Work of Breathing in Fixed and Pressure Relief Continuous Positive Airway Pressure (C-Flex™): A post hoc Analysis.

BACKGROUND: Expiratory pressure relief continuous positive airway pressure (pressure relief CPAP; C-Flex™) causes increases in inspiratory duty cycle and shortening of expiratory time. It has been suggested that these changes are caused by an increase in work of breathing. OBJECTIVES: We studied the effects of C-Flex on work of breathing and intrinsic positive end-expiratory pressure as compared to fixed CPAP. METHODS: Work of breathing was analyzed in 24 patients with obstructive sleep apnea during treatment with fixed CPAP and C-Flex with 3 different pressure relief settings in a randomized order during rapid-eye-movement (REM) and non-REM sleep. Work of breathing was assessed on a breath-by-breath basis using a piezoelectric esophageal pressure catheter and a pneumotachograph for measuring airflow. RESULTS: We found there was no increase in inspiratory work of breathing observed using C-Flex compared to fixed CPAP. Instead, we found a linear decrease in inspiratory work of breathing with increasing pressure relief, with a mean difference of 1.22 J/min between CPAP and maximum pressure release (C-Flex 3; 90% of the value with nasal CPAP); however, the decrease was not statistically significant. The decrease in inspiratory work of breathing associated with C-Flex has a significant inverse correlation with BMI. CONCLUSIONS: The C-Flex technology does not change work of breathing but shows a tendency towards a reduction of inspiratory work of breathing in patients with a lower BMI using higher C-Flex. The effect is probably caused by diminishing airway resistance generated by the positive end-expiratory pressure. Our findings may lead to additional fields of application of the C-Flex technology, such as chronic obstructive pulmonary disease or muscular dystrophy.

Health-related quality of life in patients with narcolepsy.

BACKGROUND: To evaluate the health-related quality of life (HRQoL) in patients suffering from narcolepsy. METHODS: Subjects included 75 narcoleptic patients diagnosed at the Hephata Klinik, Germany, who met the International Classification of Sleep Disorders (ICSD) criteria for narcolepsy. A standardized telephone interview was used to inquire about the disease and its burdens to the patients. HRQoL was recorded using the 36-item short-form Medical Outcomes Study (SF-36) as well as the Euroqol (EQ-5D). Frequency and factors of influence on decreased HRQoL were evaluated by using bivariate and multivariate analyses. RESULTS: Patients with narcolepsy had considerably lower scores on all eight domains of the SF-36 compared to the general German population. In particular, scores were poor for the dimensions "physical role", "vitality", and "general health perception". Forty-eight percent of the patients reported problems in at least one of the EQ-5D items; most frequent were problems in the dimension "usual activity" (63.8%), "pain/discomfort" (61.7%) and "anxiety/depression" (41.1%). Difficulty maintaining "self-care" was documented only by 6.8%. The mean VAS score was 60.7%. Interestingly, signs and symptoms of narcolepsy, except for irresistible sleep episodes (p<0.03), had only a minor impact on HRQoL. Multivariate analyses confirmed a strong influence of employment status, living with a partner, excessive daytime sleepiness (EDS) and professional advancement. CONCLUSIONS: HRQoL is considerably reduced in patients, with narcolepsy affecting the different dimensions to various degrees. Factors other than clinical signs and symptoms are associated also with poor HRQoL. Measures should be taken to integrate those factors into healthcare guidelines in order to improve the quality of life in patients with narcolepsy.

Brain natriuretic peptide for prediction of Cheyne-Stokes respiration in heart failure patients.

