Intrathoracic airway obstruction and gastroesophageal reflux: a canine model

Gastroesophageal reflux (GER) is common in children with airway disorders. Previous studies have shown an association between upper airway obstruction and GER in experimental animal models. However, the cause and effect relationship between intrathoracic airway obstruction (IAO) and GER is obscure. The goal of this study is to investigate the association between IAO and GER using the canine model.

In sedated dogs, a telemetric implant was placed subcutaneously (with one pressure sensor tip each in intrapleural space and abdomen) to monitor intrapleural pressure (IPP) and intrabdominal pressure (IAP). The IPP and the IAP were monitored intraoperatively and in conscious dogs on the 7th to 10th postoperative days. GER was assessed by determining the reflux index (RI), based on the intraesophageal pH recording performed continuously for a 24 hr period using a pH probe. After 2-3 weeks following placement of the telemetric implant, IAO was surgically created in the dog. After maintaining IAO for 2 weeks, the IPP, IAP, and pH measurements were monitored again following the same protocol as before IAO.

After the creation of IAO, there was no significant change observed in the mean RI either in the distal (P = 0.716) or proximal (P = 0.962) esophageal lumens. The IPP became significantly more negative (P = 0.006) and the IAP turned significantly negative (P < 0.001) from being positive compared to the respective values before IAO. However, transdiaphragmatic pressure (Pdi) did not change significantly (P = 0.08).

We conclude that moderate IAO does not cause GER in our animal model. It can be explained by the absence of significant change in Pdi after creation of IAO.