Slides accompanying the Lecture/Review Mechanical Ventilatory support series part V/V: Weaning and liberation from mechanical ventilatory support. For medical students and residents in Internal medicine. Contents are including rationale of weaning, predictors of weaning success and failure, methods of weaning, and detection and management of weaning failure
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Mvss part v weaning & liberation from mechanical ventilation
1. Mechanical Ventilatory Support Series
Part V:
Weaning & Liberation from Mechanical Ventilation
S a n t i S i l a i r a t a n a , M D
Division of Pulmonary Medicine, Department of Medicine,
Faculty of Medicine Vajira Hospital
Navamindradhiraj University
4. Ventilator Days and Survival Chance
Esteban A, Anzueto A, Frutos F, et al.
More ventilation days,
more deaths.
Day
Survival chance
Asthma
COPD
ARF
ARDS
5. Do patients need weaning?
19%
81%
Brochard L, Rauss A, Benito S, et al.
456 patients
were enrolled to study weaning methods
347 patients (81%)
were successfully extubated within 48 hr
9. Parameters Used in Prediction of Weaning Success
PaO
P: F ratio
PaO
A-a DO
Pi
FVC
PaCO
MV
TV
MVV
RR
P
V
C
C
RSBI CROP index
P
SWI
10. Predictors Based on Respiratory Physiology
PaO
P: F ratio
P
A-a DO
Pi
FVC
PaCO
MV
TV
MVV
RR
P
V C
C RSBI
CROP index
P
SWI
Oxygenation CombinedLoadStrengthDrive
11. Indicators of Muscle Performance
Parameter of Oxygenation Weaning Threshold
Pimax <-15 to -30 cm H2O
FVC >10-15 mL/kg
PaCO2 <50 mmHg
Minute Ventilation (MV) <10-15 L/min
Tidal volume (TV) >5 mL/kg
Maximum voluntary ventilation (MVV) >20 L/min
RR <35 breaths/min or >6 breaths/min
f/Vt ratio <105 breaths/min/L
Strength
Stamina
Ashfaq Hasan.
12. Respiratory Mechanics
Mechanical Indices Weaning Threshold
Dynamic compliance (Cdyn) >22 mL/cm H2O
Static compliance >33 mL/cm/H2O
Work of breathing 0.47 J/L or 33 J/min
Ashfaq Hasan.
13. Indices of Oxygenation
Parameter of Oxygenation Weaning Threshold
PaO2 (on FiO2 0.5 and PEEP ≤5 cm H2O) >60 mmHg
PaO2/FiO2 ratio (“PF”ratio) >200
PaO2/PAO2 ratio >0.35
Alveolo-arterial oxygen gradient (A-aDO2) <350 mmHg on FiO2 1.0
Shunt fraction (Qs/Qt ratio) 0.2 (<20% shunt)
Ashfaq Hasan.
14. Composite Indices
Composite Indices Weaning Threshold Failure Threshold
RSBI (f/Vt) ratio <105 breaths/min/mL >105 breaths/min/mL
CROP index >13 mL/breaths/min N/A
P0.1/Pmax ≤0.9 N/A
SWI <9/min >11/min
RSBI
CROP
SWI
Ashfaq Hasan.
16. Readiness to Wean
The cause of respiratory failure has improved
The patient is oxygenating adequately
The arterial pH is >7.25
The patient is ale to initiate an inspiratory effort
The patient is hemodynamically stable
No myocardial ischemia
18. Rate of Successful Weaning
Weaning technique
Relative rate of suscessful weaning
(95% CI)
P value
Once daily SBT vs SIMV 2.83 (1.36-5.89) <0.006
Once daily SBT vs PSV 2.05 (1.04-4.04) <0.04
Once daily SBT vs intermittent SBTs 1.24 (0.64-2.41) 0.54
SBT
Esteban, A, Frutos, F, Tobin, MJ, et al,
SIMV
PSV:
19. Assessment of Readiness to Wean
Clinical
assessment
Objective
measurements
Good heart:
HR ≤140 bpm
SBP 90-160 mmHg
No/minimal vasopressors
Good oxygenation:
SaO2 >90% on FiO2 ≤0.4
PEEP ≤8 mmHg
‘3 Cs’
Cough
Clean
Clear
Good
consciousness
Good pulmonary function:
RR ≤35 bpm
MIP ≤-20 to -25 cmH2O
VT >5 mL/kg
VC >10 mL/kg
f/Vt <105 br/min/L
No significant respiratory acidosis
Stable
metabolic status
21. Weaning with PSV
1 2 3 4 5 6
Record
Tidal volume
P peak
Set
Level of PS
80-85% of
P peak
Monitor
clinical signs
periodically
Gradual
decrease
PS 2 cmH2O
twice per day
PS 6-8 cmH2O
PEEP ≤5 cmH2O
T-piece trial
or
Extubation
22. Weaning with SIMV + PSV
1 2 3 4 5 6
Record
spontaneous
RR and P peak
Set SIMV rate
75-80% of
spontaneous rate
and PS 80-90% of
P peak
Monitor
clinical signs
periodically
Gradual
decrease
RR 1-2 bpm
twice per day
RR 0 bpm
Gradual
decrease
PS 2 cmH2O
twice per day
7 8
PS 6-8 cmH2O
PEEP ≤5 cmH2O
T-piece trial
or
Extubation
23. Modes of Weaning: Summary
SIMV with PSV
Progressive decrease
of SIMV rate
Progressive
decrease
of PSV
PSV
SB with PSV
SB with T-piece
SB without
PSV
Extubation
25. Weaning Failure
Either
the failure of
Spontaneous breathing trial
or
the need for reintubation within 48 h
following extubation
J-M. Boles et al.
26. Classification of Patients with Weaning Failure
Group/Category Description
Simple weaning Success at the first attempt
Difficult weaning
1-3 attempts of SBT
Up to 7 days from the first SBT
Prolonged weaning
>3 attempts
7 days of weaning after the first SBT
SBT
J-M. Boles et al.
37. Management of Weaning Failure
Rest
24 hours
Correct
the cause(s)
Retry
weaning
Retry
with gradual
modes
Tracheostomy
Long-term ventilation
38. Postextubation Laryngeal Edema: Risk
Normal
vocal cords
Vocal cord
edema
Age >60 years
Female
Duration of intubation ≥3 days
Severe disease (APACHE II, SAPS II score)
Large tube size
High cuff pressure
History of self-extubation/reintubation
Underlying DM, CKD, Liver disease
39. Postextubation Laryngeal Edema: Detection
Suction and clearing airway
Switch ventilator to VCV mode
Set tidal volume to be inspired (Vti)
Deflate ET tube cuff
Record tidal volume of expiration (Vte)
5-10 breaths to calculate mean values
Vti - Vte
>110 mL
associated with adequate
patency of the airway
(Specificity 99%)
40. Postextubation Laryngeal Edema: Management
All intubated patients
At risk:
• Female
• Longer duration of intubation
• High APACHE II, SAPS II score
• Large tube size
• High cuff pressure
• History of self-extubation
• Negative cuff leak test
Not at risk
Consider:
• Methylprednisolone 20 mg q 4 h 3-4
doses; at least 12 hr prior to
extubation attempt
• Place airway exchanger catheter
Extubation with
close observation
Consider discharge
Consider:
• Prednisolone 0.5 mg/kg
• Epinephrine 1 mg in NSS 5 mL NB
• Helium 40% + O2 60% inhalation
PES
• Re-intubation
• Continue
steroids
No improvement in 1 hr
No symptom
in 1 hr