ABSTRACT
[ABSTRACT]OBJECTIVETo assess the upper airway and related structures in different patterns of the upper airway obstruction on cine magnetic resonance (CMR) imaging in patients with obstructive sleep apnea hypopnea syndrome (OSAHS).METHODSCMR images of upper airway were obtained in 30 male patients with severe OSAHS during waking state and natural sleep. The midsagittal plane images were obtained. Patients were classified into 3 groups based on the upper airway obstruction patterns at apnea events and the reference data of the upper airway were measured.RESULTSDuring natural sleep, the diameter of retropalatal region, retroglossal region, retroepiglottic region and the length of suprahyoid muscles were significantly shorter than those during waking state (P<0.01). The maximum angle between the suprahyoid muscles and the apex of the tongue during natural sleep was significantly larger than that during waking state (P<0.01). During wakefulness, there was a significantly difference in the diameter of retropalatal region among 3 obstruction patterns (P<0.01). During natural sleep, there were statistical difference in the diameter of retropalatal region and the upper tongue, the angle between the hard palate and soft palate, the maximum angle between the suprahyoid muscles and the apex of the tongue, and their change values among 3 obstruction patterns (P<0.05). CONCLUSIONThe measurements of the upper airway and related structures on CMR imaging in OSAHS patients could provide useful information in assessing upper airway.
ABSTRACT
Objective To study the effects of different pressure boundary conditions and breathing patterns on the airflow of upper airway and related physiological status of the obstructive sleep apnea hypopnea syndrome (OSAHS) patient at sleep stage with eupnea and apnea, respectively. Methods The CT scan data of an OSAHS patient during natural sleep in supine position were acquired and used to reconstruct a three-dimensional finite element model of upper airway. Meanwhile the pressure changes in laryngeal cavity of the OSAHS patient were clinically measured and then used as the boundary conditions, and four typical breathing patterns (nasal inhaling and nasal exhaling, nasal inhaling and oral exhaling, oral inhaling and nasal exhaling, oral inhaling and oral exhaling) were considered for computational fluid simulation. Results The airflow of the OSAHS patient during sleep was an unstable, whorled and bidirectional flow, which was significantly affected by pressure boundary conditions and breathing patterns. Compared with nasal breathing, the maximum velocity of airflow by mouth breathing was increased, resulting in an increase of pressure drop in oral cavity, with was about 30% in inspiration and 100% in expiration. Conclusions It is significant to use CT data of an OSAHS patient during natural sleep for model reconstruction and the clinically measured pressure in laryngeal cavity as boundary conditions for finite element simulations, and the results will contribute to understand the characteristics of flow field in upper airway of the OSAHS patient during real natural sleep.