Respiratory sleep disorders in patients with congestive heart failure

Respiratory sleep disorders (RSD) occur in about 40-50% of patients with symptomatic congestive heart failure (CHF). Obstructive sleep apnea (OSA) is considered a cause of CHF, whereas central sleep apnea (CSA) is considered a response to heart failure, perhaps even compensatory. In the setting of heart failure, continuous positive airway pressure (CPAP) has a definite role in treating OSA with improvements in cardiac parameters expected. However in CSA, CPAP is an adjunctive therapy to other standard therapies directed towards the heart failure (pharmacological, device and surgical options). Whether adaptive servo controlled ventilatory support, a variant of CPAP, is beneficial is yet to be proven. Supplemental oxygen therapy should be used with caution in heart failure, in particular, by avoiding hyperoxia as indicated by SpO₂ values >95%.     

Cycle length identifies obstructive sleep apnea and central sleep apnea in heart failure with reduced ejection fraction

Aim

To clarify whether unmasking of central sleep apnea during continuous positive airway pressure (CPAP) initiation can be identified from initial diagnostic polysomnography (PSG) in patients with heart failure with reduced ejection fraction (HFREF) and obstructive sleep apnea (OSA)

Materials and methods

Forty-three consecutive patients with obstructive sleep apnea and central sleep apnea (OSA/CSA) in HFREF were matched with 43 HFREF patients with OSA and successful CPAP initiation. Obstructive apneas during diagnostic PSG were then analyzed for cycle length (CL), ventilation length (VL), apnea length (AL), time to peak ventilation (TTPV), and circulatory delay (CD). We calculated duty ratio (DR) as the ratio of VL/CL and mathematic loop gain (LG).

Results

While AL was similar, CL, VL, TTPV, CD, and DR was significantly longer in patients with OSA/CSA compared to those with OSA, and LG was significantly higher. Receiver operator curves identified optimal cutoff values of 50.2 s for CL (area under the curve (AUC) 0.85, 29.2 s for VL (AUC 0.92), 11.5 s for TTPV (AUC 0.82), 26.4 s for CD (AUC 0.79), and 3.96 (AUC 0.78)) respectively for LG to identify OSA/CSA.

Conclusion

OSA/CSA in HFREF can be identified by longer CL, VL, TTPV, and CD from obstructive events in initial diagnostic PSG. The underlying mechanisms seem to be the presence of an increased LG.

     

Effects of dynamic bilevel positive airway pressure support on central sleep apnea in men with heart failure

BACKGROUND: Treatment with continuous positive airway pressure (CPAP) improves cardiac function in chronic heart failure (CHF) patients with central sleep apnea (CSA)-Cheyne-Stokes respiration (CSR) by stabilizing ventilation, but frequently central apneas and hypopneas persist. Our objective was to test the hypothesis that flow-targeted dynamic bilevel positive airway pressure (BPAP) support (BiPAP autoSV; Respironics; Murrysville, PA) effectively suppresses CSR-CSA in CHF patients. METHODS: We studied 14 CHF patients with CSR-CSA (and residual CSA on positive airway pressure therapy) during 3 consecutive nights: (1) diagnostic polysomnography, (2) CPAP (n=10) or BPAP (n=4) titration, and (3) dynamic flow-targeted dynamic BPAP support with an expiratory positive airway pressure (EPAP) set to suppress obstructive respiratory events, and an inspiratory positive airway pressure (IPAP) dynamically ranging between 0 and 15 cm H2O above the EPAP. RESULTS: CPAP or BPAP significantly reduced the apnea-hypopnea index (AHI) [mean+/-SD, 46+/-4 events/h to 22+/-4 events/h; p=0.001] compared to the first night without treatment. Flow-targeted dynamic BPAP support (mean EPAP, 6.5+/-1.7 cm H2O; maximal IPAP, 21.9+/-2.1 cm H2O) further reduced the AHI to 4+/-1/h of sleep compared to the untreated (p<0.001) and CPAP or BPAP night (p=0.002). After the first night of flow-targeted dynamic BPAP support, patients rated on an analog scale (range, 0 to 10) the treatment as comfortable (6.9+/-0.6), and the sleep quality as improved compared to previous nights (7.4+/-0.6). CONCLUSION: Flow-targeted dynamic BPAP support effectively suppresses CSR-CSA in patients with CHF and is well tolerated.     

