Journal meeting weaning prediction

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Journal meeting--weaning prediction

• Date 12/20
• ??? ???
• ??? ?????

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Extubation failure magnitude of the problem,
impact on outcomes, and prevention

• Rothaar, Robert C. MD Epstein, Scott K. MD, FCCP
  
• Current opinion in critical care
• Volume 9(1)   February 2003   
• pp 59-66

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Causes of extubation failure

• Extubation failure is usually defined as the need
  for reinstitution of ventilatory support within
  24 to 72 hours
• traditional monitoring of a SBT using
  respiratory rate, oxygen saturation, blood
  pressure, heart rate, and blood gases is not
  sufficiently sensitive to detect early signs of
  loadcapacity imbalance

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Causes of extubation failure
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Causes of extubation failure

• Risk factors for glottic or subglottic narrowing
  include excessive cuff pressure, traumatic
  intubation, prolonged duration of intubation,
  tracheal infection, and female gender
• postextubation WOB may equal or actually exceed
  that seen with T-piece breathing

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• Swallowing dysfunction, with increased risk of
  aspiration, is common in extubated patients the
  incidence exceeds 50 among patients intubated
  for 48 hours or more

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• The prevalence of extubation failure ranges from
  2 to 25 depending on the population studied and
  the time frame (2472 h) included for analysis
• only 5 of cardiothoracic, general surgical, and
  trauma patients ultimately require reintubation

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• ICU physician staffing and nurse-to-patient
  ratios have been shown to influence reintubation
  rates in patients with esophageal resection and
  abdominal aortic surgery

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• Most investigators use 1- to 2-hour spontaneous
  (T-piece) breathing trials, whereas others use
  pressure support or intermittent mandatory
  ventilation weaning trials lasting 2 to 24 hours
  
• Prospective data are now available both for
  T-piece and pressure support modes, demonstrating
  that patients randomized to an initial trial of
  either 30 minutes' or 120 minutes' duration
  experience no difference in reintubation rates

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• Randomized, controlled clinical trials comparing
  various combinations of T-piece ventilation,
  pressure support ventilation, intermittent
  mandatory ventilation, continuous positive airway
  pressure, and automatic tube compensation
  demonstrate no difference in extubation failure
  rates

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Factors associated with increased risk of
extubation failure
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Impact on outcomes

• The outcome for patients who tolerate extubation
  for a minimum of 24 to 72 hours is generally
  favorable, with hospital mortality rates below 10
  to 15
• In contrast, univariate analyses have shown that
  the mortality rate associated with extubation
  failure ranges from 2.5 to 10 times that
  experienced by successfully extubated patients

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• The cause of extubation failure is also a
  determinant of outcome mortality rates are
  lowest when reintubation must be performed as a
  result of upper airway obstruction, aspiration,
  or excess pulmonary secretions

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Prevention

• The decision to extubate cannot be based solely
  on routine screening criteria for weaning (eg,
  adequate oxygenation, hemodynamic stability) ?
  40 of the patients who meet these criteria
  require reintubation
• Additional information is gained by successful
  completion of a SBT because 80 to 95 of patients
  who pass a trial will also tolerate extubation

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Prevention
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Prediction of extubation outcome using weaning
parameters
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Prediction of extubation outcome using weaning
parameters

• Meade et al. concluded that these indices have
  only limited utility in predicting weaning
  outcome, even less accurate predictors of
  extubation outcome
• The most accurate and well-studied test is the
  frequencytidal volume ratio ?But still rarely
  leads to moderate or large changes in the
  probability of success or failure

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Prediction of extubation outcome using weaning
parameters

• The sustained maximal inspiratory pressure was
  significantly lower in those who failed
  extubation ?threshold value of 57.5 pressure time
  units perfectly separated the two groups
• A limitation of this technique is that it
  requires patients to be able to follow commands

