Chapter 17
Mechanical Ventilators (plus
transition to extrauterine life)
Heads Paradoxical Reflex
• Mediated by rapidly adapting pulmonary stretch receptors
(RARs) in the lungs, with properties quite distinct from those
of the slowly adapting receptors (SARs) responsible for the
Breuer-Hering inflation reflex.
• Called Paradoxical since it has the ability to supersede the
Hering reflex which normally limits large volume inspirations.
• Thought to be responsible for a babies first breath
What is the primary factor that initiates
breathing in a newborn infant?
• The fetus lives in a relatively hypoxic environment, with a pO2
of approximately 35.
• This relative hypoxia is normal for the fetus and causes the
pulmonary blood vessels to constrict.
• This raises pulmonary blood pressure quite high, higher than
the fetus's systemic blood pressure.
• So, with each heart beat, most of the cardiac output follows
the path of least resistance and flows to the fetus's body. Very
little flows to the fetal lungs, due to the relatively high
pulmonary blood pressure. This works out just fine in utero
where the fetus isn't responsible for oxygenating it's own
blood, but not so well after delivery when the placenta is no
longer available to provide oxygen.
What is the primary factor that initiates
breathing in a newborn infant?
• At the moment of birth, when the baby takes it's first breath,
the pO2 within the baby's bloodstream begins to rise, causing
the pulmonary blood vessels to begin to relax, lowering
pulmonary blood pressure.
• With subsequent breaths, the pO2 continues to rise, causing
pulmonary vasodilation, which drops the pulmonary blood
pressure lower than the systemic blood pressure (as it should
be in adult circulation), and a greater portion of cardiac output
begins to flow to the baby's lungs with each heartbeat,
allowing the baby to sufficiently oxygenate its own blood.
What is the primary factor that initiates
breathing in a newborn infant?
• As the pO2 begins to rise, the fetal shunts begin to close
(functionally), including the patent foramen ovale, the patent
ductus arteriosus and the ductus venosus. This changes the
pattern of blood flow thru the baby's heart and body to an
adult pattern. If these shunts fail to close (functionally) at
birth, or structurally within a few days-weeks of birth, then
the baby may experience problems such as decreased
oxygenation, murmur, CHF, poor feeding, poor weight gain,
etc.
• If the baby is deprived of oxygen at birth, due to complications
such as birth asphyxia, meconium aspiration or pneumonia,
these changes may not occur, and the baby may develop a lifethreatening condition called persistent pulmonary
hypertension of the newborn (PPHN).
What is the primary factor that initiates
breathing in a newborn infant?
• Perfusing its body by breathing independently instead of
utilizing placental oxygen is the first challenge of a newborn.
At birth, the baby's lungs are filled with fetal lung fluid (which
is not amniotic fluid) and are not inflated.
• The newborn is expelled from the birth canal, its central
nervous system reacts to the sudden change in temperature
and environment.
• This triggers it to take the first breath, within about 10
seconds after delivery
• With the first breaths, there is a fall in pulmonary vascular
resistance, and an increase in the surface area available for gas
exchange. Over the next 30 seconds the pulmonary blood flow
increases and is oxygenated as it flows through the alveoli of
the lungs.
What is the primary factor that initiates
breathing in a newborn infant?
• Oxygenated blood now reaches the left atrium and ventricle,
and through the descending aorta reaches the umbilical
arteries.
• Oxygenated blood now stimulates constriction of the umbilical
arteries resulting in a reduction in placental blood flow.
• As the pulmonary circulation increases there is an equivalent
reduction in the placental blood flow which normally ceases
completely after about three minutes.
• These two changes result in a rapid redirection of blood flow
into the pulmonary vascular bed, from approximately 4% to
100% of cardiac output
What is the primary factor that initiates
breathing in a newborn infant?
• The increase in pulmonary venous return results in left atrial
pressure being slightly higher than right atrial pressure, which
closes the foramen ovale.
• The flow pattern changes results in a drop in blood flow
across the ductus arteriosus and the higher blood oxygen
content of blood within the aorta stimulates the constriction
and ultimately the closure of this fetal circulatory shunt.
• All of these cardiovascular system changes result in the
adaptation from fetal circulation patterns to an adult
circulation pattern. During this transition, some types of
congenital heart disease that were not symptomatic in utero
during fetal circulation will present with cyanosis or
respiratory signs.
