Continuous Monitoring of Respiratory Variables During Sleep by Microcomputer

A microcomputer system has been developed to acquire, process and store respiratory and heart rate data for all-night sleep studies. Signals monitored continuously are: expired carbon dioxide (an index of airflow); respiratory inductance plethysmography (an index of the volume of air exchanged); oxygen saturation; and heart rate. The respiratory inductance Plethysmograph signal is reduced to a set of values which summarize each complete respiratory cycle (inspiratory time, expiratory time, and tidal volume index). Values of oxygen saturation and heart rate are saved at two points: the onset of inspiration and expiration. These signals, and derived values, are continuously updated on the system video display terminal. An audible alarm signals the presence of apneic events, and defects in the computer-polygraph interface. The software identifies three forms of apnea (central, obstructive, and mixed) in accordance with conventional definitions. A continuous polygraphic recording is time-synchronized, by a software generated time-coded signal, to enable the subsequent incorporation of the manually reduced sleep stage data. The sleep stage distribution data is placed, under program control, on the same storage medium as the computer-acquired data. Statistical relationships between sleep stage and respiration are investigated.

Sleep complaints and restless legs syndrome in adult type 2 diabetics

OBJECTIVE

To determine the prevalence and characteristics of sleep complaints and restless legs syndrome (RLS) in type 2 adult diabetics. To test the hypothesis that sleep complaints are more common among adult diabetics.

BACKGROUND

Restless legs syndrome is a common disorder and is a cause of insomnia and daytime somnolence. An association between RLS and diabetes mellitus has been hypothesized but has not been established.

METHODS

Consecutive type 2 diabetic patients and controls were subjected to sleep questionnaires, examinations for sensory neuropathy, and laboratory investigations.

RESULTS

Diabetics had higher rates of insomnia (50 vs. 31%, P=0.04) and used more hypnotics (25.9 vs. 6.0%, P=0.02) than controls. The proportion of diabetics with elevated Epworth Sleepiness Scores (> or =12) was higher than controls (15.5 vs.2.1%, P=0.02). The prevalence of RLS among diabetics was not significantly different than in controls (24.1 vs. 12.5%, P=0.1). The prevalence of sensory polyneuropathy was similar in diabetics with and without RLS. Age, BMI, duration and level of diabetes control, hemoglobin, ferritin and creatinine levels did not predict the presence of RLS in diabetics.

CONCLUSIONS

Adult type 2 diabetics have higher rates of insomnia, excessive somnolence and hypnotic use than controls. There is no evidence that RLS is significantly more common in adult diabetics.

Cardiovascular medication use in patients with undiagnosed obstructive sleep apnoea

BACKGROUND

A study was undertaken in patients with undiagnosed sleep apnoea/hypopnoea syndrome (OSAS) to document the use of prescribed medications, especially those used in cardiovascular diseases, in the year before the OSAS diagnosis was confirmed.

METHODS

A total of 549 patients with OSAS (401 men of mean age 47.2 years, mean body mass index (BMI) 35.5 kg/m(2), mean apnoea/hypopnoea index (AHI) 47.2 and148 women of mean age 50.2 years, BMI 39.6 kg/m(2), AHI 32.6) were each matched to one general population control by age, sex, geographical location, and family physician. Medication use was evaluated for patients and controls using a database containing information about all prescriptions completed in the province of Manitoba, Canada.

RESULTS

In the year before OSAS was diagnosed, prescribed medication costs were $155.91 (Canadian dollars) (95% CI $91.34 to $220.49) greater for cases than for controls. Cases were dispensed 3.3 (95% CI 1.5 to 5.2) more prescriptions, were on 1.2 (95% CI 0.8 to 1.6) more medications, and were supplied with 157.4 (95% CI 95.9 to 218.8) more daily doses of medication. The odds ratio of OSAS cases being on a prescribed medication was 1.88 relative to controls (95% CI 1.38 to 2.54, p<0.0001). In the same year 36.6% of cases and 19.7% of controls were using medications for cardiovascular disease (OR 2.82, 95% CI 2.05 to 3.89, p<0.0001), consuming 79.4 (95% CI 48.9 to 109.8) more daily doses of medication, having been dispensed 1.7 (95% CI 1.0 to 2.4) more prescriptions, and at a $75.26 (95% CI $44.03 to $106.50) greater cost. The odds ratio of patients with OSAS being on medications indicated for the treatment of systemic hypertension was 2.71 (95% CI 1.96 to 3.77) relative to controls; however, such medications might also be prescribed for other indications such as angina pectoris and congestive heart failure, and for the secondary prevention of myocardial infarction. The use of medications indicated for the treatment of systemic hypertension was predicted significantly by age (odds ratio (OR) 1.10 per year), BMI (OR 1.05 per unit), and AHI (OR 1.01 per unit).

CONCLUSIONS

In the year before OSAS was diagnosed, patients with OSAS were heavy users of medications, particularly those used to treat cardiovascular diseases.

Obstructive sleep apnea patients use more health care resources ten years prior to diagnosis

Because Obstructive Sleep Apnea Syndrome (OSAS) patients may be treated for comorbidities prior to OSAS diagnosis, we examined the health care utilization records of 181 OSAS patients and those of matched controls. We compared OSA patient health care utilization for a ten-year interval prior to diagnosis to those of randomized age-, gender-, and geographically-matched controls from the general population. We found that OSAS patients used approximately twice the resources (as defined by physician claims and stays in hospital) in the ten years prior to their diagnosis. Physician claims for cases totaled $686,365 ($3,972 per patient) compared to $356,376 ($1,969 per patient) for the controls for the length of the study. Utilization was significantly higher in 7 of 10 years prior to diagnosis. OSAS patients also had more hospitalizations: they had 1,118 nights (6.2 per patient) in hospital versus 676 nights (3.7 per patient) for controls over the ten-year period. Thus OSA patients are heavy users of health care resources ten years prior to diagnosis.

The use of health-care resources in obesity-hypoventilation syndrome

OBJECTIVE

To document health-care utilization (ie, physician claims and hospitalizations) in patients with obesity-hypoventilation syndrome (OHS), for 5 years prior to the diagnosis and for 2 years after the diagnosis and initiation of treatment.

DESIGN

Retrospective observational cohort study.

SETTING

University-based sleep disorders center in Manitoba, Canada.

PATIENTS AND CONTROL SUBJECTS

Twenty OHS patients (mean [+/- SD] age, 52.7 +/- 9.5 years; body mass index [BMI], 47.3 +/- 11.0 kg/m(2); PaCO(2), 59.7 +/- 13.8 mm Hg; PaO(2), 51.6 +/- 12.4 mm Hg) were matched to two sets of control subjects. First, each case was matched to 15 general population control subjects (GPCs) by age, gender, and geographic location, and, second, each case was matched to a single obese control subject (OBC) who was matched using the same criteria as for the GPCs, plus the measurement of BMI.

