Published ahead of print on March 4, 2005, doi:10.1164/rccm.200411-1597OC Am. J. Respir. Crit. Care Med., Volume 171, Number 11, June 2005, 1298-1304 A more recent version of this article appeared on June 1, 2005
Submitted on November 29, 2004 Changes in Upper Airway Size During Tidal Breathing in Children With Obstructive Sleep ApneaRaanan Arens1*,1 Division of Pulmonary Medicine, Children's Hospital of Philadelphia, Philadelphia, PA, USA; Division of Sleep Medicine, Hospital of the University of Pennsylvania, University of Pennsylvania School of Medicine, Philadelphia, PA, USA, 2 Division of Pulmonary Medicine, Children's Hospital of Philadelphia, Philadelphia, PA, USA, 3 Division of Critical Care, Children's Hospital of Philadelphia, Philadelphia, PA, USA, 4 Research Collaboration, Siemens Medical Solutions, USA, Inc., Malvern, PA, USA, 5 Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA, USA, 6 Division of Sleep Medicine, Hospital of the University of Pennsylvania, University of Pennsylvania School of Medicine, Philadelphia, PA, USA * To whom correspondence should be addressed. E-mail: arens{at}email.chop.edu.
We performed respiratory-gated MRI to evaluate airway dynamics during tidal breathing in 10 children with obstructive sleep apnea syndrome (OSAS, 4.3±2.3 years) and 10 matched controls (5.0±2.0 years). We hypothesized that respiratory cycle fluctuations in upper airway cross-sectional area will be larger in OSAS children. Methods: Studies were performed under sedation. Respiratory gating was performed automatically at 10, 30, 50, 70, and 90% of inspiratory and expiratory volume. Airway cross-sectional area was measured at 4 ascending oropharyngeal levels at each increment of the respiratory cycle. Results: We noted the following in OSAS subjects compared to controls: 1) A smaller upper airway cross-sectional area particularly during inspiration; 2) Airway narrowing occurred during inspiration without evidence of complete airway collapse 3) Airway dilatation occurred during expiration, particularly early in the phase; and 4) Magnitude of cross-sectional areas fluctuations during tidal breathing noted in OSAS at levels 1-4 were: 317%, 422%, 785% and 922% compared to 19%, 15% 17% and 24%, in controls (p<0.001, p<0.005, p<0.001, and p<0.001, respectively). Conclusions: Fluctuations in airway area during tidal breathing are significantly greater in OSAS subjects compared to controls. Resistive pressure loading is a probable explanation, although increased airway compliance may be a contributing factor. Key Words: Magnetic resonance imaging (MRI), Respiratory gated MRI, Upper airway. Key words: Magnetic resonance imaging (MRI), Respiratory gated MRI, Upper airway
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