[Airway obstruction associated with gastroesophageal reflux: experimental study]

Gastro-oesophageal reflux (GER) frequently complicates the clinical course of children suffering from conditions leading to upper airway obstruction (UAO) (choanal atresia, tracheomalacia, oesophageal atresia, vascular rings etc.). In an attempt to explore whether partial airway obstruction causes changes in the normal thoraco-abdominal pressure gradients, we measured end-inspiratory intrathoracic and intra-abdominal pressures in anesthesized rats under spontaneous breathing conditions, after tracheostomy and under upper airway obstruction induced by tracheal intubation with three progressively narrower cannulae (inner diameters 1.0 mm, 0.5 mm. and 0.2 mm.). We also measured the lower oesophageal sphincter pressure (LESP) and length (LESL) and calculated the thoraco-abdominal end-inspiratory pressure gradient (TAEIPG). Neither LESP nor LESL changed significantly before or after maximal tracheal obstruction but TAEIPG significantly increased from 5.58 +/- 1.34 cm H2O to 17.62 +/- 4.27 cm. H2O (p < 0.01) under the same conditions, mainly as a result of progressively stronger intra-thoracic pressures during inspiration. These experiments prove that the powerful thoraco-abdominal pressure gradients developed after partial UAO may contribute to the pathogenesis of GER by overcoming the anti-reflux barrier function.