急性脑血管病与睡眠呼吸障碍的关系研究

目的　探讨急性脑血管病与睡眠呼吸障碍(SDB)的关系。方法　利用多导睡眠图(PSG)对86例急性脑血管病患者进行睡眠全程监测,并选择年龄、性别和体重指数(BMI)相当的健康体检者50例作为正常对照组。结果　研究组睡眠结构紊乱,表现为睡眠效率降低、深睡期和快速眼动(REM)睡眠时间减少、浅睡时间延长,与正常对照组比较,均有显著性差异(均为P<0. 01);同时与正常对照组比较,研究组夜间鼾声指数和呼吸紊乱指数(RDI)明显增高(均为P<0. 01),氧减指数(ODI)和动脉血氧饱和度(SaO2 )明显降低(均为P<0. 01),其中58例(67. 44% )诊断为阻塞性睡眠呼吸暂停综合征。研究组中睡眠发病率明显高于清晨觉醒后和活动时(均为P<0. 01)。结论　睡眠呼吸障碍,尤其是阻塞性睡眠呼吸暂停(OSA)与急性脑血管病的关系密切,既是其发病的独立危险因素,又是其结果;早期诊治睡眠呼吸障碍对于脑血管病的预防、治疗和康复有重要意义。     

Pilot study assessing the impact of intrathecal baclofen administration mode on sleep-related respiratory parameters

Bensmail D, Marquer A, Roche N, Godard A-L, Lofaso F, Quera-Salva M-A. Pilot study assessing the impact of intrathecal baclofen administration mode on sleep-related respiratory parameters.ObjectiveTo assess the impact of intrathecal baclofen (ITB) mode of administration on sleep and sleep-related breathing events in severely disabled patients with severe spasticity.DesignOpen prospective trial.SettingPhysical medicine and rehabilitation department.ParticipantsPatients (N=11) treated with ITB pump for severe spasticity.InterventionAssessment of patients' sleep before and after ITB pump implantation, and comparison of polysomnography results after continuous or bolus mode of administration of ITB.Main Outcome MeasuresPolysomnography and sleep-related breathing events.ResultsITB reduced periodic limb movements and increased the respiratory disturbance index (RDI) and central apneas in our population of patients. This study showed that ITB mode of administration may affect sleep-disordered breathing. Indeed, we observed a significant increase of respiratory events in the bolus condition (RDI and central apneas). In contrast, continuous infusion did not induce a significant modification of sleep-disordered breathing. When a sleep apnea syndrome was preexisting, it was generally severely worsened by the bolus mode of administration.ConclusionsThese results indicate that sleep function and sleep-related respiratory events should be assessed before ITB pump implantation. It is probably better to use a continuous mode of infusion if patients have preexisting sleep-disordered breathing.     

Sleep apnea in adults with traumatic brain injury: a preliminary investigation

OBJECTIVE: To determine the occurrence and nature of sleep-related breathing disorders in adults with traumatic brain injury (TBI). DESIGN: Prospective, observational, consecutive sample enrollment of subjects admitted for rehabilitation after TBI. SETTING: Inpatient rehabilitation and subacute rehabilitation units of a tertiary care university medical system. PARTICIPANTS: Subjects (n = 28) included adults with TBI and a Rancho Los Amigos Scale level of 3 or greater who were less than 3 months postinjury and admitted for comprehensive inpatient rehabilitation. INTERVENTIONS: Overnight sleep study using portable 6-channel monitoring system. MAIN OUTCOME MEASURE: Respiratory disturbance index (RDI), which is the number of apneic and hypopneic episodes per hour of sleep. RESULTS: Evidence of sleep apnea was found in 10 of 28 (36%) subjects as measured by a RDI level of 5 or greater and in 3 of 28 (11%) subjects as measured by a RDI level of 10 or greater. This rate of sleep apnea is significantly (p =.002) higher than would be predicted based on population norms. No correlation was found between the occurrence of significant sleep apnea and measures of TBI severity or other demographic variables. Sleep-related breathing disorders were primarily central though obstructive apneas were also noted. CONCLUSION: In this preliminary investigation, sleep-related breathing disorders as defined by a respiratory disturbance index of 5 or greater appears to be common in adult subjects with TBI.     

