Paradoxical response to valproic acid in a patient with a hypothalamic hamartoma

We investigated factors of daytime sleepiness in 22 middle-aged male patients with sleep apnea syndrome (SAS) using the Epworth sleepiness scale (ESS) and polysomnography. The subjects were classified into two groups according to ESS score as follows; low ESS group: ESS score < 10, and high ESS group; ESS score > or = 10. ESS score was significantly correlated with duration in which nocturnal oxygen saturation decreased below 90% (Time of SpO2 < 90%) (r = 0.54, p < 0.05). Time of SpO2 < 90% and percent of movement arousals at the termination of apnea/hypopnea (number of movement arousal/total number of apnea/hypopneas x 100) were significantly higher in high ESS group than in low ESS group. Our findings suggest that the severity of oxygen desaturation and sleep fragmentation caused by arousal response at the termination of apnea/hypopnea may be important factors of daytime sleepiness in patients with SAS.     

Nocturnal pulmonary hypertension in an elderly patient with sleep apnea syndrome

We report a case of sleep apnea syndrome (SAS) with nocturnal pulmonary hypertension (NPH) in a 71-year-old man suffering from dyspnea during sleep. Severe snoring at night and daytime sleepiness were noticed before admission by his wife. Nocturnal oxygen desaturation (NOD) was documented with a pulse oximeter and severe sleep apnea syndrome was diagnosed on the basis of results of respiratory inductive plethysmography, an apnea index (AI) > 20, minimum SpO2 56%. NPH was diagnosed by Swan-Ganz catheter. The levels of NPH were severe. Elevation of systolic pulmonary arterial pressure (PAP) above 40 mmHg was observed 137 episodes at night. Both NPH and NOD were improved by 1 L/min of nasal oxygen therapy. A number of episodes of systolic PAP above 40 mmHg with oxygen therapy was 55 episodes. Peak mean PAP was 36 mmHg in room air vs 33 mmHg in oxygen therapy. Minimum SpO2 with oxygen therapy was improved to 69%. Total time of SpO2 < 90% at night was 153 minutes in room air vs 37 minutes in oxygen therapy. In this case, NPH and NOD due to severe SAS were remarkably improved by oxygen therapy.     

Screening of sleep apnea/hypopnea syndrome by home pulse oximetry

We evaluated the diagnostic accuracy and reproducibility of results obtained by home oximetry for the screening of sleep apnea/hypopnea syndrome. Our subjects were 40 patients who underwent home oximetry (12 patients for 1 night, 28 patients for 2 nights) followed by all-night polysomnography. Their mean age was 50.7 +/- 11.2 years; mean body mass index (BMI), 27.6 +/- 4.4 kg/m2; and mean apnea/hypopnea index (AHI), 36.0 +/- 26.0 hr-1. The data obtained by home pulse oximetry were fed into a personal computer, and utilized to calculate the desaturation cycles per hour (oxygen desaturation index (ODI) of 2-4%) and the percentage of time that SpO2 measured less than 90% (T 90). Polysomnography was used to monitor the number of apnea and hypopnea episodes per hour of sleep (AHI). With sleep apnea/hypopnea syndrome defined as AHI > or = 15, the diagnostic sensitivity and specificity of home pulse oximetry were 73.5% and 83.3%, respectively, when ODI-3 > or = 15 was used as the diagnostic standard. Patients who showed false negative results had a lower mean BMI (25.5 +/- 3.0) than those who showed true positive results (28.8 +/- 4.6). The reproducibility of ODI-3 data obtained at home was very high (r = 0.964, n = 28). In conclusion, home pulse oximetry seems to be a very useful tool for the detection of apnea/hypopnea syndrome, but false negative results should be considered a possibility, especially in patients who are not obese.     

