Figure 58-12 Graphic representation of the factors predictive of a difficult intubation. Such factors include Malampatti class, short neck (SN), protruding maxillary incisors (PI), or receding mandible (RM). Data were obtained from 1500 parturients undergoing cesarean section under general anesthesia. Values in parentheses represent observed incidences of risk factor combinations in the series. (From Rocke DA, Murray WB, Rout CC, et al: Relative risk analysis of factors associated with difficult intubation in obstetric anesthesia. Anesthesiology 77:67, 1992.)