The effect of quiet tidal breathing on lateral cephalometric measurements

In the evaluation of the upper airway in patients with sleep apnea it has been suggested that cephalometric radiographs be performed at either end-inspiration or end-expiration during quiet tidal breathing. This study sought to determine if standard soft tissue cephalometric measurements vary significantly with tidal breathing.

In this prospective, controlled study 22 adult male patients with the sleep apnea/hypopnea syndrome and 27 nonapneic, nonsnoring male controls had cephalometric radiographs performed at end-tidal inspiration and end-tidal expiration. The measurements obtained from each radiograph included the posterior airway space distance, the mandibular plane to hyoid distance, and the posterior nasal spine to tip of palate (PNS-P) distance.

There were no statistically significant differences between the inspiratory and expiratory measurements in either group. Only the PNS-P distance differed significantly between the two groups. Changes in cephalometric measurements did not occur uniformly in any one direction with tidal breathing.

The data indicate that coordinating radiographic exposure to respiratory cycle phase is not necessary for soft-tissue measurements commonly used to assess upper airway patency in patients with the sleep apnea/hypopnea syndrome.