Cheyne-Stokes respiration (CSR) is indicative of adverse outcome in patients with chronic heart failure (CHF). We evaluated the use of brain natriuretic peptide (BNP) plasma levels to predict CSR in CHF patients. In this cross-sectional study, overnight polygraphy and cardiac work-up were performed and neurohumoral activation was determined in 102 consecutive CHF patients (25-82 years). Demographic characteristics did not significantly differ among patients with (n=38) or without CSR (n=64); BNP (median: 377 vs. 142 pg/ml, p<0.001) and norepinephrine levels (459+/-283 vs. 346+/-204 pg/ml, p=0.02) were significantly increased in patients with CSR. BNP concentrations were significantly associated with the central apnoea/hypopnoea index (y=253+/-5.3x; r=0.26, p=0.01). The area under the ROC curve that used BNP to predict CSR was 0.780 (95% CI: 0.688 to 0.873). Using established cut-off limits of BNP plasma levels, heart failure patients with BNP levels >500 pg/ml displayed a 13 fold increased risk of CSR (95% CI: 2.34-73.50; p=0.03) compared to patients with BNP levels <100 pg/ml. In multiple logistic regression analysis p(a)CO2 (point estimate 0.84, 95% CI: 0.72 to 0.98; p=0.02) and higher BNP class (point estimate 3.14, 95% CI: 1.38-7.144; p=0.006) emerged as parameters independently predicting the presence of CSR in our cohort of CHF patients. In conclusion, CSR is associated with neurohumoral activation in CHF patients. Specifically, BNP levels are associated with the severity of cardiac and sleep-related disease, and may be helpful in the diagnosis of CSR and more appropriate use of polysomnography in CHF patients.

Obesity, sleep apnea syndrome, and rhythmogenic risk.

Obstructive sleep apnea is a common disorder and affects approximately 4% of middle-aged men and 2% of middle-aged women. Obstructive sleep apnea is clearly associated with obesity, with more than 50% of patients having a body mass index>30 kg/m2. Substantial evidence identified obstructive sleep apnea as risk factor not only for excessive daytime sleepiness and road traffic accidents, but also for increased cardiovascular morbidity and mortality. In addition, all kinds of arrhythmias have been observed in patients with sleep apnea ranging from asymptomatic sinus bradycardia to sudden cardiac death. Approximately 5-10% of patients with obstructive sleep apnea show marked apnea-related bradyarrhythmias due to enhanced vagal tone and pronounced hypoxia. Therapeutic options in obese patients with obstructive sleep apnea include consequent weight loss and nasal continuous positive airway pressure (CPAP) ventilation as the therapy of first choice. Weight reduction and effective nasal CPAP therapy significantly decrease cardiovascular morbidity and mortality and eliminate sleep-related bradyarrhythmias in 80-90% of patients obviating the need for pacemaker implantation in these patients.

[Intermediate care units and noninvasive ventilation]. / Intermediate-Care-Units und nichtinvasive Beatmung.

Intermediate care units (IMC) have been introduced to provide optimal patient management according to disease severity and to bridge the gap between intensive care (ICU) and general wards. Most patients that are referred to an IMC need monitoring and intensive analgetic treatment. Over the past years noninvasive ventilation (NIV) and weaning have emerged as important new forms of active treatment in the IMC. Most studies that have been published so far demonstrate that an IMC improves patient outcome and lowers costs, although randomized controlled trials are missing. NIV reduces mortality, the need for intubation as well as ICU and hospital length of stay in patients with chronic obstructive pulmonary disease (COPD) and other disorders that cause respiratory failure. In many cases NIV can be performed in the IMC, a fact that reduces the number of ICU admissions, lowers costs and improves patient care. The high prevalence of pulmonary diseases and NIV emphasizes the importance of pneumologists as directors of both ICU and IMC.

Central sleep related breathing disorders - diagnostic and therapeutic features.

THREE CLASSES OF CENTRAL SRBD ARE DISTINGUISHED: 1. Central sleep apnea (CSA), 2. Cheyne-Stokes Respiration as a subgroup of CSA and 3. central hypoventilation syndromes. Reduced or completely absent central respiratory drive without upper airway obstruction is the common feature of central SRBD. Hypoventilation syndromes most often occur secondary in patients with neuromuscular, pulmonary or sceletal diseases or in patients with massive obesity. In patients with hypoventilation during sleep nocturnal and exertional dyspnea and headaches are frequently reported symptoms. Excessive daytime sleepiness is the key symptom in patients with central sleep apnea syndrome. Cheyne-Stokes Respiration is frequent in heart failure patients but in many cases does not cause symptoms specific for the breathing disorder. If there are symptoms or if ambulatory recording of breathing during sleep suggests a sleep related breathing disorder, polysomnography is then performed to definitively rule out or confirm the diagnosis and to initiate treatment, if needed. The indication for treatment in asymptomatic patients with central sleep apnea and Cheyne-Stokes Respiration may be difficult, as there are very little data concerning the long-term benefit in these patients. Symptomatic patients and those with severe central sleep apnea should be treated. Oxygen and CPAP may be effective in 20-30% of patients each. If these treatment options are ineffective, non-invasive pressure support ventilaiton can be used. In patients suffering from hypoventilation syndromes the treatment of choice is non-invasive pressure support ventilaiton combined with supplemental oxygen, if required.

