Showing papers on "Polysomnography published in 1990"
TL;DR: The results support the notion that ambulatory EEG/EOG changes may be used to quantify sleepiness and suggest physiological changes due to sleepiness are not likely to occur until extreme sleepiness is encountered.
Abstract: Eight subjects were kept awake and active overnight in a sleep lab isolated from environmental time cues. Ambulatory EEG and EOG were continuously recorded and sleepiness ratings carried out every two hours as was a short EEG test session with eyes open for 5 min and closed for 2 min. The EEG was subjected to spectral analysis and the EOG was visually scored for slow rolling eye movements (SEM). Intrusions of SEM and of alpha and theta power density during waking, open-eyed activity strongly differentiated between high and low subjective sleepiness (the differentiation was poorer for closed eyes) and the mean intraindividual correlations between subjective and objective sleepiness were very high. Still, the covariation was curvilinear; physiological indices of sleepiness did not occur reliably until subjective perceptions fell between "sleepy" and "extremely sleepy-fighting sleep"; i.e. physiological changes due to sleepiness are not likely to occur until extreme sleepiness is encountered. The results support the notion that ambulatory EEG/EOG changes may be used to quantify sleepiness.
2,568 citations
TL;DR: To examine the hypothesis that sleep apnoea is a risk factor for ischaemic heart disease, overnight polysomnography was performed in 101 unselected male survivors of acute myocardial infarction aged less than 66 yr and in 53 male subjects of similar age without evidence of ischaemia heart disease.
946 citations
01 Aug 1990
TL;DR: The choice of therapy should be tailored to the individual patient with sleep apnea, and careful follow-up is essential to ensure a positive response to therapy.
Abstract: Obstructive sleep apnea syndrome is the most common cause of hypersomnolence in patients referred to sleep disorders centers. This type of sleep apnea is characterized by loud snoring, nocturnal oxyhemoglobin desaturation, and disrupted sleep that leads to daytime hypersomnolence. The anatomic configuration of the pharynx and the physiologic responses to occlusion of the upper airway play a major role in the pathogenesis of this disorder. Polysomnography can accurately identify obstructive sleep apnea, and the multiple sleep latency test allows an objective measurement of daytime alertness. Weight loss and training the patient to sleep in a lateral position are frequently used to alleviate mild cases. Nasally applied continuous positive airway pressure is an extremely effective modality for treating moderate and severe obstructive sleep apnea. Surgical correction of obvious anatomic defects has a role in diminishing obstructive sleep apnea, but the exact role of surgical intervention in patients without obvious anatomic defects remains unknown. The choice of therapy should be tailored to the individual patient with sleep apnea, and careful follow-up is essential to ensure a positive response to therapy.
334 citations
TL;DR: It is suggested that the change in pharyngeal cross sectional shape, secondary to a reduction in phayageal transverse diameter, may be related to the risk of developing sleep related disordered breathing.
Abstract: To characterise the relation between pharyngeal anatomy and sleep related disordered breathing, 17 men with complaints of snoring were studied by all night polysomnography. Ten of them had obstructive sleep apnoea (mean (SD) apnoea-hypopnoea index 56.3 (41.7), age 52 (10) years, body mass index 31.4 (5.3) kg/m2); whereas seven were simple snorers (apnoea-hypopnoea index 6.7 (4.6), age 40 (17) years, body mass index 25.9 (4.3) kg/m2). The pharynx was studied by magnetic resonance imaging in all patients and in a group of eight healthy subjects (age 27 (6) years, body mass index 21.8 (2.2) kg/m2, both significantly lower than in the patients; p less than 0.05). On the midsagittal section and six transverse sections equally spaced between the nasopharynx and the hypopharynx several anatomical measurements were performed. Results showed that there was no difference between groups in most magnetic resonance imaging measurements, but that on transverse sections the pharyngeal cross section had an elliptic shape with the long axis oriented in the coronal plane in normal subjects, whereas in apnoeic and snoring patients the pharynx was circular or had an elliptic shape but with the long axis oriented in the sagittal plane. It is suggested that the change in pharyngeal cross sectional shape, secondary to a reduction in pharyngeal transverse diameter, may be related to the risk of developing sleep related disordered breathing.
243 citations
TL;DR: The effect of sleep position was evaluated in 10 patients and found to have little affect on the extent over which the UA collapsed during sleep independent of sleep state, and the effects of UPPP on regional UA collapse were evaluated in a small group of six patients.
