NRP 2006: Assisted Ventilation

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NRP 2006Assisted Ventilation

• Khalid Aziz,
• Canadian NRP Committee

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Cape Spear from St. Johns, Newfoundland
Labrador
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StitchesSeptember 2006
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Philosophy

• Establishing effective ventilation is the primary
  objective in the management of the apneic or
  bradycardic newborn infant in the delivery room.
  ILCOR 2005

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Objectives

• To present significant changes to the practice of
  assisted ventilation
• To explain the relevant ILCOR consensus processes
  and summarize some of the evidence

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Areas of Focus

• With respect to resuscitation of the newborn
• Characteristics of initial assisted breaths
• Devices used for assisted ventilation
• Ventilatory needs of the preterm baby

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NRP Importance of Heart Rate

• In the bradycardic infant, prompt improvement in
  heart rate is the primary measure of adequate
  initial ventilation.
• Check signs of improvement after 30 seconds of
  PPV. This requires the assistance of another
  person.

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NRP Importance of Heart Rate
Secondary or Terminal Apnea
Primary Apnea
Last Gasp
Onset of Gasping

• In the bradycardic infant, prompt improvement in
  heart rate is the primary measure of adequate
  initial ventilation.

Resuscitation
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NRP Optimal Initial Ventilation

• An initial ventilation pressure of 20 cm H2O may
  be effective (ILCOR).
• gt30-40 cm H2O may be necessary in some term
  babies (ILCOR).

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NRP Optimal Initial Ventilation
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NRP Positive End-Expiratory Pressure

• If ongoing positive pressure ventilation is
  required, PEEP of 3-6 cm of water should be used
  (Canadian NRP 2006).
• PEEP may be given with a flow-inflating bag or a
  T-piece resuscitator (Canadian NRP 2006).
• A self-inflating bag with a PEEP valve is also an
  acceptable alternative (Canadian NRP 2006).

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NRP Inflation Times

• There is insufficient evidence to recommend
  optimal initial and subsequent inflation times
  (ILCOR 2005).

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NRP Assisted Ventilation Devices

• A self-inflating bag,
• a flow-inflating bag,
• or a T-piece mechanical device designed to
  regulate pressure as needed
• can be used to provide bag-valve-mask ventilation
  to a newborn (ILCOR 2005)

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NRP Assisted Ventilation Devices
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NRP Self inflating bag and PEEP

• PEEP may be provided using an additional PEEP
  valve on a self-inflating bag
• Self-inflating bags cannot provide CPAP

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NRP The T-Piece Resuscitator
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NRP The T-Piece Resuscitator
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NRP The T-Piece Resuscitator

• The description
• Advantages and disadvantages
• Practical use

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NRP Confirming ETT Placement

• An increasing heart rate and exhaled CO2
  detection are the primary methods for confirming
  endotracheal tube placement (NRP 2006).
• CO2 detector should be used as the primary method
  for confirming endotracheal tube placement
  (Canadian NRP 2006).

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NRP Confirming ETT Placement
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NRP Pressures in Preterm Infants

• Avoid creation of excessive chest wall movement
  (ILCOR 2005).
• An initial inflation pressure of 20-25 cm H2O is
  adequate for most preterm infants (ILCOR 2005).

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NRP Other Preterm Issues

• Use the lowest pressures necessary to achieve an
  adequate response
• Consider giving CPAP (not with a self-inflating
  bag)
• Consider giving surfactant if the baby is
  significantly preterm

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The tip of the iceberg
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The ILCOR Consensus ProcessStep 1 State the
Proposal
The ILCOR Consensus Process

• Step 1A. Refine the research question(s)
• Step 1B. Gather the evidence

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The ILCOR Consensus ProcessStep 2 Assess the
Quality of Each Study

• Step 2A. Determine the level of evidence
  (levels 1-8)

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The ILCOR Consensus ProcessStep 2 Assess the
Quality of Each Study

