Comparison of different methods of ventilation via cannula cricothyroidotomy in a trachea-lung model

Impact of simulation-based training on bougie-assisted cricothyrotomy technique: a quasi-experimental study

BACKGROUND

Cricothyrotomy is a lifesaving surgical technique in critical airway events. However, a large proportion of anesthesiologists have little experience with cricothyrotomy due to its low incidence. This study aimed to develop a multisensory, readily available training curriculum for learning cricothyrotomy and evaluate its training effectiveness.

METHODS

Seventy board-certificated anesthesiologists were recruited into the study. Participants first viewed an instructional video and observed an expert performing the bougie-assisted cricothyrotomy on a self-made simulator. They were tested before and after a one-hour practice on their cricothyrotomy skills and evaluated by a checklist and a global rating scale (GRS). Additionally, a questionnaire survey regarding participants' confidence in performing cricothyrotomy was conducted during the training session.

RESULTS

The duration to complete cricothyrotomy was decreased from the pretest (median = 85.0 s, IQR = 72.5-103.0 s) to the posttest (median = 59.0 s, IQR = 49.0-69.0 s). Furthermore, the median checklist score was increased significantly from the pretest (median = 30.0, IQR = 27.0-33.5) to the posttest (median = 37.0, IQR = 35.5-39.0), as well as the GRS score (pretest median = 22.5, IQR = 18.0-25.0, posttest median = 32.0, IQR = 31.0-33.5). Participants' confidence levels in performing cricothyrotomy also improved after the curriculum.

CONCLUSION

The simulation-based training with a self-made simulator is effective for teaching anesthesiologists to perform cricothyrotomy.

A comparison of cannula insufflation device performance for emergency front of neck airway

BACKGROUND

Pediatric emergency front of neck airway guidelines recommend oxygenation via cannula cricothyroidotomy or tracheotomy.

AIM

The primary aim was to measure test lung pressures and volumes generated by cannula insufflation devices recommended for emergency front of neck airway compared with a pressure limit of 50 cm H₂ O and volume limit of 20 ml/kg. The secondary aim was to calculate pressure and volume variability. The primary end point was test lung expansion.

METHOD

Adult, child, and infant airway models, each with three degrees of upper airway obstruction, were oxygenated using six cannula insufflation devices: 3-way stopcock, Rapid-O₂ , Manujet, Enk oxygen flow modulator, Ventrain, and self-inflating bags. Test lung pressures and volumes were recorded.

RESULTS

Pressures and volumes from all devices were highly variable, despite oxygen flow calibration and strict adherence to oxygen insufflation protocols. With upper airway occlusion, pressures >50 cm H₂ 0 were produced by Rapid-O₂ and Enk oxygen flow meter in adult and infant lungs, 3-way stopcock in adult and child lungs, and Manujet in all lung sizes. Ventrain produced acceptable pressures <35 cm H₂ O in all models. Test lung volumes >20 ml/kg were recorded in airway models with fully obstructed proximal airways using Rapid-O₂ and Enk oxygen flow meter in infant lungs, and Manujet in all lung sizes. Rapid-O₂ produced lung volumes >20 ml/kg in the infant model with partially obstructed and open upper airways. Test lung volumes >20 ml/kg were produced by the 3-way stopcock in adult, child, and infant models. Insufflation was unsuccessful with the self-inflating bag. Ventrain produced acceptable volumes <7 ml/kg in all airway models.

CONCLUSION

Rapid-O₂ , Enkoxygen flow meter, Manujet, and 3-way stopcock oxygenation devices produced highly variable and excessive airway pressures and volumes in models with obstructed upper airways. Self-inflating bag insufflation was unsuccessful. Ventrain was the only device that insufflated oxygen with acceptable pressures and volumes in adult, child, and infant airway models with any degree of airway obstruction.

Ventilation strategies for front of neck airway rescue: an in silico study

BACKGROUND

During induction of general anaesthesia a 'cannot intubate, cannot oxygenate' (CICO) situation can arise, leading to severe hypoxaemia. Evidence is scarce to guide ventilation strategies for small-bore emergency front of neck airways that ensure effective oxygenation without risking lung damage and cardiovascular depression.

METHODS

Fifty virtual subjects were configured using a high-fidelity computational model of the cardiovascular and pulmonary systems. Each subject breathed 100% oxygen for 3 min and then became apnoeic, with an obstructed upper airway. When arterial haemoglobin oxygen saturation reached 40%, front of neck airway access was simulated with various configurations. We examined the effect of several ventilation strategies on re-oxygenation, pulmonary pressures, cardiovascular function, and oxygen delivery.

