Brendan D. Higgins

Evaluation of intubation using the Airtraq® or Macintosh laryngoscope by anaesthetists in easy and simulated difficult laryngoscopy – a manikin study*

The Airtraq® Laryngoscope is a novel intubation device which allows visualisation of the vocal cords without alignment of the oral, pharyngeal and tracheal axes. We compared the Airtraq® with the Macintosh laryngoscope in simulated easy and difficult laryngoscopy. Twenty‐five anaesthetists were allowed up to three attempts to intubate the trachea in each of three laryngoscopy scenarios using a Laerdal® Intubation Trainer followed by five scenarios using a Laerdal SimMan® Manikin. Each anaesthetist then performed tracheal intubation of the normal airway a second time to characterise the learning curve. In the simulated easy laryngoscopy scenarios, there was no difference between the Airtraq® and the Macintosh in success of tracheal intubation. The time taken to intubate at the end of the protocol was significantly lower using the Airtraq® (9.5 (6.7) vs. 14.2 (7.4) s), demonstrating a rapid acquisition of skills. In the simulated difficult laryngoscopy scenarios, the Airtraq® was more successful in achieving tracheal intubation, required less time to intubate successfully, caused less dental trauma, and was considered by the anaesthetists to be easier to use.

Learning and performance of tracheal intubation by novice personnel: a comparison of the Airtraq® and Macintosh laryngoscope

Direct laryngoscopic tracheal intubation is taught to many healthcare professionals as it is a potentially lifesaving procedure. However, it is a difficult skill to acquire and maintain, and, of concern, the consequences of poorly performed intubation attempts are potentially serious. The Airtraq® Laryngoscope is a novel intubation device which may possess advantages over conventional direct laryngoscopes for use by novice personnel. We conducted a prospective trial with 40 medical students who had no prior airway management experience. Following brief didactic instruction, each participant took turns in performing laryngoscopy and intubation using the Macintosh and Airtraq devices under direct supervision. Each student was allowed up to three attempts to intubate in three laryngoscopy scenarios using a Laerdal® Intubation Trainer and one scenario in a Laerdal® SimMan® Manikin. They then performed tracheal intubation of the normal airway a second time to characterise the learning curve for each device. The Airtraq provided superior intubating conditions, resulting in greater success of intubation, particularly in the difficult laryngoscopy scenarios. In both easy and simulated difficult laryngoscopy scenarios, the Airtraq decreased the duration of intubation attempts, reduced the number of optimisation manoeuvres required, and reduced the potential for dental trauma. The Airtraq device showed a rapid learning curve and the students found it significantly easier to use. The Airtraq appears to be a superior device for novice personnel to acquire the skills of tracheal intubation.

Hypercapnic acidosis attenuates pulmonary epithelial wound repair by an NF-κB dependent mechanism

Background: Hypercapnic acidosis exerts protective effects in acute lung injury but may also slow cellular repair. These effects may be mediated via inhibition of nuclear factor-κB (NF-κB), a pivotal transcriptional regulator in inflammation and repair. Objectives: To determine the effects of hypercapnic acidosis in pulmonary epithelial wound repair, to elucidate the role of NF-κB and to examine the mechanisms by which these effects are mediated. Methods: Confluent small airway epithelial cell, human bronchial epithelial cell and type II alveolar A549 cell monolayers were subjected to wound injury under conditions of hypercapnic acidosis (pH 7.0, carbon dioxide tension (Pco2) 11 kPa) or normocapnia (pH 7.37, Pco2 5.5 kPa) and the rate of healing determined. Subsequent experiments investigated the role of hypercapnia versus acidosis and elucidated the role of NF-κB and mitogen-activated protein kinases. The roles of cellular mitosis versus migration and of matrix metalloproteinases in mediating these effects were then determined. Results: Hypercapnic acidosis reduced wound closure (mean (SD) 33 (6.3)% vs 64 (5.9)%, p<0.01) and reduced activation of NF-κB compared with normocapnia. Buffering of the acidosis did not alter this inhibitory effect. Prior inhibition of NF-κB activation occluded the effect of hypercapnic acidosis. Inhibition of ERK, JNK and P38 did not modulate wound healing. Hypercapnic acidosis reduced epithelial cell migration but did not alter mitosis, and reduced matrix metalloproteinase-1 while increasing concentrations of tissue inhibitor of metalloproteinase-2. Conclusions: Hypercapnic acidosis inhibits pulmonary epithelial wound healing by reducing cell migration via an NF-κB dependent mechanism that may involve alterations in matrix metalloproteinase activity.

Retention of tracheal intubation skills by novice personnel: a comparison of the Airtraq and Macintosh laryngoscopes.

