[Medical treatment of snoring and obstructive sleep apnea syndrome]

Although snoring may have deleterious effects by itself, its only clearly identified hazard is that of a social nuisance; therefore, treatment of snoring should before all make no harm. Conversely, the potential hazards of obstructive sleep apnea are well established, and it is clearly important to eliminiate sleep apneas. The medical treatments which may improve snoring and obstructive sleep apneas are basically the same. They include avoidance of risk factors such as obesity, alcohol and hypnotics as well as active treatments such as positional treatment, dental appliances and by nasal continuous positive airway pressure. Nasal continuous positive airway pressure has become the treatment of choice for obstructive sleep apnoea, since it is both efficient and safe. Its only limitation is related to variable acceptance by patients.

Pulmonary hypertension in the obstructive sleep apnoea syndrome: prevalence, causes and therapeutic consequences

"Cor pulmonale" is a classic feature of the "Pickwickian syndrome". Earlier studies have reported a high prevalence of pulmonary hypertension (PH) in obstructive sleep apnoea (OSA) patients, but this has not been confirmed by recent studies with a more adequate methodology, including larger groups of patients. The first part of this review is devoted to the prevalence of PH in OSA; most recent studies agree on prevalence of 15-20%. The second (and major) part of the study deals with the causes and mechanisms of PH in OSA. Pulmonary hypertension is rarely observed in the absence of day-time hypoxaemia, and the severity of nocturnal events (apnoea index (AI), apnoea+ hypopnoea index (AHI) does not appear to be the determining factor of PH. Diurnal arterial blood gas disturbances and PH are most often explained by the presence of severe obesity (obesity-hypoventilation syndrome) and, principally, by association of OSA with chronic obstructive pulmonary disease (the so called "overlap syndrome"). Bronchial obstruction is generally of mild-to-moderate degree and may be asymptomatic. The final part of the review analyses the therapeutic consequences of the presence of PH in OSA patients. Pulmonary hypertension, which is generally mild-to-moderate, does not need a specific treatment. When nasal continuous positive airway pressure (CPAP) fails to correct sleep-related hypoxaemia, supplementary oxygen must be administered. In patients with marked daytime hypoxaemia (arterial oxygen tension (Pa,O2), < or = 7.3 kPa (55 mmHg) conventional O2 therapy (nocturnal + diurnal) is required.

Respiratory effort. A factor contributing to sleep propensity in patients with obstructive sleep apnea

To test the hypothesis that respiratory effort during obstructive apneas contributes, together with hypoxemia and sleep fragmentation, to excessive daytime sleepiness, we investigated the relationship between daytime sleepiness and polysomnographic variables in 44 patients with obstructive sleep apnea (OSA). In all patients, daytime sleep propensity was assessed by an 11-item standardized self-questionnaire yielding a sleepiness score and by a modified sleep latency test yielding a mean sleep latency. Respiratory effort during apneas was evaluated by measuring esophageal pressure swings using an esophageal balloon. Within each apneic cycle, we measured the esophageal pressure swings during the first three and the last three occluded efforts during the apnea to define the overall increase, its ratio to apnea duration, and the maximal effort developed during obstruction. In the group of patients as a whole, the sleepiness score was negatively correlated with the mean sleep latency (r=-0.38, p=0.01). The sleepiness score was correlated with the indexes of respiratory effort during apneas (ie, the overall increase, its ratio to apnea duration, and the maximal end-apneic swing in esophageal pressure) and with the apnea+hypopnea index. The mean sleep latency was correlated with all indexes of nocturnal hypoxemia (ie, the mean lowest oxyhemoglobin saturation [SaO2] and the index of apnea associated with a fall in SaO2 below 90% and 80%). We conclude that the degree of respiratory effort during obstructive apneas contributes to self-rated sleep propensity in patients with OSA.

Binding proteins from the antennae of Bombyx mori

From an antennal library of Bombyx mori cDNA clones encoding different binding proteins have been isolated. The deduced amino acid sequences showed only moderate homology to each other but shared several common structural features. Based on a sequence comparison with the antennal binding proteins from different moth species, one of the clones appears to encode a pheromone binding protein, whereas two others represent new members of the two general odorant binding protein families. A fourth clone encodes a protein which is related to antennal binding proteins so far found only in Drosophila melanogaster.

