The contribution of this study was to present the use of a cephalometric analysis, commonly used in orthodontics, with the aim of identifying anatomical changes in the upper airways, which may predispose to respiratory disorders.
Cephalometric performed by means of lateral teleradiography has been shown to be an important instrument in the multidisciplinary field for evaluating the upper airways [13, 14] because it is easily accessible and low cost, highly reproducible, and the individual is submitted to a low dose of radiation [4, 15]. Thus, innumerable studies have sought associations of the physical characteristics related to these airway spaces, as a way of predicting pathologies [13,14,15,16,17,18,19,20].
However, there are studies that use computed tomography for morphological evaluation of the airway spaces, particularly due to the possibility of measuring areas and volumes, which is impossible to do by means of other radiographic exams [21,22,23]. Therefore, the authors point out that one of the limitations of the present study refer to not measuring the airway volumes, due to the type of exam used for evaluation . There was also difficulty in the methodologies with two-dimensional radiographs when performing superimposition of tracings ; however, in the present study, no superimpositions were made. Many studies have evaluated the airways by using lateral cephalograms and associated their dimensions with the vertical skeletal pattern of the face and facial morphology [1, 26, 27]. A recent longitudinal study also used lateral cephalometric radiographs for associating changes in the morphology of the nasopharyngeal space in different facial patterns , which did not make this method of evaluation unfeasible.
In this study, the authors opted to use the sleep apnea cephalometry instrument because it has been validated for Brazilians and presents standard values that may be used as reference .
The authors were able to identify reduction in the median posterior palatal space in individuals with a dolichofacial pattern. A previous study also observed changes in the dimensions of the upper airway related to the reduction in the medial posterior palatal space in individuals with the obstructive sleep apnea syndrome (OSAS) . This measurement expresses the distance from the soft palate to the posterior wall of the pharynx and has a close relationship with the dimensions of the soft palate. The increased length of which was related to presence of OSAS in other researches [8, 29, 30] and the present study. The highest alteration values in upper airway dimensions in OSAS patients occur in the oropharynx  and were related to the reduction of the median posterior palatal space . In individuals with a vertical pattern, the mandible is normally retracted and rotated downwards and backwards, thus diminishing the oropharyngeal space  Furthermore, the base of the tongue accompanies the direction of mandibular rotation, being positioned downward and backward, thus the soft palate is in a more retrusive position, diminishing the median posterior palatal space.
Some authors have pointed out that when the nasopharyngeal space was reduced, there would be a tendency towards neuromuscular adaptation, leading to vertical growth of the face that is associated with a dolichofacial pattern [14, 21]. However, in this study, no difference was found in the upper airway dimensions in the nasopharyngeal region in the studied volunteers with this facial type. This could be attributed to different sample characteristics in others studies in which the sample was composed of the youngest participants [1, 26]. This aged group could be more susceptible to narrower nasopharyngeal airway spaces due to adenotonsillar hypertrophy, for example [32, 33]. In addition, authors  compared Angle Classes I and II, differently from the present study, in which the sample was composed of only Class I patients.
Obstruction of the upper airways forces the patient to breathe through the mouth, and in addition to OSAS, these factors cause oral dysfunction, such as lip incompetence, low position of the tongue in the floor of the mouth, tongue thrust, and may lead to unbalanced muscle and function  disturbances in swallowing, mastication, speech , and stability of occlusion .
This study was performed using two-dimensional digital lateral cephalogram that is a limitation. Therefore, it is important to recognize that three-dimensional evaluation of the airways by means of cone-beam computed tomography, respecting legal and ethical aspects, due a higher dose of radiation, could be useful for improved assessment in further studies to minimize this limitation.