Efficacy of adaptive servoventilation in treatment of complex and central sleep apnea syndromes

BACKGROUND: Complex sleep apnea syndrome (CompSAS) is recognized by the concurrence of mixed or obstructive events with central apneas, the latter predominating on exposure to continuous positive airway pressure (CPAP). Treatment of CompSAS or central sleep apnea (CSA) syndrome with adaptive servoventilation (ASV) is now an option, but no large series exist describing the application and effectiveness of ASV. METHODS: Retrospective chart review of the first 100 patients who underwent polysomnography using ASV at Mayo Clinic Sleep Center. RESULTS: ASV titration was performed for CompSAS (63%), CSA (22%), or CSA/Cheyne Stokes breathing patterns (15%). The median diagnostic sleep apnea hypopnea index (AHI) was 48 events per hour (range, 24 to 62). With CPAP, obstructive apneas decreased, but the appearance of central apneas maintained the AHI at 31 events per hour (range, 17 to 47) [p = 0.02]. With bilevel positive airway pressure (BPAP) in spontaneous mode, AHI trended toward worsening vs baseline, with a median of 75 events per hour (range, 46 to 111) [p = 0.055]. BPAP with a backup rate improved the AHI to 15 events per hour (range, 11 to 31) [p = 0.002]. Use of ASV dramatically improved the AHI to a mean of 5 events per hour (range, 1 to 11) vs baseline and vs CPAP (p < 0.0001). ASV also resulted in an increase in rapid eye movement sleep vs baseline and CPAP (18% vs 12% and 10%, respectively; p < 0.0001). Overall, 64 patients responded to the ASV treatment with a mean AHI < 10 events per hour. Of the 44 successful survey follow-up patients contacted, 32 patients reported some improvement in sleep quality. CONCLUSION: The ASV device appears to be an effective treatment of both CompSAS and CSA syndromes that are resistant to CPAP.     

A continuous positive airway pressure trial as a novel approach to the diagnosis of the obstructive sleep apnea syndrome

OBJECTIVES: Treatment of obstructive sleep apnea syndrome (OSA) is often delayed because polysomnography, the recommended standard diagnostic test, is not readily available. We evaluated whether the diagnosis of sleep apnea could be inferred from the response to a treatment trial with nasal continuous positive airway pressure (CPAP). DESIGN: Study on diagnostic accuracy. SETTING: Sleep-disorders clinic of a university hospital. PATIENTS: Seventy-six sleepy snorers consecutively referred for sleep apnea evaluation. INTERVENTIONS: CPAP treatment trial over 2 weeks as an initial diagnostic test in comparison with polysomnography, and treatment success over > or = 4 months. MEASUREMENTS AND RESULTS: The main outcome was diagnostic accuracy of the CPAP trial. The trial result was positive if the patient had used CPAP for > 2 h per night and wished to continue therapy. This suggested sleep apnea. The trial was evaluated in terms of predicting an obstructive apnea/hypopnea index (AHI) > 10/h during polysomnography performed for validation, and in terms of identifying sleep apnea patients treated successfully over > or = 4 months. Forty-four of 76 patients (58%) had sleep apnea as confirmed by an AHI > 10/h. The CPAP trial predicted sleep apnea with a sensitivity of 80%, a specificity of 97%, and positive and negative predictive values of 97% and 78%, respectively. In 35 of 76 sleep apnea patients (46%) with positive CPAP trial results, polysomnography could have been avoided. These patients were prescribed long-term CPAP therapy. After 4 months, 33 of 35 patients (94%) still used CPAP, and their symptoms remained improved. These patients were identified by the CPAP trial with positive and negative predictive values of 92% and 100%, respectively. CONCLUSIONS: In a selected population, a CPAP trial may help to diagnose OSA, to identify patients who benefit from CPAP, and to reduce the need for polysomnography.     