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• Levy et al. found that an elevated WOB (gt0.8 J/L)
  was not associated with extubation failure among
  patients tolerating a SBT
• a higher gastricarterial carbon dioxide
  gradient, determined by gas tonometry, was found
  in patients who failed extubation

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• Airway occlusion pressure measured at 100
  milliseconds (P100 or P0.1) --Hilbert et al.
  demonstrated that P100, measured immediately
  after extubation (via face mask in pressure
  support ventilation mode) ?predict which patients
  with chronic obstructive pulmonary disease
  subsequently developed postextubation respiratory
  failure

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• Comprehensive analysis of the breathing pattern
  during SBT may predict extubation failure? A
  prospective trial of 52 patients undergoing SBT
  revealed that an irregular breathing pattern was
  associated with an increased risk of extubation
  failure

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Prediction of extubation outcome using parameters
that assess upper airway patency

• Upper airway obstruction may increase the WOB
  after endotracheal tube removal
• The absence of an audible air leak after
  deflation of the endotracheal tube balloon
  (qualitative cuff leak test) has been associated
  with an increased risk of postextubation stridor
  ?subjective
• An objective assessment involves the indirect
  measurement of the volume of gas escaping around
  the tube during balloon deflation (quantitative
  cuff leak test).? less than 110 mL predicted the
  development of postextubation stridor

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Prediction of extubation outcome using parameters
that assess upper airway patency

• fewer than 50 of patients with postextubation
  stridor require reintubation
• The results of a meta-analysis of randomized,
  controlled trials in children showed that routine
  preextubation corticosteroid administration
  reduced postextubation stridor but did not
  clearly reduce reintubation rates

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Prediction of extubation outcome using parameters
that measure the capacity for airway protection

• cough strength,
• pharyngeal muscle competency,
• secretion volume,
• mental status

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Prediction of extubation outcome using parameters
that measure the capacity for airway protection

• Effective cough --adequate expiratory muscle
  function
• -- peak cough flow rates
• -- maximal expiratory pressure
• Bach and Saporto studied patients with
  neuromuscular causes for acute respiratory
  failure ? unsuccessful extubation or tracheotomy
  decannulation was likely with peak cough flow
  rates less than 160 L/min

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Prediction of extubation outcome using parameters
that measure the capacity for airway protection

• The relative risk of extubation failure increases
  for patients requiring endotracheal suctioning
  more frequently than every 2 hours
• A sawtooth pattern on the flowvolume curve
  provides a qualitative indication of the presence
  of airway secretions

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Prediction of extubation outcome using parameters
that measure the capacity for airway protection

• Brain dysfunction ?hypoventilation
• Depressed mental status (Glasgow Coma Scale score
  lt 8) has been shown to be a variable predictor
  of extubation outcome, with two studies in
  brain-injured patients arriving at conflicting
  conclusions

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• The best predictor of extubation success at
  present is
• --successful completion of a SBT coupled with an
  adequate cough,
• --absence of excessive respiratory secretions
  (eg, airway requires suctioning less frequently
  than every 2 hours),
• -- a patent upper airway.

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Gastric intramucosal pH and intraluminal Pco2
during weaning from mechanical ventilation

• Hurtado, F. Javier MD, etc.
• Critical Care Medicine
• Volume29(1)  January 2001  pp 70-76

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Introduction

• Along with the increment in the respiratory
  muscles blood flow, a redistribution of cardiac
  output has been described in different pathologic
  conditions.
• during low cardiac output states, septic shock,
  and hypoxemia, the blood flow to the skin,
  kidneys, and the splanchnic area decreases to
  favor the respiratory muscles perfusion

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• monitoring gut perfusion could provide useful
  information when spontaneous ventilation and the
  work of breathing are reassumed

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MATERIALS AND METHODS

• Study Population
• 19 critical ill patients
• Patients who were on mechanical ventilation for
  less than 24 hrs were excluded
• A written informed consent was obtained from the
  family or the patient when possible