Insulin resistance,the metabolic syndrome,and risk of incident cardiovascular disease in nondiabetic american indians: the Strong Heart Study

OBJECTIVE: Insulin resistance (IR) and the metabolic syndrome (MS) are associated with type 2 diabetes and adverse cardiovascular disease (CVD) risk factor profiles. Whether IR and MS predict CVD independently of diabetes and other CVD risk factors is not known. This study examines whether IR and/or presence of MS are independently associated with CVD in nondiabetic American Indians (AI). RESEARCH DESIGN AND METHODS: We examined 2283 nondiabetic AI who were free of CVD at the baseline examination of the Strong Heart Study (SHS). CVD risk factors were measured, IR was quantified using the homeostasis model assessment (HOMA), and MS as defined by the National Cholesterol Education Program Adult Treatment Panel (ATP III) was assessed for each participant. Incident CVD and diabetes were ascertained during follow-up. RESULTS: MS was present in 798 individuals (35%), and 181 participants (7.9%) developed CVD over 7.6 +/- 1.8 years of follow-up. Age, BMI, waist circumference, and triglyceride levels increased and HDL cholesterol decreased across tertiles of HOMA-IR. Risk of diabetes increased as a function of baseline HOMA-IR (6.3, 14.6, and 30.1%; P < 0.001) and MS (12.8 vs. 24.5%). In Cox models adjusted for CVD risk factors, risk of CVD did not increase either as a function of baseline HOMA-IR or MS, but individual CVD risk factors predicted subsequent CVD. CONCLUSIONS: Among nondiabetic AI in the SHS, HOMA-IR and MS both predict diabetes, but neither predicts CVD independently of other established CVD risk factors.     

Lower toenail chromium in men with diabetes and cardiovascular disease compared with healthy men

OBJECTIVE: Chromium may improve insulin sensitivity, which can modify the risk of diabetes and cardiovascular disease (CVD). Therefore, we evaluated the association between toenail chromium and CVD in diabetic men. RESEARCH DESIGN AND METHODS: We performed cross-sectional and nested case-control analyses among men aged 40-75 years within the Health Professionals Follow-up Study. The cross-sectional analysis compared men with diabetes only (n = 688), diabetes with prevalent CVD (n = 198), and healthy control subjects (n = 361). The nested case-control study included 202 men with baseline diabetes who developed incident CVD and 361 matched control subjects. RESULTS: Mean toenail chromium (microg/g) was 0.71 in healthy control subjects, 0.61 in diabetes-only subjects, and 0.52 in diabetic subjects with prevalent CVD (P for trend = 0.003). In the cross-sectional analysis, the multivariate odds ratio (OR) between extreme quartiles was 0.74 (95% CI 0.49-1.11; P for trend = 0.18), comparing diabetes only with healthy control subjects. A similar comparison between diabetic subjects with prevalent CVD and healthy control subjects yielded an OR of 0.45 (0.24-0.84; P for trend = 0.003). In the nested case-control study, comparing diabetic men with incident CVD with healthy control subjects, the multivariate OR was 0.65 (0.36-1.17; P for trend = 0.16) between extreme quartiles. When we combined prevalent and incident CVD cases among diabetic men and compared them with healthy control subjects, the OR was 0.62 (0.39-1.01; P for trend = 0.02) between extreme quartiles. CONCLUSIONS: Our results suggest that diabetic men with CVD have lower toenail chromium than healthy control subjects. However, this study could not distinguish between the effects of chromium on diabetes and those on CVD. Long-term clinical trials are needed to determine whether chromium supplementation is beneficial for preventing CVD among diabetic patients.     

