Does rapid maxillary expansion improve nasal airway obstruction? A computer fluid dynamics study in patients with nasal mucosa hypertrophy and obstructive adenoids.

INTRODUCTION: Rapid maxillary expansion (RME) expands the maxillary dentition laterally and improves nasal airway obstruction. However, the incidence of nasal airway obstruction improvement after RME is approximately 60%. This study aimed to clarify the beneficial effects of RME on nasal airway obstruction in specific pathologic nasal airway diseases (nasal mucosa hypertrophy and obstructive adenoids) using computer fluid dynamics. METHODS: Sixty subjects (21 boys; mean age 9.1 years) were divided into 3 groups according to their nasal airway condition (control, nasal mucosa hypertrophy, and obstructive adenoids), and those requiring RME had cone-beam computed tomography images taken before and after RME. These data were used to evaluate the nasal airway ventilation condition (pressure) using computer fluid dynamics and measure the cross-sectional area of the nasal airway. RESULTS: The cross-sectional area of the nasal airway significantly increased after RME in all 3 groups. The pressures in the control and nasal mucosa groups significantly reduced after RME but did not change significantly in the adenoid group. The incidence of improvement in nasal airway obstruction in the control, nasal mucosa, and adenoid groups was 90.0%, 31.6%, and 23.1%, respectively. CONCLUSIONS: The incidence of improvement in nasal airway obstruction after RME depends on the nasal airway condition (nasal mucosa hypertrophy and obstructive adenoids). In patients with nonpathologic nasal airway conditions, the obstruction may be sufficiently improved with RME. Furthermore, to some extent, RME may be effective in treating nasal mucosa hypertrophy. However, because of obstructive adenoids, RME was ineffective in patients with nasal airway obstruction.

Relationship between pharyngeal airway depth and ventilation condition in mandibular setback surgery: A computational fluid dynamics study.

OBJECTIVES: This study aimed to determine the anteroposterior depth (APD) of the pharyngeal airway (PA) where post-operative PA obstruction was predicted, using computer fluid dynamics (CFD), in order to prevent obstructive sleep apnoea after mandibular setback surgery. SETTINGS AND SAMPLE POPULATION: Nineteen skeletal Class III patients (8 men; mean age, 26.7 years) who required mandibular setback surgery had computed tomography images taken before and 6 months after surgery. METHODS: The APD of each site of the four cross-sectional reference planes (retropalatal airway [RA], second cervical vertebral airway, oropharyngeal airway and third cervical vertebral airway) were measured. The Maximum negative pressure (Pmax) of the PA was measured at inspiration using CFD, based on a three-dimensional PA model. Intersite differences were determined using analysis of variance and the Friedman test with Bonferroni correction. The relationship between APD and Pmax was evaluated by Spearman correlation coefficients and non-linear regression analysis. RESULTS: The smallest PA site was the RA. Pmax was significantly correlated with the APD of the RA (rs  = .628, P < .001). The relationship between Pmax and the APD-RA was fitted to a curve, which showed an inversely proportional relationship of Pmax to the square of the APD-RA. Pmax substantially increased even with a slight reduction of the APD-RA. In particular, when the APD-RA was 7 mm or less, Pmax increased greatly, suggesting that PA obstruction was more likely to occur. CONCLUSIONS: The results of this study suggest that APD-RA is a useful predictor of good PA ventilation after surgery.

Rapid maxillary expansion effects of nasal airway in children with cleft lip and palate using computational fluid dynamics.

OBJECTIVES: Rapid maxillary expansion (RME) improves nasal airway ventilation in non-cleft palate children. Children with unilateral cleft lip and palate (UCLP) may have nasal obstruction and experience an increased risk of obstructive sleep apnoea. The effect of RME in UCLP children is unclear. This retrospective study evaluated RME-induced changes in ventilation parameters in children with UCLP using computational fluid dynamics. SETTING AND SAMPLE POPULATION: Nineteen patients (10 boys, mean age 10.7 years) who required RME had cone-beam computed tomography images taken before and after RME. Twenty control participants (11 boys, mean age 11.1 years) received regular orthodontic treatment. METHODS: Nasal airway ventilation parameters (air pressure, air velocity and airflow rate) were analysed via computational fluid dynamics, and nasal cross-sectional area (CSA) was measured. RESULTS: Maximum pressure, velocity and nasal resistance were significantly reduced by RME in the UCLP group. Air flow rate and CSA on the cleft side significantly were increased by RME in the UCLP group. CONCLUSIONS: In children with UCLP, increasing the quantity of airflow and CSA on the cleft side by RME substantially improved nasal ventilation.