Abstract: The present study was conducted to determine the effects of body position and sleep state, as well as the effect of uvulopalatopharyngoplasty (UPPP) on the regions over which the upper airway (UA) collapses during sleep. To accomplish this goal, 18 male patients with obstructive sleep apnea (OSA) underwent overnight polysomnography with simultaneous monitoring of pressures in the posterior nasopharynx, oropharynx, hypopharynx, and esophagus. From the profile of pressures recorded in the UA and esophagus, the regions over which the UA collapses during apneas could be determined. The patients were 54 ± 14 y of age and were grossly obese with a body mass index of 37 ± 2 kg/m2. They had moderately severe OSA with a mean apnea plus hypopnea index of 62 ± 8 per hour. During NREM sleep, 10 of the 18 (56%) patients had collapse confined to the velopharyngeal or retropalatal segment of the upper airway. The remaining 44% of the patients demonstrated collapse of the retroglossal segment of the oropharynx located ca...
198 citations
TL;DR: The present indications for MMO are severe OSAS, morbid obesity, and severe mandibular deficiency.
186 citations
TL;DR: In this article, a simplified sleep apnea investigation consisting of combined oximetry and respiration movement monitoring was compared with conventional polysomnography, and two types of recordings were performed simultaneously during one night in 77 patients with suspected obstructive sleep apna syndrome (OSAS).
156 citations
TL;DR: There was no statistical difference between nasal CPAP and surgery for all respiratory variables and an analysis of variance was used to examine the results, and the goal was to determine if the surgical protocol was as effective as nasalCPAP.
145 citations
TL;DR: It is conjectured that GHB, an endogenous neurochemical, may be a sleep neurotransmitter or neuromodulator, since GHB rapidly induces sleep, and increases sleep continuity and delta sleep without suppressing REM sleep in both normals and narcolepsy patients.
Abstract: The effects of gamma-hydroxybutyrate (GHB: 25 mg/kg h.s. and 3 h later) vs. placebo on objectively evaluated nighttime sleep and daytime sleepiness in narcolepsy were evaluated in a double-blind, counterbalanced crossover design. Twenty narcolepsy patients were given an overnight polysomnogram (PSG), followed by a daytime multiple sleep latency test (MSLT) at baseline and on the 1st and 29th days of GHB and placebo treatment. The overnight PSGs indicated that the narcolepsy patients had the following significant results during GHB versus placebo treatment: decreased stage 1 (p = 0.012), increased stage 3 (p = 0.008), increased delta (stage 3 and 4 combined) sleep (p = 0.049), fewer stage shifts (p = 0.002), and fewer awakenings (p = 0.006). Minutes of wakefulness were significantly increased only for the last 2 h of the 8 h sleep period on GHB versus placebo (p = 0.019), which is beyond the time of GHB's direct influence. The MSLTs indicated that the narcolepsy patients had a marginally increased sleep latency mean during GHB versus placebo treatment (p = 0.074) and significantly increased total stage 0 (wakefulness) on day 29 of GHB versus day 29 of placebo treatment (p = 0.038). Female narcolepsy patients had significantly fewer naps with REM sleep (REM naps) on day 29 of GHB vs. day 29 of placebo treatment (p = 0.020). The therapeutic effect of GHB in narcolepsy patients, i.e., decreases cataplexy, appears to be due to its improving nocturnal sleep quality, since its half-life is only 1.5 to 2 h. It is conjectured that GHB, an endogenous neurochemical, may be a sleep neurotransmitter or neuromodulator, since GHB rapidly induces sleep, and increases sleep continuity and delta sleep without suppressing REM sleep in both normals and narcolepsy patients.
134 citations
TL;DR: Maxillofacial surgery has proven to be an effective method for controlling OSA syndrome, and its results are as effective as those obtained with nasal CPAP.
133 citations
TL;DR: It is concluded that there can be variable expressivity of the clinical features in familial restless legs syndrome and that there are probably some relatively nonrestless patients with prominent periodic movements in sleep who are carriers of the restless legs Syndrome gene.
Abstract: A 62-year-old man with a 20-year history of excessive daytime somnolence and kicking during sleep was an obligate carrier of the restless legs syndrome gene because his paternal grandfather, father, and all three of his children had symptoms of restless legs syndrome. The patient himself, however, denied motor restlessness after a careful and exhaustive medical history and he was originally believed to have periodic movements in sleep without restless legs. Close clinical observation did reveal nighttime motor restlessness, although the patient continued to deny its importance. Polysomnography showed frequent periodic movements in sleep. We conclude that there can be variable expressivity of the clinical features in familial restless legs syndrome and that there are probably some relatively nonrestless patients with prominent periodic movements in sleep who are carriers of the restless legs syndrome gene. Some sleep-disordered patients who are believed to have only periodic movements in sleep may have a forme fruste of autosomal dominant restless legs syndrome. If one does not examine these patients carefully at night and take an adequate family history, one may miss the diagnosis of restless legs syndrome.
