Manual Translaryngeal Jet Ventilation

Sustained oxygenation without ventilation in paralyzed pigs with high-flow tracheal oxygen

OBJECTIVES

It is generally assumed that ventilation is necessary for oxygenation. This study tested if paralyzed animals without respirations can maintain arterial oxygenation when administered high-flow oxygen delivered by a catheter in the trachea.

METHODS

DESIGN

Prospective observational study.

SETTING

University research laboratory.

PARTICIPANTS

3 anesthetized/paralyzed swine weighing 29.5 +/- 4.2 kg. INTERVENTIONS/OBSERVATIONS: Pigs were intubated, anesthetized with intravenous tiletamine and a pentobarbital drip. A femoral arterial line was placed to record arterial blood gases and vital signs every 5 minutes. Respiratory paralysis was obtained with vecuronium 150 microg/kg and repeated at any sign of movement. A catheter was placed in the trachea to deliver oxygen at 15 L/min. Outflow gas from the endotracheal tube was analyzed for O2 and CO2. O2 was discontinued at 75 minutes. The institutional animal care and use committee approved the protocol.

RESULTS

All pigs survived to 75 minutes. PaO2 was more than 100 mm Hg throughout the study period. Mean PaCO2 was 37.4 +/- 2.8 mm Hg at baseline, 146 +/- 59 at 30 minutes, then rose above 200 mm Hg in all pigs by 45 minutes. Mean arterial pH fell from 7.47 +/- 0.04 at onset to 6.75 +/- 0.06 at 75 minutes. When oxygen was terminated at 75 minutes, PaO2 fell to 16.5 +/- 7.6 mm Hg within 5 minutes, and all pigs were sacrificed within 10 minutes. For outflow gas, O2 was more than 98% and expired CO2 less than 1% throughout the study period.

CONCLUSIONS

Paralyzed, unventilated pigs receiving high-flow oxygen via a tracheal catheter remained alive after 75 minutes, although a profound respiratory acidosis developed.

Dimensions of the neonatal cricothyroid membrane - how feasible is a surgical cricothyroidotomy?

BACKGROUND

Airway management of the neonate remains a cornerstone in neonatal resuscitation which in most cases involves tracheal intubation. However, difficult intubations do occur. Cricothyroidotomy is recognized as an entry point below the vocal cords. This procedure becomes increasingly difficult in young children and is not recommended in children under the age of 5 years. Little is known about the anatomy of the neonatal airway, especially the size of the cricothyroid membrane. The aim of the study was to determine the dimensions of the cricothyroid membrane in neonates.

METHODS

Twenty-seven neonatal cadavers (mean height of 44.89 cm and a mean weight of 2.05 kg) were carefully dissected and the dimensions of the cricothyroid membrane recorded with a digital caliper (accuracy 0.01 mm) by two independent observers.

RESULTS

The cricothyroid membrane has a mean height of 2.61 mm (sd: 0.71) and width of 3.03 mm (sd: 0.63).

CONCLUSIONS

Results of this study indicate that the dimensions of the cricothyroid membrane are too small for passing a tracheal tube as the dimensions of the tube exceeds that of the cricothyroid membrane. This could fracture the cartilages of the larynx. The performance of a surgical cricothyroidotomy with passing of a tracheal tube is therefore strongly discouraged in neonatal patients.

Difficult Airway Society guidelines for management of the unanticipated difficult intubation

Problems with tracheal intubation are infrequent but are the most common cause of anaesthetic death or brain damage. The clinical situation is not always managed well. The Difficult Airway Society (DAS) has developed guidelines for management of the unanticipated difficult tracheal intubation in the non-obstetric adult patient without upper airway obstruction. These guidelines have been developed by consensus and are based on evidence and experience. We have produced flow-charts for three scenarios: routine induction; rapid sequence induction; and failed intubation, increasing hypoxaemia and difficult ventilation in the paralysed, anaesthetised patient. The flow-charts are simple, clear and definitive. They can be fully implemented only when the necessary equipment and training are available. The guidelines received overwhelming support from the membership of the DAS.

DISCLAIMER

It is not intended that these guidelines should constitute a minimum standard of practice, nor are they to be regarded as a substitute for good clinical judgement.

Cricothyroidotomy: A clinical anatomy review

The safe and successful performance of a cricothyroidotomy demands a working and yet specific knowledge of anatomy. An ignorance or misunderstanding of anatomy may result in failure or complications. The Educational Affairs Committee of the American Association of Clinical Anatomists has highlighted the importance of clinical anatomy for several invasive procedures. This review is building on their work and contribute further to the understanding of the anatomical framework, particularly the pitfalls and complications related to performing a cricothyroidotomy.

