Sleep-disordered breathing and oxygen desaturation in obese patients

Multi-center safety and efficacy study of a negative-pressure intraoral device in obstructive sleep apnea

BACKGROUND

Intraoral devices, with or without negative oral pressure, can stabilize the oropharynx and reduce obstructive sleep apneas. We tested the hypothesis that treatment with the iNAP® Sleep Therapy System, which applies negative oral pressure through an intra-oral appliance, would reduce the severity of obstructive sleep apnea in a multi-center, prospective, first-night-randomized-order cross-over study.

METHODS/PATIENTS

130 patients fulfilled the entry criteria (age <75, AHI 15-55, BMI <33), and 63 entered the primary endpoint cohort (Total Sleep Time ≥4 h/night on the baseline polysomnogram and an oral negative vacuum time maintained by iNAP® ≥ 4 h/night and total sleep time ≥4 h/night during the first treatment study). 54 patients completed a second treatment sleep study at least 28 days after the first sleep study.

RESULTS

Among the primary endpoint cohort (n = 63, age = 53.2 ± 11.3, BMI = 27.1 ± 2.8), 33 patients (52 %; 95 % confidence interval = 40%-64 %, p < 0.001) responded to iNAP treatment according to the Sher criteria (>50 % reduction in AHI and an AHI ≤20 events/hr). The average oxy-hemoglobin saturation increased by 1-2%, and the average percent oxygen desaturation decreased (was less severe) by 1 % while using the iNAP device. The incidence of adverse events, all self-limited, was low. The reduction in the apnea-hypopnea index was durable over the 28-day study. Patients used iNAP on average 5.6 h per night during the study period.

CONCLUSION

The iNAP® Sleep Therapy System achieved a durable benefit in more than half the patients with moderate to severe obstructive sleep apnea and may be considered in patients who object to or failed continuous positive airway pressure.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02698059.

Prevalent and sex-biased breathing patterns modify functional connectivity MRI in young adults

Resting state functional connectivity magnetic resonance imaging (fMRI) is a tool for investigating human brain organization. Here we identify, visually and algorithmically, two prevalent influences on fMRI signals during 440 h of resting state scans in 440 healthy young adults, both caused by deviations from normal breathing which we term deep breaths and bursts. The two respiratory patterns have distinct influences on fMRI signals and signal covariance, distinct timescales, distinct cardiovascular correlates, and distinct tendencies to manifest by sex. Deep breaths are not sex-biased. Bursts, which are serial taperings of respiratory depth typically spanning minutes at a time, are more common in males. Bursts share features of chemoreflex-driven clinical breathing patterns that also occur primarily in males, with notable neurological, psychiatric, medical, and lifespan associations. These results identify common breathing patterns in healthy young adults with distinct influences on functional connectivity and an ability to differentially influence resting state fMRI studies.

Functional connectivity measured from fMRI data is widely used in neuroscience. Here the authors report an association between two types of breathing signature and obtained BOLD data, and associated sex differences.

Apnea-hypopnea index: time to wake up

Despite the widespread use of the apnea-hypopnea index in research, its scientific and statistical properties have not been examined thoroughly. The index may be viewed either as a rate (number of events per hour of sleep) or as a ratio of two variables (number of events/number of hours of sleep). When considered as a rate, the apnea-hypopnea index may be modeled as the dependent variable, provided that researchers explicitly state which physical property they assume to be measuring. On the other hand, the index is rarely, if ever, the preferred model of exposure to sleep-disordered breathing (an independent variable), regardless of whether it is considered a rate or a ratio variable. Continued indiscriminate use of the apnea-hypopnea index in sleep research should be discouraged.

Testosterone therapy and obstructive sleep apnea: is there a real connection?

INTRODUCTION

With the recent increased recognition and treatment of hypogonadism in men, a caution has been given that testosterone replacement therapy (TRT) may cause or aggravate obstructive sleep apnea syndrome (OSA).

AIM

To evaluate the scientific data behind the cautionary statements about TRT and OSA.

MAIN OUTCOME MEASURES

Methodology and criteria for such studies and evaluation of documents and results based on methodology, duration, and outcome of treatment.

METHODS

A review of the literature on the subject of TRT and OSA was performed. The possible mechanisms of action of TRT, on breathing and respiration during sleep were explored.