• Step 2B. Critically assess each article for
  quality of design methods

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The ILCOR Consensus ProcessStep 2 Assess the
Quality of Each Study

• Step 2C. Determine the direction of the
  results/statistics

Step 2D. Cross-tabulate by level, quality
and direction combine summarize
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The ILCOR Consensus Process Step 2 Example of
result
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The ILCOR Consensus ProcessStep 2 Example of
result
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The ILCOR Consensus ProcessStep 2 Example of
result
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The ILCOR Consensus ProcessStep 2 Example of
result (Supporting Evidence)
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The ILCOR Consensus ProcessStep 2 Example of
result
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The ILCOR Consensus ProcessStep 2 Example of
result (neutral or opposing)
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The ILCOR Consensus ProcessStep 3 Determine the
Class of Recommendation
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The ILCOR Consensus ProcessImportant Areas in
Assisted Ventilation

• Initial Ventilation in Asphyxiated Term Newborns
• Initial Lung Inflation in Preterm Infants
• The use of CPAP during resuscitation of Very
  Premature Infants

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Initial Ventilation in Asphyxiated Term Newborns

• Step 1. State the Proposal
• 5 Hypotheses
• IPPV alone is effective
• Best indicator of adequate initial ventilation is
  heart rate
• Chest movement assesses initial ventilation
  pressure gt30cm H2O may be required
• Prolonged/sustained inflations are needed (gt1sec)
  for initial inflation of asphyxiated term infant
• Optimal IPPV is 30-40 breaths per minute
• (728 articles reviewed / 20 included)

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Initial Ventilation in Asphyxiated Term Newborns

• Step 2. Assess the Quality of Each Study
• 2A. Determine the level of evidence
• 2B. Critically assess each article
  (research design/methods)
• 2C. Determine direction of results
  statistics (/- neutral)
• 2D. Cross-tabulate

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Initial Ventilation in Asphyxiated Term Newborns

• Step 3. Determine the Class of Recommendations
• Class I
• Class IIa
• Class IIb
• Class III
• Indeterminate

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Initial Ventilation in Asphyxiated Term Newborns

• Hypothesis I
• Positive pressure alone is effective in the
  resuscitation of asphyxiated newly born infants.
• Animal Studies
• Mature fetal lambs and rhesus monkeys
• Artificial ventilation alone was effective in
  resuscitating the majority of animals following
  the last spontaneous gasp, provided the mean
  arterial BP was greater than 15mmHg
• (Dawes 1963)

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Initial Ventilation in Asphyxiated Term Newborns

• In all species ventilation of the lungs
  ...effects a rapid complete restoration of the
  cardiovascular condition to normal
• (Cross 1966)

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Initial Ventilation in Asphyxiated Term Newborns

• Criteria of Effective Treatment
• Gasping returns only after recovery of the
  circulation
• The increase in heart rate (if maintained at a
  reasonable level) is a reliable guide to this
  recovery
• (Cross 1966)
• IPPV is much more effective than hyperbaric O2 in
  newborn rabbits 85 recovered with IPPV alone
  4mins. ...or IPPV and cardiac massage
• (Campbell 1966)

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Initial Ventilation in Asphyxiated Term Newborns

• 12 fetal rhesus monkeys asphyxiated under
  controlled conditions
• 6/12 - rapid response to IPPV alone
• remaining 6 prompt response to chest
  compressions and IPPV
• mean arterial BP lower in those who required CPR
• (Adamsons 1964)
• Fetal and newborn rabbits under controlled
  asphyxia
• ...surest sign that lung inflation was going to
  succeed was an increase in heart rate and BP
• (Godfrey 1968)

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Initial Ventilation in Asphyxiated Term Newborns

• Hypothesis II
• Observing an increase in heart rate within 30
  seconds is the primary measure of adequate
  initial ventilation.
• Human Studies
• 31 full term infants, delivered by c-section,
  required intubation and ventilation
• IPPV through an endotracheal tube is at least as
  effective in producing lung expansion as is
  spontaneous respiration
• (Ditchburn 1966)
• Demonstrated that prompt increase in heart rate
  130/min. was proof of adequate ventilation
• (Palme-Kilander 1993)

