Introducing new anaesthetic equipment into clinical practice

New guidelines for research in airway device evaluation: time for an updated approach (ADEPT-2) to the Difficult Airway Society's 'ADEPT' strategy?

In this article we present the learning from a clinical study of airway device evaluation, conducted under the framework of the Difficult Airway Society (DAS, UK) 'ADEPT' (airway device evaluation project team) strategy. We recommend a change in emphasis from small scale randomised controlled trials conducted as research, to larger-scale observational, post-marketing evaluation audits as a way of obtaining more meaningful information.

Updated guideline on equipment to manage difficult airways: Australian and New Zealand College of Anaesthetists

The Australian and New Zealand College of Anaesthetists (ANZCA) recently reviewed and updated the guideline on equipment to manage a difficult airway. An ANZCA-established document development group, which included representatives from the Australasian College for Emergency Medicine and the College of Intensive Care Medicine of Australia and New Zealand, performed the review, which is based on expert consensus, an extensive literature review, and bi-nationwide consultation. The guideline (PG56(A) 2021, https://www.anzca.edu.au/getattachment/02fe1a4c-14f0-4ad1-8337-c281d26bfa17/PS56-Guideline-on-equipment-to-manage-difficult-airways) is accompanied by a detailed background paper (PG56(A)BP 2021, https://www.anzca.edu.au/getattachment/9ef4cd97-2f02-47fe-a63a-9f74fa7c68ac/PG56(A)BP-Guideline-on-equipment-to-manage-difficult-airways-Background-Paper), from which the current recommendations are reproduced on behalf of, and with the permission of, ANZCA. The updated 2021 guideline replaces the 2012 version and aims to provide an updated, objective, informed, transparent, and evidence-based review of equipment to manage difficult airways.

An assessment of introducers used for airway management

Different introducers are available to assist with tracheal intubation. Subtle differences in the design of introducers can have a marked effect on safety and performance. The Difficult Airway Society's Airway Device Evaluation Project Team proposal states that devices should only be purchased for which there is at least a case-control study on patients assessing airway devices. However, resources are not currently available to carry out a case-control study on all introducers available on the market. This study comprised a laboratory and manikin-based investigation to identify introducers that could be suitable for clinical investigation. We included six different introducers in laboratory-based assessments (design characteristics) and manikin-based assessments involving the participation of 30 anaesthetists. Each anaesthetist attempted placement in the manikin's trachea with each of the six introducers in a random order. Outcomes included first-time insertion success rate; insertion success rate; number of attempts; time to placement; and distance placed. Each anaesthetist also completed a questionnaire. First-time insertion success rate depended significantly on the introducer used (p = 0.0016) and varied from 47% (Armstrong and P3) to 77% (Intersurgical and Frova). Median time to placement (including oesophageal placement) varied from 10 s (Eschmann and Frova) to 20 s (P3) (p = 0.0025). Median time to successful placement in the trachea varied from 9 s (Frova) to 22 s (Armstrong) (p = 0.037). We found that the Armstrong and P3 devices were not as acceptable as other introducers and, without significant improvements to their design and characteristics, the use of these devices in studies on patients is questionable. The study protocol is suitable for differentiating between different introducers and could be used as a basis for assessing other types of devices.

Performance of EasyBreath Decathlon Snorkeling mask for delivering continuous positive airway pressure

During the COVID-19 pandemic, the need for noninvasive respiratory support devices has dramatically increased, sometimes exceeding hospital capacity. The full-face Decathlon snorkeling mask, EasyBreath (EB mask), has been adapted to deliver continuous positive airway pressure (CPAP) as an emergency respiratory interface. We aimed to assess the performance of this modified EB mask and to test its use during different gas mixture supplies. CPAP set at 5, 10, and 15 cmH₂O was delivered to 10 healthy volunteers with a high-flow system generator set at 40, 80, and 120 L min^-1 and with a turbine-driven ventilator during both spontaneous and loaded (resistor) breathing. Inspiratory CO₂ partial pressure (PiCO₂), pressure inside the mask, breathing pattern and electrical activity of the diaphragm (EAdi) were measured at all combinations of CPAP/flows delivered, with and without the resistor. Using the high-flow generator set at 40 L min^-1, the PiCO₂ significantly increased and the system was unable to maintain the target CPAP of 10 and 15 cmH₂O and a stable pressure within the respiratory cycle; conversely, the turbine-driven ventilator did. EAdi significantly increased with flow rates of 40 and 80 L min^-1 but not at 120 L min^-1 and with the turbine-driven ventilator. EB mask can be safely used to deliver CPAP only under strict constraints, using either a high-flow generator at a flow rate greater than 80 L min^-1, or a high-performance turbine-driven ventilator.

