Continuous positive airway pressure therapy in sleep apnoea

Sympathetic activity in obesity: a brief review of methods and supportive data

The increase in the prevalence of obesity and the concomitant rise in obesity-related illness have led to substantial pressure on health care systems throughout the world. While the combination of reduced exercise, increased sedentary time, poor diet, and genetic predisposition is undoubtedly pivotal in generating obesity and increasing disease risk, a large body of work indicates that the sympathetic nervous system (SNS) contributes to obesity-related disease development and progression. In obesity, sympathetic nervous activity is regionalized, with activity in some outflows being particularly sensitive to the obese state, whereas other outflows, or responses to stimuli, may be blunted, thereby making the assessment of sympathetic nervous activation in the clinical setting difficult. Isotope dilution methods and direct nerve recording techniques have been developed and utilized in clinical research, demonstrating that in obesity there is preferential activation of the muscle vasoconstrictor and renal sympathetic outflows. With weight loss, sympathetic activity is reduced. Importantly, sympathetic nervous activity is associated with end-organ dysfunction and changes in sympathetic activation that accompany weight loss are often reflected in an improvement of end-organ function. Whether targeting the SNS directly improves obesity-related illness remains unknown, but merits further attention.

Sympathetic neural activity to the cardiovascular system: integrator of systemic physiology and interindividual characteristics

The sympathetic nervous system is a ubiquitous, integrating controller of myriad physiological functions. In the present article, we review the physiology of sympathetic neural control of cardiovascular function with a focus on integrative mechanisms in humans. Direct measurement of sympathetic neural activity (SNA) in humans can be accomplished using microneurography, most commonly performed in the peroneal (fibular) nerve. In humans, muscle SNA (MSNA) is composed of vasoconstrictor fibers; its best-recognized characteristic is its participation in transient, moment-to-moment control of arterial blood pressure via the arterial baroreflex. This property of MSNA contributes to its typical "bursting" pattern which is strongly linked to the cardiac cycle. Recent evidence suggests that sympathetic neural mechanisms and the baroreflex have important roles in the long term control of blood pressure as well. One of the striking characteristics of MSNA is its large interindividual variability. However, in young, normotensive humans, higher MSNA is not linked to higher blood pressure due to balancing influences of other cardiovascular variables. In men, an inverse relationship between MSNA and cardiac output is a major factor in this balance, whereas in women, beta-adrenergic vasodilation offsets the vasoconstrictor/pressor effects of higher MSNA. As people get older (and in people with hypertension) higher MSNA is more likely to be linked to higher blood pressure. Skin SNA (SSNA) can also be measured in humans, although interpretation of SSNA signals is complicated by multiple types of neurons involved (vasoconstrictor, vasodilator, sudomotor and pilomotor). In addition to blood pressure regulation, the sympathetic nervous system contributes to cardiovascular regulation during numerous other reflexes, including those involved in exercise, thermoregulation, chemoreflex regulation, and responses to mental stress.

Screening for sleep dysfunction after traumatic brain injury

Numerous studies on the high prevalence of sleep disorders in individuals with traumatic brain injury (TBI) have been conducted in the past few decades. These disorders can accentuate other consequences of TBI, negatively impacting mood, exacerbating pain, heightening irritability, and diminishing cognitive abilities and the potential for recovery. Nevertheless, sleep is not routinely assessed in this population. In our review, we examined the selective screening criteria and the scientific evidence regarding screening for post-TBI sleep disorders to identify gaps in our knowledge that are in need of resolution. We retrieved papers written in the English-language literature before June 2012 pertinent to the discussion on sleep after TBI found through a PubMed search. Within our research, we found that sleep dysfunction is highly burdensome after TBI, treatment interventions for some sleep disorders result in favorable outcomes, sensitive and specific tests to detect sleep disorders are available, and the cost-effectiveness and sustainability of screening have been determined from other populations. The evidence we reviewed supports screening for post-TBI sleep dysfunction. This approach could improve the outcomes and reduce the risks for post-TBI adverse health and nonhealth effects (e.g., secondary injuries). A joint sleep and brain injury collaboration focusing on outcomes is needed to improve our knowledge.

