Weaning ventilator

WEANING VENTILATOR AND EXTUBATION:
STRATEGIES ON
SPONTANEOUS BREATHING TRIAL
FACEBOOK: HAPPY FRIDAY KNIGHT
9TH APRIL, 2020

BACK TO THE BASIC…
• Indications for intubation
• Indications for mechanical ventilation
• Weaning ventilator strategies
• Extubation
• Journal club: Pressure support VS T-piece during SBT on successful
extubation

INDICATIONS FOR INTUBATION: 4P
• Airway protection
• Assist ventilation (positive pressure)
• Prevent aspiration
• Suction secretion (pulmonary toilet)
http://medinfo2.psu.ac.th/anesth/education/intubation.html

INDICATIONS FOR MECHANICAL VENTILATION
• Patients unable to oxygenate without high FiO2 or CPAP
• Patients unable to do the work of breathing without mechanical
ventilation
Wilson WC, Grande CM, Hoyt DB. Trauma critical care. New York: Informa Healthcare, 2007.

Wilson WC, Grande CM, Hoyt DB. Trauma critical care.
New York: Informa Healthcare, 2007.
Davidson C, Treacher D. Respiratory Critical Care. London:
Arnolds, 2002.

WEANING VENTILATION STRATEGIES
1. Clinically stable:
• Central nervous system: normal CNS function, no sedation
• Cardiovascular system: hemodynamically stable
• Respiratory system: FiO2 0.4, PEEP 5 cmH2O, O2 sat > 92:
2. Spontaneous breathing trial (SBT)
3. Assess weaning parameter: rapid shallow breathing index (RSBI)
4. Assess extubation parameter: cuff leak test
5. extubation
Davidson C, Treacher D. Respiratory Critical Care. London: Arnolds, 2002.

WEANING VENTILATION STRATEGIES: SBT
• T-piece 2 h
• SIMV mode
• PSV mode: reduce PS until 5 - 8 cmH2O

WEANING VENTILATION STRATEGIES: RSBI
• RSBI = RR (bpm) / tidal volume (L)
• RSBI < 100-105 b/L predicts successful extubation (accuracy 85%)

EXTUBATION STRATEGIES
• Assess risk factors for postextubation stridor: airway edema, vocal
cords ulcer and cyst, RLN injury
• evaluation of periglottic swelling:
• Cuff-leak test
• Fiberoptic bronchoscopy
• Imaging study: laryngeal ultrasound

EXTUBATION STRATEGIES: CUFF-LEAK TEST
• ATS recommend cuff-leak test in high risk of postextubation stridor
• if failed, administer systemic steroids for at least 4 hours before
extubation
• Positive cuff-leak test is defined by < 110 ml of different between
exhaled volume
• before cuff deflation
• After cuff deflation
Cuff Leak Test for the Diagnosis of Post-Extubation Stridor: A Multicenter Evaluation Study. Journal of intensive care medicine. 2019: 34(5):391-
396.

JAMA June 11, 2019 Volume 321, Number

INTRODUCTION
• Daily screening of respiratory function by SBT decreases ventilation
duration
• After SBT and extubation, 10 – 25% require reintubation  higher
morbidity
• Most common modes of SBT are T-piece and PSV, 30 minutes to 2 hours
• No evidence: which one has a higher successful extubation rate
• This study compared between:
• More demanding T-piece for 2 hour
• Less demanding PSV 8 cmH2O for 30 minutes

METHODS
• From January 2016 through April 2017
• 18 Spanish intensive care units: multicenter randomized clinical
trial
• Approved by ethic committee of each hospital
• All patients were informed consent

METHODS
• Inclusion criteria:
• Patients at 18 years or older
• Undergoing mechanical ventilation at least 24 hours
• Fulfilled weaning criteria
• Exclusion criteria:
• Patients with tracheostomies
• Patients with do-not-reintubate orders

