1. Educational Resources
PICU resident handbook with relevant PICU topics is available at
Hard copy is available in the resident call room.

2. PICU chapters at http://peds.stanford.edu/Rotations/picu/picu.html
Monitors in ICU
Vascular Access
Codes
ICP management
Status Epilepticus
Sedation
Pediatric Airway
Airway Management
Mechanical Ventilation
ARDS
Status Asthmaticus
Inotropes
Shock
Sepsis
Meningococcus

3. PICU chapters at http://peds.stanford.edu/Rotations/picu/picu.html
Cardiomyopathy
Liver Failure
Acute Renal Falilure
Fluids, Electrolytes, Nutrition
Oncology
Transfusions
DKA
Submersion Injuries
Brain Death
End of life issues

4. PICU Tables at peds.stanford.edu
Sedation
Inotropes
Shock

5. MECHANICAL VENTILATION
SARASWATI KACHE, M.D.
Clinical Assistant Professor

6. Spontaneous respiration vs. Mechanical ventilation
Natural Breathing
Negative inspiratory force
Air pulled into lungs
Mechanical Ventilation
Positive inspiratory pressure
Air pushed into lungs

8. Initiate Mechanical Ventilation
Hypoxia
Hypercarbia
Airway protection
(Decrease demand in cases of poor cardiac output)

9. Ventilators: a Schematic

10. IMPORTANT TERMS TIME Volume Pressure Flow
I - Time: amount of time spent in inspiration
E - Time: amount of time spent in expiration
Volume
Amount of tidal volume that a patient receives
Pressure
Measure of impedance to gas flow rate
Flow
Measure of rate at which gas is delivered

11. A Few More Terms PEEP = positive end expiratory pressure
Pressure maintained in the airways at the end of exhalation
Keeps Alveoli from collapsing
PIP = peak inspiratory pressure
Point of maximal airway pressure
Delta P = the difference between PIP – PEEP
MAP = mean airway pressure

12. ICU Ventilator: Evita 4

13. ICU Ventilator: Evita 4

14. Types of Ventilation ….

15. Compliance = Volume
Pressure

16. Volume Ventilation Preset Ventilator Determines Advantages Volume PEEP
Rate
I-time
FiO2
Ventilator Determines
Pressure required
Advantages
Guaranteed minute ventilation
More comfortable for patient
Draw-backs
Large ETT leak
Not optimal for poorly compliant lungs

17. Pressure Ventilation Preset Vent determines Advantages Draw back PIP
PEEP
Rate
I-time
FiO2
Vent determines
Tidal volume given
Advantages
Provides more support at lower PIP for poorly compliant lungs
Draw back
Minute ventilation not guaranteed

18. Volume vs. Pressure

19. Amount of support to give…

20. MODES OF VENTILATION Controlled Mechanical Ventilation (CMV)
Assist Control (AC)
Continuous Positive Airway Pressure (CPAP)
Intermittent Mandatory Ventilation (IMV)
Synchronized Intermittent Mandatory Ventilation (SIMV)
Pressure Support
Volume Support
Pressure Regulated Volume Control (PRVC)

21. Assist Control Volume or Pressure control mode Parameters to set:
Rate
I – time
FiO2

22. Assist Control Machine breaths: Patient’s spontaneous breath:
Delivers the set volume or pressure
Patient’s spontaneous breath:
Ventilator delivers full set volume or pressure & I-time
Mode of ventilation provides the most support

23. SIMV Synchronized intermittent mandatory ventilation
Volume or Pressure mode
Parameters set:
Volume or pressure
Respiratory rate
I – time
FiO2
Pressure support

24. SIMV Synchronized intermittent mandatory ventilation
Machine breaths: d
Delivers the set volume or pressure
Patient’s spontaneous breath:
Set pressure support delivered
Mode of ventilation provides moderate amount of support
Works well as weaning mode

25. Pressure Support Parameters set: Machine breaths: none *****
FiO2
Machine breaths: none *****
Patient’s spontaneous breaths: set pressure support delivered
Purposes:
Final step prior to extubation
Re-train muscle strength

26. Continuous Positive Airway Pressure (CPAP)
Positive airway pressure maintained throughout respiratory cycle: during inspiratory and expiratory phases
Can be administered via ETT or nasal prongs

27. Managing the Patient…

28. Pulmonary Compliance Compliance = Volume Pressure
Monitor patient’s clinical changes
i.e. as compliance improves
Volume mode: required pressure decreases
Pressure mode: generated volume increases