Pulmonary hemodynamics in the obstructive sleep apnea syndrome. Results in 220 consecutive patients

We have investigated pulmonary hemodynamics in a large series of consecutive, unselected patients with obstructive sleep apnea syndrome (OSAS). The aims of this study were to evaluate the frequency of pulmonary artery hypertension (PH) in OSAS and to analyze, as far as possible, its mechanisms. Two hundred twenty patients were included on the basis of a polysomnographic diagnosis of OSAS (apnea+hypopnea index > 20). PH, defined by a resting mean pulmonary artery mean pressure (PAP) of at least 20 mm Hg, was observed in 37 of 220 patients (17%). Patients with PH differed from the others with regard to pulmonary volumes (vital capacity [VC], FEV1) and the FEV1/VC ratio that were significantly lower (p < 0.001); PaO2 (64.4 +/- 9.3 vs 74.7 +/- 10.1 mm Hg; p < 0.001); PaCO2 (43.8 +/- 5.4 vs 37.6 +/- 3.9 mm Hg; p < 0.001), apnea+hypopnea index (100 +/- 33 vs 74 +/- 32; p < 0.001), and mean nocturnal arterial oxygen saturation (SaO2) (88 +/- 6% vs 94 +/- 2%; p < 0.001). Patients with PH were also more overweight (p < 0.001). Multiple regression analysis showed that 50% of the variance of PAP could be predicted by an equation including PaCO2 (accounting for 32% of the variance), FEV1 (12%), airway resistance (4%), and mean nocturnal SaO2 (2%). In conclusion, PH is observed, in agreement with previous studies, in less than 20% of OSAS patients. PH is strongly linked to the presence of an obstructive (rather than restrictive) ventilatory pattern, hypoxemia, and hypercapnia, and is generally accounted for by an associated obstructive airways disease. In this regard, the severity of OSAS plays only a minor role.

[Propensity for sleep and diurnal somnolence in the course of sleep apnea syndrome]

Daytime sleepiness is one of the major symptoms of obstructive sleep apnea. However, its definition raises problems, since it may be based on either subjective feeling (evaluated by means of questionnaires or analog visual scales), physiological drive or need (inferred by a sleep latency) or on the concept of sleep propensity defined as the probability of falling asleep (measured by the occurrence of sleep in various circumstances of daily life). Data from the literature suggest that sleep fragmentation and hypoxemia, both related to sleep apneas, cause daytime sleepiness. Our own data show that sleep propensity in a group of 44 patients with obstructive sleep apnea was correlated with the increase in esophageal pressure swings during obstructive apneas. This result suggests that the increased respiratory effort against occluded upper airways also contributes to daytime sleepiness in patients with obstructive sleep apnea.

Two classes of olfactory receptors in Xenopus laevis

Xenopus laevis possess a gene repertoire encoding two distinct classes of olfactory receptors: one class related to receptors of fish and one class similar to receptors of mammals. Sequence comparison indicates that the fish-like receptors represent closely related members of only two subfamilies, whereas mammalian-like receptors are more distantly related, most of them representing a different subfamily. The fish-like receptor genes are exclusively expressed in the lateral diverticulum of the frog's nose, specialized for detecting water-soluble odorants, whereas mammalian-like receptors are expressed in sensory neurons of the main diverticulum, responsible for the reception of volatile odors.

Determinants of effective continuous positive airway pressure in obstructive sleep apnea. Role of respiratory effort

We investigated whether cephalometric measurements, nocturnal indices of negative intrathoracic pressure, or the frequency of sleep-related breathing disorders were related to the level of effective continuous positive airway pressure (CPAP) in patients with obstructive sleep apnea (OSA). We examined 22 OSA patients who underwent two consecutive polysomnographic recordings, the first for diagnosis and the second for CPAP titration. Cephalometric measurements, spirometric data, and blood-gas analysis results were available for all subjects. In the diagnostic polysomnography, at least 30 apneas were analyzed during non-rapid-eye-movement (NREM) sleep and 10 apneas during rapid eye movement (REM) sleep for each patient. Swings in esophageal pressure (Pes) during the preapneic period and during the beginning and the end of obstructive apneas were calculated as the average of three consecutive breaths (or ineffective efforts). The difference in Pes from the minimal initial to the maximal final apneic respiratory effort (DPes) and the rate of increase in Pes (RPes = DPes/apnea duration) during apnea were computed. Within an apnea, the lowest Pes always occurred during the first three occluded breaths and the highest during the last three, with a more marked difference in NREM sleep. The level of effective CPAP was correlated with the length of the soft palate (r = 0.69, p = 0.000), RPes (r = 0.55, p = 0.008), and DPes (r = 0.49, p = 0.02). The correlations of effective CPAP level with body mass index and apnea + hypopnea index were not significant. A model including length of the uvula, DPes, and RPes accounted for 56 to 59% of the variability in effective CPAP.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of plasma volume during obstructive sleep apnoea

The evidence that plasma volume is altered in obstructive sleep apnoea is an indirect one, based on the observation of a paradoxical elimination of peripheral oedema along with a decrease in water and sodium excretion and of a decrease in haematocrit when apnoeas are eliminated with continuous positive airway pressure (CPAP) treatment. A suggested interpretation of these observations is that in the untreated condition, increased renal sodium excretion and increased vascular membrane permeability lead to increased urine and salt excretion and to a fluid shift from the plasma to the extracellular space, causing nocturnal polyuria, peripheral oedema and haemoconcentration. Treatment with continuous positive airway pressure reverses the increased membrane permeability and urine excretion, allowing the peripheral oedema to resolve and the haematocrit to decrease. Increased atrial natriuretic peptide release and decreased renin-angiotensin-aldosterone activity, along with an increased release of thromboxane and of endothelin (which have been reported in untreated obstructive sleep apnoea), could be the mechanisms of the observed alterations in fluid distribution in obstructive sleep apnoea.

