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

In the Nick of Time-Emergency Front-of-Neck Airway Access

Emergency front-of-neck access refers to all techniques that deliver oxygen into the airway lumen through the anterior neck structures and encompasses access both through the cricothyroid membrane and the tracheal wall. There has yet to be a universal agreement regarding the preferred technique. A surgical incision is currently the most common approach in prehospital and in-hospital care. This review intends to review and summarize the existing clinical, basic science, and societal guidelines for eFONA.

Ventilation through a straw

Transtracheal jet ventilation can be used for resuscitation of partial airway obstruction. A prerequisite for jet ventilation is that at least a minimum airway opening for gas escape must be secured. Therefore, another option should be considered in cases of complete airway obstruction. The following methods or devices has been used under cricothyrotomy using an intravenous cannula: 1) Ambu (bag valve mask) bagging, 2) Ventrain®, 3) Rapid-O2 oxygen insufflation device (Rapid-O2), and 4) jet ventilation using a dual lumen catheter. During Ambu bagging, extraordinarily high insufflation pressure is required to force oxygen through the cannula. When using a 12-G cannula, long and slow positive-pressure ventilations (10–12 breaths/min) are required, which makes it extremely difficult to compress the bag. Therefore, a 10-G or larger is recommended. Ventrain® is an expiratory assist device capable of forcibly expelling insufflated oxygen through a transtracheal cannula. It is recommended to adjust the inspiratory and expiratory times while observing the chest wall movements. Rapid-O2 is a rescue oxygenation device with adequate ventilation of less importance; therefore, the resulting hypercarbia is inevitable. A 14-G cannula is used. Lastly, jet ventilation using a dual-lumen catheter with a 16-G inflow lumen and 10-G outflow lumen was used to obtain both oxygenation and ventilation. However, the addition of the outer diameters of 16-G and 10-G results in an outer diameter of 5.1 mm, which is too large to puncture the cricothyroid membrane. In conclusion, Ventrain® is considered the most ideal device for use among the devices developed to date.

Cannula cricothyroidotomy in the impalpable neck: An observational study of simulated 'can't intubate, can't oxygenate' scenarios by teams following a cannula-first algorithm in live anaesthetised pigs

Live animal models can be used to train anaesthetists to perform emergency front-of-neck-access. Cannula cricothyroidotomy success reported in previous wet lab studies contradicts human clinical data. This prospective, observational study reports success of a cannula-first 'can't intubate, can't oxygenate' algorithm for impalpable anatomy during high fidelity team simulations using live, anaesthetised pigs.Forty-two trained anaesthesia teams were instructed to follow the Royal Perth Hospital can't intubate, can't oxygenate algorithm to re-oxygenate a desaturating pig with impalpable neck anatomy (mean (standard deviation, SD) 16.2 (3.5) kg); mean (SD) tracheal internal diameter 11 (1.4) mm. Teams were informed that failure would prompt veterinary-led euthanasia.All teams performed percutaneous cannula cricothyroidotomy as the initial technique, with a median (interquartile range, IQR (range)) start time of 42 (35-50 (24-93)) s. First-pass percutaneous cannula success was 29% to both insufflate tracheal oxygen and re-oxygenate. Insufflation success improved with repeated percutaneous attempts (up to three), but prolonged hypoxia time increasingly necessitated euthanasia (insufflation 57%; re-oxygenation 48%). First, second and third percutaneous attempts achieved insufflation at median (IQR (range)) 74 (64-91 (46-110)) s, 111 (95-136 (79-150)) s and 141 (127-159 (122-179)) s, respectively. Eighteen teams failed with percutaneous cannulae and performed scalpel techniques, predominantly dissection cannulation (n = 17) which achieved insufflation in all cases (insufflation 100%; re-oxygenation 47%). Scalpel attempts were started at median (IQR (range)) 142 (133-218 (97-293)) s and achieved insufflation at 232 (205-303 (152-344)) s.While percutaneous cannula cricothyroidotomy could rapidly re-oxygenate, the success rate was low and teams repeated attempts beyond the recommended 60 s time frame, delaying transition to the more successful dissection cannula technique. We recommend this 'cannula-first' can't intubate, can't oxygenate algorithm adopts a 'single best effort' strategy for percutaneous cannula, with failure prompting a scalpel technique.