Effect of continuous positive airway pressure vs placebo continuous positive airway pressure on sleep quality in obstructive sleep apnea

STUDY OBJECTIVES: Continuous positive airway pressure (CPAP) therapy has become the treatment of choice for obstructive sleep apnea (OSA). However, the efficacy of CPAP therapy has not been evaluated against a suitable control. We investigated the effectiveness of CPAP therapy in improving sleep quality in patients with OSA. We hypothesized that CPAP improves sleep quality. PATIENTS: Forty-eight CPAP-naive OSA patients were evaluated. None were receiving antihypertensive medications, and none had major medical illnesses. DESIGN: Patients were randomized to receive either CPAP or placebo CPAP (CPAP at an ineffective pressure) for 7 days in a double-blind fashion. Forty-one patients completed the protocol. Sleep quality variables, arousals, sleep arterial oxygen saturation (SaO(2)), and respiratory disturbance index (RDI) were assessed at baseline, after 1 day of treatment, and after 7 days of treatment. Repeated measures analysis of variance was used to evaluate the effects of treatment, time, and the interaction of the two. RESULTS: As expected, CPAP lowered RDI and number of arousals, and increased SaO(2) over time (p = 0.001). Contrary to expectations, both CPAP and placebo CPAP had comparable effects on sleep quality as assessed by sleep architecture, sleep efficiency, total sleep time, and wake after sleep onset time. CONCLUSIONS: This study confirms the effectiveness of CPAP in lowering the number of arousals and the RDI, and in raising SaO(2). However, our data suggest that short-term CPAP is no different than placebo in improving sleep architecture. Further evaluation of the effectiveness of CPAP using a suitable placebo CPAP in prospective randomized studies is needed     

Impact of sleep apnea on sympathetic nervous system activity in heart failure

OBJECTIVES: To compare and establish the relevance of the relative degree of sympathetic nervous system activity (SNSA) in groups of patients with congestive heart failure (CHF) and obstructive sleep apnea (OSA), and in a control group. BACKGROUND: Elevated SNSA is a characteristic feature of CHF, as well as of OSA and nonhypercapnic central sleep apnea (CSA). OSA and CSA commonly occur with CHF; however, the relative contribution of apnea-related hypoxemia and sleep fragmentation to the SNSA of patients with CHF is not known. METHODS: This was a prospective, controlled, observational trial in which the overnight urinary norepinephrine (UNE) level, which is a measure of integrated overnight SNSA while asleep, was measured in 15 healthy male volunteers, 15 male OSA patients who did not have CHF, and 90 CHF patients (77 men). CHF patients also had right heart pressure measurements and then were grouped by the presence of sleep apnea. RESULTS: Compared with healthy individuals, the mean (+/- SD) UNE level was significantly elevated in the OSA group and was even further elevated in the CHF group (13.4 +/- 5.6 vs 19.7 +/- 12.3 vs 32.2 +/- 20.2 nmol/mmol creatinine, respectively; p < 0.001 [by analysis of variance]). Within the CHF group, the mean UNE levels were greatest in the CHF-CSA group compared with the CHF-OSA group and the CHF nonapnea group (43.9 +/- 24.1 vs 24.0 +/- 10.8 vs 22.4 +/- 8.9 nmol/mmol creatinine, respectively; p < 0.001). Using a multivariate regression model, the variance of the UNE level in the CHF group was predicted, in descending order, by pulmonary capillary wedge pressure (14% variance), rapid eye movement sleep (8%), and the mean sleep pulse oximetry level (7%). CONCLUSIONS: Overnight SNSA is significantly greater in CHF patients than in OSA patients. Moreover, the hemodynamic severity of CHF contributes to the elevation of SNSA in CHF patients to a greater degree than apnea-related hypoxemia.     