RESULTS

Re-oxygenation was achieved in all ventilation strategies. Smaller airway configurations led to dynamic hyperinflation for a wide range of ventilation strategies. This effect was absent in airways with larger internal diameter (≥3 mm). Intrapulmonary pressures increased quickly to supra-physiological values with the smallest airways, resulting in pronounced cardio-circulatory depression (cardiac output <3 L min^-1 and mean arterial pressure <60 mm Hg), impeding oxygen delivery (<600 ml min^-1). Limiting tidal volume (≤200 ml) and ventilatory frequency (≤8 bpm) for smaller diameter cannulas reduced dynamic hyperinflation and gas trapping, preventing cardiovascular depression.

CONCLUSIONS

Dynamic hyperinflation can be demonstrated for a wide range of front of neck airway cannulae when the upper airway is obstructed. When using small-bore cannulae in a CICO situation, ventilation strategies should be chosen that prevent gas trapping to prevent severe adverse events including cardio-circulatory depression.

Randomised comparison of Enk™ and Manujet™ for emergency tracheal oxygenation with a high-fidelity full-scale simulation

BACKGROUND

We aimed to compare time and difficulties of emergency tracheal oxygenation with Enk™ or Manujet™ by anaesthesiologists or intensivists, in a full-scale cannot ventilate and intubate scenarios on a SimMan3G™ high-fidelity patient simulator.

METHODS

After ethical committee approval and written informed consent, teams (two to three learners with at least one physician senior) participating at a difficult airway training with a massive sublingual haematoma scenario, were randomised in Enk™ (E) group (29 teams, 76 learners) and Manujet™ (M) group (31 teams, 84 learners) according to the device at disposal. Main criterion was time between taking device in hand and first insufflation delay. Data were medians [25-75%].

RESULTS

The handling-insufflation time was shorter with Enk™ than with Manujet™ (74 [54-87] seconds versus 95 [73-123] seconds (s), P=0.0112). The team number performing insufflation within one minute after device handling was higher in the E group (8, 27.6%) than in the M group (2, 6.4%) (P=0.0392) as well as the team number performing insufflation within 90s in the E group (22, 75.09%) than in the M group (12, 38.7%) (P=0.0047). In E group, 75% of learners reported no difficulty versus 58.8% in M group (P=0.0443). Insufflation frequency was high in both groups and higher than 12min^-1 in 51.7% of the teams.

CONCLUSION

In a simulation context, Enk™ use is faster and easier. A high insufflation rate was also in favour of Enk™ that generates lower airway pressures.

Pulmonary effects of expiratory-assisted small-lumen ventilation during upper airway obstruction in pigs

Novel devices for small-lumen ventilation may enable effective inspiration and expiratory ventilation assistance despite airway obstruction. In this study, we investigated a porcine model of complete upper airway obstruction. After ethical approval, we randomly assigned 13 anaesthetised pigs either to small-lumen ventilation following airway obstruction (n = 8) for 30 min, or to volume-controlled ventilation (sham setting, n = 5). Small-lumen ventilation enabled adequate gas exchange over 30 min. One animal died as a result of a tension pneumothorax in this setting. Redistribution of ventilation from dorsal to central compartments and significant impairment of the distribution of ventilation/perfusion occurred. Histopathology demonstrated considerable lung injury, predominantly through differences in the dorsal dependent lung regions. Small-lumen ventilation maintained adequate gas exchange in a porcine airway obstruction model. The use of this technique for 30 min by inexperienced clinicians was associated with considerable end-expiratory collapse leading to lung injury, and may also carry the risk of severe injury.

Transtracheal ventilation with a novel ejector-based device (Ventrain) in open, partly obstructed, or totally closed upper airways in pigs

BACKGROUND

Transtracheal access and subsequent jet ventilation are among the last options in a 'cannot intubate-cannot oxygenate' scenario. These interventions may lead to hypercapnia, barotrauma, and haemodynamic failure in the event of an obstructed upper airway. The aim of the present study was to evaluate the efficacy and the haemodynamic effects of the Ventrain, a manually operated ventilation device that provides expiratory ventilation assistance. Transtracheal ventilation was carried out with the Ventrain in different airway scenarios in live pigs, and its performance was compared with a conventional jet ventilator.

METHODS

Pigs with open, partly obstructed, or completely closed upper airways were transtracheally ventilated either with the Ventrain or by conventional jet ventilation. Airway pressures, haemodynamic parameters, and blood gases obtained in the different settings were compared.

RESULTS

Mean (SD) alveolar minute ventilation as reflected by arterial partial pressure of CO2 was superior with the Ventrain in partly obstructed airways after 6 min in comparison with traditional manual jet ventilation [4.7 (0.19) compared with 7.1 (0.37) kPa], and this was also the case in all simulated airway conditions. At the same time, peak airway pressures were significantly lower and haemodynamic parameters were altered to a lesser extent with the Ventrain.

CONCLUSIONS

The results of this study suggest that the Ventrain device can ensure sufficient oxygenation and ventilation through a small-bore transtracheal catheter when the airway is open, partly obstructed, or completely closed. Minute ventilation and avoidance of high airway pressures were superior in comparison with traditional hand-triggered jet ventilation, particularly in the event of complete upper airway obstruction.

