Patients with obstructive sleep apnea (OSA) experience severe sleep disruption and consequent daytime sleepiness. Current arousal scoring criteria show that some obstructive apneic events do not end in a recognizable cortical electroencephalographic (EEG) arousal. It is not known whether events that end in an obvious EEG arousal differ from those that do not, in terms of EEG frequency changes during the apneic event, the respiratory effort developed prior to apnea termination, the degree of the postapneic increase in blood pressure, or changes in CO2 tensions. We studied 15 patients with OSA in early Stage 2 sleep and analyzed obstructive apneic events with and without typical EEG arousals, defining an arousal as a frequency shift to waking alpha rhythm of 1 s or longer. EEG signals were digitized and analyzed by fast Fourier transform during and immediately after each apnea. The median EEG frequency and mean pleural pressure of the first and second halves of the apneic episode were compared with that of the first breath. Peak pleural pressure was measured just before the end of the apneic episode. Systolic and diastolic blood pressures and CO2 tensions were measured at the onset and termination of apnea. For each patient, 10 events that ended in EEG arousal were compared with 10 events that did not. Mean apnea duration did not differ for the two groups of events. Median EEG frequency and pleural pressure increased significantly from 8.14 to 9.25 Hz and 15.4 to 22.1 cm H2O, respectively, as the apnea progressed, but there was no difference between the groups nor any difference in the peak pleural pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

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A case of obstructive sleep apnoea associated with the Arnold-Chiari malformation is described, in which the loss of pharyngeal sensation seems to have played an important part in the aetiology of the obstruction of the upper airway. (Thorax 1995;50:690-691) Keywords: obstructive sleep apnoea, Arnold-Chiari malformation, airways obstruction.Obstructive sleep apnoea usually arises when anatomical factors narrow the upper airway or lead to an increase in negative intraluminal pressure. However, most reports of sleep disorders in patients with neuromuscular disease have found central sleep apnoea'2; obstructive episodes have been reported in some34 but not all5 cases where sleep apnoea coexists with an Arnold-Chiari malformation.Arnold-Chiari malformation is a disorder in which the cerebellar tonsils herniate through the foramen magnum producing variable signs and symptoms of cerebellar, cervical, and/or brainstem dysfunction. Surgical correction of this problem has been reported to produce a dramatic improvement in the symptoms of the associated sleep apnoea, but follow up has been relatively brief.3 We report a case of obstructive sleep apnoea associated with Arnold-Chiari malformation where mechanisms other than upper airway narrowing appeared to operate, and where a longer follow up has led us to revise our initially optimistic view of surgical treatment.Case report A 62 year old man presented with two "black outs", one following a coughing bout. He admitted to hypersomnolence and was a loud snorer. His wife had witnessed apnoeas during sleep, together with attacks of coughing and choking. He was mildly overweight with a collar size of 16 inches (40 cm) and body mass index of 27-4, but no neurological abnormality was detected at presentation. A provisional diagnosis of cough syncope together with obstructive sleep apnoea was made and polysomnography was performed. This showed repeated obstructive apnoeic episodes (table) irrespective of body position associated with considerable difficulty in swallowing saliva during his sleep. Nasal continuous positive airway pressure was tried but was not tolerated.At follow up three months after presentation he reported progressive difficulty in walking. On examination he had a positive Romberg's sign and dysarthria. Over the next few weeks he developed diplopia and, subsequently, difficulty in swallowing. At this point his gag reflex was noted to be absent, whilst horizontal and vertical nystagmus together with features of cerebellar ataxia were present.Myelography and magnetic resonance imaging (MRI) of his head and cervical spine revealed an Arnold-Chiari malformation with the cerebellar tonsils prolapsed to C2. There was kinking of the medulla by the inferior tip of the clivus, but no hydrocephalus or syrinx were demonstrated.He underwent a preliminary tracheostomy followed by a decompressive laminectomy to C2 and debulking of both cerebellar tonsils. Postoperatively his swallowing was good and pulse oximetery with an open tracheostomy revealed no oxygen desat...

Fibreoptic bronchoscopy (FOB) is now commonly performed, and the number of elderly patients undergoing the procedure is increasing. Problems with oxygenation during FOB are well-recognised, but there are few data about its cardiovascular effects. Forty five patients (median age 65 yrs) undergoing elective FOB were studied prospectively. Patients were connected to a 12-lead computerized electrocardiographic recorder, a finger plethysmographic blood pressure (FPBP) monitor and pulse oximeter. Forty three patients were sedated with fentanyl and droperidol, and all were given 5 mL 2.5% cocaine intratracheally and xylocaine spray to the pharynx. Mean sphygmomanometric cuff blood pressure was raised initially (167/88 mmHg). Mean blood pressure recorded by FPBP rose on intratracheal injection (178/96 mmHg) and remained high throughout the procedure. Mean (SD) initial cardiac frequency was 93 (5.1) beats x min(-1) and rose to 134 (7.5) beats x min(-1) during the procedure. Four of the 45 patients showed unexpected ST segment depression of >1 mm for >1 min, and a further three developed bundle branch block. These seven patients had significantly greater tachycardia (152 vs 131 beats x min(-1)) and higher blood pressure (238/131 vs 207/109 mmHg). They were older (72 vs 61 yrs), had smoked more (63 vs 39 pack-years), but had similar lung function and similar changes in oxygen saturation. Oxygen desaturation occurred in 19 patients and this was associated with poor lung function (69 vs 84% predicted forced expiratory volume in one second), but was independent of the cardiovascular changes. Significant cardiovascular changes occur during fibreoptic bronchoscopy, with evidence of cardiac strain in 21% of patients over the age of 60 yrs.