Australasian Anaesthesia 2011 - Australian and New Zealand ...

86 Australasian Anaesthesia 2011Jet Ventilation and Anaesthesia 87Other indications for the use of HFJVHFJV has several applications in areas other than in laryngeal surgery. A subglottic technique is usually employedfor this purpose.Minimum movement with ventilation:The movements of thoracic and abdominal viscera during HFJV are much smaller than those seen during tidalventilation. This produces a relatively immobile target that is ideal for precision therapeutic interventions.Extracorporeal Shock Wave Lithotripsy (ESWL) uses focused, high intensity, acoustic pulses to break up stonesinside the kidney with minimal collateral damage. Most current lithotriptors have smaller focal zones with theadvantage of minimizing damage to surrounding soft tissues. Unfortunately, movement of the diaphragm duringspontaneous or intermittent positive pressure ventilation causes movement of the kidney and therefore the stonein and out of the acoustic ‘energy cone’ with every respiratory cycle. The shockwaves applied while the stones areout of the target zone have no effect on fragmentation leading to higher failure rates, incomplete treatment, andthe need for retreatment. Energy from such ‘stray’ shock waves can also cause injury to surrounding kidney tissues.Subglottic HFJV has been used during ESWL with great success. 66-67 A simplified technique of HFJV through asupraglottic airway such as a laryngeal mask airway is certainly simple and easy for this outpatient procedure. 68For similar reasons, HFJV has also been reported as a ventilation technique for stereotactic irradiation ofmetastasis in the lungs, cardiac radiofrequency ablation and percutaneous radiofrequency ablation of hepatictumours. 69-71Thoracic surgery:The low peak tracheal and transpulmonary pressures and low mean airway pressures (relaxed lungs) during HFJVmake it very useful for thoracic surgery. It has been used in conjunction with a wide range of thoracic procedures.(Table 2)Table 2. Some thoracic procedures in which HFJV has been reported as a useful ventilation techniqueAnaesthesia for open thoracic surgery 59,72-82One lung ventilationPartial lung ventilation during lung resectionStaple excision of subcentimeter lung nodulesBronchial repairTransthoracic oesophagectomyTAA with tracheal and right bronchial compressionOff pump single lung transplantRepair of coarctationAnterior approach scoliosis surgeryCarinal resection / TracheoplastyBronchial stentingRepair of congenital tracheal stenosisAnaesthesia for closed chest procedures 83-87Endobronchial laser treatment for tumoursTransthoracic endoscopic sympathectomyHFJV through the FOB for identifying segmental planesLung lavageInterventional fibreoptic bronchoscopyUninterrupted oxygenation during airway manoeuvres:The use of jet ventilation through an airway exchange device is an option that provides a way to deliver oxygeninto the lungs during procedures like a trial of extubation or the re-positioning of an endotracheal tube. 53,88 In thissetting, the narrow internal diameter and rather long length of some exchange catheters can result in volume lossdue to compression 89 and yet can also be dangerous when used in conjunction with an endotracheal tube withsmall internal diameter (restricted expiratory outlet) or when the tip of the catheter is inside a snugly fitting distalairway (risk of barotrauma). 88 The delivery of jet ventilation through the suction-biopsy channel of a flexible fibreopticbronchoscope has been shown to provide adequate ventilation. 90Common problems seen with HFJVHypercarbia is well documented and is more usually a problem with obese patients.Trans-tracheal cannulae have been found to be a major independent risk factor for complications in a 10 yearreview of different ventilation strategies in endoscopic laryngeal surgery. 91 Obstruction of trans-tracheal cannulaecan occur in up to 20% of cases 92 even with custom made, kink-resistant varieties. Care must be taken duringinsertion of the cannula to aim in a 45 degree angle caudad direction as soon as the trachea is entered. In somepatients with restricted space between the larynx and the jaw, a lower point of puncture at the cricotracheal junctionor even between the upper rings of the trachea may help to get the angle right.Difficulty with CO2 measurement is encountered at times with side stream CO2 monitoring as the sampling linetends to get blocked by respiratory secretions and blood. The use of preoperative anticholinergics, periodic suctioningand the use of a three way tap in the CO2 sampling line providing a route to unblock it are helpful.Serious complications associated with HFJV that have been reported are summarized in table 3.9, 45, 60- 65, 93-94Table 3. Summary of reported complications associated with HFJVExhalation difficultiesSurgical emphysema in the neck and chestPneumothoraxPneumomediastinumOccasional hypoxia (hypoventilation)Necrotising tracheo bronchitisHaemodynamic instabilityBenign gastric distensionCONCLUSIONJet ventilation during anaesthesia has been practiced for over forty years but is not widely practiced as a techniqueof choice mainly due to lack of exposure. Surveys on the practice show that most complications are associatedwith the use of manual jet ventilation at direct pipeline pressure without monitoring. HFJV delivered with automaticjet ventilators is safer but is only available in a few centres [97,98]. All reports concur that the essential factors forsuccessful HFJV are use of automatic jet ventilators, close monitoring and expert supervision.ACKNOWLEDGEMENTSThe author is thankful to Dr Simon Morphett, Staff Specialist, Department of Anaesthesia at the Royal HobartHospital, Hobart, Tasmania for editing the manuscript and J. Hanuszewicz from the Teaching and Research SupportUnit of University of Tasmania for help with the illustrations.