Pharyngeal critical pressure in patients with obstructive sleep apnea syndrome. Clinical implications

Current evidence suggests that patients with obstructive sleep apnea (OSA) may have greater pharyngeal critical pressure (Pcrit), which reflects the increase in upper airway collapsibility. The contribution of Pcrit to the severity of OSA and to the efficacious continuous positive pressure (nCPAPeff) therapy has never been extensively described and no data are available about the interaction of Pcrit, age, and anthropometric variables. To determine the relationship between Pcrit, severity of the disease, nCPAPeff, and anthropometric variables we measured Pcrit in a group of 106 patients with OSA. Pharyngeal critical pressure was derived from the relationship between maximal inspiratory flow and nasal pressure, Pcrit representing the extrapolated pressure at zero flow. Upper airway resistance (Rus) was determined as the reciprocal of the slope (DeltaPn/DeltaVImax cm H2O/L/s) in the regression equation. In a subgroup of 68 patients, during the diagnostic night, we measured as indices of respiratory effort, the maximal inspiratory esophageal pressure (Pes) at the end of apnea (Pesmax), the overall increase from the minimum to the maximum (DeltaPes), and the rate of increase of Pes during apnea (RPes). As a group, the mean Pcrit was 2.09 +/- 0.1 cm H2O (range, 0 to 4.5) and the mean Rus was 11.1 +/- 0.5 cm H2O/L/s. Although men have greater Pcrit, pharyngeal collapsibility was influenced neither by neck size nor by body mass index (BMI). Although there was a significant relationship between Pcrit and apnea plus hypopnea index (AHI) (r = 0.23, p = 0.02), neck circumference was the stronger predictor of apnea frequency, with Pcrit contributing only to the 3% of the variance. In the group of patients as a whole, a model including AHI, BMI, Rus, and Pcrit explained the 36% of the variance in nCPAPeff, with a greater contribution of AHI, Pcrit accounting for only 3% of the variation. In patients for whom the measure of respiratory effort was obtained, 42% of the variance in nCPAPeff was explained by RPes (33%) and BMI. From these results we conclude that Pcrit alone does not yield a diagnostically accurate estimation of OSA severity and nCPAPeff. Although individual collapsibility may predispose to pharyngeal collapse, upper airway occlusion may require the combination of several factors, including obesity, upper airway structure, and abnormalities in muscle control.     

Effect of tracheal and tongue displacement on upper airway airflow dynamics

We have previously shown that caudal tracheal displacement alters the airflow dynamics of the upper airway. In the present study, we specifically examined the effects of tongue and tracheal displacement on upper airway airflow dynamics. To determine how tongue and tracheal displacement modulate maximal inspiratory airflow (VImax), we analyzed the pressure-flow relationships obtained in the isolated upper airway of paralyzed cats. VImax and its determinants, the pharyngeal critical pressure (Pcrit) and the nasal resistance (Rn) upstream to the flow-limiting site, were measured as tongue displacement and tracheal displacement were systematically varied. Four results were obtained: 1) there was no independent effect of tongue displacement on VImax, Pcrit, or Rn; 2) there was an increase in VImax with 2 cm of tracheal displacement, which was associated with a decrease in Pcrit and an increase in Rn; 3) there was an interactive effect of tongue and tracheal displacement on VImax and Pcrit but not on Rn; and 4) there was a large increase in VImax with tongue displacement > 2.5 cm with the trachea nondisplaced, which was associated with a large decrease in Pcrit and a large increase in Rn. We conclude that tongue and tracheal displacement exert differing influences on airflow dynamics and present a mechanical model of the upper airway that explains these results.     

