[Cognitive impairment in obstructive sleep apnea syndrome]

Improved prediction of CPAP failure using T90, age and gender

Sleep apnea syndrome is associated with increased risk of cardiovascular disease. In treating older patients, there is a special emphasis put on minimally invasive and conservative procedures and a simple method for predicting the potential for treatment success is essential. Continuous positive airway pressure (CPAP) is the first choice for treatment, however, it is not always successful. In cases where CPAP was unsuccessful, treatment with bilevel positive airway pressure (BiPAP) is the next treatment option. In this study, we examine commonly evaluated respiratory parameters, obesity, and age relative to their ability to predict CPAP failure. We also tried to find differences in the predictive ability of these parameters in older and younger patients. The predictive ability, relative to CPAP failure, was examined for each individual parameter as well as for combinations of parameters. All variables had a statistical association with CPAP failure; failure prediction reliability ranged from poor to moderate. Combining T90, age, and gender can be used to find patients who will benefit from BiPAP as the first choice for treatment. An initial BiPAP indication can produce relevant reductions in treatment cost.

Abnormal resting-state functional connectivity of amygdala subregions in patients with obstructive sleep apnea

Background: The amygdala is one of the core areas of the emotional circuits. Previous neuroimaging studies have revealed that patients with obstructive sleep apnea (OSA) have aberrant structure and function in several brain areas (including the amygdala). However, the resting-state functional connectivity (rs-FC) of amgydala subregions remains uncertain. Objective: To determine whether aberrant rs-FC exists between the amygdala subregions and other brain areas and whether such abnormalities are related to emotional disorders and cognitive impairment in OSA. Methods: The resting-state functional magnetic resonance imaging (rs-fMRI) data of 40 male severe OSA patients and 40 matched healthy controls (HCs) were collected. The rs-FC between the amygdala subregions and other brain areas was compared between the two groups. The correlations between aberrant rs-FC and clinical variables and neuropsychological assessments were evaluated. Results: Compared with the HCs, the OSA patients showed significantly increased rs-FC between the left dorsal amygdala (DA) and the anterior lobe of the cerebellum, among the left ventrolateral amygdala (VA), the left inferior frontal gyrus (IFG) and the left superior temporal gyrus (STG), and between the right VA and the left IFG. However, significantly decreased rs-FC was observed between the right DA and the right prefrontal cortex (PFC) in OSA patients. No regional differences in rs-FC were found between the OSA patients and HCs in the bilateral medial amygdala (MA). Conclusion: In this study, male severe OSA patients showed complex rs-FC patterns in the amygdala subregions, which may be the result of OSA-related selective damage to the amygdala, and abnormal rs-FC between the amygdala subregions and brain regions associated with emotional, cognitive and executive functions may partly explain the affective deficits and cognitive impairment observed in male severe OSA patients.

Oronasal mask may compromise the efficacy of continuous positive airway pressure on OSA treatment: is there evidence for avoiding the oronasal route?

PURPOSE OF REVIEW

Continuous positive airway pressure (CPAP) delivered by nasal mask is the gold standard treatment for obstructive sleep apnea (OSA). However, oral and oronasal masks are also available. We considered experimental evidence and reviewed clinical trials that evaluated the impact of oral and oronasal mask on OSA treatment.

RECENT FINDINGS

One recent study in 18 OSA patients that slept with a customized oronasal mask with two sealed compartments showed that the change of CPAP flow from nasal to oronasal and oral caused upper airway obstruction because of posterior displacement of the tongue demonstrated by nasoendoscopy. Oral masks use a mouthpiece that may stabilize the jaw and the tongue and have shown to be effective. However, oral masks are not widely used in clinical practice. Four out of five observational studies and all five reviewed randomized studies showed a worse performance of oronasal when compared with nasal masks. Oronasal masks were associated with higher residual apnea-hypopnea index, lower adherence, more leaks, and less satisfaction than nasal mask in the majority of the studies.

SUMMARY

Nasal CPAP must be the first choice to treat OSA. Patients on oronasal mask should be carefully followed. VIDEO ABSTRACT.

Fluid Redistribution in Sleep Apnea: Therapeutic Implications in Edematous States

Sleep apnea (SA), a condition associated with increased cardiovascular risk, has been traditionally associated with obesity and aging. However, in patients with fluid-retaining states, such as congestive heart failure and end-stage renal disease, both prevalence and severity of SA are increased. Recently, fluid shift has been recognized to play an important role in the pathophysiology of SA, since the fluid retained in the legs during the day shifts rostrally while recumbent, leading to edema of upper airways. Such simple physics, observed even in healthy individuals, has great impact in patients with fluid overload. Correction of the excess fluid volume has risen as a potential target therapy to improve SA, by attenuation of nocturnal fluid shift. Such strategy has gained special attention, since the standard treatment for SA, the positive airway pressure, has low compliance rates among its users and has failed to reduce cardiovascular outcomes. This review focuses on the pathophysiology of edema and fluid shift, and summarizes the most relevant findings of studies that investigated the impact of treating volume overload on SA. We aim to expand horizons in the treatment of SA by calling attention to a potentially reversible condition, which is commonly underestimated in clinical practice.