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Initial Ventilation in Asphyxiated Term Newborns

• Hypothesis III
• Observing chest wall movement assesses the
  adequacy of initial ventilation pressures in
  excess of 30cm H2O may be required
• Hypothesis IV
• Prolonged or sustained inflations (gt1 second) are
  needed for the initial inflation of asphyxiated
  term infants

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Initial Ventilation in Asphyxiated Term Newborns

• Several studies looked at pressure and volume
  changes in healthy term newborns with the onset
  of spontaneous respirations
• Babies produce large negative intrathoracic
  pressures of up to 50cm H2O before lung expansion
  occurs
• 7/11 babies had formed FRC at the end of the
  first breath
• (Karlberg 1960)

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Initial Ventilation in Asphyxiated Term Newborns

• 20 healthy infants immediately after C-section
  delivery
• The pattern of breathing immediately after
  delivery is very irregular
• FRC obtained with the first breath is
  proportional to the previous inspired volume
• (Mortola 1982)

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Initial Ventilation in Asphyxiated Term Newborns
Studied the first breath of 50 babies

• 15 babies elective c-section
• 5/11 had formed FRC

• 35 babies born vaginally
• 20/21 had formed FRC

• Possible explanations
• Vaginal birth canal squeeze
• Vaginal delivery babies make a strong
  expiratory effort (expiratory pressures in c/s
  group were 25 smaller)
• Balance of fluid dynamics within the lungs
• - no opening pressure
• - inspiratory pressure volume same
• - expiratory pressure lower in c/s group
• 
  (Vyas 1981)

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Initial Ventilation in Asphyxiated Term Newborns

• Studied the establishment of FRC
• 34 term babies vaginally delivered recorded
  the first 30 seconds ( 3 breaths)
• Looked at
• Magnitude of the birth canal squeeze
• Interval between delivery of the chest and the
  onset of the first breath
• Inspiratory pressure changes
• Expiratory pressure changes
• Gaseous FRC at the end of the first breath

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Initial Ventilation in Asphyxiated Term Newborns

• Results
• No evidence of opening pressure
• All babies had a marked positive pressure during
  expiration - in 13/16 this exceeded 50cm H2O
• All except 1 formed FRC following the first
  breath
• Significant correlation between inspiratory
  volume and FRC
• emerged above all other factors in the
  formation of FRC
• (Vyas 1986)

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Initial Ventilation in Asphyxiated Term Newborns

• Studied IPPV in depressed term infants
• Ventilating pressures of 30cm H2O provide
  adequate lung ventilation
• FRC Formation

(Hull 1969)
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Initial Ventilation in Asphyxiated Term Newborns
(Hull 1969)
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Initial Ventilation in Asphyxiated Term Newborns
(Hull 1969)
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Initial Ventilation in Asphyxiated Term Newborns
(Hull 1969)
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Initial Ventilation in Asphyxiated Term Newborns

• Respiratory reflex responses
• Strong expiratory effort (rejection response)
• Inspiratory efforts (paradoxical reflex of Head)
• (Hull 1969)

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Initial Ventilation in Asphyxiated Term Newborns

• Responses to prolonged and slow rise inflation
  9 babies studied

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Initial Ventilation in Asphyxiated Term Newborns

• Results
• Physiologic responses
• Inflation mean 33.6mL (16.9-10mL)
• Formation of FRC all 9 babies formed FRC at the
  end of the first inflation
• Opening pressure
• only seen in 1 infant with slow rise
• in square wave apparent between 10-25cm H2O
• (Vyas 1981)

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Initial Ventilation in Asphyxiated Term Newborns
(Milner 1982)
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Initial Ventilation in Asphyxiated Term Newborns