Digital fluoroscopy before and after laser uvulopalatopharyngoplasty in obstructive sleep apnea. Importance of pharyngeal collapsibility and hyoid bone position

PURPOSE: To study the changes in pharyngeal behavior after laser uvulopalatopharyhgoplasty (LUPPP). MATERIAL AND METHODS: The dynamic changes in the upper airway size were evaluated with digital fluoroscopy in 24 patients with obstructive sleep apnea (OSA) before and after LUPPP and in 16 normal controls, while they were awake and breathing normally. Cephalometric measurements were also made. The patients were classified into the categories of good and poor responders by means of a static-charge-sensitive bed. RESULTS: Following LUPPP, collapsibility at the velopharyngeal level was within the normal range m 15 of 17 good responders, but only in 2 of 7 poor responders (p = 0.0086). The minimum airway size at the same level showed a similar trend. In 3 of 7 poor responders the hyoid bone was positioned more caudally than in the good responders (p = 0.017). CONCLUSION: Digital fluoroscopy provides information on the change in upper airway behavior after LUPPP.     

State-related changes in upper airway caliber and surrounding soft-tissue structures in normal subjects

State-dependent changes in upper airway caliber were studied with magnetic resonance imaging (MRI) techniques. We hypothesized that changes in airway caliber during sleep in normal subjects would result from positional and dimensional changes in upper airway soft-tissue structures, including the lateral pharyngeal walls, tongue, and soft palate. We used MRI to study 15 normal subjects during wakefulness and sleep. Sleep was facilitated by one night of sleep deprivation prior to MRI. During sleep, the volume of the retropalatal (RP) airway was reduced by 19% (p = 0.03). The volume of the retroglossal (RG) airway was not significantly reduced during sleep, suggesting that the RP region may be more likely to collapse. The mean minimal cross-sectional airway area was reduced by 228% (p = 0.004) in the RP and by 22% (p = 0.02) in the RG region during sleep as compared with values in anatomically matched axial images during wakefulness. Airway anteroposterior (AP) and lateral dimensions were also significantly reduced in the RP region. Airway narrowing in the RP region was associated with a 7% increase in thickness of the lateral pharyngeal walls (p = 0.04). In nine subjects, sagittal data showed significant posterior displacement of the soft palate during sleep as compared with wakefulness. Multiple linear regression analyses indicated that reduction in the RP airway area during sleep resulted from posterior movement of the soft palate, thickening of the lateral pharyngeal walls, and an increase in tongue oblique distance. We conclude that the lateral pharyngeal walls play an important role in upper airway narrowing during sleep in normal subjects.     

Histological indications of a progressive snorers disease in an upper airway muscle

The etiology of upper airway collapsibility in patients with snoring and obstructive sleep apnea (OSA) remains unclear. Local muscular abnormalities, including neurogenic lesions, could be a contributory factor. The aim of this study was to histologically evaluate the hypothesis of a progressive snorers disease. Biopsies of palatopharyngeal muscle were obtained from 21 patients with habitual snoring and different degrees of upper airway obstruction (10 patients with OSA) and 10 nonsnoring control subjects. Morphological abnormalities, including neurogenic signs (e.g., type grouping), were blindly quantified. The degree of abnormality was significantly increased in patients compared with control subjects. The individual score of abnormalities was significantly correlated to the percentage periodic obstructive breathing but not to oxygen desaturation index. Analyses of the individual fiber-size spectra demonstrated a significantly increased number of hypertrophied and/or atrophied fibers in patients compared with controls. The subjects were also divided into three groups according to their type of nocturnal breathing, i.e., nonsnorers, patients with < 20%, and patients with > or = 45% obstructive breathing. These groups correlated significantly with the degree of abnormality and pathological fiber-size spectra. In conclusion, these results support the hypothesis of a progressive local neurogenic lesion, caused by the trauma of snoring, as a possible contributory factor to upper airway collapsibility.     

