TRACHEAL COLLAPSE - ARE THERE SURGICAL OPTIONS??

D. M. Tillson, DVM, MS, Diplomate ACVS
Auburn University College of Veterinary Medicine
Auburn University, Alabama

INTRODUCTION

Tracheal collapse is a progressive condition associated with small breed dogs that results in significant respiratory distress. It is primarily found in small breed dogs such as Yorkshire terriers, toy poodles and Pomeranians. The cervical trachea is most commonly affected but the collapse can extend along the thoracic trachea down to and including the main stem bronchus.

The pathogenesis of tracheal collapse is believed to be caused by chondrodysplasia or softening of the cartilage rings in the trachea. A slow loss of structural integrity occurs. This results in the trachea deforming, especially during inspiration, causing a decrease in the cross-sectional area of the tracheal lumen. The smaller lumen results in increased respiratory effort and decreased intralumenal pressures, placing even more stress on the cartilage. This constant stress is suspected to hasten the progressive nature of tracheal collapse.

Clinical signs associated with tracheal collapse include: coughing, stertorous breathing, exercise intolerance, heat intolerance and cyanosis. In severe cases, the condition may progress to complete respiratory arrest and collapse. Many dogs are unable to sleep comfortably due to the difficulty breathing and consequently the owners are unable to rest.

Diagnosing tracheal collapse is straight forward. However, many clinicians have the tendency to make the diagnosis with minimal supportive evidence and, in doing so, may overlook other reasons for the clinical signs such as cardiac disease or a primary respiratory problem.

Since tracheal collapse is a dynamic process, fluoroscopic examination is extremely useful in making the diagnosis. During fluoroscopic examination, the actual changes in a patient's trachea can be observed. In most situations, complete occlusion of the tracheal lumen can be seen.

Warn owners of potential risks of placing a suspected tracheal collapse dog under general anesthesia.

Prompt surgical intervention may be required before the animal can recover.

My final (and definitive) diagnostic procedure is a tracheoscopic examination. This can be accomplished with a small flexible endoscope (3 mm) or with a rigid arthroscope. Unlike other diagnostic procedures, general anesthesia is required for visual examination. The scope is guided into the trachea and advanced until the tracheal bifurcation is seen. I find I have the best visualization while withdrawing up the trachea.

Direct visualization of the tracheal lumen allows for the assignment of a grade to the disease. The standard scale for grading tracheal collapse is presented in table 1. I feel that the diagnosis of tracheal collapse is not complete until the tracheal lumen has been visualized. 

Dorsal Membrane Plication. Dorsal tracheal membrane (tracheales muscle) plication can be an effective method of holding the dorsal tracheal membrane so that it does not hang into the tracheal lumen. A ventral midline incision is made and the trachea is rotated, exposing the dorsal tracheal membrane. Grasping the dorsal tracheal membrane, mattress sutures (using fine, non-absorbable, monofilament polypropylene suture material) are placed, everting the membrane out of the tracheal lumen. This is repeated along the length of the cervical trachea. A smaller, more rounded trachea results once with the obstructing membrane pulled out of the lumen. Long term studies have not demonstrated the effectiveness of tracheal plication but it may have a place in the management of grade 2 tracheal collapse where the primary airway obstruction is caused by dorsal tracheal membrane laxity.

External Support. External support a flaccid or malformed trachea is the most common technique used for surgical management of tracheal collapse. This generally takes the form of custom created polypropylene rings or spirals inserted around the outside of the trachea. Each technique has positive and negative aspects (and converts); however, the techniques share a basic surgical approach.

The trachea is approached using a ventral cervical incision. I find elevating the head and neck with a towel helps maintain a level surgical field. The incision is made from the laryngeal cartilage to the thoracic inlet taking care to avoid entering the chest cavity. The sternohyoideus and sternocephalicus muscles are bluntly separated to exposure the ventral trachea. The recurrent laryngeal nerve, jugular vein, carotid artery and vagosympathethic trunk are each identified. Preservation of these structures during dissection and retraction is vital and will decrease complications. From this point on, the techniques differ based on the type of support to be used.

 Individual tracheal rings can be placed around the trachea. These rings are created from 3 cc syringe cases cut to widths of 7-10 mm. Six equally spaced holes are drilled through the ring to allow suture passage. The ring is cut over the 6^th hole to allow it to be placed around the trachea. The ring is secured by sutures encircling a tracheal ring and passing through the pre-drilled holes in the prosthesis.

Avoid jugular venopuncture or catheters when preparing to perform tracheal surgery.

Hematomas make nerve and vessel identification extremely difficult.

A spiral ring prosthesis is a 3mm wide polypropylene support created from syringe cases. Placement of the prosthesis involves the dissection of the left tracheal pedicle and perforation of the right tracheal pedicle as the prosthesis is placed along the length of the trachea. Dissection of the left pedicle allows retraction of the left recurrent laryngeal nerve. Care is take to place the spiral on the inside of the right recurrent nerve as it is passed around the trachea. The trachea blood supply is segmental and visible blood vessels are preserved. The spiral encircles the entire length of the cervical trachea into the thoracic inlet. Once in place, 4/0 polypropylene sutures are placed at 6:00 and 3:00 and 9:00 to pull the tracheal out to the prosthesis. The sutures tags on the 3:00 sutures are left long and are used to rotate the trachea so that sutures can be placed through the dorsal tracheal membrane (12:00 position). All sutures go around the spiral ring prosthesis and enter the tracheal lumen with knots on the outside. After all sutures are placed, the surgical site is lavaged and closed in a routine manner.