Ventilation through small-bore airways in children by implementing active expiration

Management of narrowed airways can be challenging, especially in the smallest patients. This educational review focusses on active expiration through small-bore airways with the Ventrain (Ventinova Medical, Eindhoven, The Netherlands). Manual ventilation with the Ventrain establishes inspiratory and expiratory flow control: By setting an appropriate flow, the volume of gas insufflated over time can be controlled and expiration through a small-bore airway is expedited by jet-flow generated suction, coined "expiratory ventilation assistance" (EVA). This overcomes the inherent risks of emergency jet ventilation especially in pediatric airway emergencies. Active expiration by EVA has been clinically introduced to turn a "straw in the airway" into a lifesaver allowing not only for quick and reliable reoxygenation but also adequate ventilation. As well as managing airway emergencies, ventilating through small-bore airways by applying EVA implements new options for pediatric airway management in elective interventional procedures. Safe application of EVA demands a thorough understanding of the required equipment, the principle and function of the Ventrain, technical prerequisites, clinical safety measures, and, most importantly, appropriate training.

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.

Automated expiratory ventilation assistance through a small endotracheal tube can improve venous return and cardiac output

BACKGROUND

Positive pressure ventilation can decrease venous return and cardiac output. It is not known if expiratory ventilation assistance (EVA) through a small endotracheal tube can improve venous return and cardiac output.

RESULTS

In a porcine model, switching from conventional positive pressure ventilation to (EVA) with - 8 cmH₂0 expiratory pressure increased the venous return and cardiac output. The stroke volume increased by 27% when the subjects were switched from conventional ventilation to EVA [53.8 ± 7.7 (SD) vs. 68.1 ± 7.7 ml, p = 0.003]. After hemorrhage, subjects treated with EVA had higher median cardiac output, higher mean systemic arterial pressure, and lower central venous pressure at 40 and 60 min when compared with subjects treated with conventional ventilation with PEEP 0 cmH₂0. The median cardiac output was 41% higher in the EVA group than the control group at 60 min [2.70 vs. 1.59 L/min, p = 0.029].

CONCLUSION

EVA through a small endotracheal tube increased venous return, cardiac output, and mean arterial pressure compared with conventional positive pressure ventilation. The effects were most significant during hypovolemia from hemorrhage. EVA provided less effective ventilation than conventional positive pressure ventilation.

Transtracheal Use of the CriCath Cannula in Combination With the Ventrain Device for Prevention of Hypoxic Arrest due to Severe Upper Airway Obstruction: A Case Report

A patient recently treated with surgery and radiation for oropharyngeal cancer presented with impending hypoxic respiratory and cardiac arrest in a difficult airway scenario. A CriCath cannula in combination with the Ventrain device and its active expiratory ventilation technology enabled oxygenation and ventilation for 60 minutes until a surgical airway was established. This case report is the first to describe the intended use of Ventrain technology in an emergent "can't ventilate-can't intubate" scenario.

Improved lung recruitment and oxygenation during mandatory ventilation with a new expiratory ventilation assistance device: A controlled interventional trial in healthy pigs

BACKGROUND

In contrast to conventional mandatory ventilation, a new ventilation mode, expiratory ventilation assistance (EVA), linearises the expiratory tracheal pressure decline.

OBJECTIVE

We hypothesised that due to a recruiting effect, linearised expiration oxygenates better than volume controlled ventilation (VCV). We compared the EVA with VCV mode with regard to gas exchange, ventilation volumes and pressures and lung aeration in a model of peri-operative mandatory ventilation in healthy pigs.

DESIGN

Controlled interventional trial.

SETTING

Animal operating facility at a university medical centre.

ANIMALS

A total of 16 German Landrace hybrid pigs.

INTERVENTION

The lungs of anaesthetised pigs were ventilated with the EVA mode (n=9) or VCV (control, n=7) for 5 h with positive end-expiratory pressure of 5 cmH2O and tidal volume of 8 ml kg. The respiratory rate was adjusted for a target end-tidal CO2 of 4.7 to 6 kPa.

MAIN OUTCOME MEASURES

Tracheal pressure, minute volume and arterial blood gases were recorded repeatedly. Computed thoracic tomography was performed to quantify the percentages of normally and poorly aerated lung tissue.

RESULTS

Two animals in the EVA group were excluded due to unstable ventilation (n=1) or unstable FiO2 delivery (n=1). Mean tracheal pressure and PaO2 were higher in the EVA group compared with control (mean tracheal pressure: 11.6 ± 0.4 versus 9.0 ± 0.3 cmH2O, P < 0.001 and PaO2: 19.2 ± 0.7 versus 17.5 ± 0.4 kPa, P = 0.002) with comparable peak inspiratory tracheal pressure (18.3 ± 0.9 versus 18.0 ± 1.2 cmH2O, P > 0.99). Minute volume was lower in the EVA group compared with control (5.5 ± 0.2 versus 7.0 ± 1.0 l min, P = 0.02) with normoventilation in both groups (PaCO2 5.4 ± 0.3 versus 5.5 ± 0.3 kPa, P > 0.99). In the EVA group, the percentage of normally aerated lung tissue was higher (81.0 ± 3.6 versus 75.8 ± 3.0%, P = 0.017) and of poorly aerated lung tissue lower (9.5 ± 3.3 versus 15.7 ± 3.5%, P = 0.002) compared with control.