Starling resister and stability of sleep ventilation

The upper airway can be described as a collapsible segment (the pharynx) interposed between two rigid bony (the cavum) or cartilaginous (the trachea) segments. Due to this structure, the pharynx behaves as a collapsible tube, in which airflow does not depend on the downstream pressure, but is limited to a maximum value which depends only on the upstream pressure and on the pressure surrounding the collapsible segment; this behavior, known as a Starling resistor can be modeled by the waterfall effect. Thus, the upper airways can be in three different conditions: an occluded condition, in which no flow is possible, a patent condition, in which flow depends on the difference between upstream and downstream pressures (according to Poiseuille's law), and a situation in which flow is limited. The behavior of the upper airway is largely dependent on its anatomic structure, but functional factors play a critical role. Among these sleep state is both a determinant of the collapsibility of the pharynx, and determined by the simulation of upper airway mechanoreceptors whose activity depends on the activity of respiratory muscles. Thus the interplay of three factors: ventilatory drive, upper airway collapsibility, and arousal threshold can predict most of the situations of stable and unstable ventilatory behavior during sleep. The level of the arousal threshold governs the stability of the ventilatory pattern, as it determines whether a combination of slow, respiratory effort, and blood gases can be maintained or is interrupted by an arousal.     

Clinical significance of snoring

Habitual snoring, nocturnal apnea, and excessive daytime sleepiness are leading symptoms of the obstructive sleep apnea syndrome. However, simple snoring without apnea is a more common and normal phenomenon. In certain habitual snorers increased upper airway resistance during sleep may lead to sleep fragmentation and hypersomnolence even in the absence of frank apnea; this condition is termed upper airway resistance syndrome. There is no convincing evidence that snoring in the absence of sleep apnea is an independent risk factor for cardiovascular disease. The evaluation of symptomatic snorers includes a specific history and physical exam, followed by a sleep study if treatment is considered necessary. The choice of treatment modality for snoring is guided by the individual needs and symptoms of the patient. Weight loss, nocturnal application of continuous positive airway pressure, or intraoral appliances which hold the mandible in protrusion during sleep are non-surgical treatment options. According to the patients' subjective assessment conventional or laser-assisted uvulo-palato-pharyngoplasty (UPPP) has a high cure rate for snoring. However, objective documentation of the effect of these interventions on measured snoring noise is scant.     

Arousal responses to inspiratory resistive loading during REM and non-REM sleep in normal men after short-term fragmentation/deprivation

The arousal response to inspiratory resistive loading in normal men is known to be high during REM sleep compared to non-REM sleep. We investigated whether we could observe the same pattern, i.e. brisk arousal from REM sleep compared to non-REM sleep, in normal subjects who had undergone short-term sleep fragmentation/deprivation prior to the investigation. The arousal response to the repeated application of an external inspiratory resistance of 25 cm H2O/l/s was determined during REM and non-REM sleep in 10 healthy men after a single night with 4 hours of acoustically fragmented sleep. The percentage of arousals to non-arousals occurring within 2 minutes of the load application was significantly higher during REM sleep than during either of the non-REM sleep stages 2 and 3/4 and decreased significantly from stage REM to stage 2 and from stage 2 to stage 3/4. The mean time to arousal in REM was significantly shorter than in non-REM stage 3/4. The duration of sleep (comparing the results of the first with the second half of the sleep period time) did not modify the arousal response in stages 2 and 3/4. Despite short-term sleep fragmentation/deprivation the night before the study, the arousal response to external inspiratory resistive loading was brisker during REM than non-REM sleep in the healthy subjects studied. The responses were of the same magnitude as those induced in prior studies without pretest sleep disturbance. This is different from what is seen in patients with sleep apnea, where breathing disorders are worst during REM sleep and sleep fragmentation/deprivation leads to rapid deterioration of arousal responses to the spontaneously occurring airway occlusions.     

