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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Multicenter Study
A survey of antenatal and peripartum provision of information on analgesia and anaesthesia.
Why is this relevant?
Anaesthetists and anesthesiologists have long worried about the recall of labouring women when presented with risk-benefit discussions prior to epidural analgesia or receiving anaesthesia for cesarean section.
This UK survey of over 900 women across 28 Greater London hospitals explored recall of this antenatal and intrapartum information, along with maternal satisfaction.
What did they find?
There was very little recall of receiving either thorough labour analgesia information (9%) or anaesthesia for CS (12%) provided during the antenatal period.
During the interpartum period, fewer than two-thirds (62%) recalled receiving thorough information during labour before insertion, and less than one-third (28%) before Caesarean section anaesthesia.
13% of women did not recall receiving any information before epidural insertion.
These are concerning findings in a modern era where patient autonomy and informed consent are prioritised, and more so where informed decision making may contribute to a positive birth experience.
Interestingly, verbal information appeared best recalled (OR 5.9 to 20.7 across different categories), although this is counter to past studies showing superiority of written information.
Be clear
Because the 28 hospitals contributing to the survey had large practice differences in how antenatal anaesthetic information was provided, it is difficult to determine whether the provision of information or recall itself is the problem.
Take-home...
Regardless of the cause, a large proportion of pregnant women did not recall being adequately informed before epidural analgesia or caesarean anaesthesia. This needs to be improved.
summary -
Audio recording consent discussions, and giving a copy of the recording to the patient to keep, might improve the consent process and reduce the risk of misunderstandings, complaints or medicolegal claims. However, there may be concerns over confidentiality and how being recorded could affect the consent discussion. ⋯ There was a wide range of opinions, with women and staff similarly supportive of audio recording overall, but the women were more supportive of recording than the staff when asked if they were against it, or whether they would support recording the discussion if the patient requested it; and less concerned than the staff regarding the potential disadvantages of audio recording. There were no significant differences in the views between anaesthetists, obstetricians and midwives.