Paradoxical breathing and pleural space disease in dogs & cats | VETgirl Veterinary Continuing Education Podcasts

In today’s VETgirl online veterinary continuing education podcast, we discuss paradoxical breathing in our canine and feline patients. As we all know, pleural space diseases like pleural effusion, pneumothorax and diaphragmatic hernias can sometimes be difficult to diagnose. You might not always hear obvious muffled heart or breath sounds, and often our veterinary patients aren’t stable enough for radiographs right away. In one study of dogs with pleural effusion, almost 1/3 died during initial examination and diagnostics!1 Remember, we always want to rapidly identify and stabilize our dyspneic patients to maximize survival and patient comfort!

It has been suggested that paradoxical breathing (that is, when the abdomen moves inward as the chest expands on inhalation, and moves outward as the patient exhales) indicates pleural space disease. This relationship hasn’t been investigated in clinical patients. So Le Boedec and all out of France wanted to see if paradoxical breathing correlated with pleural space disease in small animals, and looked at cases retrospectively.

Between 2001-2009 at the National Veterinary Schools of Toulouse and Alfort in France, 389 dyspneic dogs and cats (195 dogs, 194 cats) were identified. 53/195 (27%) dogs and 125/194 (64%) cats had paradoxical breathing, and 29/195 (20%) dogs and 91/194 (47%) cats had pleural space disease. There were no significant differences in patient characteristics between groups except for canine weight, which was different between those with or without pleural space disease. In the canine patients, the diagnosis of pleural space disease was much higher in dyspneic dogs with paradoxical breathing (26/53, 49%) than in those without paradoxical breathing (13/142, 9%). Paradoxical breathing was 67% sensitive and 83% specific to predict pleural space disease (PPV 0.49, NPV 0.91).

The dogs that had pleural space diseases had effusion (85%), pneumothorax (12%) and pyothorax (4%). In the cats in this study, pleural space disease was also much higher in those with paradoxical breathing (82/125, 66%) than in those without paradoxical breathing (9/69, 13%), with a sensitivity of 90% and specificity of 58% (PPV 0.66, NPV 0.87). Underlying pleural space diseases in the feline patients included effusion (66%), pneumothorax (28%), diaphragmatic hernia (5%) and pyothorax (1%). In the multivariate analysis, odds ratios between pleural space disease and paradoxical breathing were > 10 in both species.

So how do I interpret this study as a criticalist who sees dyspneic patients all the time? Overall, there were some limitations to this study: it was retrospective, which means the data is based on the accuracy of keeping good medical records – cases might have been missed if the clinician didn’t record the breathing pattern, or write that the patient was dyspneic, or they may have been excluded because radiographs weren’t obtained. Honestly, I’ve never written down on a SOAP that my patient has paradoxical breathing (unless it’s a flail chest, sometimes), so this makes me worried about how accurate the extraction of data from the medical records was. Also, it’s important to remember that these results only apply to dyspneic patients, so patients with pleural space disease that weren’t dyspneic might have also been missed.

So, what can we take away from VETgirl podcast? Paradoxical breathing seems to be very strongly associated with pleural space disease in cats and dogs that are dyspneic. That said, there were both dogs and cats that had paradoxical breathing but didn’t have pleural space disease, and the specificities (especially in cats, 58%, versus dogs 83%) were not very high, so it can’t be considered a specific sign of pleural space disease. Because the positive predictive values weren’t very high in either species, it might be more appropriate to use the absence of paradoxical breathing as a way to help exclude pleural space disease rather than using its presence to alert us to pleural space disease. In other words, if a dog or cat doesn’t have paradoxical breathing, you probably don’t need to get ready to perform a thoracocentesis right away.

So, if you are triaging a dyspneic patient with paradoxical breathing and your exam findings are suspicious for pleural space disease, you might want to think about emergency stabilization with a thoracocentesis – remember, it’s diagnostic and therapeutic! When in doubt, consider implementing your ultrasound machine to perform a T-FAST to help you! Remember, the presence or absence of paradoxical breathing can be a hint at the underlying disease, but it isn’t superior to your physical exam skills, clinical signs, and history, so don’t rely on it entirely!

1. Mellanby RJ, Villiers E, Herrtage ME. Canine pleural and mediastinal effusions: retrospective study of 81 cases. J Sm Anim Prac 2002;43:447-451.
2. Le Boedec K, Arnaud C, Chetboul V et al. Relationship between paradoxical breathing and pleural space diseases in dyspneic dogs and cats: 389 cases (2001-2009). J Am Vet Med Assoc 2012;240(9):209-216.

NPV: negative predictive value
PPV: positive predictive value

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