Indices from flow-volume curves in relation to cephalometric, ENT- and sleep-O2 saturation variables in snorers with and without obstructive sleep-apnoea

In a group of 37 heavy snorers with obstructive sleep apnoea (OSA, Group 1) and a group of 23 heavy snorers without OSA (Group 2) cephalometric indices, ENT indices related to upper airway collapsibility, and nocturnal O2 desaturation indices were related to variables from maximal expiratory and inspiratory flow-volume (MEFV and MIFV) curves. The cephalometric indices used were the length and diameter of the soft palate (spl and spd), the shortest distance between the mandibular plane and the hyoid bone (mph) and the posterior airway space (pas). Collapsibility of the upper airways was observed at the level of the tongue base and soft palate by fibroscopy during a Müller manoeuvre (mtb and msp) and ranked on a five point scale. Sleep indices measured were the mean number of oxygen desaturations of more than 3% per hour preceded by an apnoea or hypopnoea of more than 10 s (desaturation index), maximal sleep oxygen desaturation, baseline arterial oxygen saturation (Sa,O2) and, in the OSA group, percentage of sleep time with Sa,O2 < 90%. The variables obtained from the flow-volume curves were the forced vital capacity (FVC), forced expiratory and inspiratory volume in 1 s (FEV1 and FIV1), peak expiratory and peak inspiratory flows (PEF and PIF), and maximal flow after expiring 50% of the FVC (MEF50). The mean of the flow-volume variables, influenced by upper airway aperture (PEF, FIV1) was significantly greater than predicted.(ABSTRACT TRUNCATED AT 250 WORDS)     

Expandable metallic stent placement in patients with benign esophageal strictures: results of long-term follow-up

Prosthetic mandibular advancement (PMA) was applied to nine patients with obstructive sleep apnea syndrome (OSAS) and its therapeutic usefulness, mechanism of action, and clinical indication were discussed based on polysomnographic findings and serial examination of upper airway before and during PMA treatment. Apnea hypopnea index significantly decreased during PMA treatment compared with the value before treatment (P < 0.01) and the rate of the treatment responder counted 78.1%. Cephalometric variables indicated forward and inferior advancement of mandible in our subjects. Magnetic resonance imaging of the upper airway during sleep revealed a marked improvement of velophanryngeal obstruction in most subjects. In addition, intraesophageal negative pressure during sleep decreased significantly. Our results confirmed the high therapeutic efficacy of PMA for OSAS and indicated forward advancement of the mandible and decrease of negative pressure loading on upper airway with PMA might suppress velopharyngeal collapse. Thus, PMA was regarded as one of the treatments of choice for OSAS occurring based on with velopharyngeal narrowing.     

Upper airway muscle activity during REM and non-REM sleep of patients with obstructive apnea

We measured electromyograms (EMGs) of genioglossus muscle (GG) and inspiratory intercostal muscle (IIM) in both rapid eye movement (REM) sleep and non-REM sleep of 12 patients with obstructive sleep apnea (OSA) to examine the influence of different sleep stages on upper airway muscle activity during sleep apnea. Quantifications of both muscle activities were assessed by their individual peak amplitude of integrated inspiratory EMG. Genioglossus and IIM activities showed a qualitatively similar cyclic change with an alteration of apneic and ventilatory phases during both non-REM and REM sleep. Both muscle activities increased gradually in the late apneic phase and reached each peak at the opening of the upper airway and, subsequently, decreased gradually. There were no significant differences in both muscles activities in either the ventilatory or early apneic phase between non-REM sleep and REM sleep. On the other hand, GG and IIM activities in the late apneic phase during REM sleep were significantly lower than those during non-REM sleep. The relative activity of GG to IIM in the late apneic phase was significantly lower during REM sleep than that during non-REM sleep. These results indicate that upper airway and intercostal muscle activation in the later apneic phase during REM sleep were inhibited compared with those during non-REM sleep and that this inhibition was observed predominantly in upper airway muscles.     

Absence of tonic electromyographic activity during sleep in normal and spastic nonmimetic skeletal muscles in man

An electromyographic study of nonmimetic skeletal muscles was carried out in 8 normal adults and 4 patients with spastic hemiparesis during all stages of sleep for a total of 21 nights. All normal subjects showed absence of tonic electromyographic activity in all nonmimetic skeletal muscles in all stages of sleep. Also, during quiet, relaxed wakefulness, tonic muscle discharges disappeared in the normal subjects. Three patients with upper motor neuron spasticity demonstrated results during sleep similar to those obtained in the normal subjects. In the fourth patient, tonic muscle discharges persisted into stage 2 non-REM sleep, disappeared within 30 to 240 seconds following the onset of stage 2 sleep, and were absent during stages 3 and 4 sleep and REM sleep.     

