Describe  the  anatomy   of the  tracheobronchial tree, as  seen  down  a  bronchoscope inserted via an endotracheal tube.

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College Answer

As the bronchoscope exits the endotracheal tube, the tracheal rings are seen anteriorly. They are deficient posteriorly, where the trachealis muscle runs longitudinally. As the bronchoscope is advanced a narrow antero-posterior ridge (the carina) is seen, where the trachea divides into the right and left main bronchi. The right main bronchus is relatively in line with the trachea, while the left comes off at a greater angle. Advancing down the right main bronchus; the right upper lobe bronchus comes off laterally (3 o’clock) approximately 2 cm past the carina, and divides into the branches to the apical, anterior and posterior segments; the middle lobe bronchus is seen anteriorly (12 o’clock) and divides into the branches to the medial and lateral segments; soon after the apical segment of the lower lobe is seen posteriorly (6 o’clock); then the four basal segments are seen (medial, lateral, anterior and posterior). Pulling back to the trachea, then advancing down the left main bronchus; at approximately 5 cm the left main bronchus divides into the left upper lobe bronchus which is seen laterally (9 o’clock) and the left lower lobe bronchus. The upper lobe bronchus divides into the superior division and the lingular division. The superior division gives rise to two branches, the apicoposterior and anterior segments. The lingula gives rise to the superior and inferior segments. The lower lobe bronchus gives rise to the apical segment of the lower lobe seen posteriorly (6 o’clock), then the three basal segments (lateral, anterior, and posterior).


Fourteen out of forty-one candidates passed this question.

Discussion

A picture is worth a thousand words. However, there is no concise graphical summary of this, and one can really go berzerk with bronchial nomenclature.

The low pass rate for this question demonstrates the lack of access to quality bronchoscopy teaching in our specialty.

Additonally, the college answer seems to fail to acknowledge the need to change the orientation of the bronchoscope when advancing it. Thus, instead of coming off at 3o'clock, the right main bronchus is actually seen at 12 o'clock (because you have turned the bronchoscope in order to guide the flexible tip into the right main bronchus).

In short, these are the landmarks one encounters when performing a bronchoscopy.

  • Right main bronchus
    • right upper lobe bronchus at 12 o'clock
      • branches to the apical, anterior and posterior segments
    • right bronchus intermedius
      • right middle lobe bronchus
        • 3 branches: to the right middle medial and lateral segments
      • right lower lobe bronchus
        • apical segment of the lower lobe
        • four basal segments: medial, lateral, anterior and posterior
  • Left main bronchus
    • left upper lobe bronchus
      • superior division
        • apicoposterior and anterior segments
      • lingular division
        • superior and anterior segments
    • left lower lobe bronchus
      • apical segment of the lower lobe
      • three basal segments: lateral, anterior, and posterior.

References

LITFL have some excellent bronchoscopy videos.

Educational resources for bronchoscopy are available from the wonderful website of the American Thoracic Society.

Additionally, ThoracicAnaesthesia.com has a full-on virtual bronchoscopy simulator which is essentially a Flash-based game, and which is disturbingly fun to play with.

Lastly, bronchoscopy.org is probably the definitive resource for all this, and represents the pinnacle of bronchoscopic excellence. Their bronchoscopic anatomy poster is the best thing ever.