MEASUREMENTS AND RESULTS

In the 5 years before diagnosis, the 20 OHS patients had (mean +/- SE) 11.2 +/- 1.8 physician visits per patient per year vs 5.7 +/- 0.8 (p < 0.01) visits for OBCs and 4.5 +/- 0.4 (p < 0.001) visits for GPCs. OHS patients generated higher fees, $623 +/- 96 per patient per year for the 5 years prior to diagnosis compared to $252 +/- 34 (p < 0.001) for OBCs and $236 +/- 25 (p < 0.001) for GPCs. OHS patients were much more likely to be hospitalized than were subjects in either control group in the 5 years prior to diagnosis (odds ratio [OR] vs GPCs, 8.6) (95% confidence interval [CI], 5.9 to 12.7); OR vs OBCs, 4.9 (95% CI, 2.3 to 10.1). In the 2 years after diagnosis and the initiation of treatment (usually continuous positive airway pressure or bilevel positive airway pressure), there was a significant linear reduction in physician fees. In the 2 years after the initiation of treatment, there was a 68.4% decrease in days hospitalized per year (5 years before treatment, 7.9 days per patient per year; after 2 years of treatment, 2.5 days per patient per year [p = 0.01]).

CONCLUSIONS

OHS patients are heavy users of health care for several years prior to evaluation and treatment of their sleep breathing disorder; there is a substantial reduction in days hospitalized once the diagnosis is made and treatment is instituted.

Diagnosis and management of sleep apnea syndrome

Sleep apnea is the cessation of breathing during sleep. These episodes result in hypoxemia and sleep disruption; thus the consequences are both cardiorespiratory and neural. Sleep apnea syndrome is defined by a constellation of signs and symptoms, with the main presenting symptom being excessive daytime sleepiness. A diagnosis requires documentation of episodes of abnormal breathing during sleep. This disorder, once thought to be very rare, is so common that it is unlikely that any busy clinician has not encountered a case. Facilities for the evaluation of sleep breathing disorders are now available in most communities. With the introduction of continuous positive airway pressure and other treatments, most patients have complete resolution of their disabling symptoms.

Health care utilization in males with obstructive sleep apnea syndrome two years after diagnosis and treatment

OBJECTIVE

To document changes in health care utilization (physician claims and hospitalizations) two years after diagnosis and treatment of patients with OSAS.

DESIGN

Prospective observational cohort study.

SETTING

The study was done in the Canadian Province of Manitoba. OSAS patients were selected from a University-based sleep disorders center. Control subjects were selected from the general population.

PATIENTS AND CONTROLS

There were 344 OSAS patients on whom there was utilization data for the period of the study. They were matched to controls from the general population by gender, age, and geographic location.

MEASUREMENTS AND RESULTS

The difference in physician claims between the patients and their matched controls two years after diagnosis and treatment ($174+/-32.4 (SE) per year in Canadian dollars) was significantly less than the difference in the year before diagnosis ($260+/-35.7 (SE), p=0.038). Examining the subgroups of patients adhering (PAT) or not adhering (PNAT) to treatment revealed that the changes were only significant in the patients adhering to treatment. Hospital stays for the entire OSAS group decreased from 1.27 days+0.25(SE) per patient per year one year before diagnosis to 0.54+0.13 per patient per year (p=0.01). The changes in the PAT group (1.25+0.28 per patient per year one year before diagnosis to 0.53+0.14 per patient per year (p=0.034) were significant while in the PNAT group they were not.

CONCLUSIONS

Adherence to treatment in patients with OSAS results in a significant reduction in physician claims and hospital stays.

Upper airway resistance syndrome: effect of nasal dilation, sleep stage, and sleep position

BACKGROUND

The upper airway resistance syndrome (UARS) is one of the mild variants of obstructive sleep disordered breathing. Nasal obstruction is proposed as one of the mechanisms that lowers intrapharyngeal pressure and hence increases airway collapsibility.

OBJECTIVE

We evaluated the effect of external nasal dilation and sleep position on sleep in UARS.

METHOD

A double blind, randomized, controlled study with a crossover design (using therapeutic and placebo dilators) was conducted in 18 consecutive patients with UARS. Each patient had two overnight sleep studies one to two weeks apart. Cardiorespiratory parameters (AHI, percentage of time that SaO2 was more than 2% below awake [desaturation time] and mean overnight heart rate), sleep architecture (sleep stages, sleep efficiency, and arousal index), and body position were determined.

RESULTS

Application of the external nasal dilator resulted in a significant increase in the nasal cross-sectional area (p < 0.001). Treatment reduced stage 1 sleep (as a percent of total sleep time) from 8.6 +/- 0.8% to 7.1 +/- 0.7 (SEM), p = 0.034). Desaturation time was significantly lower with treatment (12.2 +/- 2.2% on placebo versus 9.1 +/- 1.3 on treatment, p = 0.04). There were no additional significant effects on the cardiorespiratory parameters, sleep architecture, or MSLT when the entire night was examined. Controlling for interactions of sleep stage and position and treatment we found that treatment reduced desaturation time (p = 0.03) but not AHI or arousal index. AHI was significantly lower in the lateral position compared to the supine (p = 0.0001) and in NREM sleep compared to REM (p = 0.001). Desaturation time was significantly lower on the lateral compared to the supine position (p = 0.002) and in NREM sleep compared to REM (p = 0.006). Arousal index was highly dependent on sleep stage (p = 0.0001): the index was higher in stage 2 compared to slow wave sleep and REM. Sleep position and treatment had no significant effect on arousals.

CONCLUSIONS

External nasal dilation reduced stage 1 sleep, an indirect marker of disrupted sleep, and desaturation time. There were no additional effects on sleep architecture or sleep disordered breathing. Both sleep position and sleep stage had a significant effect on sleep disordered breathing in UARS.

Health care utilization in the 10 years prior to diagnosis in obstructive sleep apnea syndrome patients

Obstructive sleep apnea syndrome (OSAS) patients may have symptoms for years prior to recognition of their disorder, or they may be treated for the associated comorbidities. We hypothesized that such patients would be heavy consumers of health care resources for several years prior to diagnosis. We therefore compared health service utilization for a 10-year interval prior to diagnosis of 181 OSA patients to those of randomly selected age-, gender-, and geographically matched controls from the general population. OSAS patients used approximately twice as many health care services (as defined by physician claims and overnight stays in hospital) in the 10 years prior to their initial diagnostic evaluation for apnea. Physician claims for the OSA patients totaled $686,365 ($3972 per patient), compared to $356,376 ($1969 per patient) for the controls for the 10-year period examined in this study. Use of health services was significantly higher in 7 of 10 years prior to diagnosis. The OSAS patients also had more overnight hospitalizations: they spent 1118 nights (6.2 per patient) in hospital vs 676 nights (3.7 per patient) for controls in the decade prior to diagnosis. We conclude that by the time patients are finally diagnosed for sleep apnea, they have already been heavy users of health services for several years. It is possible that our findings reflect not OSAS per se, but the presence of some of the risk factors that predispose to OSAS, such as obesity, alcohol usage and perhaps tobacco consumption.

Clinical presentations of obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is a common but still underrecognized disorder. It affects 2% to 4% of middle-aged adults, a significant proportion of whom are female. The spectrum of clinical presentations of OSAS and their severity is variable, ranging from neurocognitive complaints to cardiorespiratory failure. OSAS has a significant impact on quality of life, cardiovascular morbidity, and mortality. Its major sequelae include daytime somnolence and its consequences (motor vehicle accidents, poor work performance, disrupted social interactions), systemic and pulmonary hypertension, and ischemic heart disease. Treatment of OSAS results in improvement in symptoms, quality of life, and blood pressure control, and may improve mortality. An expansion of our understanding of this condition has resulted in increased awareness of its consequences, but the recognition of OSAS in clinical practice is still delayed. Identification of these patients in clinical practice requires attention to risk factors (history of snoring and witnessed apneas, obesity, increased neck circumference, hypertension, family history) and careful examination of the upper airway. Clinical impression alone, however, has poor (50% to 60%) sensitivity and specificity (63% to 70%) and the diagnosis is usually obtained on polysomnography. Physicians and other health care professionals need to be aware of the progress made in this area and recognize the necessity for prompt evaluation and treatment of these patients.

