Isolated Right-sided Patent Ductus Arteriosus in Right-sided Aortic Arch* Report of TwoCases

protruded forward. This sequence of events is in contrast to a previous report8 describing protrusion of the prevertebral soft tissue as the initial event in obstructive apnea. The patient was completely well before the head trauma six years previously. We believe, therefore, that the main underlying cause of the obstructive apnea was an abnormal sleep-induced reduction in the pharyngeal dilator muscle tone, caused by the head injury. The combination of this, together with the elongated epiglottis and the retrognathia, then facilitated the loss of airway patency during sleep. Both abnormally decreased muscular activity8 and reduced pharyngeal cross-sectional area of the pharynx have been described in patients with the obstructive sleep apnea syndrome.9 When nasal CPAP was applied, the epiglottis was virtually blown into approximation with the posterior pharyngeal wall giving the patient a feeling of suffocation. The fact that the patient could not fall asleep, as well as a pneumatic tongueretaining effect of the nasal CPAP, presumably prevented marked aggravation of the obstructive apnea. It is likely that the abnormality of the epiglottis was not noted at the initial otorhinolaryngeal examination because the patient was examined in the upright position. Most of our patients with obstructive sleep apnea are now studied by video-taped fluoroscopic examination of the pharynx during sleep. When the mechanism responsible for occlusion of the pharyngeal airway is discovered, the most appropriate treatment can be selected.