Relation of lower-extremity amputation to all-cause and cardiovascular disease mortality in American Indians: the Strong Heart Study

OBJECTIVE: To compare risk of all-cause and cardiovascular disease (CVD) mortality in people with a lower-extremity amputation (LEA) attributable to diabetes and people without an LEA. RESEARCH DESIGN AND METHODS: The Strong Heart Study is a study of CVD and its risk factors in 13 American-Indian communities. LEA was ascertained at baseline by direct examination of the legs and feet. Mortality surveillance is complete through 2000. RESULTS: Of 2,108 participants with diabetes at baseline, 134 participants (6.4%) had an LEA. Abnormal ankle-brachial index (53%), albuminuria (87%), and long diabetes duration (mean 19.8 years) were common among diabetic subjects with LEA. Mean diabetes duration among diabetic participants without LEA and in those with toe and below-the-knee amputations was 11.9, 18.6, and 21.1 years, respectively. During 8.7 (+/-2.9) years of follow-up, 102 of the participants with LEA (76%) died from all causes and 35 (26%) died from CVD. Of the 1,974 diabetic participants without LEA at baseline, 604 (31%) died from all causes and 206 (10%) died from CVD. The unadjusted hazard ratios (HRs) for all-cause and CVD mortality in diabetic participants with LEA compared with those without were 4.0 and 4.1, respectively. Adjusting for known and suspected confounders, LEA persisted as a predictor of all-cause (HR 2.2, 95% CI 1.7-2.9) and CVD mortality (HR 1.9, 95% CI 1.3-2.9). We observed a significant interaction between baseline LEA and sex on CVD mortality, with female sex conferring added risk of CVD mortality. CONCLUSIONS: LEA is a potent predictor of all-cause and CVD mortality in diabetic American Indians. The combination of female sex and LEA is associated with greater risk of CVD mortality than either factor alone.     

Sleep-disordered breathing in patients with heart failure: pathophysiology, assessment, and management

PURPOSE: To provide clinicians in primary care settings information on the effects of sleep-disordered breathing in patients with heart failure (HF). Assessment and screening tools, as well as management considerations, are presented. DATA SOURCES: Review of the scientific literature of the past 10 years, along with classic studies and Internet sources. CONCLUSIONS: HF is an increasingly prevalent problem with a high degree of associated sleep-disordered breathing. There are two broad categories of sleep-disordered breathing: obstructive sleep apnea and central sleep apnea/Cheyne-Stokes breathing. Both of these occur on a continuum of mild hypopnea to severe apnea with hypoxia. Sleep apneas are particularly harmful to patients with HF and, if left untreated, may adversely affect their prognosis. Yet sleep apnea is not routinely screened for in this population. IMPLICATIONS FOR PRACTICE: Given the serious consequences of untreated sleep-disordered breathing, there is sound justification to screen for sleep apnea in all patients with HF. Subsequent treatment of those patients with sleep apnea can significantly improve their quality of life and can decrease their mortality.     

Coronary heart disease risk equivalence in diabetes depends on concomitant risk factors

OBJECTIVE: Diabetes has been defined as a coronary heart disease (CHD) risk equivalent, and more aggressive treatment goals have been proposed for diabetic patients. RESEARCH DESIGN AND METHODS: We studied the influence of single and multiple risk factors on the 10-year cumulative incidence of fatal and nonfatal CHD and cardiovascular disease (CVD) in diabetic and nondiabetic men and women, with and without baseline CHD or CVD, in a population (n = 4,549) with a high prevalence of diabetes. RESULTS: In both sexes, diabetes increased the risk for CHD (hazard ratio 1.99 and 2.93 for men and women, respectively). Diabetic men and women had a 10-year cumulative incidence of CHD of 25.9 and 19.1%, respectively, compared with 57.4 and 58.4% for nondiabetic men and women with previous CHD. The pattern was similar when only fatal events were considered. Diabetic individuals with one or two risk factors had a 10-year cumulative incidence of CHD that was only 1.4 times higher than that of nondiabetic individuals (14%). However, the 10-year incidence of CHD in diabetic subjects with multiple risk factors was >40%, and the incidence of fatal CHD was higher in these subjects than in nondiabetic subjects with previous CHD. Data for CVD showed similar patterns, as did separate analyses by sex. CONCLUSIONS: Our results and comparisons with other available data show wide variation in the rate of CHD in diabetes, depending on the population and existing risk factors. Most individuals had a 10-year cumulative incidence >20%, but only those with multiple risk factors had a 10-year cumulative incidence that was equivalent to that of patients with CHD. Until more data are available, it may be prudent to consider targets based on the entire risk factor profile rather than just the presence of diabetes.     

