This document provides an overview of neonatal ventilation fundamentals, including respiratory physiology, ventilator basics, and pulmonary graphics. Some key points: - Neonates have higher respiratory rates and are more prone to respiratory failure due to anatomical differences in their chest walls and lungs. - Ventilation eliminates carbon dioxide from the blood and is correlated with minute ventilation and alveolar ventilation. Lung volumes, mechanics, and gas exchange are also discussed. - Common ventilator terminologies like PIP, PEEP, rate, and modes of ventilation like pressure and volume control are introduced. - Pulmonary graphics provide pressure, volume, and flow signals over the respiratory cycle to assess ventilation.

1. VENTILATION
FUNDAMENTALS
Dr Bikash Shrestha
Fellow Neonatology (NNF, India)
MD Paediatrics (AFMC, Pune, India)

2. OVERVIEW
 REPSIRATORY PHYSIOLOGY
 VENTILATOR BASICS

3. RESPIRATORY PHYSIOLOGY
 Basic characteristics
 Oxygenation
 Ventilation
 Lung volumes
 Lung mechanics

4. BASIC CHARACTERISTICS-1
 Higher respiratory rate

5. BASIC CHARACTERISTICS-2
 Higher propensity to respiratory failure
– More cylindrical thorax of newborns
– Horizontal placing of ribs
– Compliant chest wall-lower propensity to
spring out
– Closing volume almost equal to FRC

6. BASIC CHARACTERISTICS-3
 Higher propensity to respiratory failure
– Diaphragmatic attachment more horizontal
– Low muscle mass and less type I muscle fibers
– Liver is relatively larger organ
– Dramatic increase in airway resistance (Narrow
airway)
– Lung growth takes place in centripetal direction
with relatively larger anatomic dead space

7. OXYGENATION-1
 Extraction of oxygen from the atmosphere
and delivery into the mitochondria
 Directly correlated with the partial pressure
of oxygen in the alveoli (PAO2)
 Partial pressure of oxygen in artery (PaO2)
 Alveolar arterial oxygen gradient (PAO2 –
PaO2) = 5 - 15 mm Hg

8. ALEVOLAR GAS EQUATION

9. HYPOXEMIA-1
 Hypoxic gas mixture (Low FIO2)
 High altitude (Low PB)
 Hypoventilation (High PACO2)

10. HYPOXEMIA-2
 Increased alveolar arterial oxygen
gradient (PAO2 – PaO2)
 Ventilation perfusion mismatch (shunts)

11. HYPOXEMIA-3
Ventilation perfusion mismatch (shunts)

12. VENTILATION-1
 Elimination of CO2 from the blood through the
alveolus
 PaCO2 is proportional to minute ventilation
(VE)
 PaCO2 is accurately correlated to mean
alveolar minute ventilation

13. VENTILATION-2
Problem in ventilation (PaCO2)
–Reduced RR
–Reduced tidal volume
–Increased dead space

14. LUNG VOLUMES

15. LUNG MECHANICS
 Elastic recoil
 Compliance
 Resistance
 Time constant

16. ELASTIC RECOIL-1
The tendency of stretched objects
to return to their original state

17. ELASTIC RECOIL-2
 The forces tending
and resisting to
collapse are equal
at a point close to
FRC or resting state

18. ELASTIC RECOIL-3
 Surface tension is correlated with elastic
recoil
 Surface tension follows Laplace law
P = 2T
R

19. ELASTIC RECOIL-4

20. ELASTIC RECOIL-5

21. COMPLIANCE-1
Change in volume resulting from a
given change in pressure

22. COMPLIANCE-2

23. RESISTANCE
 Resistance is resulted due to friction
 Viscous resistance and airway resistance
 VR-Generated by tissue elements moving
past one another
 AR-Generated within the respiratory tract
against the gas flow
R = P1-P2
V(Flow)

24. TIME CONSTANT-1
 Time necessary for the alveoli to discharge
63% of TV

25. TIME CONSTANT-2
 Pressure changes at alveoli lag behind at the
proximal airway
 Inspiratory and expiratory time constants

