Anaesthesia
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What’s so interesting?
De Carvalho and co. show that pre-operative voice analysis can be predictive of difficult laryngoscopy.
I’d never thought about that...
The authors describe how different frequency components and acoustic qualities of the voice are, at least partly, determined by the shape and size of different anatomical areas of the vocal tract. By analysing the most intense frequencies (voice formants) within the voice spectrum they were able to correlate components with difficult laryngoscopy, namely Cormack & Lehane grade 3 or 4.
The practicalities
During pre-anaesthetic assessment, 467 elective general surgical patients were asked to pronounce each of the five vowels, corresponding to base phonemes. This was recorded on a smartphone and then later processed and analysed on a laptop computer.1
They found...
A model using voice ‘formants’ could reliably predict difficult laryngoscopy with a ROC-AUC of 0.761 (ie. 76% probability that it correctly classifies a patient as difficult or not). When combined with the modified Mallampati this improved to 92%.
The big picture
While interesting, it’s worth remembering that using voice formants (76%) did not perform as well as modified Mallampati alone (87%), and that this performance is also surprisingly much better than those from the most recent Cochrane meta-analysis (2018) of bedside airway assessment. Over 133 studies the Cochrane review reported a summary sensitivity of only 53% and specificity of 80% for the modified Mallampati (vs 100% and 75% respectively for this study).
Although this is an interesting and novel new test, it’s just not that simple... Screening for an uncommon outcome using tests with imperfect sensitivity and specificity is already problematic, but doubly so when we are not always certain which outcome we should be screening for (laryngoscopy, intubation, ventilation, oxygenation...).
As an airway screening test, voice analysis is both different and also more of the same.
summary
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It would also be feasible for recording, analysis and reporting to occur entirely at the bedside on a smartphone. ↩
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Observational Study
Time to oxygenation for cannula- and scalpel-based techniques for emergency front-of-neck access: a wet lab simulation using an ovine model.
In a wet-lab cannot-intubate cannot-oxygenate front-of-neck access simulation, a needle-cannula technique resulted in faster and more reliable oxygen delivery than scalpel-bougie.
pearl -
The primary aim of this study was to identify, describe and compare the content of existing difficult airway management algorithms. Secondly, we aimed to describe the literature reporting the implementation of these algorithms. A directed search across three databases (MEDLINE, Embase and Scopus) was performed. ⋯ The identified algorithms are overwhelmingly similar, yet many use differing terminology. The frequency of algorithm publication has increased recently, yet adherence and implementation outcome data remain limited. Our results highlight the lack of a single algorithm that is universally endorsed, recognised and applicable to all difficult airway management situations.
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Advanced airway management is a treatment priority in trauma care. It is likely that a proportion of patients who receive urgent airway management on arrival in the emergency department represent an unmet demand for airway intervention in the pre-hospital phase. This study aimed to investigate emergency airway practice in major trauma patients and establish any unmet demand in this patient group. ⋯ Of the patients whose tracheas were intubated in the emergency department, this was done within 30 min of hospital arrival in 3264 patients (75%). Excluding tracheal intubation, 1593 patients had a pre-hospital airway intervention of which 881 (55%) subsequently had their trachea intubated in the emergency department; tracheal intubation was done within 30 min of arrival in the majority of these cases (805 patients (91%)). Over 70% of emergency department tracheal intubations in patients with traumatic injuries were performed within 30 min of hospital arrival; this suggests there may be an unmet demand in pre-hospital advanced airway management for trauma patients in England.