Rescue ventilation through a small-bore transtracheal cannula in severe hypoxic pigs using expiratory ventilation assistance

BACKGROUND

Suction-generated expiratory ventilation assistance (EVA) has been proposed as a way to facilitate bidirectional ventilation through a small-bore transtracheal cannula (TC). In this study, we investigated the efficiency of ventilation with EVA for restoring oxygenation and ventilation in a pig model of acute hypoxia.

METHODS

Six pigs (61-76 kg) were anesthetized and ventilated (intermittent positive pressure ventilation) via a cuffed endotracheal tube (ETT). Monitoring lines were placed, and a 75-mm long, 2-mm inner diameter TC was inserted. After the baseline recordings, the ventilator was disconnected. After 2 minutes of apnea, reoxygenation with EVA was initiated through the TC and continued for 15 minutes with the ETT occluded. In the second part of the study, the experiment was repeated with the ETT either partially obstructed or left open. Airway pressures and hemodynamic data were recorded, and arterial blood gases were measured. Descriptive statistical analysis was performed.

RESULTS

With a completely or partially obstructed upper airway, ventilation with EVA restored oxygenation to baseline levels in all animals within 20 seconds. In a completely obstructed airway, PaCO2 remained stable for 15 minutes. At lesser degrees of airway obstruction, the time to reoxygenation was delayed. Efficacy probably was limited when the airway was completely unobstructed, with 2 of 6 animals having a PaO2 <85 mm Hg even after 15 minutes of ventilation with EVA and a mean PaCO2 increased up to 90 mm Hg.

CONCLUSIONS

In severe hypoxic pigs, ventilation with EVA restored oxygenation quickly in case of a completely or partially obstructed upper airway. Reoxygenation and ventilation were less efficient when the upper airway was completely unobstructed.

Invasive and surgical procedures in pre-hospital care: what is the need?

BACKGROUND

On occasion, advanced invasive procedures in pre-hospital care can be life saving. This study aimed to identify the contemporary use of these procedures on a regional doctor-led air ambulance unit, and to define the need, skill set and training requirements for a regional pre-hospital team in the UK.

METHODS

Mission data were recorded prospectively and the database reviewed to identify invasive procedures over a 76-month period. These cases were reviewed with indications, mechanism of injury, presence of cardiac arrest at any time point (±return of spontaneous circulation) and procedural failure or morbidity.

RESULTS

Two hundred and thirty-five procedures were performed: 16 for injuries affecting the airway, 111 for breathing and 108 for circulation. Almost a third of patients in cardiac arrest regained spontaneous circulation. Procedures performed increased fivefold from 2003 to 2009, with a marked increase in the use of thoracostomy and intra-osseous access. Procedural failure or inadequacy was high with needle cricothyroidotomy, needle chest decompression and early intra-osseous access experience.

CONCLUSIONS

A steady increase in the number of procedures was observed over time. Less invasive methods of airway and breathing support were frequently inadequate, though definitive surgical airway or chest decompression was effective each time it was performed. Thoracotomy was performed infrequently. There are implications for the training of pre-hospital doctors who work in the majority of the UK.

Jet or intensive care unit ventilator during simulated percutaneous transtracheal ventilation: a lung model study

BACKGROUND

Percutaneous transtracheal ventilation (PTV) via a jet ventilator (PTJV) is considered a rescue technique in difficult airway management. However, whether a conventional ventilator can generate adequate ventilation via PTV is not known. Our goal was to evaluate the tidal volume (V(T)) generated by a conventional ventilator during simulated PTV compared with PTJV in a lung model.

METHODS

A lung model simulating an adult lung was used. A catheter was inserted through the artificial trachea and connected to either a jet ventilator or a conventional ventilator. The direction of catheter insertion was perpendicular to the trachea, pointing towards the lung and away from the lung. The jet ventilator was operated at 344.7 kPa. The conventional ventilator was operated in the pressure mode at peak inspiratory pressures of 40-90 cm H(2)O.

RESULTS

The jet ventilator generated larger V(T) [817 (336) ml] when the catheter was pointing towards the lung than when pointing away from the lung or perpendicular to the trachea [121 (41) and 69 (24) ml, respectively, P<0.01]. With the conventional ventilator, changes in V(T) at different direction of catheter insertion were much less [222 (81) ml catheter pointing towards the lung, 229 (121) ml perpendicular to the trachea, and 187 (97) ml away from the lung].

CONCLUSIONS

Our result demonstrated that PTJV was effective only when the catheter was pointing towards the lung and requires high operating pressure. A conventional ventilator can generate reasonable minute ventilation through the transtracheal catheter less dependent on directions of catheter insertion and should be considered during emergent PTV.