Obstructive sleep apnea

Obstructive sleep apnea (OSA) affects millions of Americans and is estimated to be as prevalent as asthma and diabetes. Given the fact that obesity is a major risk factor for OSA, and given the current global rise in obesity, the prevalence of OSA will increase in the future. Individuals with sleep apnea are often unaware of their sleep disorder. It is usually first recognized as a problem by family members who witness the apneic episodes or is suspected by their primary care doctor because of the individual's risk factors and symptoms. The vast majority remain undiagnosed and untreated, despite the fact that this serious disorder can have significant consequences. Individuals with untreated OSA can stop breathing hundreds of times a night during their sleep. These apneic events can lead to fragmented sleep that is of poor quality, as the brain arouses briefly in order for the body to resume breathing. Untreated, sleep apnea can have dire health consequences and can increase the risk of hypertension, diabetes, heart disease, and heart failure. OSA management has also become important in a number of comorbid neurological conditions, including epilepsy, stroke, multiple sclerosis, and headache. Diagnosis typically involves use of screening questionnaires, physical exam, and an overnight polysomnography or a portable home study. Treatment options include changes in lifestyle, positive airway pressure, surgery, and dental appliances.

Effect of continuous positive airway pressure therapy on aortic stiffness in patients with obstructive sleep apnea syndrome

OBJECTIVE

The most significant complications seen in patients with obstructive sleep apnea syndrome (OSAS) are associated with the cardiovascular system. The present study assessed aortic stiffness in patients with OSAS and evaluated the effect of continuous positive airway pressure (CPAP) therapy on aortic stiffness.

METHOD

Twenty-four patients with newly diagnosed, previously untreated, moderate or severe OSAS (apnea-hypopnea index > 15) and a control group of 17 healthy patients were included in the study. M-mode recordings of the ascending aorta were taken from the parasternal long axis by echocardiograhy, and systolic and diastolic diameters of the aorta were measured. Aortic elastic parameters, aortic strain, and distensibility were calculated. Measurements were repeated after 6 months of CPAP therapy in patients with OSAS and were compared with baseline values.

RESULTS

In patients with OSAS, compared with the control group, aortic strain (6.7%+/- 2.1% vs. 12.4%+/- 3.1%; P < 0.001) and aortic distensibility (2.8 +/- 0.9 x 10(-6) cm(2) dyn(-1) vs. 5.5 +/- 1.7 x 10(-6) cm(2) dyn(-1); P < 0.001) were evidently lower, and there was a significant correlation between aortic elastic parameters and AHI. After a 6-month course of CPAP therapy, significant increases were observed in aortic strain (6.1%+/- 1.5% vs. 7.3%+/- 1.7%; P < 0.001) and aortic distensibility (2.5 +/- 0.7 x 10(-6) cm(2) dyn(-1) vs. 3.1 +/- 0.9 x 10(-6) cm(2) dyn(-1); P < 0.001) in patients with OSAS.

CONCLUSION

Aortic strain and distensibility were lower in patients with OSAS than in control patients, and CPAP treatment provided improvement in aortic elastic parameters.

[Obstructive sleep apnea contribution to oxidative stress in obesity]

OBJECTIVE

The aim of this paper was to check the influence of obstructive sleep apnea (OSA) on obesity oxidative stress and CPAP (Continuous Positive Airway Pressure) effect on oxidative stress and in these patients.

METHODS

Twenty nine male patients considered obese (BMI > 30 kg/m(2)) were divided into 3 groups: a) Group I: 10 OSA free patients (apnea-hipopnea index (AHI) < 5); b) Group 2: 10 with moderate to serious OSA (AHI > 20); c) Group 3: 9 with OSA from moderate to serious (AHI > 20) using CPAP, minimum 4 hours/night for 2 months.