RESULT

Historically, the first such caution came in 1978. Since then, a few similar incidence reports have been cited. The total number of patients in such reports was very small, very disproportional to the millions of patients treated with TRT. Also, there was a lack of consistent findings connecting TRT to OSA. In addition, different results may occur with physiologic replacement vs. supraphysiologic doses in regard to breathing and OSA. The studies showing the effect of TRT on OSA and breathing were all case studies with small numbers of subjects and showed little effect of TRT on OSA in the majority of case reports. Only one study using supraphysiologic doses was a double-blind, placebo-controlled study, which showed a development of OSA in healthy pooled subjects. The other reports were case studies with limited numbers of subjects, suggesting an inconsistent effect of supraphysiologic TRT on OSA and breathing.

CONCLUSION

Cautionary statements about TRT in OSA appear frequently in the TRT literature and guidelines, despite lack of convincing evidence that TRT causes and/or aggravates OSA. Also, there is a lack of consistency in the findings connecting TRT to OSA. It is evident that the link between TRT and OSA is weak, based on methodological issues in many of the studies, and most studies involved small numbers of men. Further studies in this area are needed.

Sleep-related erections: Clinical perspectives and neural mechanisms

Involuntary sleep-related erections (SREs) occur naturally during REM sleep in sexually potent men and other mammals. The regularity of their pattern and non-volitional nature made SREs useful clinically for differentiating psychogenic and organic erectile dysfunction (ED) in candidates for surgical intervention. Normative data available for different age groups added to the attractiveness of SRE measurement for clinical decision-making. Clinical SRE testing is less commonly applied today with the advent of minimally invasive medical therapies for ED. Nonetheless, as an objective measure of erectile function, SRE recording for research provides a precise technique for examining the mechanisms of erection and is still conducted to resolve legal disputes. SRE alterations provoked hormonally and pharmacologically are discussed. Different SRE patterns are associated with comorbid factors and some of these are illustrated, described, or both. Recording techniques developed for rats have proved extremely valuable for furthering our understanding of brain centers mediating erectile response. Data from lesion and stimulation studies are examined in the present review, moving us a step closer to understanding the underpinnings of erectile function.

Effect of testosterone on the apneic threshold in women during NREM sleep

The hypocapnic apneic threshold (AT) is lower in women relative to men. To test the hypothesis that the gender difference in AT was due to testosterone, we determined the AT during non-rapid eye movement sleep in eight healthy, nonsnoring, premenopausal women before and after 10-12 days of transdermal testosterone. Hypocapnia was induced via nasal mechanical ventilation (MV) for 3 min with tidal volumes ranging from 175 to 215% above eupneic tidal volume and respiratory frequency matched to eupneic frequency. Cessation of MV resulted in hypocapnic central apnea or hypopnea depending on the magnitude of hypocapnia. Nadir minute ventilation as a percentage of control (%Ve) was plotted against the change in end-tidal CO(2) (Pet(CO(2))); %Ve was given a value of zero during central apnea. The AT was defined as the Pet(CO(2)) at which the apnea closest to the last hypopnea occurred; hypocapnic ventilatory response (HPVR) was defined as the slope of the linear regression Ve vs. Pet(CO(2)). Both the AT (39.5 +/- 2.9 vs. 42.1 +/- 3.0 Torr; P = 0.002) and HPVR (0.20 +/- 0.05 vs. 0.33 +/- 0.11%Ve/Torr; P = 0.016) increased with testosterone administration. We conclude that testosterone administration increases AT in premenopausal women, suggesting that the increased breathing instability during sleep in men is related to the presence of testosterone.

Hormones and breathing

A number of hormones, including hypothalamic neuropeptides acting as neurotransmitters and neuromodulators in the CNS, are involved in the physiologic regulation of breathing and participate in adjustment of breathing in disease. In addition to central effects, some hormones also control breathing at peripheral chemoreceptors or have local effects on the lungs and airways. Estrogen and progesterone seem to protect from sleep-disordered breathing, whereas testosterone may predispose to it. Progesterone and thyroxine have long been known to stimulate respiration. More recently, several hormones such as corticotropin-releasing hormone and leptin have been suggested to act as respiratory stimulants. Somatostatin, dopamine, and neuropeptide Y have a depressing effect on breathing. Animal models and experimental human studies suggest that also many other hormones may be involved in respiratory control.

