Effect of salicylate on upper airway stability and pressure flow: relationship in anesthetized dogs.

Previous studies have shown that upper airway muscle activity is augmented in response to increased respiratory drive, thereby improving upper airway patency. In the present study we evaluated the effect of salicylate, a well-known respiratory stimulant, on upper airway stability and pressure-flow relationship. Multiple levels of airflow were used to assess pressure-flow relationship in the isolated airways of anesthetized dogs and to calculate the coefficients of Rohrer's equation P = K1V + K2V2. In addition, we measured the negative intraluminal pressure needed to collapse the upper airway. These measurements were repeated after intravenous administration of sodium salicylate, 250 mg/kg. Salicylate-induced hyperventilation was associated with increased alae nasi electrical activity. Resistance to airflow and K2 decreased significantly (p less than 0.01), suggesting dilation of the upper airway lumen. The intraluminal pressure under which upper airway collapse occurred became more negative in all dogs (from -5.0 +/- 0.8 to -8.5 +/- 1.3 cm H2O, p less than 0.01), indicating improved stability of the upper airway walls. These findings suggest that salicylate, and presumably other pharmacologic agents that stimulate ventilation, can improve both upper airway patency and upper airway stability.