Degree Of Desaturation Research Articles

Sleep architecture and respiratory disturbances in children with obstructive sleep apnea.

Little is known regarding sleep architecture in children with the obstructive sleep apnea syndrome (OSAS). We hypothesized that sleep architecture was normal, and that apnea increased over the course of the night, in children with OSAS. We analyzed polysomnographic studies from 20 children with OSAS and 10 control subjects. Sleep architecture was similar between the groups. Of obstructive apneas 55% occurred during rapid eye movement (REM) sleep. The apnea index, apnea duration, and degree of desaturation were greater during REM than non-REM sleep. OSAS data from the first and third periods of the night (periods A and C) were compared. Both the overall and the REM apnea index increased between periods A and C (11 to 25/h, p < 0.02; and 24 to 51/h, p < 0.01, respectively). There was no difference in Sa(O(2)) over time. Spontaneous arousals, but not respiratory-related arousals, were more frequent during non-REM than REM sleep; these did not change from periods A to C. We conclude that children with OSAS have normal sleep stage distribution. OSAS is predominantly a REM phenomenon in children. Obstructive apnea worsens over the course of the night, independent of the changing amounts of REM sleep. We speculate that this increase in apnea severity may be secondary to upper airway muscle fatigue, changes in upper airway neuromotor control, or changes in REM density.

Lipid profile: a useful chemotaxonomic marker for classification of a new cyanobacterium in Spirulina genus

The morphological, physiological and genetic characteristics of an isolate cyanobacterium from hard sand of the lake Venere in the Pantelleria island (Italy) were described. The isolate with a small-size coiled helix shape, growing optimally at pH 9.2–9.5 at 30°C under continuous illumination and aeration, possessed a 61.5 mol% of Guanine + Cytosine content of DNA. The lipid profile showed the presence of mono-, di-glycosyl, sulphoquinovolosyl and phosphatidyl (MGDG, DGDG, SQDG and PG). The fatty acid profile was also studied, characterized by the absence of γ-linolenic acid and the presence of saturated and monounsaturated C16 and C18. The latter was also present as a dienoic component. The fatty acid composition was affected by growth temperature by increasing the degree of desaturation at a lower temperature and the biosynthesis of shorter acyl chains. The effects of growth conditions other than temperature, physical, nutritional and chemical on lipid composition were also studied. The overall features of the cyanobacterium isolated from Pantelleria clustered it into Spirulina genus.

Effects of Chloroacetanilide Herbicides on Membrane Fatty Acid Desaturation and Lipid Composition in Rice, Maize, and Sorghum

The effects of the chloroacetanilide herbicides pretilachlor and metolachlor on the composition of membrane fatty acids and lipids were studied in dark-grown rice (Oryza sativa L., cv. Lemont), maize (Zea mays L., cv. Cargill 7567), and grain sorghum (Sorghum bicolor (L.) Moench., cv. G522DR) seedlings. The main desaturated fatty acid found in control and herbicide-treated seedlings of rice, maize, and grain sorghum was 18:2. Applied at their respective GR50 concentrations, pretilachlor (0.1 μM) and metolachlor (10 and 5 μM) did not inhibit the overall desaturation of 18:1 to 18:2 and 18:3 fatty acids in root and shoot tissues of rice, maize, or grain sorghum. However, seedlings of the three grass species treated with the two herbicides showed some decrease in 18:1 and a concomitant increase in 18:2 or 18:3 fatty acids, compared to control plants. The safeners fenclorim, benoxacor, and fluxofenim protected the three grass crops against injury caused by pretilachlor and metolachlor but did not change the composition of membrane fatty acids in any of the three plant species. The effects of metolachlor and pretilachlor on plant membranes were determined also by a detailed analysis of individual lipids extracted from the roots of the three grasses. Metolachlor and pretilachlor did not alter the composition of membrane lipids and the degree of desaturation of fatty acids in the individual lipids found in the roots of rice, maize, and grain sorghum. The obtained results do not seem to support recent suggestions correlating the herbicidal activity of chloroacetanilide herbicides with an inhibition of fatty acid desaturation in algal species. The mechanism of action of these herbicides may be related to an inhibition of the synthesis of very long chain fatty acids or of the incorporation of unsaturated fatty acids into nonlipids of plants.