Effect of CO2 inhalation on central sleep apnea and arousals from sleep

BACKGROUND: CO(2) inhalation reduces central sleep apnea (CSA) in patients with congestive heart failure (CHF) and idiopathic CSA. CO(2) is also a stimulus for cortical arousal, which has been linked to increased sympathetic nerve activity (SNA) and increased mortality in CHF patients with CSA. OBJECTIVE: We have tested the hypothesis that during sleep, inhalation of CO(2) sufficient to reduce the apnea-hypopnea index (AHI) would not reduce the arousal index (AroI). METHODS: In 10 male patients with CSA (7 with CHF and 3 with idiopathic CSA), the inspired CO(2) concentration was increased to raise the sleeping end-tidal CO(2) by 2-4 mm Hg during established stage 2 sleep. Each intervention was maintained for a 10-min period. Sleep stage was monitored with electroencephalograms, electrooculograms, submental electromyogram, airflow with pneumotachometer and respiratory effort and blood gases with oxygen saturation and end-tidal CO(2). During periods of air and CO(2) breathing, AHI and AroI were compared with paired t tests; patients acted as their own controls. RESULTS: Inhalation of CO(2) produced a significant reduction in AHI (mean +/- SEM) from 74.4 +/- 12.4 events/h during air breathing to 25.8 +/- 7.8 events/h with CO(2) inhalation (p = 0.002). However, the AroI was not significantly different between the two conditions, air 67.8 +/- 12.3 events/h and CO(2) inhalation 52.8 +/- 12.4 events/h (p = 0.264). CONCLUSION: CO(2) inhalation reverses CSA but not arousals from sleep. Our findings highlight the need for treatment options that reduce both respiratory events and decrease arousals from sleep, with their associated SNA sequelae.     

Continuous positive airway pressure improves nocturnal baroreflex sensitivity of patients with heart failure and obstructive sleep apnea

OBJECTIVES: To determine the acute effects of continuous positive airway pressure (CPAP) on baroreceptor reflex sensitivity (BRS) for heart rate during sleep in congestive heart failure (CHF) patients with obstructive sleep apnea (OSA). DESIGN AND METHODS: In eight CHF patients with OSA not previously treated with CPAP, spontaneous BRS was assessed during overnight polysomnography prior to the onset of sleep, and during stage 2 non-rapid eye movement sleep (NREM) before, during and after application of CPAP. RESULTS: CPAP alleviated OSA and acutely increased the slope of BRS (median, 25%,75%) [from 3.9 (3.5, 4.8) to 6.2 (4.6, 26.2) ms/mmHg, P<0.05]. Increases in the slope of BRS persisted following withdrawal of CPAP [4.9 (4.3, 6.9) ms/mmHg, P<0.05]. CPAP also lowered heart rate (from 81.3 +/- 4.9 to 76.0 +/- 5.7 bpm, P< 0.05), an effect which persisted after its withdrawal (76.7 +/- 5.7 bpm, P < 0.05). Systolic blood pressure at the midpoint of the pressure range of BRS sequences fell while on CPAP (from 139 +/- 8 to 120 +/- 7 mmHg, P < 0.05), and remained lower following CPAP withdrawal (124 +/- 9 mmHg, P < 0.05). CONCLUSIONS: In CHF patients with OSA, CPAP increases acutely BRS during sleep, lowers heart rate and resets the operating point for BRS to a lower blood pressure. These effects of CPAP persist after its withdrawal, suggesting that nocturnal CPAP therapy may cause sustained improvement in the neural control of heart rate.     

复杂型睡眠呼吸暂停综合征12例分析

目的 分析复杂型睡眠呼吸暂停综合征(complex sleep apnea syndrome,CompSAS)患者临床特点.方法 收集我院12例CompSAS患者作回顾性分析,比较经鼻持续气道正压通气(continuous positive airway pressure,CPAP)治疗前后睡眠质量、呼吸紊乱、压力变化...     

