Ease and comfort of pre-oxygenation with high-flow nasal oxygen cannulae vs. facemask: a randomised controlled trial.

The Difficult Airway Society recommends that all patients should be pre-oxygenated before the induction of general anaesthesia, but this may not always be easy or comfortable and anaesthesia may often be induced without full pre-oxygenation. We tested the hypothesis that high-flow nasal oxygen cannulae would be easier and more comfortable than facemasks for pre-oxygenation. We randomly allocated 199 patients undergoing elective surgery aged ≥ 10 years to pre-oxygenation using either high-flow nasal oxygen or facemask. Ease and comfort were assessed by anaesthetists and patients on 10-cm visual analogue scale and six-point smiley face scale, respectively. Secondary endpoints included end-tidal oxygen fraction after securing a definitive airway and time to secure an airway. A mean difference (95%CI) between groups in ratings of -0.76 (-1.25 to -0.27) cm for ease of use (p = 0.003) and -0.45 (-0.75 to -0.13) points for comfort (p = 0.006), both favoured high-flow nasal oxygen. A mean difference (95%CI) between groups in end-tidal oxygen fraction of 3.89% (2.41-5.37%) after securing a definitive airway also favoured high-flow nasal oxygen (p < 0.001). There was no significant difference between groups in the number of patients with hypoxaemia (Sp O2 < 90%) or severe hypoxaemia (Sp O2 < 85%) lasting ≥ 1 min or ≥ 2 min; in the proportion of patients with an end-tidal oxygen fraction < 87% in the first 5 min after tracheal intubation (52.2% vs. 58.9% in facemask and high-flow nasal oxygen groups, respectively; p = 0.31); or in time taken to secure an airway (11.6 vs. 12.2 min in facemask and high-flow nasal oxygen groups, respectively; p = 0.65). In conclusion, we found pre-oxygenation with high-flow nasal oxygen to be easier for anaesthetists and more comfortable for patients than pre-oxygenation with a facemask, with no clinically relevant differences in end-tidal oxygen fraction after securing a definitive airway or time to secure an airway. The differences in ease and comfort were modest.

Preventing unrecognised oesophageal intubation: a consensus guideline from the Project for Universal Management of Airways and international airway societies.

Across multiple disciplines undertaking airway management globally, preventable episodes of unrecognised oesophageal intubation result in profound hypoxaemia, brain injury and death. These events occur in the hands of both inexperienced and experienced practitioners. Current evidence shows that unrecognised oesophageal intubation occurs sufficiently frequently to be a major concern and to merit a co-ordinated approach to address it. Harm from unrecognised oesophageal intubation is avoidable through reducing the rate of oesophageal intubation, combined with prompt detection and immediate action when it occurs. The detection of 'sustained exhaled carbon dioxide' using waveform capnography is the mainstay for excluding oesophageal placement of an intended tracheal tube. Tube removal should be the default response when sustained exhaled carbon dioxide cannot be detected. If default tube removal is considered dangerous, urgent exclusion of oesophageal intubation using valid alternative techniques is indicated, in parallel with evaluation of other causes of inability to detect carbon dioxide. The tube should be removed if timely restoration of sustained exhaled carbon dioxide cannot be achieved. In addition to technical interventions, strategies are required to address cognitive biases and the deterioration of individual and team performance in stressful situations, to which all practitioners are vulnerable. These guidelines provide recommendations for preventing unrecognised oesophageal intubation that are relevant to all airway practitioners independent of geography, clinical location, discipline or patient type.

Negligible Quantities of Particulate Low-Temperature Pyrogenic Carbon Reach the Atlantic Ocean via the Amazon River.

Particulate pyrogenic carbon (PyC) transported by rivers and aerosols, and deposited in marine sediments, is an important part of the carbon cycle. The chemical composition of PyC is temperature dependent and levoglucosan is a source-specific burning marker used to trace low-temperature PyC. Levoglucosan associated to particulate material has been shown to be preserved during riverine transport and marine deposition in high- and mid-latitudes, but it is yet unknown if this is also the case for (sub)tropical areas, where 90% of global PyC is produced. Here, we investigate transport and deposition of levoglucosan in suspended and riverbed sediments from the Amazon River system and adjacent marine deposition areas. We show that the Amazon River exports negligible amounts of levoglucosan and that concentrations in sediments from the main Amazon tributaries are not related to long-term mean catchment-wide fire activity. Levoglucosan concentrations in marine sediments offshore the Amazon Estuary are positively correlated to total organic content regardless of terrestrial or marine origin, supporting the notion that association of suspended or dissolved PyC to biogenic particles is critical in the preservation of PyC. We estimate that 0.5-10 × 106 g yr-1 of levoglucosan is exported by the Amazon River. This represents only 0.5-10 ppm of the total exported PyC and thereby an insignificant fraction, indicating that riverine derived levoglucosan and low-temperature PyC in the tropics are almost completely degraded before deposition. Hence, we suggest caution in using levoglucosan as tracer for past fire activity in tropical settings near rivers.