Effects of varying approaches for identifying respiratory disturbances on sleep apnea assessment.

Varying approaches to measuring the respiratory disturbance index (RDI) may lead to discrepant estimates of the severity of sleep-disordered breathing (SDB). In this study, we assessed the impact of varying the use of corroborative data (presence and degree of desaturation and/or arousal) to identify hypopneas and apneas. The relationships among 10 RDIs defined by various definitions of apneas and hypopneas were assessed in 5,046 participants in the Sleep Heart Health Study (SHHS) who underwent overnight unattended 12-channel polysomnography (PSG). The magnitude of the median RDI varied 10-fold (i.e., 29.3 when the RDI was based on events identified on the basis of flow or volume amplitude criteria alone to 2.0 for an RDI that required an associated 5% desaturation with events). The correlation between RDIs based on different definitions ranged from 0.99 to 0.68. The highest correlations were among RDIs that required apneas and hypopneas to be associated with some level of desaturation. Lower correlations were observed between RDIs that required desaturation as compared with RDIs defined on the basis of amplitude criteria alone or associated arousal. These data suggest that different approaches for measuring the RDI may contribute to substantial variability in identification and classification of the disorder.

Interrelationships between low density lipoprotein receptor defect, serum fatty acid composition, and serum cholesterol concentration

It is known that, in the general human population, serum fatty acid composition is correlated with serum triacylglycerol and cholesterol concentrations. The goal of the present study was to analyze whether the same is true of individuals who have a low density lipoprotein receptor (LDL-R) defect. Concentrations of 16 different fatty acids, cholesterol, triacylglycerol, and major lipoproteins in serum were determined in eight individuals who had (FH-North Karelia), the most common LDL-R defect in Finland, which causes familial hypercholesterolemia, and in their 30 relatives belonging to a single large pedigree as controls. The average number of double bonds (i.e., degree of desaturation) in serum fatty acids correlated negatively with the concentrations of serum total cholesterol ( r = 0.27, P < 0.05) and total triacylglycerol ( r = −0.71, P < 0.001) and positively with the number of fish meals per week ( r = 0.50, P < 0.01), which was analyzed in all pedigree members jointly. These effects were similar in individuals having LDL-R defect, in which group the correlation coefficients were −0.31 ( P = NS), −0.99 ( P < 0.001), and 0.79 ( P = NS) for serum total cholesterol, triacylglycerol, and weekly fish meals, respectively. Thus, LDL-R defect does not impair the correlation between serum fatty acid composition and serum triacylglycerol concentration. This result is in agreement with dietary studies that have shown that familial hypercholesterolemia patients respond very favorably to dietary therapy.

Subcutaneous, omentum and tumor fatty acid composition, and serum insulin status in patients with benign or cancerous ovarian or endometrial tumors. Do tumors preferentially utilize polyunsaturated fatty acids?

The relationships between the fatty acid composition of cancerous endometrium and ovary, and peripheral adipose tissues were studied in Israeli Jewish women, and are presented together since no differences were shown between them. The results suggest a mobilization of linoleic acid from subcutaneous and omental depots and its incorporation into tumors accompanied by a high degree of desaturation. High blood insulin concentrations characterized patients with stage I and II disease, and low concentrations characterized patients with advanced degrees of malignancy.

EEG Frequency Changes During Sleep Apneas

To study the effect of transient, apnea-induced hypoxemia on electrocortical activity, five patients with severe obstructive sleep apnea syndrome (OSAS) were investigated during nocturnal sleep. Polysomnographic and simultaneous digitized electro encephalographic (EEG) recordings for topographic and compressed spectral array analysis were made. The EEG recordings were timed exactly to respiratory events. During nonrapid eye movement (NREM) apnea, delta band amplitude increased, starting on average 13 seconds after the apnea onset. Average differences were 268% between initial and maximal values and 202% between initial and final values. In contrast, significant increases in delta amplitudes between the onset and end of REM apneas did not occur, although some caused deep oxygen desaturations. Changes in delta activity were not correlated to NREM apnea duration or degree of desaturation. These results indicate that the increased delta activity during NREM apneas may not be caused by arterial hypoxemia. It could instead be due to either an arousal mechanism, since arousals may be preceded by slow waves in EEG, or to a breakthrough of slow-wave-sleep activity. The sleep disturbance in severe OSAS may create such a propensity for slow-wave sleep that stages pass much more rapidly than in normal persons.