Diagnosis and treatment of sleep apnea in heart disease

Opinion statement One of the most common yet unidentified conditions in heart disease is sleep-disordered breathing (SDB). Although it is most prevalent in patients with heart failure, it has been epidemiologically and pathophysiologically linked to ischemic heart disease, hypertension, sudden cardiac death, atrial fibrillation, and stroke. There are two primary SDB syndromes: obstructive sleep apnea (OSA) and central sleep apnea (CSA; also known as Cheyne-Stokes respiration). The pathophysiologic mechanisms that underlie these disorders appear to be distinct but both involve recurrent cycles of excessive sympathetic activation, hypoxemias and hypercapnias, and increases in ventricular wall stress. Signs and symptoms may include daytime somnolence, snoring, difficult-to-control hypertension, and refractory arrhythmias or angina. In heart failure, half of patients will have SDB and most patients will exhibit evidence of both OSA and CSA, although one or the other may predominate. The current standard diagnostic method is overnight laboratory polysomnography. Primary therapies for OSA include lifestyle changes, various facial and oral appliances, head and neck surgery, and continuous positive airway pressure (CPAP). CPAP is the most effective form of therapy for OSA, with few side effects, but is limited by compliance because of comfort-related issues. In patients with cardiovascular disease who predominantly suffer from OSA, treatment recommendations should be based on current guidelines for OSA. For patients with heart failure with predominant CSA, the current cornerstone of therapy is the optimization of medical therapy and resynchronization therapy when indicated. When SDB persists despite optimal medical management, referral to a sleep medicine consultant should be considered.     

Risk factors for central and obstructive sleep apnea in 450 men and women with congestive heart failure.

In previous analyses of the occurrence of central (CSA) and obstructive sleep apnea (OSA) in patients with congestive heart failure (CHF), only men were studied and risk factors for these disorders were not well characterized. We therefore analyzed risk factors for CSA and OSA in 450 consecutive patients with CHF (382 male, 68 female) referred to our sleep laboratory. Risk factors for CSA were male gender (odds ratio [OR] 3.50; 95% confidence interval [CI], 1.39 to 8.84), atrial fibrillation (OR 4.13; 95% CI 1.53 to 11. 14), age > 60 yr (OR 2.37; 95% CI 1.35 to 4.15), and hypocapnia (PCO(2 )< 38 mm Hg during wakefulness) (OR 4.33; 95% CI 2.50 to 7. 52). Risk factors for OSA differed by gender: in men, only body mass index (BMI) was significantly associated with OSA (OR for a BMI > 35 kg/m(2), 6.10; 95% CI 2.86 to 13.00); whereas, in women, age was the only important risk factor (OR for age > 60 yr, 6.04; 95% CI 1.75 to 20.0). We conclude that historical information, supplemented by a few simple laboratory tests may enable physicians to risk stratify CHF patients for the presence of CSA or OSA, and the need for diagnostic polysomnography for such patients. Sin DD, Fitzgerald F, Parker JD, Newton G, Floras JS, Bradley TD. Risk factors for central and obstructive sleep apnea in 450 men and women with congestive heart failure.     

Washout Rate of Cardiac Iodine-123 Metaiodobenzylguanidine is High in Chronic Heart Failure Patients With Central Sleep Apnea