A comparison of fibreoptic-guided tracheal intubation through the Ambu ® Aura-i ™, the intubating laryngeal mask airway and the i-gel ™: a manikin study

We compared the Aura-i(™) , intubating laryngeal mask airway and i-gel(™) as conduits for fibreoptic-guided tracheal intubation in a manikin. Thirty anaesthetists each performed two tracheal intubations through each device, a total of 180 intubations. The median (IQR [range]) time to complete the first intubation was 40 (31-50 [15-162]) s, 37 (34-48 [25-75]) s and 28 (22-35 [14-59]) s for the Aura-i, intubating laryngeal mask airway and i-gel, respectively. Tracheal intubation through the i-gel was the quickest (p < 0.01). Resistance to railroading of the tracheal tube over the fibrescope was significantly greater through the Aura-i compared with the intubating laryngeal mask airway and the i-gel (p = 0.001). There were no failures to intubate through the intubating laryngeal mask airway or the i-gel but six intubation attempts through the Aura-i were unsuccessful, in five owing to a railroading failure and in one owing to accidental oesophageal intubation. We conclude that the Aura-i does not perform as well as the intubating laryngeal mask airway or the i-gel as an adjunct for performing fibreoptic-guided tracheal intubation.

Combined use of a McGrath® MAC video laryngoscope and Frova Intubating Introducer in a patient with Pierre Robin syndrome: a case report

Patients with Pierre Robin syndrome are characterized by micrognathia, retrognathia, glossoptosis, and respiratory obstruction and are prone to have a difficult-to-intubate airway. The McGrath® MAC video laryngoscope provides a better view of the glottis than a Macintosh laryngoscope, but it is not easy to insert an endotracheal tube through the vocal cords because a video laryngoscope has a much greater curvature than that of a conventional direct laryngoscope and an endotracheal tube has a different curvature. The Frova Intubating Introducer is used as a railroad for an endotracheal tube in cases of a difficult airway. We thought that a combination of these two devices would make it easy to insert an endotracheal tube through the vocal cords, as a McGrath® MAC video laryngoscope provides a better glottic view and the Frova Intubating Introducer is a useful device for placing an endotracheal tube through the glottis. We report a successful endotracheal intubation with use of the McGrath® MAC video laryngoscope and Frova Intubating Introducer in a patient with Pierre Robin syndrome.

Functional evaluation and practice survey to guide purchasing of intravenous cannulae

Background

There are wide variations in the physical designs and attributes between different brands of intravenous cannulae that makes product selection and purchasing difficult. In a systematic assessment to guide purchasing, we assessed two cannulae – Cannula P and I. We proposed that the results of in-vitro performance testing of the cannulae would be associated with preference after clinical comparison.

Methods

We designed an observer-blinded randomised head-to-head trial between the 18, 20 and 22 gauge versions of Cannula P and I. Our primary end-point was pressure (mmHg) generated during various flow rates and our secondary end-point was the force (Newton) required to slide the catheter away from the needle. This was followed by a prospective electronic survey following a two-week clinical trial period.

Results

The mean difference in resistance between Cannula P and I was: 307 mmHg.L^-1.hr^-1 (95% CI: 289–325, p < 0.001) for 22G; 135 mmHg.L^-1.hr^-1 (95% CI: 125–144, p < 0.001) for 20G; and 27 mmHg.L^-1.hr^-1 (95% CI: 26–28, p < 0.001) for 18G. The mean difference in the force needed to displace the catheter away from its needle was: 1.41 N (95% CI: 1.09-1.73, p < 0.001) for 22G; 0.19 N (95% CI: -0.04-0.41, p = 0.12) for 20G; and 1.96 N (95% CI: 1.40-2.52, p < 0.001) for 18G. After a trial period, all 16 anaesthetist who had used both cannulae preferred Cannula I to P.

Conclusions

The evaluation process described here could help hospitals improve efficient product selection and purchasing decisions for intravenous cannulae.

Non-Luer connectors: are we nearly there yet?

The Department of Health aims to eliminate the use of devices with a Luer connector firstly from 'single shot' neuraxial procedures (April 2012) and subsequently from all neuraxial and regional anaesthesia procedures (April 2013). This initiative is important for all anaesthetists, oncologists, paediatricians and neurologists. Once achieved, non-Luer connectors for neuraxial procedures will create one more barrier to wrong-route errors. The period until full implementation and market stability remains problematic. Avoidance of unintended consequences requires professional and individual attention to detail. Considerable progress has been made by manufacturers in the last year in improving the quality and range of equipment available, but despite this not all the necessary equipment is available and there remains a lack of independent evaluation, which is urgently needed to enable clinicians to judge the absolute and relative performance of different connectors. Initial evaluation of devices with new connectors can (and should) take place in a laboratory with rigs and manikins, with patient-based evaluation following after the results of the technical and usability evaluations are available. A structured evaluation of all five current connectors is urgently needed. Non-Luer connectors, however successful, will not create barriers to several type of wrong-route error and solutions to these should also be actively sought. It is clear that the initiative has been more complex than the Health Select Committee, the National Patient Safety Agency and the External Reference Group anticipated, but while there is still much work to be done, we should acknowledge that much progress has been made.