Susceptibility of LDL to oxidative stress in obstructive sleep apnea

Cardiovascular diseases are more common in patients with obstructive sleep apnea (OSA) than in the general population. We hypothesized that severe hypoxemia during sleep in these patients may cause an imbalance between reactive oxygen species and the antioxidant reserve that is important for the detoxification of these molecules. We tested the hypothesis that low-density lipoproteins (LDL) in hypoxic OSA patients may be more susceptible to oxidative stress than LDL of nonhypoxic OSA patients and normal controls. Fifteen OSA patients were included in this study, six with severe hypoxia (hypoxic group) who spent more than 10 minutes during sleep with SaO2 < 85% (mean 96 minutes), and nine OSA patients (nonhypoxic group) who spent less than 10 minutes during sleep with SaO2 < 85% (mean 1.1 minutes). Six healthy nonsmoking males of the same age group were included as a control group. The susceptibility of each individual's LDL to oxidative stress was examined after free-radical challenge in vitro by assessing changes in levels of conjugated dienes. The LDL in OSA patients with severe hypoxia was not more susceptible to oxidative stress compared to the LDL of nonhypoxic OSA patients and normal controls. After 6 hours of exposure to an oxidative agent, the changes in the mean conjugated diene were not different among the three groups (p = 0.75). The time required to reach 50% of maximal absorbance was also not different, p = 0.199. Glutathione peroxidase and catalase activities in red blood cells in the hypoxic and nonhypoxic patient groups were not significantly different. One night of CPAP therapy in each patient group did not significantly change the level of the antioxidant enzymes. Our results did not show any difference in the susceptibility to oxidative stress between hypoxic and nonhypoxic OSA patients and normal controls.

Randomized, double-blind, placebo-controlled crossover trial of modafinil in the treatment of excessive daytime sleepiness in narcolepsy

Seventy-five patients meeting international diagnostic criteria for narcolepsy enrolled in a 6-week, three-period, randomized, crossover, placebo-controlled trial. Patients received placebo, modafinil 200 mg, or modafinil 400 mg in divided doses (morning and noon). Evaluations occurred at baseline and at the end of each 2-week period. Compared with placebo, modafinil 200 and 400 mg significantly increased the mean sleep latency on the Maintenance of Wakefulness Test by 40% and 54%, with no significant difference between the two doses. Modafinil, 200 and 400 mg, also reduced the combined number of daytime sleep episodes and periods of severe sleepiness noted in sleep logs. The likelihood of falling asleep as measured by the Epworth Sleepiness Scale was equally reduced by both modafinil dose levels. There were no effects on nocturnal sleep initiation, maintenance, or architecture, nor were there any effects on sleep apnea or periodic leg movements. Neither dose interfered with the patients' ability to nap voluntarily during the day nor with their quantity or quality of nocturnal sleep. Modafinil produced no changes in blood pressure or heart rate in either normotensive or hypertensive patients. The only significant adverse effects were seen at the 400-mg dose, which was associated with more nausea and more nervousness than either placebo or the 200-mg dose. As little as a 200-mg daily dose of modafinil is therefore an effective and well-tolerated treatment of excessive daytime somnolence in narcoleptic persons.

Using self-reported questionnaire data to prioritize OSA patients for polysomnography

Many laboratories have large numbers of patients with suspected obstructive sleep apnea (OSA) waiting to be tested. We assessed the use of simple clinical data to detect those patients with an apnea index <20 (low AI) who could be studied less emergently. Using questionnaires completed by patients prior to evaluation, we collected data on 354 consecutive patients (281 males, 73 females; mean age 48.6 years) referred for OSA and assessed with polysomnography (PSG). The questionnaires included the Epworth sleepiness scale (ESS), height, weight, age, and a history of observed apnea. Analysis of receiver operating characteristics curves revealed that both body mass index (BMI) [area under curve = 0.7258, standard error (SE) = 0.03, p < 0.01] and ESS (area under curve = 0.5581, SE = 0.03, p = 0.03) were significantly better than chance alone in detecting people with AI < 20. ESS < or =12 was found in 37.9% of the subjects but 39.6% of those expected to have a low AI using ESS had an AI > or =20. A BMI < or =28 was found in 24.9% of the subjects; 14.8% of those expected to have a low AI using BMI had an AI > or =20. Combining these variables improved accuracy but resulted in smaller groups; a cut-off of ESS < or =12 and BMI < or =28 resulted in a group of 33 (9.3% of subjects), only two (6%) of whom were falsely called low AI. Adding to this the fact that apnea had not been observed resulted in a group of nine patients (2.5% of subjects), none of whom had an AI > or =20. Thus there is a tradeoff; the more variables used, the greater the accuracy but the smaller the percent of cases selected to have low AI. However, in laboratories with hundreds of patients waiting to be tested, any procedure better than chance to help prioritize patients seems worthwhile.

Utilization of health care services in patients with severe obstructive sleep apnea

We compared the health care utilization of 97 obese patients diagnosed with obstructive sleep apnea (OSA) and 97 matched control subjects. Over a 2-year period that ended 2 years prior to initial diagnosis, the OSA group had 251 nights in hospital, compared to 90 nights for the control group. During the same 2-year period, total expenditures from physician claims were $82,238 (Canadian dollars) in the OSA patients versus $41,018 in the control group (p < 0.01). Depending upon which assumptions one uses for the calculation of hospital costs, during the same 2-year period, the 97 OSA patients utilized between $100,000 and $200,000 more in services than their control counterparts. We conclude that sleep apnea patients are already heavy consumers of health care services prior to any specific evaluation and treatment for apnea.

L-DOPA/carbidopa for nocturnal movement disorders in uremia

Restless legs syndrome (RLS) and periodic limb movements during sleep (PLMS) are sleep disorders that are common and distressing to uremic patients. There are few data regarding effective treatment in this population. Five chronic hemodialysis patients completed a double-blind, placebo-controlled, crossover study using a single bedtime dose of controlled release L-DOPA/carbidopa (100/25 mg) for treatment of RLS and sleep disruption. Leg movements per hour of sleep and percentage of sleep time accompanied by leg movements were decreased with treatment (101.0 +/- 29.1 events/hour on placebo vs. 61.0 +/- 28.3 events per hour on drug, p = 0.006; and 15.1 +/- 4.9% of sleep time with leg movements on placebo vs. 8.6 +/- 4.0% on drug, p = 0.014). In addition, arousals associated with leg movements (mean 209 +/- 49 events on placebo, mean 108 +/- 46 events on drug) and the leg movement arousal index (mean 59 +/- 23 events/hour on placebo, mean 23 +/- 9 events/hour on drug) were decreased by active medication (p = 0.03 and 0.04, respectively). Patients, however, continued to have very disrupted sleep and we could not document consistent subjective or objective improvement in overall sleep except for an increase in slow-wave sleep (SWS) from 9.0% to 22.8% (p = 0.01). The patterns of movements during sleep were not uniform in different patients, and the movements, although often periodic, were much longer than defined for PLMS. Because of this, finding suitable objective parameters to analyze was problematic. Measuring the percentage of sleep time during which there were leg movements was probably the most efficient and reproducible means of quantitating this disorder. Thus, although controlled-release L-DOPA/carbidopa at a dose of 100/25 mg given once nightly reduced leg movements and increased SWS, sleep continued to be disrupted. Whether higher doses or more frequent dosing is effective requires further investigation.

