Safety of transtracheal jet ventilation in upper airway obstruction

* E-mail: andrew.mcleod{at}porthosp.nhs.uk

Editor—We read with interest the article by Chandradeva and colleagues,1 who reported the use of percutaneous transtracheal jet ventilation (PTJV) in the emergency management of two patients with severe upper airway obstruction. We agree that this is an extremely useful technique for this situation but would like to suggest that the method they employed could be further enhanced by the use of an automated jet ventilator with end-expiratory pressure monitoring linked to a pause function. We have used this technique in two situations similar to those described in their article.

Case 1, a 64-yr-old man undergoing tracheostomy because of worsening episodes of stridor secondary to a vocal cord palsy after radiotherapy for malignant neck lymphadenopathy. He was given a small dose of midazolam and then an inhalational induction was attempted using sevoflurane in oxygen 100%. During induction the patient developed worsening stridor, and became restless. His arterial oxygen saturation began to fall, at which point the anaesthetist abandoned the gas induction and called for help. Stridor and hypoxia persisted despite discontinuing the volatile agent. At this point a second anaesthetist inserted a 14G Ravussin jet ventilation catheter (VBM, Germany) through the cricothyroid membrane under local anaesthesia, and the patient's lungs were oxygenated with PTJV. We used an automatic jet ventilator (Mistral model, Acutronic, Switzerland), and delivered oxygen () with initial settings of: driving pressure=1 bar (15 psi), frequency=30 min–1, and pause pressure=20 cm H2O. This led to a rapid improvement of his oxygen saturation and a decision was made to continue with inhalational induction. This proceeded with difficulty, but on the occasions when upper airway patency was reduced, the ventilator detected a rise in the end-expiratory pressure and paused to limit lung over-inflation. I.V. anaesthesia was administered to complete the induction, and the patient was intubated orally once asleep and after neuromuscular blocking agents had been given. Like Chandradeva and colleagues,1 we found that PTJV maintained good oxygenation, and that the gas emerging through the glottis also assisted with successful tracheal intubation.

Case 2, an 88-yr-old man presented with stridor secondary to bilateral vocal cord palsy for tracheostomy and examination under anaesthesia. Because of diminished cervical spine mobility, a good view at direct laryngoscopy could not be predicted confidently. A 14G jet ventilation catheter (as above) was inserted through the cricothyroid membrane under local anaesthesia. Tracheal placement was confirmed from the presence of a regular capnograph waveform, and jet ventilation started with the patient awake. The ventilator was initially set at: driving pressure=1.5 bar (22.5 psi), frequency=30 min–1, and pause pressure=25 cm H2O. Anaesthesia was induced i.v., and bag mask ventilation confirmed after which the patient was intubated conventionally with an 8.0 mm cuffed oral endotracheal tube. The jet ventilation catheter was removed, and the tracheostomy completed uneventfully. In common with the first case, effective oxygenation was achieved with jet inflation pressures limited to 1.5 bar, and end-expiratory pressures limited to levels conventionally believed to be safe.

As Chandradeva and colleagues acknowledge, the incidence of barotrauma during PTJV remains a concern, but the actual risk of this complication has not been estimated precisely. PTJV using a jet ventilator that incorporates end-expiratory pressure monitoring is now well described for elective surgery to the larynx.2 Although peak inflation pressures remain unknown, the measured end-expiratory pressure has been shown in a separate study to correlate well with pulmonary distension.3 In their clinical study employing pressure limited PTJV in elective patients, Bourgain and colleagues reported an incidence of 1% for pneumothorax.2 In emergency scenarios, where there is severe compromise to the upper airway, intrathoracic pressures and volumes during unrestrained PTJV would be unknown, and the risk of barotrauma is likely to be higher. Although these are, to an extent, speculations we believe that on a priori grounds, using a dedicated jet ventilator with a pause pressure alarm facility can limit these risks as far as possible, and in the future may come to represent best practice.

A. D. M. McLeod*, M. W. H. Turner and K. J. Torlot

Portsmouth, UK


 
* E-mail: chandra.chandradeva{at}qms.nhs.uk

Editor—Thank you for the opportunity to respond to the letter from McLeod and colleagues concerning our paper.1 They suggest that the delivery of jet ventilation with an automated jet ventilator with end-expiratory pressure monitoring linked to a pause function could enhance the safety of PTJV by minimizing the risk of barotrauma in severe upper airway obstruction. We agree with their statement and would like to thank them for making a contribution to the safety of PTJV in airway obstruction.