Direct laryngoscopic tracheal intubation is a potentially lifesaving manoeuvre, but it is a difficult skill to acquire and to maintain. These difficulties are exacerbated if the opportunities to utilise this skill are infrequent, and by the fact that the consequences of poorly performed intubation attempts may be severe. Novice users find the Airtraq® laryngoscope easier to use than the conventional Macintosh laryngoscope. We therefore wished to determine whether novice users would have greater retention of intubation skills with the Airtraq® rather than the Macintosh laryngoscope. Twenty medical students who had no prior airway management experience participated in this study. Following brief didactic instruction, each took turns performing laryngoscopy and intubation using the Macintosh and Airtraq® devices in easy and simulated difficult laryngoscopy scenarios. The degree of success with each device, the time taken to perform intubation and the assistance required, and the potential for complications were then assessed. Six months later, the assessment process was repeated. No didactic instruction or practice attempts were provided on this latter occasion. Tracheal intubation skills declined markedly with both devices. However, the Airtraq® continued to provide better intubating conditions, resulting in greater success of intubation, with fewer optimisation manoeuvres required, and reduced potential for dental trauma, particularly in the difficult laryngoscopy scenarios. The substantial decline in direct laryngoscopy skills over time emphasise the need for continued reinforcement of this complex skill.

Hypercapnic acidosis attenuates shock and lung injury in early and prolonged systemic sepsis

Objective:To investigate whether acute hypercapnic acidosis—induced by adding CO2 to inspired gas—would protect against severe systemic sepsis-induced lung and systemic organ injury resulting from cecal ligation and puncture. Acute hypercapnic acidosis protects against lung injury after both nonseptic and early pneumonia-induced lung injury. In contrast, prolonged hypercapnia worsens pneumonia-induced lung injury. The effects of hypercapnia and acidosis in the setting of systemic sepsis remain to be determined. Design:Prospective randomized animal study. Setting:University research laboratory. Subjects:Adult male Sprague-Dawley rats. Interventions:In the early systemic sepsis series, post induction of anesthesia and tracheostomy placement, animals were randomized to normocapnia (Fico2 = 0.00, n = 12) or hypercapnic acidosis (Fico2 = 0.05, n = 12). Cecal ligation and puncture were performed and the animals were ventilated for 3 hrs. In the prolonged systemic sepsis series, rats were anesthetized, cecal ligation and puncture were performed, and the animals were allowed to recover. The animals were then randomized to housing under conditions of environmental normocapnia (Fico2 = 0.00, n = 20) or hypercapnia (Fico2 = 0.08, n = 20). After 96 hrs, the animals were reanesthetized, and the severity of lung and hemodynamic injury was assessed. Results:In early systemic sepsis, hypercapnic acidosis attenuated the development and severity of hypotension, and reduced lactate accumulation and the decrement in central venous oxyhemoglobin levels, compared with normocapnia. Hypercapnic acidosis reduced bronchoalveolar lavage neutrophil infiltration, and lung wet/dry weight ratios. In prolonged systemic sepsis, hypercapnic acidosis reduced histologic indices of lung injury. There was no evidence that hypercapnia worsened prolonged systemic sepsis-induced lung injury. Hypercapnic acidosis did not alter lung or systemic bacterial loads in early or prolonged systemic sepsis. Conclusion:Hypercapnic acidosis exerts beneficial effects in early and prolonged cecal ligation and puncture-induced polymicrobial systemic sepsis.

A comparison of the Glidescope®, Pentax AWS®, and Macintosh laryngoscopes when used by novice personnel: a manikin study

