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Paper text:
extubation failure ( the need for re - intubation ) is associated with increased intensive care unit and hospital mortality , increased length of stay in the intensive care unit and hospital , greater need for tracheostomy and for long - term acute care , and increased costs . underlying severity of illness , premorbid health status , and complications directly associated with re - intubation fail to explain the adverse outcomes seen with extubation failure . clinical deterioration between the time of extubation and the re - establishment of ventilatory support
the study reported by lee and coworkers   is one of a series of recent investigations examining whether corticosteroids can prevent postextubation upper airway obstruction ( uao ) , which is a common cause of extubation failure .
intubation and the endotracheal tube ( ett ) may cause laryngotracheal injury , resulting in inflammation , mucosal ulceration , edema , or granuloma formation .
this can lead to glottic or subglottic narrowing , which manifests as stridor , respiratory distress , or respiratory failure after removal of the ett .
factors associated with increased risk for postextubation uao include female sex ( probably resulting from small airway size ) , trauma patient , age above 80 years , excessively mobile or overly large ett size , ratio of ett size to laryngeal diameter above 45% , ratio of patient height to tube diameter , duration of intubation , tracheal infection , absence of cough , absence of sedation , low glasgow coma scale score , or excess cuff pressure [ 2 - 5 ] . research into detection of uao , with the ett in place , has recently focused on using the quantitative cuff leak test . during this maneuver
the patient breathes on assist control ventilation , the endotracheal cuff is deflated , and the difference between inspired and expired tidal volume is compared .
an obstructed upper airway results in similar inspiratory and expiratory volumes , whereas a patent airway results in a substantial difference as a large volume of gas escapes around the tube . this quantitative cuff leak can be reported as either a percentage of inspired tidal volume or as an absolute cuff leak volume ( clv ) .
previous investigators have found that the risk for postextubation stridor is increased when clv is less than approximately 12% to 25% of inspired volume or an absolute value of less than 110 to 130 ml [ 2,6 - 9 ] . although previous studies conducted in pediatric patients found that corticosteroids reduce the prevalence of postextubation uao by nearly 40% and may reduce the need for re - intubation , earlier controlled trials in mechanically ventilated adults did not corroborate those findings .
francois and colleagues   recently compared 20 mg methylprednisolone ( given every 4 hours for 12 hours before extubation ) with placebo in nearly 700 adults patients who had been intubated for at least 36 hours .
corticosteroid pretreatment was associated with decreased risk for postextubation uao ( 3% versus 22% ) , need for re - intubation ( 4% versus 8% ) , and need for re - intubation secondary to uao ( 0.3% versus 4% ) . the number needed to treat ( nnt ) was eight to prevent one case of stridor and 26 to prevent one case of re - intubation .
cheng and colleagues   used a reduced clv ( 24% of inspired tidal volume ) to define and study patients at high risk for postextubation uao .
patients randomly assigned to methylprednisolone ( 40 mg every 6 hours for four doses ) were less likely either to experience stridor ( 7% versus 30% ) or to require re - intubation ( 7% versus 19% ) than were those receiving placebo .
the study reported in this issue of critical care   also targeted high - risk patients by examining those ventilated for at least 48 hours and with a clv below 110 ml .
patients were randomly assigned to receive placebo or dexamethasone 5 mg every 6 hours for 24 hours , and were then extubated 24 hours later .
the dexamethasone group was less likely to develop postextubation stridor ( 10% versus 27.5% ; nnt = 5.7 ) without a difference in need for re - intubation ( 2.5% versus 5% ; nnt = 40 ) .
an important observation is that dexamethasone led to a significant increase in clv that persisted for 24 hours after the last dose ( for example , at the time of extubation ) . given that no further improvement in clv occurred after the last dose of dexamethasone , one could argue for immediate extubation at that time rather than waiting an additional 24 hours .
the study by lee and coworkers   also revealed that 14 out of 285 in the non - randomized cohort ( 4.9% ) , who had a clv above 110 ml , developed stridor . examining these patients and those randomly assigned to placebo , only 20% with postextubation uao required re - intubation , possibly a result of the effective use of inhaled racemic adrenaline ( epinephrine ) and noninvasive ventilation . among placebo patients , 73%
did not develop postextubation uao , despite a clv below 110 ml ; similar findings have been noted by other investigators .
a falsely low clv may result from secretions adherent to or pooled around the ett .
alternatively , with the cuff deflated , the patient may breathe additional tidal volume around the tube ( in addition to machine delivered volume ) , leading to a falsely low measurement of inspired tidal volume .
this phenomenon can be overcome by delivering the machine breath with the cuff inflated and then deflating the cuff just before expiration .
the evidence is now mounting that corticosteroids can prevent postextubation uao , and possibly the need for re - intubation , but should all patients be intubated for longer than 36 to 48 hours receive such therapy ? although a short course of corticosteroids may be relatively safe , further study is warranted .
this author believes the focus should continue to be on targeting patients at greatest risk .
although the study by francois and coworkers   examined an ' unselected ' cohort , the 22% incidence of postextubation uao suggests a high risk group . using
the clv can help to identify a cohort at greater risk , but the sensitivity and specificity of the test is suboptimal . using this test alone to determine need for prophylactic corticosteroids will result in an unnecessary 12 to 24 hour prolongation of intubation for three out of every four such patients .
another approach is to identify first a high - risk cohort based on clinical factors ( for instance , age , sex , tube size , and so on ) and then to apply clv to determine which patients should receive corticosteroids before extubation .
clv = cuff leak volume ; ett = endotracheal tube ; nnt = number needed to treat ; uao = upper airway obstruction .
intubation of the airway can lead to laryngotracheal injury , resulting in extubation failure from upper airway obstruction ( uao ) . 
 a number of factors can help to identify patients who are at greatest risk for postextubation uao . 
 three randomized controlled trials demonstrate that prophylactic corticosteroids decrease the risk for postextubation uao and probably the need for re - intubation .