What is the primary factor that initiates
breathing in a newborn infant?
• Following birth, the expression and re-uptake of surfactant,
which begins to be produced by the fetus at 20 weeks
gestation, is accelerated.
• Expression of surfactant into the alveoli is necessary to
prevent alveolar closure (atelectasis). At this point, rhythmic
breathing movements also commence. If there are any
problems with breathing, management can include
stimulation, bag and mask ventilation, intubation and
ventilation.
• Cardiorespiratory monitoring is essential to keeping track of
potential problems. Pharmacological therapy such as caffeine
can also be given to treat apnea in premature newborns. A
positive airway pressure should be maintained, and neonatal
sepsis must be ruled out
What is the primary factor that initiates
breathing in a newborn infant?
• Potential neonatal respiratory problems include apnea,
transient tachypnea of the newborn (TTNB), respiratory
distress syndrome (RDS), meconium aspiration syndrome
(MAS), airway obstruction, PPHN and pneumonia/Sepsis.
• PPHN can be a result of idiopathic means or as a result of
persistent pulmonary vascular resistance. The treatment
involves treatment of the underlying cause, surfactant
delivery, PPV, Nitric Oxide, HFV, ECMO, Prostglandins, steroids
and Oxygen
Energy metabolism
• Energy metabolism in the fetus must be
converted from a continuous placental supply of
glucose to intermittent feeding.
• While the fetus is dependent on maternal
glucose as the main source of energy, it can use
lactate, free-fatty acids, and ketone bodies under
some conditions.
• Plasma glucose is maintained by glycogenolysis
• Glycogen synthesis in the liver and muscle begins
in the late second trimester of pregnancy, and
storage is completed in the third trimester
Energy metabolism
• Glycogen stores are maximal at term, but even then, the
fetus only has enough glycogen available to meet energy
needs for 8–10 hours, which can be depleted even more
quickly if demand is high. Newborns will then rely on
gluconeogenesis for energy, which requires integration,
and is normal at 2–4 days of life.
• Fat stores are the largest storage source of energy. At 27
weeks gestation, only 1% of a fetus' body weight is fat. At
40 weeks, that number increases to 16%.
• Inadequate available glucose substrate can lead to
hypoglycemia, fetal growth restriction, preterm delivery,
or other problems. Similarly, excess substrate can lead to
problems, such as infant of a diabetic mother (IDM),
hypothermia or neonatal sepsis.
Energy metabolism
• Anticipating potential problems is the key to managing most
neonatal problems of energy metabolism. For example, early
feeding in the delivery room or as soon as possible may
prevent hypoglycemia.
• If the blood glucose is still low, then an intravenous (IV) bolus
of glucose may be delivered, with continuous infusion if
necessary. Rarely, steroids or glucagon may have to be
employed.
Temperature Regulation
• Newborns come from a warm environment to the cold and
fluctuating temperatures of this world.
• They are naked, wet, and have a large surface area to mass
ratio, with variable amounts of insulation, limited metabolic
reserves, and a decreased ability to shiver.
• Physiologic mechanisms for preserving core temperature
include vasoconstriction (decrease blood flow to the skin),
maintaining the fetal position (decrease the surface area
exposed to the environment), jittery large muscle activity
(generate muscular heat), and "non-shivering thermogenesis".
Temperature Regulation
• "non-shivering thermogenesis "occurs in "brown fat“ which is
specialized adipose tissue with a high concentration of
mitochondria designed to rapidly oxidize fatty acids in order to
generate metabolic heat.
• The newborn capacity to maintain these mechanisms is
limited, especially in premature infants. As such, it is not
surprising that some newborns may have problems regulating
their temperature. As early as the 1880s, infant incubators
were used to help newborns maintain warmth, with
humidified incubators being used as early as the 1930s.