TL;DR: It is demonstrated that the polygraphically identified SA and PLMs which are widespread in seniors tend not to be manifested in self-reported sleep-wake or mood disturbance, and the need for validated morbidity cut-offs for SA andPLMs is illustrated.
Abstract: Despite its widespread use, the validity of the 5/h morbidity cut-off for the Respiratory Disturbance Index (RDI) or the Movement Index (MI) in determining presence of sleep apnea (SA) or sleep-related periodic leg movements (PLMs), respectively, has not been determined for any aged population. One hundred community resident seniors 60 years of age or older underwent three consecutive nights of polysomnography and also completed conventional measures of subjective sleep-wake complaints (written sleep questionnaire, sleep log, sleep interview) and mood disturbances (Zung Self-Rating Depression and Anxiety Scales, Profile of Mood States, Beck Depression Inventory). Based on the 5/h cut-off, 34% had SA and 58% had PLMs. Despite this, the frequency of subjective sleep-wake and mood disturbance was low across methods of assessment. Groups formed by the 5/h cut-off for RDI or MI failed to differ significantly in responses on all subjective sleep-wake and mood measures. Higher cut-offs also were examined and proved weak or ineffective in predicting subjective sleep-wake and mood disturbance. Preliminary investigations suggested that alternative measures of severity of SA (means oxygen desaturation and means duration of apneas or hypopneas) may be better predictors of subjective disturbance than RDI in this population. These findings both (a) demonstrate that the polygraphically identified SA and PLMs which are widespread in seniors tend not to be manifested in self-reported sleep-wake or mood disturbance, and (b) illustrate the need for validated morbidity cut-offs for SA and PLMs.
TL;DR: Sleep studies should be performed on post-polio patients with excessive daytime sleepiness and respiratory complaints, including individuals already on respiratory assistance such as rocking beds who have features of respiratory failure who can be treated effectively with long-term nasal mechanical ventilation.
TL;DR: The sleep in young adults with severe isolated growth hormone deficiency (IGHD) was examined by polysomnography and there was a significant decrease in delta sleep time, but the total sleep time was significantly increased compared to age- and sex-matched normal subjects.
Abstract: The sleep in young adults with severe isolated growth hormone deficiency (IGHD) was examined by polysomnography. There was a significant decrease in delta sleep time (= stages 3 + 4, slow wave sleep,
TL;DR: Polysomnography showed paroxysmal short-lasting arousals during NREM, especially slow-wave sleep, associated with complex movements and autonomie activation, which represent a sleep disturbance that may be related to deep epileptic foci.
Abstract: Six patients complained of distressing sudden awakenings with abnormal motor activity during sleep causing insomnia. Polysomnography showed paroxysmal short-lasting arousals during NREM, especially slow-wave sleep, associated with complex movements and autonomie activation. Ictal and interictal EEG never showed epileptic discharges except in 1 patient who also had a tonic-clonic seizure during sleep. Carbamazepine was the only effective medication in 2 patients. Paroxysmal arousals represent a sleep disturbance that may be related to deep epileptic foci.
Journal Article•
TL;DR: The occurrence of respiratory events was not related to the degree of the decrease in minute ventilation from wakefulness to apnea-free sleep, and the higher the minute ventilation during wakefulness, the greater the decrease during sleep.
Abstract: Although ventilation during sleep has been studied in normal young and elderly subjects, little data are available concerning possible quantitative changes in ventilatory parameters in normal middle-aged subjects. We studied the occurrence of respiratory events and the changes in minute ventilation, tidal volume, and respiratory rate during rapid-eye-movement (REM) and non-REM (NREM) sleep in 40 normal (20 men and 20 women) middle-aged subjects, using polysomnography with pneumotachography and oximetry. Apnea indices greater than 5, with apneas predominantly of the obstructive type, were found in 17.5% of the subjects (30% of the men and 5% of the women). These "apneic" subjects differed from the "nonapneic" subjects only in that they had a higher body mass index. Minute ventilation decreased from wakefulness to sleep by 14% to 19%, owing to a decrease in tidal volume without a significant change in respiratory rate. This decrease was not greater in slow wave (stage 3-4 NREM) or in REM sleep than in stage 2 NREM sleep, nor was it greater in men than in women. It correlated with the minute ventilation during wakefulness: the higher the minute ventilation during wakefulness, the greater the decrease during sleep. The occurrence of respiratory events was not related to the degree of the decrease in minute ventilation from wakefulness to apnea-free sleep.
