Prediction and Outcome of Impossible Mask Ventilation

Diana Lee, D.O.PGY-1

Journal ClubOctober 21, 2009

Overview• This article addresses an important topic that is central to

airway management for our patients, and it defines important predictors of impossible mask ventilation. It includes a large data set that was thoroughly reviewed manually to determine primary outcome of difficult mask ventilation and prediction score.

• Scientific background is discussed for mask ventilation and the lack of data on predictions and outcomes.

• This article was an observational study x 4yrs (2004-2008) looking at 53,041 cases of masked ventilation in a tertiary center. Primary outcome was impossible mask ventilation, and secondary outcomes were ultimate airway management technique (DL, rigid direct laryngoscopy, flexiable fiberoptic intubation, LMA, pt awakened, surgical airway). This study attempts to define incidence, predictors, and outcomes associated with impossible mask ventilation in a statistical manner.

Summary of findings

• Impossible mask ventilation incidence was 0.15% (n=77; 1:690)

Summary of findings continued…

• Among cases of impossible mask ventilation– 25% was also associated with difficult intubation (n=19)– 19% was successfully intubated (n=15)– 16% required an alternative intubation technique including

surgical airway (n=12)– 0.08% used LMA (n=6)– 0.05% were not intubated (n=4)

• Impossible mask ventilation often requires advanced airway management

• And, impossible mask ventilation is associated with difficult intubation (25%)

Summary of findings continued…

• 5 independent predictors of impossible mask ventilation found from this study with (P <0.05)…

– Neck radiation changes*** (most significant clinical predictor)– Male sex– Sleep apnea– Mallampati III or IV– Presence of beard (previously only associated with difficult, not

impossible, mask ventilation)

Critique of article

• Good points…– This article created the first risk scale for predicting impossible

mask ventilation– The incidence of impossible mask ventilation was consistent

with their previous study– This is the first large scale study on impossible mask

ventilation– 2 study investigators independently reviewed records to

confirm secondary outcome (ultimate airway mangement)– This study can serve as catalyst into researching and further

recommendations on impossible mask ventilations and subsequent difficult intubations.

Critique of article• Bad points…

• This study did not include cases where initial intubation was awake fiberoptic intubation without an attempt to mask ventilate first (usually these pt would be the most difficult to mask ventilate and intubate).

• A subset of the cases were already included in a previous study (20/77 impossible mask ventilation cases). Previous 2006 study observed 22,000 cases.

• More studies need to be done to validate findings from this study.• From this study, no recommendations can be made on managing

impossible mask ventilation and again, further studies will need to be done to offer any guidance.

• Provider variablity.• This study did not use more objective measures of difficult or

impossible mask ventilation.• No specifics on predictor of neck radiation were given.

How does this apply to our practice?

• This article demonstrated the clinical predictors and outcomes of impossible mask ventilation (as opposed to difficult mask ventilation).

• This article highlighted the association of impossible mask ventilation with difficult intubation in a subset of patients.

• Be aware of the variety of provider responses to difficult mask ventilation and hence, difficult intubations.

Open discussion……