Weaning from mechanical ventilation
Newth C et al. Pediatr Crit Care Med 2009; 10:1–11
Peter C. Rimensberger
Pediatric and Neonatal ICU, Department of Pediatrics
University Hospital of Geneva, Geneva, Switzerland
Weaning / Extubation failure:
Is it a real problem in the PICU ?
Reported extubation failure rates in
PICUs range from 4.1% to 19%
Baisch SD, Wheeler WB, Kurachek SC, Cornfield DN. Extubation
failure in pediatric intensive care incidence and outcomes.
Pediatr Crit Care Med 2005; 6:312–318.
Edmunds S, Weiss I, Harrison R. Extubation failure in a large
pediatric ICU population. Chest 2001; 119:897–900.
Fontela PS, Piva JP, Garcia PC, et al. Risk factors for extubation
failure inmechanically ventilated pediatric patients.
Pediatr
Crit Care Med 2005; 6166–170.
Effect of Mechanical Ventilator Weaning
Protocols on Respiratory Outcomes in Infants
and Children:
A Randomized Controlled Trial
In contrast with adult patients, the majority of children are weaned
from mechanical ventilator support in 2 days or less.
Weaning protocols did not significantly shorten this brief duration
of weaning.
Adrienne G. Randolph et al. JAMA 2002;288(20):2561-2568
Weaning: The key questions
1. Is the cause of respiratory failure gone or
getting better ?
2. Is the patient well oxygenated and ventilated ?
3. Can the heart tolerate the increased work of
breathing ?
Discontinuation of Mechanical Ventilation
To discontinue mechanical ventilation requires:
– Patient preparation
– Assessment of readiness
 For independent breathing
 For extubation
– A brief trial of minimally assisted breathing
 An assessment of probable upper airway patency after
extubation
– Either abrupt or gradual withdrawal of positive
pressure, depending on the patient’s readiness
Factors that may contribute to
extubation failure in pediatric patients
• young age
• duration of mechanical ventilation
• prolonged treatment with sedatives and analgesics
Fontela PS, Piva JP, Garcia PC, et al.
Risk factors for extubation failure in mechanically ventilated pediatric patients.
Pediatr Crit Care Med 2005; 6166–170.
Failure rate of planned extubations of patients within the first 48 hrs
of arrival in the pediatric intensive care unit (PICU) is, on average,
half that of the rate for patients ventilated for longer than 48 hrs.
Kurachek SC et al.Crit Care Med 2003; 31:2657–2664
Ventilation > 48 hours:
contrary to common perception there is no relationship
between the duration of MV and rates of failed extubation
Kurachek SC et al.Crit Care Med 2003; 31:2657–2664
Concepts of Weaning
Classical Methods for Gradually
Withdrawing Ventilator Support
The most common weaning approach:
 gradual reduction of ventilatory support
1) By reducing ventilatroy rate: IMV or SIMV
2) By reducing inspiratory pressure: PS
PS is often combined with IMV/SIMV during weaning
Volume support and volume-assured pressure support are special forms of
PS available in certain ventilators that guarantee a minimal tidal volume per
assisted breath.
Weaning with volume support is semiautomatic, where the PS level
required to maintain a certain tidal volume is reduced automatically as
respiratory mechanics improve.
Getting ready for extubation
• Weaning
– decrease the PEEP (4-5)
– decrease the rate
– decrease the PIP (as needed)
• What you want to do is decrease
what the vent does and see if the
patient can make up the difference….
Controlled ventilation
Ventilator work
Paw = Pvent + Pmus
Airway pressure
Trigger patient
Inspiration
Expiration
Assisted Ventilation
Pvent
Patient work
Ventilator work
J.J. Marini, et al Am Rev Respir Dis 1986: 134: 902-909
Spontaneous Breathing Trials
and Extubation Readiness Tests
Spontanoeus Breathing Test (SBT)
SBT conducted on PS of 10 cm H2O
versus
SBT using a T-piece
 no difference
Farias JA et al. Intensive Care Med 2001; 27:1649–1654
Of the 323 patients (77%) who passed the SBT and
were extubated, 14% were reintubated within 48 hrs.
Respiratory rate, tidal volume, rapid shallow breathing
index (RSBI), and maximal negative inspiratory pressure
(PImax) were all poor predictors of extubation outcome.
