Difficult face-mask ventilation and difficult laryngoscopy.

To the Editor: Our thanks are due to Kheterpal et al. 1 for another valuable addition to our understanding of airway management during anesthesia. Their work suggests that provided we exclude the patients with obvious abnormalities, we will find that the incidence of the combination of difficult mask ventilation (DMV) and difficult laryngoscopy (DL) is infrequent but not rare (0.4%), and the outcome is good when standard methods are applied. As well as incidence and outcome, Dr. Kheterpal et al. addressed the prediction of DMV plus DL and presented odds ratios* to describe their findings. They used a group (class I, 0 to 3 risk factors) with few risk factors as a reference , but we should note that cases of DMV plus DL occurred (107 patients) in this group. The odds ratio for the group of patients with the most risk factors (class V, 7 to 11) was 18.4, which sounds high, but I suspect that the positive predictive value gives most of us a clearer idea of the clinical significance. The positive predictive value for DMV plus DL of class V abnormalities was only 3.31%, which means that 96.69% of predictions were wrong and the patients did not present difficulty. The conclusion must To the Editor: Thanks to Kheterpal et al. 1 for their study on the incidence of concurrent difficult laryngoscopy and difficult mask ventilation. In their database series of 177,000 cases, both airway maneuvers were difficult in 0.4% of patients. This rate is alarmingly high. Even worse, it may be an underestimate because the study excluded patients who were predicted to be difficult and offered alternative techniques. Inevitably, the definitions used are important when interpreting these results. First, mask ventilation was assessed using the Han scale: grades 3 or 4 were defined as " difficult. " Han et al. 2 defined grade 3 as mask ventilation, which was " inadequate, unstable , or requiring two operators, " and grade 4 as " impossible. " These two grades cover a broad range of clinical significance. The need for a second operator is mild inconvenience compared with the potential crisis of a flat-line capnograph. Second, two methods were used to assess laryngoscopy: the Cormack and Lehane grade and the number of attempts. Grades 3 and 4, or four attempts, constituted " difficulty. " Again, this definition spans a wide range of significance. An epiglottis-only view with easy bougie-guided …