Browsing by Author "Hofmeyr, Ross"

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    Open Access
    Comparison of sonographic lung comet evaluation by an experienced ultrasonographer and novice in a high-altitude environment
    (2022) Vogts, Ferdinand Wilhelm; D'alton, Caroline; Hofmeyr, Ross
    Introduction: High altitude illness can be severely debilitating and sometimes fatal to those visiting higher altitudes. The condition is known to develop at altitudes above 2500m and has an incidence of between 50 and 60 percent. High altitude pulmonary oedema (HAPE) presents with signs and symptoms related to the accumulation of extravascular fluid in the lung, and early identification is critical to timeous intervention which in turn improves clinical outcomes. While increases in altitude result in physiological acclimatization, being able to identify when these changes become pathological is vital to early intervention. This process is facilitated with the use of lung ultrasound and the identification of sonographic artifacts called lung comets. This study was designed to establish whether a novice sonographer can perform effective assessment of lung ultrasound comet scores in comparison to an experienced sonographer in a high-altitude environment. An acceptable limit of agreement of 4 lung comets were identified a priori. This value was established based on the work done by Volpicelli et al. in 2006 who defined a positive lung ultrasound test as having at least 3 lung comets present at the time of examination.[49] In addition, various physiological and clinical parameters and their changes at different altitudes, ranging from 950 to 4662 meters above sea level, were assessed to aid the clinical interpretation and relevance of the ultrasound findings. Methods: Ten participants (six male; four female) underwent daily lung ultrasound scans at varying altitudes on Mount Kilimanjaro according to a standardized 8-zone protocol. One experienced sonographer scanned each participant, with his score then used as the “gold standard” for comparison, followed by a novice sonographer. The two sonographers were blinded to each other's findings during the data collection. Participants also undertook daily Lake Louise Scores, fingertip peripheral oxygen saturation readings and heart rates as part of the safety and clinical monitoring program on the mountain. Results: An exploratory Bland-Altman analysis revealed that compared to experts, novices showed little bias in identifying lung comets with sonography (mean difference 0,2 comets, 95% CI -0,2 to 0,6). Novice total comet scores typically fell within a range of approximately 3 above and below the expert score. There was a statistically significant difference in the total number of lung comets across the 7 recorded altitude points, χ2 (6) = 22.05, p < 0.01, as measured by the expert ultra sonographer. In addition, there was an overall statistically significant difference across the 7 recorded altitude points with regards to oxygen saturation (χ2 (6) = 33.22, p < 0.001), heart rate (as a percentage of maximum heart rate) (χ2 (6) = 12.83, p < 0.05) and Lake Louise Scores (χ2 (6) = 30.59, p < 0.001). Conclusion: Our results suggest that a novice sonographer is able to perform an effective assessment of lung ultrasound comet scores when compared to an experienced sonographer in a high-altitude environment. While the limited sample size of this study advocates for corroboration with future research projects on a larger scale, our preliminary findings encourage the use of a portable ultrasound machine as a potentially useful diagnostic tool in a wilderness expedition kit. The significant effects of high-altitude on physiological parameters are again emphasized, with our results in keeping with the findings of previous authors.
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    Effects of the Lubo cervical collar on airway patency in awake adults – A magnetic resonance imaging study
    (2022) Jaga, Rudhir; Hofmeyr, Ross
    Introduction: Intended for use by prehospital first responders, the Lubo TM cervical collar is an adjustable, radiolucent, single-use device that incorporates a mechanical jaw thrust mechanism. The combination enables non-invasive airway management in cases of trauma where cervical motion restriction is necessary. The potential benefits include use as an airway adjuvant maintaining upper airway patency, reducing provider task loading. The limited research on the device efficacy and safety requires further investigation. Methods: A randomized , crossover, interventional study was performed to compare mean differences in airway patency at the level of the uvula, epiglottis, tongue and soft palate with and without the Lubo collar in awake volunteers using magnetic resonance imaging (MRI). Fourteen participants each underwent two MRI scans of the upper airway: A control scan with no Lubo collar, and an intervention scan with the Lubo collar applied and jaw thrust mechanism activated. Two independent radiologists measured anterior-posterior diameter of the airway at four anatomical levels on the resulting MRI images. Results: There was no significant difference in mean airway diameter between the control and intervention measurements at any level. Mean (SD; 95% CI: p-value) differences were 0.9 mm (-2.38; 2.3 to 0.5; p= 0.17) at the epiglottis, 0.5 mm (1.6; -0.5 to 1.4; p= 0.29) at the soft palate, 0.2 mm (2.86; -1.4 to 1.9; p = 0.78) at the tongue, 0.4 mm (4.04; -1.9 to 2.7; p = 0.72) at the uvula. Conclusion: The Lubo TM airway collar did not show a significant change in upper airway patency at four anatomical levels measured in awake adult participants. Further research is required to investigate its clinical use in patients that are unable to maintain upper airway tone. Groups of interest would include trauma, obstructive sleep apnoea, obesity and patients under general anaesthesia.