[Sleep and COPD]

In COPD patients hypoxaemia does worsen during sleep and particularly during REM sleep. However, severe sleep-related O2 desaturation is only observed in patients who exhibit a marked daytime hypoxaemia. Nocturnal desaturation is due to the combination of alveolar hypoventilation and ventilation-perfusion mismatch; alveolar hypoventilation is the predominant mechanism, at least during REM sleep. Sleep-related hypoxaemia leads to peaks of pulmonary hypertension but also to cardiac arrhythmias. Hypoxaemia can be particularly severe when COPD is associated with a sleep apnoea syndrome (this association is rather frequent). A severe nocturnal desaturation needs a treatment with prolonged oxygen therapy, especially if daytime hypoxaemia (PaO2 < 55-60 mmHg) is present. The real benefit from oxygen therapy limited to sleep time in nocturnal desaturators who have not a significant daytime hypoxaemia, has not been yet demonstrated.

Prolactin secretion during sleep in obstructive sleep apnoea patients

Plasma prolactin (PRL) concentration exhibits a sleep-dependent pattern, with highest levels during sleep and lowest levels during the waking period. The syndrome of obstructive sleep apnoea (OSA) is associated with severe hypoxaemia and chronic sleep fragmentation, both of which could affect the sleep-entrained PRL rhythm. Treatment with nasal continuous positive airway pressure (CPAP) immediately restores a normal sleep structure by successful abolition of the apnoeas. In the present study, seven OSA patients underwent two night studies, once when no treatment was given and once during the first night of CPAP treatment. Sleep was recorded polygraphically in all experiments. Plasma PRL was measured at 10 min intervals and secretory rates were calculated by a deconvolution procedure. CPAP treatment greatly reduced hypoxaemia and improved sleep quality. The secretory pulse amplitude and the total amount of PRL secreted during the night remained constant regardless of whether patients were treated or not. The only difference found was a lower pulse frequency in untreated OSA patients as compared to treated patients, which may be attributed either to hypoxaemia or to sleep disturbance or to the combined action of both. Treatment may be considered to normalize PRL release by restoring pulse frequency to values similar to those observed for normal subjects.

Association of chronic obstructive pulmonary disease and sleep apnea syndrome

The association of chronic obstructive pulmonary disease (COPD) and sleep apnea syndrome (SAS), which are both frequent diseases, is likely to occur in a number of patients. We have prospectively investigated a large series (n = 265) of patients who were selected solely on the basis of a confirmed diagnosis of SAS (apnea + hypopnea index > 20/hr). An obstructive spirographic pattern, defined by an FEV1/VC ratio < or = 60%, was observed in 30 of 265 patients (11%). These patients (subgroup "overlap") were older (58 +/- 9) versus 53 +/- 10 yr, p = 0.01) than the remainder of the study population, and all were male patients. Body mass index (BMI) was identical in overlap patients to that in the remainder. Vital capacity and FEV1 were lower, by definition, in the overlap group. PaO2 was lower (66 +/- 10 versus 74 +/- 10 mm Hg, p < 0.001) and PaCO2 higher (42 +/- 6 versus 38 +/- 4 mm Hg, p < 0.001) in the overlap group. Hypoxemia (Pao2, < or = 65 mm Hg) was observed in 17 of 30 overlap patients and in 54 of 235 of the remainder. Hypercapnia (Paco2 > or = 45 mm Hg) was observed in 8 of 30 overlap patients and in 19 of 235 of the remainder. The pulmonary artery mean pressure (PAP) was higher in overlap patients both at rest (20 +/- 6 versus 15 +/- 5 mm Hg, p < 0.01) and during steady-state exercise (37 +/- 12 versus 29 +/- 10 mm Hg, p = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Probing olfactory receptors with sequence-specific antibodies