Temperature Regulation
• Basic techniques for keeping newborns warm include keeping
them dry, wrapping them in blankets, giving them hats and
clothing, or increasing the ambient temperature. More
advanced techniques include incubators (at 36.5°C), humidity,
heat shields, thermal blankets, double-walled incubators, and
radiant warmers while the use of skin-to-skin "kangaroo
mother care" interventions for low birth-weight infants have
started to spread world-wide after its use as a solution in
developing countries.[
Mechanical Ventilation
• http://www.youtube.com/watch?v=dVqurKOJuD8
• http://www.youtube.com/watch?v=9gq34tkskkE
• http://www.youtube.com/watch?v=EhQxO8pVy0A
•Support devices
•HFNC / NC
•Transport
•Servo 1
•Baby log
•Neo Puff
•HFV Jet
•Avea
•HFOV
RT Equipment in NICU
• Nasal Cannula (0.25-2L), typically set below 1L, always with a
blender and a bubble humidifier. Used for oxygenation issues only,
or A’s and B’s, weaning off of PPV
• Oxyhood: set 7-12 L, with a heated humidifier, blender, temperature
probe and O2 analyzer. Used when high FIO2 required/pneumos for
Nitrogen washout
• HFNC: used when higher flows are required up to 8L, given with
heated humidifier/circuit and special cannula. Always use with a
blender; may be used when weaning from CPAP/vent
• NCPAP: used for persistent grunting/retractions where surfatant is
not required. PEEP set from 2-6, given through prongs/mask,
through a stand alone machine or through the ventilator
RT Equipment in NICU
• Nasal SIMV: Used through a SiPAP machine or ventilator, essentially
the same as SIMV-PC except given through the nose
• Mask CPAP/PPV through a flow inflating bag, may also give through
a T-piece/NeoPuff for short term relief
• Invasive mechanical ventilation: Through a ETT, typically set in SIMV
mode in PC, or a volume targeted mode, rates set between 15-30,
Pressures are set anywhere from 10-25, FIO2 kept as low as
possible, IT anywhere from 0.2-0.8 seconds
• HFV: given as Jet ventilation or HFOV
• Nitric Oxide: typically given in tandem with HFV
• ECMO: again given in tandem with HFV or mechanical ventilation
Other equipment: HHN (although far less common in NICU), CPT via
mini massager, ABG/CBG supplies, suction equipment, airway supplies)
RT Equipment
• NOTE:
• All oxygen delivering equipment in the NICU and PICU setting
will utilize a humidifier. High flow devices will use a heated
humidifier
• The use of a blender is also common with most equipment as
is a oxygen analyzer
• Use of aerosols are uncommon due to the noise factor; except
for HHN
• Suction pressures are lower, and flows and FIO2 levels are
lower, as are PEEP levels
Introduction
• The primary objective of Mechanical
Ventilation is to support breathing until
patient respiratory efforts are sufficient.
• First mechanical ventilation for a neonate in
1959.
• One of the most important breakthroughs in
the history of neonatal care.
• Mortality from RDS decreased markedly after
MV.
• New Morbidity developed, CLD (BPD)
Indications
• Apnea (prolonged or repetitive unresponsive apnea
associated with bradycardia or cyanosis).
• Respiratory failure in newborns:
PaO2 < 50 mmHg on FIO2 ≥ 0.6
PaCO2 > 60 - 65 mmHg (> 55 in infants < 1500 gm)
pH < 7.20
• Impending ventilatory failure (worsening oxygenation and/or
respiratory distress
[↑ RR > 60 infants; > 40 children], retractions, grunting,
nasal flaring even when
ABG values are within acceptable ranges) (anticipation of
worsening lung pathology)
Indications
• There are no well defined criteria for when to initiate MV in
infants and children.
Many clinical factors come into play and must be
individualized for each patient's problem.
Early intubation and MV is recommended in many situations:
• Congenital anomalies affecting ventilatory function
(diaphragmatic hernia)
• Infants with low Apgar scores and responding poorly to
resuscitation efforts
• Infants with severe sepsis or compromised pulmonary
blood flow (PPHN)
• Premature babies < 1000 gm
• Progressive atelectatic disease
Indications
• Scheduled surgical procedure
• Any acute or chronic cardiopulmonary
insufficiency
• May be due to problem with lung, cardiovascular
system, CNS, or various metabolic disorders
Clinical signs:
• Repeated A-B spells
Indications
• The oxygenation index is a calculation used to assess
FIO2/Pressure requirements to achieve a PaO2
• A lower oxygenation index is better - this can be inferred by
the equation itself. As the oxygenation of a person improves,
they will be able to achieve a higher PaO2 at a lower FiO2. This
would be reflected on the formula as a decrease in the
numerator or an increase in the denominator - thus lowering
the OI. Typically an OI threshold is set for when a neonate
should be placed on ECMO, for example >40,>30 HFV
Blood Gas Scoring System For Assisted
Ventilation
* A score of 3 or more indicates the need for
CPAP or IMV.