The detection of the sleep apnea syndrome in a population of professional drivers

The aim of this study was to reduce the risk of traffic accidents related to obstructive sleep apnea syndrome (OSAS) by means its detection and treatment in a group of 100 commercial drivers from Seville. Besides, to analyze which clinical findings could suggest OSAS. By means a questionnaire we selected subjects without (questionnaire score < 10 points) and with (questionnaire score > or = 10) clinical history of OSAS. In cases with score > or = 10, an overnight home polygraphy was carried out (Apnoescreen II, Jaeger), with measurement of oronasal airflow, chest and abdominal movements, oxygen saturation, electrocardiogram, body position and actimetry. We performed a manual analysis of recordings, and polygraphy was considered to be positive for OSAS if both AHI (respiratory events Index) or DI (desaturation Index) were > or = 10. In these positive cases, overnight conventional polysomnography was carried out (SleepLab, Jaeger), with therapeutic tests with CPAP if OSAS was diagnosed (AHI > or = 10). Average age and BMI (Body Mass Index) were 41.5 +/- 0.9 years and 28.2 +/- 0.4 kg/m2. Questionnaire was positive in 59 subjects, in 35 of whom home polysomnography was done. We did not find differences in age, BMI, neck circumference or symptomatology among these 35 drivers and the 24 remaining subjects in whom home polygraphy was not performed. Home polygraphy was positive in 10 subjects and negative In 25. Drivers in first group were older, heavier and complaint more frequently about snoring, sleep apnea and daytime sleepiness. We did not find differences in neck circumference, waist/hip ratio nor alcohol consumption between both groups. From the group with positive polygraphy, we performed conventional polysomnography in 8 cases and OSAS was diagnosed in 5 (in all cases, treatment with CPAP was started). This study does not provide data about prevalence, but it seems that the percentage of our drivers with OSAS could be lightly higher than the prevalence in general population. These subjects seem to be older, heavier and complaint more frequently about snoring, sleep apnea and daytime sleepiness.     

Neuropeptide regulation of proinflammatory cytokine responses

Severe postoperative hypoxaemia during sleep may increase the risk of postoperative cardiovascular complications. We hypothesized that the severity of hypoxic episodes after surgery are related to the presence of preoperative sleep-disordered breathing (SDB). We tested this hypothesis in a multicentre study designed to elucidate the major risk factors for development of postoperative nocturnal desaturations. We performed overnight oximetry before operation and for one night between the second and fourth day after operation in 80 patients undergoing major surgery. We calculated oximetry variables such as oxygen desaturation index (ODI), defined as the number of oxygen desaturations exceeding 4% below baseline, percentage time spent at SpO2 < 90% (CT90, %) and lowest SpO2 value. After operation, although the change in ODI was not significant (P = 0.34), deterioration in CT90 and lowest SpO2 values were significant (P = 0.036 and P = 0.007, respectively). Multivariate analysis of possible risk factors for postoperative desaturations revealed that preoperative hypoxaemia and apnoea witnessed by others were highly correlated with postoperative hypoxaemia.     

Geranylgeranylacetone, an anti-ulcer drug, stimulates hexosamine production in a rat gastric mucosal cell line through binding to a specific cytosolic protein

It is not known whether patients with acute myocardial infarction (MI) with coexistent obstructive sleep apnea (OSA) have a poor clinical course during the acute phase of MI. Therefore, we investigated the impact of OSA on in-hospital morbidity and mortality during an acute MI. Patients admitted to the intensive cardiac unit (ICU) with acute MI underwent Holter monitoring and night pulse oximetry (SpO2). During the first complete day at the ICU, both recordings (ECG and SpO2) were matched in time to determine association between cardiac arrhythmias and hypoxemia episodes. We identified and compared 55 heavy snorers with daytime sleepiness who showed more than 10 episodes of desaturation per hour on pulse oximetry (OSA group), and 196 nonOSA patients. There was an increase in the incidence of premature ventricular contraction (PVC, p < 0.05) and couplets PVC (p < 0.05) in OSA patients; the proportion of those arrhythmias increased in parallel with desaturation episodes in the OSA group. There were no differences between OSA and nonOSA groups for major MI complications (38.2% vs 34.2%, p > 0.05), ICU/hospital stay (3.6 +/- 1.2 vs 2.7 +/- 0.9 days, p > 0.05), or mortality within 30 days (14.5% vs 12.2%, p > 0.05). In conclusion, despite the greater incidence of some types of cardiac arrhythmias during an acute MI in OSA, these patients have the same clinical course in hospital and mortality rate as nonOSA patients.     