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    Global Airway Management of the Unstable Cervical Spine Survey
    (2021) Stegmann, George Frederik; Hofmeyr, Ross; Llewellyn, Richard
    Background Rapid growth in optical and video devices for indirect visualisation of the airway has expanded the options for emergency and elective endotracheal intubation in patients with unstable fractures of the cervical spine. Aiming to ascertain whether video laryngoscopy (VL) has replaced awake flexible intubation (AFI) as the preferred technique for airway management, we conducted a global survey to evaluate current clinical practice. Methods After ethics approval, we created a questionnaire featuring one emergency and one urgent elective hypothetical patient with unstable injuries of the cervical spine. Target sample sizes per country were estimated using data from the World Federation of Societies of Anaesthesiologists' (WFSA) Global Anaesthesia Workforce Survey. Respondents were asked about their training, experience, airway skills, current clinical setting, and availability of airway equipment, as well as their preferred airway strategy in each case. The questionnaire was actively distributed for one year through the WFSA member societies and via social networks to physician anaesthesia providers (PAPs). Global and regional trends were assessed using descriptive statistics. Results Of a total of 1904 responses, 1153 (101 countries) were included in the final analysis. In the emergency case, 46.9% (95% confidence interval [CI]: 44.0–49.8%) of participants preferred VL and 39.8% (95% CI: 38.0-42.6%) chose AFI. In the urgent elective case, 51.3% (95% CI: 48.3-54.3%) selected VL as their preferred method, while 37.3% (95% CI: 34.4-40.2%) indicated AFI. Significant regional variations in preference were found. Conclusion The results suggest that practice in airway management of unstable cervical spine fractures is changing, and currently tends to favour VL over AFI. There is a statistically significant preference for VL in elective cases, traditionally considered to be a stronghold of AFI.
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    Hypoxaemia during tracheal intubation in patients with hypertensive disorders of pregnancy: analysis of data from an obstetric airway management registry
    (2021) Smit, Maretha Isabel; Hofmeyr, Ross; du Toit, Leon; Dyer, Robert A
    Background In South Africa, hypertensive disorders of pregnancy are the leading cause of maternal mortality. More than 50% of anaesthesia-related deaths are attributed to complications of airway management. We compared the prevalence and risk factors for hypoxaemia (SpO2<90%) during induction of general anaesthesia in parturients with and without hypertensive disorders of pregnancy. We hypothesised that hypertensive disorders of pregnancy are associated with desaturation during tracheal intubation. Methods Data from 402 cases in a multicentre obstetric airway management registry were analysed. The prevalence of peri-induction hypoxaemia (SpO2<90%) was compared in patients with and without hypertensive disorders of pregnancy. Quantile regression of SpO2 nadir was performed to identify confounding variables associated with, and mediators of hypoxaemia.Results In the cohort of 402 cases, hypoxaemia occurred in 19% with and 9% without hypertension (estimated risk difference, 10%; 95% CI 2% to 17%; P=0.005). Quantile regression demonstrated a lower SpO2 nadir associated with hypertensive disorders of pregnancy as body mass index increased. Room-air oxygen saturation, Mallampati grade, and number of intubation attempts were associated with the relationship. Conclusions Clinically significant oxygen desaturation during airway management occurred twice as often in patients with hypertensive disorders of pregnancy, compounded by increasing body mass index. Intermediary factors in the pathway from hypertension to hypoxaemia were also identified.
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    Innovation in low-cost video-laryngoscopy: Intubator V1-Indirect compared with Storz C-MAC in a simulated difficult airway
    (2021) De Villiers, Christiaan Tertius; Hofmeyr, Ross
    Background: Video laryngoscopy has directly impacted airway management, with numerous studies demonstrating its utility in clinical management of anatomically difficult airways. However, availability of video laryngoscopes in all clinical areas has been limited by cost. We used smartphone technology, miniature cameras and three-dimensional printing to design and create an innovative low-cost hyperangulated video laryngoscope. This has the potential to make the technique more widely available. Objectives: The aim of this study was to determine if time to intubation with the novel device was clinically equivalent to an existing gold-standard video laryngoscope (Storz CMAC with Dörges blade). Methods: We conducted a randomised, controlled, cross-over equivalence study with 100 skilled practitioners who had previous video laryngoscopy experience. Participants received instruction on the new device, and adequate opportunity to practice. Intubations were then performed in a randomised order on a mannikin simulating a difficult airway. Video recordings of each intubation were analysed by two independent investigators to determine time to intubation. A mean difference in intubation time of less than 10 seconds was determined a priori to denote clinical equivalence. Results: Mean difference in intubation time between the devices was 4.92 seconds, (two one-sided test 95%CI: 2.34 – 7.49 seconds). The innovative low-cost VL was thus clinically equivalent to the industry standard in a simulated difficult airway. Further testing in vivo in a clinical environment is needed. Conclusion: The results of this study show that a low-cost disposable hyperangulated video laryngoscope is clinically equivalent to the industry standard in a simulated difficult airway. In the context of the current global pandemic, video laryngoscopy has been advised in nearly all airway guidelines. Access to a low-cost VL which does not require reprocessing may be of great value.
