3D Airway in Clefts Figure 4. Comparisons of airway length in CLP vs. non-CLP, CLP boys vs. non-CLP boys and CLP girls vs. non-CLP girls. doi:10.1371/journal.pone.0043405.g004 CLP group. The average ratio of cross-sectional area to volume was 0.0064 for the CLP group and 0.0076 for the non-CLP group. A one-tailed T test determined that there were no significant differences in the smallest cross-sectional area to volume ratio. Discussion The goal of the study was to develop a reliable 3-D analysis to measure certain characteristics of the pharyngeal airway in children with CLP and compare the findings to a non-CLP control group, matched for age and sex. To the best of our knowledge, this is the first 3-D study to measure airway volume and smallest cross sectional area in children with CLP. Previous CBCT studies have assessed pharyngeal airway volume in healthy children with retrognathic mandible versus normal growth pattern, the oropharyngeal airway in children with class III malocclusion, and age related changes in the airway in children versus adults [28,29,30]. In our study, we hypothesized that children with CLP had smaller pharyngeal airways compared to non-CLP control group. Our data demonstrated that there was no significant difference in pharyngeal airway volume and smallest cross sectional area but that the airway length was significantly longer in CLP children when compared to non-CLP children. Kim et al [30] measured the total airway volume for children (age range = 10.50–12.92 years) to be 20.96 cm3 with a standard deviation of 3.6 cm3. In our study, the mean airway volume was 18.1 cm3 (SD = 7.0 cm3) and 15.1 cm3 (SD = 5.8 cm3) for the cleft palate and non-cleft palate groups, respectively. The mean smallest cross-sectional area for CLP individuals was 115.7 mm2 (SD = 58.4 mm2) and for controls 113.8 mm2 2 (SD = 59.2 mm ). The large standard deviations signify a wide Table 1. Airway length measurements in CLP vs. controls. Average airway length (mm) S.D. p- value CLP Controls CLP boys Control boys CLP girls Control girls 60.6 52.6 62.4 52.9 57.6 50.8 Average airway length in various groups. doi:10.1371/journal.pone.0043405.t001 8.6 4.5 8.1 4.1 9.1 5.3 0.004 0.01 0.20 Figure 5. Graph depicting strong positive correlation between volume and smallest cross-sectional area in non-CLP. doi:10.1371/journal.pone.0043405.g005 range of values for cross-sectional area. This may be attributed to the age range of patients and the varying levels of growth for each patient. Abramson et al [28] found that the average smallest cross- sectional area in children age 6–11 was 82.9 mm2 (SD = 16.5 mm2) and for adolescents 12–16 was 122.2 mm2 2 (SD = 39.3 mm ). They did not find any significant differences in airway volume or minimum cross-sectional area between boys and girls. They also found that there was a significantly longer airway length in the study group compared to the control group but there was no difference in airway length between boys and girls. Ronen et al [31] found a differential growth in airway length in boys and girls during puberty resulting in significantly longer airway in boys (ages 14–19). In our study, there was a significantly longer airway in the CLP group compared to non-CLP group and in CLP boys compared to non-CLP boys. There were no significant differences in airway length between boys and girls in the age group studied. PLOS ONE | www.plosone.org 4 August 2012 | Volume 7 | Issue 8 | e43405