‫بسم هللا الرحمن الرحیم‬
Basics of Mechanical Ventilation
Normal breath
Normal breath inspiration animation, awake
Lung @ FRC= balance
-2cm H20
Diaghram contracts
Chest volume
Pleural pressure
-7cm H20
Air moves down
pressure gradient
to fill lungs
Alveolar
pressure falls
Normal breath
Normal breath expiration animation, awake
Diaghram relaxes
Pleural /
Chest volume 
Pleural pressure
rises
Alveolar
pressure rises
Air moves down
pressure gradient
out of lungs
‫منحنی تغییرات ‪:‬‬
‫‪ )1‬فشار – زمان‬
‫‪ )2‬حجم – زمان‬
‫‪ )3‬جریان – زمان‬
‫را در یک سیکل تنفسی طبیعی رسم کنید‪:‬‬
Pressure
Normal breath
Expiration
+3
+2
+1
0
-1
-2
-5
Inspiration
Pressure
Normal breath
Expiration
+3
+2
+1
0
-1
-2
-5
volume
Inspiration
Time
Normal breath
FLOW
Expiration
Inspiration
Pressure
Expiration
+3
+2
+1
0
-1
-2
-5
FLOW
volume
Inspiration
Inspiration
Expiration
Normal breath
Ventilator breath inspiration animation
0 cm H20
 lung pressure
Air blown in
Air moves down
pressure gradient
to fill lungs
+5 to+10 cm H20
 Pleural
pressure
Ventilator breath expiration animation
Similar to spontaneous…ie passive
Ventilator stops
blowing air in
Air moves out
Down gradient
Pressure gradient
Alveolus-trachea
 Lung volume
‫منحنی تغییرات‬
‫‪ )1‬فشار‬
‫‪ )2‬حجم‬
‫‪ )3‬جریان‬
‫را در یک سیکل تنفس مصنوعی رسم کنید‪:‬‬
0
1
2
5
FLOW
volume
Pressure
+
3
+
2
+
1
Normal breath
Mechanical breath
Origins of mechanical ventilation
•Negative-pressure ventilators
(“iron lungs”)
• Non-invasive ventilation first
used in Boston Children’s Hospital
in 1928
• Used extensively during polio
outbreaks in 1940s – 1950s
•Positive-pressure ventilators
The iron lung created negative pressure in abdomen
as well as the chest, decreasing cardiac output.
• Invasive ventilation first used at
Massachusetts General Hospital
in 1955
• Now the modern standard of
mechanical ventilation
Iron lung polio ward at Rancho Los Amigos Hospital
in 1953.
Several ways to ..connect the
machine to Pt
• Oro / Naso - tracheal Intubation
• Tracheostomy
• Non-Invasive
Ventilation
Ventilation = Inspiration + Expiration
Inspiration = 1) Start or Triggering
2) inspiratory motive force or control or Mode
3) termination of inspiration or Cycling
Expiratory Phase Maneuvers
Classification (the Basic
Questions)
A. Trigger mechanism
– What causes the breath
to begin?
B
B. Limit variable
– What regulates gas
flow during the breath?
C. Cycle mechanism
– What causes the breath
to end?
A
C
1
2
3
The four phases of each ventilatory cycle
4
volume
Inspiration
Time
Expiration
volume
Cycling
Start
Time
Cycling Vs. Limiting
Pressure
Pressure
Limited
Time
Cycled
Time
‫چهار مرحله تنفس مکانیکی را نام ببرید‪:‬‬
‫‪)1‬‬
‫‪)2‬‬
‫‪)3‬‬
‫‪)4‬‬
Triggering the Ventilator
 flow trigger
 pressure trigger
 volume Trigger
 Time Trigger
 Other techniques: Neurally Adjusted Ventilatory Assist (NAVA)
Chest impedance
Abdominal movement
Flow triggering is considered to be more comfortable,
Increasing the trigger sensitivity:
decreases the work of breathing
accidental triggering and unwanted breaths
Trigger
Which Trigger is correct?