[Sleep apnea--treatment improves hypertension]. / Schlafapnoe--Behandlung verbessert Hypertonie.

Obstructive sleep apnea and arterial hypertension are frequent diseases, but they are also often overlooked. There is a causal relationship of sleep apnea and hypertension. Undiagnosed sleep apnea is probably the most important reason for "essential" hypertension. It is important to identify these patients. All hypertensive patients should be asked for snoring, breathing arrest and daytime sleepiness, neck circumference should be measured, and an ambulant sleep apnea monitoring should be performed, if necessary. Especially patients with refractory hypertension or non-dippers should be screened for sleep apnea and patients with sleep apnea should be examined for arterial hypertension. Continuous positive airway pressure (CPAP) can effectively lower blood pressure in the hypertensive sleep apnea patient. This is especially true for the obstructive sleep apnea patient with refractory hypertension. CPAP therapy is probably the best therapy for sleep apnea-induced nocturnal blood pressure rises.

The socioeconomic impact of narcolepsy.

STUDY OBJECTIVE: To evaluate the economic burden of patients suffering from narcolepsy. DESIGN: Cross-sectional study. PARTICIPANTS: 75 narcoleptic patients diagnosed at the Hephata Klinik, Germany, who met the International Classification of Sleep Disorders criteria for narcolepsy. MEASUREMENTS: A standardized telephone interview was used to inquire about the disease and its burden. In addition, health-related quality of life scales (SF-36 and EQ-5D) were mailed to the patients. Complete data were available for 75 patients. Direct and indirect costs were calculated from the societal perspective. All costs (mean +/- SD) were calculated in 2002 Euros (Euros). RESULTS: Total annual costs were Euros 14,790 +/- 16,180 (US-dollars 15,410) per patient. Direct costs were Euros 3,180 +/- 3,540 (US-dollars 3,310), which consisted of hospital costs (Euros 1,210 +/- 2,210; US-dollars 1,260), drug costs (narcolepsy medication: Euros 1,020 +/- 1,420; US-dollars 1,060), ambulatory care (Euros 90 +/- 90; US-dollars 40), and ambulatory diagnostics (Euros 20 +/- 30; US-dollars 20). More than 50% of the drug costs were due to the newer wake-promoting drugs. Total annual indirect costs amounted to Euros 11,390 +/- 15,740 (US-dollars 11,860) per patient and were mainly attributable to early retirement due to the disease. Narcolepsy was listed as being the cause of unemployment by 32 patients. In patients with sleep attacks, there was a significant correlation between early retirement and higher indirect costs compared to patients without these attacks. CONCLUSIONS: Narcolepsy causes a high socioeconomic burden, which is comparable to other chronic neurologic diseases, Indirect costs are considerably higher than direct costs. Measures should be taken to increase public awareness of this disease. Appropriate treatment must be provided in order to increase quality of life and to assist patients continuing in working life.

Peripheral arterial tonometry, oximetry and actigraphy for ambulatory recording of sleep apnea.

Autonomous nervous functions change with sleep stages and show characteristic changes associated with sleep disorders. Therefore, continuous monitoring of autonomous nervous functions during sleep can be used for diagnostic purposes. Recently, the peripheral arterial tonometry (PAT) has been introduced to determine peripheral arterial vascular tone on the finger being determined by sympathetic activity. We investigate a new ambulatory recording system which uses PAT, oximetry and actigraphy (Watch-PAT) in order to detect sleep apnea and arousal. The Watch-PAT is battery operated and attached to the wrist and has two finger sensors. Twenty-one patients with suspected sleep apnea were recorded with cardiorespiratory polysomnography and the new system in parallel. Seventeen recordings could be evaluated. The correlation for the apnea/hypopnea index derived from the sleep laboratory and the respiratory disturbance index derived from the Watch-PAT was r = 0.89 (p < 0.01) and between arousals and the respiratory disturbance index was r = 0.77 (p < 0.01). The correlation for the total sleep time compared between the two systems was r = 0.15 (n.s.). The Watch-PAT detects apneas and hypopneas with a reasonable reliability and it is very sensitive to arousals. The number of Watch-PAT events lies between the sum of apneas plus hypopneas and arousals. Arousals are not unique to apnea events and therefore the specifity of the Watch-PAT is limited. In conclusion, the Watch-PAT is well suited to perform therapy control studies in patients suffering from sleep apnea and being treated.

