Article Notes

Bacteriophage therapy may offer one answer to growing bacterial antibiotic-resistance.

  Daniel Jolley

Hypertonic saline use in sepsis reduces resuscitation fluid volume but has no effect on survival.

  Daniel Jolley

Intensivists hold different views on their own thresholds for intensive care admission versus those they hold for patients.

  Daniel Jolley

There is inadequate evidence supporting the benefit of music on sedation, analgesia or delirium in critically ill patients.

  Daniel Jolley

Subcostal transversus abdominis plane (TAP) block does not improve analgesia after laparoscopic cholecystectomy.

  Daniel Jolley

Anesthesiologists are overconfident in their knowledge and management of neuromuscular blocking drugs.

  Daniel Jolley

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.

  Daniel Jolley

Epinephrine (adrenaline) likely improves return of spontaneous circulation and survival up to 3 months after out-of-hospital cardiac arrest when compared to other vasopessors.

  Daniel Jolley

Hypoxaemia at induction is relatively common, with unsurprising independent risk factors (difficult preoxygenation, mask ventilation, and intubation).

  Daniel Jolley

The new Score for Prediction Of Postoperative Respiratory Complications (SPORC-2) more reliably predicts the need for early post-operative re-intubation.

  Daniel Jolley