1. Educational Resources
PICU resident handbook with relevant
PICU topics is available at
http://peds.stanford.edu/Rotations/picu/pic
u.html
Hard copy is available in the resident call
room.
6. Spontaneous respiration vs.
Mechanical ventilation
Natural Breathing
Negative inspiratory force
Air pulled into lungs
Mechanical Ventilation
Positive inspiratory pressure
Air pushed into lungs
10. IMPORTANT TERMS
TIME
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
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:
Volume or pressure
Rate
I – time
FiO2
22. Assist Control
Machine breaths:
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:
Pressure support,
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
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
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
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
36.
37.
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:
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%
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.
