[Show abstract][Hide abstract] ABSTRACT: Visceral adipose tissue (VAT) is associated with abnormal cardiovascular and metabolic profiles. Total VAT volume of the abdominal compartment by magnetic resonance imaging (MRI) is the gold-standard measurement for VAT but is costly and time consuming. Prior studies suggest VAT area on a single slice MR image may serve as a surrogate for total VAT volume but it is unknown if this relationship is maintained in overweight and obese men and women. Untreated sleep apnea subjects enrolled into the Icelandic Sleep Apnea Cohort (ISAC) underwent abdominal MRI. VAT area and subcutaneous adipose tissue (SAT) area at the L2-L3 and L4-L5 interspaces and total VAT and SAT volumes were determined by manual examination using image analysis software; 539 men and 129 women with mean ages of 54.1 and 58.8 years and mean BMI of 32.2 kg/m(2) and 33.7 kg/m(2), respectively, were studied. Mean total VAT volume was 40% smaller and mean total SAT was 25% larger among females compared with males. The correlation with VAT volume was significantly larger for L2-L3 VAT area (r = 0.96) compared to L4-L5 VAT area (r = 0.83). The difference in correlation coefficients was statistically significant (nonparametric bootstrap P < 0.001 with 95% confidence interval (CI) for the difference from 0.11 to 0.15. VAT area at L2-L3 was also significantly better correlated with VAT volume than traditional anthropometric variables. Linear regression analyses demonstrated that L2-L3 area alone was sufficient for predicting total VAT volume and that the nature of the linear association was maintained across all levels of obesity and in both genders.
[Show abstract][Hide abstract] ABSTRACT: Noninvasive ventilation (NIV) has become a proven and accepted treatment for respiratory failure from a variety of underlying causes. NIV during sleep can improve gas exchange in both acute and chronic respiratory failure. During sleep, numerous physiologic changes take place that increase the work of breathing and can therefore worsen sleep quality. These include decrements in tidal volume, worsening of gas exchange, and altered lung mechanics. While institution of NIV has been shown to improve nocturnal Paco2 and Pao2 levels and reduce the work of breathing, less is known regarding its effects on sleep and sleep quality. This article reviews data from case series, uncontrolled studies, randomized clinical trials, and meta-analyses. While there is some controversy, the predominance of data suggests that NIV can significantly improve several measures of sleep quality and duration in patients with chronic respiratory failure from numerous underlying causes. Studies have demonstrated improvements in total sleep time, sleep efficiency, subjective sleep quality, and overall quality of life in patients using NIV. In patients with the obesity hypoventilation syndrome, NIV is a cornerstone of therapy, improving daytime hypersomnolence as well as gas exchange. The data for NIV in patients with chronic obstructive pulmonary disease are conflicting and it is unclear if these patients have overall improvements with NIV use. Implementation of chronic NIV is discussed, along with indications and contraindications to therapy.
Sleep Medicine Clinics 12/2008; 3(4):557-568. DOI:10.1016/j.jsmc.2008.08.002
[Show abstract][Hide abstract] ABSTRACT: Obstructive sleep apnea continues to be a significant public health problem. A variety of imaging modalities have been used recently to gain insight into the pathogenesis of this disease, as well as to identify therapeutic options.
Data from more recent imaging studies have highlighted key findings regarding the anatomic sites of collapse and local tissue factors promoting upper airway compromise. The role of genetics, aging, gender and ethnicity in the development of sleep apnea and the identification of predictors for successful treatment outcomes for sleep-disordered breathing are also reviewed.
As our understanding of obstructive sleep apnea evolves, newer imaging techniques and computerized models may be able to further enhance our understanding of the pathogenesis and treatment of this disease.
Current opinion in pulmonary medicine 12/2006; 12(6):397-401. DOI:10.1097/01.mcp.0000245706.77064.51 · 2.76 Impact Factor