Farias JA et al. Intensive Care Med 2002; 28:752–757
Rapid Shallow Breathing Index (RSBI): f/VT
The frequency to tidal volume ratio (or rapid shallow breathing
index, RSBI) is a simple and useful integrative indicator of the
balance between power supply and power demand.
In adults: A rapid shallow breathing index < 100 generally indicates
adequate power reserve.
In this instance, the RSBI indicated that spontaneous breathing without
pressure support was not tolerable, likely due in part to the development of
gas trapping.
Limitations of RSBI in children
wide range of age groups with different respiratory rates
Weaning failure: Objective Criteria
RR above normal age limits:
< 6 months:
20–60 breaths/min
< 2 years:
15–45 breaths/min
< 5 years:
10–35 breaths/min
or > 1,5 x normal
F. Leclerc, O. Noizet, W. Chaari, A. Sadik, Y. Riou
Principles of mechanical ventilation weaning in paediatric intensive care
Annales Françaises d’Anestésie et de Réanimation 28 (2009) 685–687
Rapid Shallow Breathing Index (RSBI): f/VT
Compliance, Resistance, Oxygenation,
Pressure Index (CROP Index):
(Dynamic Compliance x Maximal Negative
Inspiratory Pressure x (PaO2/PAO2)/
Respiratory Rate)
Venkataraman ST et al. Crit Care Med 2000; 28:2991–2996
Rapid Shallow Breathing Index (RSBI): f/VT
Compliance, Resistance, Oxygenation,
Pressure Index (CROP Index):
(Dynamic Compliance x Maximal Negative
Inspiratory Pressure x (PaO2/PAO2)/
Respiratory Rate)
Volumetric Capnography:
physiologic dead space (VD/VT)
Measurement of End-tidal CO2 and Dead Space
The Single Breath CO2 Curve
Phase 1:
- airway deadspace
Phase 2:
- mixing of airway deadspace
and alveolar gas
Phase 3:
- alveolar volume
The Single Breath CO2 Curve with added PaCO2 value
Area X = volume of CO2
Area Y = wasted ventilation due to alveolar deadspace
Area Z = wasted ventilation due to airway deadspace
Physiologic VD / VT
Physiologic Deadspace
Alveolar Deadspace
= (Y+Z) / (X+Y+Z)
= (VD / VT) * (VT)
= VD phys - VD airway
Deadspace to tidal volume ratio
predicts successful
extubation in infants and children
VD/VT ≤ 0.50 reliably predicts extubation
success with 75% sensitivity and 92% specificity,
whereas a VD/VT > 0.65 identified patients at risk
for failure
Hubble CL, Gentile MA, Tripp DS, et al:
Crit Care Med 2000; 28:2034–2040
The Single Breath CO2 Curve and VCO2
Airway deadspace (VD airway) = area p
Volume of CO2 = area X.
Adding volumes of each breath gives CO2 elimination in ml / min
Volumetric CO2 recording
MV 
SV not
present
VCO2 
Not ready
to extubate
Volumetric CO2 Monitoring
• Watch VCO2 (CO2 elimination) over time as
wean ventilator
• If mechanical ventilation taken over by
spontaneous ventilation with VCO2 remaining
stable or increasing, then probably approaching
extubation point
Predictors of extubation success and failure in
mechanically ventilated infants and children
Khan, Nadeem; Brown, Andrew; Venkataraman, Shekhar T.
Critical Care Medicine 199624(9):1568-1579
Predictors of
extubation success
and failure in
mechanically
ventilated infants
and children
Venkataraman ST
Crit Care Med 2000; 28:2991–2996
Reasons for reintubation
Venkataraman ST et al. Crit Care Med 2000; 28:2991–2996
Preextubation variables easily obtained at
the bedside can predict the relative risk of
reintubation
a spontaneous tidal volume that is at least normal,
a low FIO2,
a low Paw,
a low OI,
a low PIP,
a high dynamic compliance,
a low FrVe (fraction of total minute ventilation provided by the
ventilator)
a normal or high Vt/Ti
(mean inspiratory flow)
are associated with a low risk of failure
Venkataraman ST et al. Crit Care Med 2000; 28:2991–2996
Sedation?
Adrienne G. Randolph et al. JAMA 2002;288(20):2561-2568
The “air leak” test
to predict which patients are at risk for
postextubation stridor and extubation failure
76% of the physicians routinely use the “air
leak” test test prior to extubation
Foland JA, Super DM, Dahdah NS, Mhanna MJ.
The use of the air leak test and corticosteroids in intubated children: a
survey of pediatric critical care fellowship directors.