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    Intubation during spinal motion restriction using the Lubo TM cervical collar a minikin simulation study
    (2022) Behari, Dinell; Hofmeyr, Ross
    Introduction: The Lubo TM collar is a cervical motion restriction device featuring a unique external jaw-thrust mechanism designed to provide non-invasive airway patency. In addition, tracheal intubation is facilitated by releasing an anterior chin strap; this allows better mouth opening than the previous generation of semi-rigid cervical collars. This study aimed to compare tracheal intubation using the Lubo TM collar combined with manual in-line stabilization (MILS) to intubation with MILS alone. The primary outcome was the time to successful intubation. Secondary outcomes compared intubation success rate, Cormack-Lehane grade, ease of intubation and dental trauma. Methods: A randomized, cross-over, equivalence study was performed. Eighty full-time physician anaesthesia providers were recruited. Participants performed tracheal intubation using direct laryngoscopy on a manikin under two different scenarios: with the Lubo TM collar and MILS applied, and with MILS and no cervical collar. The time to successful intubation was measured and compared using two-one-sided and paired t-tests. Results: Intubation times fell well within the a priori equivalence limits of 10 seconds, with a mean difference (95% CI) of 0.52 seconds (-1.30 to 2.56). There was no significant difference in intubation time with the Lubo TM collar (mean [SD] 19.2 [4.5] seconds) compared to the MILS alone group (19.7 [5.2] seconds). The overall success rate was 98.7% in the Lubo group and 100% in the MILS group. Adequate laryngoscopy views (Cormack-Lehane grades I to IIb) were equivalent between groups (Lubo 92.5% versus MILS alone 93.7%). Conclusion: In this manikin-based study, the time to intubation with the Lubo TM collar and MILS applied was equivalent to time to intubation with MILS alone, with similar intubating conditions. Thus, the Lubo TM collar and MILS may simplify airway management by reducing the number of steps required to perform intubation in patients requiring cervical motion restriction.
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    Predictors of difficult intubation in obstetric cohort of patients: an analysis of the prospective obstetric airway management registry (OBAMR) (substudy – R025/2018)
    (2020) Burger, Adrian; Hofmeyr, Ross
    Abstract Background: Hypoxaemia during tracheal intubation in obstetrics remains a lifethreatening complication. This study aimed to identify common clinical preinduction predictors of difficult intubation. Methods: A retrospective analysis was performed of data pertaining to tracheal intubation in patients requiring general anaesthesia for caesarean delivery, with a gestational age from 20 weeks, and until 7 days post-delivery, obtained from an obstetric airway management registry (ObAMR) at the University of Cape Town. Data was entered anonymously into a secure UCT REDCap database. Data categories were: patient and pregnancy characteristics, airway characteristics, details of management, and operator experience. The primary aim of the study was to identify anatomical and physiological risk factors for hypoxaemia. The primary outcome was defined as arterial desaturation to < 90% during obstetric airway management. For this purpose, multivariable binary logistic regression was performed. Hypoxaemia was thus used as a composite indicator of anatomical and physiological difficulty. Results: Data was collected for 1095 general anaesthetics in the ObAMR. Overall, 143/1091 of patients (13.1%, 95%CI 11.1 to 15.4%) experienced peripheral oxygen saturation below 90%. Univariate analysis showed that 91/142 (64.1%) of patients who desaturated were obese (body mass index [BMI]> 30 kg/m2 ), compared with 347/915 (37.9%) who were obese and did not experience desaturation (p< .001). A receiver operating curve (ROC) was constructed post hoc, which showed a cut-point for BMI of 29.76, and a sensitivity of 0.66, and specificity 0.62 for the prediction of hypoxaemia. Desaturation occurred in 17.0% of patients with hypertensive disorders of pregnancy, versus 11.0 % without (p=0.005). Increasing Mallampati class was associated with an increased incidence of hypoxaemia. The incidence of hypoxaemia was 25.8% for interns, compared with 8.0 % for consultant anaesthesiologists (p=0.005). In the multivariate analysis of factors associated with hypoxaemia, body mass index (p< 0.001), room air saturation prior to preoxygenation (p=0.008), and the presence of airway oedema (p=0.027), were independently associated with hypoxaemia. Conclusions: In this study, both anatomical and physiological predictors of hypoxaemia were identified. Using this concept, a predictive tool could be developed to aid in the identification of a difficult airway in obstetrics. Simple interventions such as face mask ventilation and the use of high flow nasal oxygenation, could be introduced to protect the parturient from the consequences of life-threatening hypoxaemia.