Equipment to manage a difficult airway during anaesthesia

Airway complications are a leading cause of morbidity and mortality in anaesthesia. Effective management of a difficult airway requires the timely availability of suitable airway equipment. The Australian and New Zealand College of Anaesthetists has recently developed guidelines for the minimum set of equipment needed for the effective management of an unexpected difficult airway (TG4 [2010] www.anzca.edu.au/resources/professionaldocuments). TG4 [2010] is based on expert consensus, underpinned by wide consultation and an extensive review of the available evidence, which is summarised in a Background Paper (TG4 BP [2010] www.anzca.edu.au/ resources/professional-documents). TG4 [2010] will be reviewed at the end of one year and thereafter every five years or more frequently if necessary. The current paper is reproduced directly from the Background Paper (TG4 BP [2010]).

A prospective randomized trial comparing supraglottic airways for flexible bronchoscopy in children

OBJECTIVE

A prospective randomized, controlled trial was conducted comparing supraglottic airways (SGA) for flexible bronchoscopy in 100 children.

BACKGROUND

Pediatric flexible bronchoscopy is commonly performed using a SGA as both a ventilation device and a conduit for flexible bronchoscopy. We observed that some disposable SGAs were associated with increased resistance to bronchoscope manipulation compared to the LMA Classic (cLMA).

METHODS

We compared the cLMA to the Ambu Aura Once, Portex Soft Seal, Boss Systems disposable silicone laryngeal mask, and LMA Unique. We recorded the subjective resistance of the bronchoscope manipulation within the SGA by linear analog score and measured the time to insert the bronchoscope from the proximal end of the SGA to the right upper lobe. We also scored the view of the larynx through the bronchoscope and measured SGA cuff pressures.

RESULTS

Resistance to bronchoscope manipulation during pediatric flexible bronchoscopy was higher using polyvinyl chloride (PVC) disposable SGAs (Ambu, Unique, and Portex) than the silicone re-usable cLMA (P < 0.0001). The Unique and Ambu laryngeal masks were clinically inferior to the cLMA at all levels of the airway (P < 0.0001). The Portex Soft Seal was not different above the larynx but was significantly statistically inferior at (P < 0.04) and below the larynx (P < 0.006) and inferior overall (P < 0.007). Boss Systems single-use laryngeal mask was as effective as the cLMA.

CONCLUSION

In this trial, PVC single-use laryngeal masks were inferior to the silicone cLMA and Boss Systems laryngeal masks for flexible bronchoscopy in children.

Practice Patterns for Predicted Difficult Airway Management and access to Airway Equipment by Anaesthetists in Queensland, Australia

A postal survey was conducted to investigate difficult airway management, training and equipment availability among Fellows of the Australian and New Zealand College of Anaesthetists in Queensland. The survey aimed to determine practise patterns for predicted difficult airways and investigate equipment availability.

Participants were asked to nominate an induction method, intubation method and airway adjunct for each of the five difficult airway scenarios. The cases consisted of one elective and four emergency scenarios. Availability of difficult airway devices in their institution was also assessed, as well as demographics of practice and airway-related maintenance of professional standards participation.

There were 454 surveys distributed and 250 returned (response rate 55%). Direct laryngoscopy and flexible fibreoptic intubation were the most commonly selected techniques for all five cases. Difficult intubation trolleys were available to 98% of responders. Certain types of equipment (such as fibreoptic bronchoscopes and cricothyroidotomy kits) were available less frequently in private institutions. We recommend a standardisation of difficult airway management equipment and an on-going training program to provide support for anaesthetists in all locations.

Assessing the performance of the Whisperflow continuous positive airway pressure generator: a bench study

BACKGROUND

There are few data describing the performance of the Whisperflow continuous positive airway pressure (CPAP) generator.

METHODS

(i) (a) A static test of 11 Whisperflow devices examining maximum flow generation with no load and with 2.5, 5, 7.5, 10, 15, and 20 cm H2O valve loading, at varying Fi(O2). (b) CPAP valves (Accu-peep(R), Vital Signs, Totowa, NJ, USA) were tested by measuring mean upstream pressure at varying flows in five valves (2.5, 5, 7.5, 10, 15, and 20 cm H2O). (ii) We measured the mean and minimum inspiratory mask pressure generated by a representative Whisperflow device in a model of spontaneous respiration. Measurements were made with combinations of Fi(O2), ventilatory frequency, tidal volume, and valve loading similar to those encountered in clinical practice.

RESULTS

(i) (a) The flow generated by the Whisperflow valves decreases with increasing valve load and increasing Fi(O2) (from 140 to 20 litre min(-1)). (b) The CPAP valves maintain the required pressure within acceptable limits against varying flow. (ii) At all permutations, the mean inspiratory mask pressure was significantly lower than that required. At high inspiratory flow rates, the minimum inspiratory pressure approached atmospheric pressure.

CONCLUSIONS

The Whisperflow may not perform as expected. Clinicians should be cautious when using this device, particularly with high Fi(O2) and CPAP valve load. The flow setting should be set at maximum. Failure of CPAP therapy may be due to failure of the generator. Further in vivo data are required.