Project for Universal Management of Airways - part 1: concept and methods.

Multiple professional groups and societies worldwide have produced airway management guidelines. These are typically targeted at the process of tracheal intubation by a particular provider group in a restricted category of patients and reflect practice preferences in a particular geographical region. The existence of multiple distinct guidelines for some (but not other) closely related circumstances, increases complexity and may obscure the underlying principles that are common to all of them. This has the potential to increase cognitive load; promote the grouping of ideas in silos; impair teamwork; and ultimately compromise patient care. Development of a single set of airway management guidelines that can be applied across and beyond these domains may improve implementation; promote standardisation; and facilitate collaboration between airway practitioners from diverse backgrounds. A global multidisciplinary group of both airway operators and assistants was assembled. Over a 3-year period, a review of the existing airway guidelines and multiple reviews of the primary literature were combined with a structured process for determining expert consensus. Any discrepancies between these were analysed and reconciled. Where evidence in the literature was lacking, recommendations were made by expert consensus. Using the above process, a set of evidence-based airway management guidelines was developed in consultation with airway practitioners from a broad spectrum of disciplines and geographical locations. While consistent with the recommendations of the existing English language guidelines, these universal guidelines also incorporate the most recent concepts in airway management as well as statements on areas not widely addressed by the existing guidelines. The recommendations will be published in four parts that respectively address: airway evaluation; airway strategy; airway rescue and communication of airway outcomes. Together, these universal guidelines will provide a single, comprehensive approach to airway management that can be consistently applied by airway practitioners globally, independent of their clinical background or the circumstances in which airway management occurs.

Risks to healthcare workers following tracheal intubation of patients with COVID-19: a prospective international multicentre cohort study.

Healthcare workers involved in aerosol-generating procedures, such as tracheal intubation, may be at elevated risk of acquiring COVID-19. However, the magnitude of this risk is unknown. We conducted a prospective international multicentre cohort study recruiting healthcare workers participating in tracheal intubation of patients with suspected or confirmed COVID-19. Information on tracheal intubation episodes, personal protective equipment use and subsequent provider health status was collected via self-reporting. The primary endpoint was the incidence of laboratory-confirmed COVID-19 diagnosis or new symptoms requiring self-isolation or hospitalisation after a tracheal intubation episode. Cox regression analysis examined associations between the primary endpoint and healthcare worker characteristics, procedure-related factors and personal protective equipment use. Between 23 March and 2 June 2020, 1718 healthcare workers from 503 hospitals in 17 countries reported 5148 tracheal intubation episodes. The overall incidence of the primary endpoint was 10.7% over a median (IQR [range]) follow-up of 32 (18-48 [0-116]) days. The cumulative incidence within 7, 14 and 21 days of the first tracheal intubation episode was 3.6%, 6.1% and 8.5%, respectively. The risk of the primary endpoint varied by country and was higher in women, but was not associated with other factors. Around 1 in 10 healthcare workers involved in tracheal intubation of patients with suspected or confirmed COVID-19 subsequently reported a COVID-19 outcome. This has human resource implications for institutional capacity to deliver essential healthcare services, and wider societal implications for COVID-19 transmission.

Late Holocene volcanic and anthropogenic mercury deposition in the western Central Andes (Lake Chungará, Chile).

Volcanism is one of the major natural processes emitting mercury (Hg) to the atmosphere, representing a significant component of the global Hg budget. The importance of volcanic eruptions for local-scale Hg deposition was investigated using analyses of Hg, inorganic elemental tracers, and organic biomarkers in a sediment sequence from Lake Chungará (4520 m a.s.l.). Environmental change and Hg deposition in the immediate vicinity of the Parinacota volcano were reconstructed over the last 2700 years, encompassing the pre-anthropogenic and anthropogenic periods. Twenty eruptions delivering large amounts of Hg (1 to 457 µg Hg m-2 yr-1 deposited at the timescale of the event) were locally recorded. Peaks of Hg concentration recorded after most of the eruptions were attributed to a decrease in sedimentation rate together with the rapid re-oxidation of gaseous elemental Hg and deposition with fine particles and incorporation into lake primary producers. Over the study period, the contribution of volcanic emissions has been estimated as 32% of the total Hg input to the lake. Sharp depletions in primary production occurred at each eruption, likely resulting from massive volcaniclastic inputs and changes in the lake-water physico-chemistry. Excluding the volcanic deposition periods, Hg accumulation rates rose from natural background values (1.9 ±â€¯0.5 µg m-2 yr-1) by a factor of 2.3 during the pre-colonial mining period (1400-900 yr cal. BP), and by a factor of 6 and 7.6, respectively, during the Hispanic colonial epoch (400-150 yr cal. BP) and the industrial era (~140 yr cal. BP to present). Altogether, the dataset indicates that lake primary production has been the main, but not limiting, carrier for Hg to the sediment. Volcanic activity and climate change are only secondary drivers of local Hg deposition relative to the magnitude of regional and global anthropogenic emissions.