BackgroundThe association between sleep-disordered breathing (SDB) assessed by polysomnography and cardiac sympathetic nerve activity (SNA) assessed by cardiac iodine-123 metaiodobenzylguanidine (123I-MIBG) imaging has not been investigated in patients with chronic heart failure (CHF).Methods and ResultsWe performed cardiac 123I-MIBG scintigraphy and overnight polysomnography in 59 patients with stable CHF. The patients were classified into the 3 groups: 19 with no or mild SDB (NM-SDB, apnea-hypopnea index <15); 21 with central sleep apnea (CSA), and 19 with obstructive sleep apnea (OSA). The cardiac washout rate (WR) of 123I-MIBG was obtained from initial and delayed planar 123I-MIBG images. The WR was higher in patients with CSA (54.2 ± 11.6%) than in those with OSA (37.9 ± 8.6%, P < .05) or NM-SDB (40.8 ± 8.8%, P < .05). The WR correlated positively with central apnea index (ρ = 0.40, P = .002). A stepwise multiple regression analysis selected CSA and plasma brain natriuretic peptide levels as independent variables associated with the WR.ConclusionsThe WR was higher in CHF patients with CSA than in those with OSA or NM-SDB, and CSA was independently associated with the WR, suggesting a link of CSA to increased cardiac SNA in CHF.     

Effect of a 2 week CPAP treatment on mood states in patients with obstructive sleep apnea: a double-blind trial

Obstructive sleep apnea (OSA) is a common disease with significant medical and psychiatric comorbidities. The literature documenting the effects of continuous positive airway pressure (CPAP) treatment on mood in OSA patients is mixed. We previously observed that 1 week of CPAP treatment did not result in improvements in mood beyond those observed in a group treated with placebo–CPAP. This study examined the effect of a 2 week CPAP treatment on mood in a placebo-controlled design in OSA patients. Fifty patients with untreated sleep apnea were evaluated by polysomnography and completed the Profile of Mood States (POMS) pre-/post-treatment. The patients were randomized for 2 weeks to either therapeutic CPAP or placebo–CPAP (at insufficient pressure). Both the therapeutic CPAP and the placebo–CPAP groups showed significant improvements in POMS total score, tension, fatigue, and confusion. No significant time × treatment effect was observed for either group. We could not show a specific beneficial impact of CPAP treatment on mood in OSA patients.     

Acute effect of nasal continuous positive air pressure on the ventilatory control of patients with obstructive sleep apnea.

BACKGROUND: Sleep fragmentation can decrease the awake ventilatory control. Since patients with obstructive sleep apnea (OSA) patients exhibit sleep fragmentation linked to respiratory events, their ventilatory control could be impaired. However, most of these patients are also obese, which could conversely increase the ventilatory control. The effect of nasal continuous positive airway pressure (CPAP) on the awake ventilatory control in normocapnic OSA patients is unclear. Objectives: To study the acute effect of nasal CPAP on the awake ventilatory control in normocapnic OSA patients. METHODS: 12 normocapnic OSA patients, with an apnea/hypopnea index (AHI) >15 with moderate obesity (body mass index: 33.5 kg/m2) and normal pulmonary function tests were submitted to two polysomnography studies (diagnostic and for CPAP titration). Before and after 3 consecutive nights of nasal CPAP we analyzed the hypersomnia score and the ventilatory and the mouth occlusion pressure (P.1) responses at rest (breathing room air and a mixture of 8% CO2 + 40% O2). RESULTS: The respiratory drive of OSA patients as evaluated by P.1 was in the range of the controls of our laboratory. After nasal CPAP, a significant decrease in AHI (mean: 51.9-9.4/h) and arousal (mean: 88.7-43/h) occurred, as well as improvement in nocturnal oxyhemoglobin. There was a marginal increase in DeltaV(E)/DeltaP(ET)CO2 (mean: 1.41-1.87 liters/min/ mm Hg, p = 0.09) and a significant rise in P.1/DeltaP(ET)CO2 (mean: 0.29-0.43 cm H2O/mm Hg), a better indicator of ventilatory drive. CONCLUSIONS: Normocapnic OSA patients increased their awake ventilatory drive response to a hypercapnic and hyperoxic mixture with the use of 3 consecutive nights of nasal CPAP.     

