Quantitative methods that have been described for BOAS assessment include Whole Body Barometric Plethysmography (WBBP) and Exercise Testing (ET):
1. WBBP involves placing the dog in an enclosed barometric chamber and taking numerous measurements (such as respiratory rate, inspiratory volume, expiratory volume) to assess respiratory function. While it is useful in a research setting, it is not a very practical or available thing to do in general practice.
2. Exercise testing is a fairly simple thing to do, and can even be done yourself at home. (NB. An exercise test is NOT recommended for dogs with significant clinical signs, as it may push them into life-threatening respiratory distress.) Two types of exercise test have been described – the 5-6 minutes walk test (which assesses upper and lower respiratory function), and the 3 minute trot test (which more effectively evaluates upper respiratory function – the main problem for brachycephalic breeds). Measurements of distance covered, heart rate, respiratory rate, oxygenation and rectal temperature are taken before and after exercise. Dogs are also assessed for changes to respiratory noise, breathing effort and/or difficulty after exercise.
Reasonable correlation has been found between exercise testing and WBBP results, as far as grading the severity of BOAS symptoms is concerned. Given the confinement of WBBP to a research setting, the rest of this discussion will relate to exercise testing only.
So….. does exercise testing change our advice?
In short – probably not. Any dog showing symptoms on examination will have an improved quality of life with corrective airway surgery. We do not need an exercise test to diagnose these patients. Where exercise testing may be helpful is in those patients that are symptom-free at rest. Try trotting your dog for 3 minutes – a normal dog should not experience breathing noise or shortness of breath after such a short period of activity. Having said this, we strongly believe that even symptom-free dogs benefit from early correction of airway abnormalities, as we know that this is a progressive condition. Perhaps the most useful application of exercise testing would be for evaluating response to surgery – one published study has documented a significant increase in distance walked, decrease in respiratory rate and increases tissue oxygenation 6 weeks after airway surgery.
Conclusions:
1. Exercise testing increases the sensitivity of an examination for BOAS diagnosis, but probably does not affect the indications for surgical correction.
2. Exercise testing is probably more useful for assessing response to surgery, rather than for assessing the need for surgery.
3. While dogs that have no change to respiratory noise or effort after exercise testing may be deemed ‘not clinically affected’, we know that this is a progressive condition and this situation will likely change. This leaves us with a choice of monitoring by repeat exercise testing and making the decision to correct airway issues as soon as early changes are detected OR correcting airway abnormalities regardless, in order to prevent or delay progression to symptoms. Based on our clinical experience, early surgical correction of airway abnormalities (at 8 -12 months of age) is advisable, even in symptom-free dogs.