Ambient O2 failure → CPAP
CPAP failure (10 cm H2O & FIO2 1.0) → IMV
** May indicate the need for CPAP or IMV by
itself, if cyanotic heart disease not present.
Contraindications
• < 23 weeks gestation (?) or birth weight of less than 400 g (ref:
NRP)
• Congenital anomalies incompatible with survival (anacephaly,
lethal genetic disorders)
• Severe prolonged code with no reasonable chance of survival
• NOTE: Parental involvement in the decision not to treat is
vital.
• Untreated/unvented pneumothorax (a contraindication for
all PPV in all age populations)
Neonatal Physiology Affecting Ventilation
• Compliant chest wall and weak cartilaginous support of
airways (excessive inspiratory efforts will collapse upper
airway and lungs, increasing Raw and decreasing Vt)
• Horizontal ribs and flatness of diaphragm reduce
potential lung expansion and Vt
• Peripheral Raw is 4x > than older children and adults
• Distal airway growth lags behind proximal airway growth
leading to increased peripheral Raw
• Possible R-L shunting (PDA and/or foramen ovale) (L-R
shunt through PDA increases the risk of pulmonary
edema)
Neonatal Physiology Affecting Ventilation
• Increased risk of atelectasis and airway closure due to
paucity of collateral ventilation between alveoli
• Surfactant deficiency (↓ CL, ↓, FRC; may grunt and/or
shorten Te to maintain FRC)
• Postnatal clearance of lung liquid and ↑ pulmonary
interstitial fluid
• High metabolic rate
• ↓ Muscle mass, ↓ oxidative capacity, ↓ Type 1 (slow
twitch) muscle fiber
Time Constant:
An index of how rapidly the lungs can
empty.
• Time constant = Compliance X
Resistance
• In BPD time constant is long because
of increased resistance.
• In RDS time constant is short because
of low compliance.
• Normal = 0.12-0.15 sec
Time Constant
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Inspiratory time must be 3-5 X time constant
One time conststant = time for alveoli to discharge
63% of its volume through the airway.
Two time constant = 84% of the volume leaves
Three time constant = 95% of volume leaves.
In RDS: require a longer I time because the lung will
empty rapidly but require more time to fill.
• In CLD: decrease vent rate, which allows to lengthen
the I time and E time.
Relationship to FRC
Neonatal Ventilation
• Time Cycled and Pressure Limited Ventilation
with SIMV (most common type of conventional
ventilation in the NICU)
• Inspiration is stopped when the selected
inspiratory time has been reached
• PIP is the maximum amount of pressure
exerted on the patient’s airway during the
inspiration
• Initial values = 16-20 cmH20 of PIP
• Good chest rise and Good breath sounds
Neonatal Ventilation
Volume Controlled Ventilators: A preset volume of gas is
delivered to the system after which inspiration is
terminated.
• When this gas has been delivered by the piston
inspiration is terminated.
• Tidal Volume
• 4-6 ml/kg in low–birth-weight preemies
• 5-8 ml/kg in term infants
• 7-10 ml in pediatrics and adolescent patients
• Volume losses by leaks from tubing system around the
endotracheal tube.
• Not common, unless using Volume targeted modes, such
as with the Baby Log by Drager.
Neonatal Ventilation
• Peep = Positive pressure maintained in the patient’s
airway during expiration; typically set between 3-5
cmH2O in most babies due to low FRC. Rarely do you go
above 6 or below 3.