Effect of gender on the development of hypocapnic apnea/hypopnea during NREM sleep

We hypothesized that a decreased susceptibility to the development of hypocapnic central apnea during non-rapid eye movement (NREM) sleep in women compared with men could be an explanation for the gender difference in the sleep apnea/hypopnea syndrome. We studied eight men (age 25-35 yr) and eight women in the midluteal phase of the menstrual cycle (age 21-43 yr); we repeated studies in six women during the midfollicular phase. Hypocapnia was induced via nasal mechanical ventilation for 3 min, with respiratory frequency matched to eupneic frequency. Tidal volume (VT) was increased between 110 and 200% of eupneic control. Cessation of mechanical ventilation resulted in hypocapnic central apnea or hypopnea, depending on the magnitude of hypocapnia. Nadir minute ventilation in the recovery period was plotted against the change in end-tidal PCO(2) (PET(CO(2))) per trial; minute ventilation was given a value of 0 during central apnea. The apneic threshold was defined as the x-intercept of the linear regression line. In women, induction of a central apnea required an increase in VT to 155 +/- 29% (mean +/- SD) and a reduction of PET(CO(2)) by -4.72 +/- 0.57 Torr. In men, induction of a central apnea required an increase in VT to 142 +/- 13% and a reduction of PET(CO(2)) by -3.54 +/- 0.31 Torr (P = 0.002). There was no difference in the apneic threshold between the follicular and the luteal phase in women. Premenopausal women are less susceptible to hypocapnic disfacilitation during NREM sleep than men. This effect was not explained by progesterone. Preservation of ventilatory motor output during hypocapnia may explain the gender difference in sleep apnea.

Hour-to-hour variability of oxygen saturation in sleep apnea

STUDY OBJECTIVES

Methods used to express the severity of oxygen desaturation during polysomnography include the average oxygen saturation (AO2), lowest oxygen saturation (LO2), and the percent of the total time with oxygen saturation level lower than 90% (T<90%). We wanted to determine which one of these methods is least variable during different hours of monitoring.

DESIGN

Prospective, observational study.

SETTING

Sleep center at a medical university.

PATIENTS

One hundred fifty patients with apnea-hypopnea index from 5 to 130.

MEASUREMENTS

AO2, LO2, and T<90% were calculated during each of the 8 h of polysomnography. Data for each hour were compared and the Cronbach alpha coefficients were calculated.

RESULTS

There was a high degree of correlation among the three methods as well as between each method and the severity of sleep apnea. The mean+/-SD values for each method were as follows: AO2, 92.7+/-5.6; LO2, 68.5+/-19.3; and T<90%, 15.7+/-24.2. The alpha coefficients for these methods were AO2, 0.98; LO2, 0.88; and T<90%, 0.98. In all methods, the data of the first hour were significantly different from the data of the subsequent hours.

CONCLUSION

Both AO2 and T<90% methods show less hour to hour variability compared with LO2, and there is more variability in the first hour. Since the AO2 values >90% may not convey the severity of O2 desaturation, T<90% may be the best method of expressing oxygen saturation changes during polysomnography.

Sleep-related erectile activity

Sleep-related erections occur in all healthy, potent men in close temporal association with REM sleep. These erections are naturally occurring and can be assessed quantitatively. The nocturnal tumescence cycle seems unaffected by behavioral factors. Furthermore, sleep-related erections are present across the life span with only a slight decline in older healthy people. Analogous phenomena are present in women. The function of sleep-related erections is not known; however, they clearly involve vascular, neurologic, and hormonal mechanisms. Sleep-related erection testing provides a physiologic, objective, diagnostically useful technique for evaluating erectile capacity. Laboratory-based studies with comprehensive polysomnography offer the most complete diagnostic picture of erectile function available. Nonlaboratory procedures require further validation. The sleep-related tumescence pattern contains a wealth of information about the physiology and pathophysiology of erection. The coordination between REM sleep and erection, the differential expansion at the penile base and upper shaft, and the rate of circumference increase and decrease are meaningful indicators for determining if erectile dysfunction exists. Sleep-related erection testing indexes the magnitude and nature of organic involvement and takes the differential diagnosis of impotence beyond a simplistic psychogenic-organic dichotomy.

