Prediction and Outcomes of Impossible Mask Ventilation

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Abstract
MASK ventilation is an essential component of airway management and serves an important role in the case of difficult intubation.1 However, despite the large amount of research into the prediction of and outcomes associated with difficult intubation, data on difficult or impossible mask ventilation are limited.2 In 2006, we reviewed 22,000 anesthetics and observed 313 (1.4%) cases of difficult mask ventilation and 37 (0.16%) cases of impossible mask ventilation.3 Although we were able to derive a robust prediction scale for difficult mask ventilation, the limited number of observed impossible mask ventilation attempts did not offer the statistical power necessary to derive a prediction scale with adequate discriminating capability. We were only able to identify a history of snoring and limited thyromental distance as predictors of impossible mask ventilation. In addition, 17 of the 37 impossible mask ventilation patients did not undergo a complete, robust airway exam including an assessment of jaw protrusion, further reducing the ability to derive a useful prediction scale. Finally, the previous data did not include a detailed, manual review of the anesthesia record to identify the ultimate clinical management of each event. As a result, clinicians still have minimal data to guide their prediction or management of impossible mask ventilation, and the need for further research into impossible mask ventilation persists.4