BJA Advance Access originally published online on October 31, 2007
British Journal of Anaesthesia 2007 99(6):891-897; doi:10.1093/bja/aem312
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Air entrainment during high-frequency jet ventilation in a model of upper tracheal stenosis
1 Department of Anaesthesia, Critical Care and Pain Management, University Hospitals of Leicester NHS Trust, Leicester Royal Infirmary, Leicester LE1 5WW, UK
2 Department of Cardiovascular Sciences,Clinical Division of Anaesthesia, Critical Care and Pain Management, University of Leicester,Leicester Royal Infirmary, Leicester LE1 5WW, UK
* Corresponding author. E-mail: piotrbuczkowski{at}hotmail.com
Background: Previous work has demonstrated that when high-frequency jet ventilation (HFJV) is applied above an airway stenosis, higher distal airway pressures are produced compared with when the same ventilation is delivered below the stenosis (BSV). This study aimed to investigate the mechanisms underlying this finding.
Methods: HFJV was applied to a model of laryngo-tracheal stenosis with the jet located above the stenosis (ASV), with a catheter passed through the stenosis (TSV) or with HFJV delivered by a side port BSV. For each configuration and over a range of diameters of stenosis (2.5–8.5 mm), distal tracheal pressures and delivered minute volume were measured and air entrainment estimated. Experiments were repeated using the same model with the addition of a simulated pharynx around the stenosis.
Results: Distal airway pressures, minute volumes, and air entrainment were consistently higher during ASV compared with BSV and TSV. The presence of the pharynx made no significant difference to airway pressures or air entrainment. Delivered minute volumes varied between ASV, TSV, and BSV, and were also dependent on the stenosis diameter. With ASV, there appeared to be a range of stenosis diameters (4.0–5.5 mm) which maximized minute volumes.
Conclusions: The results suggest that the high airway pressures generated during ASV are the consequence of air entrainment and this effect, although reduced slightly, is maintained in the presence of the model pharynx. In contrast to the previous work, no significant entrainment occurred during BSV. If applicable to patients, these data suggest that ASV HFJV should be avoided in small diameter stenoses, but provides more efficient gas delivery and greater distending pressures with larger stenoses. BSV HFJV produces lower distal pressures and more consistent oxygen concentrations of injected gas across a range of stenosis diameters.
Keywords: airway, calibre; airway, obstruction; model, jet ventilation; ventilation, high frequency jet; ventilation, respiratory impedance
3 Present address: Department of Anaesthesia, Derby Hospitals NHS Foundation Trust,Derbyshire Royal Infirmary, London Road, Derby DE1 2QY, UK
These data were presented in part to the American Association of Anesthesiologists Meeting, Las Vegas, October 2004 and 3rd Biannual Meeting of the European Society for Jet Ventilation, Vienna, November 2004.
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G. Mausser, G. Schwarz, P. W. Buczkowski, and J. P. Thompson Air entrainment during high-frequency jet ventilation Br. J. Anaesth., March 1, 2008; 100(3): 418 - 419. [Full Text] [PDF] |
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- High frequency jet ventilation above, passed through and below the airway stenosis.
- Gerlinde Mausser
- British Journal of Anaesthesia, 3 Dec 2007 [Full text]
- Reply to Drs Mausser and Schwarz
- Piotr W. Buczkowski, et al.
- British Journal of Anaesthesia, 12 Dec 2007 [Full text]