Apnoea and oximetric desaturation in patients receiving epidural morphine after gastrectomy: a comparison of intermittent bolus and patient controlled administration

The number of apnoeic episodes and arterial oxygen desaturations were measured preoperatively and for sixty hours postoperatively in twenty ASA status 1-2 patients scheduled for elective gastrectomy. Monitoring included continuous pulse oximetry, respiratory inductive plethysmography and repeated arterial blood gas analysis. The number and magnitude of apnoeas and desaturation episodes were compared between two postoperative analgesic regimens of epidural morphine; intermittent bolus injection (Group B, n = 10), and patient controlled administration with continuous infusion (Group P, n = 10). Morphine dose, P(a)CO2 and mean SpO2 values were similar between the two groups. Although the number of central apnoeas with SpO2 < 90% was greater in Group B, other episodes of apnoea or desaturation were similarly seen preoperatively. In the postoperative period, central apnoeas with SpO2 < 90% were significantly increased in Group B, while no change was seen in Group P. Apnoeas with SpO2 < 80% were only seen in Group B. We conclude from these results that postoperative apnoeas and episodic desaturations are greatly influenced by the different modes of opioid administration.     

Sleep-related O2 desaturation and daytime pulmonary haemodynamics in COPD patients with mild hypoxaemia

It has been hypothesized but not firmly established that sleep-related hypoxaemia could favour the development of pulmonary hypertension in chronic obstructive pulmonary disease (COPD) patients without marked daytime hypoxaemia. We have investigated the relationships between pulmonary function data, sleep-related desaturation and daytime pulmonary haemodynamics in a group of 94 COPD patients not qualifying for conventional O2 therapy (daytime arterial oxygen tension (Pa,O2) in the range 7.4-9.2 kPa (56-69 mmHg)). Nocturnal desaturation was defined by spending > or = 30% of the recording time with a transcutaneous O2 saturation < 90%. An obstructive sleep apnoea syndrome was excluded by polysomnography. Sixty six patients were desaturators (Group 1) and 28 were nondesaturators (Group 2). There was no significant difference between Groups 1 and 2 with regard to pulmonary volumes and Pa,O2 (8.4+/-0.6 vs 8.4+/-0.4 kPa (63+/-4 vs 63+/-3 mmHg)) but arterial carbon dioxide tension (Pa,CO2) was higher in Group 1 (6.0+/-0.7 vs 53+/-0.5 kPa (45+/-5 vs 40+/-4 mmHg); p<0.0001). Mean pulmonary artery pressure (Ppa) was very similar in the two groups (2.6+/-0.7 vs 2.5+/-0.6 kPa (19+/-5 vs 19+/-4 mmHg)). No individual variable or combination of variables could predict the presence of pulmonary hypertension. It is concluded that in these patients with chronic obstructive pulmonary disease with modest daytime hypoxaemia, functional and gasometric variables (with the noticeable exception of arterial carbon dioxide tension) cannot predict the presence of nocturnal desaturation; and that mean pulmonary artery pressure is not correlated with the degree and duration of nocturnal hypoxaemia. These results do not support the hypothesis that sleep-related hypoxaemia favours the development of pulmonary hypertension.     

Simultaneous laboratory-based comparison of ResMed Autoset with polysomnography in the diagnosis of sleep apnoea/hypopnoea syndrome