Increased norepinephrine variability in patients with sleep apnea syndrome

To assess the plasma arterial catecholamine response to nocturnal desaturation in a group of patients with a history suggestive of sleep apnea. At a Veterans Affairs hospital, 10 patients who had a history consistent with sleep apnea syndrome were involved in the study. Arterial plasma catecholamines were measured at varying intervals during a 5 1/2-hour sleep study. Eighteen samples per patient were analyzed. As the hemoglobin saturation decreased, the variability in plasma norepinephrine increased significantly (r = -.78, P = 0.004). As the hemoglobin saturation fell, there was a trend towards higher concentrations of plasma norepinephrine (r = -.53, P = 0.06). As the hemoglobin saturation decreased, the variability in plasma epinephrine concentration was not significant (r = .42). The association between the degree of desaturation and the variability in norepinephrine suggests that norepinephrine is released in response to nocturnal desaturation.

Exertional oxygen of limited benefit in patients with chronic obstructive pulmonary disease and mild hypoxemia.

It is unclear whether short-term benefits from supplemental oxygen translate into improved quality of life in patients with severe COPD. In a 12 wk double-blind randomized crossover study, we assessed the effects of supplemental air and oxygen on exercise performance (step tests and 6 min walking distance [6MWD]) initially and after two 6 wk periods at home using exertional cylinder air or oxygen. We measured quality of life at baseline and after the two 6 wk domiciliary periods. The 26 patients (24 males) had a mean age of 73 +/- 6 yr; mean FEV1, 0.9 +/- 0.4 L; mean DLCO, 10.6 +/- 2.4 ml/min/mm Hg; mean resting PO2, 69 +/- 8.5 (range 58 to 82) mm Hg; mean PCO2, 41 +/- 3.3 mm Hg; and mean resting SaO2, 94 +/- 2.1 (mean +/- SD). Laboratory tests were performed breathing intranasal air or oxygen at 4 L/min, and measurements were made of SaO2 and Borg dysnea scores. Supplemental oxygen increased 6MWD and steps by small, statistically significant increments acutely at baseline and after 6 and 12 wk, without corresponding falls in Borg score. Degree of desaturation at baseline did not correlate with increase in 6MWD or steps achieved at baseline or at 6 or 12 wk, nor with the domiciliary gas used. There was no difference in 6MWD or steps achieved while breathing supplemental oxygen after 6 wk of domiciliary oxygen compared with domiciliary air. Small improvements in quality of life indices were found after domiciliary oxygen, and mastery also improved after domiciliary air. There were no differences in quality of life, however, when domiciliary oxygen was compared with domiciliary air. Although oxygen supplementation induced small acute increments in laboratory exercise performance, such improvements had little impact on the patients' daily lives.

Sleep stage influences the hemodynamic response to obstructive apneas.

Blood pressure (BP) rises at the termination of obstructive episodes in patients with sleep apnea. Although the relationship of these BP elevations to oxygen saturation (SaO2) and arousal has been explored, the influence of sleep stage is undefined. To examine the effects of sleep stage on the postapnea BP elevation, we enrolled 12 patients with obstructive sleep apnea (OSA), and successfully collected data from seven of these (all male). Subjects slept overnight in the sleep laboratory, with full sleep and respiratory monitoring. Arterial pressure was assessed continuously with a radial artery catheter (six patients) or with digital photoplethysmography (one patient). Apneas occurring in both rapid eye movement (REM) and non-rapid eye movement (NREM) sleep were matched for duration and degree of desaturation. When mean arterial pressure (MAP) at termination of apneas during NREM sleep associated with SaO2 nadirs 78 to 82% (NREM 80%) was compared with MAP following apneas in REM with the same SaO2 nadir (REM 80%), there was a significant difference (NREM 80% 122 +/- 15.3 mm Hg, REM 80% 132 +/- 11.0; p = 0.0109). We also analyzed the effect of oxygen desaturation on MAP during REM sleep, by comparing events with SaO2 nadirs of 78 to 82% with events with nadirs of < 75% (REM < 75%). In REM, further desaturation was associated with significant lengthening of the obstructive episodes and significantly higher postapnea BP increases (REM 75% 143 +/- 19.9 mm Hg, p = 0.0392). We conclude that sleep stage alters the hemodynamic response to obstructive apneas during sleep.