Nasal continuous positive airway pressure use in children with obstructive sleep apnea younger than 2 years of age

STUDY OBJECTIVES: To assess the efficacy of continuous positive airway pressure (CPAP) in obstructive sleep apnea (OSA) patients who are < 2 years of age. DESIGN: A retrospective chart review of 18 patients from 1992 to 1999 who had OSA confirmed by polysomnography. All patients in this study also completed a separate night of CPAP polysomnography to determine the effectiveness of CPAP in the correction of OSA. Nasal CPAP compliance data were gathered via clinical follow-up examination, telephone interview, or mailed questionnaire. SETTING: All patients were studied in the Sleep Disorders Center at Loma Linda University Children's Hospital in Loma Linda, CA. PATIENTS: All patients were < 2 years old. INTERVENTION: After OSA was confirmed by the results of technician-attended nocturnal polysomnography, separate technician-attended nocturnal CPAP polysomnography was completed. On CPAP nights, CPAP pressure was titrated to ameliorate OSA and snoring. CPAP pressure was increased by 2-cm H(2)O or 1-cm H(2)O increments. RESULTS: Data were analyzed by dependent groups t test at p < 0.05 level of significance. CPAP statistically improved respiratory parameters significantly when compared to baseline polysomnography. The following four patient subgroups emerged from the analysis: group 1 consisted of six patients who had tracheostomies prior to the CPAP trial, with two patients using CPAP as an alternative to tracheostomy; group 2 consisted of two patients who had previous unsuccessful adenostonsillectomies and who used CPAP successfully, with both having OSA resolution over time; group 3 consisted of four patients who did not tolerate CPAP on the study night; and group 4 consisted of six patients who used CPAP nightly, had OSA resolution over time, and therefore, no longer needed CPAP therapy. Thus, 10 of 18 patients used CPAP either on an interim basis for corrective therapy or as a primary treatment modality for OSA. CONCLUSIONS: These data show that children < 2 years of age can tolerate and use CPAP effectively. In several cases, CPAP treatment could be discontinued as OSA resolved over time. The reasons for this are discussed in the text.     

Overnight shift from obstructive to central apneas in patients with heart failure: role of PCO2 and circulatory delay

BACKGROUND: Obstructive (OSA) and central sleep apnea (CSA) can coexist in patients with congestive heart failure (CHF). However, the reason why OSA events occur at one time and CSA events at another has not been determined. We hypothesized that a change in PCO(2) would be associated with an alteration in apnea type: a decrease in PCO(2) should lead to CSA. METHODS AND RESULTS: To test this hypothesis, we evaluated minute ventilation (V(I)), transcutaneous PCO(2) (PtcCO(2)), circulation time, and periodic breathing cycle length during overnight polysomnography in 12 patients with CHF and coexisting OSA and CSA. V(I) was significantly greater (mean+/-SEM, 9.4+/-1.3 versus 8.0+/-0.9 L/min; P:<0.05) and PtcCO(2) was lower (39.4+/-1.0 versus 41.9+/-1.1 mm Hg, P:<0.01) during episodes of CSA than of OSA. These changes were associated with significant lengthening of circulation time (23.6+/-3.7 versus 21.1+/-3.6 seconds, P:<0.01) and periodic breathing cycle length (53.7+/-3.5 versus 49.6+/-2.9 seconds, P:<0.01). In addition, the proportion of obstructive events decreased (from 68.5+/-11.4% to 22.5+/-7.2%, P:<0.001) and of CSA events increased (from 31.5+/-11.4% to 77.5+/-7.2%, P:<0.001) from the first to the last quarter of the night in association with a significant decrease in PtcCO(2) (from 42.6+/-0.9 to 40.8+/-0.9 mm Hg, P:<0.01). CONCLUSIONS: In patients with CHF, the shift from OSA to CSA is associated with a reduction in PCO(2). This appears to be related to an overnight deterioration in cardiac function as suggested by the concurrent lengthening of circulation time. Therefore, in CHF patients, alterations in cardiac function may influence apnea type.     