TL;DR: The physiological and psychological features identified in these patients, possibly reflecting different expressions of a constitutional cerebral characteristic, may be explored in terms of hysterical dissociation.
Abstract: OBJECTIVE--To determine some personality and psychoneurotic characteristics of adults who have the sleepwalking-night terrors syndrome. DESIGN--Prospective assessment of two groups of consecutive patients with a firm diagnosis of either of two specific sleep disorders as established clinically and by polysomnography. SETTING--Outpatient sleep disorders clinic and sleep laboratory in a tertiary referral centre. PATIENTS--12 Patients referred consecutively to the clinic in whom a diagnosis of sleepwalking (six) or night terrors (six) was confirmed. MAIN OUTCOME MEASURES--Psychological characteristics as measured at the time of clinical assessment by means of the Eysenck personality questionnaire, the hostility and direction of hostility questionnaire, and the Crown-Crisp experiential index. RESULTS--Both groups scored exceptionally highly on the hysteria scale of the Crown-Crisp experiential index and the night terrors group also scored highly on the anxiety scale. The patients with sleepwalking also scored highly on a measure of externally directed hostility. CONCLUSIONS--The physiological and psychological features identified in these patients, possibly reflecting different expressions of a constitutional cerebral characteristic, may be explored in terms of hysterical dissociation. The findings contribute to the debate concerning the nature of sleepwalking, in particular with and without the forensic aspects.
Journal Article•
TL;DR: In a cohort unselected for symptoms, the ability of self-administered questionnaires to predict SDB was low; short studies were only moderately sensitive for detecting an AHI greater than or equal to 10, and the AHI was not a major determinant of nocturnal desaturation.
Abstract: We evaluated self-administered questionnaires and short sleep studies in screening for sleep-disordered breathing (SDB) in 40 hypertensive men ages 36-66 unselected for symptoms. Each subject completed a questionnaire including questions on sleep-related symptoms and underwent overnight polysomnography in which we evaluated the apnea-hypopnea index (AHI) and the percentage of time during which arterial O2 saturation was less than 90% (T90). The first 90 min of overnight study was evaluated separately, and 10 subjects with an AHI greater than or equal to 10 also underwent late afternoon nap study. By overnight polysomnography, 48% of the cohort had an AHI greater than or equal to 10, and 35% had a T90 greater than or equal to 10%. Using linear regression, we found no features of the symptom questionnaire that strongly predicted AHI. Only self-reported snoring and baseline arterial Po2 significantly predicted T90. The AHI and T90 were not significantly correlated. Considering an AHI greater than or equal to 10 in the overnight study as "abnormal" and an AHI greater than or equal to 10 on the short study as a "positive" test, the specificity of the AHI in the first 90 min was 100% (21/21), and the sensitivity was 42% (8/19). The sensitivity of the nap study was 60% (6/10). We conclude that in a cohort unselected for symptoms, the ability of self-administered questionnaires to predict SDB was low; short studies were only moderately sensitive for detecting an AHI greater than or equal to 10, and the AHI was not a major determinant of nocturnal desaturation.
TL;DR: It is suggested that GH has an effect on sleep, and sleep recordings may be one way of directly monitoring the effect of GH on the central nervous system.
Abstract: SUMMARY
Eight patients with isolated growth hormone deficiency(IGHD), 20–30 years old were studied with polysomnography before and after 6 months of treatment with growth hormone (GH). During GH treatment total sleep time decreased and REM sleep time increased significantly. Delta sleep time (stage 3 + 4) did not change significantly. All patients reported improved well-being and none wished to discontinue the treatment with growth hormone. These findings suggest that GH has an effect on sleep. The effect of increased REM sleep in humans is incompletely understood, but sleep recordings may be one way of directly monitoring the effect of GH on the central nervous system.
TL;DR: It was concluded that the neuropsychological deficit in mytonic dystrophy cannot be attributed to a secondary effect of nocturnal sleep apnea or sleep disruption but probably represents a direct effect of CNS lesions.
