Success stories: use of patient vignettes to assess the ability of physicians to predict extubation success.

Safely returning intubated, mechanically ventilated patients to independent breathing requires 3 steps.1,2 First, clinicians must recognize when respiratory failure has resolved or improved enough to allow a spontaneous breathing trial (SBT). Second, a 30–120 min SBT should be used to test the patient’s ability to breathe without the ventilator.3 Third, if the SBT is successful, the physician must decide whether to extubate. In many intensive care units (ICU), respiratory therapists and nurses drive the first 2 steps, which are relatively straightforward, guided by protocols.4-6 The decision to extubate is more challenging.1,7,8 Within 24–72 hours, 2–25% of newly extubated patients need re-intubation.1,7,8 Failed extubations can lead to prolonged immobility, longer stay, and increased risk of ventilator-associated pneumonia, need for tracheotomy, and mortality.1,7-9 Identifying high-risk patients helps prevent premature extubation. Among those extubated, those at high risk merit careful monitoring and occasionally noninvasive ventilation to help prevent re-intubation.7,8,10 Causes of extubation failure fall into 2 categories: those associated with ventilatory failure and inadequate gas exchange, and those associated with airway compromise. Ventilatory failure most commonly results from a strength-load imbalance. Effective screening and performance of SBTs should screen out most patients at risk for ventilatory failure before extubation. Some patients who pass SBTs will develop ventilatory failure over the ensuing hours to days (eg, those with congestive heart failure or neuromuscular disease). Risk of airway compromise is more difficult to predict.1,7-9 Two major causes include post-extubation laryngeal edema and inability to keep the airway clear of secretions. Although its accuracy is disputed, a “cuff leak test” can help identify patients with laryngeal edema who may benefit from corticosteroid treatment before extubation.11 Attention to quantity of secretions, cough strength, and mental status may help identify patients unable to keep their airways clear and therefore unready for extubation.12 In summary, a deliberate approach, combining careful screening, performing a 30– 120 min SBT, and assessing airway risk can mitigate,but not eliminate, the risk of re-intubation. Given the challenges and dangers associated with extubation decisions, we were pleased to see the study by Tulaimat and Mokhlesi in this issue of RESPIRATORY CARE, which explores the ability of ICU physicians to predict extubation success.13 Tulaimat and Mokhlesi extracted a series of 32 clinical vignettes from a previously describedcohort of patients who had been extubated after an SBT on CPAP of 5 cm H2O and pressure support of 5–7 cm H2O. Half were successfully extubated and the other half required re-intubation. The vignettes included ample clinical and physiological data, generally available to physicians making extubation decisions, including information on the patient’s SBT performance, arterial blood gas results, and descriptions of secretion quantity and mental status. Fiftyfive intensivists were asked to participate in the survey, and 45 responded. For each vignette the respondent was asked to decide if extubation was appropriate. If the respondent thought extubation was not appropriate, he or she was asked to describe the factor or factors influencing the decision. Accuracy was calculated by determining sensitivity (defined as the fraction of successfully extubated patients whom the surveyed physicians correctly decided to extubate) and specificity (defined as the fraction who required re-intubation and for whom the physicians correctly decided to postpone extubation). Reliability was defined by comparing decisions among physicians. A logistic regression model was constructed based on reasons the physicians cited to forgo extubation. The accuracies of the model and physician predictions were then compared.