ResMed Autoset (AS) is a simplified diagnosis system for obstructive sleep apnoea/hypopnoea syndrome (OSAS) based on the respiratory flow/time relationship by pressure variation measured through simple nasal prongs. A multicentre prospective trial was used to compare AS and polysomnography (PSG) for diagnosing 95 patients, with suspected OSAS. Physicians gave a pretest probability of the patient having OSAS. The apnoea/hypopnoea index (AHI) was compared between the two methods of diagnosis for the whole population and for subgroups according to the pretest probability. Twenty-four patients had AHI < 15 events x h(-1) on PSG and 19 AHI 15-30, and 52 patients had AHI > or = 30. Correlation between AHI assessed by AS and PSG was r=0.87 for total sleep time (TST), p<0.0001. A Bland and Altman plot gave an agreement between the two methods of +/-40%. For a threshold of AHI > or = 15 events x h(-1) to diagnose OSAS, AS has a sensitivity of 92%, specificity of 79%, positive predictive value of 93% and negative predictive value of 76%. With a pretest probability > or = 80%, sensitivity and positive predictive value were 98 and 100% respectively. Of six false negative, four had a high pretest probability (> 80%) or Epworth score > or = 10. Using these parameters as a criterion for proceeding to PSG after a negative AS study would mean that two apnoeic patients (AHI 20 and 17 events x h(-1) by PSG) would escape detection. The Autoset is useful for the detection of obstructive sleep apnoea but with high pretest probability and a negative Autoset result polysomnography should be performed.     

Therapy with nasal CPAP (continuous positive airway pressure) in patients with obstructive sleep apnea syndrome (OSAS). I: Long-term acceptance of nasal CPAP

BACKGROUND: Nocturnal ventilation with nCPAP has been established as the safest and most efficient nonsurgical treatment for OSAS. Long-term results, however, are determined by the patients' compliance with therapy. The aim of this study was the objective measurement of long-term acceptability of nCPAP therapy in all patients receiving this treatment in our sleep laboratory between January 1990 and March 1995. METHODS: We prospectively investigated 41 patients (36 male, 5 female) with moderate to severe OSAS who received nCPAP therapy. Mean time of follow-up was 20.6 months, ranging from 1.2 to 53.5 months. Therapy was indicated when OSAS was confirmed by cardiorespiratory polygraphy and either (1) the patient complained of daytime sleepiness or (2) the patient possessed an apnea-hypopnea index greater than 30/h or when the mean oxygen desaturation was below 80% regardless of the presenting symptoms. The compliance with treatment was defined as a mean rate of use of over 5 hours per night calculated from the time counter on the nCPAP machine. RESULTS: 33 patients (88.5%) have continued using nCPAP until the present time but only 24 patients (59%) met our criteria for long-term acceptance and this group was identified as responders. We found no significant differences in age, body mass index, apnea-hypopnea index, and nCPAP-pressure between responders and non-responders. CONCLUSION: Although nCPAP is the safest treatment for OSAS, there is still a large group of patients with moderate to severe OSAS who are not efficiently treated with nCPAP because of the low long-term acceptability of this therapy. With respect to this group of patients, surgical approaches have to be considered as an alternative therapy.     

Influence of sleep apnea on nocturnal blood pressure

In the present study, we subjected 65 patients to overnight monitoring and continuous nocturnal blood pressure measurement in order to assess the influence of sleep apnea on the circulatory system. Thirty-one patients were compared before and after surgery. The severity of sleep apnea was classified by Apnea Hypopnea Index (AHI), the duration of exposure to low-level oxygen (calculated as the desaturation time: DT), and increment of blood pressure. Before surgery, a significant correlation was noted between the DT and blood pressure changes. Therefore, this index was considered useful for assessing the influence of sleep apnea on nocturnal blood pressure. After surgery, improvement of AHI was greater than 50% in 19/31 patients (61.3%), and this result was almost the same as described in the literature. The improvements in DT and BP change were greater than 50% in 21/31 (67.7%) and 14/31 (45.2%), respectively. With regard to severity before surgery, AHI was > or = 50 and DT was > or = 40% in 10 and 18 patients, respectively. Nineteen patients had BP changes > or = 40 mmHg. After surgery, 1,5, and 2, patients, respectively, still showed these values. Thus, a beneficial effect of surgery was demonstrated.     

