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Rigid bronchoscopy-induced bacterial translocation: is it a real threat?

Dept of Chest Diseases, Meram Medical Faculty, Selçuk University, Konya, Turkey

CORRESPONDENCE:

To the Editor:

I read with great interest the report by Nayci et al. 1, regarding rigid bronchoscopy-induced bacterial translocation in rats. However, several of their speculative comments are misleading and merit comment.

First, the animal model used in their study does not completely reproduce all the features of rigid bronchoscopy in humans. Bronchoscopy means examination of the tracheobronchial tree through a bronchoscope. In the current study, the inserted angiocath did not have similar physical properties of a rigid bronchoscope. Furthermore, this examination was performed outside the tracheobronchial tree through a lateral neck incision. For this reason, it would be better to entitle the article "intratracheal insertion of an angiocath induces bacterial translocation" rather than "rigid bronchoscopy induces bacterial translocation".

Secondly, the authors found a decrease in pH and arterial oxygen tension (P_a,O2), and an increase in arterial carbon dioxide tension values following insertion of the angiocath. They have concluded that bacterial translocation may be related to the hypoxaemia-induced mucosal damage of the intestines. However, Saarnivaara et al. 2 have found that instrumentation with a telescope during rigid bronchoscopy ameliorates rather than impairs the ventilation and oxygenation of the patients. During the course of the bronchoscopy, as well as after 1 h inthe recovery room, the arterial acid-base status was within normal limits,the mean P_a,O2 value during bronchoscopy ranged 23–32 kPa (175–240 mmHg) and was 18 kPa (138 mmHg) in the recovery room when the patients breathed 35% oxygen in the air. The authors suggested that the increased P_a,O2 value might be the result of increased oxygen concentration as well as of an increased inflation pressure at the distal end of the bronchoscope 2. Furthermore, it has been suggested that the term rigid bronchoscopy should be replaced with "open ventilating bronchoscopy", because the property of splinting open the airway and providing a side-arm for delivery of oxygen or anesthetic gases is an inherent feature of all present rigid bronchoscopes. In contrast, the flexible bronchofibrescope inevitably fills a portion of the airway and diminishes ventilation 3. These findings suggest that rigid bronchoscopy is a safe procedure regarding hypoxaemia.

Thirdly, what was the average internal tracheal diameter of the rats? This is an important point, since if the diameter of an angiocath is close to the tracheal diameter of a rat this may lead to a much tighter insertion and the latter situation may cause tracheal mucosal damage during the procedure. According to the authors, mucosal damage induced by the bronchoscope can promote bacteraemia and bacterial translocation. Nevertheless, in my opinion, the risk of mucosal damage is minimal for a human trachea during procedure performed by a well-trained and skilled bronchoscopist, because anteroposterior and transverse internal diameters ofthe adult human trachea are 16x14 mm, and the rigid, bronchoscopes commonly used have an external diameter that varies 2–9 mm 4, 5.

In summary, one should be cautious of making a conclusion about a direct link between rigid bronchoscopy and bacterial translocation, because the results obtained using this animal model may be significantly different than those obtained in clinical studies.

References

1. Nayci A, Atis S, Talas DU, Ersoz G. Rigid bronchoscopy induces bacterial translocation: an experimental study in rats. Eur Respir J 2003;21:749–752.[Abstract/Free Full Text]
2. Saarnivaara L, Tarkkanen J. The effect of instrumentation with a telescope during bronchoscopy on arterial oxygen tension and acid-base balance. Acta Anaesthesiol Scand 1983;27:242–244.[Web of Science][Medline] [Order article via Infotrieve]
3. Helmers RA, Sanderson DR. Rigid bronchoscopy: the forgotten art. Clin Chest Med 1995;16:393–399.[Web of Science][Medline] [Order article via Infotrieve]
4. Scothorne RJ. The respiratory systemIn: Romanes GJ, ed. Cunningham's textbook of anatomyNew York, Oxford University Press, 1995; pp. 491–529.
5. Prakash UBS, Diaz-Jimenez JP. The rigid bronchoscopeIn: Prakash UBS, ed. BronchoscopyPhiladelphia, Lippincott-Raven, 1997; pp. 53–69.

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Permissions Request Permissions Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Zamani, A. Search for Related Content PubMed PubMed Citation Articles by Zamani, A.