Sleep disturbances and their relationship to glucose tolerance in pregnancy

OBJECTIVE

To explore relationships among sleep disturbances, glucose tolerance, and pregnancy outcomes.

RESEARCH DESIGN AND METHODS

Four validated sleep questionnaires were administered to 169 pregnant women at the time of 50-g oral glucose tolerance testing (OGTT) during the second trimester. Pregnancy outcomes were analyzed in 108 women with normal glucose tolerance (NGT).

RESULTS

Of the participants, 41% had excessive daytime sleepiness (Epworth Sleepiness Scale [ESS] >8); 64% had poor sleep quality; 25% snored frequently; 29% had increased risk of sleep-disordered breathing (SDB); 52% experienced short sleep (SS); 19% had both increased SDB risk and SS (SDB/SS); and 14% had daytime dysfunction. Reported sleep duration inversely correlated with glucose values from 50-g OGTT (r = −0.21, P < 0.01). Each hour of reduced sleep time was associated with a 4% increase in glucose levels. Increased likelihood of gestational diabetes mellitus (GDM) was found in subjects with increased SDB risk (odds ratio 3.0 [95% CI 1.2–7.4]), SS (2.4 [1.0–5.9]), SDB/SS (3.4 [1.3–8.7]), and frequent snoring (3.4 [1.3–8.8], after adjustment for BMI). Among NGT subjects, preterm delivery was more frequent in those with increased ESS (P = 0.02), poor sleep quality (P = 0.02), and SS (P = 0.03). Neonatal intensive care unit admissions were associated with increased ESS (P = 0.03), SDB/SS (P = 0.03), and daytime dysfunction (P < 0.01) in mothers.

CONCLUSIONS

Pregnant women experience significant sleep disturbances that are associated with increased risk of GDM and unfavorable pregnancy outcomes. Pregnant women with increased SDB risk, frequent snoring, and sleep duration of <7 h/night have increased risk of developing GDM.Sleep-disordered breathing (SDB) is present in 24% of men and 9% of women in the U.S. population (1) and has been linked to insulin resistance and type 2 diabetes (2–5). Recent studies reveal that SDB is present in up to 86% of patients with type 2 diabetes (6,7). SDB severity has been associated with poorer glucose control (6).Decreases in both duration and quality of sleep are common in pregnant women as a result of hormonal and physical factors (8,9). Collectively, these disorders have been termed pregnancy-associated sleep disorders by the International Classification of Sleep Disorders (10).Prospective studies show that SDB symptoms increase during pregnancy (11). SDB in pregnancy has been associated with preeclampsia, intrauterine growth retardation, and preterm delivery (12,13). A few recent studies using questionnaires that variably assess snoring, SDB symptoms, and/or sleep duration report an association between short sleep (SS) and/or frequent snoring and glucose intolerance and gestational diabetes mellitus (GDM) (14–16).We used four validated sleep questionnaires to obtain a comprehensive evaluation of sleep duration and quality and assess associations with glucose tolerance and pregnancy outcomes.     

Sleep-Disordered Breathing in 2 Pediatric Patients on Peritoneal Dialysis

Sleep-disordered breathing (SDB) is prevalent in children with chronic kidney disease (CKD), and has the potential to worsen vascular and neuro-cognitive health and quality of life. We present 2 children with CKD who experience central sleep apnea and nocturnal hypoventilation and discuss the possible underlying mechanisms in relation to CKD and dialysis.     

Central sleep apnea

Central sleep apnea (CSA) is characterized by the periodic occurrence of apnea caused by loss of ventilatory motor output. CSA is often discussed as a minor variant of obstructive sleep apnea.However, this view obscures the critical contribution of CSA as an important manifestation of breathing instability in a variety of conditions with diverse causes. Central apnea can also be a physiologic phenomenon in healthy people during sleep onset. Conversely, patients who have obstructive apnea may also develop episodes of apparent central apnea, and apneas that begin as central may become obstructive as respiratory effort is restored ("mixed apneas"). Thus, there is a significant overlap between obstructive and central apnea. This article addresses the pathophysiology, clinical features, and management of normocapnic and hypercapnic CSA.     