• Prevents collapsed alveoli
• Increases FRC
• Improves compliance
• Improves oxygenation
• Decreases intrapulmonary shunting
• Allows for lower PIPs to be used
Mechanical Ventilation: Modes
• All modes are available to
the neonate
• Time cycled IMV (with
pressure limiting)
• Newer neonatal vents may
allow volume cycled IMV
• Newer neonatal
ventilators can do A/C
volume cycle or pressure
control
Initial Setting on neonatal vent
• Time cycled – Pressure Limited ventilator
• PIP set 15 – 20 cm H20
• Achieve VT range of 4-6 ml/kg
• Peep set 3 – 5 cm H2O (assess MAP, CXR 8-9 ribs
expanded)
• Rate set 20 – 40 bpm
• Flow set 6 – 8 lpm
• I time set .3 - .5 seconds for LBW and .5 - .8 seconds
for larger infants
• Keep alarms tight/set in SIMV mode, may use PSV 3-5
Settings
• PIP – good chest excursion, good lung
aeration
• Vt in pressure control = PIP – PEEP
• Vt in pressure control changes with change
in compliance and resistance
• PIP set – change only with changes in
compliance and resistance in 2 cm
increments
Inspiratory Time
Positive End Expiratory Pressure
Managing Ventilator Settings
Inspiratory Trigger Mechanism
•Time
–Controlled Mechanical Ventilation – NO patient interaction
•Pressure
–Ventilator senses a drop in pressure with
patient effort
•Flow
–Ventilator senses a drop in flow with patient effort
•Chest impedance / Abdominal movement
–Ventilator senses respiratory/diaphragm or abdominal
muscle movement
•Diaphragmatic activity
•NAVA- Neurally adjusted ventilatory assist
•http://www.youtube.com/watch?v=fq2cna71G_o
Target Values: MAP
Mean Airway Pressure
• Average pressure exerted on the airways from the start of one
inspiration until the next
• Is affected by IT, PIP, Rate, and PEEP
• Baro/Volutrauma seen with values above 12 cmH2O
• It is the most powerful influence on oxygenation!
CPAP vs PEEP
• Same distending alveolar pressure
• PEEP is used in conjunction with ventilator rate
• CPAP is used in spontaneously breathing patient,
typically with use of nasal prongs or mask, not
common with ETT in place, although PSV can be
used along with CPAP
Methods of administering
CPAP
• Endotracheal Tube
• Patent airway, airway clearance
• Disadvantage: plugging, malacia, infection
• Nasal Prongs
• Decrease infection, no malacia
• Disadv. = plugging,pressure necrosis, gastric distention
• Nasopharyngeal
• Pressure necrosis, infection
• Face Mask
• Temporary measure prior to intubation or for apnea
episode
CPAP
Indications:
• Refractory Hypoxemia
• PaO2 < 50 on an FIO2 of 60% or >
• Many hospitals use 50% as the upper limit before
changing to CPAP
• Transitional therapy between simple O2 therapy
and mechanical ventilation
• Usually in the early stages of a disease or when
recovery starts
• Any disease that causes increased elastic
resistance and alveolar instability
CPAP: EFFECTS
• Increased FRC , ie, back towards normal
• Decreased shunt
• Adequate PaO2 at minimal FIO2
• W.O.B. ?
• By increasing FRC, CPAP should decrease the W.O.B.
• However, it requires active exhalation which increases
W.O.B.
• To go on CPAP an infant needs to be breathing
spontaneously and to have normal (or slightly
lowered) PaCO2
CPAP: Administration
Techniques
• Mostly flow resistors
• To change CPAP level,
change either flow rate or
the amount of resistance
• May be administered via
mask, nasal cannula,
hood, or ET tube
• An orogastric tube may be
needed if using a mask,
cannula, or hood
•SiPAP machine
•Bubble CPAP
CPAP: Management Technique
• Start at current FIO2 or slightly >
• Start at 4-5 cmH2O
• Titrate level in 1-2 cmH2O increments until PaO2 is
acceptable
• Watch pulse oximeter or TCM as well
• Maximal level is usually 10-12 cmH2O
Weaning:
• Get FIO2 to 50% or <
• Decrease CPAP in 1-2 cmH2O increments
• Monitor for stability in vital signs, ABGs, and pulse oximeter
• If on ET tube, extubate when CPAP is 2 cmH2O
Delivery Systems (cont.)
Delivery Systems (cont.)
Delivery Systems (cont.)
Delivery Systems (cont.)
Delivery Systems (cont.)
Delivery Systems (cont.)
CPAP Hazard, breakdown of
septum
Common method
• High flow nasal cannula: Although you are not
setting a PEEP level, you are setting a flow rate
up to 8L at max. The flow will create a expiratory
resistance thus creating a small peep level.