PurposeDirect laryngoscopic tracheal intubation is a potentially lifesaving procedure, but a difficult skill to acquire and maintain. The consequences of poorly performed intubation attempts are potentially severe. The Pentax AWS® and the Glidescope® are indirect laryngoscopes that may require less skill to use. We therefore hypothesized that AWS® and Glidescope® would prove superior to the Macintosh laryngoscope when used by novices in the normal and simulated difficult airway.MethodsIn this prospective randomized crossover trial following standardized didactic instruction, medical students with no prior experience of laryngoscopy performed tracheal intubation using each device. Each student was allowed up to three attempts to intubate in a Laerdal® Intubation Trainer in two laryngoscopy scenarios and in a Laerdal® SimMan® manikin in one scenario. The students then performed tracheal intubation of the normal airway a second time to characterize the learning curve for each device.ResultsThe Pentax AWS® provided better intubation conditions than the Glidescope® or the Macintosh, resulting in greater success of intubation, particularly in the difficult laryngoscopy scenarios. The Glidescope® demonstrated advantages over the Macintosh, particularly in the more difficult scenarios. Both the AWS® and the Glidescope® decreased the duration of intubation attempts, reduced the number of maneuvers required, and reduced the potential for dental trauma. In direct comparisons, the AWS® provided the best intubation conditions.ConclusionsThe Pentax AWS® appears to constitute a better alternative to the Macintosh for novice personnel to acquire the skills of tracheal intubation.RésuméObjectifL’intubation trachéale par laryngoscopie directe est une procédure potentiellement salutaire, mais il s’agit également d’une compétence difficile à acquérir et à maintenir. Les conséquences de tentatives d’intubation mal réalisées sont potentiellement graves. Le Pentax AWS® et le Glidescope® sont des laryngoscopes indirects qui pourraient nécessiter une compétence moindre. Ainsi, nous avons émis l’hypothèse que l’AWS® et le Glidescope® donneraient de meilleurs résultats que le laryngoscope Macintosh lors de leur utilisation par du personnel inexpérimenté pour l’intubation de voies aériennes normales ou rendues difficiles par simulation.MéthodeDans cette étude croisée randomisée et prospective qui a été menée à la suite d’une formation didactique standard, des étudiants en médecine n’ayant pas d’expérience antérieure en matière de laryngoscopie ont réalisé une intubation trachéale à l’aide de chacun des appareils. Chaque étudiant avait droit à un maximum de trois tentatives d’intubation sur un simulateur d’intubation Laerdal® dans le cadre de deux scénarios de laryngoscopie, dont l’un sur un mannequin Laerdal® SimMan®. Les étudiants ont ensuite réalisé une seconde intubation trachéale dans une voie aérienne normale afin de déterminer la courbe d’apprentissage de chaque appareil.RésultatsLe Pentax AWS® a procuré de meilleures conditions d’intubation que le Glidescope® ou le Macintosh, ce qui a eu pour résultat un taux de réussite de l’intubation plus élevé et ce, particulièrement dans les situations de laryngoscopie difficile. Le Glidescope® a démontré des avantages par rapport au Macintosh, notamment dans les situations de laryngoscopie plus difficile. L’AWS® et le Glidescope® ont permis de réduire la durée des tentatives d’intubation, le nombre de manœuvres nécessaires, ainsi que le potentiel d’un traumatisme dentaire. En comparaison directe, l’AWS® était le laryngoscope procurant les meilleures conditions d’intubation.ConclusionLe laryngoscope Pentax AWS® semble constituer une meilleure alternative au Macintosh pour permettre au personnel inexpérimenté d’acquérir les compétences nécessaires à l’intubation trachéale.

Hypercapnic acidosis attenuates severe acute bacterial pneumonia-induced lung injury by a neutrophil-independent mechanism

Objective:Deliberate induction of hypercapnic acidosis protects against lung injury after nonseptic lung injury. In contrast, concerns exist regarding the effects of hypercapnic acidosis in the setting of severe pulmonary sepsis. The potential for the effects of hypercapnic acidosis to be neutrophil-mediated remains to be determined. We investigated whether hypercapnic acidosis—induced by adding CO2 to inspired gas—would protect against severe acute lung injury induced by pulmonary Escherichia coli instillation and the role of neutrophils in mediating this effect. Design:Prospective randomized animal study. Setting:University Research Laboratory. Subjects:Adult male Sprague-Dawley rats. Interventions:In series 1, after induction of anesthesia and tracheostomy placement, animals were randomized to normocapnia (Fico2 0.00, n = 12) or hypercapnic acidosis (Fico2 0.05, n = 12). E. coli (0.5–3.0 × 1015 colony-forming units) was instilled intratracheally and the animals were ventilated for 6 hrs to allow a severe acute lung injury to evolve. In series 2, animals were randomized to neutrophil depletion or nondepletion before bacterial instillation, in a three-group design: normocapnia alone (Normo + polymorphonuclear neutrophils [PMN], n = 9), normocapnia with neutrophil depletion (Normo − PMN, n = 9), or hypercapnic acidosis with neutrophil depletion (hypercapnic acidosis − PMN, n = 9). After intratracheal E. coli administration these animals were also ventilated for 6 hrs. Results:Hypercapnic acidosis protected against evolving pneumonia-induced acute lung injury, attenuating the increase in airway pressure, and the decrement in lung compliance and arterial Po2. However, hypercapnic acidosis did not reduce histologic injury. Hypercapnic acidosis also protected against evolving pneumonia-induced acute lung injury in the presence of neutrophil depletion, reducing both physiologic and histologic indices of lung injury. Conclusions:Hypercapnic acidosis reduces indices of intratracheal E. coli induced lung injury by a mechanism that seems to be neutrophil-independent.

Permissive hypercapnia: role in protective lung ventilatory strategies.