Evaluation of variables to characterize respiratory periodicity during sleep in older adults

Reliable markers of early neurological decline might guide interventions to prevent or reverse cognitive decline in older adults. Because cognitive decline is associated with hypoxemia during sleep, the authors examined 3 respiratory periodicity variables in 5 older adults. Subjects were monitored overnight using standard polysomnography. From the inductance band signal, the authors calculated the variability in duration of breathing cycles measured by standard deviation of interbreath intervals (sdIBI), frequency of breathing cycles measured by standard deviation of interbreath frequencies (sdIBF), and amplitude of breathing cycles measured by standard deviation of breathing cycle amplitudes (sdAMP). Logistic regression analysis and kappa coefficients identified variables that reliably detected 5-minute segments having central or obstructive apneas or body movements. An sdIBF > or = 4.5 cpm identified body movements (sensitivity = 0.96, specificity = 0.96, kappa = 0.90). An sdIBI > 1.2 seconds identified central apneas (sensitivity = 0.86, specificity = 0.99, kappa = 0.86), and an sdIBI > or = 1.68 seconds identified segments with 3 central apneas (sensitivity = 0.90, specificity = 0.89, kappa = 0.89). An sdAMP > or = 0.1 V and an sdIBF > or = 1.5 cpm identified obstructive apneas (kappa = 0.91). Data support the potential of these variables to identify central and obstructive apneas and to classify individuals according to different patterns of respiratory periodicity.     

Effects of long-term nocturnal oxygen treatment in patients with severe heart failure

Sleep-disordered breathing (SDB) is common in patients with heart failure (HF) and leads to disturbed sleep. The objective of this study was to determine the persistent effects of long-term nocturnal oxygen treatment in patients with severe HF regarding (1) objective outcomes, such as sleep, SDB, cardiac function, and functional capacity; (2) subjective outcomes, such as self-assessed sleep difficulties, daytime sleepiness, and health-related quality of life (HRQOL); and (3) the relationship between objective and subjective outcomes. In this open nonrandomized experimental study, 22 patients, median age 71 years, with severe HF were studied before and after 3 months of receiving nocturnal oxygen. The measures used were overnight polysomnography, echocardiography, 6-minute walk test, self-assessed sleep difficulties (Uppsala Sleep Inventory-HF), daytime sleepiness (Epworth Sleepiness Scale), and HRQOL (36-Item Short Form Health Survey and Minnesota Living with Heart Failure Questionnaire). SDB, with a 90% dominance of central sleep apnea, occurred in 41% of the patients with severe HF before intervention. After intervention, functional capacity improved for both the whole group of patients with HF (P < .01) and HF patients with SDB (P < .05). No improvements regarding cardiac function, objective sleep, subjective sleep, or SDB were seen, except for a decrease of > or = 4% desaturations (P < .05). HRQOL did not differ significantly between HF patients with and without SDB before or after intervention with nocturnal oxygen. Long-term nocturnal oxygen treatment improved functional capacity in patients with severe HF, with or without SDB. No improvements were seen regarding sleep, daytime sleepiness, SDB, cardiac function, or HRQOL.     

Sex differences in the effect of HbA1c-defined diabetes on a wide range of cardiovascular disease risk factors

Objective Sex differences in the association of HbA1c and cardiovascular disease (CVD) risk remain controversial. We examined CVD risk profile in both HbA1c-defined diabetic and nondiabetic men and women.

Methods We conducted a cross-sectional analysis of 7139 Chinese adults using data from the China Health and Nutrition Survey 2009.