The efficacy of oral appliances in the treatment of persistent sleep apnea after uvulopalatopharyngoplasty

Twenty-four patients who failed uvulopalatopharyngoplasty (UPPP) for obstructive sleep apnea (OSA) had an adjustable oral (Herbst) appliance made to treat the persistent apnea. Six patients discontinued the device prior to sleep evaluation. Eighteen patients had polysomnographic evaluations at baseline, post-UPPP, and with the Herbst appliance in place. The apnea-hypopnea index baseline (AHI) and arterial oxygen saturation (SaO2) nadir were 42.3+/-6.1 and 83.6+/-1.8%, respectively. There was no significant change in either parameter with surgery. With the oral appliance, the AHI fell to 15.3+/-4.4 (p < or = 0.01) and the SaO2 nadir increased to 87.9+/-1.2% (p < or = 0.05). Ten of the patients had control of the OSA with the Herbst appliance with a fall in the AHI to < 10. There were, in addition, two partial responders as defined by an AHI of <20 and a >50% fall in AHI compared with baseline and post-UPPP values. All but one of the responders and partial responders had complete resolution of subjective symptoms of daytime sleepiness with the appliance. An adjustable oral appliance appears to be an effective mode of therapy to control OSA after an unsuccessful UPPP.     

The effect of low flow oxygen on sleep-disordered breathing and oxygen desaturation. A study of patients with chronic obstructive lung disease

Oxygen desaturation occurs during sleep in many patients with chronic obstructive lung disease (COLD) and is often caused by sleep-disordered breathing (SDB). Nocturnal oxygen therapy should improve nighttime hypoxemia, but might also worsen SDB. Using standard polysomnographic techniques, we evaluated the frequency and duration of oxygen desaturation and SDB during sleep in 11 patients with stable COLD. During half of the night the patients breathed air through a nasal cannula and during the other half of the night they breathed oxygen at 2 liters per minute. Five patients had arterial lines inserted for determination of arterial blood gas levels during periods of SDB or desaturation. The ten men and one woman slept 70 minutes (52 percent of time in bed) while on air and 111 minutes (80 percent of time in bed) while on oxygen (p < 0.001). Oxygen therapy reduced the number of episodes of desaturation per hour and the time spent in desaturation. However, there was no difference between air and oxygen in episodes of SDB per hour, the duration of episodes of SDB, baseline sleeping PaCO2 or PaCO2 during episodes of desaturation or SDB. Therefore, in most patients with stable COLD, administration of oxygen at 2 liters per minute improves oxygenation, prolongs sleep, but does not adversely affect SDB.     

Acute von Willebrand factor secretion from the endothelium in vivo: assessment through plasma propeptide (vWf:AgII) Levels

STUDY OBJECTIVES: Patients with coronary heart disease (CHD) and obstructive sleep apnea may have an increased cardiac risk due to nocturnal myocardial ischemia triggered by apnea-associated oxygen desaturation. Sleep structure in patients with obstructive sleep apnea is fragmented by activation of the central nervous system (CNS) (arousal) due to obstructive apneas. Nocturnal myocardial ischemia may lead to activation of the CNS as well. PATIENTS: Fourteen patients with obstructive sleep apnea and CHD disease and seven patients suffering from obstructive sleep apnea without CHD were studied. Overnight sleep studies and simultaneous six-lead ECG recordings were performed. In addition, sleep studies and ECG recordings were performed with administration of a sustained-release nitrate in these patients in a double-blinded crossover design. RESULTS: Analysis of three nights' recordings revealed 144 episodes of nocturnal myocardial ischemia in six subjects. Five patients had underlying CHD and one patient exhibited diffuse wall defects of the coronary arteries; also, 85.4% of ischemic episodes were concomitant with apneas and oxygen desaturation > 3%, and 77.8% of ischemic episodes occurred during rapid eye movement (REM) sleep, although total amount of REM sleep was only 18% of total sleep time. Mean oxygen saturation was significantly lower (p < 0.05) during apnea-associated ischemic episodes than during nonapnea-associated ischemia (77.3% vs 93.1%). Nitrate administration did not reduce ischemic episodes. Sleep architecture (macrostructure) exhibited a reduction in sleep stages non-REM 3 and 4 and REM sleep. Comparing the microstructure of sleep (arousals) within episodes with and without ischemia but similar criteria like sleep stage, apnea activity, and oxygen saturation, we found significantly more (p < 0.01) and severe (p < 0.001) arousals during periods with myocardial ischemia than during control episodes. In addition, microstructure of sleep was disturbed by myocardial ischemia itself in absence of apneas. CONCLUSION: It is concluded that patients with CHD and obstructive sleep apnea are endangered by apnea-associated ischemia and that these ischemic episodes lead to activation of the CNS and additional fragmentation of sleep. Patients with nocturnal ischemia should be screened for underlying sleep apnea even if nitrate therapy fails.     