Effect of severe gastroesophageal reflux on sleep stage in patients with aperistaltic esophagus

Polysomnography and esophageal pH studies were conducted in 13 patients with an aperistaltic esophagus; seven of these had scleroderma and six were patients treated for achalasia. The percentage total time of pH<4.0 when recumbent exceeded 30% for both groups. There was a total of 51 reflux events for both groups. There were 22 reflux events recorded for both groups that were less than 5 min in length and 29 events greater than 5 min. In 26 of 32 (81%) instances, patients either began awake and went to sleep during a reflux event or did not awake during a reflux event. Only six of 32 (19%) reflux events caused sleep disruption. We conclude that even the severe reflux demonstrated in this subset of patients does not always disrupt sleep. Patients may have severe prolonged reflux and not arouse.

Medical treatment of sleep apnea

Obstructive sleep apnea is a common disorder. Since 1981 the treatment of choice has shifted from tracheostomy or weight loss to uvulopalatopharyngoplasty and then to continuous positive airway pressure. This review encompasses the most recent literature, focusing mainly on current treatment options and other potential and experimental modes of therapy. We review in detail continuous positive airway pressure therapy, including unwanted effects; compliance and possible ways to improve it; and ways to deal with the difficult patient. We also review dental appliances, electrical stimulation, and potential hormonal and nicotine treatment.

Sleep complaints are common in a dialysis unit

Sleep disturbance among uremic patients is reported to be high, but data on the actual prevalence, clinical significance, and causative factors is limited. A sleep questionnaire was distributed to an entire hemodialysis unit of 64 patients. Of the 54 patients who completed the survey, 83.3% had sleep-wake complaints. Disturbed sleep was reported by 28 patients (51.8%), and causes were secondary to delayed sleep onset in 25 patients (46.3%), frequent awakening in 19 patients (35.2%), restless legs syndrome (RLS) in 18 patients (33.3%), and generalized restlessness in six patients (11.1%). Daytime sleepiness was the most frequent complaint, reported by 36 patients (66.7%), and RLS was the second most frequent specific complaint, reported by 31 patients (57.4%). Symptoms of sleep apnea were described by seven patients (13.0%). Male gender, age more than 60 years, RLS, and caffeine intake were associated with more sleep-wake complaints (P = 0.009, P = 0.002, P = 0.028, and P = 0.008, respectively). Urea and creatinine levels were higher in patients with RLS (P = 0.04 and P = 0.08, respectively); otherwise, no other metabolic or demographic variable was associated with specific sleep disorders or disturbance. Sleep problems are very common in dialysis patients and likely contribute to the impaired quality of life experienced by many of these patients.

A familial awake movement disorder mimicking restless legs in a sleep apnea patient

We report on a patient with sleep apnea and an unusual familial movement disorder. The movements were present only during wakefulness and nocturnal arousals caused by disordered breathing. A 27-year-old obese man was referred with sleep onset insomnia, symptoms suggesting restless legs syndrome, daytime sleepiness, loud snoring and awakening with choking sensations. He was proven to have obstructive sleep apnea (apnea hypopnea index = 60.6). He also had a daytime movement disorder that was characterized by almost continuous stereotypic tapping of one or both legs. The movements were suppressible and not associated with any unpleasant or abnormal leg sensation. Virtually identical movements were present in three generations of his family. The severity of the movements did not worsen late in the day or with supine posturing. The nocturnal movements, consisting of a visible shaking of one or both legs, occurred only during arousals secondary to the apnea, had a mean duration of 5.7 +/- 3.0 (standard deviation) seconds and could not be defined as periodic limb movements in sleep (PLMS). Successful treatment of apnea by nasal continuous positive airway pressure dramatically reduced the movements during sleep (from 88.2 to 1.9 per hour). The clinical significance and the mechanism of this movement disorder is unknown. We discuss the features inconsistent with restless legs syndrome and consider other possible phenomenology, including akathisia. We conclude that this patient may have a previously unreported familial movement disorder and in addition developed the sleep apnea syndrome related to obesity.

Irregular breathing during sleep in patients with panic disorder

OBJECTIVE

The authors examined the nocturnal breathing patterns of patients with panic disorder to determine whether these individuals had respiratory irregularities at a time when anxiety was not manifest.

METHOD

Respiratory polysomnography was conducted on 14 medication-free patients with panic disorder and 14 healthy comparison subjects. Semiautomated indices of ventilatory variability were calculated for representative 3-minute, artifact-free sleep samples, and manually scored indices of irregular breathing were rated (blind to diagnosis) for the entire last 2 nights of sleep.

RESULTS

Patients with panic disorder had evidence of abnormal sleep breathing as indicated by increased irregularity in tidal volume during REM and an increased rate of microapneas (i.e., brief [5-10-second] pauses in breathing). A subgroup of patients (including some with recent sleep panic attacks) had indices of subtle disorders in breathing during sleep that were above the 95th percentile for the comparison subjects.

CONCLUSIONS

These findings extend the observations in the awake state that patients with panic disorder breathe more irregularly than healthy comparison subjects. The irregularities may be attributable to altered brainstem sensitivity to CO2 or to other as yet unexplained factors. A possible relationship between irregular nocturnal breathing and sleep panic attacks is discussed.

Nocturnal oximetry: is it a screening tool for sleep disorders?

The objective of this study was to examine the usefulness of home oximetry for the screening of sleep disorders presenting with excessive daytime sleepiness (EDS). This was accomplished by blinded comparison of diagnosis by oximetry alone versus polysomnographic diagnosis carried out at a sleep disorders center at a tertiary referral hospital. This study included three hundred patients who had been referred because of EDS and suspected sleep apnea. A number of measurements were made. The arterial oxygen saturation (SaO2) data were sampled at 2 Hz and stored digitally during polysomnography (PSG). From the SaO2 data recorded onto paper six scorers calculated the number of desaturations > 3% per hour (desaturation index: DI) and then made a diagnosis [normal, DI < 5; mild obstructive sleep apnea (OSA), 5 < DI < 20; moderate OSA, 20 < DI < 40; severe OSA, DI > 40]. Upper airway resistance syndrome (UARS) was diagnosed when DI was < 5 but associated with small fluctuations in SaO2. The diagnosis made by each of six scorers was compared to the clinical diagnosis made independently using PSG. Thirty-one (10.3%) of all the records were rejected by scorers because of inadequate SaO2 signals requiring technologist intervention. Sensitivity of screening for sleep-breathing disorders was 90.0% and specificity was 75.0%. All moderate and severe OSA patients were detected by oximetry. However, among the 66 patients who were classified as normal by oximetry, 1 had mild OSA, 20 had UARS, 9 had periodic limb movements in sleep, 4 had narcolepsy and 2 had a parasomnia. In conclusion, home oximetry may not have sufficient sensitivity and specificity to detect breathing disorders reliably during sleep and is useless for other disorders of sleep.