Developmental trends of sleep-disordered breathing in Prader-Willi syndrome: the role of obesity

Polysomnographic recordings of 43 children and adults with Prader-Willi syndrome (PWS) were inspected and classified into 5 age groups. The effect of age and body mass index (BMI) on measures of breathing, oxygen saturation, and sleep efficiency were analyzed. Body mass index (BMI) increased significantly between early childhood and preadolescent groups. Subjecting the data to analysis of variance showed an overall significant effect of BMI but no age effect on breathing parameters and oxygen saturation. Increased BMI was associated with decreased oxygen saturation and with higher apnea/hypopnea index. Sleep efficiency index was significantly lower in adults than in young children, preadolescent, and adolescent groups. These findings emphasize the role of obesity in the development of sleep-related breathing abnormalities and nocturnal oxygen desaturation in patients with PWS.

Obstructive sleep apnea in a consecutive series of obese women

The prevalence of obstructive sleep apnea (OSA) in women who were being seen for obesity assessment, rather than for assessment of sleep disturbance, was assessed. A consecutive series of referrals to an eating disorders clinic (n = 40) were studied in the sleep laboratory. Their body mass index (BMI) ranged from 29.4 to 66.9 kg/m2. Overnight polysomnograms were carried out, with respiration and oxygen saturation being monitored. Four women (10%), 1 postmenopausal and 3 premenopausal, had significant OSA. They tended to have a higher percentage of body fat and higher BMIs than the nonapnea group. These findings indicate that the prevalence of OSA is higher in the general population of obese women than is generally thought. They highlight the need for professionals who work with obese women to consider the possibility that some of the complaints of fatigue and tiredness may be a result of OSA.

Effects of a cognitive-behavioural weight loss programme on overweight obstructive sleep apnoea patients

Thirty-two obese patients (Body Mass Index (BMI) = 38.5 +/- 3.7) with obstructive sleep apnoea (the average number of oxygen desaturations per hour of sleep exceeding 4% from the baseline (ODI4) = 38.64 +/- 23.9) underwent a one-year cognitive-behavioural weight reduction programme with a one year follow-up period. The criteria for successful treatment were (i) a decrease in ODI4 to less than 10 and (ii) a decrease in ODI4 that was greater than 50%. Fourteen (44%) patients were considered to be treated successfully at six months. When the patients were grouped according to weight loss 23 patients had lost more than 5 kg; 12 (52%) of them belonged to the group treated successfully. At 24 months, however, only three (9%) patients could be regarded as treated successfully and six patients had been transferred to other treatment modes (Nasal Continuous Positive Airway Pressure (nCPAP) and uvulopalatopharyngoplasty (UPPP)). The changes in weight correlated with the changes in ODI4 (r = 0.47 and 0.63 at the 6-month and the 24-month evaluation, respectively).

Breathing frequency in sleep related respiratory disturbances

In normal adults, breathing frequency (f) is highly reproducible within an individual ranging from 8 to 25 min-1; during sleep, f is known to change only minimally. This variable is rarely reported in studies of adults with various sleep related respiratory disturbances (SRRD). We occasionally observed a spectacular increase of f during sleep in patients with SRRD associated with hypopnea and 02 desaturation. We undertook a retrospective study of 650 consecutive all-night polysomnographic recordings, in order to evaluate how often such an increase in breathing frequency occurs and with which factors it is associated. We excluded patients with major respiratory failure. We found 16 patients (11 males; mean +/- SD, age: 45 +/- 13 yrs; body mass index (BMI): 44 +/- 11 kg/m2) with f > 25 min-1 during sleep (tachypneic group, T). We performed a one-for-one matching for sex, age and BMI between the T and a control (C) group (age: 45 +/- 12 yrs; BMI 44 +/- 10 kg/m2), with similar sleep disturbances but normal f during sleep. We compared the f in each vigilance state by averaging five measurements of f, each of one minute duration in a stable period. We observed that: C patients showed no significant change in f in any vigilance state; T patients showed a higher f already during wakefulness (p < 0.05) and f increased significantly in all sleep stages (< 0.01). We compared the two groups for many clinical and polysomnographic variables.(ABSTRACT TRUNCATED AT 250 WORDS)

Nasal CPAP and weight loss in hypertensive patients with obstructive sleep apnoea

BACKGROUND

The high prevalence of obstructive sleep apnoea (OSA) in patients with systemic hypertension and of hypertension in patients with OSA suggests a causal link between the two disorders. This study was carried out to determine whether nasal continuous positive airway pressure (CPAP) and weight loss affect daytime hypertension in OSA.