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Study Protocol

• The decision to initiate weaning was made by the
  clinical staff
• Criteria resolution or improvement of the
  pulmonary disease, cardiovascular stability,
  absence of electrolyte or acid-base disorders,
  absence of fever, 12 hrs free from sedation, Pao2
  gt70 torr with an Fio2 lt0.50, vital capacity (VC)
  gt10 mL/kg, maximal inspiratory pressure (MIP) gt20
  cm H2O, and dynamic compliance gt20 mL/cm H2O

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• two different time points
• -The first or initial evaluation was done at the
  beginning of a weaning protocol. The measurements
  were taken at least 30 mins after the selected
  weaning mode was start
• -The second or final evaluation was done once the
  minimum planned level of partial mechanical
  support was reached

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• 10 patients were randomly assigned to SIMVPEEP
  and 9 to CPAPPSV
• SIMV?initiated at eight cycles per minute and
  PEEP levels lt5 cm H2O
• PSV and CPAP ?initial settings were 18 and 5 cm
  H2O
• The duration of the weaning process was managed
  by the clinical staff according to their usual
  practice

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• the time spent to discontinue the mechanical
  support lasted from 3 to 72 hrs
• SIMV was reduced in steps of 1-2 mandatory cycles
  until a target value of 2
• PSV was reduced in steps of 2 cm H2O until a
  target value of 8
• ?then extubated

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• Weaning failure?The patients who were not able to
  complete the weaning process reintubated and
  mechanically ventilated within 24 hrs after
  extubation
• Weaning failure RR gt 35 /min , increase in
  Paco2 gt10 torr from the initial value, Pao2 lt55
  torr at a Fio2 gt0.45, dyspnea and diaphoresis,
  HRgt 140 or 30 increase of the initial value,
  chest pain, ventricular arrhythmias, arterial pH
  lt7.28, or consciousness deterioration.

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Measurement and Calculations

• Simultaneous curves of respiratory airway flow,
  airway pressure, and tidal volume
• the breathing pattern and the central control of
  breathing were evaluated after a 30-min period of
  spontaneous T-tube ventilation
• The respiratory airway pressure was obtained with
  a differential pressure transducer

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• The respiratory airway flow was measured with a
  pneumotachograph connected to an airway flow
  transducer
• the tidal volume was obtained using a respiratory
  integrator
• The central control of breathing during
  spontaneous ventilation was evaluated by
  measuring or calculating the following variables
  inspiratory time, expiratory time, total
  respiratory time, tidal volume, RR, inspiratory
  duty cycle, mouth occlusion pressure, mean
  inspiratory flow, and effective inspiratory
  impedance (mouth occlusion pressure/mean
  inspiratory flow)

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Main results

• 11 patients were successfully extubated and 8t
  failed.
• The patients who failed showed higher values of
  mouth occlusion pressure, respiratory rate, and
  effective inspiratory impedance (mouth occlusion
  pressure/mean inspiratory flow).
• The intramucosal pH was initially 7.19 0.22 and
  decreased to 7.10 0.16 during the weaning
  process in patients who failed (p lt .05).
• the intramucosal pH showed a nonsignificant
  change from 7.36 0.07 to 7.32 0.07 in the
  patients who were successfully extubated.

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• The intramucosal pH was statistically different
  when both groups were compared during the initial
  and the final evaluations (p lt .05).
• the sensitivity and specificity to predict
  weaning failure when the intramucosal pH was
  lt7.30 were 0.88 (95 confidence interval CI,
  0.661) .
• The gastric intraluminal Pco2 was higher in
  patients who failed (p lt .05). When gastric
  intraluminal Pco2 was gt40 torr during the
  initial evaluation, weaning failure occurred with
  a sensitivity of 1 (95 CI, 0.311) an

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Conclusion

• A low gastric intramucosal pH or an increase in
  gastric intraluminal Pco2 were associated with
  weaning failure
• These changes were associated with a higher
  respiratory rate, mouth occlusion pressure, and
  effective inspiratory impedance