flow trigger
pressure trigger
volume Trigger
Time Trigger
Mandatory
all the breaths with
mandatory
inspiratory cycling
Spontaneous
Unsupported
Mandatory
Trigger
Which Trigger is correct?
flow trigger
pressure trigger
volume Trigger
Time Trigger
Trigger
Which Trigger is correct?
flow trigger
pressure trigger
supported
volume Trigger
Time Trigger
Mandatory
Trigger
Which Trigger is correct?
flow trigger
pressure trigger
supported
volume Trigger
Time Trigger
Mandatory
Synchronized
Triggered
(PSV)
spontaneous
spontaneous
and mandatory
inspiratory
and
cycling
mandatory
Mandatory
(VCV)
No mandatory inspiratory cycling
all the breaths are pressuretargeted and trigger inspiratorycycled
Which Trigger?
flow trigger
pressure trigger
volume Trigger
Time Trigger
Non of the above
Expiration
Inspiration
Air OUT
Air IN
Time Constant = C X R
A certain amount of time is necessary for pressure equilibration (and therefore completion of delivery of
gas) to occur between proximal airway and alveoli. TC, a reflection of time required for pressure
equilibratlon, is a product of compliance and resistance. In diseases of decreased lung compliance, less
time is needed for pressure equilibration to occur, whereas in diseases of increased airway reslstance,
more time is required. Expiratory TC is increased much more than inspiratory TC in obstructive airway
diseases, because airway narrowing is exaggerated during expiration.
3-5 time constant
C = 100 cc/ Cm H2O
R = 1 Cm H2O / L / Sec
Time Constant = ?
= R.C
=100 cc/ Cm H2O X 1 Cm H2O / L / Sec
= 0.1 Sec
C = 50 cc/ Cm H2O
R = 1 Cm H2O / L / Sec
TC= ?
= R.C
=50 CC / Cm H2O X 1 Cm H2O / L / Sec
= 0.05 Sec
C = 100 cc/ Cm H2O
R = 2 Cm H2O / L / Sec
Time Constant = ?
= R.C
=100 CC/ Cm H2O X 1 Cm H2O / L / Sec
= 0.2 Sec
Time Constant
C = 40 cc/ Cm H2O
R = 4 Cm H2O / L / Sec
Inspiratory Time = ??
TC = C x R = 0.16
IT = 3 x 0.16 = 0.48
Selection of Appropriate Inspiratory Time
TI too long
TI too short
T I = 3-5 time constant
Tc = C x R
TI is usually initiated at: 0.5-0.7 sec for neonates,
0.8-1 sec in older children,
1-1.2 sec for adolescents and adults
need to be adjusted through : individual patient observations
and according to the type of lung disease.
T I + T E = Time Cycle
F ( RR ) = 60/TC
IT
ET
F= 60/ TI +TE
T I = 3-5 time constant
Tc = C x R
Many ventilators ask the user to set the I:E ratio and respiratory rate
V T = 100 cc
TI = 0.8 sec
Inspiratory Flow = ?
Inspiratory Flow = 100 / 0.8 = 125 cc/sec (7.5 L/ Min )
• RR = 60 I:E = ½
IT = ? ET = ?
F= 60/ TI +TE
60 = 60 / TI + 2TI = 60/ 3TI
IT = 0.33
ET = 0.66
• IT= 0.8 ET= 1.2Sec
• RR=?
F= 60/ TI +TE
RR = 60 / 0.8+1.2 = 30
Inspiratory Flow/Pressure/Volume Pattern
Decelerating
Square
Accelerating
Sinusoidal
Inspiratory Rise Time
time
Pmax = Pinf + PEE
Pressure-controlled inflation
Inspiratory Rise Time
Effect of a pressure-limit on a volume-controlled breath
Cycling
Termination of Inspiration (Cycle)
1)Time-cycled
2)Volume-cycled
3) flow-cycled
Pressure Controlled Ventilation
Cycling at 25% Flow
VT
Pressure Controlled Ventilation
respiratory resistance and
compliance are both lower
both the resistance and compliance of
the respiratory system are higher
Cycling at 25% Flow
IT>
IT<
10%
ET
ET
50%
Over inflation
(high resistance),
prolonged inspiration
a large tidal volume.
the next inspiratory phase starts before expiratory gas flow has reached zero
Improve
Over inflation
inspiratory motive force or control or Mode
Critical Opening Pressure
Volume Controlled Ventilator
The desired tidal volume is set on the ventilator, and the resulting airway
pressure excursion is merely observed.