METHODS

Sixty hypertensive patients with OSA took part in the study; 33 accepted nasal CPAP and used their machine for 5.7 (0.2) hours per night, and the remaining 27 patients refused nasal CPAP and upper airway surgery so the only therapeutic intervention was a recommendation of weight loss. A significant change in hypertension during follow up was defined as either a change in mean blood pressure of at least 10 mm Hg (or more than 8%) without a change in drug treatment, or a reduction in drug dosage with mean blood pressure within these limits. Weight loss was defined as a body mass index of at least 5% below the baseline value.

RESULTS

After 512 (41) days, hypertension had become less severe in seven of 12 patients (58%) treated with weight loss only, in eight of 28 patients (29%) with nasal CPAP only, in two of five patients with nasal CPAP and weight loss, and in one of 15 patients without nasal CPAP or weight loss. Multivariate analysis of variance with the outcome of hypertension at follow up as the dependent variable revealed that only the percentage change in body mass index significantly contributed to the course of hypertension.

CONCLUSION

The course of hypertension in OSA is more closely linked to weight loss than to elimination of sleep apnoea by nasal CPAP.

Snoring and obstructive sleep apnea

Evidence shows that snoring and obstructive sleep apnea have significant negative physiologic consequences. These patients should be treated expeditiously once the diagnosis is made and carefully followed to ensure that improvement is maintained.

Systemic hypertension in sleep apnea syndrome. Relationship with sleep architecture and breathing abnormalities

To examine the possible relationship between systemic HT and SAS we compared 21 hypertensive (HT+) and 29 normotensive (HT-) patients for morphologic characteristics, sleep disturbances and respiratory events monitored during a full night polysomnography. There was no significant difference between HT+ and HT- patients with respect to age, weight, BMI, sleep stage distribution and disorganization, apnea-hypopnea index (number of episodes per hour of sleep) and duration (minutes per hour of sleep) nor O2 saturation indices: mean nocturnal and minimum O2 saturation. We conclude therefore that HT in SAS patients is not directly related to morphologic characteristics, sleep disturbances and breathing abnormalities.

Prevalence of sleep apnea in men with erectile dysfunction

Sleep studies were performed on 1,025 patients complaining of erectile dysfunction. In addition to standard measures of sleep stage and nocturnal penile tumescence, respiratory activity was evaluated. The number of episodes of sleep apnea per hour (Apnea Index--AI) was calculated for each patient. The overall prevalence of sleep apnea activity in this sample was: 43.8 percent with AI greater than or equal to 5; 27.9 percent with AI greater than or equal to 10; and 19.6 percent with AI greater than or equal to 15. These results confirm that sleep apnea activity is common in men with erectile dysfunction. This high prevalence also indicates that further study is needed to elucidate pathophysiology of erectile failure in men with sleep apnea.

Effect of three alcohol doses on breathing during sleep in 30-49 year old nonobese snorers and nonsnorers

To test the effect of alcohol ingestion and snoring on sleep-disordered breathing (SDB), the sleep and respiration of 31 nonobese healthy males ages 30-49 (15 snorers, 16 nonsnorers) were studied overnight after alcohol ingestion. Subjects received placebo, 0.32, 0.65, and 0.81 g alcohol/kg body weight prior to their evening bedtime, with each dose given on one of four nonconsecutive nights in a repeated-measures counterbalanced design. On each night, respiration was assessed by recording respiratory effort from intercostal surface electromyography (EMG), ventilation from oral and nasal thermistors, and arterial oxygen saturation (SaO2) from an ear oximeter (BIOX III). Snorers had significantly: (a) more total SDB, (b) more obstructive sleep apnea (OSA), and (c) lower minimum SaO2 than nonsnorers after the placebo and each alcohol dose. Snorers had more hypoxic events than nonsnorers after each alcohol dose but not after placebo. Increasing alcohol dose caused a statistically significant (p = 0.0004) decrease in minimum SaO2 in snorers only, but this decrease was small and probably not clinically important. Alcohol did not cause significant increases in SDB and hypoxic events, and did not have different effects on SDB and hypoxic events for snorers versus nonsnorers. Because this experiment included only nonobese 30-49-year-old males, these results do not imply that alcohol has no significant effects on obese subjects or those older than 50.