There is another potential benefit of employing automated jet ventilation. Studies in experimental models that simulate normal airway diameter and lung compliance using a driving pressure of 3.5 bar (50 psi) have demonstrated that the gas flow through 20, 16, and 14G cannula is ~400,4 500,5 and 1600 ml s–1,4 respectively. As the 1-s tidal volume with a 14G cannula is equal to 1600 ml, the inspiratory time should be limited to less than 1 s (e.g. 0.5 s) and the inspiratory:expiratory (I:E) ratio should be ~1:3 to allow adequate time for deflation or exhalation and thereby avoid air trapping and barotrauma. In order to meet these ventilatory requirements, it could be argued that automated ventilation is safer than the manual delivery, especially in anxious resuscitation situations.

In the cases reported by McLeod and colleagues, the airway obstruction appeared to be caused by vocal cord palsy but in our cases the acute airway obstruction was attributable to severe supraglottic oedema. We feel that it is important to take this difference into account as the driving pressure that is required to open up airway obstruction attributable to supraglottic oedema could be higher. However, the optimum driving pressure or more importantly the optimum intratracheal pressure that is required is not known. McLeod used a driving pressure of up to 1.5 bar (22.5 psi) via 14G transtracheal cannula whereas we employed 3 bar (44 psi) via a 14G cannula in severe supraglottic oedema. Patel6 reported a driving pressure of 3.5 bar (50 psi), which was delivered manually via varying sizes of cannulae (12G, 16G, and 6 F) in 23 patients when there was a cannot intubate and difficult to ventilate' situation and did not encounter barotraumas in the case series. Although barotrauma is a potential complication and a serious concern among the users of PTJV, the reported incidence of this complication, if driving pressure is less than 4 bar,4 remains low.2 6 When in doubt, it seems prudent to start with the driving pressure at a low level, increasing it as dictated by the clinical response.

We wish to emphasize that the application of PTJV should be considered as a rescue and temporary manoeuvre to oxygenate the patient while a more secure permanent airway is being established at the earliest opportunity. It is our experience that tracheal intubation is aided by virtue of inducing high intratracheal pressure and its effect on the glottic area. If direct laryngoscopic tracheal intubation during the PTJV fails, a definitive airway should be established by means of surgical or percutaneous dilatational tracheostomy or fibreoptic-aided intubation without delay. Whether automated or manually delivered PTJV is used, great care should be exercised at all times to minimize the risk of barotrauma and the duration of the PTJV should be kept to a minimum.

K. Chandradeva* and C. Palin

Sidcup, UK

References

1 Chandradeva K, Palin C, Ghosh SM, Pinches SC. Percutaneous transtracheal jet ventilation as a guide to tracheal intubation in severe upper airway obstruction from supraglottic oedema. Br J Anaesth 2005; 94: 683–6[Abstract/Free Full Text]

2 Bourgain JL, Desruennes E, Fischler M, Ravussin P. Transtracheal high frequency jet ventilation for endoscopic airway surgery: a multicentre study. Br J Anaesth 2001; 87: 870–5[Abstract/Free Full Text]

3 Bourgain JL, Desruennes E, Cosset MF, Mamelle G, Belaiche S, Truffa-Bachi J. Measurement of end-expiratory pressure during transtracheal high frequency jet ventilation for laryngoscopy. Br J Anaesth 1990; 65: 737–43[Abstract]

4 Gaughan SD, Ozaki GT, Benumof JL. Comparison in a lung model of low—and high-flow regulators for transtracheal jet ventilation. Anesthesiology 1992; 77: 189[ISI][Medline]

5 Spoerel WE, Narayanan PS, Singh NP. Transtracheal ventilation. Br J Anaesth 1971; 43: 932–9[ISI][Medline]

6 Patel RG. Percutaneous transtracheal jet ventilation. A safe, quick, and temporary way to provide oxygenation and ventilation when conventional methods are unsuccessful. Chest 1999; 116: 1689–94[Abstract/Free Full Text]





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