Difficult Weaning
An approach
Ram E. Rajagopalan,
MBBS, AB (Int Med) AB (Crit Care)
Head, Department of Critical Care Medicine
SUNDARAM MEDICAL FOUNDATION
Chennai
Goals of this talk






To define “difficult” wean
Evaluate the pathophysiology of
ventilator dependence
Identify difficult-to-wean groups
Consider a systematic approach to
minimising reversible causes of
ventilator dependence
Consider methods to enhance wean
Not an evaluation of long-term
ventilator dependence
What is weaning?

“Discontinuation”; the apolitical term
It starts when the doctor decides that the
disease has resolved & patient is
“ready” for K support

Objective “readiness” criteria:

 Adequate
Chest 2001; 120:375S–395S
oxygenation (P/F > 200, PEEP<5)
 Stable CVS (BP, ’pressors, HR)
 Adequate cough reflex
 Adequate mentation (GCS>12)
 ? Rapid-shallow breathing index <100
Initial Trial of Discontinuation
When patients are “ready” to wean, a spontaneous breathing
trial (SBT; using a T-piece for 2 hours) is tolerated by most.
Abbreviation to a 30-min SBT
reduces ICU & Hospital LOS*
AJRCCM 1994; 150: 896-903
N Engl J Med 1995; 332: 345-50
*AJRCCM 1999;159:512-518
Re-intubation rates average~15%
All attempts
are
NOT likely
to succeed!!
Spanish Collaborative Trial
Approach to the failed SBT
N Engl J Med 1995;332; 345-50.
Summary Approach
The Failed SBT
AJRCCM 1994; 150: 896-903
N Engl J Med 1995; 332; 345-50.

After return to MV, patients should
undergo a daily 2-hour T-piece trial

PS(7 cm H20) + PEEP is acceptable

IMV should NOT be used
Defining “Difficult-to-wean”
“Ready to wean” Consensus Definitions*
Initial T-piece
SBT
“Difficult Wean”
In acute cases ~25-40 % &
need ~ 7days & 3 SBTs
2/3 extubated
“Prolonged
Wean”
(15%
reintubation)
Up to 14 days (~10%)
1/3 fail
Daily SBT/
Pres. Sup
AJRCCM 2001; 164: 186-7
* Chest 2005; 128: 3937-54
* Eur Respir J 2007; 29: 1033-56
“Prolonged Mechanical
Ventilation” (PMV)
is the need of MV >21 days
for >6 hours
/day; 3-7%
85-90%
weaned
JinMortality
14 days/ Resource use
“Prolonged Ventilation”
Frequency
Re-intubation
Mortality
AJRCCM; 2013: 187; 1294-1302
Weaning Difficulty &
Outcome
■Simple ■Difficult ■Prolonged
Pathophysiology
Rapid shallow breathing
N Engl J Med 2001; 344: 1986-96
Chest 2001; 120:375S–395S
? Response to inadequate drive / breath
? Inappropriate response to increased load
Pathophysiology


Rapid shallow breathing (K RR D in COPD)
Increased respiratory load
 Higher
PEEPi
 Higher Elastance
 Higher Resistance





* AJRCCM 2000;161: 1115–23.