The effects of posture change and continuous positive airway pressure on cardiac natriuretic peptides in congestive heart failure

We studied changes in the peripheral plasma levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) in seven patients with congestive heart failure (CHF) during four 1-h protocols during which patients maintained either an upright or a supine posture with or without nasal continuous positive airway pressure therapy (N-CPAP) at a pressure of 10 cm H2O (FIO2 = 0.21). The mean plasma ANP concentration of patients increased significantly from baseline at the end of 1 h of recumbency (65.9 +/- 5.8 to 82.6 +/- 8.3 pg/mL (mean +/- standard error); p < 0.05). This increase was prevented by concomitant N-CPAP therapy (72.1 +/- 8.0 to 61.0 +/- 8.8 pg/mL; p = NS). The mean level of ANP decreased significantly (71.9 +/- 9.0 to 62.5 +/- 8.0 pg/mL; p < 0.05) while patients simply maintained an upright posture. A significant reduction was also observed when patients remained upright with accompanying N-CPAP (72.6 +/- 10.9 to 54.6 +/- 4.3 pg/mL; p < 0.05). There were no significant changes observed in the mean level of BNP for any of the protocols undertaken. We conclude that in patients with chronic CHF, (1) an increase in ANP concentration occurs with recumbency, and this can be prevented by N-CPAP therapy; (2) a decrease in ANP occurs with maintenance of an upright posture, and that this reduction may be augmented by N-CPAP; and (3) no net change in BNP concentration occurs with either posture change or N-CPAP.

CPAP titration for sleep apnea using a split-night protocol

We studied 107 patients with sleep-disordered breathing to confirm the effectiveness of continuous positive airway pressure (CPAP) titration using a split-night protocol. Patients spent two consecutive nights in our laboratory with complete polysomnography. On the first night, we applied a split-night protocol; the first half of the night was used as a baseline (B), and after a diagnosis was made, CPAP was applied during the second half of the night (SN). On the second night (2N), patients spent the entire night on CPAP to confirm the effectiveness of CPAP treatment. The SN and 2N both revealed a significant reduction in arousal index (37.8 +/- 27.9 on B, 13.2 +/- 12.1 on SN, 11.4 +/- 8.0 on 2N, values are mean +/- SD, p < 0.001), apnea hypopnea index (AHI) (23.6 +/- 26.3/h on B, 3.0 +/- 3.7/h on SN, 2.4 +/- 2.6/h on 2N, p < 0.001), percent total sleep time below 90% SaO2 (21.0 +/- 27.2% on B, 8.2 +/- 13.8% on SN, 4.9 +/- 10.2% on 2N, p < 0.001), and percent total sleep time below 80% SaO2 (1.1 +/- 3.8% on B, 0.0 +/- 0.1% on SN, 0.1 +/- 0.5% on 2N, p < 0.001). There were no significant differences between the SN and the 2N for these measurements. Final CPAP pressure was significantly lower at the end of the SN when compared with the 2N (8.8 +/- 2.7 cm H2O on SN, vs 10.3 +/- 2.8 cm H2O on 2N, p < 0.001). When patients were divided into three groups (AHI < 20, n = 69; 20 < AHI < 40, n = 18; AHI > 40, n = 20), the final CPAP pressure was different only in the group with AHI < 20 (8.1 +/- 2.3 cm H2O on SN, 9.6 +/- 2.3 cm H2O on 2N, p < 0.001). We conclude that a split-night protocol may be sufficient to determine the effective CPAP pressure, especially in patients with an AHI > 20.

Ventilatory instability in patients with congestive heart failure and nocturnal Cheyne-Stokes breathing

Many of the factors that appear to cause Cheyne-Stokes Breathing (CSB) in sleeping patients with congestive heart failure (CHF) are present during wakefulness. We studied the stability of ventilatory pattern in nine awake CHF patients (left ventricular ejection fraction 9-48%) who demonstrated CSB only while asleep and compared results with 13 age-matched normals. The test involved brief (30-50-second) exposure to hypoxia (end-tidal PO2 = 55 Torr) followed by breathing pure oxygen. During hypoxia, ventilation increased about 40% above air breathing control in both groups, whereas end-tidal CO2 declined to 92% of control in both groups. During hyperoxia, however, breathing pattern differed between groups. In the normals, ventilation gradually declined to air-breathing levels and did not significantly undershoot. In the patients, ventilation dropped more rapidly to baseline and an overshoot was present with ventilation being 72% and air-breathing control at 45 seconds of hyperoxia. Circulatory delay was calculated from the time interval between alveolar hypoxia and in increase in ventilation, and when corrections for circulatory delay were applied to ventilation during hyperoxia the differences between groups increased in that the patients' ventilation was less than baseline immediately after the delay. In the normals, the gradual decline in hyperoxic ventilation probably represents the decay of short-term potentiation (STP) activated by hypoxic hyperventilation. Results in the patients were compatible with absence of such STP decay, but could also have been due to a reduction in ventilatory drive early in hyperoxia related to prolonged circulation times.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of nasal CPAP on nocturnal reflux in patients with aperistaltic esophagus

It has been shown that nasal continuous positive airway pressure (nasal CPAP) significantly reduces nocturnal reflux both in patients with sleep apnea and in patients without sleep apnea but consistent abnormal nocturnal reflux. The mechanism by which CPAP is thought to reduce reflux includes the elevation of the resting lower esophageal sphincter (LES) pressure. In this study, we tested the effect of nasal CPAP in two groups of patients with aperistaltic esophagus but with different resting LES pressure. Seven patients with scleroderma esophagus and six patients treated for achalasia were tested over a 48-h period. On the first night, the patients were untreated; on the second night, both groups received applied nasal CPAP at 8 cm H2O pressure. The percentage of time the pH < 4.0, the number of reflux events > 5 min, and the length of the longest reflux event were all significantly reduced in the patients with achalasia (p < 0.03), but not in the scleroderma group (p > 0.20). These results suggest that a residual resting LES pressure greater than that demonstrated by patients with scleroderma (> 10 mm Hg) may be necessary for nasal CPAP to affect nocturnal reflux.

Acute effect of nasal CPAP on periodic limb movements associated with breathing disorders during sleep

Sleep-disordered breathing is commonly associated with periodic limb movements (PLMS). Nasal continuous positive airway pressure (nCPAP) is the most widely used treatment for sleep-disordered breathing. However, it is not clear whether nCPAP treatment of apnea also has a systematic effect on PLMS. We studied 15 patients with sleep-disordered breathing and PLMS in a split-night protocol in order to confirm the acute effects of nCPAP on PLMS. Although the PLMS index (PLMSI) did not change statistically (baseline, 38.7 +/- 20.5; CPAP, 31.3 +/- 17.0; p = ns), the PLMS-related index (PLMS-ArI) decreased significantly on nCPAP (baseline, 17.8 +/- 10.1; CPAP, 9.2 +/- 5.7; p < 0.05). Whether the reduced PLMS-ArI is sustained with chronic nCPAP is unknown and a matter of future investigation.