Effect of pharmacokinetic sampling methods on aminoglycoside dosing in critically ill surgery patients

BACKGROUND: Airway obstruction after anesthesia may be caused or exaggerated by residual neuromuscular block, with loss of muscle support for collapsible upper airway structures. METHODS: Six male volunteers were studied before treatment, during stable partial neuromuscular block with vecuronium at a mean train-of-four (TOF) ratio of 50% (95% CI, 36-61%), and after reversal by neostigmine. Catheter-mounted transducers were placed in the pharynx and esophagus to estimate, respectively, the upper airway resistance, and the work of breathing (calculated as the time integral of the inspiratory pressure developed by the respiratory muscles, esophageal pressure time product) during quiet breathing, during breathing 5% carbon dioxide, and while breathing with an inspiratory resistor. Breathing with pressure at the airway opening held at pressures from -5 to 40 cm H2O were also tested to assess airway collapsibility. RESULTS: Although breathing through a resistor increased upper airway resistance from 1.2 (0.67, 1.72) cm H2O x l(-1) x s to 2.5 (1.32, 3.38) cm H2O x l(-1) x s, and carbon dioxide stimulation reduced resistance to 0.8 (0.46, 1.33) cm H2O x l(-1) x s, no effect of partial neuromuscular block (mean TOF ratio, 52%) on upper airway properties could be shown. CONCLUSIONS: Neuromuscular block with a TOF ratio of 50% can be present yet clinically difficult to detect in patients recovering from anesthesia. This degree of block has no effect on airway patency in volunteers, even during challenge. Airway obstruction during recovery from anesthesia thus is more likely to be caused by residual effects of general anesthetic agents or centrally acting analgesics, either alone or perhaps in concert with residual neuromuscular block.     

Ventilatory dynamics during transient arousal from NREM sleep: implications for respiratory control stability

The polysomnographic and ventilatory patterns of nine normal adults were measured during non-rapid-eye-movement (NREM) stage 2 sleep before and after repeated administrations of a tone (40-72 dB) lasting 5 s. The ventilatory response to arousal (VRA) was determined in data sections showing electrocortical arousal following the start of the tone. Mean inspiratory flow and tidal volume increased significantly above control levels in the first seven breaths after the start of arousal, with peak increases (64.2% > control) occurring on the second breath. Breath-to-breath occlusion pressure 100 ms after the start of inspiration showed significant increases only on the second and third postarousal breaths, whereas upper airway resistance declined immediately and remained below control for > or = 7 consecutive breaths. These results suggest that the first breath and latter portion of the VRA are determined more by upper airway dynamics than by changes in the neural drive to breathe. Computer model simulations comparing different VRA time courses show that sustained periodic apnea is more likely to occur when the fall in the postarousal increase in ventilation is more abrupt.     

Abnormal twenty-four hour pattern of pulsatile luteinizing hormone secretion and the response to naloxone in women with hyperprolactinaemic amenorrhoea

