Computational fluid dynamics endpoints for assessment of adenotonsillectomy outcome in obese children with obstructive sleep apnea syndrome.
BACKGROUND
Improvements in obstructive sleep apnea syndrome (OSAS) severity may be associated with improved pharyngeal fluid mechanics following adenotonsillectomy (AT). The study objective is to use image-based computational fluid dynamics (CFD) to model changes in pharyngeal pressures after AT, in obese children with OSAS and adenotonsillar hypertrophy.


METHODS
Three-dimensional models of the upper airway from nares to trachea, before and after AT, were derived from magnetic resonance images obtained during wakefulness, in a cohort of 10 obese children with OSAS. Velocity, pressure, and turbulence fields during peak tidal inspiratory flow were computed using commercial software. CFD endpoints were correlated with polysomnography endpoints before and after AT using Spearman׳s rank correlation (rs).


RESULTS
Apnea hypopnea index (AHI) decreases after AT was strongly correlated with reduction in maximum pressure drop (dPTAmax) in the region where tonsils and adenoid constrict the pharynx (rs=0.78, P=0.011), and with decrease of the ratio of dPTAmax to flow rate (rs=0.82, P=0.006). Correlations of AHI decrease to anatomy, negative pressure in the overlap region (including nasal flow resistance), or pressure drop through the entire pharynx, were not significant. In a subgroup of subjects with more than 10% improvement in AHI, correlations between flow variables and AHI decrease were stronger than in all subjects.


CONCLUSIONS
The correlation between change in dPTAmax and improved AHI suggests that dPTAmax may be a useful index for internal airway loading due to anatomical narrowing, and may be better correlated with AHI than direct airway anatomic measurements.
Department of Mechanical Engineering, The Cooper Union for the Advancement of Science and Art, 41 Cooper Square, New York, NY, USA.
Haiyan
H
Luo
Division of Respiratory and Sleep Medicine, Albert Einstein College of Medicine, The Children׳s Hospital at Montefiore, Bronx, NY, USA.
Sanghun
S
Sin
Division of Pulmonary Medicine, The Children׳s Hospital of Philadelphia, Philadelphia, PA, USA.
Joseph M
JM
McDonough
Department of Epidemiology & Population Health, Albert Einstein College of Medicine, Bronx, NY, USA.
Carmen R
CR
Isasi
Division of Respiratory and Sleep Medicine, Albert Einstein College of Medicine, The Children׳s Hospital at Montefiore, Bronx, NY, USA.
Raanan
R
Arens
Department of Mechanical Engineering, The Cooper Union for the Advancement of Science and Art, 41 Cooper Square, New York, NY, USA. Electronic address: wootto@cooper.edu.
David M
DM
Wootton
D000233:Adenoidectomy; D000293:Adolescent; D000311:Adrenal Glands / Q000601:surgery*; D002648:Child; D015331:Cohort Studies; D003198:Computer Simulation; D005260:Female; D006801:Humans; D057446:Hydrodynamics; D006984:Hypertrophy; D007091:Image Processing, Computer-Assisted; D007320:Inspiratory Capacity; D008297:Male; D009296:Nasal Cavity / Q000473:pathology; D014066:Palatine Tonsil / Q000601:surgery*; D063766:Pediatric Obesity / Q000150:complications / Q000503:physiopathology*; D010614:Pharynx / Q000503:physiopathology; D010641:Phenotype; D017286:Polysomnography; D011312:Pressure; D012137:Respiratory System / Q000503:physiopathology; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000503:physiopathology*; D012984:Software; D013990:Tidal Volume; D014068:Tonsillectomy; D016896:Treatment Outcome
Airway resistance; Computer simulation; Humans; Magnetic resonance imaging; Pediatrics