Abstract: Eight patients with myotonic dystrophy underwent comprehensive neuropsychological testing and overnight polysomnography to assess whether the waking cognitive impairment might be attributable to sleep structure abnormalities or to sleep-related respiratory problems. Patients showed substantial neuropsychological deficits, fragmented nocturnal sleep and, in half the patients, sleep apnea and/or hypopnea both mainly of central type. There was no statistically significant correlation between the degree of daytime cognitive deficit and the degree of sleep fragmentation or of respiratory problems at night. It was concluded that the neuropsychological deficit in mytonic dystrophy cannot be attributed to a secondary effect of nocturnal sleep apnea or sleep disruption but probably represents a direct effect of CNS lesions.
TL;DR: It is concluded that HT in SAS patients is not directly related to morphologic characteristics, sleep disturbances and breathing abnormalities, and apnea-hypopnea index is not significant.
TL;DR: It is speculated that the dissociation index is a quantitative reliable sleep parameter which reflects brain-stem maturation, which was highest in infants aged 36-38 conceptional weeks.
TL;DR: The nocturnal sleep, performance, and personality of healthy, asymptomatic, normal young men, 18 who had unusually short sleep latencies on the Multiple Sleep Latency Test and 20 with unusually long latencies were compared.
Abstract: The nocturnal sleep, performance, and personality of healthy, asymptomatic, normal young men, 18 who had unusually short sleep latencies on the Multiple Sleep Latency Test (average latency, less than or equal to 6 min) and 20 with unusually long latencies (average latency, greater than or equal to 16 min) were compared. On the nocturnal sleep recording, sleepy subjects had a shorter sleep latency, less waking time, and overall greater sleep efficiency than alert subjects. During the day, sleepy subjects performed more poorly than alert subjects on divided attention and vigilance performance tasks. The sleepy and alert subjects did not differ appreciably on the Minnesota Multiphasic Personality Inventory and Jenkins Activity measures of personality. On the Institute of Personality and Ability Testing Anxiety Scale, the sleepy subjects showed higher levels of anxiety than the alert subjects. The data were interpreted as indicating that the sleepy subjects had a sleep debt due to chronic sleep restriction.
TL;DR: There observed an increase in the ratio of stage REM against slow wave sleep (SWS) with age and the nocturnal variation became inapparent with age in % SWS and the phasic components of sREM, while that of % sREM exaggerated at later ages.
Abstract: Twelve polysomnographies were performed on eight cases of the Rett syndrome and the results were compared between cases under and over 5 years of age. There observed an increase in the ratio of stage REM (sREM) against slow wave sleep (SWS) with age. The ratio of the number of mentalis twitch movement (ment TM) during sREM against the number of rapid eye movements (REMs) (reflecting dopaminergic activities) was below normal in the younger cases but increased markedly. The ratio of ment TM in the period of REMs burst against the total ment TM during sREM (reflecting the noradrenergic hypofunction) was high in the younger group, while it decreased later. The nocturnal variation became inapparent with age in % SWS and the phasic components of sREM, while that of % sREM exaggerated at later ages. The early hypofunctions of the noradrenergic and dopaminergic neurons later modified by the serotonergic dysfunction and dopaminergic postsynaptic supersensitivity are suggested.
TL;DR: A follow-up questionnaire was sent to all patients diagnosed with narcolepsy at the Henry Ford Hospital Sleep Disorders and Research Center as mentioned in this paper, which inquired regarding the present, previous, and change in status for the constellation of symptoms with the latest reported onset, including memory problems, problems of daytime function, and nocturnal sleep disturbance.
Journal Article•
TL;DR: A digital recording device developed to monitor heart rate (HR) and breathing sounds (snoring), and used to screen subjects for obstructive sleep apnoea syndrome (OSAS), was investigated.
Abstract: A digital recording device developed to monitor heart rate (HR) and breathing sounds (snoring), and used to screen subjects for obstructive sleep apnoea syndrome (OSAS), was investigated. This device is called the MESAM and is currently commercially available in some western European countries. The computer-based automatic scoring systems provided with the equipment and a hand-scoring technique developed at Stanford and requiring 10-15 min to perform, were used. Polysomnography and MESAM recordings were performed simultaneously on two groups of 25 sleep disorder patients (each with respiratory disturbance index greater than or less than 10). Patients were randomly monitored and records were analysed by two teams blind to the initial clinical impression, to the events which occurred during the recordings, and to each other's findings. Specificity and sensitivity were calculated for each of the MESAM scoring techniques considered, with polysomnography being selected as the recording standard, With "automatic HR scoring" specificity was 12%, sensitivity 92%; with "automatic breathing sounds (snoring)" scoring, specificity was 8% and sensitivity 96%; with "hand-scoring" specificity was 72% and sensitivity 92%. If the three scoring techniques were combined, all patients with a respiratory disturbance index (RD) greater than 10 were recognized as having OSAS.