Arterial oxygen saturation during upper gastrointestinal endoscopy: Influence of sedation and operator experience

In order to compare the effects of Diazemuls and midazolam on arterial oxygen saturation during upper gastrointestinal endoscopy, 120 patients were randomly allocated to receive Diazemuls, midazolam, or normal saline. Endoscopy was performed by one consultant or one of four residents. Arterial oxygen saturation was monitored continuously during endoscopy by means of a Biox III pulse oximeter and ear probe. Oxygen saturation fell during endoscopy in all three groups, but no significant differences between the groups were detected at any stage of the procedure. When all groups were combined, there was significantly less desaturation when the consultant performed the endoscopy, and he was also significantly faster in carrying out endoscopy than the residents in each group. When an inexperienced resident was compared with one with at least 6 months of experience, there were significant differences in degree of desaturation, lowest value during endoscopy and tolerance score. It is suggested that the patient at risk of hypoxemia should, if possible, be endoscoped by an experienced endoscopist.

Sleep studies of respiratory function and home respiratory support.

Breathing differs when we are awake and asleep. Cortical stimulation of the respiratory centres wanes with the onset of sleep, resulting in a decrease in chemosensitivity to carbon dioxide and oxygen tensions; a reduction in upper airway, intercostal, and accessory muscle tone, particularly in rapid eye movement sleep; altered responses to elastic and resistive respiratory loads; and a reduction in metabolic rate.1 Failure to adapt to these physiological processes in predisposed subjects sets the scene for the development of sleep disordered breathing, in the form of the sleep apnoea syndromes and nocturnal hypoventilation (fig 1). Night time and daytime respiratory function is linked in that although obstructive apnoeas occur only during sleep, these can ultimately lead to diurnal abnormalities of breathing. Nocturnal hypoventilation either accompanies or heralds the development of diurnal respiratory failure. FIG 1 Links between sleep disordered breathing conditions This syndrome is characterised by snoring and repeated episodes of complete or partial obstruction of the upper airway which cause sleep fragmentation, fluctuations in arterial oxygen saturation, and daytime somnolence. There is no satisfactory definition of the syndrome, as a spectrum exists which ranges from normal breathing through snoring to severe effects. It is also clear that some snorers, in the absence of apnoeic episodes, may also suffer from disrupted sleep (the upper airway resistance syndrome).2 For diagnostic purposes the occurrence of 15 or more episodes of apnoea or hypopnoea per hour (apnoea/hypopnoea index) is usually considered abnormal. In each person the severity of the condition can be expressed by the apnoea/hypopnoea index, but it is the consequences of these events in terms of degree of desaturation, sleep fragmentation, and cardiovascular abnormalities such as hypertension and dysrhythmias which are crucial. The effects of untreated obstructive sleep apnoea/hypopnoea syndrome are listed in the box. View this table: Long term effects of untreated obstructive …

Preoxygenation techniques: the value of nitrous oxide

Changes in arterial oxygen saturation during induction of anaesthesia and intubation were studied using the pulse oximeter. Seventy-five young ASA I patients undergoing elective uncomplicated surgery were divided equally into three groups. The patients were preoxygenated with 100% oxygen, 50% oxygen: 50% nitrous oxide or 30% oxygen: 70% nitrous oxide for 1 min. All were then induced with thiopentone, paralysed with suxamethonium and orally intubated. Arterial oxygen saturations were continuously recorded by a separate investigator. All groups showed similar arterial desaturation during suxamethonium-induced apnoea and intubation, but the degree of desaturation was not clinically significant and no patient showed clinical signs of hypoxaemia. Preoxygenation with mixtures of oxygen and nitrous oxide can hasten the build-up of alveolar nitrous oxide concentration and help to smooth induction without compromising oxygenation of patients.