METHODS: WEANING CRITERIA
• Improvement of condition leading to intubation
• Hemodynamically stable: SBP 90-160 mmHg, HR < 140/min, no or low
dose vasopressors
• GCS ≥ 13
• Respiratory stability: O2sat > 90%, FiO2 ≤ 0.4, RR < 35/min,
spontaneous TV > 5 ml/kg, RR/TV < 100 beat/L, maximal Pi > 15 cmH2O
• Noncopious secretion: < 3 aspiration in last 8 hours

METHODS: RANDOMIZATION
• 1:1 ratio
• means of tables of computer-generated random numbers in
blinded blocks of 4 patients for each center.
• A central administrator who was not involved in the analyses used
an opaque envelope to allocate patients to receive one of the two
treatments
• The intervention was not blinded for the investigators or attending
physicians

METHODS: INTERVENTIONS
• Before randomization, physicians decide on extubation strategy
(whether to reconnect the patient to the ventilator for 1 hour before
extubation and whether to administer noninvasive ventilation or high-
flow nasal cannula after extubation)
• Patients randomized to
• Highly demand 2-hr T-piece
• Less demand PSV 8 cmH2O and PEEP 0
• Patients were extubated after successful SBT
• No ABG was required but if so, the results were recorded

• Physicians record dyspnea using Borg dyspnea scale
• 0 – 10
• 0 = no dyspnea
• 10 = maximal dyspnea
• Ask at the beginning and end of SBT, and without ventilator

• If not tolerate SBT  back to ventilator with these failure criteria:
• agitation, anxiety
• low level of consciousness(Glasgow Coma Scale score <13)
• respiratory rate higher than 35/min and/or use of accessory muscles
• oxygen saturation by pulse oximetry less than 90% with FiO2 higher than 0.5
• heart rate higher than 140/min or greater than a 20% increase from baseline
• systolic blood pressure lower than 90 mm Hg
• development of arrhythmia

• Additional SBTs were not protocolized, and mode and duration were left to the discretion of
attending teams
• Respiratory failure within 72 hours of extubation was defined as the occurrence of at least 1
of the following:
• respiratory acidosis with pH lower than 7.32 and PaCO2 higher than 45 mm Hg
• oxygen saturation less than 90% with FiO2 higher than 0.5
• respiratory rate higher than 35/min
• low level of consciousness (Glasgow Coma Scale score <13)
• severe agitation
• clinical signs of respiratory fatigue.

• Treatment of postextubation respiratory failure was not protocolized
• When noninvasive ventilation was used, duration, maximum inspiratory
and expiratory pressures, and maximum FiO2 were recorded
• When respiratory failure was treated with a high flow nasal cannula,
duration, maximum flow, and maximum FiO2 were recorded
• Patients needing reintubation within 72 hours were NOT
randomized again for weaning, but the need for tracheostomy and the
date of final liberation from mechanical ventilation were registered

METHODS: OUTCOMES
• primary outcome: successful extubation  free of invasive
mechanical ventilation 72 hours after the first SBT
• Secondary outcomes:
• rate of reintubation
• ICU and hospital lengths of stay
• hospital and 90-day mortality

METHODS: OUTCOMES
• Exploratory outcomes:
• time to reintubation and reasons for reintubation
• Incidence of tracheostomy
• Use of noninvasive ventilation and high-flow nasal cannula as
prophylaxis against postextubation respiratory failure and to treat it.

METHODS: OUTCOMES
• Post hoc outcomes:
• ICU mortality
• Borg Dyspnea Scale score at the end of the SBT
• patients’ confidence in their ability to breathe without the ventilator
• arterial blood analysis after successful SBT

METHODS: STATISTICAL ANALYSIS
• a successful extubation rate of 75% and an absolute increase in successful
extubation of 7% were expected  required sample for an α=.05 and a power
of 80% was estimated to be 540 patients in each group
• Using intention-to-treat principle with no exclusion after randomization
• Patients extubated outside of protocol were analyzed as having a failed SBT
• No participants were excluded from main or secondary analyses because of
missing or incomplete data.
• Reintubation was recorded only among patients who completed the trial

• Categorical variables are presented as absolute and relative
frequencies.
• Continuous variables are summarized as medians and interquartile
ranges (IQRs) for nonnormal distributions
• The Mann-Whitney U was used for nonparametric continuous variables
• To compare categorical variables, the 2χ test was used, except when
expected frequencies in contingency tables were less than 5, in which
case the Fisher exact test or the Monte Carlo method was used

