Traumatic Tracheal Disease in Avian Patients
Presenting Author: Angela Lennox, DVM, Dipl ABVP (Avian)
Avian and Exotic Animal Clinic of Indianapolis , IN
Interpretive Review and comments by Dr. Nemetz:
Numerous causes of tracheal trauma have been reported in birds mainly from predator attacks or foreign agent injuries. Due to the great flexibility of the avian neck, extreme soft tissue damage to the neck seldom produces tracheal damage. Dr. Lennox focus in this paper was addressing the cause and incidence of tracheal damage subsequent to endotracheal intubation during anesthetic procedures. This is important as tracheal trauma often leads to tracheal strictures and subsequent respiratory compromise.
In humans, post intubation tracheal stenosis (constrictions) is most commonly caused by local ischemic necrosis produced by the inflated tracheal tube cuff. Cuffed intubation tubes are not recommended or used in avian anesthesia because of the complete tracheal rings found in birds and the increased risk of damage if cuffed tubes are used. If stenosis occurs, tracheal resection and reanastomosis is the most common therapy utilized.
So if cuffs are the main cause in humans, what could be the cause in our avian patients where cuffs are not used? Dr. Lennox found that the damage is not to the tracheal rings themselves but to the superficial layers with a severe inflammatory response producing vascular granulation tissue (fibroplasia).
Species reported seem to show an increased incidence in macaws, cockatoos, African grey and maybe amazon parrots.
This led Dr. Lennox look at the trachea in several species and found that the above species have a narrowing trachea as it descends from the glottis to the syrinx. In some species the narrowing is marked possibly increasing the risk of stenosis in these species.
This paper demonstrates the importance of proper intubation tube selection for anesthesia in our avian patients and being aware of the species variations that may increase one's risks. Other steps that can decrease the possibility of tracheal inflammation include rinsing disinfectants thoroughly from tubes and avoid kinking the trachea during procedures to reduce tube/tracheal wall contact.
Dr. Nemetz has seen tracheal strictures due to infection, neoplasia, and trauma but not due to post anesthetic complications. Several reason may contribute to this: All intubation tubes are custom made specifically for each species in consideration of an anesthetic procedure; the patient's head and neck are always held in a linear position, thereby minimizing any tube/wall contact; tubes are each individually cleaned, disinfected and dried between each procedure; and tube placement is maintained within the proximal 30% of the length of the trachea.