• Summary
• No randomized studies
• IPPV in depressed term newborns
• Limited numbers
• Mostly C-section deliveries
• Initial respiratory pressures were highly
  variable
• 18-60cm H2O (mean 30-40cm H2O)
• Chest movement mentioned in Upton et al
• Indicator of adequate ventilation
• Palme-Kilander
• 2/3 infants required PIP gt50cm H2O
• Subsequent breaths PIPs somewhat less
• 29 (14-42cm H2O)
• Generally variable inspiratory time
• 0.5 2 secs.
• Based on limited available data

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Initial Ventilation in Asphyxiated Term Newborns
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Initial Lung Inflation in Preterm Newborns

• Step 1. State the Proposal
• Hypothesis
• Methods of achieving initial lung inflation
  during resuscitation of term infants are
  inappropriate for use in preterm infants
• Gather evidence
• 47 articles from human studies
• 13 articles from animal studies

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Initial Lung Inflation in Preterm Newborns

• Step 2. Assess the Quality of Each Study
• 2A Determine the level of evidence
• 2B Critically assess each article
  (research design/methods)
• 2C Determine direction of results statistics
  (/- neutral)
• 2D Cross-tabulate
• different endpoints

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Initial Lung Inflation in Preterm Newborns

• Step 3. Determine the class of Recommendations
• Class I
• Class II
• IIa
• IIb
• Class III
• Indeterminate

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Initial Lung Inflation in Preterm Newborns

• Animal Studies
• 44 premature rabbits
• - ventilated with standardized tidal volume
  of 10mL/kg of standardized insufflation
  pressures of 35cm H2O from 10-30 minutes
• Necrosis and degeneration of bronchiolar
  epithelium appeared in animals ventilated for 5
  min. or more
• (Nilsson 1980)
• 16 premature lambs, 8 received 4 sustained
  inflations for 5 seconds
• SI did not improve lung function
• (Klopping-Ketelaars 1994)

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Initial Lung Inflation in Preterm Newborns

• 5 pairs of premature lamb siblings
• - one of each pair given 6 manual inflations,
  35- 40mL/kg (bagging)
• - all lambs given surfactant at 30 min. of age
• Histological lung injury
• Impairment of compliance
• Inhibited the response to surfactant
• Why did a few large breaths have such a
  deleterious effect on lung function?
• High airway pressure during bagging
• The size of the breaths
• The time at which they were given
• The surfactant deficiency in the lungs
• (Bjorklund 1997)

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Initial Lung Inflation in Preterm Newborns

• 21 premature lambs
• - IPPV for 30 min. after birth (tidal volumes
  of 5mL/kg, 10mL/kg and 20mL/kg)
• - then at 30 min. - given surfactant
  and ventilated x 6hrs
• The group with tidal volumes of 20mL/kg
• Lower compliance
• Difficult to ventilate
• Depressed surfactant recovery
• Increased protein recovery
• (Wada 1997)

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Initial Lung Inflation in Preterm Newborns

• 10 premature newborn lambs
• - 2 received surfactant before birth
• - 2 before the first breath
• - 2 recruitment maneuvers 5 breaths, 8mL/kg
• - 2 recruitment maneuvers 5 breaths, 16mL/kg
  
• - 2 recruitment maneuvers 5 breaths, 32mL/kg
  
• followed by surfactant
• Decreased inspiratory capacity
• Decreased compliance
• Decreased FRC
• Decreased surfactant response
• More lung injury
• (Bjorklund 2001)

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Initial Lung Inflation in Preterm Newborns
(Bjorklund 2001)
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Initial Lung Inflation in Preterm Newborns
(Bjorklund 2001)
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Initial Lung Inflation in Preterm Newborns
(Bjorklund 2001)
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Initial Lung Inflation in Preterm Newborns