The Airway App: exploring the role of smartphone technology to capture emergency front-of-neck airway experiences internationally.

In this exploratory study we describe the utility of smartphone technology for anonymous retrospective observational data collection of emergency front-of-neck airway management. The medical community continues to debate the optimal technique for emergency front-of-neck airway management. Although individual clinicians infrequently perform this procedure, hundreds are performed annually worldwide. Ubiquitous smartphone technology and internet connectivity have created the opportunity to collect these data. We created the 'Airway App', a smartphone application to capture the experiences of healthcare providers involved in emergency front-of-neck airway procedures. In the first 18-month period, 104 emergency front-of-neck airway management reports were received; 99 (95%) were internally valid and unique from 21 countries. Eighty-one (82%) were performed by non-surgeons and 63 (64%) were 'cannot intubate, cannot oxygenate' emergencies. Overall first-attempt success varied by technique; 45 scalpel-bougie cricothyroidotomy (37 first-attempt success), 25 surgical cricothyroidotomy (15 first-attempt success), eight cannula cricothyroidotomy (five first-attempt success), six wire-guided cricothyroidotomy (three first-attempt success) and 15 tracheostomy reports (11 first-attempt success). The most commonly reported positive human factors were good communication, good teamwork and/or skilled personnel. The most commonly reported negative human factors were fixation on multiple tracheal intubation attempts, delay in initiating emergency front-of-neck airway and/or the failure to plan for failure. Due to the anonymous nature of reporting, reports are open to recollection bias and spurious reporting. We conclude collection of data using a smartphone application is feasible and has the potential to expand our knowledge of emergency front-of-neck airway management.

Effect of palpable vs. impalpable cricothyroid membranes in a simulated emergency front-of-neck access scenario.

The Difficult Airway Society 2015 guidelines recommend and describe in detail a surgical cricothyroidotomy technique for the can't intubate, can't oxygenate (CICO) scenario, but this can be technically challenging for anaesthetists with no surgical training. Following a structured training session, 104 anaesthetists took part individually in a simulated can't intubate, can't oxygenate event using simulation and airway models to evaluate how well they could perform these front-of-neck access techniques. Main outcomes measures were: ability to correctly perform the technical steps; procedural time; and success rate. Outcomes were compared between palpable and impalpable cricothyroid membrane scenarios. Anaesthetists' technical abilities were good, as assessed by a video analysis checklist score. Mean (SD) procedural time was 44 (16) s and 65 (17) s for the palpable and impalpable cricothyroid membrane models, respectively (p ≤ 0.001). First-pass tracheal tube placement was obtained in 103 out of the 104 palpable cricothyroidotomies and in 101 out of the 104 impalpable cricothyroidotomies (p = 0.31). We conclude that anaesthetists can be trained to perform surgical front-of-neck access to an acceptable level of competence and speed when assessed using a simulator.

Evaluating the ORSIM® simulator for assessment of anaesthetists' skills in flexible bronchoscopy: aspects of validity and reliability.

BACKGROUND: Developing expertise in flexible bronchoscopy is limited by inadequate opportunities to train on difficult airways. The new ORSIM bronchoscopy simulator aims to address this by creating virtual patients with difficult airways. This study aims to provide evidence on the validity and reliability of the ORSIM for assessment of subjects on both normal and abnormal airway simulations. METHODS: Novice, trainee, and expert subjects performed seven simulations of varying difficulty and scored the perceived difficulty for each. Time to completion was measured. Three blinded raters independently scored videos of each subject's performance. We measured inter-rater agreement and the difference in raters' scores between subject groups. RESULTS: We recruited 28 study subjects, generating 196 videos for analysis. Expert subjects consistently completed the scenarios faster than novices. Overall performance scores showed significant differences between subject groups (P<0.0001). Inter-rater reliability of scores was >0.8. CONCLUSIONS: Our results provide initial evidence on the validity and reliability of the ORSIM bronchoscopy simulator, supporting its potential value in training and assessment.