Results HbA1c-defined nondiabetic men have a more favorable CVD risk profile than female counterparts. However, HbA1c-defined diabetic men have higher levels of triglyceride, low-density lipoprotein (LDL)-cholesterol, and triglyceride/high-density lipoprotein (HDL)-cholesterol and lower levels of HDL-cholesterol, be more visceral obese as indicated by visceral adiposity index (VAI) and lipid accumulation product (LAP), and more insulin resistant as assessed by the triglycerides and glucose index (TyG) than HbA1c-defined diabetic women. Furthermore, HbA1c-defined diabetic men showed greater relative differences in ferritin than diabetic women when compared with their nondiabetic counterparts. Statistically signi?cant sex by HbA1c-defined diabetes status interactions were observed for triglyceride, LDL-cholesterol, HDL-cholesterol, triglyceride/HDL cholesterol, VAI, LAP, TyG, and ferritin (all ps?Conclusions Men who progressed from HbA1c-defined nondiabetes to HbA1c-defined diabetes have greater metabolic deteriorations and put on more visceral adiposity than women.

• Key messages

• HbA1c-defined nondiabetic men have a more favorable CVD risk profile than female counterparts.

• Men have to undergo a greater metabolic deterioration to develop HbA1c-defined diabetes than do women.

• Men have to put on more visceral adiposity to develop HbA1c-defined diabetes than do women.

     

Dyslipidemia in patients with type 2 diabetes. relationships between lipids, kidney disease and cardiovascular disease.

Type 2 diabetes mellitus is a leading cause of morbidity and mortality. Cardiovascular disease (CVD) is the most prevalent complication and primarily accounts for the excess morbidity and mortality in diabetic patients, but microvascular complications, such as kidney disease and retinopathy, are frequent and contribute to the total disease burden. Lipid abnormalities in patients with type 2 diabetes are a major problem and associated with the increased risk of CVD. The most common pattern of dyslipidemia in these patients consists of elevated levels of triglycerides and low levels of high-density lipoprotein cholesterol. Low-density lipoprotein levels in these patients are often similar to that of the nondiabetic population, although there may be important qualitative differences in the pattern that contribute to the increased risk of CVD. Abnormal levels of urinary albumin occur in 30-40% of patients with type 2 diabetes and the presence of kidney disease enhances the mortality from CVD. Microalbuminuria, an early marker of diabetic nephropathy, is an independent risk factor for CVD. The increased levels of urinary albumin secretion may represent a more generalized vascular damage than renal microvascular injury alone. This Review focuses on the significance of diabetic dyslipidemia and microalbuminuria to CVD risk as well as to kidney complications. We also discuss the role of aggressive therapy to ameliorate vascular injury in the diabetic patient and reduce or prevent the cardiovascular and renal consequences of the disease.     

Sleep-disordered breathing in fatigued postpoliomyelitis clinic patients

OBJECTIVE: To determine the frequency, predictive factors, and symptoms predictive of sleep-disordered breathing (SDB) in fatigued postpoliomyelitis clinic patients. DESIGN: Cross-sectional, retrospective chart review. SETTING: University-affiliated hospital postpolio clinic. PARTICIPANTS: Postpolio clinic charts (N=590) were reviewed. Ninety-eight patients were included, and 492 patients were not included, primarily because of the lack of a polysomnogram. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: The Apnea-Hypopnea Index (AHI) calculated as the total number of sleep-related breathing events/total sleep time. RESULTS: The frequency of SDB defined by an AHI score of 5 or more was 65% and by an AHI score of 10 or more was 50%. Obstructive hypopnea was the predominant form, occurring in 86%. Age, sex, age at acute polio, time since polio, weakness and respiratory difficulties at acute polio, bulbar involvement at acute polio and at evaluation, body mass index, pulmonary function measures, alcohol use, sedative drug use, smoking, fibromyalgia, kyphoscoliosis, and scoliosis and ear-nose-throat surgery were not predictive of SDB (AHI scores > or =5 and > or =10). Snoring was more common in subjects with SDB (AHI score > or =5 and > or =10). Some pulmonary function measures correlated with oxygen saturation during sleep in SDB (AHI scores > or =5). CONCLUSIONS: SDB was very common in fatigued postpoliomyelitis clinic patients referred for sleep evaluation. Obstructive hypopnea was the most frequent type. In this preliminary study, snoring tended to predict SDB.     