Inspiratory volume is thus the primary, or independent, variable (V) and the
change in airway pressure (P) resulting from this is the secondary, or
dependent, variable.
The value of P is determined by the compliance of the respiratory system,
which is given by V/P.
If the compliance of the respiratory system falls, V remains constant but P
increases
Pressure Controlled Ventilator
The desired inflating pressure is set on the ventilator, and the tidal volume that this delivers
is merely observed.
The change in airway pressure is thus the primary, or independent, variable (P) and the
volume change (V) resulting from this is the secondary, or dependent, variable.
The value of V is determined by the compliance of the respiratory system, which is given
by (V/P).
If the compliance of the respiratory system falls, P remains constant but V falls
volume-controlled inspiration
A: Volume/time curve for a volume-controlled inspiration with
a tidal volume of VT1 litres and an inspiratory time of TIa
seconds. The inspiratory flow ( ˙VI ) is the slope of the volume/time :
˙VI = VT 1 / TI a
volume-controlled inspiration
‫تغییر در حجم جاری‬
High Flow
High VT
Low VT
I time
instant
Low Flow
‫منحنی تغییرات فشار را در حجم های مختلف رسم کنید‪:‬‬
‫‪ )1‬افزایش حجم جاری‬
‫‪ )2‬کاهش حجم جاری‬
‫‪PRESSURE‬‬
‫‪Time‬‬
‫تغییر در زمان دم‬
VT
Constant
I time
variable
Low Flow
‫منحنی تغییرات فشار را در زمانهای مختلف دم رسم کنید‪:‬‬
‫‪ )1‬افزایش زمان دم‬
‫‪ )2‬کاهش زمان دم‬
‫‪PRESSURE‬‬
‫‪Time‬‬
Inspiration sometimes have two phases,
1) an active ‘flow’ (TI f low) phase during which gas is being delivered to the patient,
2) end-inspiratory pause (TI pause )
TI = TI f low + TI pause
end-inspiratory
pause
Changes in
End-inspiratory
Pause
Pressure profile of a volume-controlled breath with an end-inspiratory pause
‫منحنی تغییرات فشار را در وقفه های مختلف دم در‪ vcv‬رسم کنید‪:‬‬
‫‪ )1‬افزایش زمان وقفه دم‬
‫‪ )2‬کاهش زمان وقفه دم‬
‫‪PRESSURE‬‬
‫‪Time‬‬
‫منحنی تغییرات جریان را در وقفه های مختلف دم در ‪ vcv‬رسم کنید‪:‬‬
‫‪ )1‬افزایش زمان وقفه دم‬
‫‪ )2‬کاهش زمان وقفه دم‬
‫‪FLOW‬‬
‫‪FLOW‬‬
‫منحنی تغییرات حجم را در وقفه های مختلف دم در ‪ vcv‬رسم کنید‪:‬‬
‫‪ )1‬افزایش زمان وقفه دم‬
‫‪ )2‬کاهش زمان وقفه دم‬
‫‪volume‬‬
‫‪volume‬‬
Volume-controlled inflation
. A good indicator of adequate tidal volume is:
. . . . . a. good chest rise
. . . . . b. adequate breath sounds
. . . . . c. oxygen saturation = 100%
. . . . . d. a and b
►
As compliance worsens in a child receiving volume controlled
mechanical ventilation, the TV delivered to the patient will:
. . . . . a. increase
. . . . . b. decrease
. . . . . c . No change
►
As resistance increases in a child receiving volume controlled
mechanical ventilation, the TV delivered to the patient will:
. . . . . a. increase
. . . . . b. decrease
. . . . . c . No change
►
As resistance decreases in a child receiving volume controlled
mechanical ventilation, the TV delivered to the patient will:
. . . . . a. increase
