1. 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

2. 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.

3. A Randomized Controlled Trial
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):

4. Weaning: The key questions
Is the cause of respiratory failure gone or getting better ?
Is the patient well oxygenated and ventilated ?
Can the heart tolerate the increased work of breathing ?
In truth, you are always weaning a patient in the sense that you are always trying to minimize the ventilator settings. “True” weaning implies a different expectation - that the patient is improving and will soon not need mechanical ventilation. This usually happens when the disease process is improving or resolved and the patient has acceptable parameters. It is important to assess the ability of the heart to handle the increased demands that extubation may place upon it (e.g., pneumonia/ARDS has resolved but significant septic shock with cardiovascular collapse is present).

5. 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

6. 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.

7. Kurachek SC et al.Crit Care Med 2003; 31:2657–2664
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

8. 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

9. Concepts of Weaning

10. Classical Methods for Gradually Withdrawing Ventilator Support

11. 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.

12. 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….
Weaning is really the transfer of demands from the ventilator to the patient. By decreasing the rate, the FiO2 and the PEEP, you are asking the patient to do more. The rate at these parameters are decreased will often depend on the acuity of the disease process. The patient who was intubated because of sedation secondary to a drug overdose may wean rapidly when they are awake as compared to the child recovering from ARDS who may take weeks to completely wean from mechanical ventilatory support. The rate can be decreased in increments of 2-5 breaths/minute (or more) as dictated by the clinical situation. An arterial blood gas or end tidal CO2 monitor can be used to assess the PaCO2 after these changes. PEEP is generally lowered in increments of 1-2 mmH2O per change. As changes in oxygenation or ventilation may not be immediately apparent after a decrease in PEEP, these changes are not made more often than every 6-8 hours. [fair statement?]

13. J.J. Marini, et al Am Rev Respir Dis 1986: 134: 902-909
Controlled ventilation
Ventilator work
Paw = Pvent + Pmus
Trigger patient
Inspiration
Expiration
Airway pressure
Assisted Ventilation
Pvent
Patient work
Ventilator work
J.J. Marini, et al Am Rev Respir Dis 1986: 134:

14. Spontaneous Breathing Trials and Extubation Readiness Tests

15. SBT conducted on PS of 10 cm H2O
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

16. 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.

17. Limitations of RSBI in children
wide range of age groups with different respiratory rates

18. 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

19. 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)

20. Venkataraman ST et al. Crit Care Med 2000; 28:2991–2996

21. 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)

22. 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

23. 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 = (Y+Z) / (X+Y+Z)
Physiologic Deadspace = (VD / VT) * (VT)
Alveolar Deadspace = VD phys - VD airway

24. 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

25. 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

27. Volumetric CO2 recording
MV 
SV not
present
VCO2 
Not ready
to extubate

28. 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

29. Predictors of extubation success and failure in
mechanically ventilated infants and children
Khan, Nadeem; Brown, Andrew; Venkataraman, Shekhar T.
Critical Care Medicine (9):

30. Predictors of extubation success and failure in
mechanically ventilated infants and children
Venkataraman ST
Crit Care Med 2000; 28:2991–2996

31. Reasons for reintubation
Venkataraman ST et al. Crit Care Med 2000; 28:2991–2996

32. 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

33. Harikumar G et al AJRCCM 2009; 180: 982–988,
Tension–Time Index as a Predictor of Extubation Outcome in Ventilated Children
Harikumar G et al AJRCCM 2009; 180: 982–988,
The tension–time index (TTI) of the diaphragm (TTdi),
is a measure of the load capacity ratio of the diaphragm.
It is derived by relating the mean transdiaphragmatic pressure per breath (Pdi) to the maximal inspiratory transdiaphragmatic pressure (Pdimax) and the inspiratory time (Ti) to the total respiratory cycle time (Ttot).
Pdi/Pdimax = contractile capacity of diaphragm
Ti/Ttot = duration of respiratory muscle contraction

34. Harikumar G et al AJRCCM 2009; 180: 982–988,
Tension–Time Index as a Predictor of Extubation Outcome in Ventilated Children
Harikumar G et al AJRCCM 2009; 180: 982–988,

35. Harikumar G et al AJRCCM 2009; 180: 982–988,
Tension–Time Index as a Predictor of Extubation Outcome in Ventilated Children
Harikumar G et al AJRCCM 2009; 180: 982–988,

36. Harikumar G et al AJRCCM 2009; 180: 982–988,
Tension–Time Index as a Predictor of Extubation Outcome in Ventilated Children
Harikumar G et al AJRCCM 2009; 180: 982–988,

37. Adrienne G. Randolph et al. JAMA 2002;288(20):2561-2568
Sedation?
Adrienne G. Randolph et al. JAMA 2002;288(20):

38. 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

39. 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.

40. 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.

41. 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 RR 0.48; 95% CI 0.19 to for reintubation
(n = 1953) RR 0.47; 95% CI 0.22 to 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

42. 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

43. Extubation Criteria
Neurologic
Cardiovascular
Pulmonary

44. 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.

45. 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.

46. Pulmonary Patient should have a patent airway.
Pulmonary compliance and resistance should be near normal.
Patient should have “normal” blood gas and work-of-breathing 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

47. Conclusions: Weaning Readiness and Extubation Criteria
Ability to protect upper airway
Effective cough
Alertness
Improving clinical condition
Adequate lumen of trachea and larynx
“Leak test” during airway pressurization

48. 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.

49. 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
When is a patient ready to be extubated? First, they must be able to protect their airway. They should have an acceptable SaO2 on an FiO2 of no more than They should be breathing at a comfortable rate with a set ventilator rate of 5-8. Patients may be trialed on just pressure support/CPAP to make sure they are generating an adequate spontaneous minute ventilation. The amount of pressure support should be just enough to compensate for the added work of breathing imposed by the vent and ETT. The PEEP should be at 5 mmH2O.
If these are the circumstances, then the patient is ready for an attempt at extubation and their time on mechanical ventilation (and this presentation) has come to an end.