• Most HFNC start around 2-6 L, it is always heated
to body temperature at 100% RH, using a heated
humidifier; used as an alternative to CPAP or as a
weaning tool from CPAP
ET - CPAP in Pediatrics
Pre and Post operatively to support structures
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Subglottic stenosis
Cleft palate
Laryngeal papillomas
Neck tumors
Tonsillitis
epiglottitis
Indications for NCPAP
AARC Clinical Guidelines
• Increased WOB with retractions, flaring,
grunting and cyanosis
• Inadequate ABG’s
• Presence of poor expansion on CXR
• Presence of conditions responsive to CPAP
• RDS, Pulmonary edema, atelectasis,
apnea, tracheal malacia, TTN
Contraindications to NCPAP
Guidelines
• Upper airway abnormalities
• TEF, choanal atresia (REQUIRE ETT)
• Severe cardiovascular instability and
impending arrest
• Unstable respiratory drive
• Ventilatory failure
• NEC
Hazards of NCPAP
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Hemodynamic compromise
Pulmonary Baro/Volutrauma
Gastric insufflation
Air leaks
Ventilation Perfusion Mismatch
CO2 retention and increased WOB
Increase in PVR due to impedence of blood flow
Nasal irritation with septal distortion
Pressure necrosis
Nasal mucosal damage due to inadequate
humidification
Physiologic Deadspace
• Physiologic = anatomic + alveolar
• Anatomic = Gas that fills the airways and never
participates in gas exchange
• Alveolar = gas that goes to unperfused alveoli
and thus never participates in gas exchange
• Nl physiologic Vd in neonate = 2cc/kg
Flow rate
• Flow rate used determines the type of
wave pattern
• Goal is to set flow to allow maximum
diffusion time without causing turbulent
flow
• Diffusion time is the length of time that
the gas is in contact with the alveoli
Flow Rate
Target Values: ABGs
• pH: 7.25 – 7.45
• PaCO2: 35-55 mmhg
• Increased chances of intracranial bleed if above 55
mmhg
• PaO2: 50 – 70 mmhg
• Capillary is 35 – 50 mmhg
• May allow permissive hypercapnia for severe
prematurity to prevent VILI (BPD, PIE)
• Capillary Blood gas ranges differ dramatically with pH
7.25-7.35
• CO2 45-60
• Trend ABG values using TCOM or ETCO2 and
oxygenation using a pulse ox SpO2
Strategies to Prevent
Non-Permissive Hypercapnia
• Define optimum PaCO2 levels
• Level to at which you will intervene
• Level to at which you will wean
• Ventilate at optimal FRC
• Continuous monitoring of tidal volume
• Use least pressure for maximal tidal volume
• Facilitate spontaneous breathing
• Consider “dual wean” of driving pressures
• Consider pseudo-adaptive strategies
Adjusting Ventilator
Parameters
• To change PaCO2 ONLY, change rate
• To increase PaCO2 only, decrease rate
• To decrease PaCO2 only, increase rate
• To Change PaO2 ONLY, change FIO2, PEEP, or IT
• FIO2 is changed in 1- 5 % increments
• PEEP is changed in 1 – 2 cmH2O increments
• To change both PaCO2 and PaO2 at the same
time, but in opposite directions, change PIP
• Increase PIP, PaO2 increases, PaCO2 decreases
• Decrease PIP, PaO2 decreases, PaCO2 increases
Adjusting Ventilator
Parameters
Peak Inspiratory Pressure (PIP):
• Changes in PIP affect both PaO2& PaCO2by altering the
MAP.
• Increase in PIP:Increase in PaO2
• Decrease in PaCO2
• A high PIP should be used cautiously because it may
increase the risk of volutrauma = air leak and BPD
• Common mistake “large babies need higher PIP”
requirement is strongly determined by compliance
Adjusting Ventilator
Parameters
Rate: Change in rate alter alveolar minute
ventilation
• High rate low TV is strongly preferred
• Rate change alone with constant I:E ratio
do not alter MAP
• Any change in inspiratory time that
accompany change in rate will alter MAP
Adjusting Ventilator
Parameters
FIO2:Changes alter Alveolar Oxygen Pressure
Flow: Not well studied in infants
• Minimal effects on ABG
• In general 8-12 LPM
• High Flow is needed with short inspiratory time
to achieve adequate TV.
