Final answer:
In the case of a tracheoesophageal fistula where oxygen saturation is decreasing and airway pressures are rising due to possible ETT obstruction or displacement, the next appropriate step is to replace the endotracheal tube in order to re-establish a patent airway and resolve the urgent respiratory issue.
Step-by-step explanation:
In the scenario where a patient with a tracheoesophageal fistula (TEF) is experiencing a drop in oxygen saturation and difficulty with positive-pressure ventilation during surgery, the immediate concern is ensuring adequate oxygenation and ventilation of the patient. The description suggests that the endotracheal tube (ETT) may be obstructed by mucus and clots, or possibly dislodged. The next most appropriate action would be to replace the ETT to re-establish a clear airway, as this action directly addresses the critical issue of airway compromise. Administering albuterol or placing an arterial line do not address the immediate need to secure a patent airway, and asking the surgeon to occlude the gastrostomy tube does not relate to the immediate problem of the obstructed ETT.