basics for mechanical ventilator

1. Neonatal Ventilator Workshop

2. Terminology
Respiration
Ventilation
Oxygenation
ALL SAME ?ALL SAME ?

3. Lung Function
Prime function
exchange of O2 and CO2
Other functions,
a. blood reservoir
b. heat exchange
c. metabolism - synthesis & catabolism
d. immunological and mechanical defence

4. BASICS

5. AIRWAYS
Main Airway Branches & Zones
Conducting zone
( generations 1-16 )
Trachea
R+L main bronchi
Lobar bronchi
Segmental bronchi
Bronchioles
Terminal bronchioles
Respiratory zone
( generations 17-23)
Respiratory bronchioles
Alveolar ducts
Atria
Alveolar sacs

6. Conducting zone

7. Respiratory zone

8. Dead space
Anatomical dead space
CZ doesn't contribute to gas exchange -
Physiological dead space
It is the combination of anatomical
dead space and alveolar dead space.

9. Cell Types in the
Respiratory Tract
1. Alveolar type I cells – Ventilation
2. Alveolar type II cells - produce surfactant
3. Alveolar type III cells ? function = "brush"
cells
4. Capillary endothelium
5. Alveolar macrophages
6. Mast Cells
7. Non-ciliated bronchial epithelial, "Clara",
cells
8. APUD cells

10. Surfactant
 Reduce surface tension

11. Perfusion
How many capillaries for each alveoli ??
For gas exchange – alveoli must contact
with ample blood supply
1 million alveoli : 280 billion capillaries

12. Ventilation
 Inspiration
 Expiration

13. Diaghram contracts
↑Chest volume
↓Pleural pressure
Air moves down
pressure gradient
to fill lungs
-2cm H20
-7cm H20
Alveolar
pressure falls
Lung @ FRC= balance
Normal inspiration

14. Diaghram relaxes
Pleural /
Chest volume ↓
Pleural pressure
rises
Alveolar
pressure rises
Air moves down
pressure gradient
out of lungs
-7cm H20
-2cm H20
Normal expiration

15. Air blown in
↑ lung pressure
Air moves down
pressure gradient
to fill lungs
↑ Pleural
pressure
0 cm H20
+5 to+10 cm H20
Ventilator inspiration

16. Ventilator expiration
Ventilator stops
blowing air in
Pressure gradient
Alveolus-trachea
Air moves out
Down gradient
↓ Lung volume

17. Regulation for respiration

18. LUNG VOLUMES
primary lung volumes
i. RV Residual Volume
ii. ERV Expiratory Reserve Volume
iii. TV Tidal Volume
iv. IRV Inspiratory Reserve Volume

19. secondary derived capacities
i. TLC Total Lung Capacity
ii. VC Vital Capacity
iii. IC Inspiratory Capacity
iv. FRC Functional Residual Capacity

20. TLC
IRV
RV
FRC
TV
ERV
VC

21. Tidal volume
Dead space
Alveolar ventilation
minus
=

22. Alveolar ventilation
Volume of fresh gas entering the alveoli
per breath
VA = VT - VD

23. Minute volume
= VT × respiratory rate

24. Alveolar minute ventilation
Alveolar ventilation x respiratory rate

25. Gas exchange and transport

27. Carbon Dioxide (CO2)
Elimination
Depends on alveolar minute ventilation

29. Oxygenation

30. COMPLIANCE
Compliance describes the elasticity or
distensibility
compliance = volume / pressure

31. Normal ventilating lungs
Normal Compliance

32. Low Compliance
RDS

33. Left pneumothorax
High compliance

34. Pressure Volume curve

35. RESISTANCE
 inherent capacity to oppose airflow and
 expressed as the change in pressure
per unit change in flow:
Resistance = pressure/ flow

36. Airway resistance depends on
1) radii of the airways (total cross-
sectional area),
2) length of airways,
3) flow rate,
4) density and viscosity of gas breathed.

37. Time constant

38. Time constant
 time necessary for the alveolar
pressure to reach 63% of the change in
airway pressure
Time constant = resistance x compliance

39. Ventilator terminology

40. This is not the end,
It’s just the beginning….

41. THANK YOU