• Study A. 12 preterm lambs
• Group 1 5 lung inflations at birth ?
  surfactant
• Group 2 surfactant followed immediately by
  5 inflations
• Group 3 surfactant followed by inflations
  after 10min.
• Group 4 surfactant followed by inflations
  after 60min.
• Inflations were 16mL/kg sustained x 5seconds
• Study B. 10 pairs of twin preterm lambs
• - all received surfactant before the first
  breath
• - one of each pair got 5 inflations immediately
  after
• - the other got 5 inflations 10-15min. after
• (Ingimarsson 2004)

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Initial Lung Inflation in Preterm Newborns

• late compared to early inflations
• Lower pressures generated
• Easier to ventilate
• Better inspiratory capacity, compliance and FRC
• Histology showed satisfactory response to
  surfactant

(Ingimarsson 2004)
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Initial Lung Inflation in Preterm Newborns

• Suggests
• Preceding surfactant does not protect the lungs
  against the harmful effects of large inflations
• The sensitive period is probably very short (
  10 min.)

(Ingimarsson 2004)
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Initial Lung Inflation in Preterm Newborns

• Human Studies
• 21 preterm infants, intubation and IPPV at birth
  (mean inflation pressure 27cm H2O)
• (Hoskyns 1987)
• 70 preterm infants, (median pressure for adequate
  chest wall expansion 22.8cm H2O)
• - never required gt30cm H2O
• (Hird 1991)

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Initial Lung Inflation in Preterm Newborns

• 651 infants multi-center randomized trial
• a) compared an immediate surfactant bolus
• b) post-ventilatory aliqout strategy 10min.
• No difference in survival
• Less chronic lung disease O2 supplement at 36
  weeks in (b)
• Could be due to the vigorous bagging in the
  immediate group?
• (Kendig 1998)

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Initial Lung Inflation in Preterm Newborns

• 123 preterm infants (retrospective cohort study)
  
• 2 different delivery room policies 1994 vs.
  1996
• 1994 - ELBW infants intubated immediately for
  respiratory distress
• 1996 - NP tube inserted continuous inflation
  20-25cm H2O (15-20 sec.) ? CPAP 4-6cm.
• Mean initial pressure requirement 25cm H2O
• More infants in 1996 never intubated (25 vs. 7)
• Mortality morbidity were the same
• (Lindner 1999)

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Initial Lung Inflation in Preterm Newborns

• Human Element
• Physicians unable to detect blocked ETT
• Nurses with experience relied less on manometers
  but were also less accurate in controlling PIP
  without the devices
• Junior doctors could not assess tidal volume
  visually in relation to inflation pressure
• NEOPUFF device more consistent
• (Spears 1991)
• (Howard-Glenn 1990)
• (Stenson 1995)
• (Finer 2001)

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Initial Lung Inflation in Preterm Newborns

• Summary
• Greater emphasis on improving heart rate
• Less emphasis on good chest wall movement
• Encourages large, potentially damaging inflations
  to preterm infants at a time when their lungs are
  most susceptable to injury

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Initial Lung Inflation in Preterm Newborns
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Use of CPAP in the Delivery Room

• Step 1. State the Proposal
• Hypotheses
• CPAP is a safe and effective intervention in
  newborn resuscitation compared to Endotracheal
  Intubation
• CPAP during resuscitation of very preterm infants
  will reduce oxygen requirements and the need for
  ventilation
• The use of CPAP will decrease oxygen dependency
  at 36 wks. gestation
• Gather evidence
• 27 articles from human studies
• 3 articles from animal studies

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Use of CPAP in the Delivery Room

• Step 2. Assess the Quality of Each Study
• 2A Determine the level of evidence
• 2B Critically assess each article
  (research design/methods)
• 2C Determine direction of results statistics
  (/- neutral)
• 2D Cross-tabulate
• different endpoints

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Use of CPAP in the Delivery Room

• Step 3. Determine the class of Recommendations
• Class I
• Class II
• IIa
• IIb
• Class III
• Indeterminate

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Use of CPAP in the Delivery Room
(Finer 2004))
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Use of CPAP in the Delivery Room

• Recommendation Class B
• Acceptable useful
• Fair evidence

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