Transtracheal aspiration (TTA), also called a transtracheal wash (TTW), is the insertion of a catheter into the trachea and upper airway of a sedated dog to collect fluid samples lavaged from the lower airway.
A variant of the technique is to intubate the airway of an anesthetized dog with a sterile endotracheal tube and to obtain the fluid sample via this tube. Fluid can be collected directly from the endotracheal tube or from a catheter inserted through this tube into the lower airway. This procedure is also referred to as a bronchoalveolar lavage (BAL).
What Does Transtracheal Aspiration Reveal?
Transtracheal aspiration is performed as a diagnostic aid to help determine the cause of coughing or other respiratory signs caused by acute or chronic bronchitis, pneumonia, or other forms of lower airway disease. It is often possible to identify bacterial, parasitic, fungal, and allergic causes of bronchopulmonary disorders. TTA is less helpful in identifying disorders caused by viruses or tumors.
Analysis of fluids obtained by TTA can also help to determine the prognosis for recovery from smoke inhalation and chemical injuries of the airway.
How is Transtracheal Aspiration Performed?
Transtracheal aspiration is performed by injecting a small volume of fluid into the airways, and then suctioning out the fluid for later examination.
In dogs, TTA usually only requires local anesthesia and mild sedation. An area of skin on the underside of the neck below the larynx is shaved and sterilized. Local anesthetic, usually lidocaine, is injected into the skin. A small incision is made through the skin over the trachea. That section of the trachea is gently elevated and a needle is inserted through the skin incision and passed between the cartilaginous rings of the trachea. The tip of the needle should come to rest in the lumen of the trachea. A long intravenous catheter is inserted through the needle and advanced within the lumen of the trachea (windpipe). The catheter is advanced until reaches the lower airways. Once the catheter is in place, the needle is withdrawn from the skin but the catheter is left in place.
A syringe containing sterile saline or an electrolyte solution is attached to the catheter. The solution is injected into the airway, which often causes the animal to cough. The fluid is then aspirated (suctioned) back into the catheter. The fluid is then analyzed under a microscope.
Is the Procedure Painful?
Because the procedure is usually performed under local anesthesia and mild sedation, there is little pain or distress involved. There may be some minor discomfort expressed following the procedure.
Is Sedation or Anesthesia Required?
TTAs are usually performed in conscious animals. Many dogs require mild sedation. Ill or weak animals may only require manual restraint.