Effect of inhaled 3% CO2 on Cheyne-Stokes respiration in congestive heart failure

Cheyne-Stokes respiration (CSR) in severe stable congestive heart failure (CHF) may be associated with significant nocturnal arterial oxygen desaturation and sleep disruption. Previous investigations of inhaled CO2 in CSR have been uncontrolled and of short duration, sleep has not been monitored electroencephalographically, and most patients studied have had neurological disease with or without cardiac disease. The purpose of our study was to document the effects of inhaled CO2 on CSR in patients with severe stable CHF (left ventricular ejection fraction < 35% and NYHA class 3 or 4 dyspnea) in controlled all-night polysomnographic studies. Six patients were studied for 3 nights and days: adaptation, control and inhalation of CO2. These patients received a constant F1CO2 = 0.03 in air (with a 4-5 mm Hg increase in PaCO2) on night 3. This caused virtual abolition of CSR as reflected by CSR duration/total sleep time (62-2.2%; p = 0.0012) and CSR duration/nonrapid eye movement (NREM) sleep time (73-2.4%; p = 0.00064), and NREM apnea index was reduced from 33.5 to zero (p = 0.026). The apparatus used to accurately control F1CO2, however, was intrusive and some features of sleep structure such as sleep latency were adversely affected. We conclude that inhalation of CO2 with a constant F1CO2 = 0.03 virtually eradicates CSR in all-night polysomnographically monitored studies in patients with severe stable CHF. The clinical significance of these findings remains to be determined.

Nasal continuous positive airway pressure. A new treatment for nocturnal gastroesophageal reflux?

Nasal continuous positive airway pressure (CPAP) reduces nocturnal gastroesophageal reflux (GER) in obstructive sleep apnea syndrome (OSAS) patients. The primary objectives of our investigation were to determine if CPAP could reduce reflux in non-OSAS patients and, if so, by what mechanism. Esophageal pH was monitored for 48 h in six nocturnal reflux patients. During the first 24 h, basal reflux data were collected; the second night, nasal CPAP was administered (pressure = 8 cm H2O). Esophageal manometry was obtained in six healthy adult volunteers both on and off nasal CPAP (pressure = 8 cm H2O) to ascertain CPAP's effects on esophageal pressure and peristalsis. The six reflux patients experienced less nocturnal GER while on CPAP. The mean percent time esophageal pH < 4 was reduced from 27.7 +/- 10.0 to 5.8 +/- 2.6 (p < 0.004); the mean reflux duration dropped from 2.1 +/- 0.6 to 0.9 +/- 0.5 min (p < 0.03); and the mean duration of longest reflux improved from 84.3 +/- 32.6 to 13.8 +/- 6.9 min (p < 0.01). The CPAP raised the mean resting midesophageal pressure by 4.4 cm H2O (p < 0.01) and the mean resting lower esophageal pressure (LES) by 13.2 cm H2O (p < 0.02) in the healthy volunteers. Nasal CPAP effectively reduced nocturnal GER in six patients with nocturnal reflux. The antireflux activity of CPAP is likely due to passive elevation of intraesophageal pressure and possibly to reflex LES constriction.

Benzodiazepines in congestive heart failure: effects of temazepam on arousability and Cheyne-Stokes respiration

We studied seven male patients with moderate to severe congestive heart failure (CHF) [left ventricular ejection fraction (LVEF) = 22.4 +/- 6.7; mean +/- SD] in a double-blind crossover trial to determine the effects of temazepam 15 mg on arousability, sleep architecture, Cheyne-Stokes respiration (CSR) and nighttime oxygen saturation. Sleep architecture was not markedly improved with temazepam. There was no significant change in total sleep time (TST) (383.1 +/- 14.1 minutes to 396.6 +/- 15.4 minutes, p = ns) (mean +/- SE, placebo vs. temazepam) or total wake time (TWT) (96.9 +/- 14.0 vs. 81.4 +/- 14.0 minutes, p = ns). Sleep stage proportions did not change appreciably except for a reduction in stage 1 sleep (6.7 +/- 1.2% vs. 4.0 +/- 1.0%, p < 0.05). Microarousals per hour of sleep decreased with temazepam (21.1 +/- 2.7/hour vs. 13.9 +/- 2.1/hour placebo, p < 0.05), with the largest change occurring in stage 2 (24.9 +/- 5.4/hour vs. 15.0 +/- 3.1/hour, p < 0.05). Wake time during sleep (WDS) was reduced from 82.5 +/- 11.7 minutes to 54.5 +/- 9.4 minutes, p < 0.03. Daytime alertness was improved with temazepam as was indicated by an increase in mean latency to sleep [multiple sleep latency test (MSLT) = 7.1 +/- 2.4 vs. 5.7 +/- 2.0 minutes, p < 0.04) on days following treatment with temazepam. There was no significant change in CSR as a percentage of TST (38.7 +/- 13.6% vs. 32.5 +/- 11.8%, p = ns). However, the apnea/hypopnea index (AHI) (10% filter) was decreased in stage 1 (28.1 +/- 9.7/hour vs. 15.6 +/- 8.2/hour). Overnight oxygen saturation did not change with temazepam (95.1 +/- 0.6% both nights) and the percentage of TST spent below 90% oxygen saturation was minimal for both conditions (1.5 +/- 1.1% vs. 2.2 +/- 1.7%, p = ns). We conclude that CHF patients with CSR experience frequent arousals and that these arousals can be reduced with temazepam. There was an improvement in daytime somnolence. There was no worsening of nighttime oxygen saturation.

Effects of zolpidem and triazolam on sleep and respiration in mild to moderate chronic obstructive pulmonary disease

Sleep problems and nocturnal arterial oxygen desaturation are common in patients with chronic obstructive pulmonary disease (COPD). Hence, the safety and efficacy of new hypnotic agents must be ascertained in this group of patients. We performed a double-blind, randomized, single-dose, placebo and active drug controlled, crossover study in 24 patients with insomnia (subjective sleep latency > 30 minutes and sleep duration 4-6 hours) and mild to moderate COPD (mean FEV1 61 +/- 12(SD)% predicted) in order to establish the effects of zolpidem 5 mg and 10 mg on sleep and respiration and to compare these effects with triazolam 0.25 mg. Arterial oxygen saturation for the entire night, by hour and stage, and the apnea-hypopnea index for the entire night were not significantly different with placebo and the various drug conditions. Total sleep time and sleep efficiency were increased over placebo by all three drug conditions. Triazolam was more effective than zolpidem 5 mg but not zolpidem 10 mg, and there was no significant difference between zolpidem 5 mg and zolpidem 10 mg. Zolpidem 10 mg and triazolam both reduced the number of awakenings (> 15 seconds duration) per hour of sleep. Although there was a trend for triazolam to be more efficacious than zolpidem 10 mg, no statistically significant difference was found for any objective or subjective sleep variable. Likewise, zolpidem 10 mg tended to be more efficacious than zolpidem 5 mg, but the difference was only significant in terms of perceived sleep quality and ease of falling asleep.(ABSTRACT TRUNCATED AT 250 WORDS)

Sleep in nondepressed patients with panic disorder: II. Polysomnographic assessment of sleep architecture and sleep continuity

This study assessed the EEG sleep of 16 patients with panic disorder who did not currently meet criteria for major depression in comparison to 16 age-comparable healthy controls. Patients with panic disorder had remarkably normal sleep, with only a modest reduction in total sleep time (374 +/- 46 min vs. 399 +/- 36 min) and delta sleep (11.4 +/- 6.2% vs. 16.4 +/- 6.6%) noted. Contrary to expectation, impairment in sleep maintenance and continuity was not found in the patients with panic disorder. We conclude (a) sleep in non-depressed patients with panic disorder is fairly unremarkable, and does not resemble that classically described for depressed patients, and (b) excessive arousability is not a characteristic feature of sleep in panic disorder.