. . . . . b. decrease
. . . . . c . No change
►
As compliance worsens in a child receiving volume controlled
mechanical ventilation, the Pressure delivered to the patient will:
. . . . . a. increase
. . . . . b. decrease
. . . . . c . No change
►
As resistance decreases in a child receiving volume controlled
mechanical ventilation, the Pressure delivered to the patient will:
. . . . . a. increase
. . . . . b. decrease
. . . . . c . No change
►
As resistance increases in a child receiving volume controlled
mechanical ventilation, the Pressure delivered to the patient will:
. . . . . a. increase
. . . . . b. decrease
. . . . . c . No change
►
Comparison of ‘volume-controlled’
and ‘pressure-controlled’ breaths
Volume
Tidal volume
Airway
pressure
Minute Volume
Inspiratory
Flow
Pressure
Comparison of ‘volume-controlled’
and ‘pressure-controlled’ breaths
VCV
PCV
Tidal volume
---------
----------
Airway
pressure
---------
-----------
Minute Volume
----------
----------
Inspiratory
Flow
-----------
----------
Comparison of ‘volume-controlled’
and ‘pressure-controlled’ breaths
VCV
PCV
Tidal volume
Fixed
Variable
Airway pressure
Variable
Fixed
Minute Volume
Set
Measured
Inspiratory Flow
Constant/Square
Decelerating
IPPV
Trigger
Time
Patient
Patient
PSV
CPAP
Inspiratory cycling
Inspiratory support
Time
Yes
Patient
Yes
Patient
No
Breath type Example
Mandatory
Triggered
Spontaneous
IPPV
Pressure
support
CPAP
CONVENTIONAL VENTILATOR SETTINGS
FI02
Is the patient adequately oxygenated?
2 Question
1: ‘how well are this patient’s lungs able to take up the oxygen I am
supplying?’
2: ‘is enough oxygen being supplied to the patient’s vital organs?’
The clinical assessment of the adequacy of oxygenation is deceptively difficult
Measurement of
PaO2 or
(SaO2), or
both
The PaO2 and SaO2 are not equivalent and provide different information
PaO2/ FiO2
A-a Gradient
CaO2 = ( Hb × 1.34 × SaO2/100 ) + (0.0225 × PaO2 )
A-a Gradient = PAO2 − PaO2
PAO2 = FIO2 × (Pb − 47) − PaCO2/0.8
PAO2=F IO2 × (Pb + { PEEP/75} − 47) − PaCO2/0.8
oxygenation index OI = 100 × FIO2 × Paw/ PaO2
PAO2/ PaO2 more indicative of V/ Q mismatch and alveolar capillary integrity.
VI = (PIP x ventilator rate/min x Paco2) / 1000
==================================================================
extra-pulmonary
CaO2 = ( Hb × 1.34 × SaO2/100 ) + (0.0225 × PaO2 )
oxygen delivery D ˙ O2 = ˙Qt × CaO2/ 100
oxygen consumption
FiO2
Pa O2
SaO2 = 95
Pa02 value of 70-75 torr is a reasonable goal
Fi O2 values should be decreased to a level ~0.4 as long as SaO2 remains 95% or above
Rate of diffusion = Area × K × PAO2− PaO2 / d
IT / Plateau
RR by ET
CPAP
Positive end-expiratory pressure (PEEP)
What is PEEP?
Positive pressure measured at the end of expiration.
)
PHYSIOLOGICAL
PEEP
PEEP (3 to 5 cm H2O)
to overcome the decrease in FRC that results from the bypassing of the glottic
apparatus by the ETT
Positive End-expiratory Pressure
(PEEP)
What is the goal of PEEP?
