The association between gastroesophageal reflux (GER) and upper airway obstruction in children is recognized but not well understood. Our objective was to determine if the creation of a model of upper airway obstruction in dogs would cause GER and to determine if the GER is related to intrathoracic pressure changes. Five dogs underwent evaluation with esophageal manometry and pH probe at baseline and 1 week after creation of an upper airway obstruction. Airway obstruction was created by placement of a fenestrated cuffed tracheostomy tube, which was then capped and the cuff was inflated, requiring the animals to breathe via the fenestrations. The negative inspiratory pressure (Pes) (+/- SD) increased from 11.8 +/- 4.8 cm H(2)O at baseline to 17.6 +/- 4.9 cm H(2)O 1 week after creation of an airway obstruction (p = .029). None of the dogs had GER at baseline with a reflux index (RI) value of 0.0; however, 1 week after creation of airway obstruction, three out of five dogs had GER, with a mean RI value of 21.2 +/- 21.2. There was a significant (p = .023) correlation (r = .928) of the changes in Pes and RI values following airway obstruction. Upper airway obstruction (UAO) does cause GER in this canine model. Severity of GER is significantly correlated with Pes changes.

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Although the differential cell counts in the dogs' BAL fluid was comparable to that of other experimental animals and humans, the LLMI was distinctly higher than the corresponding value reported for other species. As LLMI is a valuable modality for evaluation of intrapulmonary pathophysiology, these data on LLMI can be used as a species-specific standard for canine subjects used for experimental studies on GER and airway diseases.

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