Respir Care 2002; 47:662–666
The ‘air leak’ test
to predict which patients are at risk for
postextubation stridor and extubation failure
Increased risk for post-extubation stridor or extubation
failure when there is absence of a leak around the ETT or
leak at a > 30 cm H2O
Kemper KJ et al. Crit Care Med 1991; 19:352–355
Seid AB et al. Arch Otolaryngol Head Neck Surg 1991; 117:880–882
A leak around the ETT at > 20 cm H2O had a sensitivity of
83.3% in predicting post-extubation stridor in patients age
> 6 years
Mhanna MJ et al. Crit Care Med 2002; 30:2639–2643
3 x higher incidence of adverse events in patients without
an air leak at 25cmH2O
Suominen Pet al. Paediatr Anaesth 2006; 16:641–647.
Prophylactic systemic corticosteroids in an
attempt to minimize post-extubation stridor ?
Reduced incidence of post-extubation stridor in both
neonatal and pediatric patients
Trend towards decreased rates of re-intubation in the
corticosteroid groups (statistically not significant)
But there was considerable variation noted in the
pediatric trials examined in this meta-analysis, which the
authors attributed to possible differences in risk among
the populations studied.
Markovitz BP, Randolph AG. Corticosteroids for the prevention of reintubation and
postextubation stridor in pediatric patients: A meta analysis.
Pediatr Crit Care Med 2002; 3:223–226.
Prophylactic systemic corticosteroids in an
attempt to minimize post-extubation stridor ?
In neonates: RR 0.42; 95% CI 0.07 to 2.32
In children:
significantly reduced in children with
underlying airway abnormalities (n = 62)
but not in the study that excluded these
children (n = 153)
In adults
(n = 1953)
RR 0.48; 95% CI 0.19 to 1.22 for reintubation
RR 0.47; 95% CI 0.22 to 0.99 for stridor
Markovitz BP, Randolph AG, Khemani RG:
Corticosteroids for the prevention and treatment of post-extubation stridor
in neonates, children and adults.
Cochrane Database Syst Rev 2008; (2):CD001000
Using corticosteroids to prevent (or
treat) stridor after extubation
has not proven
effective for neonates, children or
adults. However, given the consistent
trend toward benefit, this intervention
does merit further study
Markovitz BP, Randolph AG, Khemani RG:
Corticosteroids for the prevention and treatment of post-extubation stridor
in neonates, children and adults.
Cochrane Database Syst Rev 2008; (2):CD001000
Extubation Criteria
1. Neurologic
2. Cardiovascular
3. Pulmonary
Neurologic
• Patient must be able to protect his airway, e.g,
have cough, gag, and swallow reflexes.
• Level of sedation should be low enough that
the patient doesn’t become apneic once the
ETT is removed.
• No apnea on the ventilator.
• Must be strong enough to generate a
spontaneous TV of 5-7ml/kg on 5-10 cm H2O
PS or have a negative inspiratory force (NIF) of
25cm H2O or higher.
• Being able to follow commands is preferred.
Cardiovascular
• Patient must be able to increase cardiac
output to meet demands of work of breathing.
• Patient should have evidence of adequate
cardiac output without being on significant
inotropic support.
• Patient must be hemodynamically stable.
Pulmonary
• Patient should have a patent airway.
• Pulmonary compliance and resistance should be near
normal.
• Patient should have “normal” blood gas and work-ofbreathing on the following settings:
– FiO2 <40%
– PEEP ±5cm H2O
– PS 5-8cm H2O
– Spontaneous TV of 5-7ml/kg
– Close to normal breath rate according to age
Conclusions:
Weaning Readiness and Extubation Criteria
1. Ability to protect upper airway
Effective cough
Alertness
2. Improving clinical condition
3. Adequate lumen of trachea and larynx
“Leak test” during airway pressurization
Conclusions:
Weaning Readiness and Extubation Criteria
Upper airway obstruction is the single most common
cause of extubation failure.
A reliable method of assessing readiness for weaning
and predicting extubation success is not evident
from the pediatric literature.
Weaning is often not considered early
enough in the course of ventilation.
Extubation
– Control of airway reflexes
– Patent upper airway (air leak around tube?)
– Minimal oxygen requirement
– Minimize pressure support (0 - max 10)
(Normal compliance = Vt 8 ml/kg with PS of 8)
– Comfortable spontaneous breathing
– “Awake ” patient