2 Components of WOB:
Elastic and Resistive – Resp. Rate Dependency

21. Imposed work of breathing [WOB]
 ET, circuit tubing, ventilator exhalation valve, all
increase the resistance against which the baby must
breathe while on ventilator.
 This leads to increased O2 consumption and
exhaustion of respiratory muscles.

22. Techniques to counter the Imposed WOB:
 Avoid narrow ET if possible.
[Poiseuille's equation R   . L  (Radius)4]
 ‘Pressure Support’ for the spontaneous breaths.
 Adequate PEEP in expiration:
[Maximum WOB is for re-opening a collapsed alveoli]
 Optimize the lung volume:
 Lowlung volume: Airway resistance is high, so WOB .
 Over-distended Lungs: Compliance is low, so WOB .
 Synchronization of ventilator and baby`s cycling.
 Good nutrition.
 Early extubation ASAP.

23. Mean Airway Pressure [MAP/Paw]
Contributing parameters {PIP, PEEP, Ti, Flow, Rate}
Important for the: MAP= (PIP-PEEP) x [Ti (Ti+Te)] + PEEP
 Recruitment of alveolar units:
 Oxygenation is directly proportional to MAP.
 Surfactant preservation.
 Optimization of Lung volume:
 Airway resistance is high at low lung volumes.
 Compliance is poor at high (over-distended) lung volume.
 Pulmonary vascular resistance is high at low lung volume
 Venous return and Cardiac output is compromised when
MAP is abnormally high.

24. Mean Airway Pressure [MAP/Paw]
Safety & Efficiency of
ventilation is best in
this Lung Volume &
Paw range.
Lung Volume
Mean Airway Pressure

25. Importance of PEEP
 Presence of ET in the glottis disables the braking
action of the vocal cords during expiration, which
would normally prevent the collapse of alveoli.
 It is easy to expand an already open alveoli, rather
than opening a fully collapsed one.
 FRV provides a means of oxygenation of pulmonary
blood flow during expiration.
 PEEP split opens the floppy airways of preterm
neonate, thereby preventing their collapse during
expiration; so helps in reducing the airway
resistance in expiration.

26. Modes of Neonatal Ventilation -
Classified by three factors:
 Breath initiation:
 Controlledor
 Synchronized with the patient`s effort.
 Gas flow control during the breath delivery:
 Pressure limited or
 Volume limited
 Breath is termination:
 Time cycled (fixed inspiratory time) or
 Flow cycled (matching with the patient`s own Ti)
 Hybrid modes mix multiple techniques from above.

28. CMV & IMV: by definition…
 Continuous Mandatory Ventilation: Used most often
in the paralyzed or apneic patients. The ventilator
rate is set faster than the patient's own breathing
rate.
 Intermittent Mandatory Ventilation: The ventilator
rate is lower (less than 30 bpm), therefore the patient
gets chance to breathe spontaneously between two
controlled breaths.
 In both CMV and IMV, breaths are delivered regardless
of the patient's effort.
 Synchronization is not intended in both.

29. Poor Synchronization causes:
 Baby fighting with the ventilator.
 Increased WOB
 Abnormally high intra-thoracic and intra-pulmonary
pressure surges.
 Decreased venous return.
 Increased intracranial pressure.
 Barotrauma
 Sub-optimal training of muscles in weaning.

30. Synchronized ventilation modes
 Nomenclature is a mess.
 Heart of synchronized ventilation is the breath
sensor attached between the ventilator tubing & ET.
1. Pressure sensor
2. Flow sensor
1. Pneumotachograph
2. Hot wire anemometer
3. Hybrid

31. Limitations of flow sensors
 ET leak: expiratory TV may be underestimated.
 Less than the expected expiratory tidal volume due
to ET leak is registered as a negative flow ( same
as baby`s breath initiation).
This artifact falsely triggers a ventilator breath in
the middle of the baby`s expiration:
[AUTOCYCLING], ventilator can end up with very
high auto triggered rate.
 Imposing 1 mL of dead space, may increase the
work of breathing in very tiny preterm.

33. Assist Control [A/C]
Patient Triggered Ventilation [PTV]
 Every breath of baby that the flow sensor detects is
supported with PIP/PEEP
 Ventilator rate therefore belongs to baby.
 Ti is fixed by the physician.
 Backup rate [20-30/min] is set by physician in case
of apnea or flow sensor failure.
 Weaning is done by decreasing the PIP.
 If baby is excessively tachypneic, the A/C mode
may deliver abnormally high ventilator breaths,
causing hypocapnea.

34. A/C: Green parts at beginning of flow
curve is the patient`s effort

35. Synchronized Intermittent Mandatory Vent.
[SIMV]
 SIMV was developed as a result of the problem of
high respiratory rates associated with PTV.
 SIMV delivers the preset pressure and rate while
allowing the patient to breathe spontaneously in
between ventilator breaths.
 Each ventilator breath is delivered in synchrony with
the patient’s breaths, yet the patient is allowed to
completely control the spontaneous breaths.
 Work of breathing and respiratory muscle fatigue
increase with low parameter SIMV.

36. SIMV breaths:
Green spontaneous; Blue ventilator

37. Volume Targeted Ventilation [VTV]
Targeted Tidal Volume [TTV] Ventilation
Volume Guarantee [VG]
Physician selects a desired tidal volume (app. 5-6
mL/kg) for the baby.
The ventilator then delivers the desired tidal volume
at the lowest feasible PIP and Ti according to
changes in Raw, C and baby`s effort.
Main benefits of TTV:
Reduction in volutrauma and barotrauma.
A stable Tidal Volume avoiding swings in pCO2.
Ventilation is at the lowest possible parameters.
Ability to self wean.

38. Pressure Support Ventilation [PSV]
Peak Expiratory Flow

39. PSV with SIMV

40. Effect of various parameters on
oxygenation and ventilation.

41. In brief: Always Check:
 Chest movement, air entry, presence of retractions,
hyper-inflated chest, wheezing etc.
 Level of ET at lips, visible secretions in ET, any kinking
or disconnection, any warning alarms on the ventilator.
 Assess baby`s own respiratory drive: depth & rate.
 Signs of baby fighting the ventilator: air hunger,
asynchrony, gross difference between ventilator and
baby`s breathing rate.
 Signs of pain, agitation, abnormal posturing.
 Abnormal heart rate, BP, temperature.
 Signs of excessive sedation.