Neuropsychiatric manifestations of obstructive sleep apnea: a review

Obstructive sleep apnea (OSA) may result in neuropsychiatric complications. Psychiatrists need to be alert to the possibility that patients who present to them with cognitive and/or affective disorders, who also have sleep related complaints such as snoring and significant daytime hypersomnolence, may have OSA. Clinical suspicion needs to be reinforced by obtaining a history from the bed partner. A polysomnogram will establish the diagnosis. Once the diagnosis is made, several treatment options are available. Treatment of sleep apnea usually leads to a resolution, or at least improved control, of the complicating neuropsychiatric disorder. Physicians must be aware that sedating neuroleptic or antipsychotic agents may worsen sleep apnea and, thereby, aggravate the neuropsychiatric disturbance.

[Gastroesophageal reflux during++ sleep in obese patients]

Evidence of relationship between gastrooesophageal reflux (GER) and obstructive apneas in some near-miss children, led us to investigate its possibility in adults. Our purpose was to look for 1) sleep stages of GER occurrence, and 2) the possible chronological link between sleep apneas and GER. Eight obese patients were investigated. Esophageal pHmetry was carried out on two consecutive nights. On the second night, sleep polygraphy was performed including EEG, EOG, EMG, nasal and buccal flows, thoracic and abdominal motions. Esophageal pHmetry was analyzed between the onset of sleep and the definite waking. Fifteen GER episodes occurred in 4 of the 8 patients. Fourteen of them occurred during wakefulness or transient arousals. Only 1 occurred during REM sleep. Four hundred forty five apneas were recorded in 7 patients. None of the obstructive apneas, or mixed apneas followed or preceded a GER. In 1 patient, 2 central apneas succeeded to GER during REM sleep. We conclude that 1) GER, as in healthy subjects, occurs essentially during wakefulness or transient arousals; 2) in these patients, we did not establish a causal relationship between GER and obstructive apneas nor between apneas and GER.

Sex differences in awake ventilatory drive and abnormal breathing during sleep in eucapnic obesity

We studied hypoxic and hypercapnic ventilatory drives in 22 eucapnic obese subjects (14 female and eight male subjects) referred for weight reduction therapy and 23 normal subjects (eight female and 15 male subjects). In the female subjects, both occlusion pressure, currently used as an indicator of ventilatory drive, and ventilatory responses to hypoxia, as well as occlusion pressure response to hypercapnia, were significantly greater in the obese than in the normal subjects; however, no significant differences in these responses between male obese and male normal subjects were observed, except for the hypoxic occlusion pressure response. We also studied disordered breathing during sleep in the obese subjects, and male predominance in abnormal breathing and oxygen desaturation was noted. These results showed that obese female subjects increased their hypoxic and hypercapnic chemosensitivities against their body mass loading, which was not evident in obese male subjects. The relatively depressed chemosensitivities of the latter may be related to disordered breathing and oxygen desaturation during sleep.

Respiration during sleep in kyphoscoliosis

Eleven subjects with non-paralytic and 10 with paralytic kyphoscoliosis and nine normal control subjects were studied during sleep. The Cobb angle of those with kyphoscoliosis varied from 60 degrees to 140 degrees (median 100 degrees) and the vital capacity varied from 17% to 56% (median 28%) of the value predicted on the basis of span. Recordings made during sleep included expired carbon dioxide tension at the nose, gas flow at the mouth, arterial oxygen saturation, chest wall movement, and the electroencephalogram, electro-oculogram, and electrocardiogram. In three subjects transcutaneous carbon dioxide tension was measured simultaneously. Patients with kyphoscoliosis hypoventilated during sleep, particularly in rapid eye movement sleep, resulting in a rise in end tidal and transcutaneous carbon dioxide tension, and a reduction in oxygen saturation to a degree not observed in normal subjects. Reduced chest wall movement was the major cause of these episodes, which were more frequent and occupied a greater proportion of sleep time in those with kyphoscoliosis than in normal subjects. Serious cardiac arrhythmias were rarely associated. It is concluded that disturbances of respiration during sleep occur in patients with kyphoscoliosis and that these may be important in the pathogenesis of cardiorespiratory failure.