Maintained neuromuscular drive (P0.1)*
Reduced muscle strength (Pdi max)*
Imbalance between load & capacity
Higher PCO2
Similar in COPD and post-CTS*
Not predictable by baseline mechanics
Effect of weaning on CV
Pulmonary
hypertension
RV Failure
Spontaneous breathing
K intrathoracic pressure
(J insp. Swings)
J Venous return
Hypoxia
Venous
desaturation
Anesthesiology 1988; 69:171–179
AJRCCM 1998;158:1763–1769.
Chest 2001; 120:375S–395S
Unmasks LV
Diastolic Dysfunction
Pulmonary edema
Reversible Factors
A (c)heck list !!
From:
Chest 1998; 114: 886-901
Improve neuromuscular competence
Treat Sepsis
Nutritional support without overfeeding
Replace K, Mg, P to normal
Assure periods of respiratory muscle rest;
avoid exhausting breathing trials
Limit use of neuromuscular blocking drugs
Consider stopping aminoglycoside therapy
Consider
Neurological disease
Hypothyroidism
Over sedation
Critical illness myopathy / polyneuropathy
Steroid myopathy
Investigational / unproven
Anabolic Steroids
Growth Hormone
Aminophylline
Reduce respiratory load
Resistance
Bronchodilators
Corticosteroids
Removal of airway secretions
Treatment of upper airway/ET obstruction
Compliance
Treat Pneumonia
Treat pulmonary oedema
Reduce intrinsic PEEP
Drain large pleural effusions
Evacuate pneumothoraces
Treat Ileus
Decompress abdominal distension
Ve
Treat sepsis
Antipyretics
Avoid overfeeding
Correct Metabolic acidosis
Reduce intrinsic PEEP
Bronchodilators
Maintain least PEEP possible
Resuscitate shock and hypovolemia
Identify and treat pulmonary embolism
I think you
are stupid if you
still want to read
the whole list!
Risk Factors:
Influence of Aetiology
COPD
NEURO
Ac. Resp. Failure
f/Vt <100; MIP < -20
2-hour T-piece trial
39%
weaned
AJRCCM 1998; 158:1855-62.
59%
weaned
62%
weaned
Influence of Aetiology
COPD
NEURO
Ac. Resp. Failure
f/Vt <100; MIP < -20
2-hour T-piece trial
39%
weaned
AJRCCM 1998; 158:1855-62.
59%
weaned
36%
re-intubated
Low GCS
62%
weaned
9%
re-intubated
Weaning Risk; Co-morbidity
None
57%
COPD
None
43%
>1400 patients in 23 LTC facilities
Mean age =72 years
46%
High frequency of associated co-morbidity
COPD, CAD & Neurological Dx
CAD / CHF
54%
Renal failure; 1.9X probability of failed wean
None
80%
GCS <8 ; 6.5X probability of weaning failure
Neuro-
AJRCCM 2003; 167: A458
Chest 2005; 128: 3937-54
muscular
20%
Other Risk Factors
Age >65; comorbidity
APACHE Score
Neurological failure
COPD / J Secretions / Feeding
(CO2 retention at SBT)
Respiratory failure of Cardiac Origin
(J BNP / K ScvO2 at wean)
Critical Illness Polyneuropathy
Nutrition
Neurological Function

Neurological drive is well preserved in
most difficult-to-wean patients

Drive may be suppressed by
 CVA
 Non-convulsive
seizures
 Electrolyte disturbance (Low Na)
 Medication (sedatives)
 Hypothyroidism (+ impairs muscle fn.)
Sedation: Daily Discontinuation
RCT;
128 adults
on ventilation
Routine
Sedation
Daily
d/c
“Wake-up” call
N Engl J Med 2000;342:1471-7.
PMV & Hypothyroidism
140 patients with
PMV (routine screen)
1 old hypothyroid
TSH h in 16 (12.1%)
TSH h+ K T3/ T4 = 4 (3%)
Clinical suspicion, BMI
are poor correlates.
Chest 2004; 126:1307 - 12
Hypothyroidism is a rare but
treatable cause of PMV
Predictors of Wean


Aetiology matters
COPD / ARF
 Duration
of ventilation
 Age
f
/ Vt ratio
 P0.1
 MIP

Neurology
 MIP
 MEP
AJRCCM 1998; 158:1855-62.
f
/ Vt . P0.1
Cardiovascular Reserve

