Clearing the airway - DVM
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Clearing the airway
Studies show equine nasal strips reduce airway resistance and mitigate exercise-induced pulmonary hemorrhage.


DVM360 MAGAZINE


An opposing viewpoint

Offering different results, Goetz et al 2001 demonstrated that "application of an external nasal dilator strip neither improved the exercise-induced arterial hypoxemia and hypercapnia nor diminished the lactate and ammonia production or the incidence of EIPH in Thoroughbred horses performing strenuous exercise."9

Poole, however, takes issue with this study. "When the paper clearly disagreed with us, we were blown away by their poor methodology and the misinterpretation of their own and other scientists results," he says.

One significant difference with this study was the method of measuring EIPH, which was not via BAL.

"The technique used by Goetz and colleagues could not even be expected to detect a reduction in EIPH, as they did not use BAL to measure the red blood cells in the lavage from the respiratory tract," Poole says. "They merely evaluated by eye how much blood was in the large airways and used a very crude rating scale."

Erickson agrees that the use of BAL is key. "About 15 to 20 years ago, as they were using lavage in people, I went to Ireland to visit with Ursala Fogerty, DVM, PhD, at the Irish Equine Center. She did her PhD on BAL, looking at hemosiderin in the BAL fluid," he says. From what he learned, Erickson and his colleagues began using BAL to measure the severity of EIPH. About 150 ml of saline solution is infused into the lungs and about 60 percent of that fluid is then recovered.

"One can actually count the number of red blood cells within the BAL to better quantify the severity of EIPH," Erickson says. Although it is not practical on the racetrack or for the clinical veterinarian (where endoscopy is used), it is a useful method experimentally. "BAL is a well-recognized experimental assessment because of its accuracy in measuring red blood cells within the lavage fluid," he says.

A second difference was the placement of the nasal strips. The paper, when presented as a poster presentation, included a photograph of their horses wearing the nasal strips.

"What was most striking was the misplacement of the nasal strip," Poole says. "They were much higher on the face than specified in the instructions. The correct placement of the strip is just rostral to the nasoincisive notch. When you look at a horse skull, you can clearly see where the nasal passages are unsupported by bone. Remember that the horse needs to generate very high negative pressures to inhale at up to 60 L/s per nostril." This pressure is what generates the compressive forces on the soft tissues, causing nasal passages to narrow.

A third deficiency of this study was in neglecting to measure gas exchange. "The title of their paper proposed some results that were not even tested scientifically within the methodologies of the paper," says Poole. "One was EIPH, and the second was gas exchange (they measured blood gases, which are something else entirely). If you look at the blood gases of the horse, they're hypoxemic, hypercapnic—i.e., low O2, high CO2—because the lungs just can't do as good a job oxygenating the blood as the heart does pumping that blood around the body. Measuring blood gases doesn't reflect gas exchange. Case in point—the Thoroughbred horse running at maximal exercise, about 40 mph, has an oxygen uptake about 150 times higher than a human lung disease (COPD) patient but may have roughly the same blood gases (hypoxemic and hypercapnic). The bottom line is that blood gases don't tell you anything about gas exchange, as the COPD patient has abysmal gas exchange, while that of the Thoroughbred horse is superb."

Conclusion

Based on the research available, it is apparent that use of external nasal strips positively affects both the structure and function of the nasal passages in exercising horses. By resisting their collapse, the nasal strip maintains the diameter of the nasal passageways, thereby reducing upper airway resistance and improving airflow. This has been shown to reduce the severity of EIPH and likely improve overall performance. Once thought to be just a quirky fad, these simple devices may pose a legitimate adjunct or alternative to the use of furosemide in racing horses.

Ed Kane, PhD, is a researcher and consultant in animal nutrition. He is an author and editor on nutrition, physiology and veterinary medicine with a background in horses, pets and livestock. Kane is based in Seattle.


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Source: DVM360 MAGAZINE,
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