•
•
•
•
•
•
•
•
PEEP FOR HYPOXAEMIA
‘to open the lungs and keep them open’
To improve respiratory mechanics,
To reduce intrapulmonary shunt,
To stabilize unstable lung units
To reduce the risks of ventilator-induced lung injury (VILI
Recruit lung in ARDS
Prevent collapse of alveoli
Diminish the work of breathing
Critical Opening Pressure
Collapse/ atelectosis/ ARDS
Increases Surface area for gas exchange
Opens the collapsed lung
PEEP
Collapsed
alveoli
After PEEP
PEEP- Indications.
• If a PaO2 of 60 mmHg cannot be achieved
with a FiO2 of 60%
• If the initial shunt estimation is greater than
25%
• Pulmonary edema
• ARDS/ALI
• Atelectosis
Complications of positive end-expiratory pressure (PEEP)
Pulmonary over-distension
Barotrauma
Ventilator-induced lung injury (VILI)
Increased dead space
Impaired carbon dioxide elimination
Reduced diaphragmatic force-generating capacity
Reduced cardiac output and oxygen delivery
Impaired renal perfusion
Reduced splanchnic blood flow
Hepatic congestion
Reduced lymphatic drainage
Diminish cardiac output
Regional hypoperfusion
Augmentation of I.C.P.?
Paradoxal hypoxemia
Hypercapnoea and respiratory acidosis
Prolongation of inspiratory time
INVERSE RATIO VENTILATION
first described in the early 1970s in infants with ARDS
the inspiratory period extends beyond 50% of the total cycle time
IRV can be applied in either volume- (VC) or pressure-controlled (PC) mod.
To maintaining an open lung in ALI/ARDS
requires profound sedation and frequently the use of neuromuscular blockade.
adverse consequences to cardiac output; any perceived benefits to oxygenation may
well be offset by consequent reductions in oxygen delivery.
AIRWAY PRESSURE RELEASE VENTILATION (APRV)
first described in 1987.
is a form of bi-level assisted ventilation
utilizing continuous positive airway pressure (CPAP) with periodic pressure releases,
either to a lower CPAP pressure or
to atmospheric pressure
The ventilator settings for APRV do not usually include the respiratory frequency but
instead :
the duration of Phigh, Thigh in seconds;
the duration of Plow, Tlow in seconds;
absolute value of Phigh and Plow.
the patient is able to breathe spontaneously during both of these phases.
Bi-level ventilation
Bi-level ventilation.
the airway pressure cycles between two levels of CPAP.
The patient can breath spontaneously during both Phigh and Plow phases, and only
receives inspiratory assistance during the low–high transition.
High-frequency oscillatory ventilation.
(HFOV) A system of ventilation which uses respiratory rates between 300 and 900 breaths
per minute
Alveoli
Segmental bronchi
Carina
ET tube
Oscillator
Recruitment maneuvers
PRONE POSITION
Ventilation
at rest 200 mL.min−1
1) volume of dead space,
2) tidal volume,
3) respiratory frequency
4) Positive end-expiratory pressure (PEEP
Influences on the production of carbon dioxide
• Factors associated with increased carbon dioxide production
– Systemic inflammation
– Sepsis
– Burnt patients
– Hyperpyrexia
– Thyrotoxic crisis
– Muscular activity (seizures, excessive respiratory work)
– Predominance of glucose as metabolic substrate
– Administration of exogenous bicarbonate
• Factors associated with reduced carbon dioxide production
– Hypothermia
– Hypothyroidism
– Sedation and neuromuscular blockade
– Predominance of fatty acids as metabolic substrate
P CO2 = K X ( V CO2 / MV)
MV = RR X VT
VT = Alveolar Space + Dead Space
Dead Space
Physiological dead space (VD) = Alveolar (VDA) + Anatomical (VDanat)
VD = Alveolar (VDA) + Anatomical (VDanat) +Equipment (VDequip)
Vd/Vt = 0.3
VD / VT = PaCO2 − PE TCO2 / PaCO2
Tidal Volume and Rate
VT and rate depends on the time constant.