Fixed and autoadjusting continuous positive airway pressure treatments are not similar in reducing cardiovascular risk factors in patients with obstructive sleep apnea

BACKGROUND: A strong association between obstructive sleep apnea (OSA) and the risk for cardiovascular and cerebrovascular diseases has been reported. Continuous positive airway pressure (CPAP) is the first-line therapy for OSA, able not only to reduce daytime sleepiness but also to improve cardiovascular and metabolic outcomes. Autoadjusting CPAP (APAP), an alternative treatment to CPAP, can reduce OSA symptoms while increasing long-term CPAP compliance without the high costs of CPAP titration. However, no data are available on the effects of APAP on cardiovascular risk factors METHODS: We performed standard full polysomnography; obtained plasma levels of glucose, insulin, and C-reactive protein (CRP); and measured systolic BP (SBP) and diastolic BP (DBP) in 31 patients with newly diagnosed, severe OSA. After standard CPAP titration, all subjects were randomized to CPAP or APAP treatment. Measurements were obtained at baseline and after 3 months of treatment. RESULTS: The two groups were similar in terms of age, sex, body mass index (BMI), and severity of OSA. SBP, DBP, heart rate (HR), homeostasis model assessment index (HOMA-IR), and CRP were similar in the two groups. After 3 months of treatment, BMI, HR, and compliance to therapy were also comparable. OSA indexes were significantly reduced in both groups. Significant reductions in SBP, DBP, and HOMA-IR were observed in the CPAP group but not in the APAP group, while CRP plasma levels were similarly reduced. CONCLUSIONS: Our results suggest that CPAP and APAP, despite significant effects on OSA indexes and symptoms, do not improve cardiovascular risk factors in the same fashion.     

阻塞性睡眠呼吸暂停心血管相关血清学标志物研究进展

阻塞性睡眠呼吸暂停（OSA）最常见的临床症状是夜间睡眠打鼾伴呼吸暂停,以慢性间歇性缺氧、高碳酸血症、反复微觉醒和睡眠结构紊乱为病理生理基础,是心血管疾病的源头疾病和危险因素。在临床实践中,多导睡眠监测仍是确诊OSA的金标准,但是受多导睡眠监测局限性、需专业的睡眠医师阅读报告等诸多因素的影响,导致多数患者诊治延迟。因此,目前研究热点是探寻一种简易、便捷的血清学标志物,从OSA患者中筛选心血管疾病高危患者,实现早期防治、精准治疗。     

Clinical characteristics of Asian patients with sleep apnea with low arousal threshold and sleep structure change with continuous positive airway pressure

Purpose

Low respiratory arousal threshold (ArTH) has been observed to be prevalent in patients with obstructive sleep apnea (OSA), and is associated with poor adherence to continuous positive airway pressure (CPAP) treatment. This study aimed to examine the associations between low ArTH and clinical characteristics. The second aim was to examine sleep structure changes between diagnostic polysomnography (PSG) and CPAP titration studies.

Methods

PSG data for 3718 adults who had an apnea-hypopnea index (AHI) ≥?5 were reviewed retrospectively, as well as 206 CPAP titration studies among these participants. Participants were dichotomized into low- and high-ArTH groups according to their PSG parameters. The associations between low ArTH and clinical characteristics were examined by multivariate logistic regressions. The sleep structure changes between PSG and CPAP titration studies were examined by repeated measures ANOVA.

Results

Fifty percent of patients with OSA had low ArTH. Compared with high-ArTH patients, low-ArTH patients were less obese and composed of a higher percentage of women. In logistic regression models, low ArTH was associated with bruxism and nocturia, but not with illnesses after adjusting for AHI and body mass index. Compared with diagnostic PSG studies, low-ArTH patients had significantly decreased stage changes and increased percentage of rapid eye movement sleep during CPAP titration studies.

Conclusion

Low ArTH was prevalent in this large sample of patients with OSA. Arousal threshold was not associated with an increased risk of physical illnesses but was with certain clinical complaints. Low-ArTH patients benefited from CPAP titration study for improved sleep structure.