Weaning causes significant changes in
LV & RV function

Consider occult coronary disease
 Beta

blockade?
Optimise function
 Weight
* AJRCCM 1992; 145: A522
loss associated with diuresis
correlates with wean in PMV*
 My bias towards nitrates
 Dobutamine unlikely to be beneficial
 Inodilators (enoximone) used
effectively in CVTS
Fluid Restriction (FACTT)
Achieved 7-day fluid balance of
-136+490 ml (conservative) vs. 6992+502 ml
K Pplat &
oxygenation index
________________________________________
Expected D in ’lytes
__________________________________________
2 day J vent-free
& ICU-free days
(p <0.001)
______________________________________________
No D in mortality
N Engl J Med 2006;354:2564-75
SvO2 monitoring in wean
Venous desaturation
was significantly K
in patients who fail
weaning (SBT)
AROC: 0.70 ± 0.08
AJRCCM 1998; 158: 1763-69
Critical Care 2010; 14: 211
PaOP and plasma protein conc. have value?
AROC= 0.93 ± 0.04
Weaning Failure
Basal measurement of E/E’ has been
validated as a marker of weaning failure
in multiple studies;
Lamia;
E/E’ >8.5 with E/A .0.95;
Sens 82% Spec 91%
ICM 2011; 37:1976-85
CCM 2009; 37: 1696-1701
Papanickolaou
E/E’ >7.8
Sens 79% Spec 100%
Weaning Failure &
Diastolic Dysfunction
68 unselected pts.
28 fail wean
Sensitivity
Weaning failure if:
Basal E/E’ >12.6
(AUC .75)
10 min E/E’
Basal E/E’
10min SBT E/E’ >14.5
(AUC .86)
Or
E’ <8 at baseline
Moschietto et al.
Critical Care 2012, 16:R81
1-specificity
Implications on Weaning
Identification prior to / early in SBT gives
room for preventive care
If identified; attention to fluid management
may enhance weanability
May identify a role for NIV / CPAP after
extubation
BNP- directed wean
RCT of BNP to guide fluid Rx (n=304)
BNP J with
failed SBT
(AROC 0.89 + 0.04)
Cut-off of 275 pg/ml
15% CAD
25% COPD
60% neither
Avg. P/F = 210
Questionable
incremental value*
AJRCCM 2012: 186; 1256-63
*Critical Care 2010; 14: 211
Larger -ve balance (-2.3L vs -0.1 L)
Wean time K; 42 hr. vs. 58 hr.
Respiratory Load



Remember: rapid shallow breathing is
effective for energy utilisation but
affects lung mechanics
Increased resistance and elasatance
occurs in most difficult weans
Minimising load is useful: Lower Ve
 Sepsis
 Fever
 Overfeeding
Nutrition & Respiratory Load
J CHO:FAT
OVERFEEDING
VCO2
LUNG DISEASE
COPD
PCO2
WEAN FROM VENTILATOR
Overfeeding & Respiratory Load
300
250
VCO2
250
200
200
150
150
100
100
C40 / F40
Chest 1992;102:551-5
C60 / F20
C75 / F5
1xREE
1.5xREE
2xREE
VCO2 is affected more by hypercaloric feeding
than by the carbohydrate: fat ratio
ARDSnet: W-3 Fatty Acids
JAMA 2011; 306: 1574-81
Motor Function


Muscle weakness may be a reversible
contributor to ventilator dependence
Identify & Rx: Electrolyte problems:
 Deficiency




of K, Mg, P
Identify: Critical Illness Polyneuropathy
Stop: neuromuscular blocking agents
Stop: aminoglycosides
Stop: steroids?
Hypophosphatemia
Causes are multifactorial
P repletion
improves
Pdi
Refeeding Syndrome
(associated hypo K and hypo Mg)
Respiratory Alkalosis /
correction of respiratory acidosis
Met. alkalosis causes smaller change
CCM 1989; 17: 1115-20
CC Clin 1991; 7: 201-14
Sucralfate
Used for stress ulcer prophylaxis
Critical Illness Polyneuropathy
In one study
96% of patients ventilated >7 days
Had EMG/ Biopsy evidence of neuro/myopathy
62% with similar findings in PMV
Sepsis may contribute to CIPN
Use of steroids, NMB agents of importance in
myopathy…..
Glycemic Control
The dose-response relationship:
70
60
% Riskk
50
40
80-110
30
110-150
>150
20
10
0
(Crit Care Med 2003; 31: 359-66)
oly
P
I
C
I
tion
a
mm
a
l
f
n
il
l Fa
a
n
e
eR
t
u
Ac
Despite recent
controversy on the
value of strict
glycaemic control in
medical patients
Effect on CIPN seems
consistent….
Chest 2007; 132: 268-78.
Cochr Databa of Sys. Rev. 2014,
DOI:10.1002/14651858.CD006832.
pub3.
Meta-analysis RR: 0.65 (95% CI; 0.55-0.77)
NIV: To Hasten Wean
p <0.01
24
25
NiPPV
In COPD patients;
60-day mortality &
nosocomial
pneumonia show
improving trends
Ann Int Med 1998; 128: 721-8
15
PS+/- CPAP
15
10
p 0.02
5
398
400
0
ICU LOS
300
Hours
Days
20
245
200
100
0
Duration of Ventilation
COPD: NIV weaning
p 0.10
28
30
25
p 0.06
20
NiPPV
% 15
10
8
PS+/- CPAP
5
25
0
20
60-day mortality
28
30
% 15
10
5
0
0
Nosocomial Pneumonia
Ann Int Med 1998; 128: 721-8
Chest 2001; 120: 438S-44S
Ferrer; AJRCCM 2003;168:70–76
NIV wean is NOT an established strategy in
ventilated patients with other aetiologies
NIV: To prevent Re-intubation
Effective
when used
prophylactically
in selected cases
post-extubation;
COPD
Elderly >65
High APACHE
APE as cause
J PCO2 at SBT
AJRCCM 2011; 184: 672-79
Sampath S,
ESICM abstract 2007
The use of NIV in patients extubated after
failing SBT has no value.
PS vs. T-piece in SBT
Pressure Support (7 cm H20)
The “spurious”* belief that work of
breathing J with an ETT and
K consistently on extubation
86%
14%
Extubated
Failed
T-piece for 2 hours
p = 0.02
78%
22%
AJRCCM 1997; 156: 459-46
*AJRCCM 2012; 185: 349-50
No difference in LOS, mortality.
63% of T-pieced and 70% of PS
patients remained extubated (NS)
PS vs. T-Piece in SBT
Wean with low PS may result in false
+ve SBT pass
In COPD & LVF where extubation is to
NIV prefer SBT on CPAP alone (over
low PS); may perform better
In all other cases T-piece is preferred to
estimate success more accurately
Tracheostomy?