• Time-to-event outcomes were analyzed with Kaplan Meier curves and compared by
log-rank test
• For the time-to event outcome of 72-hour successful extubation
• deaths occurring before 72 hours were introduced in the survival analysis as
censored data
• Event or censored times for all patients were calculated from the time of
randomization.
• Crude hazard ratios and 95% confidence intervals were calculated using a univariable
Cox proportional regression model to estimate the effect size of randomization group
• Proportionality of hazards was verified by examining Schoenfeld residual plots

• A post hoc random-effects multilevel logistic regression
model was used to determine variables associatedwith 72-hour
successful extubation, taking into account the effect of hospital
• Patient characteristics that were associated with 72-hour
successful extubation in the bivariable analysis were introduced in
the random-effects multilevel logistic regression model as first-
level variables andhospital as a second-level variable (random
effect)

• Odds ratios (ORs) and median ORs with 95% confidence intervals were
used to measure the association between each covariate and 72-hour
successful extubation.
• The median OR is a measure of the variation between rates of 72-hour
successful extubation at different hospitals that is unexplained by the
modeled risk factors  defined as the median of the set of ORs that
could be obtained by comparing 2 patients with identical patient-level
characteristics from 2 randomly chosen hospitals

• Covariates were introduced in the random-effects multilevel logistic
regression model using a researcher-controlled backward exclusion
strategy
• Post hoc analyses were performed for primary, secondary, exploratory,
and post hoc outcomes among the following populations:
• patients extubated after the first SBT
• patients extubated outside of protocol
• patients treated per protocol
• several subgroups defined by baseline demographic characteristics

• Effect sizes were evaluated by computing absolute risk differences with 95% confidence
intervals for binary outcomes and differences in means with 95% confidence intervals for
continuous outcomes.
• Figures were plotted for unadjusted risk ratios and 95% confidence intervals in the subgroup
analysis by
• age
• days of mechanical ventilation
• APACHE II score
• Chronic obstructive pulmonary disease (COPD)
• medical, surgical, or trauma admission
• No tests for interaction were conducted for the subgroup analyses

• A 2-sided α=.05 was considered statistically significant
• Data were analyzed using SPSS version 22(IBM Corp) and Stata
version 14 (StataCorp)
• Subgroup analysis graphs were generated using R version 3.5.2 (R
Foundation for Statistical Computing)
• There was no adjustment for multiple comparisons
• Results of the subgroup analyses and the analyses for secondary and
exploratory outcomes should be interpreted as exploratory

• No patient loss follow up
DEMOGRAPHICS: NO
DIFFERENCE

THE KAPLAN-MEIER
CURVES SHOW A
SIGNIFICANT
DIFFERENCE,
WITH A HIGHER
SUCCESSFUL
EXTUBATION RATE IN
THE PSV GROUP
(HAZARD RATIO,
1.54; 95% CI, 1.19-
1.97; P < .001])

Reasons for reintubation were not significantly different in the 2 groups

• In this RCT: PSV group results in:
• Higher rate of successful extubation
• The higher rate was related to more patients being extubated after the
PSV-SBT
• suggesting that a less demanding SBT better allows critically ill patients to
demonstrated their ability to sustain breathing
DISCUSSION

• A recent meta-analysis concluded that breathing through
a T piece requires the same amount of work as breathing after
extubation
• the authors recommended that SBTs should be performed with T
pieces because this approach better reflects the physiologic
conditions after extubation
• Physicians may be concerned that patients with low PSV and PEEP
could develop RS failure after extubation
DISCUSSION

• The current study found that the T-piece SBT was less
well tolerated than the PSV SBT, although the work of breathing
with the T piece may have been similar to breathing spontaneously
• But reintubation rate was not significantly different in the 2 groups
• No respiratory failure was observed after extubation from PSV
• incidence of cardiac arrest was very low and higher in the T-piece
group
DISCUSSION

