Chapter 102 Trachea and Bronchi Flashcards
Label the diagram
How many terminal bronchioles are dogs estimated to have?
17,000 - 36,000
What type of cartilage are tracheal rings composed of?
Tracheal rings composed of hyaline cartilage
What is the name of dorsal muscle connecting traceal rings (N.B. inserts to external surface of tracheal rings)
Trachealis muscle
Approximately how many tracheal rings are there (and upper range)
Approx 35 tracheal rings (up to 46 reported)
What si the name of the tissue between tracheal rings?
Annular ligament
How many cartilage rings is the left mainstem bronchus typically made up of? And the right?
Typically 3 rings in left mainstem bronchus, only 1 in right.
How are bronchioles distinguised from smaller bronchi?
Smaller bronchi contain overlapping cartilage plates (rather than rings); diasppearance of plates marks transition to bronchiole.
List the layers of the trachea:
- Mucosa
- Submucosa
- Fibrocartilaginous layer
- Adventitia (in cervical trachea), serosa (in thoracic trachea).
where along thelength of the trachea is the cartilage the thinnest and the luminal diameter smallest?
At thoracic inlet
What type of epithelium lines the trachea?
Ciliated, pseudostratified, columnar epithelium
Aside from goblet cells, there are other mucus secreting glands in the trachea.
- What are they named?
- How do they differ from goblet cells?
- What is the pproximate density of these cells in canine trachea?
- What are they named? Tubuloalveolar mucus glands
- How do they differ from goblet cells? Produce equivalent mucous of 40 goblet cells
- What is the pproximate density of these cells in canine trachea? 1 opening/mm
During progression down the bronchial tree, how does ‘cell population’ vary?
Tubuloalveolar glands disappear first, then goblet cells, then ciliated cells.
Where does the trachea receive its segmental blood supply from?
Cranial and caudal thyroid arteries. Branches travel towards midline where they extensively anastomose
Where do the mainstem bronchi/bronchioles receive blood supply from?
Broncho-oesophageal arteries.
What is the venous drainage of the trachea/bronchi?
Thyroid vein, jugular vein, broncho-oesophageal veins
List 4 lymph nodes that drain trachea/bronchi:
- Cranial mediastinal
- Medial retropharyngeal
- Deep cervical
- Tracheobronchial
Which nerves supply the trachea/bronchi?
Is there a dominant side (in dogs at least)?
Vagus/recurrent laryngeal
Right dominant side. (L stimulation –> only 28% response compared with R stimulation)
List 3 functions of trachea
- Conduit fo rair passage
- Warms and humidifies air
- Mucociliary clearance
What is the typical mucociliary clearance rate in dogs?
1 - 1.5 cm/min
List two physiological changes that occur with trachealis m contraction
- Increased airflow velocity
- Increased rigidity
- Creates mucosal inversion ‘furrow’ along which mucus collected and expelled
What is the normal ratio of tracheal:thoracic inlet diameter in:
Normal dogs:
Brachy dogs:
English Bulldogs:
Normal dogs: 0.2
Brachy dogs: 0.16
English Bulldogs: 0.13
List 3 radiographic findings of URT obstruction.
And 3 of lower RT obstruction
URT obstruction:
- Tracheal narrowing distal to obstruction
- Tall, domed diaphragm
- Under-aerated lungs
- (Poss pulmonary oedema)
Lower RT obstruction:
- Flattened diaphragm
- Over-inflated lungs
- –> prominent pulmonary vasculature
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What is the advantage of fluoro over rads for evaluatio of trachea?
What is the advantage of CT over rads?
List an advantage of tracheobronchoscopy:
- Fluoro allows dynamic assessment (increased intrathoracic pressure (e.g. during cough) can exacerbate collapse)
- CT results in less under-estimation of dimensions (CT validated as method for diagnosing tracheal hypoplasia, collapse, stenosis in non-anaesthetised dogs and cats = “virtual endoscopy”!)