TL;DR: The results confirm earlier findings indicating that the abnormalities in REM latency and REM density that characterize adults with major depression are absent in adolescents suffering from major depression.
Abstract: Ten adolescents with major depression and 10 age-matched controls were studied with polysomnography for 3 consecutive nights. The sleep records were analyzed for variables pertaining to sleep continuity (total sleep time, sleep efficiency, sleep onset latency, number of awakenings, and number of stage shifts), sleep architecture (Stages 1, 2, 3, and 4), and rapid eye movement (REM) sleep (total) REM sleep time, number of REM periods, REM latency, and REM density). The experimental and control groups were compared on 14 variables with the t test for independent groups. The results indicated that none of the sleep variables differed significantly between the two groups. These results confirm earlier findings indicating that the abnormalities in REM latency and REM density that characterize adults with major depression are absent in adolescents suffering from major depression. Developmental and diagnostic variables are discussed as possible explanations for the sleep differences between adolescents and adults with depressive disorders.
TL;DR: Recent studies support the clinical intuition that sleep apnea is undesirable, and treatment with tracheostomy or NCPAP improves mortality rates to normal.
TL;DR: Correlation of the clinical and physiologic data with the MRI abnormalities suggested that the lesion responsible for CNH in this patient might reside in the medial tegmental parapontine reticular formation.
Abstract: Central neurogenic hyperventilation (CNH), for which there is no effective therapy, can eventually result in respiratory fatigue and death. This report describes a patient with CNH due to a brainstem anaplastic astrocytoma who also exhibited disturbances of sleep and ocular motor function. The CNH responded clinically to morphine sulfate and methadone. Analysis of ventilatory response to CO2 before and after morphine demonstrated a depression of ventilatory response (49 to 53% of baseline) and occlusion pressure response (35 to 50% of baseline) to CO2, with a requirement for high doses of naloxone (10 mg IV) to reverse the effect. Polysomnography revealed sustained hyperventilation, elevated O2 saturation, and low end-tidal CO2 throughout all stages of non-rapid eye movement (NREM) sleep, and absence of rapid eye movement (REM) sleep. Ocular motor evaluation disclosed absence of horizontal and reflexive saccades with compensatory head thrusts. Correlation of the clinical and physiologic data with the MRI abnormalities suggested that the lesion responsible for CNH in this patient might reside in the medial tegmental parapontine reticular formation. Since recurrent episodes of hyperventilation responded in a sustained fashion to IV and oral opiates, this treatment may warrant consideration in other patients with CNH.
TL;DR: Lung function tests, blood gas analysis and right-heart catheterization were performed in 46 consecutive patients and PH and daytime hypoxaemia were associated either with chronic airway obstruction or with severe obesity.
Abstract: In order to study the frequency and the mechanisms of daytime pulmonary hypertension (PH) in obstructive sleep apnoea syndrome (OSAS) lung function tests, blood gas analysis and right-heart catheterization were performed in 46 consecutive patients. OSAS was assessed by polysomnography. 9 patients only (20%) had PH (mean pulmonary artery pressure (Ppa) greater than or equal to 20 mmHg). Patients with PH had lower daytime PaO2 (60.8 +/- 7.6 vs. 76.2 +/- 9.4 mmHg; p less than 0.001), higher daytime PaCO2 (44.8 +/- 4.2 vs. 38.0 +/- 4.0 mmHg; p less than 0.001), lower forced vital capacity (FVC) and forced expiratory volume (FEV1) (p less than 0.001), but the severity of OSAS was not different whether PH was present or not (apnoea index: 62 +/- 34 hour in the PH group vs. 65 +/- 40 hour, apnoea + hypopnoea index 102 +/- 33 hour in the PH group vs. 86 +/- 36 hour, lowest sleep SaO2: 59 +/- 21% in the PH group vs. 66 +/- 18%). There were significant correlations between Ppa and: daytime PaO2 (r = -0.61; p less than 0.001), PaCO2 (r = 0.55; p less than 0.001), FEV1 (r = -0.52; p less than 0.001) but not between Ppa and apnoea index, apnoea + hypopnoea index, lowest sleep SaO2. PH and daytime hypoxaemia were associated either with chronic airway obstruction or with severe obesity.