Management of obstructive sleep apnea

Although the indications for treatment of obstructive sleep apnea are controversial, there is general agreement that treatment is warranted in patients with a combined apnea and hypopnea frequency of 20 events per hour of sleep. General therapeutic measures include abstinence from alcohol and weight loss in obese patients. A minority of patients with specific abnormalities of the nose, pharynx, or jaw may require surgical management. In the absence of specific upper airway abnormalities, the most effective treatment is nasal continuous positive airway pressure or, if necessary, bilevel positive airway pressure during sleep. The role of uvulopalatopharyngoplasty remains controversial, due in part to the reported variability in long-term efficacy of this procedure. Drug therapy may be effective in selected patients.

Short technical note: quantification of periodic breathing: preliminary studies

Although the apnea/hypopnea index is the most widely used measure of breathing pattern abnormality during sleep, this index gives no information about the strength of the oscillation in the breathing pattern, its periodicity or its regularity. Such information may be required in research studies involving breathing patterns and how they are affected by interventions. We are exploring spectral analytic methods to determine two normalized indices, the periodicity index and the modified modulation index, to examine periodic breathing for all-night sleep studies. These methods are automatic and require no user interaction. Data were obtained from 11 heart failure patients who slept for a total of 21 nights in the sleep laboratory. Because individual patients had a marked regularity of their Cheyne-Stokes respiration during sleep, one would expect an extremely high correlation between the traditional measures of breathing pattern abnormality and these spectral analytic techniques. Indeed we found that there was an extremely high correlation between the periodicity index and the modulation index and the traditional measures of apnea/hypopnea index and the proportion of the night with periodic breathing (p less than 0.02 in all cases). When the breathing pattern was irregular but still with many apneas there was a discrepancy between the apnea index and the indices of periodicity. These techniques are still preliminary and future studies will determine their limitations in other patient populations and where the pattern is unstable.

Nasal CPAP reduces gastroesophageal reflux in obstructive sleep apnea syndrome

Anecdotal reports suggest that obstructive sleep apnea syndrome (OSAS) patients may suffer from frequent nocturnal gastroesophageal reflux (GER) and that nasal continuous positive airway pressure may be an effective form of antireflux therapy in this population. To confirm these clinical impressions, we performed two consecutive days of 24-h esophageal pH monitoring, nocturnal esophageal pressure recording, and polysomnography on six OSAS patients complaining of regular nocturnal GER. On night one, the patients were untreated. Five of six subjects had abnormal amounts of nocturnal GER. Arousal, movement and swallowing were more frequent (p less than 0.043) and nadir intrathoracic pressure lower (p less than 0.005) in the 30 s prior to precipitous drops in esophageal pH (greater than or equal to 2 pH units) than during random control periods. A direct association between obstructive apneas and GER was not identified. On night two, nasal CPAP was administered and successfully treated apnea in five of six subjects. In these patients, there was also dramatic reduction in GER frequency and duration on CPAP. The mean percentage of time pH less than 4 dropped from 6.3 +/- 2.1 to 0.1 +/- 0.1 percent (p less than 0.025). We believe that OSAS may predispose to nocturnal GER by lowering intrathoracic pressure and increasing arousal and movement frequency. Nasal CPAP can correct these predisposing factors and reduce GER.

Cheyne-Stokes respiration: Stability of interacting systems in heart failure

Cheyne-Stokes respiration, a breathing pattern found in patients with heart failure, is characterized by periodic changes in ventilation. This pattern of breathing is also associated with oscillations in the arousal state, blood oxygen level, carbon dioxide blood level, and the blood pressure. Although originally described as an irregular breathing pattern or an unstable breathing pattern, Cheyne-Stokes respiration may be quite stable for prolonged periods of time. This breathing pattern may represent a clinical disorder in which disease results in a low-frequency oscillation of the system. Treatment that either reduces or abolishes the oscillation results in clinical improvement because of reduced oscillation of the systems whose function is linked to the changes in ventilation.

Subjective versus objective evaluation of hypnotic efficacy: experience with zolpidem

There is little published literature on the correlation between subjective and objective efficacy of hypnotics. We wanted to determine whether there was a correlation between the patient's subjective evaluation of the efficacy of the hypnotic with the polysomnographic (PSG) findings. We studied 16 patients with chronic insomnia (sleep latency, greater than or equal to 30 minutes; total sleep time, greater than 240 but less than 420 minutes) for 11 nights who took placebos on nights 1 and 2, zolpidem (imidazopyridine) on nights 3-9 and placebo on nights 10 and 11. Patients completed a questionnaire each morning following PSG, which evaluated subjective sleep quality, sleep latency and total sleep time. These data were compared to PSG findings to answer specific questions about sleep latency reduction, efficacy of the hypnotic after a week's use, sleep quality after discontinuing the drug, and any correlation between subjective and objective measures. PSG findings indicated a shortened sleep latency, increased total sleep time, decreased total wake time and increased sleep efficiency when patients ingested zolpidem 30 minutes before bedtime. We found that after 7 nights (nights 3-9) the drug was still effective in reducing sleep latency and increasing total sleep time. Upon withdrawal (nights 10 and 11) sleep returned to baseline (nights 1 and 2). Subjectively, the patients confirmed those findings on the questionnaire, as well as a subjective reduction in the number of awakenings and, interestingly, a subjective increase in the time spent awake after sleep. Many of the objective variables we examined correlated highly with the subjective variables. While on zolpidem, subjects believed and were objectively shown to have a decreased sleep latency, increased total sleep time and decreased time awake before persistent sleep, although they tended to overestimate sleep latency and time spent awake before persistent sleep and underestimated total sleep time. Although the correlation between objective and subjective measures was high for the group, in individual patients there was an impressive difference between the two, and the highest coefficient of variation between a subjective and objective measures was 0.453. No correlations were found with subjective measures of refreshing quality of sleep, decrease in number of awakenings, how sleepy patients felt in the morning or their ability to concentrate in the morning. Thus, we believe the PSG remains the keystone in the evaluation of hypnotic efficacy.

Central sleep apnoea in congenital muscular dystrophy

Sleep-disordered breathing may occur in a wide variety of neuromuscular syndromes, and may present with diverse, often isolated, symptoms or findings such as excessive daytime sleepiness, pulmonary hypertension, congestive heart failure, morning headaches, or hypoxia-induced nocturnal seizures. The authors report two sisters with congenital muscular dystrophy in whom central sleep apnoea resulted in the isolated symptom of nocturnal seizures in one, and morning headaches in the other. Review of the literature reveals that sleep-disordered breathing may be common in neuromuscular disorders, and may often be present when clinical weakness is mild, and insufficient to result in diurnal respiratory dysfunction.