OBJECTIVE: Hyperprolactinaemic amenorrhoea is associated with disturbances of pulsatile gonadotrophin secretion. The underlying mechanism remains unclear and the aim of this study was to investigate the 24-hour secretory pattern of gonadotrophins in women with hyperprolactinaemic amenorrhoea. The effect of opioid blockade using naloxone infusion on LH secretory pattern was also studied. DESIGN: The secretory patterns of LH, FSH, PRL and their responses to naloxone infusion were studied by serial blood samples collected at 10-minute intervals for 24 hours. On the following day, naloxone was infused at a dose of 1.6 mg per hour for 4 hours. PATIENTS: Eight women with hyperprolactinaemic amenorrhoea, two women hyperprolactinaemic but with normal ovarian cycles, and nine control subjects in the early follicular phase of menstrual cycle. MEASUREMENTS: Concentrations of LH, FSH and PRL were measured in plasma samples obtained at 10-minute intervals for 24 hours. In one woman, concentrations of urinary oestrone glucuronide were measured daily during treatment with pulsatile GnRH. RESULTS: The number of LH pulses per 24 hours was significantly fewer in women with hyperprolactinaemic amenorrhoea than in those with hyperprolactinaemia with normal cycles or control subjects (mean +/- SEM 4.5 +/- 2.4 vs 13.5 +/- 2.5 vs 17.3 +/- 0.8, P < 0.001). The magnitude of each episode of secretion was significantly higher in the hyperprolactinaemic amenorrhoeic women (P < 0.05) so the overall mean concentrations of LH throughout the 24-hour period was similar in the three groups (5.2 +/- 1.1, 4.8 +/- 0.8 and 5.2 +/- 0.4 U/l respectively). In women with hyperprolactinaemic amenorrhoea there was no significant change in the pattern of LH secretion during sleep in contrast to the control women in whom there was a slowing in the LH pulse frequency during the night. There was no significant change in the mean concentrations of LH, FSH and PRL during the naloxone infusion. There were also no significant changes in the LH pulse frequency in response to naloxone infusion when compared with an equivalent period of time in the previous 24 hours. In one hyperprolactinaemic amenorrhoeic woman, follicular development, ovulation and pregnancy were induced when gonadotrophin releasing hormone (GnRH) was infused in a pulsatile manner at a dose of 5 micrograms every 90 minutes. CONCLUSIONS: The suppression of normal ovarian cycles in women with hyperprolactinaemic amenorrhoea is due to a significant reduction in frequency of LH (GnRH) secretion which is not due to an increase in hypothalamic opioid activity. As normal ovarian cycles can occur or be induced by exogenous GnRH in hyperprolactinaemia, it is unlikely that a high level of prolactin by itself inhibits follicular development and ovulation.     

Effects of 24-hr nicotine replacement on sleep and daytime activity during smoking cessation

BACKGROUND: This study uses wrist actigrapy to assess the effects of 24-hr transdermal nicotine replacement on the sleep and daytime activity of smokers during smoking cessation. METHODS: Seventy-one subjects grouped as light (n = 23), moderate (n = 24), or heavy (n = 24) smokers were randomly assigned to placebo or 11, 22, or 44 mg/day doses of transdermal nicotine for 1 week of intensive inpatient treatment of nicotine dependence. Outpatient patch therapy continued for 7 weeks following the inpatient stay. Those initially on placebo were randomly assigned to 11 or 22 mg/day, and those initially on 44 mg/day were reduced to 22 mg/day at Week 4. RESULTS: There was a significant decrease in daytime wrist activity during patch therapy and the 1st week off patch therapy. These changes in daytime wrist activity were positively correlated with percentage of nicotine and cotinine replacement. No changes from baseline in sleep (sleep efficiency or wrist activity) were detected, nor were there differences in sleep among the four patch doses. CONCLUSIONS: Using wrist actigraphy, this study failed to show any disturbing effects of 24-hr high-dose nicotine replacement on sleep. Lower levels of nicotine replacement were associated with a decrease from baseline in daytime wrist activity.     

Effects of sleeping in a chemical protective mask on sleep quality and cognitive performance

