Respiratory Interventions

Respiratory Interventions

Nasopharyngeal Stenting for Stenosis or Tumors

Nasopharyngeal stenosis (NPS) is a pathologic narrowing within the nasopharynx caudal to the choanae (back of the nose) resulting in a variable degree of respiratory obstruction. This can occur as a congenital anomaly or be acquired, most commonly after vomiting/regurgitation post-anesthesia, after surgery, trauma, or due to a tumor. Traditional therapy involves surgery or serial balloon dilatation procedures. Balloon dilatation is minimally invasive and utilizes interventional technique, but can result in re-stricture in a few days to a few weeks. We have found that stenting of this nasopharyngeal region allows for a more permanent fixation and results in both dogs and cats have been extremely promising.

Case example: “Tyler” is an 11 year old domestic short hair cat who presented for the inability to breath through her nose and was in severe respiratory distress, needing admission to the emergency room for immediate oxygen therapy. Due to the location of the noise it was suspected that she had a narrowing in the back of her nasal passage (called the nasopharynx). She was subsequently anesthetized and an endoscope was used to evaluate the back of her nose. Scar tissue was seen, making a very small hole for her to be able to breath through (see pictures below). We utilized a balloon and a stent to open up this region permanently, and she was discharged only 8 hours later without any discomfort or pain. Two years later she is doing very well, breathing normally, acting as if nothing ever happened.

nasopharyngeal stenosis
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Nasopharyngeal stenosis (NPS) in a cat. (A) Retroflexed endoscopic image of stenotic nasopharynx. (B) Fluoroscopic-guided placement of hydrophilic guidewire through nares and across NPS lesion with balloon-expandable stent (BEMS) mounted on angioplasty balloon passed over guidewire. (C) Fluoroscopic image of BEMS partially inflated demonstrating stenotic lesion identified as balloon waist. (D) Fluoroscopic image following complete balloon inflation demonstrating effacement of stenotic area. (E) Fluoroscopic image following balloon deflation and removal, leaving BEMS expanded and in place across previously narrowed NPS.

Tracheal Stenting for Tracheal Collapse

Tracheal collapse is a progressive, degenerative disease of the cartilage rings in which hypocellularity and decreased glycosaminoglycan content leads to dynamic tracheal collapse during respiration. This is a condition of predominantly middle-age, small and toy-breed dogs which can present with signs ranging from a mild, intermittent “honking” cough to severe respiratory distress from dynamic upper-airway obstruction. Many of these animals are palliated with medications including anti-inflammatories, cough suppressants, and bronchodilators. Candidates for surgical therapy are those that have failed initial conservative medical management.

Various surgical techniques have been described however the currently recommended surgical therapy is extraluminal polypropylene prostheses. This technique involves placing extraluminal support rings around the trachea during an open cervical approach and has a reported 75%-85% overall success rate in 90 dogs for reducing clinical signs.15 This procedure is not without complications however. The same study reported that 5% of animals died peri-operatively, 11% developed laryngeal paralysis from the surgery, 19% required permanent tracheostomies, and 23% die of respiratory problems with a median survival of 25 months. More importantly, only 11% of the dogs in this study had intra-thoracic tracheal collapse (all dogs had extrathoracic tracheal collapse). The authors advised against this technique in animals with intra-thoracic tracheal collapse as the associated morbidity was unacceptably high.

Due to the relatively high morbidity associated with surgery, the use of intra-luminal stents has been investigated. A number of stents have been evaluated in the canine trachea, including both balloon-expandable (Palmaz), and self-expanding (Stainless steel, Laser-cut nitinol, Knitted nitinol) stents. Clinical improvement rates in 75%-90% of animals treated with self-expanding, intra-luminal stainless steel stents have been reported. Immediate complications were mostly minor although there was a peri-operative mortality rate of approximately 10%. Late complications included stent shortening, excessive granulation tissue, progressive tracheal collapse, and stent fracture.

The advantages of intra-luminal tracheal stenting include minimal invasiveness, avoiding dissection around the peri-tracheal neurovascular structures, shorter anesthesia times, and access to the entire intra-thoracic trachea. While most commonly performed under fluoroscopic guidance, some are now placing tracheal stents under endoscopic guidance. The search for a better intra-luminal tracheal stent continues and long-term studies will be necessary to determine late effects of these stents on the trachea and whether the progression of the tracheal collapse syndrome can be prevented or delayed through earlier intervention.

Chylothorax: Glue Embolization of the Thoracic Duct

Idiopathic chylothorax is a frustrating disease to manage in which the pleural space fills with a chylous effusion resulting in dyspnea and sclerosing pleuritis over time if left untreated. Numerous surgical techniques have been described with varying success and invasiveness. Recently, thoracoscopic treatment has been described. Another less commonly considered technique is that used in humans which involves glue embolization of the thoracic duct using cyanoacrylate. This technique has been evaluated experimentally in animals as well as in a small number of clinical patients. This technique is performed under fluoroscopic guidance through an abdominal approach and involves performing lymphangiography with subsequent glue embolization of the cisterna chyli and thoracic duct. Glue embolization may be a viable primary therapy or follow-up treatment if a previous surgical attempt has failed.

glue embolization
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Thoracic duct glue embolization for idiopathic chylothorax. (A) Contrast lymphangiogram through 22 gauge catheter surgically placed into efferent mesenteric lymphatic vessel demonstrating lymphatics, cisterna chyli and thoracic duct. (B) Radiograph post-glue embolization demonstrating thoracic duct branches filled with cyanoacrylate glue. Notice the many individual branches filled with this liquid mixture.

Nasal Bleeding (Epistaxis): Arterial Embolization

Tracheobronchial Foreign Body Retrieval

Tracheal foreign bodies are seemingly uncommon to encounter. When you do, having a fast, safe, and effective approach for retrieval is imperative. Most internists would use an endoscope and grasper or basket. In very small animals this requires extubation and a very small endoscope, which can result in hypoxia, hypercarbia and minimal or no ventilation. Using endoscopy with a retrieval basket, in conjunction with fluoroscopy, helps to guide you to the object and watch the wires entrap the prior to removing the basket.  For radiolucent objects this would be done with endoscopy alone, but for radio-opaque material this can be easily done with a retrieval basket and fluoroscopy alone, directly through the endotracheal tube, preserving ventilation (see presentation) and foregoing the need for tracheoscopy.