Association of right ventricular dysfunction and Cheyne-Stokes respiration in patients with chronic heart failure.

Cheyne-Stokes respiration (CSR) is present in up to 40% of patients with congestive heart failure (CHF) and is an independent risk factor for increased overall mortality. We examined whether CSR is associated with right ventricular (RV) dysfunction in CHF patients. Parameters of RV function were assessed by two-dimensional echocardiography and tissue velocity imaging in 42 patients (aged 23-75 years) with a left ventricular (LV) ejection fraction below 40%. Respiratory polygraphy revealed CSR with an central apnea-hypopnea index (CAHI) >10 h-1 in 13 of the 42 patients (31%). Demographic characteristics did not differ among the patient groups. The velocity of the tricuspid annular systolic motion (TASM), a parameter reflecting systolic RV function, was significantly reduced in CHF patients with CSR (10.5 +/- 2.3 cm s-1) compared with those without CSR (15.0 +/- 5.1 cm s-1, P = 0.004), and was inversely associated with the CAHI (y = 15.2-0.2x; r = 0.46, P = 0.003). The RV dimensions were significantly increased and the fractional RV area changes significantly reduced in CHF patients with CSR (33 +/- 17 versus 48 +/- 20%; P = 0.04). Doppler parameters of pulmonary artery flow indicate higher pulmonary artery pressures in CSR patients compared with patients without CSR, which is also reflected by an increased RV free-wall thickness in CSR patients (6.5 +/- 1.1 vs. 5.3 +/- 1.3 mm; P = 0.05). Parameters of systolic LV function, forced expiratory volume in 1 s (FEV1), and PaO2 and PaCO2 were not different among patients with or without CSR. In conclusion, CSR is associated with depressed systolic RV function and increased RV dimensions in CHF patients. Future studies will show whether optimized treatment of CSR will improve RV function.

Effect of nasal continuous positive airway pressure treatment on blood pressure in patients with obstructive sleep apnea.

BACKGROUND: There is increasing evidence that obstructive sleep apnea (OSA) is an independent risk factor for arterial hypertension. Because there are no controlled studies showing a substantial effect of nasal continuous positive airway pressure (nCPAP) therapy on hypertension in OSA, the impact of treatment on cardiovascular sequelae has been questioned altogether. Therefore, we studied the effect of nCPAP on arterial hypertension in patients with OSA. METHODS AND RESULTS: Sixty consecutive patients with moderate to severe OSA were randomly assigned to either effective or subtherapeutic nCPAP for 9 weeks on average. Nocturnal polysomnography and continuous noninvasive blood pressure recording for 19 hours was performed before and with treatment. Thirty two patients, 16 in each group, completed the study. Apneas and hypopneas were reduced by approximately 95% and 50% in the therapeutic and subtherapeutic groups, respectively. Mean arterial blood pressure decreased by 9.9+/-11.4 mm Hg with effective nCPAP treatment, whereas no relevant change occurred with subtherapeutic nCPAP (P=0.01). Mean, diastolic, and systolic blood pressures all decreased significantly by approximately 10 mm Hg, both at night and during the day. CONCLUSIONS: Effective nCPAP treatment in patients with moderate to severe OSA leads to a substantial reduction in both day and night arterial blood pressure. The fact that a 50% reduction in the apnea-hypopnea index did not result in a decrease in blood pressure emphasizes the importance of highly effective treatment. The drop in mean blood pressure by 10 mm Hg would be predicted to reduce coronary heart disease event risk by 37% and stroke risk by 56%.