PURPOSE OF REVIEW Hypercapnia is a central component of current protective ventilatory strategies. This review aims to present and interpret data from recent clinical and experimental studies relating to hypercapnia and its role in protective ventilatory strategies. RECENT FINDINGS Increasing clinical evidence supports the use of permissive hypercapnia, particularly in acute lung injury/acute respiratory distress syndrome, status asthmaticus, and neonatal respiratory failure. However, there are no clinical data examining the contribution of hypercapnia per se to protective ventilatory strategies. Recent experimental studies provide further support for the concept of therapeutic hypercapnia, whereby deliberately elevated PaCO2 may attenuate lung and systemic organ injury. CO2 administration attenuates experimental acute lung injury because of adverse ventilatory strategies, mesenteric ischemia reperfusion, and pulmonary endotoxin instillation. Hypercapnic acidosis attenuates key effectors of the inflammatory response and reduces lung neutrophil infiltration. At the genomic level, hypercapnic acidosis attenuates the activation of nuclear factor-kappaB, a key regulator of the expression of multiple genes involved in the inflammatory response. The physiologic effects of hypercapnia, both beneficial and potentially deleterious, are increasingly well understood. In addition, reports suggest that humans can tolerate extreme levels of hypercapnia for relatively prolonged periods without adverse effects. SUMMARY The potential for hypercapnia to contribute to the beneficial effects of protective lung ventilatory strategies is clear from experimental studies. However, the optimal ventilatory strategy and the precise contribution of hypercapnia to this strategy remain unclear. A clearer understanding of its effects and mechanisms of action is central to determining the safety and therapeutic utility of hypercapnia in protective lung ventilatory strategies.

Hypercapnic Acidosis Attenuates Lung Injury Induced by Established Bacterial Pneumonia

Background: Hypercapnic acidosis protects against lung injury after ischemia–reperfusion, endotoxin-induced and ventilation-induced lung injury. The effects of hypercapnic acidosis in the setting of established pulmonary sepsis are not known. The authors investigated whether hypercapnic acidosis—induced by adding carbon dioxide to inspired gas—would be beneficial or deleterious in established Escherichia coli pneumonia in an in vivo model, in the presence and absence of antibiotic therapy. Methods: Adult male Sprague-Dawley rats were anesthetized and ventilated. In the first set of experiments, rats were anesthetized, E. coli (5–6.4 × 109/ml colony-forming units) was instilled intratracheally, and the animals were allowed to recover. After 6 h, during which time a severe pneumonia developed, they were reanesthetized and randomly assigned to normocapnia (fraction of inspired carbon dioxide [Fico2] = 0.00, n = 10) or hypercapnic acidosis (Fico2 = 0.05, n = 10). The second set of experiments was performed in a manner identical to that of series 1, but all rats (n = 10 per group) were given intravenous ceftriaxone (30 mg/kg) at randomization. All animals received normocapnia or hypercapnic acidosis for 6 h, and the severity of lung injury was assessed. Results: In the absence of antibiotic therapy, hypercapnic acidosis reduced the pneumonia-induced increase in peak airway pressure and the decrease in static lung compliance compared with control conditions. In the presence of antibiotic therapy, which substantially reduced lung bacterial counts, hypercapnic acidosis significantly attenuated the extent of pneumonia-induced histologic injury. Conclusions: Hypercapnic acidosis reduced the magnitude of the lung injury induced by established E. coli pneumonia.

Comparison of the Glidescope® and Pentax AWS® laryngoscopes to the Macintosh laryngoscope for use by Advanced Paramedics in easy and simulated difficult intubation

BackgroundIntubation of the trachea in the pre-hospital setting may be lifesaving in severely ill and injured patients. However, tracheal intubation is frequently difficult to perform in this challenging environment, is associated with a lower success rate, and failed tracheal intubation constitutes an important cause of morbidity. Novel indirect laryngoscopes, such as the Glidescope® and the AWS® laryngoscopes may reduce this risk.MethodsWe compared the efficacy of these devices to the Macintosh laryngoscope when used by 25 Advanced Paramedics proficient in direct laryngoscopy, in a randomized, controlled, manikin study. Following brief didactic instruction with the Glidescope® and the AWS® laryngoscopes, each participant took turns performing laryngoscopy and intubation with each device, in an easy intubation scenario and following placement of a hard cervical collar, in a SimMan® manikin.ResultsBoth the Glidescope® and the AWS® performed better than the Macintosh, and demonstrate considerable promise in this context. The AWS® had the least number of dental compressions in all three scenarios, and in the cervical spine immobilization scenario it required fewer maneuvers to optimize the view of the glottis.ConclusionThe Glidescope® and AWS® devices possess advantages over the conventional Macintosh laryngoscope when used by Advanced Paramedics in normal and simulated difficult intubation scenarios in this manikin study. Further studies are required to extend these findings to the clinical setting.