Parker Flex-Tip or standard tracheal tube for percutaneous emergency airway access?

BACKGROUND: Percutaneous emergency airway access (PEAA) can be established utilising a scalpel, bougie and cuffed tracheal tube. The study compared the Parker Flex-Tip tracheal tube with a standard tracheal tube for PEAA in cadavers. We hypothesised that a standard tracheal tube would be more likely to advance over a bougie into the trachea during a PEAA procedure than a Parker Flex-Tip tracheal tube. METHODS: Three anaesthetists performed a PEAA with a scalpel, bougie and cuffed tracheal tube, 12 times each. Recorded times included: loading the tracheal tube onto the bougie and advancing the tube over the bougie to the skin, advancing the tube through the skin into the trachea and completion of the whole procedure. Subjective opinion regarding the ease of tube insertion was recorded by visual analogue scoring. RESULTS: Subjective opinion, overall time and time to complete each component of the procedure were not significantly affected by the type of tube used. The mean time for three novice anaesthetists to complete PEAA on a cadaver was 37.5 (8.8) s, after 1 h of training. In two of the 12 cadavers, the cricothyroid membrane could not be palpated or located with the scalpel. CONCLUSION: The Parker Flex-Tip tube and a standard tracheal tube perform equally well during PEAA procedures on adult cadavers.

Education in airway management.

In airway management, poor judgment, education and training are leading causes of patient morbidity and mortality. The traditional model of medical education, which relies on experiential learning in the clinical environment, is inconsistent and often inadequate. Curriculum change is underway in many medical organisations in an effort to correct these problems, and airway management is likely to be explicitly addressed as a clinical fundamental within any new anaesthetic curriculum. Competency-based medical education with regular assessment of clinical ability is likely to be introduced for all anaesthetists engaged in airway management. Essential clinical competencies need to be defined and improvements in training techniques can be expected based on medical education research. Practitioners need to understand their equipment and diversify their airway skills to cope with a variety of clinical presentations. Expertise stems from deliberate practice and a desire constantly to improve performance with a career-long commitment to education.

Failure to ventilate with supraglottic airways after drowning.

We report the failure of an i-gel and an Ambu AuraOnce supraglottic airway to ventilate a drowning victim. Failure was attributed to changes in lung physiology following submersion and inhalation of water that may have required ventilation pressures up to 40 cmH2O to treat the victim's hypoxaemia. The ease of use and rapid insertion of supraglottic airways without interrupting cardiac compression has prompted recommendations for their use during resuscitation. The relatively low leak pressures attainable from many supraglottic airways, however may cause inadequate lung ventilation and entrainment of air into the stomach when these devices are used in drowning victims.

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]).

Accuracy of surface landmark identification for cannula cricothyroidotomy.

Cannula cricothyroidotomy is recommended for emergency transtracheal ventilation by all current airway guidelines. Success with this technique depends on the accurate and rapid identification of percutaneous anatomical landmarks. Six healthy subjects underwent neck ultrasound to delineate the borders of the cricothyroid membrane. The midline and bisecting transverse planes through the membrane were marked with an invisible ink pen which could be revealed with an ultraviolet light. Eighteen anaesthetists were then invited to mark an entry point for cricothyroid membrane puncture. Only 32 (30%) attempts by anaesthetists accurately marked the skin area over the cricothyroid membrane. Of these only 11 (10%) marked over the centre point of the membrane. Entry point accuracy was not significantly affected by subjects' weight, height, body mass index, neck circumference or cricothyroid dimensions. Consultant and registrar anaesthetists were significantly more accurate than senior house officers at correctly identifying the cricothyroid membrane. Accuracy of percutaneously identifying the cricothyroid membrane was poor. Ultrasound may assist in identifying anatomical landmarks for cricothyroidotomy.

Thyromental distance measurement--fingers don't rule.

Thyromental distance (TMD) measurement is commonly used to predict difficult intubation. We surveyed anaesthetists to determine how this test was being performed. Comparative accuracy of ruler measurement and other forms of measurement were also assessed in a meta-analysis of published literature. Of respondents, 72% used fingers for TMD measurement and also considered three finger widths the minimum acceptable TMD. In terms of distance, the minimum acceptable TMD was felt to be 6.5 cm by 55% of respondents. However, the actual width of three fingers was (range) 4.6-7.0 cm (mean 5.9 cm), with significant differences between genders and between proximal and distal interphalangeal joints. The meta-analysis showed ruler measurement increased test sensitivity (48% (95% CI 43-53) vs 16% (95% CI 14-19) without a ruler), when predicting difficult intubation.