In normal lungs :
age-appropriate ventilator rate
tidal volume of 7-10 mL/kg
Diseases associated with decreased time constants (decreased static
compliance, are best treated with :
small (6 mLlkg) tidal volume
and relatively rapid rates
Diseases associated with prolonged time constants (increased airway
resistance, e.g., asthma, bronchiolitis)
are best treated with:
relatively slow rates
and higher (10-12 mLlkg) tidal volume
Positive end-expiratory pressure (PEEP)
effects on CO2
Low levels of PEEP (3 to 5 cmH2O) have little effect
Higher levels of PEEP (8 to 15 cmH2O)
may increase the Vd/Vt ( mostly with low VT)
in recruitable lung
intrinsic PEEP
CO2
CO2
General techniques to lower carbon
dioxide production
Avoidance of pyrexia
induced hypothermia
Lowering the respiratory quotient (use of fatty acids)
Sedation and neuromuscular blockade reduce metabolic rate by around 9%
Conventional mechanical ventilation
Adjunctive pulmonary therapies
Bronchodilators
Physiotherapy
Tracheal gas insufflation
alveolar ventilation
Permissive hypercapnia
potential advantage of permissive hypercapnia:
deliberate hypoventilation
reduction in tidal volumes
reduction transpulmonary pressures
limit pulmonary injury.
In vitro,
hypercapnia reduces the activation of:
NF-kB,
intercellular adhesion molecule-1 (ICAM-1)
interleukin-8 (IL-8)
in human pulmonary endothelial cells
NF-kB is a key regulatory molecule in the activation of many pro-inflammatory genes,
including those that produce ICAM-1 and IL-8, molecules that trigger the movement
of leukocytes into the inflamed lung.
In vivo,
Hypercapnia may reduce inflammation in experimental lung injury.
Finally, hypercapnia may improve ventilation perfusion matching and intestinal and
subcutaneous tissue oxygenation
Increase in:
pCO2
pO2
MAP
FiO2
no change
increase
no change
Rate
decrease
usually no
change
increase
PIP/TV
decrease
increase
increase
Inspiratory
time
usually no
change
increase
increase
PEEP
usually no
change
increase
increase
MONITORING RESPIRATORY MECHANICS
Exhaled Tidal Volume
leak out
decrease in VTE ( PCV) : decrease in compliance
or increase in resistance
increase in VTE is indicative of improvement and
may require weaning of inflation pressures to adjust the VTE.
Peak Inspiratory Pressure
In VCV and PRVC, the PIP is determined by compliance and resistance.
increase in PIP
decreased compliance (atelectasis, pulmonary edema, pneumothorax)
or increased resistance (bronchospasm, obstructed ET).
decreasing the respiratory rate
lower PIP in patients with prolonged TC
or prolonging the TI
In such patients, a decrease in PIP suggests increased compliance
or decreased resistance of the respiratory system.
Respiratory System Dynamic Compliance
and Static Compliance
CSTAT= VTE/ (Pplat - PEEP)
CDYN= VTE / ( PIP - PEEP)
PCV
CDYN= VTE / ( PIP - PEEP)
VCV and PRVC
Assessment of Auto-PEEP
Auto-PEEP is assessed with the use of an expiratory pause maneuver
-have adverse effects on ventilation and hemodynamic status.
Management : decreasing RR
or decreasing inspiratory time
increasing the set PEEP ("extrinsic" PEEP),
Ventilator settings
1.
2.
3.
4.
5.
6.
7.
8.
