Thyromental distance ("Patil") revisited : Knowledge and performance of a basic airway screening tool among European anesthetists

[Noninvasive evaluation of airways prior to sedation or anesthesia : An update within the framework of the revision of the German S1 guidelines on airway management 2015 of the German Society for Anesthesiology and Intensive Care Medicine]

As a single and reliable parameter for prediction of the difficult airway is missing, the specialist societies for anesthesiology recommend the use of scores that combine the individual parameters. Contemporary scores include head-neck mobility, mouth opening and anatomical distances. Their training and correct performance are essential. For a broad acceptance the performance has to be easy and fast. In addition, before anesthesia a check must be made for pathological alterations (e.g. tumors) in the head and neck region and the patient history must be thoroughly determined. If the patient reports difficulties with securing the airway in the past, these are likely to occur again if they have not been surgically resolved. This includes an accurate documentation of the airway and knowledge of the in-house standard operating procedure on unexpected difficult airways as well as local equipment. Preparation causes work but may save lives.

[Update Mallampati : Theoretical and practical knowledge of European anesthetists on basic evaluation of airways]

In 1985 Mallampati et al. published a non-invasive score for the evaluation of airways (Mallampati grading scale, MGS), which originally consisted of only three different classes and has been modified several times. At present it is mostly used in the version of Samsoon and Young consisting of four different classes. Class I: soft palate, fauces, uvula, palatopharyngeal arch visible, class II: soft palate, fauces, uvula visible, class III: soft palate, base of the uvula visible and class IV: soft palate not visible. Nevertheless, other versions of MGS still exist, each having different values for sensitivity and specification. The current opinion is therefore that MGS is no longer useful as a stand-alone predictor but in combination with others it is still part of today's most relevant guidelines, such as those of the American Society of Anesthesiologists (ASA), the UK's Difficult Airway Society (DAS), the European Society of Anaesthesiology (ESA) and the German Society for Anesthesiology and Intensive Care Medicine (DGAI) and must therefore be known by anesthetists. Even in times of sophisticated tools for airway management, the procedure remains a high risk, so every anesthetist has to be prepared for and well trained in management of known and unexpected difficult airways. Evaluation of the patient's airway is a part of modern airway management to prevent problems and reduce risk of hypoxia during the procedure. The theoretical knowledge and practical skills of European anesthetists were evaluated at two international congresses, the German Anesthesia Congress (DAC) and Euroanaesthesia 2014. The DAC is an annual meeting of German speaking anesthetists, hosted by the DGAI. The Euroanaesthesia is the annual European pendant hosted by the ESA. Participation was voluntary and only physicians were allowed to take part. Theory was evaluated by a questionnaire containing open and closed questions for MGS that had to be answered by every participant alone. Apart from theory, a practical evaluation was performed. Every participant had to classify the MGS of a human airway model. The model was identical on both congresses. According to the original publication a checklist containing the factors essential for the correct performance was filled out by a supervising experienced anesthetist. During DAC 2014 n = 267 physicians participated in the study, 22 participants were excluded due to inconsistent answers, incomplete questionnaires or missing practical part. A total of 245 data sets were evaluated. During Euroanaesthesia 2014 n = 298 physicians participated in the study, 68 participants were excluded due to inconsistent answers, incomplete questionnaires or missing practical part and 230 data sets were evaluated. At the DAC the mean age (± SD) was 44.5 ± 9.5 years, 157 (64.1%) were male and 88 (35.9%) were female. Working experience was trainee anesthetist in 16.7% and other participants were experienced anesthetists. At the ESA the mean age (± SD) was 42.4 ± 9.5 years, 133 (57.8%) were male and 97 (42.2%) female. Trainee anesthetists were 15.2%, the rest were experienced anesthetists. The DAC participants knew Mallampati classes 1 (65%) and 4 (45%) better than 2 and 3 and there was no relevant differences to the ESA (close to 30% knew the classes 1-4 here). Classification of the airway model was correct in 62% and 67% at DAC and ESA, respectively. Most participants performed the practical evaluation correctly except the sitting position of the model. In agreement with earlier studies, these results show the lack of knowledge in evaluation of airways according to current guidelines of all relevant societies. This is likely to increase preventable risks for patients as unexpected difficult airway management increases the risk for hypoxia and intubation damage.