Brazilian Journal of Anesthesiology
Brazilian Journal of Anesthesiology
Original Investigation

Preoperative airway ultrasound assessment in the sniffing position: a prospective observational study

Avaliação ultrassonográfica pré-operatória das vias aéreas na posição olfativa: um estudo observacional prospectivo

Miguel Angel Fernandez-Vaquero, Pedro Charco-Mora, Miguel Angel Garcia-Aroca, Robert Greif

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Clinical airway screening tests intend to predict difficult airways, but none have a high predictive value. Recent systematic reviews correlate ultrasound with difficult laryngoscopy. This study aimed primarily to correlate ultrasound measurements of anatomical upper airway structures in the sniffing position with difficult direct laryngoscopy. The secondary aim was to observe gender-based differences.


This prospective, cross-sectional, single-center observational study included 209 patients requiring general anesthesia for elective surgery. Preoperatively, we performed six clinical airway assessments and three ultrasound measurements, which were the Distance from Skin to the Hyoid Bone (DSHB), to the Epiglottis (DSE), and to the anterior commissure of the vocal cords (DSAC) in a sniffing position. Benumof's criteria for the “best view at the first attempt” for direct laryngoscopy assessed the difficulty of laryngoscopy.


The distance from skin to the epiglottis was the best predictor of direct difficult laryngoscopy (defined as Cormack-Lehane grade ≥ 2b) with a minimum thickness cut-off at 2.70 ± 0.19 cm (sensitivity 91.3%; specificity 96.9%). The skin to the hyoid bone distance cut-off was 1.41 ± 0.30 cm with moderate correlation (sensitivity 80.4%; specificity 60.1%). No correlation was found for the distance to the anterior commissure of the vocal cords. In women compared to men, the skin to the epiglottis distance was more sensitive (92.3% vs. 90.9%) and specific (98.8% vs. 95.2%).


DSE in the sniffing position is the most reliable parameter for preoperative airway ultrasound assessment in the Caucasian population, with higher sensitivity and specificity in women, and might be considered as an independent predictor for direct difficult laryngoscopy.


Anesthesia; Airway management; Intubation; Laryngoscopy; Position; Ultrasonography



Os testes de triagem clínica das vias aéreas pretendem prever vias aéreas difíceis, mas nenhum tem alto valor preditivo. Revisões sistemáticas recentes correlacionam ultrassonografia com laringoscopia difícil. Este estudo teve como objetivo principal correlacionar as medidas ultrassonográficas das estruturas anatômicas das vias aéreas superiores na posição olfativa com a laringoscopia direta difícil. O objetivo secundário era observar as diferenças baseadas no gênero.


Este estudo observacional prospectivo, transversal e de centro único incluiu 209 pacientes que necessitavam de anestesia geral para cirurgia eletiva. No pré-operatório, foram realizadas seis avaliações clínicas das vias aéreas e três medidas ultrassonográficas, que foram a Distância da Pele ao Osso Hioide (DSHB), à Epiglote (DSE) e à comissura anterior das cordas vocais (DSAC) em posição olfativa. Os critérios de Benumof para “melhor visualização na primeira tentativa” para laringoscopia direta avaliaram a dificuldade da laringoscopia.


A distância da pele à epiglote foi o melhor preditor de laringoscopia direta difícil (definida como grau Cormack-Lehane ≥ 2b) com um corte mínimo de espessura de 2,70 ± 0,19 cm (sensibilidade 91,3%; especificidade 96,9%). O ponto de corte da distância da pele ao osso hioide foi de 1,41 ± 0,30 cm com correlação moderada (sensibilidade 80,4%; especificidade 60,1%). Nenhuma correlação foi encontrada para a distância à comissura anterior das pregas vocais. Nas mulheres em relação aos homens, a distância da pele à epiglote foi mais sensível (92,3% vs. 90,9%) e específica (98,8% vs. 95,2%).


O DSE na posição olfativa é o parâmetro mais confiável para avaliação ultrassonográfica pré-operatória das vias aéreas na população caucasiana, com maior sensibilidade e especificidade em mulheres, e pode ser considerado um preditor independente para laringoscopia direta difícil.


Anestesia; Manejo de vias aéreas; Intubação; Laringoscopia; Posição; ultrassonografia


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