Effect of chlormadinone acetate on sleep arterial oxygen desaturation in patients with chronic obstructive pulmonary disease

Twelve patients with chronic obstructive pulmonary disease (COPD) were studied in order to evaluate the effect of chlormadinone acetate (CMA), a potent synthetic progesterone, on the degree of hypoxemia during sleep. In patients designated as "correctors," in whom an increase in minute ventilation (VI) during wakefulness was brought about mainly by an increase in tidal volume (VT) and PaCO2 was effectively decreased by the administration of CMA, this agent also proved to be effective during sleep, with hypoxemia improved during both NREM and REM sleep. On the other hand, in patients called "noncorrectors" in whom a decrease in PaCO2 was not seen during wakefulness with CMA, there was also no effect during sleep. These results indicate that CMA is effective in certain selected patients with COPD.

Snoring: clinical implications and treatment

Snoring has only recently come under wide study. Recent research has established the close relationship of severe snoring to sleep apnea in terms of the obstructive pathophysiology. Snoring tends to increase in severity over time and may progress to sleep apnea. Severe snoring may be associated with pulmonary and systemic hypertension, secondary polycythemia, and cardiac arrhythmias.

Obesity and hormonal factors in sleep and sleep apnea

The presence of obesity, defined as weight 20 per cent or more above ideal body weight or increased body fat content, significantly increases risk of pulmonary, cardiovascular, metabolic, and gastrointestinal problems. Obesity is a major cause of shortened life expectancy. While obesity is not essential for the development of the obstructive sleep apnea syndrome, a significant percentage of patients with obstructive sleep apnea are obese. When evaluating these patients who have obstructive sleep apnea, it is important to search diligently for medical problems that are commonly found among the obese. While there is an increased incidence of obese patients among those who have obstructive sleep apnea, the exact reason for this is uncertain. The study of endorphins and enkephalins may expand our understanding of obesity, ventilatory regulation, and obstructive sleep apnea. This may, in fact, enable us to understand better the interrelationship between obesity and obstructive sleep apnea. The role that thyroid hormone, testosterone, and progesterone play in obstructive sleep apnea has also been reviewed. Patients who have obstructive sleep apnea should not be treated with testosterone. All patients given testosterone should be observed quite closely for the possible signs and symptoms of obstructive sleep apnea. Progesterone seems to be of some help in patients who have obesity hypoventilation syndrome. Its effectiveness in patients with obstructive sleep apnea is less clear. The obesity hypoventilation syndrome as described by Burwell is relatively uncommon. Many of the manifestations of the obesity hypoventilation syndrome, however, are found in patients with obstructive sleep apnea. The recognition that the symptoms stem from underlying obstructive sleep apnea offers great potential for therapy. Weight reduction is valuable therapy for patients with obesity and pulmonary dysfunction, obesity and obstructive sleep apnea, and obesity hypoventilation syndrome. Weight reduction and weight maintenance, while difficult, are essential in patients with obesity, obesity and obstructive sleep apnea, and the hypoventilation syndrome. Obesity should be viewed as a medical problem deserving medical attention and long-term medical follow-up.

Testosterone replacement in hypogonadal men: effects on obstructive sleep apnoea, respiratory drives, and sleep

