RESUMO
A prospective study was designed to compare the value of clinical signs aimed to predict difficult intubation in women. A group of 663 women, scheduled for elective surgery, were assessed by an anaesthetist at the preanaesthetic visit. Following parameters were assessed: the degree of mouth opening, the chin-hyoid bone and the chin-thyroid cartilage distances, dental and facial abnormalities, age, weight. All patients were ranked on the Mallampati scale. Another anaesthetist carried out the anaesthetic induction and endotracheal intubation. The latter was deemed to have been difficult if special procedures had been required (use of a stylet, a fibroscope, or Sellick's manoeuvre). In accordance with these criteria 12.5% of women were difficult to intubate. Furthermore, he assessed the degree of glottic exposure, using a Macintosh blade and according to Cormack's classification. Six per cent of women were ranked C or D in Cormack's classification (C: the glottic aperture was not seen; D: the epiglottis was not seen). Finally 66% of women with difficult intubation and 84% of those with severely abnormal glottic exposure were ranked greater than 1 on the Mallampati scale. This scale had high sensitivity (0.84), but a specificity of only 0.66. Other clinical criteria (mouth opening, the chin-hyoid bone distance) had a lower sensitivities, but seemed more specific. Multivariate analysis showed that specificity could be improved (0.84) if the distance between the upper and lower incisor teeth (mouth opening) was associated with Mallampati's rank, without any loss in sensitivity. A simple chart is proposed to assess the risk of difficult intubation.