26. TIME CONSTANT-3

27. TIME CONSTANT-4
 3 time constants lead to 95% equilibrium
of alveolar and proximal airway
 R (Resistance) X C (Compliance)=0.15 secs
 3 time constants = 0.45 secs

28. VENTILATOR
BREAKTHROUGHS

29. KENNEDY TRAGEDY
 1963-Patrick Bouvier Kennedy (34 wks POG/2.1 kg)
 RDS-succumbed at 39 hrs

30. VENTILATOR
BASICS

31. VENTILATOR BASICS
 Introduction
 Basic terminologies
 Oxygenation-MAP
 Modes of ventilation
 Pulmonary graphics

32. INTRODUCTION
 Movement of gas into and out of lungs by
an external source connected directly to
the patient
 Supportive, non therapeutic technology
 Most neonatal ventilators based on
Ayer’s T-piece

33. AYER’S T-PIECE

34. BASIC PARTS
 Pressurized source
 Blending chamber
 Flow control
 Exhalation valve

35. BASIC TERMINOLOGIES
 PIP – Peak inspiratory pressure
 PEEP – Positive end expiratory pressure
 Rate - Frequency
 Ti – Time allowed for inspiration
 Te – Time allowed for expiration
 IE ratio – 1:1 to 1:3

36. MEAN AIRWAY PRESSURE-1
 Average airway pressure over a given interval of
time (PAW)
 Area under the curve of pressure time curve for
one breath divided by total cycle time

37. MEAN AIRWAY PRESSURE-2

38. MODES OF VENTILATION-1
 Three factors
– How each breath is initiated
– How gas flow is controlled during delivery
– How the breath is terminated

39. MODES OF VENTILATION-2
 Breath initiation
– Controlled
– Synchronized or patient triggered
 Gas flow control
– Pressure
– Volume
 Flow termination (Cycling)
– Volume cycling -Time cycling
– Pressure cycling -Flow cycling

40. MODES OF VENTILATION-3

41. PULMONARY GRAPHICS-1
 Introduction
– Relatively new (1980’s)
– Microprocessor development (1990’s)
 Basis
– Sensor with tungsten wire at the proximal airway
– Heated wire anemometer technology
– Gas flow results in cooling of the wire
– Electricity required to bring it back to original temperature is
converted to signals

42. PULMONARY GRAPHICS-2
 Colors
– Inspiration (Red-machine) (Yellow-patient)
– Expiration (Blue)
– Auto calibrating (Green)
 Common signals
– Pressure (cm of H2O)
– Volume (mL)
– Flow (mL/sec)

43. PULMONARY GRAPHICS-3

44. PULMONARY GRAPHICS-4
 Cyclic phases
– A -Initiation of inspiration
– B -Peak inspiration
– C -End inspiration
– D -End expiration

45. “Primum non nocere”
(First do no harm)
The first tenet of Hippocratic oath

46. REFERENCES
 M Keszler. Update on mechanical ventilator strategies. Neoreviews.
2013;14:e237.
 AK Ghuman, RG Khemani, CJL Newth. Pediatric applied respiratory
physiology-the essentials. Pediatrics and Child Health. 2013;23:7.
 PD Sly, RA Collins. Physiological basis of rspiratory signs and
symptoms. Pediatric Respiratory Reviews. 2006;7:84-88.
 PC Rimensberger. Pediatric and Neonatal Mechanical Ventilation-
From Basics to Clinical Practice. Berlin. Springer-Verlag. 2015.
 JP Goldmsith, EH Karotkin. Assisted Ventilation of the Neonate. 5th ed.
USA. Saunders-Elsevier Imprint. 2015.
 SM Donn, MC Mammel. Neonatal Pulmonary Graphics-A Pocket
Atlas. New York. Sprigner. 2015.

47. DESIRABLE CME’S
 Basics of neonatal ventilation
 Pulmonary waveforms fundamentals
 Non invasive neonatal ventilation
 Newer modes of ventilation
 CPAP-Essential tool in NICU’s

48. THANK YOU