The obstructive sleep apnoea syndrome occurs predominantly in men. To determine the effect of testosterone on ventilatory function and whether testosterone may play a role in the development of obstructive apnoea, we performed waking ventilatory drive studies and sleep studies in five hypogonadal men. These androgen-deficient subjects were studied both while receiving no treatment and after six weeks of testosterone replacement therapy (testosterone oenanthate 200 mg i.m. every 2 weeks). Hypoxic ventilatory drive decreased significantly, from 158 +/- 39 (mean +/- SEM) off testosterone to 88 +/- 19 on testosterone therapy (P less than 0.05). Hypercapnoeic ventilatory drive did not change significantly on testosterone. Obstructive sleep apnoea developed in one man and markedly worsened in another man in association with testosterone administration. Both of these subjects also exhibited marked decreases in oxygen saturation with the development of cardiac dysrhythmias during sleep and large increases in haematocrit. The remaining three hypogonadal men did not demonstrate significant sleep apnoea either on or off testosterone. The percentage of sleep time spent in REM sleep increased from 14 +/- 3% to 22 +/- 2% when the men were receiving testosterone (P less than 0.01), but the episodes of sleep apnoea tended to occur during non-REM sleep. We conclude that in some hypogonadal men, replacement dosages of testosterone may affect ventilatory drives and induce or worsen obstructive sleep apnoea. The obstructive sleep apnoea syndrome is a potential complication of testosterone therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Nocturnal hypoxia and prolactin secretion in obese women

Respiration during sleep was studied in six obese women who had impaired prolactin response to insulin induced hypoglycaemia (non-responders), six obese women with a normal prolactin response to hypoglycaemia (responders), and six lean women. Sleep apnoea did not occur in any subject. All the obese women showed a decrease in haemoglobin oxygen saturation when asleep, which occurred predominantly during periods of rapid eye movement sleep. That the fall in oxygen saturation was significantly greater (p less than 0.05) in the obese non-responders suggests that central as well as mechanical factors may be important for the genesis of nocturnal hypoxia and is evidence for a disturbance of central nervous function in some obese women.

Flow-volume curves and sleep-disordered breathing: therapeutic implications

To assess the relationship of abnormal flow-volume curves during awake periods to the clinical severity of sleep-disordered breathing and the need for surgical treatment of obstructive sleep apnoea, flow-volume curves were measured in 72 adults with obstructive apnoea. Patients in whom surgery was recommended for standard clinical indications had significantly lower inspiratory flow rates (p less than 0.01) and a higher incidence of flow-volume curves indicating extrathoracic airway obstruction (p less than 0.01) than did non-surgical patients. These abnormal flow-volume curves correlated with an increased severity of nocturnal oxygen desaturation (p less than 0.01). Furthermore, increases in inspiratory flow rates measured serially in 22 patients were related to improvement in their polysomnography (p less than 0.05), suggesting that alterations of airway function during awake periods correlate with changes in the severity of sleep apnoea.

Sleep related breathing disorders in older men: a search for underlying mechanisms

The incidence of sleep-related breathing disorders (SRBDs) associated with hemoglobin desaturation was determined by nocturnal polygraphic evaluations in 26 healthy men, aged 55-70 years. Sixteen subjects (62%) had abnormal rates of at least 12 episodes per hour of sleep: 8 had occlusive, and 8 had central apnea or hypopnea. During waking ten of 16 SRBD subjects and only one subject without SRBDs exhibited either an elevated nasopharyngeal airway resistance (n = 4) or a reduced ventilatory response to hypercapnia (n = 4) and/or hypoxia (n = 3). However, these abnormalities were not related to the type or severity of SRBDs, and 6 subjects with SRBDs demonstrated no respiratory defect. We conclude that SRBDs have a very high incidence in older males and are not usually secondary to pulmonary cardiac, neurological, or behavioral disorders. Additionally, we hypothesize that abnormalities in ventilatory control or upper airway resistance contribute to SRBDs, but depression of brain stem reticular formation activity during sleep plays a primary role in these disorders. Factors related to both aging and SRBDs are reviewed. These include reduced chemoreceptor responses, altered steroid hormone metabolism, and use and metabolism of hypnotic drugs and alcohol.

The effect of weight loss on sleep-disordered breathing and oxygen desaturation in morbidly obese men

Four morbidly obese men who had been found to have significant sleep-disordered breathing and oxygen desaturation were restudied after an average weight loss of 108 kg (range 53-155 kg). In all subjects, weight loss was accompanied by a significant reduction in the number of episodes per hour of sleep-disordered breathing events. In three of the four subjects, there was improvment in the severity of desaturation accompanying abnormal breathing. The two subjects with daytime somnolence and hypercapnia prior to weight loss showed the most dramatic improvement in desaturation. This suggests that obesity is a cause, rather than an effect, of the sleep apnea syndrome.