Clinical Value of Pulse Oximetry during Routine Diagnostic and Therapeutic Endoscopic Procedures

The clinical utility of transcutaneous oxygen saturation monitoring during routine diagnostic and therapeutic esophagogastroduodenoscopy and colonoscopy was assessed in 271 consecutive patients. The mean patient age was 56 years (range 14-86 years). The mean preprocedure oxygen saturation was 94% (range 81-100%). The mean dosages of intravenous meperidine, diazepam and midazolam if administered were 50 mg, 6.4 mg and 3.3 mg, respectively. The largest mean decrease in oxygen saturation of all procedures compared to the preprocedure measurement was 3.2% (p = .0001) and occurred immediately after administration of intravenous medication and endoscope intubation. Colonoscopy and esophagogastroduodenoscopy patients experienced similar decreases in oxygen saturation. The patient's age and sex, type of procedure and physician performing the procedure did not affect the degree of desaturation. The largest mean decrease in oxygen saturation observed was less than that considered normal during sleep. The clinical value of transcutaneous oxygen saturation monitoring in routine diagnostic and therapeutic esophagogastroduodenoscopy and colonoscopy is not supported by the findings of this study.

Nocturnal Hypoxemia as a Determinant of Vigilance Impairment in Sleep Apnea Syndrome

In sleep apnea syndrome (SAS), vigilance impairment is typically associated with highly disrupted sleep, but recently, nocturnal hypoxemia has also been identified as a second pathogenetic factor in patients with a high degree of desaturation. However, although sleep disruption has been demonstrated to play a role in both the propensity to fall asleep and the capacity to stay awake, the role of nocturnal hypoxemia has been implicated only in the latter. In the present study, both sleep disruption and nocturnal hypoxemia were assessed in 20 moderately to severely apneic patients. During the day, vigilance was assessed both by the multiple sleep latency test (MSLT), as a measure of the propensity to fall asleep, and by the four-choice reaction time test (FCRTT), as a measure of the capacity to stay awake in a performance task. Severity of nocturnal hypoxemia was found to predict performance on the MSLT, as well as on the FCRTT, but sleep disruption was found to predict performance only on the FCRTT. These results suggest that in moderately to severely affected SAS patients, nocturnal hypoxemia may play a primary role in the pathogenesis of vigilance impairment.

A Single-blind Study of Combined Pulse Oximetry and Capnography in Children

This single-blind study examined four levels of monitoring in 402 pediatric cases. Patients were randomly assigned to one of four groups: 1) oximeter and capnograph; 2) only oximeter; 3) only capnograph; or 4) neither oximeter nor capnograph data available to the anesthesia team. An anesthesiologist, not involved in patient care, observed all cases and continuously recorded hemoglobin oxygen saturation (Spo2), ECG, expired CO2, and the oximeter plethysmographic output. Mean age, weight, ASA physical status, airway management (mask or endotracheal tube), and anesthetic technique were similar in each group. Two-hundred sixty problems were documented in 153 patients. Fifty-nine events in 43 patients resulted in "major" desaturation (Spo2 less than or equal to 85% for greater than or equal to 30 s). Fifteen "major" capnograph events (esophageal intubation, disconnection, accidental extubation, or obstructed endotracheal tube) were observed in 11 patients; 8 of these also developed varying degrees of desaturation. One-hundred thirty "minor" desaturation events (Spo2 less than or equal to 95% for greater than 60 s) and 79 "minor" desaturation events (hypercarbaria or hypocarbia) were observed. A number of problems fulfilled criteria in multiple categories. Infants less than or equal to 6 months of age had the highest incidence of major desaturation events (18 of 65 [27%]) compared to toddlers 7-24 months of age or children greater than 24 months of age (P less than 0.001). Blinding the oximeter data increased the number of patients (12 vs. 31) experiencing major desaturation events (P = 0.003); blinding the capnograph data altered neither the frequency of desaturation events nor the incidence of major capnograph events.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in soil properties under intermittent water application

A simple laboratory method was developed to measure changes in saturated hydraulic conductivity and bulk density as affected by intermittent saturating and draining of soil columns. Significant changes in soil properties were measured after intermittent wetting and draining. Laboratory experiments showed significant changes in bulk density and saturated hydraulic conductivity of soil samples during drainage period following saturation of initially dried samples. The rate of changes in soil properties during the drainage period was a function of soil type and degree of desaturation. The effect of intermittent application of water in reducing the soil hydraulic conductivity and subsequently the infiltration rate was verified in the field by measuring the changes in soil intake rate during intermittent (Surge-flow) irrigation.