29. Hypoxia
Hypoventilation: decreased alveolar ventilation, i.e. CNS depression
Diffusion impairment: abnormality at pulmonary capillary bed
Shunt: blood flow without gas exchange
Intra-pulmonary
Intra-cardiac
Ventilation-perfusion mismatch: Both dead space and shunt abnormalities

30. Treating Hypoxia Increase FiO2: >60% toxic to lung parenchyma
Increase mean airway pressure
PEEP : not too much, not too little
PIP
I-time

31. Hypercarbia Decreased minute ventilation Treatment: Respiratory rate
Tidal volume
Treatment:
Increase respiratory rate: assure I-time not too short as rate increased
Increase tidal volume
Allow permissive hypercarbia

32. Pulmonary Disease: Obstructive
Airway obstruction causing increase resistance to airflow: e.g. asthma
Optimize expiratory time by minimizing minute ventilation
Bag slowly after intubation
Don’t increase ventilator rate for increased CO2

33. Pulmonary Disease: Restrictive
Compromised lung volume:
Intrinsic lung disease
External compression of lung
Recruit alveolia, optimize V/Q matching
Lung protective strategies
High PEEP
Pressure limiting PIP: cmH2O
Low tidal volume: 4-8 ml/kg
FiO2 <60%
Permissive hypercarbia
Permissive hypoxia

34. High Frequency Oscillatory Ventilation

35. HIFI - Theory Resonant frequency phenomena:
Lungs have a natural resonant frequency
Outside force used to overcome airway resistance
Use of high velocity inspiratory gas flow: reduction of effective dead space
Increased bulk flow: secondary to active expiration

38. HIFI - Gas Transport Conventional bulk flow
Coaxial flow: different flow directions in central and peripheral air columns
Taylor dispersion: gas molecules disperse beyond the bulk flow front

39. HIFI - Gas Transport Molecular diffusion: gas mixing within alveoli
Pendelluft phenomenon: inter-alveolar gas mixing due to impedance differences

40. HIFI - Advantages Advantages: Disadvantages:
Decreased barotrauma / volutrauma: reduced swings in pressure and volume
Improve V/Q matching: secondary to different flow delivery characteristics
Disadvantages:
Greater potential of air trapping
Hemodynamic compromise
Physical airway damage: necrotizing tracheobronchitis
Difficult to suction
Often require paralysis

41. HIFI – Clinical Application
Adjustable Parameters
Mean Airway Pressure: usually set 2-4 higher than MAP on conventional ventilator
Amplitude: monitor chest rise
Hertz: number of cycles per second
FiO2
I-time: usually set at 33%

42. HIFI - Applications Oxygenation Mean airway pressure FiO2 Ventilation
Amplitude
Hertz
I-Time

43. Scenario #1
The following blood gas is presented to you for a 4yr patient that is now 3hours post-op from an OLT.
7.52 / 24 / 250 / 20 / -4
The ventilator settings are SIMV PC/PS PEEP – 4, Delta P-28, FiO2 – 50%, RR – 12.

44. Scenario #2
A 8yr female with ALL s/p chemo presents to the PICU with fever and neutropenia 1day prior. She is found with positive blood cultures this AM and got intubated secondary to respiratory failure. It is now 4am and the morning labs show the following ABG:
7.23 / 60 / 58 / 22 / -2
The ventilator settings are SIMV TV - 10cc/Kg, PEEP – 5, PIP – 38, PS – 14, FiO2 – 70%, RR – 20, I-time – 0.7
You go to examine the patient and she is agitated, hypertensive, and with a respiratory rate of 40.

45. Scenario #3
There is a 6 month old patient that presents with RSV bronchiolitis that progresses to severe disease and the patient is now on a HIFI ventilator. The patient’s ABG is as follows:
7.24 / 58 / 75 / 21 / -3
The ventilator settings are as follows: HIFI with MAP – 20, Amp – 28, Hz – 8, FiO2 – 40%.
As you are looking at the chest X-ray, the nurse mentions the patient looks more edematous this evening compared to last night.

46. References http://www.ccmtutorials.com/rs/mv/
Editors: Rogers MC & Nichols DG. Textbook of Pediatric Intensive Care. Baltimore, Willimams & Wilkins, 1996.
Cairo JM & Pilbeam SP. Mosby’s Respiratory Care Equipment. St. Louis, Mosby, 1999.
Evita 4 Intensive Care ventilator, Operating instructions, 2001.
West JB. Pulmonary Pathophysiology. Baltimore, Willims & Wilkins, 1992.