Molecular cloning has revealed the structure of several putative odorant receptors. Chemically synthesized peptides, that correspond to a predicted extracellular domain of the encoded proteins, were employed to generate receptor-specific antibodies. Immunohistological approaches as well as Western-blot analysis confirmed the specificity of the antipeptide sera. Furthermore, deglycosylation experiments explained the observed discrepancy between the molecular mass of odorant receptors, as determined by SDS/PAGE and Western-blot analysis of ciliary proteins (M(r) 50,000), and the predicted protein size based on the deduced primary structure from cloned receptor genes (M(r) 30,000-35,000). Receptor proteins become phosphorylated upon odorant stimulation of olfactory cilia preparations; this was demonstrated by immunoprecipitation experiments employing the sequence-directed, receptor-specific antibodies. Functional assays revealed that the receptor-specific antibodies significantly attenuate second messenger signalling elicited by inositol 1,4,5-trisphosphate-inducing odorants, whereas activation of the cAMP cascade by appropriate odorants was not affected. These observation indicate that the sequence-specific antibodies not only recognize odorant receptors, but also discriminate between receptor subtypes coupling to different second-messenger pathways.

Evaluation of oral rehydration therapy in Matiguas, Nicaragua

Use of oral rehydration salts is an effective tool to decrease deaths due to diarrheal dehydration. Following concerted educational efforts to introduce oral rehydration therapy, Nicaragua reported a significant decrease in deaths of young children from diarrhea and dehydration over a 5-year period. Further decline in the mortality rate has not occurred, however, and factors that would affect usage and impact are poorly understood. A health survey was administered in 155 randomly selected homes in Matiguas, Nicaragua, in July 1990. Caretakers of children were asked about their knowledge, attitudes, and practices in treating diarrhea in children younger than age 5. They were also asked to demonstrate their knowledge of mixing World Health Organization oral rehydration salts packets. Ninety percent of the respondents said they used oral rehydration therapy. The major reason quoted for not using it was dislike of the taste. Of the three-quarters willing to mix the oral rehydration salts, 62 percent prepared the solution correctly and 38 percent incorrectly. Knowledge about diarrhea and the role of oral rehydration therapy was high in this population, and those with this knowledge were more likely to use it. Respondents who learned to mix the oral rehydration salts at the health center had more years of education and were more likely to mix the salts correctly. In this study, there is a positive association between contact with the health center and correct use of the rehydration salts. The relationship of this association with morbidity and mortality needs further research.

[Sleep apneas]

In its most frequent form, in which obstructive apneas are predominant, the sleep apnea syndrome appears more and more as a frequent disorder. Clinically, it can be easily suspected in a patient presenting with snoring and daytime sleepiness, provided that these symptoms are systematically sought. A firm diagnosis relies on polysomnographic recordings. Beyond these symptoms, which are social and professional handicaps, the severity of the disorder is related to its cardiovascular long-term complications. The standard treatment is based upon nasal continuous positive airway pressure, which is safe and efficient but constraining. Surgical treatments, which are not as safe nor as efficient, can be proposed when continuous positive airway pressure is not accepted.

Continuous positive airway pressure treatment. Effects on growth hormone, insulin and glucose profiles in obstructive sleep apnea patients

The principal nocturnal GH peak normally coincides with the first episode of slow wave sleep (SWS). Obstructive sleep apnea (OSA) patients have low nocturnal GH levels which may be explained by their poor quality fragmented sleep but other factors are possibly involved. Obesity is frequently associated with OSA, and obese patients also manifest reduced GH secretion. The mechanisms reducing GH levels in obese subjects are not understood, but hyperinsulinaemia is a suggested factor. In this study nocturnal plasma and secretory GH profiles of OSA patients were examined in relation to the quality and quantity of sleep, together with plasma glucose and insulin levels. Eight OSA patients, (BMI 32.7 +/- 2.3 kg/m2), underwent 2 night studies. For one night no treatment was given and for the other continuous positive airway pressure (CPAP) treatment was administered for the first time. Blood was collected continuously throughout each night and plasma GH, insulin and glucose profiles established in 10 min interval samples. From the plasma data a deconvolution model was used to calculate GH secretion rates. Sleep was recorded during the studies. For the non-treatment night GH levels were low and increased significantly with treatment, p = 0.008 for plasma levels and p = 0.02 for secretion rates. Treatment significantly decreased the cumulative apnea duration and increased the quantity of SWS and Rapid Eye Movement (REM) sleep (p = 0.008), but the mean insulin and glucose profiles did not differ between the two nights. Individual GH plasma and secretion rates, on treatment, showed a tendency to correlate with the amount of SWS (p = 0.09).(ABSTRACT TRUNCATED AT 250 WORDS)

Odorant binding proteins of Heliothis virescens

cDNA clones coding for three different binding proteins were isolated from an antennal library of Heliothis virescens. The deduced amino acid sequences showed only moderate homology to each other but shared several common structural features. Based on a comparison with the predicted primary structures of antennal binding proteins from different moth species, one of the clones (Hel-1) was found to encode a pheromone binding protein, whereas the two others (Hel-10 and -11) encode general odorant binding proteins.