Endoscopically-directed sinus potential difference (EDSPD) will be conducted in either the operating room or in the rhinology clinic setting to quantify CFTR activity in the sinus cavities. The potential difference will be monitored in actively inflamed areas as judged by endoscopy in comparison to an agar-filled reference butterfly electrode placed in the volar aspect of the forearm. A stable potential with the mean value of a 10-s scoring interval after perfusion of each solution will be recorded by a blinded investigator.

Endoscopically-directed sinus potential difference (EDSPD) will be conducted in either the operating room or in the rhinology clinic setting to quantify CFTR activity in the sinus cavities. The potential difference will be monitored in actively inflamed areas as judged by endoscopy in comparison to an agar-filled reference butterfly electrode placed in the volar aspect of the forearm. A stable potential with the mean value of a 10-s scoring interval after perfusion of each solution will be recorded by a blinded investigator.

The equipment & conditions for measuring bioelectric changes across the sinus mucosa are based on the standard NPD protocol, including use of agar-filled PE90 tubing for the probing electrode and limiting perfusion solutions to Ringer, Ringer + amiloride (100 µM), chloride-free gluconate with amiloride + isoproterenol (10 µM). The potential difference will be monitored in actively inflamed areas as judged by endoscopy in comparison to an agar-filled reference butterfly electrode placed in the volar aspect of the forearm. A stable potential with the mean value of a 10-s scoring interval after perfusion of each solution will be recorded by a blinded investigator.

To establish the relationship of EDSPD findings with other validated instruments and markers of CRS disease