Common sleep problems in ICU: heart failure and sleep-disordered breathing syndromes

Ventilation during sleep is under tight metabolic control, and can be destabilized by upper airway obstruction leading to snoring or obstructive apneas, inadequate respiratory pump muscle activity leading to hypoventilation, and central control instability leading to changes in metabolic feedback and loop gain. These three physiologic disturbances can lead to obstructive sleep apnea hypopnea syndrome (OSAHS), hypoventilation syndromes, and periodic breathing. OSAHS places a strain on the cardiac output by virtue of hypoxemia, large negative intrathoracic pressures, and high swings in systemic blood pressure. Periodic breathing, also known as central sleep apnea with Cheyne-Stokes pattern of respiration, is likely to be a product of advanced heart failure.     

Central sleep apnea

Central sleep apnea is a disorder characterized by apneic episodes during sleep with no associated ventilatory effort. More commonly than not these apneas are seen in patients who also have obstructive and mixed events. Although patients with this disorder frequently complain of insomnia and depression, frank hypersomnolence is rarely encountered. As these complaints are common ones seen in numerous clinical situations, and since sleep studies are rarely conducted to investigate their etiology, the true incidence of central sleep apnea has not been determined. The etiology of central apnea remains unknown, although the association between these breathing events and a number of other disease processes has increased our understanding of the disorder. Central apneas during sleep commonly occur after hyperventilation with the associated hypocapnic alkalosis. This occurs at high altitude when hyperventilation is induced by hypoxia and at sea level when spontaneous nocturnal hyperventilation occurs. This suggests that PCO2 is the primary stimulus to ventilation during sleep and that loss of this drive, as occurs with hypocapnia, may produce dysrhythmic breathing. Patients with complete absence of ventilatory chemosensitivity such as occurs with Ondine's curse (central alveolar hypoventilation) or the obesity-hypoventilation syndrome may also have central apneas. For reasons that remain unexplained, central sleep apnea is commonly seen in patients with congestive heart failure, nasal obstruction, and certain neurologic disorders. However, in most patients with central sleep apnea no obvious cause or association can be found. The treatment of this disorder is not entirely satisfactory. If it is severe, mechanical ventilation during sleep can be provided by any one of a number of techniques. However, for the patient who simply complains of insomnia and is found to have a moderate number of central apneas, the treatment choices are limited. Acetazolamide has been shown to decrease central apneas during short-term use, but results have been variable with prolonged administration. Other ventilatory stimulants seem to have little efficacy. Interestingly, oxygen administration has been shown to reduce central apneas considerably in a number of studies, although the explanation for its success is unknown. Central sleep apnea therefore remains a relatively rare disorder whose etiology is not fully understood and whose treatment is not completely satisfactory.     

Cheyne-Stokes breathing during sleep in patients with left ventricular heart failure

Fifteen patients with left ventricular heart failure (LVF) without known breathing disorders during sleep had full-night recordings of sleep and breathing to study the incidence and impact of the apnea of Cheyne-Stokes breathing. This group showed a marked degree of sleep-related breathing abnormalities, 40% demonstrating Cheyne-Stokes breathing with five or more central apneas per hour of sleep. Cheyne-Stokes breathing during sleep in patients with LVF predicted an increased short-term mortality rate. All six patients with LVF and Cheyne-Stokes breathing with more than five apneas per hour of sleep were dead within six months, while only three of nine patients without recurrent apnea died within six months, a significant difference (P less than .05) even in this small group. Among seven patients with LVF studied with the polysomnogram, there were statistically significant differences between the Cheyne-Stokes and non-apnea groups in total sleep time, awakening per hour, and the number of arterial desaturations. Although sleep disturbances have been anecdotally described in patients with LVF, no previous investigation has determined the incidence and impact of Cheyne-Stokes breathing during sleep in LVF. Our findings that Cheyne-Stokes breathing predicts an adverse short-term mortality rate confirm the clinical impression that Cheyne-Stokes breathing is a poor prognostic sign in LVF.