2. Anatomy of Trachea and Bronchi Flashcards
Trachea:
tube of cartilage with a membranous lining which is continuous inferiorly with the larynx.
The trachea proper is 10–11 cm long,
extending downwards from the cricoid cartilage at the level of the sixth cervical vertebra, as far as the sixth thoracic vertebra (in full inspiration).
diameter in the adult is around 20 mm.
year of life its diameter is 3 mm or less,
Trachea Structure:
Structure: it comprises 16–20 C-shaped cartilages attached vertically by fibroelastic
connective tissue, which helps explain the mobility of the structure.
displaced slightly rightwards by the arch of the aorta @ Bifurcation
Anterior relations
Posterior relations:
Lateral
the isthmus of the thyroid overlying the second to fourth tracheal
rings.
sternohyoid and sternothyroid muscles,
the oesophagus lies posteriorly, and the recurrent laryngeal
nerves run in grooves between the trachea and oesophagus
its lower course, it is related on the right to
the lung and pleura, to the brachiocephalic artery and veins,
On the left, it is related to the arch of the aorta and
the left common carotid and subclavian arteries
The right and left main bronchi
T5
R = shorter (3 cm long), wider and angled more vertically than the left
hat foreign bodies and tracheal tubes are more likely to enter its orifice
than the left
left main bronchus is more obliquely placed and is some 5 cm in length.
In children, the angles of the bronchi at the
carina are equal.
Bronchopulmonary segments – right lung:
within about 2.5 cm of the bifurcation,
the right main bronchus gives off the right upper lobe bronchus
It is this right upper lobe bronchus that is most at risk from inadvertent occlusion by a tracheal tube or a right-sided double-lumen endobronchial tube
The right main then gives off the
middle lobe bronchus, which is directed downwards and forwards
The medial, anterior, lateral and posterior basal segments arise in due course from
the main stem of the lower lobe bronchus, which continues in its downward
direction.
Bronchopulmonary segments – left lung
the longer left main bronchus gives off the
left upper lobe bronchus after about 5 cm,
this then divides into a superior division from which arise
apical, posterior and anterior segments of the upper lobe,
The anatomy of the left lower lobe is similar to the right in that the left lower lobe
bronchus gives off superior, anterior basal, lateral basal and posterior basal segments
Lobes
Right upper lobe
Apical
Lateral
Apical
Left upper lobe
Apical
Left lower lobe
Anterior
Lingula
Superior
Posterior
RML
Lateral
Medial
RLL
Apical
Medial basal
Anterior basal
Lateral basal
Posterior basal
LLL
Apical
Medial basal
Anterior basal
Lateral basal
Posterior basal
Pulmonary aspiration of gastric contents:
- If the patient is supine,
it is more likely that the apical segments of the lower lobes
will be affected because of the direct posterior projection
of the bronchus of the apical segment.
- lateral position,
then aspiration is more likely to affect the upper lobes. - Prone.
RML + Lingula - sitting,
it will be the posterior or lateral basal segments of the
lower lobes that are contaminated
Management of aspiration:
the cardinal sign will be otherwise unexplained desaturation.
In a patient who has not received neuromuscular blockers this may be preceded
by coughing which fails to settle as anaesthesia deepens
Auscultation may reveal rhonchi and/or crepitations.
Chest X-ray changes often occur early enough to support the diagnosis of significant
aspiration, although they can be delayed for 6 hours or more.
Management is essentially expectant.
Does not need supplemental oxygen to maintain a
normal SpO2 after 2 hours, then it is unlikely that there will be significant sequelae
patient remain oxygen-dependent, then he or she will need supportive therapy
which in severe cases may include intubation and ventilation. There is no evidence of
any benefit from the administration of prophylactic antibiotics or steroids
Fibreoptic bronchoscopy
You will see first the trachea; the anterior
wall, which is composed of complete cartilaginous bands; and the posterior wall,
which is membranous. The carina separates the right and left main stem bronchi
Rght main bronchus is wider than the left and is shorter at
~3 cm long. It is also angled more vertically than the left. Within ~2.5 cm of the
bifurcation can be seen the right upper lobe bronchus
middle lobe bronchus, which is directed downwards and forwards. Just
below the origin of the middle lobe bronchus and opposite to it is the bronchus of
the apical segment of the lower lobe; beyond this the main stem of the lower lobe
bronchus continues downwards.
Left side at bronch
Left side view: the left main bronchus is more obliquely placed and is about 5 cm
in length. It gives off the left upper lobe bronchus near its termination at about
5 cm, which then divides into a superior division and a lingular bronchus. The
anatomy of the left lower lobe bronchus is similar to the right.
Double-lumen endobronchial tubes
pulmonary resection, oesophagogastrectomy, surgery of the thoracic aorta, anterior
spinal fixation and thoracoscopic sympathectomy. A left-sided tube is almost always
favoured because this avoids the risk of inadvertently occluding the origin of the right
upper lobe bronchus.
double-lumen tube is positioned correctly when the upper surface of
the bronchial cuff lies immediately distal to the bifurcation of the carina. The
position of the tube should be checked endoscopically.
Tracheal damage:
this may be caused by external trauma but has also been reported
not infrequently as a complication of tracheal intubation. Clinical features may include
alteration of phonation and stridor (if the larynx is involved), hoarseness, subcutaneous
emphysema, pain on external palpation and pain on movement of the tongue.