PURPOSE: We wanted to determine whether sleep is disrupted when soldiers sleep in a new chemical protective mask, the M40. Sleep quantity and quality, extent of protection provided by the mask during sleep, and next day performance were assessed. METHOD: After several days of training, 9 male soldiers slept with and without the M40 mask on four occasions. RESULTS: Soldiers were able to tolerate the mask for most or all of the night. However, sleep, as assessed by wrist-worn activity monitors, was significantly disturbed. Minutes (mean +/- SEM) of waking significantly increased, from 25 +/- 2.1 to 86 +/- 8.5 per night (p < 0.001), and number of awakenings rose from 8 +/- 0.6 to 20 +/- 0.9 (p < 0.0001). Soldiers reported that it took longer and was more difficult to fall asleep when wearing the mask. Errors on a choice reaction time task increased significantly and subjects reported greater fatigue and sleepiness the day after sleeping in the mask. Protection provided by the masks varied substantially among subjects and declined over the course of the study. Some soldiers were protected throughout the night but others were only protected intermittently. CONCLUSION: We conclude that sleeping in the chemical protective mask should only be done when necessary, given the adverse effects on sleep and daytime function, as well as the variability of protection, of the mask.     

Neurostimulation for obstructive sleep apnea: investigations

Neurostimulation of the upper airway muscles (accessory muscles of respiration) was accomplished in anesthetized dogs and sleeping humans by electrical stimulation of the hypoglossal nerves. Such stimulations relieved partial airway obstructions in dogs. They also aborted (shortened) obstructive sleep apnea events in humans who suffer with obstructive sleep apnea syndrome. In one subject, stimulations delivered in advance of apneic events (by automatic cycling) prevented apneas. Neurostimulation for obstructive sleep apnea may be an important concept for future research and development.     

The use of family drawings by children in pediatric practice

Sleep was actigraphically investigated in 27 Kibbutz children while sleeping in communal sleeping houses, and 1 year after changing to familial sleeping arrangements. Three independent control groups of city-living children were also recorded. Two of them were age-comparable, and the third control group was included in order to examine possible effects of the Gulf War on the communal sleep group. The results showed that the sleep quality of Kibbutz children improved significantly after moving to familial sleep. Comparison with the data from the two control groups revealed a greater resemblance between sleep of the Kibbutz children after moving to live with their families and that of the city-living children. Comparing the sleep of the children in communal sleep to that of the additional group of children examined during the Gulf War strengthened the above results, i.e. the communal sleep group that was investigated before the war slept worse than the control children that were investigated during the war. After discarding developmental and physical condition-related changes, it was concluded that the improvement in sleep quality was due to the children's increased sense of security when sleeping with their families.     

Respiratory patterns during sleep in Down's syndrome:importance of central apnoeas

Obstructive sleep apnoea episodes have been reported repeatedly in Down's syndrome (DS) patients as a consequence of the presence of predisposing malformations or intercurrent pathology of the upper airways. There are no data on respiratory patterns of uncomplicated Down's syndrome subjects. In order to evaluate the eventual effects of central nervous system (CNS) impairment on respiration in DS, we studied the respiratory patterns during sleep of a group of 10 DS subjects, aged 8.6-32.2 y, without relevant upper airway pathology. In order to control the possible effects of sleep structure and mental retardation on the results obtained, we compared the findings in DS with those obtained from a group formed by subjects affected by fragile X syndrome (six males and one female, aged 10.0-15.42 y) another genetically determined type of mental retardation. Sleep structure was similar in both groups; however, DS subjects showed significantly higher indices of central sleep apnoea and of oxygen desaturation than fragile X patients (P < 0.005). As far as DS individuals were considered, a significant preponderance of central, as opposed to obstructive, sleep apnoeas was found (89.4% vs. 9.4%, respectively; 1.2% were mixed) which showed a significant age-related increase. Central respiratory pauses were mostly preceded by sighs, which occurred more frequently during sleep stages 1 and REM, and were often organized in long sequences of periodic-like breathing. During REM sleep, they were less frequently preceded by sighs and by body movements than during NREM sleep. Obstructive sleep apnoeas occurred more often during REM sleep and were more rarely preceded by sighs or by body movements. Both central and obstructive apnoeas induced significant oxygen desaturation in 50-69.6%. Sleep structure was not significantly modified by apnoeas and oxygen desaturation. We hypothesize that the increase in central sleep apnoeas is related to a dysfunction of the central respiratory control at a brainstem level in DS.