Impact of the type of mask on the effectiveness of and adherence to continuous positive airway pressure treatment for obstructive sleep apnea

Continuous positive airway pressure (CPAP) is the gold standard for the treatment of obstructive sleep apnea (OSA). Although CPAP was originally applied with a nasal mask, various interfaces are currently available. This study reviews theoretical concepts and questions the premise that all types of interfaces produce similar results. We revised the evidence in the literature about the impact that the type of CPAP interface has on the effectiveness of and adherence to OSA treatment. We searched the PubMed database using the search terms "CPAP", "mask", and "obstructive sleep apnea". Although we identified 91 studies, only 12 described the impact of the type of CPAP interface on treatment effectiveness (n = 6) or adherence (n = 6). Despite conflicting results, we found no consistent evidence that nasal pillows and oral masks alter OSA treatment effectiveness or adherence. In contrast, most studies showed that oronasal masks are less effective and are more often associated with lower adherence and higher CPAP abandonment than are nasal masks. We concluded that oronasal masks can compromise CPAP OSA treatment adherence and effectiveness. Further studies are needed in order to understand the exact mechanisms involved in this effect.

Relationship between brain-derived neurotrophic factor and cognitive function of obstructive sleep apnea/hypopnea syndrome patients

OBJECTIVE

To determine the relationship between the blood serum brain-derived neurotrophic factor (BDNF) level and cognitive function deterioration in patients with obstructive sleep apnea/hypopnea syndrome (OSAHS), and to explore the possible mechanism of cognitive impairment.

METHODS

Twenty-eight male OSAHS patients and 14 normal males (as controls) were enrolled in the study. Polysomnography and the Montreal cognitive assessment (MoCA) were conducted. The blood serum BDNF levels were measured using ELISA.

RESULTS

The OSAHS group had significantly decreased blood serum BDNF levels compared with the control group (t = -10.912, P = 0.000). The blood serum BDNF level of the subjects was significantly positively associated with the MoCA score (r = 0.544, P = 0.000), significantly negatively associated with the apnea-hypopnea index (AHI) and shallow sleep (S1+S2) (AHI: r = -0.607, P = 0.000; S1+S2: r = -0.768, P = 0.000), and significantly positively associated with the lowest SaO(2) (LSO), slow wave sleep (S3+S4), and rapid eye movement sleep (REM) (LSO: r = 0.566, P = 0.000; S3+S4: r = 0.778, P = 0.000; REM: r = 0.575, P = 0.000).

CONCLUSIONS

OSAHS patients have significantly decreased blood serum BDNF levels compared with the control. Nocturnal hypoxia as well as the deprivation of slow wave sleep and REM may lead to the decreased serum BDNF level of OSAHS patients. This decreased blood serum BDNF level may contribute to the cognitive impairment in OSAHS.

Altered cortical and subcortical local coherence in obstructive sleep apnea: a functional magnetic resonance imaging study

Obstructive sleep apnea (OSA) syndrome is the most common sleep-related breathing disorder, characterized by excessive snoring and repetitive apneas and arousals, which leads to fragmented sleep and, most importantly, to intermittent nocturnal hypoxaemia during apneas. Considering previous studies about morphovolumetric alterations in sleep apnea, in this study we aimed to investigate for the first time the functional connectivity profile of OSA patients and age-gender-matched healthy controls, using resting-state functional magnetic resonance imaging (fMRI). Twenty severe OSA patients (mean age 43.2 ± 8 years; mean apnea-hypopnea index, 36.3 h(-1) ) and 20 non-apneic age-gender-body mass index (BMI)-matched controls underwent fMRI and polysomnographic (PSG) registration, as well as mood and sleepiness evaluation. Cerebro-cerebellar regional homogeneity (ReHo) values were calculated from fMRI acquisition, in order to identify pathology-related alterations in the local coherence of low-frequency signal (<0.1 Hz). Multivariate pattern classification was also performed using ReHo values as features. We found a significant pattern of cortical and subcortical abnormal local connectivity in OSA patients, suggesting an overall rearrangement of hemispheric connectivity balance, with a decrease of local coherence observed in right temporal, parietal and frontal lobe regions. Moreover, an increase in bilateral thalamic and somatosensory/motor cortices coherence have been found, a finding due possibly to an aberrant adaptation to incomplete sleep-wake transitions during nocturnal apneic episodes, induced by repetitive choke sensation and physical efforts attempting to restore breathing. Different hemispheric roles into sleep processes and a possible thalamus key role in OSA neurophysiopathology are intriguing issues that future studies should attempt to clarify.