Transtracheal oxygenation : an alternative to endotracheal intubation during cardiac arrest

STUDY OBJECTIVES

Because efforts to secure adequate arterial oxygenation during cardiac resuscitation are more important than efforts to promote CO(2) elimination, we investigated whether continuous transtracheal oxygenation (TTO) could represent a potentially simpler alternative to conventional positive-pressure ventilation with 100% O(2) through an endotracheal tube.

DESIGN

Controlled and randomized.

SETTING

Animal laboratory.

PARTICIPANTS

Thirty male Sprague-Dawley rats.

INTERVENTIONS

The technique for TTO was initially developed and tested in five rats. A model of ventricular fibrillation (VF) was then used to compare the effects of TTO (n = 5) with the effects of O(2) delivery through an endotracheal tube as part of positive-pressure ventilation (n = 5) or through a mask without additional airway intervention (n = 5). VF was induced and left untreated for 4 min, after which chest compression and one of the three oxygenation interventions was started. Defibrillation was attempted after 6 min of chest compression. In a subsequent series, defibrillation was attempted after 10 min of chest compression in rats treated with either TTO (n = 5) or endotracheal intubation (ET; n = 5).

MEASUREMENT AND RESULTS

TTO and ET secured adequate arterial PO(2) during chest compression (213 +/- 77 mm Hg and 154 +/- 36 mm Hg; not significant), whereas the mask yielded an arterial PO(2) of only 49 +/- 38 mm Hg (p < 0.05). Each rat treated with TTO or ET was successfully resuscitated and survived the postresuscitation interval, but none of the rats treated with the mask survived. TTO maintained its efficacy after increased duration of chest compression.

CONCLUSION

TTO was as effective as conventional positive-pressure ventilation with 100% O(2) for securing oxygenation, resuscitation, and short-term survival and more effective than O(2) delivered through a mask.

A stab in the dark! Are you ready to perform needle cricothyroidotomy?

The objective of this study was to assess the availability of pre-prepared equipment for needle cricothyroidotomy, and the knowledge of staff in its use in Accident and Emergency (A&E) departments in Great Britain. A telephone survey was undertaken of all A&E departments seeing more than 30,000 new patients per year. 184 hospitals were contacted. 98% of the doctors agreed to be interviewed. 47% of the departments had made provision for immediate use of needle cricothyroidotomy. 45% of the doctors interviewed were fully conversant in the use of needle cricothyroidotomy. Provision of equipment for immediate use of needle cricothyroidotomy in A&E departments is generally inadequate. All departments should ensure that such equipment is immediately accessible, and that the staff is regularly trained in its use.

Manual translaryngeal jet ventilation and the risk of aspiration in a canine model

STUDY OBJECTIVES

Manual translaryngeal jet ventilation (TLJV) is a safe and effective method of maintaining normal ventilation in apneic subjects. Little data exist on the amount of airway protection afforded with this technique of airway management. We sought to evaluate the risk of aspiration during manual TLJV.

SETTING

Data were collected in a laboratory animal model.

DESIGN

A prospective, nonrandomized, controlled trial was performed.

PARTICIPANTS

Seventeen adult apneic mongrel dogs were enrolled.

INTERVENTIONS

Intratracheal Gastrograffin was instilled and radiographic changes assessed during ventilation using a 0 to 3 scale (none to severe). Thirty-six trials were performed, with equal numbers at both 30 degrees and 45 degrees head elevation. The three groups studied were animals without airway protection (control), animals with a cuffed endotracheal tube (tube), and animals with a percutaneous TLJV cannula and a 50-psi oxygen source ventilated at a rate of 20 breaths per minute (jet).

MEASUREMENTS AND MAIN RESULTS

Significantly less radiographic evidence of aspiration was noted in the jet and tube groups at 30 degrees and 45 degrees compared with control animals (P = .002 each). At 45 degrees head elevation a trend toward increased aspiration scores in the jet group compared with the tube group (P = .065) was observed.

CONCLUSION

In our model, manual TLJV at 20 breaths per minute and an I:E ratio of 1:2 provided protection from aspiration comparable to that observed with a cuffed endotracheal tube at 30 degrees head elevation. At 45 degrees elevation, this protection was diminished.