Reports of tracheal necrosis followed the initial publication of the spiral ring prosthesis technique causing a fall into disfavor. Excessive dissection around the trachea to permit easy passage of the spiral ring disruption of the segmental blood supply causing post-operative tracheal necrosis. Dissection of a single tracheal pedicle should maintain the blood supply thereby avoiding this complication. Nonetheless, I always warn owners of this potentially devastating complication.

Internal Support. The use of internal stenting devices such as those placed during angioplasty has been investigated for management of tracheal collapse. Unfortunately, experimental placements have failed to live up to expectations. Further investigation is required before this option becomes useful for clinically affected dogs.

The post-operative goals following tracheal collapse surgery are to maintain tissue oxygenation, manage pain, prevent excessive coughing and avoid infection. Prior to extubation, tracheal collapse patients should have a nasal oxygen cannula placed. Oxygen is given through the endotracheal tube until extubation and through the nasal cannula thereafter. Opioids are used for post operative pain management. At the same time, opioids, especially butorphanol, are effective cough suppressants. I frequently continue butorphanol (01-0.4 mg/kg IV or IM every 4 hours) once the initial pain is well controlled. Tranquillization with a very low dose of acepromazine (0.02-0.05 mg/kg IV or IM) enhances the effects achieved with opioids and helps relieve anxiety. Oral administration of butrophanol or hydrocodone (Hycodan) can be continued throughout the post-operative period and may be required long term. Placement of a permanent prosthesis is an indication for peri-operative antibiotic administration. I use either a first generation cephalosporin (22 mg/kg IV at beginning of surgery and then every 90-120 minutes) or ampicillin (25 mg/kg IV at beginning of surgery and then every 90-120 minutes). If oral medication is warranted after surgery, I use either Keflex elixir or Clavamox drops, at the standard dosages, every 8-12 hours.

I sometimes think I have encountered every complication possible with a tracheal collapse dog but I know that there are new complications lurking with a future patient. Despite that knowledge, I generally discuss complications with clients in terms of immediate vs acute vs chronic problems. Immediate complications include hemorrhage and laryngeal paralysis from recurrent laryngeal nerve injury. Hemorrhage is seldom life threatening although inadvertent injury to the jugular vein or carotid artery could result in significant hemorrhage. In most cases, digital pressure or ligation of the offending vessel will control this complication. Laryngeal paralysis is a more serious complication. Pre-operative examination for normal laryngeal function is always performed to document any pre-existing disease. While it is possible that the injury to the recurrent laryngeal nerve causing laryngeal dysfunction is temporary, surgical intervention is often required before sufficient time can pass to allow healing. In situations where laryngeal function has been compromised after placement of a spiral ring, unilateral arytenoid lateralization is indicated.

Acute complications include those seen in the post-operative period; generally a few days after the procedure. Excessive or constant coughing is a common problem. This may be due to tracheal inflammation(considering > 40 sutures are placed into the tracheal lumen), inadequate support of the trachea (especially with segmental support) or collapse of the trachea or mainstem bronchus distal to the external support. Medical management is the mainstay of these complications, although, surgical intervention may be considered in situations where there is segmental collapse or collapse just beyond the end of the prosthesis. Tracheal necrosis is the most dreaded complication associated with spiral ring placement. Necrosis takes several days and can result in increased coughing and subcutaneous emphysema. Although surgical exploration of the cervical neck is appropriate in suspected cases of tracheal necrosis, it is unlikely that anything more than a localized lesion could be resected with subsequent tracheal anastomosis.

Chronic complications include progression of the disease resulting in collapse beyond the supported portion and infection associated with the prosthesis. The technique for placing a spiral ring prosthesis covers the entire cervical trachea, often requiring the use of two sequential prostheses. Despite completely supporting the cervical trachea, it is possible to have localized collapse associated with tearing of the dorsal tracheal membrane away from the sutures or gaps in the support between rings. The use of oral antitussive agents and albuterol will control most of this coughing. In some cases, dogs respond better to one type of antitussive than another so try several different compounds before throwing in the towel.

Additional Readings/References

1. Fingland RB. Trachea - Treatment of tracheal collapse: spiral ring technique. In: Current Techniques in Small Animal Surgery; 4^th edition, Bojrab MJ, editor. Chpt 22. Williams & Wilkins. Philadelphia, 1998.

2. Hobson HP. Trachea - Treatment of tracheal collapse: ring prosthesis technique. In: Current Techniques in Small Animal Surgery; 4^th edition, Bojrab MJ, editor. Chpt 22. Williams & Wilkins. Philadelphia, 1998.

3. Fingland RB, DeHoff WD, Birchard SJ. Surgical management of cervical and throacic tracheal collapse in dogs using extraluminal spiral prostheses. JAAHA. 23; 163-172, 1987.

4. Hedlund CS. Tracheal collapse. Problems in Veterinary Medicine. 3:229-238. June 1991.

5. Kirby BM, Bjorling DE, Rankin JHG, Phernetton TM. The effects of surgical isolation and application of polypropylene spiral prostheses on tracheal blood flow. Vet Surg. 2; 49-54, 1991.

6. Coyne BE. Fingland RB. Kennedy GA. DeBowes RM. Clinical and pathologic effects of a modified technique for application of spiral prostheses to the cervical trachea of dogs. Vet Surg 22(4):269-75, 1993.

7. Buback JL. Boothe HW. Hobson HP. Surgical treatment of tracheal collapse in dogs: 90 cases (1983-1993). JAVMA. 208(3):380-4, 1996.