- Tracheobronchoscopy allows grading of collapse and evaluation of bronchial tree (?presence of bronchomalacia), collection of BAL.
what proportion of BAL fluid must be retirieved for sample to be considered representative?
How can yield be maximised?
>33% of infusate to be considered representative
Use of surgical suction pump (max -37 mm Hg, pulsatile) vs manual aspiration
List 3 contraindications for temporary trach tube
- Collapse distal to tracheostomy
- Obstruction distal to tracheostomy
- Tracheal stent in place
What are the recommendation re transverse tracheostomy inscision?
And tracheostomy tube size?
Other tube considerations?
3rd, 4th, 5th ring, no more then 50% of circumference.
Outer tube diameter <75% of tracheal diameter
Cannulated vs non cannulated. If cuffed hig volume low pressure cuff!
List 5 aspects of post-op trach tube care
- Nebulise/instill 0.2ml/kg sterile saline q4h
- Replace/clean cannula of tube bid or suction airway (pre-and post oxygenate, attach to ECG as bradycardia (vagal response) can occur, atelectasis and hypoxia too, max 10-12 seconds at a time)
- Banage surrounding area
- Abx ointment around stoma and clean
- If cuffed, deflate q4h.
What are the to potential points of tracheal stenosis following temporary tracheostomy?
Incision or cuff/tube tip site.
What proportion of dogs with temoprary tracheostomy tubes are reported to survive to discharge?
And cats?
60% of dogs with temp. trach survived to discharge
43% of cats with temp. trach survived to discharge
List 5 potential short term complication sof temporary tracheostomy tube placement, and 2 longer term.
Short term complications:
- Tube blockage
- Inadvertent tube removal
- SC emphysema/pneumomediastinum/pneumothorax
- Coughing/gagging
- Infection
- Respiratory distress
Longer term complications
- Tracheal stenosis
- Tracheal necrosis
In dogs undergoing temporary tracheostoomy tube placement, what is the average percentage loss of luminal size ?
What degree of stenosis is necessary before clinical signs become evident?
On average, luminal size reduced by 18-25%
50 - 75% stenosis necessary before clinical signs are evident.
How does placement of temorary silicone tracheal stoma stent compare to ususal ttt placement (Trinterud)?
More invasive to place, no dogs suffered life-threatening complications
Briefly list steps of permanent tracheostomy
- Ventral midline approach, mattress sutures in sternohyoideus to appose them odrsal to trachea.
- Excision of window 9max 50% circumference) from 3-4 tracheal rings, leaving mucosa intact.
- Incise rotated “H” shape into mucosa to allow it flap dorsally and laterally.
- Suture mucosa to skin using 3/0 or 4/0 monofilament absorbable (approx 2mm apart)
From tobias pic;
A, Mattress sutures are used to appose the sternohyoideus muscles dorsal to the trachea. A segment of cartilage is removed, and the mucosa is incised (dashed line).
B, Interrupted sutures are used to attach the mucosa to the skin at the corners of the stoma. A simple continuous pattern is then used to meticulously attach the tracheal mucosa to the skin.
How is tracheal collapse graded (n.b. can only use this when assessed bronchoscopically)
Tangner and Hobson described a three-dimensional, endoscopic grading system still in use today. Grades I to IV represent 25%, 50%, 75%, and 100% collapse
How specifically should rads be obtained for tracheal stent planning?
How is stent size chosen (diameter and length)?
What radiographic landmarks are used to determine location of cricoid and carina?
Rads
- Calibrated oesophageal probe
- ET cuff at larynx and inflate to 20 cm H2O
- Get expiratory rads too
Stent size:
- Length: Ideally, from 1 cm caudal to cricoid to 1cm cranial to carina (consult manufacturer guide re expected foreshortening). At least spanning collapsed area
- Diameter: 10-20% larger than maximal rad diameter
Landmarks:
- Cricoid: Beneath C3-C4 disc space
- Carina: Level with 4th rib