Improved comfort of caregiver
(Doctor / nurse vs. patient)
Airway mechanics
 Less Resistance
 Increased turbulence

Chest 2001; 120:477S–481S
? benefit on wean duration
Is there evidence?
BMJ 2005; 330: 1243
5 RCT studies identified
406 patients
Bouderka 2004,
n=62
Dunham 1984,
n=74
Rodriguez 1990, n=106
Rumbak 2004,
n=120
Saffle 2002,
n=44
Defn.
5-6 d
3-4 d
1-7 d
<2 d
ASAP
Weaning From Ventilation
8.5 fewer days on ventilator
BMJ 2005; 330: 1243
No VAP or mortality difference
Recent Tracheostomy RCTs
Italian*
(Terragni et al)
TRACMAN**
Early
Late
Early
Late
N
Day of trache
% trached
209
7
69%
210
14
57%
455
4
92%
454
10
45%
Mortality
VAP
No difference
HR: 0.66; NS
No difference
N/A
ICU LOS
Ventilation duration
K; HR: 0.73 (0.55-0.97)
K; HR: 0.70 (0.56-0.87)
13 days; NS
N/A
*JAMA 2010; 303:1483-89
**JAMA 2013;309: 2121-29
Tracheostomy in India
Context-specific differences:
High rates of VAP
K compliance oral antisepsis with ETT
Trache may K VAP more than in the west
Very poor patient mobilization with ETT
Trache facilitates physiotherapy…….
Physical Therapy in ICU
104 patients
<72 hours since ICU admit
Expected ventilation >24 hrs
Control: 55;
Sedation interrupt
Activity per doctor’s order
Independent at discharge
49; Treatment
Sedation interrupt
Planned graded PT/OT
35%
59%
OR: 2.7 (1.2-6.1)
Ventilator-free days
21 days
23.5 days
p=0.05
Protocols:
(C)lean, Mean Guarantees
of Success?

Does the application of nurse/
respiratory care professional
directed weaning trial improve
outcome?

Removes uncertainty and
delays involved with
physician-centred decisions.
ears
neck
feet
Simple Wean by Protocol
300 patients randomised
Adjusted RR of extubation
with Protocol was
2.13 (95% CI = 1.55-2.92)
Re-intubation was less frequent:
4% vs. 10% (p 0.04)
Cost of ICU care was lower
(p 0.03)
Similar outcomes reported by Kollef et al.
N Engl J Med 1996; 335:1864-9.
(Crit Care Med 1997; 25: 567-74)
Protocols in difficult wean
Protocol
Weaned
13%
30%
COPD >15 days
ventilation
AJRCCM 2001;164: 225-30
70%
87%
Days
55 “protocol” weans
vs.
62 historical controls
Low quality evidence
Control
50
45
40
35
30
25
20
15
10
5
0
Protocol
Control
Ventilation
Hospital
Summary
Chest 2001; 120: 425S-437S

Care of the difficult-to-wean patient
consumes resources

Identification of high-risk groups can
allow better allocation of these
resources

Identification and correction of
reversible co-morbidity is essential to
enhance wean

Logical ventilatory strategies may
improve success