Adjusting Ventilator
Parameters
Oxygenation Depends largely on the FIO2
• Oxygenation increase linearly with
increase in MAP.
• MAP is a measure of the average pressure
to which the lungs are exposed.
• Generally keep FIO2 lower than 40% if
possible
Increased I time and Inverse IE
Ratios
• Used when increasing FIO2 and PEEP is NOT
raising PaO2
• Used for increased elastic resistance with short
time constant
• RDS, atelectasis, bilateral pneumonia
• Rate should be no greater than 30 and PIP
should be no greater than 30 cmH2O
Monitoring During Mechanical Ventilation
• Essential aspects of monitoring
• Calculation of effective tidal volume
• Close observation of the patient (vitals,
ETT location, B/S…)
• Noninvasive methods of determining
oxygenation and ventilation status
(SPO2, TCOM, ETCO2…)
• Direct measurement of blood gas
values (CBG, ABG…)
Weaning from Mechanical Ventilation
• Initiation
• Significant resolution or reversal of
the initial pathologic condition
(note CXR, labs, vitals…)
• Stable condition
• Adequate nutrition
• Able to breathe spontaneously
Weaning from Mechanical Ventilation (cont.)
• Initiation
• Acceptable ventilator settings
(FIO2 less than 40%, Rate low limit
10-15, PIP levels at minimum,
PEEP 3-5)
• Assessment of ventilatory muscle
strength
• VC, MIP, RSBI not assessed
Weaning
• Decrease FIO2 and PEEP (as already described
for CPAP)
• When rate is down to 10-12, try CPAP
• Decrease PIP to 10-20 cmH2O
• When stable on CPAP of 2 cmH2O and FIO2 of
40% or less, extubate
• Start weaning with the parameter that is most
extreme
• Monitor for stability of vital signs, TCM values,
and pulse oximeter values at all times
Advancing Concepts
• Automated regulation of the inspired
oxygen (closed loop FIO2)
• Partial support
• Negative pressure ventilation
Mechanical Ventilation:
Hazards
• Problems associated with increased mean ITP
• Hemodynamic compromise, pulmonary baro/volutrauma
• Mechanical failure
• Usually human failure!
• BPD, ie, Bronchopulmonary Dysplasia
• http://www.youtube.com/watch?v=W0lGTifk3Hs
Mechanical Ventilation:
Hazards
Mechanical Ventilation:
Hazards
• Pulmonary interstitial emphysema (PIE) is a collection of air outside
of the normal air passages in the body and instead is found inside
the connective tissue of the peribronchovascular sheaths,
interlobular septa, and visceral pleura.
• This collection develops as a result of alveolar and terminal
bronchiolar rupture. Pulmonary interstitial emphysema is more
frequent in premature infants who require mechanical ventilation
for severe lung disease.
• Causes:
• Prematurity
• Respiratory distress syndrome (RDS)
• Meconium aspiration syndrome (MAS)
• Amniotic fluid aspiration
• Sepsis, or other infections
• Mechanical ventilation
HFV
Definition: Ventilation at a high rate at least 2 –4 times
the natural breathing rate, using a small TV that is less than
anatomic dead space:
• Types: High Frequency Jet Ventilator (HFJV)Up
to 600 breath / min
• High Frequency Flow Interrupter (HFFI)Up to
1200 breath / min
• High Frequency Oscillatory Ventilator
(HFOV)Up to 3000 / min
High-Frequency Ventilation
HFV
Indications
When conventional ventilation fails
• –reduced compliance
• Increased OI
• –RDS/ARDS
• –airleak/PIE
• –meconium aspiration
• –BPD
• –pneumonia
• –atelectases
• –lung hypoplasia
• –PPHN
HFV
Introduction
• The respiratory insufficiency remains one of the major causes
of neonatal mortality.
• Intensification of conventional ventilation with higher rates
and airway pressures leads to an increased incidence of
barotrauma.
• Either ECMO or high-frequency oscillatory ventilation might
• resolve such desperate situations.
• Since HFOV was first described by Lunkenheimer in the early
• seventies this method of ventilation has been further
developed and is now applied the world over.