Periodic breathing at high altitude and ventilatory responses to O2 and CO2.

To determine the relationship between periodic breathing (PB) during sleep at high altitude and ventilatory chemosensitivities, we studied nine Japanese climbers who participated in the expedition to the Kunlun Mountains (7,167 m) in China in 1986. At sea level, ventilatory response to hypoxia (HVR) by isocapnic progressive hypoxia test and to hypercapnia (HCVR) by Read's method were examined. At altitude 5,360 m, respiratory movements of the chest and abdominal wall, SaO2, ECG, and HR were monitored. Seven climbers manifested PB during sleep. There was a significant correlation between PB during sleep and HVR and HCVR (p less than 0.05). All the climbers showed severe desaturation during sleep. There was a significant negative correlation between degree of desaturation during sleep and HVR (p less than 0.05). A negative correlation was also detected between PB and the degree of desaturation during sleep. We concluded that ventilatory chemosensitivities play an important role in eliciting PB and that climbers with high HVR can maintain their arterial oxygenation during sleep, due to hyperventilation induced by PB, which is considered an advantageous adaptation for lowland sojourners.

睡眠時無呼吸症候群の診断

For diagnosis of sleep apnea syndrome (SAS), there are three important steps wihch we have to consider. As the first step, we have to derive the following clinical symptoms from repeated questioning of patients and their families, for example, snoring, morning headache, daytime sleepiness, general fatigue, dyspnea, abnormal behavior during sleep or nocturnal enuresis, etc. Furthermore, we have to consider background diseases and complications. As the second step, it is necessary to take a screening test for patients, who are thought to have breathing disorders of sleep. We have developed a home sleep monitoring system which is very useful for a screening test. Home sleep monitor is consisted of two thermisters for mouth and nasal flow, a microphone for tracheal sound, three electrodes for electrocardiogram, amplifiers and microcomputer. The weight of this device is 280g. This device is equipped just before patient goes to bed, and brought back to hospital on the following day. Data such as trend display of apnea episodes, histogram of apnea episodes or trend display of heart rate are analyzed by a personal computer. As the third step, patient who is suspected of SAS by a screening test needs polysomnography to get correct diagnosis for SAS after admission to hospital. By polysomnography, we can obtain the informations of sleep stage, apnea type, degree of desaturation or hemodynamics during sleep.

Salt marsh hydrology: Implications for biogeochemical fluxes to the atmosphere and estuaries

Rates of gas emissions and solute fluxes from salt marsh sediments are influenced by sediment hydrology. A comprehensive water balance study in a New England salt marsh reveals that evapotranspiration and infiltration during tidal inundation and precipitation are the dominant hydrological processes in the sediment on a marsh‐wide scale. Water loss by drainage through the sediment into tidal creeks is effectively limited to within 10 m to 15 m of the creek bank; however, drainage is responsible for 40% of the water loss within 10 m of the creek during nonflooding, neap tide periods. The rate and extent of advective transport by pore water drainage is controlled by the topography of the marsh surface. Tidal fluctuations in creek level drive larger, oscillating water fluxes across the creek bank, which results in a dispersive transport of the solutes in the sediment, but these fluxes are attenuated in the first meter. Convexities in the marsh surface, for example, the crests of the creek banks, are the location of maximum water loss by drainage and probably the highest degree of desaturation and aeration, which can, in turn, increase gas emissions locally. The spring‐neap tide cycle modulates wetting and drying of the sediment and, by inference, gas emissions in the interior of the marsh. The limited extent of solute transport by drainage implies that an as yet undescribed mechanism is responsible for controlling the concentration of conservative solutes in salt marshes.