The entrainment of low frequency breathing periodicity

It has been predicted by mathematical models of the respiratory control system that the delay between the lung and the respiratory controller may determine the cycle time found in periodic breathing. We examined cycle time of periodic breathing and circulation time in 11 patients known to have circulation delay due to heart failure. We did not find a significant relationship between the amount of periodic breathing and circulation delay, but found a very high correlation between circulation delay and the cycle time of periodic breathing (r2 = 0.825; p = 0.0001).

Sleep in postpolio syndrome

Post-polio patients may develop additional neuromuscular and respiratory symptoms decades after the acute attack, the post-polio syndrome. We hypothesize some post-polio symptoms may be due to breathing disorders occurring during sleep. We performed polysomnography on 13 post-polio patients: group 1 (five patients) were those already on ventilatory assistance (rocking beds) and group 2 (eight patients), those without any assistance. Patients requiring new treatment were then evaluated on nasal CPAP or nasal mask ventilation. Group 1 patients, on rocking beds, demonstrated consistently poor sleep quality with decreased total sleep time, sleep efficiency, percentage stage 2, slow wave sleep, rapid eye movement sleep and an increase in the number of arousals and percentage stage 1 sleep. Respiratory abnormalities were also present and in all cases caused significant O2 desaturation. These patients did not respond to CPAP with the rocking bed. Repeat night-time polysomnography on nasal mask ventilation demonstrated an improvement in sleep structure and gas exchange. Three group 2 patients, (group 2a) had sleep within normal limits. The five remaining (group 2b) had poor sleep quality that was similar to but not as disrupted as group 1 patients. All but one patient demonstrated obstructive or mixed apnea and were treated effectively with nasal CPAP. One patient required nasal mask ventilation (due to mixed apnea and marked hypoventilation) to which there was a dramatic response. These patients demonstrated improved sleep quality and an improvement in daytime symptomatology. Sleep studies should be performed on post-polio patients with excessive daytime sleepiness and respiratory complaints. Those with obstructive and mixed apnea can often be treated with nasal CPAP. Those with hypoventilation syndrome and sleep apnea attributable to sleepiness and respiratory complaints. Those with obstructive and mixed apnea can often be treated with nasal CPAP. Those with hypoventilation syndrome and sleep apnea attributable to respiratory muscle weakness can be treated with nasal mask ventilation. Individuals already on respiratory assistance such as rocking beds who have features of respiratory failure can also be treated effectively with long-term nasal mechanical ventilation.

The effect of oxygen on respiration and sleep in patients with congestive heart failure

STUDY OBJECTIVE

To determine the effect of supplemental oxygen on Cheyne-Stokes respiration, nocturnal oxygen saturation (SaO2), and sleep in male patients with severe, stable congestive heart failure.

DESIGN

Randomized, single-blind, placebo-controlled crossover study.

SETTING

Patients referred from outpatient cardiology clinics of two teaching hospitals.

PATIENTS

Sequential sample of nine outpatients with severe, stable congestive heart failure.

INTERVENTIONS

For each patient, sleep studies (after an adaptation night) from two consecutive randomized nights were compared; one study was done while the patient breathed compressed air and the other while the patient breathed oxygen (O2). Compressed air and oxygen were both administered through nasal cannulae at 2 to 3 L/min.

MEASUREMENTS AND MAIN RESULTS

Cheyne-Stokes respiration, defined as periodic breathing with apnea or hypopnea, was found in all patients. Low-flow oxygen significantly reduced the duration of Cheyne-Stokes respiration (50.7% +/- 12.0% to 24.2% +/- 5.4% total sleep time), mainly during stage 1 NREM (non-rapid eye movement) sleep (21.3% +/- 7.1% to 6.7% +/- 2.3% total sleep time) with no significant change during stage 2 sleep, slow-wave sleep, or REM (rapid eye movement) sleep. Although patients had normal SaO2 (96.0% +/- 1.7%) while awake, severe sleep hypoxemia was common; breathing oxygen reduced the amount of time that SaO2 was less than 90% from 22.3% +/- 8.0% to 2.41% +/- 1.93% of total sleep time. Sleep, disrupted to a variable extent in all patients, improved with oxygen therapy: There was an increase in total sleep time from 275.3 min +/- 36.6 to 324.6 min +/- 23.3; a reduction in the proportion of stage 1 sleep (27.6% +/- 5.8% total sleep time to 15.2% +/- 2.6% total sleep time); and a reduction in the number of arousals (30.4/h +/- 8.0 to 13.8/h +/- 1.9). The apnea-hypopnea index was reduced from 30.0 +/- 4.7 to 18.9 +/- 2.4 with oxygen breathing.

CONCLUSION

In severe, stable congestive heart failure, nocturnal oxygen therapy reduces Cheyne-Stokes respiration, corrects hypoxemia, and consolidates sleep by reducing arousals caused by the hyperpneic phase of Cheyne-Stokes respiration. Correction of nocturnal hypoxemia and sleep disruption may improve the clinical status of these patients.

Respiration and abnormal sleep in patients with congestive heart failure

We investigated the interaction between respiration and sleep in ten male outpatients with severe, stable, maximally treated congestive heart failure (CHF). Cheyne-Stokes respiration (CSR), defined as periodic breathing with apnea or hypopnea, was found in all patients with a mean duration of 120 +/- 87 minutes [50.2 +/- 34.4 percent total sleep time (TST)]. The CSR was found predominantly during stage 1 (20.6 +/- 6.7 percent TST) and stage 2 (25.8 +/- 6 percent TST) NREM sleep and occurred rarely during slow wave sleep (SWS) (1.6 +/- 1 percent TST) and REM sleep (1.6 +/- 0.5 percent TST). All apneas and hypopneas were central. Despite normal awake arterial oxygenation (SaO2) (96.1 +/- 1.6 percent), significant, severe hypoxemia was found during sleep in seven patients with SaO2 less than 90 percent for 9 to 59 percent TST (mean +/- SD, 23 +/- 23 percent TST), and this was significantly related to the duration of CSR (r = 0.66, p less than 0.05). The mean minimum SaO2 for sleep stage was lowest during stage 1 (82.1 percent +/- 2.6 percent) and stage 2 (78.9 percent +/- 2.8 percent) NREM sleep, intermediate during REM sleep (84.5 percent +/- 1.8 percent) and highest during SWS (87.6 percent +/- 2.7 percent). Sleep was disrupted to a variable extent in all patients with a short mean TST (287 +/- 106 minutes), a high proportion of stage 1 sleep (26 +/- 19 percent TST), virtual absence of SWS (5 +/- 7 percent TST) which was found in only four patients, and a high number of sleep stage changes (30 +/- 27/hour) and arousals (28 +/- 25/hour). Arousals occurred predominantly during stage 1 (17 +/- 20/hour) and stage 2 (10 +/- 7/hour) NREM sleep and the majority immediately followed the hyperpneic phase of CSR. The amount of CSR (percent TST) was inversely related to the length of TST (r = -0.73, p less than 0.05), and directly related to the number of sleep stage changes (r = 0.79, p less than 0.01) and the number of arousals (r = 0.66, p less than 0.05). We conclude that in severe, stable CHF, CSR occurs predominantly during light sleep, that despite normal awake arterial oxygen saturation, significant hypoxemia may develop during sleep due to CSR, and that sleep is unstable and disrupted due to frequent arousals caused by the hyperpneic phase of CSR. These sequelae of CSR may be important determinants of the clinical status and outcome of patients with severe CHF.