Bronchoscopy

Indications for bronchoscopy include chronic cough, hemoptysis, or unexplained pulmonary infiltrates (focal, diffuse, lobar, bronchial, alveolar, consolidated lobes). Bronchoscopy allows collection of distal airway and alveolar samples for culture and cytology and allows characterization of disease by visualization of the airways. A more accurate prognosis can be given in cases of chronic bronchitis or bronchiectasis when the disease process has been visually assessed through endoscopy. Bronchoscopy also allows evaluation of dynamic airway changes in tracheal collapse or bronchomalacia. Foreign body removal can be performed, and with bronchoscopy, causes for treatment failure or relapsing disease can often be detected.

Contraindications and Complications

There are no absolute contraindications for bronchoscopy, however, since this procedure requires full anesthesia, relative contraindications might include serious cardiac arrhythmias and worsening respiratory distress or hypoxemia. Bronchospasm post bronchoscopy can become a problem in the cat, however this can be alleviated by administration of terbutaline subcutaneously (0.01 mg/kg) at the time of the procedure. Worsened cough or increased airway obstruction can occur in dogs with severe tracheal collapse or bronchomalacia. Increased irritation of the airway potentiates a cough, and suppression of respiratory effort by anesthetic agents allows passive collapse of diseased airways. Instillation of 1cc of 1% lidocaine intratracheally at the end of the procedure can help deaden the cough reflex. Recovery in an oxygen-enriched environment also lessens respiratory distress after the procedure.

Technique

A bronchoscope with a distal insertion tip diameter < 5.0 mm is quite versatile in evaluating the airways of variety of animals, and the 5.0 mm or a 3.7 mm scope can be used in cats and most dogs. Most 5.0 mm diameter scopes have a relatively short working length - approximately 55 cm, however, an extended length scope (85 mm) is available from Karl Storz, Pentax, and Olympus. These are particularly valuable in examining dogs > 20 kg. Any endoscope purchased for bronchoscopy must have a biopsy channel to use for bronchoalveolar lavage. The channel can also be used to deliver oxygen throughout the procedure and to obtain biopsies or airway brushings.
General anesthesia is needed to perform bronchoscopy in order to suppress coughing and laryngospasm, to allow examination of the airways without inducing trauma, and to protect the endoscope. Pre-oxygenation with a facemask or nasal oxygen prior to bronchoscopy is highly recommended to improve the safety of the procedure. A variety of anesthetic agents and combinations can be used, and a protocol should be chosen that avoids excessive cardiopulmonary depression. Shortacting, reversible drugs are practical, and the use of a combination of anesthetic agents provides smooth and balanced anesthesia for the procedure. Propofol is also very popular for use during bronchoscopy.
Bronchoscopy can be performed using gas anesthesia if the animal is large enough for a 7-8 French endotracheal tube. A special T adapter is needed to pass the scope through the endotracheal tube while administering anesthetic gas. If the animal is not intubated, oxygen can be supplied through the biopsy channel of the bronchoscope at flow rates of 1-5 L/min. Caution must be exercised since excessive flow of oxygen can result in rupture of alveoli and pneumothorax. Oxygen flow should always be withdrawn when a segment is being wedged for BAL. Rather than supplying oxygen through the bronchoscope, a sterile feeding tube can be inserted into the trachea during bronchoscopy for delivery of oxygen. In small patients, use of jet ventilation during intravenous anesthesia is helpful in maintaining oxygenation. [...]