CONCLUSION

EVA ventilation improves lung aeration via elevated mean tracheal pressure and consequently improves arterial oxygenation at unaltered positive end-expiratory pressure (PEEP) and peak inspiratory pressure (PIP). These findings suggest the EVA mode is a new approach for protective lung ventilation.

A prototype small-bore ventilation catheter with a cuff: cuff inflation optimizes ventilation with the Ventrain

Background

Ventilation through small‐diameter tubes typically precludes use of a cuff as this will impede the necessary passive outflow of gas alongside the tube's outer surface. Ventrain assists expiration and enables oxygenation and normoventilation through small‐bore cannulas or catheters, particularly in obstructed airways. A small‐bore ventilation catheter (SBVC; 40 cm long, 2.2 mm inner diameter) with a separate pressure monitoring lumen and a cuff was developed. Efficacy of oxygenation and ventilation with Ventrain through this catheter was investigated in sealed and open airways in a porcine cross‐over study.

Methods

Six pigs were ventilated with Ventrain (15 l/min oxygen, frequency 30 breaths per min, I : E‐ratio 1 : 1) through the SBVC, both with the cuff inflated and deflated. Prior to each test they were ventilated conventionally until steady state was achieved.

Results

With an inflated cuff, PaO₂ rose instantly and remained elevated (median [range] PaO₂ 61 [52–69] kPa after 30 min; P = 0.027 compared to baseline). PaCO₂ remained stable at 4.9 [4.2–6.2] kPa. After cuff deflation, PaO₂ was significantly lower (9 [5–28] kPa at 10 min, P = 0.028) and interventional ventilation had to be stopped prematurely in five pigs as PaCO₂ exceeded 10.6 kPa. Pulmonary artery pressures increased markedly in these pigs. Intratracheal pressures were kept between 5 and 20 cmH₂O with the cuff inflated, but never exceeded 2 cmH₂O after cuff deflation.

Conclusion

The SBVC combines the benefits of a small diameter airway and a cuff. Cuff inflation optimizes oxygenation and ventilation with Ventrain.

Emergency ventilation with the Ventrain® through an airway exchange catheter in a porcine model of complete upper airway obstruction

Purpose

During difficult airway management, oxygen insufflation through airway-exchange and intubating catheters (AEC/IC) can lead to life-threatening hyperinflation. Ventrain^® was originally designed to facilitate emergency ventilation using active expiration through short, small-bore cannulas. Herein, we studied its efficacy (oxygenation and ventilation) and safety (avoidance of hyperinflation) in a long, small-bore AEC.

Methods

In six anesthetized pigs, the upper airway was obstructed, except for a 100 cm long, 3 mm internal diameter AEC. After apneic desaturation to a peripheral oxygen saturation (SpO₂) of < 70%, ventilation through the AEC was started with Ventrain at an oxygen flow of 15 L·min⁻¹, a frequency of 30 breaths·min⁻¹, and an inspiration/expiration ratio of approximately 1:1. It was continued for ten minutes.

Results

Within one minute, severe hypoxia was reversed from a median [interquartile range] arterial saturation (SaO₂) of 48 [34-56] % before initiation of Ventrain ventilation to 100 [99-100] % afterward (median difference 54%; 95% confidence interval [CI] 44 to 67; P = 0.028). In addition, hypercarbia was reversed from PaCO₂ of 59 [53-61] mmHg to 40 [38-42] mmHg (median difference of −18 mmHg; 95% CI −21 to −15; P = 0.028). After ten minutes of Ventrain use, peak inspiratory and end-expiratory pressures were lower than during baseline pressure-controlled ventilation (8 [7-9] mmHg vs 12 [10-14] mmHg and −2 [−3 to +1] mmHg vs 4 [2 to 4] mmHg, respectively; P = 0.027 for both). No hemodynamic deterioration occurred.

Conclusion

Ventrain provides rapid reoxygenation and effective ventilation through a small-bore AEC in pigs with an obstructed airway. In clinical emergency situations of obstructed airways, this device may be able to overcome problems of unintentional hyperinflation and high intrapulmonary pressures when ventilating through long, small-bore catheters and could therefore minimize the risks of barotrauma and hemodynamic instability.