Simultaneous digitization of upper airway fiber-optic images and respiratory signals.

We developed an inexpensive and efficient method for simultaneously digitizing respiratory signals and fiber-optic images of the upper airway. The main components of the system are a fiber-optic scope, a charge coupled device video camera, and a personal computer equipped with a frame grabber and an A/D board. The frame grabber digitizes images at five frames per second while the A/D board samples six respiratory signals at 25 samples per second. Digitized images are saved only in the event that the user instructs the computer to do so in order to limit disk space requirements. A circular buffering technique provides continuous storage of the most recent 50 frames in frame grabber memory. This feature gives the user up to 10 seconds, following the beginning of a respiratory event, to initiate the saving of images to computer hard disk. A postacquisition program displays the data acquired during the sleep study and allows the user to interactively select images for subsequent upper airway area measurement. This system enables us to observe and quantify the dynamics of the upper airway during different breathing conditions with minimal time and cost. It is also a potential clinical tool to use to determine the site of obstruction during sleep in patients with obstructive sleep apnea.