Circadian and ultradian variations of leptin in normal man under continuous enteral nutrition: relationship to sleep and body temperature

To determine the influence of circadian rhythmicity and sleep on the 24-h leptin diurnal variations, plasma leptin levels were measured at 10-min intervals over 24 h in seven normal subjects, once during nocturnal sleep, and once after an 8-h shift of sleep. The subjects were submitted to constant conditions (continuous enteral nutrition and bed rest in controlled chambers). Body temperature and plasma glucose and insulin levels were measured simultaneously. During nighttime sleep, leptin levels increased to a maximum (109.9 +/- 2.5% of the 24-h mean) and then decreased to reach a nadir in the late afternoon. The mean diurnal variation was 18.0 +/- 3.8% of the 24-h mean. In the daytime sleep condition, leptin levels rose during the night of deprivation to a maximum of 104.7 +/- 2.3% of the 24-h mean, decreased to a minimum around 0700 h, and then rose again during diurnal sleep (108.4 +/- 3.1% of the 24-h mean); the mean diurnal variation was 13.4 +/- 3.6% of the 24-h mean. ANOVA revealed a significant interaction between time of day and sleep effects (P < 0.05). The diurnal and the sleep-related variations of plasma leptin mirrored those of body temperature and roughly paralleled those of plasma glucose and insulin; the amplitudes of the diurnal leptin variations were significantly correlated with the amplitudes of the diurnal body temperature variations (P < 0.05). Plasma leptin levels also displayed irregular pulses of low amplitude (mean duration, 70 min) that were not affected by sleep, but were associated with a significant decrease in glucose and insulin levels (P < 0.01). These results demonstrate that under continuous enteral nutrition, plasma leptin levels are modulated by both a slight circadian component and sleep, which interact under normal conditions, and suggest that leptin is implicated in circadian thermoregulatory adjustments.     

Sex-specific sleep anamnesis in obstructive sleep apnea syndrome?

Although the prevalence of obstructive sleep apnea syndrome (OSAS) is about 4% in men and 2% in women, women are underrepresented in clinical routine. The aim of this study was to determine whether differences in clinical features of OSAS may in part explain the bias observed. 224 men and 24 women with polysomnographically confirmed OSAS filled in a symptom-focussed multiple-choice questionnaire. Polysomnographical results were comparable in both groups. With regard to snoring, daytime sleepiness and tendency of falling asleep there were no differences between both groups. Women more frequently complained about difficulties of initiating and maintaining sleep and about apneas. Further investigations have to concentrate on the pathomechanisms of OSAS in women which may in part explain the gender differences in sleep apnea associated symptoms.     

Resolution of obstructive sleep apnoea with growth in the Robin sequence

A 12 year old female with the Robin sequence presented with a one year history of snoring, witnessed apnoeas and daytime sleepiness. Surgery in early childhood had consisted of cleft palate repair, tonsillectomy and adenoidectomy and, later, revision palatoplasty. Overnight polysomnography (PSG) demonstrated severe obstructive sleep apnoea syndrome with an apnoea/hypopnoea index (AHI) of 49 events x h(-1), and repetitive oxygen desaturations below 50%. Nasal continuous positive airway pressure (nCPAP) effectively controlled her sleep abnormalities. After 3 yrs of nCPAP therapy, she requested discontinuation and was fully reassessed. PSG without nCPAP revealed an AHI <5 events x h(-1) with no desaturations below 90% and normal sleep quality. A repeat lateral cephalometrogram showed increased mandibular length and posterior airway space and reduced soft palate length. The patient remains asymptomatic 9 months following nCPAP discontinuation. This case indicates that nasal continuous positive airway pressure is an effective nonsurgical therapy in children with obstructive sleep apnoea syndrome and the Robin sequence. It is likely that mandibular growth, increase in mandibular length and enlargement of the posterior airway space was responsible for the resolution of obstructive sleep apnoea syndrome in this case.     