Ventilator mode
Respiratory rate
Tidal volume or pressure settings
Inspiratory flow
I:E ratio
PEEP
FiO2
Inspiratory trigger
Assist – Control AC
Trigger window
Can be set
Vent breath
Spont breath sensed
Sensitivity can be set
Vent breath
Synch Vent breath
Vent breath
AC
• Patient only gets ventilator breaths
• These are just delivered at different times to
coincide with patient spontaneous effort
• Can help keep lungs recruited
SIMV
Spont breath sensed
Trigger window 2 for
supported breath
Trigger window 1
for Vent breath
Vent breath
Vent breath
Synch Vent Supported
breath
breath
Vent breath
Pressure Support
• Because it is difficult to breathe through a
ventilator, the vent can help
• It supports spontaneous effort
• Pressure support
– No background rate
– Patient determines resp rate & I:E
– Usually apnoea backup
Pressure Support
Spontaneous
breath sensed
by ventilator
Pressure is applied
throughout
inspiratory effort
CPAP & PEEP
The constant bit
CPAP and PEEP
• What do they do for your lungs?
• What about your cardiovascular system?
BiPAP
• Bi-Level Positive Airway Pressure
• 2 PEEPs basically
• Patient can breathe at any point
– Easier for patient to tolerate
– Less sedation?
• Pressure support can be added if required
Origins of mechanical ventilation
•Negative-pressure ventilators
(“iron lungs”)
•first used in Boston Children’s Hospital in
The iron lung created negative pressure in abdomen
1928
as well as the chest, decreasing cardiac output.
•Used extensively during polio outbreaks
in 1940s – 1950s
Iron lung polio ward at Rancho Los Amigos Hospital
in 1953.
Era of intensive care begun with this
• Positive-pressure ventilators
– Invasive ventilation first used at Massachusetts
General Hospital in 1955
– Now the modern standard of mechanical
ventilation
CMV
CMV
CMV
CMV
CMV
CMV
CMV-Volume
Volume
Tidal
Volume
CMV-P
A/CV
SIMV
Pressure Support Ventilation (PSV)
Patient determines RR, VE, inspiratory time – a purely spontaneous mode
CPAP and BiPAP
CPAP is essentially constant PEEP; BiPAP is CPAP plus PS
•Parameters
CPAP – PEEP set at 5-10 cm H2O
BiPAP – CPAP with Pressure Support (5-20 cm H2O)
Shown to reduce need for intubation and mortality
Respiratory Rate
• 10-12/Min – Adult
• 20+_ 3
- Child
• 30- 40
- New born
Respiratory Rate
• Increase –
Hypoxia
Hypercapnoea / Resp.Acidosis
• Decrease
Hypocapnoea
Resp.Alkalosis
Asthma / COPD
DHI
Hey not
always
the
same
buddy
Tidal Volume or Pressure setting
• Optimum volume/pressure to achieve good
ventilation and oxygenation without
producing alveolar overdistention
• Max = 6-8 cc/kg
Inspiratory Trigger
• Normally set automatically
• 2 modes:
– Airway pressure
– Flow triggering
I:E Ratio
• Normaly 1:2
• Asthma/COPD 1:3, 1:4, …
• Severe hypoxia
ARDS/ALI
Pul.Edema
1:1 , 2:1
FIO2
• Goal – to achive PaO2 > 60mmHg or a sat
>90%
• Start at 100% aim 40%
Vent settings to improve <oxygenation>
PEEP and FiO2 are adjusted in tandem
• FIO2
• Simplest maneuver to quickly increase PaO2
• Long-term toxicity at >60%
• Free radical damage
• Inadequate oxygenation despite 100% FiO2 usually
due to pulmonary shunting
• Collapse – Atelectasis
• Pus-filled alveoli – Pneumonia
• Water/Protein – ARDS
• Water – CHF
• Blood - Hemorrhage
Pulmonary edema
Translocation of fluid to peribroncheal region – helps in oxygenation
PEEP
DOPE
•
•
•
•
D- Disposition of ETT
O- Obstruction / kinking
P- Pneumothorax
E- Equipment failure
Prerequisites to extubation include:
•
1) A good cough/gag (to allow the child to protect their airway).
2) NPO about 4 hours prior to extubation (in case the trial of
extubation fails and reintubation is required).
3) Minimize sedation.
4) Adequate oxygenation on 40% FiO2 with CPAP (or PEEP) = 4.
5) The availability of someone who can reintubate the patient,
if necessary.
6) Equipment available to reintubate the patient, if necessary.