Laryngeal Collapse

The larynx is a cartilaginous opening that connects the upper respiratory tract to the lower respiratory tract (windpipe and lungs). Laryngeal collapse is a secondary change that occurs due to progressive BOAS.

In dogs with BOAS, increased upper airway resistance causes increased negative pressure within the larynx, and this in turns causes weakening and deformation of the cartilage (laryngeal collapse). Once the cartilages becomes weak, ongoing increased inspiratory effort will cause progression through each stage of collapse. Early airway correction is the best way to prevent or delay the occurrence & progression of laryngeal collapse. The rate of progression is variable in each individual dog, and is hard to predict. It is likely that overweight dogs will have a more rapid progression.

There are three stages of collapse. The higher the stage of collapse, the greater the severity of symptoms. In any dog with laryngeal collapse, symptoms will likely be worse with exercise and in warm weather. It is important to note however, that any dog with untreated BOAS can experience symptoms of concern without any inciting cause, and this risk if higher in dogs with laryngeal collapse.

Stage 1 is eversion of the laryngeal saccules.

Stage 2 is a partial collapse of the cartilage folds, causing narrowing of the laryngeal opening.

Stage 3 is collapse of the entire cartilage folds, leading to closure of the laryngeal opening.

Stage 1 collapse is unfortunately fairly common as it is an early secondary change. The two membranous linings of the laryngeal ventricles (also known as the laryngeal saccules), are easily sucked out of their normal location with minimal increases in upper airway pressure. When this occurs, the everted saccules obstruct the base of the opening into the larynx. Fortunately, Stage 1 collapse is easily treatable by surgical removal of the saccules, and dogs show a marked improvement when this is done along with appropriate surgical correction of other BOAS concerns (nares, soft palate, tonsils). The overall prognosis is good.

The prognosis for Stage 2 collapse is not as good, as this is an irreversible change. Correction of existing BOAS concerns becomes even more important in this situation in order to delay or prevent progression to Stage 3. Most patients show significant improvement after surgery, but have a reduced chance of the best long term result, and will likely maintain some degree of BOAS symptoms. The risk of complications in the immediate post-op period if also significantly higher.

Stage 3 collapse is life-threatening and carries a guarded prognosis, as complete collapse of the laryngeal opening dramatically affects the dog’s ability to breathe. It is not surgically reversible or correctable. Partial resection of some of the collapsed cartilage obstructing the larynx can be considered, but carries a reasonable complication rate. The most effective solution for dogs with Stage 3 collapse is a permanent tracheostomy – a surgical procedure that creates a direct opening into the windpipe on the underside of the neck, and thus bypasses the entire obstructed upper respiratory tract. Dogs with a permanent tracheostomy require lifelong ongoing aftercare, but can lead an active comfortable life.

Main points:

• Laryngeal collapse is a secondary change in BOAS
• Early airway evaluation and appropriate surgery is recommended for all brachycephalic dogs to prevent, minimise or delay the impact of laryngeal collapse
• Without surgery, laryngeal collapse will be highly likely to progress
• Dogs with Stage 1 collapse have a very good prognosis after surgery
• Dogs with Stage 2 collapse potentially also have a very good prognosis, but will likely retain a degree of BOAS symptoms and require some ongoing management (see below)
• Stage 3 collapse is a severe and life-threatening end-stage BOAS change
• Dogs with Stage 3 collapse are best treated with a permanent tracheostomy

 

How to care for your dog with laryngeal collapse:

• Have airways assessed and surgically corrected to maximise your dog’s ability to breathe
• Avoid weight gain – overweight dogs have additional tissue at the back of their throat which contributes to airway obstruction
• Be careful with exercise in warm weather (ambient temperatures greater than 22 degrees are considered ‘warm’ for a brachycephalic breed dog)