Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that Sapphire has been suffering from wheezing like episodes, with noises like she is trying to push something out of her nose, and today on her walk this was followed by open mouth gagging. This sounds like episodes of reverse sneezing.
Do your girl's episodes look like the dog in the video in the link below?
Dogs that are overweight do tend to suffer from more upper respiratory difficulties as they tend to have more obstruction and loose tissue around the soft palate/pharynx. That could explain her episodes somewhat.
But her weight may not he whole picture/cause.
Reverse sneezing episodes can be secondary to inhaled irritants and how sensitive she is to them. They can be related to respiratory infections. They can be related to gastroesophageal reflux, excitement or post nasal drip or an overlong soft palate. Sometimes dogs will inhale a piece of plant material and until it dislodges they will have episodes.
In most cases these episodes can be stopped by rubbing her throat and getting her to swallow, so I would try that maneuver as soon as she starts. While these episodes aren't harmful as it's just a spasm of the muscles around the pharynx because of the irritant, it's no fun to watch and in her case it sounds like they are somewhat interfering with her quality of life because she is having several and led to her gagging this morning on her walk.
If it is because of gastroesophageal reflux then using Pepcid-ac (famotidine) may help. Give her Pepcid-ac (or generic famotidine) at a dose of 0.25mg to 0.5mg per pound of body weight orally every 12 hours for 2 to 3 weeks. That's one quarter of a 10mg tablet per 5 to 10 pounds of body weight every 12 hours. If this helps she can stay on it as needed as Pepcid is quite safe. You can even try once daily therapy before bed at night after a couple weeks. Reflux tends to happen more when dogs are laying down and sleeping as the gastroesophageal sphincter relaxes and acid can passively reflux up into the esophagus and pharynx. This irritant only causes more tissue swelling, thus dogs with reflux will also snore more. It may help her to get her to sleep with her head raised.
If it is related to an overlong soft palate then surgery may be required eventually if this is interfering with her enjoyment of life or leading to breathing problems.
Sometimes reverse sneezing can be related to dental or gum disease and the secondary inflammation from chronic infections. If this is the case a good cleaning should improve things tremendously.
Rarely this can be related to an inner ear infection and the effects of the infection dripping down his throat.
Another rare cause would be a pharyngeal or laryngeal polyp or tumor.
Foreign material snorted up into her nose (a blade of grass, plant awn, chunk of food) can also cause episodes of reverse sneezing.
Sometimes we need to sedate them and take dental radiographs and examine the pharynx and up behind the soft palate to find the cause, so that is always an option if this is worsening for her.
Please let me know if you have any further questions.