Characteristics of apneas and hypopneas during sleep and relation to excessive daytime sleepiness

STUDY OBJECTIVES: One of the most important symptoms in patients evaluated for possible obstructive sleep apnea syndrome is excessive daytime sleepiness, but the measures of apnea severity and of sleepiness used most commonly have not generally shown strong associations. We explored whether information recorded during standard polysomnography, other than the overall rate of apneas and hypopneas per hour of sleep (AHI), might help explain the measured severity of sleepiness. DESIGN: Observational SETTING: A clinical sleep laboratory in a university hospital PATIENTS: N = 1,146 patients evaluated for suspected sleep-disordered breathing with nocturnal polysomnograms and multiple sleep latency tests. RESULTS: The AHI during supine sleep (recorded in a subgroup of n = 169 subjects), the rate of apneas (n = 1,146), and the rate of obstructive apneas (n = 1,146) were particularly useful in explaining variation in measured levels sleepiness; rates of hypopneas and central apneas were less useful (n = 1,146). In addition, the minimum recorded oxygen saturation (n = 1,097) was as important as the AHI to the level of sleepiness. CONCLUSIONS: In an attempt to explain excessive daytime sleepiness among patients evaluated for sleep-disordered breathing, additional insight is provided by observation of supine sleep during polysomnography, by emphasis on apneas rather than hypopneas, by emphasis on obstructive rather than central events, and by consideration of the minimum oxygen saturation.     

Experimental fetal transesophageal and intracardiac echocardiography utilizing intravascular ultrasound technology

The effects of epidural fentanyl on the incidence of maternal hypoxaemia during labour and on neonatal welfare were examined. Women were randomly allocated to receive one of two epidural infusions, bupivacaine 0.125% alone or bupivacaine 0.0625% with 2.5 micrograms.ml-1 fentanyl, and maternal arterial oxygen saturation was monitored continuously until delivery. The median incidence of desaturation (SpO2 < 95%) during the active phase of the second stage of labour was significantly greater in the fentanyl group than in controls (2.9 versus 0.6 min.h-1, p = 0.02). Similarly, the incidence of desaturation to SpO2 < or = 90% was greater in the fentanyl group than in controls (p = 0.02). There was no correlation between maternal oxygenation or plasma fentanyl concentration and neonatal welfare as measured by umbilical arterial and venous blood gas and acid base status, Apgar score and Neurologic and Adaptive Capacity Score.     

Short-duration nocturnal hypoxemia and persistent pulmonary hypertension

Can daily short-duration hypoxemia (4-8 hours) induce pulmonary hypertension and right ventricular hypertrophy? A clinical model of this type of hypoxemia does exist: isolated nocturnal hypoxemia in patients with obstructive sleep apnea syndrome (OSAS) or chronic obstructive pulmonary disease (COPD). By investigating the pulmonary hemodynamics of these patients, it should be possible to determine whether nocturnal hypoxemia alone can induce pulmonary hypertension. Although nocturnal hypoxemia (in OSAS as well as in COPD) can induce acute episodes of pulmonary hypertension, it would not appear that nocturnal hypoxemia alone would be sufficient to provoke permanent diurnal pulmonary hypertension. This is the conclusion of recent studies concerning diurnal pulmonary hemodynamics in OSAS and COPD patients exhibiting minimal hypoxemia during the day but significant nocturnal desaturation. The therapeutic consequences of these data, particularly in COPD are important: current evidence is insufficient to treat with nocturnal oxygen therapy COPD patients who have minimal diurnal hypoxemia but significant nocturnal desaturation.