A diagnostic tool and methods of using the tool are provided to quantify an amount of nasal collapse in a patient. The diagnostic tool includes a mask with an endoscope port and an opening to allow air flow, an endoscope with a camera adapted to take an image of the nasal valve, and an air flow sensor adapted to measure an inhalation rate of the patient. The diagnostic tool can quantify a size difference between the nasal valve during inhalation and zero flow by calculating a percentage difference in an area or one or more dimensions of the nasal valve during inhalation and zero flow.