RESULTS

Significant differences before and after CPAP usage were observed in group 3 in the following variables: reduction of superoxide (SO) production [13.2 (10.3-19.6) vs. 10.5 (5.8-11.8) nmoles O2(-)/2 x 10(6) PMN] and increase in serum nitrite/nitrates levels [24.5 (16.7-33.5) vs. 49.5 (39.3-58.1) microM]. Positive correlation between Apnea-Hypopnea Index (AHI) and SO (r = 0,726) and negative correlation was observed between AHI and serum nitrite/nitrates levels (r = - 0.867).

CONCLUSIONS

In conclusion, oxidative stress present in obesity is elevated by OSA and CPAP treatment can rise the levels of SO and can decrease serum nitrite/nitrates present in obese patients with OSA.

Study into the use of continuous positive airway pressure in obstructive sleep apnoea-hypopnoea syndrome patients with daytime drowsiness

BACKGROUND

Obstructive sleep apnoea-hypopnoea syndrome (OSAHS) is a respiratory disorder with high morbidity and mortality. Continuous positive airway pressure (CPAP) is the most commonly prescribed conservative treatment for adults with OSAHS. CPAP therapy normalises or decreases OSAHS symptoms and can reduce and prevent OSAHS complications.

AIMS

To evaluate adherence to nasal CPAP treatment and CPAP impact on daytime drowsiness.

METHOD

A sample of 20 patients evaluated for daytime drowsiness using the Epworth sleepiness scale and interviewed for adherence to nasal CPAP use.

RESULTS

There was a significant decrease in the level of daytime sleepiness of the patients users of nasal CPAP (p=0.017); patients not using nasal CPAP experienced a decrease without statistical significance (p=0.162). 100% of CPAP users reported benefits and 50% of these reported related discomforts.

CONCLUSIONS

Patients with OSAHS that use CPAP have a greater reduced level of sleepiness than those who do not use it.

Effects of continuous positive airway pressure therapy on left ventricular function assessed by tissue Doppler imaging in patients with obstructive sleep apnoea syndrome

AIMS

In this study, we aimed to assess left ventricular (LV) systolic and diastolic functions by tissue Doppler imaging (TDI) in patients with obstructive sleep apnoea syndrome (OSAS) and to investigate the effects of 6 month continuous positive airway pressure (CPAP) on LV systolic and diastolic functions.

METHODS AND RESULTS

We studied 28 new diagnosed moderate and severe OSAS patients (apnoea-hypopnoea index >15) and 18 control group. Exclusion criteria were the presence of structural heart disease, pulmonary disease, diabetes mellitus, dyslipidaemia, alcoholism, neuromuscular disease, renal failure, or malignancy. They were not previously considered or treated for OSA and were all free of drugs. Left ventricular lateral and septal wall early myocardial peak velocity (Em), late myocardial peak velocity (Am), Em to Am ratio, myocardial relaxation time (RTm), myocardial systolic wave (Sm) velocity, isovolumic acceleration (IVA), myocardial pre-contraction time (PCTm), contraction time (CTm), and PCTm to CTm ratio were measured. All echocardiographic parameters were calculated 6 months after CPAP therapy. No statistically significant difference was detected between the groups according to age, gender, body mass index, systolic and diastolic blood pressure, heart rate, fasting blood glucose, and serum lipid parameters. Left ventricular systolic parameters, such as LV septal and lateral wall IVA, CTm, and PCTm to CTm ratio, were significantly lower and Sm was similar in patients with the OSAS group compared with the controls. Left ventricular diastolic parameters, such as LV septal and lateral wall Em velocity and Em to Am ratio, were significantly lower; RTm was significantly prolonged; and Am velocity was similar in patients with OSAS compared with the controls. At the end of the treatment, 20 of 28 patients were compliant with CPAP therapy. Left ventricular septal and lateral wall Em velocity, Em to Am ratio, IVA and CTm, and PCTm to CTm increased significantly, PCTm, PCTm to CTm ratio, and RTm decreased significantly after the therapy, whereas Sm velocity and Am velocity did not change after CPAP therapy in compliant patients.