• Vallverdu et al: 64% of T-piece SBT failed SBT in first 30 minutes
• Liang et al: identify characteristics of patients who failed SBT:
• older
• more cardiopulmonary disease
• spent more time receiving mechanical ventilation before the SBT
• undergone more previous SBTs
• These patients may need longer SBT  what about 30 minutes?
DISCUSSION

• In the present study: 30 minutes of PSV-SBT was enough to
check patients’ ability to breathe without increasing the rates
of post extubation respiratory failure and reintubation
• Self-extubation during the SBT was more common in the T-piece
group: tolerance of 30-min PSV is better than 30-min T-piece but
latter group received longer MV
DISCUSSION

• 2-hr T-piece and 2-hr PSV:
• Matic et al: Higher rate of successful extubation in PSV group
• Ezingeard et al: some patients can’t tolerate T-piece but PSV is okay
without difference on reintubation rate
• These result in T-piece is not the best way to check patients’ ability
to breathe
DISCUSSION

• In this study:
• Reintubation rate: no difference
• Logistic regression analysis showed that the 30-minute PSV
SBT was associated with successful extubation
• Extubation failure associated with longer MV and COPD
• Hospital mortality and 90-day mortality: significantly higher in the T-piece
group but cannot be explained by reintubation rate, days of MV after
failed SBT, APACHE II, or hospital LOS
DISCUSSION

• No protocol for prophylactic use of noninvasive ventilation and
high-flow nasal cannula after extubation  no conclusion about
the use of NIV and high flow nasal cannula for postextubation
respiratory failure
• Patients extubated outside of protocol could be expected to
influence the main results, but the sensitivity analysis ruled out
such bias
• Investigators and attending physicians were not blinded
LIMITATIONS

• Among mechanically ventilated patients, an SBT consisting of
30 minutes of PSV, compared with 2 hours of T-piece ventilation,
led to significantly higher rates of successful extubation.
• These findings support the use of a shorter, less demanding
ventilation strategy for SBTs
CONCLUSION

CRITICAL APPRAISAL
• CASP checklist: 11 questions on
• Are the results of the study valid?
• What are the results?
• Will the results help locally?

DID THE TRIAL ADDRESS A CLEARLY FOCUSED ISSUE?
• Yes
• PICO:
• P: patients who have met weaning ventilator criteria
• I: 30 min PSV-SBT
• C: 2 hr T-piece-SBT
• O: successful extubation

WAS THE ASSIGNMENT OF PATIENTS TO TREATMENTS
RANDOMISED?
• Yes, block of 4
• But investigators and attending physicians were not blinded

WERE ALL OF THE PATIENTS WHO ENTERED THE TRIAL
PROPERLY ACCOUNTED FOR AT ITS CONCLUSION?
• Yes
• No patients loss follow up

WERE PATIENTS, HEALTH WORKERS AND STUDY
PERSONNEL ‘BLIND’ TO TREATMENT?
• No

WERE THE GROUPS SIMILAR AT THE START OF THE
TRIAL
• Yes

ASIDE FROM THE EXPERIMENTAL INTERVENTION,
WERE THE GROUPS TREATED EQUALLY?
• Can’t tell due to no protocol after extubation

HOW LARGE WAS THE TREATMENT EFFECT?
• Appropriate outcomes measured
• Clearly specified primary outcome
• Large effect

HOW PRECISE WAS THE ESTIMATE OF THE
TREATMENT EFFECT?
• Besides no extubation strategy protocol, it was very precise

CAN THE RESULTS BE APPLIED TO THE LOCAL
POPULATION, OR IN YOUR CONTEXT?
• Yes
• The participants affect general population

WERE ALL CLINICALLY IMPORTANT OUTCOMES
CONSIDERED?
• Yes

ARE THE BENEFITS WORTH THE HARMS AND COSTS?
• Yes

MY OPINION
• Very good
• Borg dyspnea scale is subjective
• Demographic: no neurosurgical patients
• T-piece disadvantages
• Require extra equipment
• Require disconnection from the ventilator: no intrinsic monitor (ex: apnea
monitoring) introduces risk and chance for medical error

Weaning ventilator

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