HFV
There are three distinguishing characteristics of
• high-frequency oscillatory ventilation:
• The frequency range from 5 to 50 Hz (300 to
3000 bpm)
• active inspiration and active expiration
• Tidal volumes: about the size of the deadspace
volume
HFV
HFV
Oscillators provide active inspiration and active
expiration with sinusoidal waveforms:
• Piston oscillators move a column of gas rapidly
back and forth in the breathing circuit with a
piston pump.
• Its size determines the stroke volume, which is
therefore fairly constant. A bias flow system
supplies fresh gas
HFV
The "flow-interrupters" chop up the gas flow into the
patient circuit at a high rate, thus causing pressure
oscillations. Their power, however, depends also on the
respiratory mechanics of the patient
Three parameters determine oscillatory ventilation:
• Firstly, there is the mean airway pressure (MAP): around
which the pressure oscillates.
• Secondly, the oscillatory volume: which results
• from the pressure swings and essentially determines the
effectiveness of this type of mechanical ventilation.
• Thirdly, the oscillatory frequency: the number of cycles
per unit of time.
HFV
• MAP set 3-5 higher than conventional ventilator MAP, adjust
with bias flow, increased for lung expansion and oxygnation
• AMP (set with power)
• The term amplitude has stood for pressure amplitude.
• In the end, however, ventilation does not depend on the
pressure amplitude but on the oscillatory volume.
• as a setting parameter the amplitude is one of the
determinants of oscillatory volume.
• The oscillatory volume exponentially influences CO2
elimination
• During HFV volumes similar to the deadspace
• volume (about 2 to 2.5 ml/kg) should be the target.
HFV
In any HF ventilator, the oscillatory volume depends
characteristically on the oscillatory frequency.
Normally, lower frequencies permit higher volumes.
Even small changes in resistance and/or compliance of the
respiratory system, e.g. by secretion in the airways, or
through the use of a different breathing circuit or ET tube,
can change the oscillatory volume and thus the
effectiveness of HFV.
Hertz set 10-15
HFV
Oscillatory ventilation on its own can be used in the CPAP mode,
or with superimposed IMV strokes, usually at a rate of 3 to 5
strokes per minute.
• The benefit of the IMV breaths is probably due to the opening
of uninflated lung units to achieve further ‘volume
recruitment’.
• Sometimes very long inspiratory times (15 to 30 s) are
suggested for these sustained inflations
Bunnell Life Pulse Jet Ventilator
Hi-Lo Jet Endotracheal Tube
SensorMedics 3100A/3100B HFOV
Circuit Considerations
• Very low circuit compliance (typically
secured to warmer)
• Intrinsic timing mechanisms
• Control over inspiratory times
• Sufficient time for gas egress
• Adequately humidify gases
• Alarms and fail-safe devices
Ventilator Management
• Initial management
• Proper gas temperature and humidity
• Ventilator and circuit position
• Initial settings are lower than anticipated
• Appropriate primary therapies
Clinical Management Strategies
• High-volume strategy
• Optimize lung inflation
• Minimize ventilation-perfusion
Sustained Inflations
• Applying plateau pressures at levels in
excess of expected alveolar opening
pressures for periods of 5 to 30 seconds
Clinical Management Strategies
• Low volume
• Allows the lung to slowly deflate or
minimizes ongoing air leakage
• Provides tolerable ventilation while
accepting a higher FIO2
Weaning
• Minute ventilation
• HFFI and HFOV
• Reducing oscillatory amplitude during
• HFJV
• Decreasing peak pressure and on time
• mPaw
• Radiographic assessment of lung volume
• FIO2
Care of the Patient
• Positioning
• Endotracheal tube
• Suctioning (keep at a minimum during HFV)
• Monitoring (assess chest wiggle from clavicles to
mid belly)
Troubleshooting
• Chest wall movement (increase AMP for
decreased movement, increase MAP per
CXR expansion)
• Cardiac output
• Pathology
• Specific for equipment
Drager Babylog 8000 plus
•Used at Kaiser,
Vol, Guaranteed,
essentially PRVC
Sechrist IV-200 SAVI
Viasys Avea
Drager Evita 4/XL
Puritan-Bennett 840
•Used at Redlands
Maquet Servo i
Hamilton-G5
GE Healthcare
Engstrom Carestation
Puritan-Bennett Companion
2801
Philips Respironics Lifecare PLV102
LTV 900/950/1000
Newport HT- 50