CONCLUSION

Left ventricular systolic and diastolic dysfunctions were determined in patients with OSAS, and it was demonstrated that LV systolic and diastolic dysfunctions improved with 6 month CPAP therapy.

Effects of continuous positive airway pressure therapy on right ventricular function assessment by tissue Doppler imaging in patients with obstructive sleep apnea syndrome

OBJECTIVES

The effects of continuous positive airway pressure (CPAP) therapy on right ventricular (RV) function in patients with obstructive sleep apnea syndrome (OSAS) has not been previously studied by tissue Doppler imaging (TDI). The aim of this study was to assess RV function using TDI in patients with OSAS before and after CPAP therapy.

METHODS

Twenty-eight patients with newly diagnosed OSAS in the absence of any confounding factors and 18 controls were included in this study. The peak systolic velocity (S'm), early (E'm) and late (A'm) diastolic myocardial peak velocities at tricuspid lateral annulus, isovolumic acceleration (IVA), myocardial precontraction time (PCT'm), myocardial contraction time (CT'm), and myocardial relaxation time (RT'm) were measured. All echocardiographic parameters were calculated 6 months after CPAP therapy.

RESULTS

The RV diastolic parameters such as E'm velocity and E'm-to-A'm ratio were significantly lower, RT'm was significantly prolonged, A'm velocity was similar in patients with OSAS compared to controls; and the RV systolic parameters such as IVA and CT'm were significantly lower and S'm was similar in patients with OSAS compared to controls. At the end of the treatment, 20 of 28 patients were compliant with CPAP therapy. E'm velocity, E'm-to-A'm ratio, IVA, and CT'm increased, PCT'm, PCT'm-to-CT'm ratio, and RT'm decreased significantly after therapy, whereas S'm velocity and A'm velocity did not change after CPAP treatment in the compliant patients.

CONCLUSION

OSAS is associated with RV systolic and diastolic dysfunction, and 6 months of CPAP therapy improves the RV systolic and diastolic dysfunction.

Association between Erectile Dysfunction and Sleep Disorders Measured by Self‐Assessment Questionnaires in Adult Men

BACKGROUND

Erectile dysfunction (ED) is often associated with sleep disorders and sleep apnea syndrome (SAS) in mostly middle-aged and elderly men. Sleep disorders and ED are also prevalent in younger men.

PURPOSE

To study the association between ED, sleep disorders, and SAS, particularly among adult men.

METHODS

A health screening program is offered by the Israel Defense Force (IDF) for career servicemen older than 25 years, for the purpose of early detection of ED and sleep disorders, among other concealed morbidities. The Sexual Health Inventory for Man questionnaire (SHIM) was used to measure ED. The Sleep Quality (SQ) questionnaire, developed by the medical services of the IDF, was used to characterize SAS and other sleep disorders.

RESULTS

From 2002 through 2003, 3,363 men (mean age, 36.1+/-6.8 years) replied to the SHIM and SQ questionnaires. Of these men, 337 (10%) scored high (>or=25) in the SQ questionnaire, suggesting moderate to severe sleep disorders, and 870 men (25.8%) scored low (<or=21) in the SHIM questionnaire, suggesting ED. There was a negative correlation between the scores in the SHIM questionnaire and in the SQ questionnaire (r=-0.29, P<0.0001)-even after age adjustment and after excluding men with risk factors for both ED and SAS (such as essential hypertension, diabetes mellitus, and obesity; r=-0.21, P<0.0001). This correlation was consistent with all severity levels of ED and sleep disorders.

CONCLUSIONS

Sleep disorders, in particular SAS, and ED are prevalent and may be related in adult men. Either ED or sleep disorders should be considered whenever the other is suspected in adult men. Sleep disorders and ED should also be investigated for the purpose of treating underlying systemic diseases and emotional disorders, and in order to prevent late complications of atherosclerosis.