Cardiovascular consequences of sleep-related breathing disorders

Probable Change of Sleep Parameters after Resection and Reconstruction Surgeries in Patients with Oral Cavity or Oropharyngeal Cancers

In patients of oral cavity or oropharyngeal cancers, resection of the tumor and reconstruction of the defect may reduce the framework, add a bulky flap, alter the tissue flexibility, and contribute to postoperative obstructive sleep apnea (OSA). Postoperative OSA and the potential consequences may decrease the survival rate and reduce patients' quality of life. It is unclear whether the surgery is associated with postoperative OSA. Here, we compared the polysomnographies (PSGs) before and after the surgery in 15 patients of oral cavity or oropharyngeal cancers (out of 68 patients of head and neck cancers) without a chemo- or radio-therapy. Each patient received the second PSG before the start of any indicated adjuvant therapy to prevent its interference. There were 14 men and 1 woman, with a mean age and a standard deviation (SD, same in the following) of 56.2 ± 12.8 years. There were 6 tongue cancers, 5 buccal cancers, 2 tonsil cancer, 1 lower gum cancer, and 1 trigone cancer. The results show that the surgery changed sleep parameters insignificantly in apnea-hypopnea index (AHI), mean oxyhemoglobin saturation of pulse oximetry (SpO2), minimum SpO2, mean desaturation, and desaturation index but increased mean heart rate in the patients with free flaps. These results hint that the effect of surgery on developing OSA was small in this sample, with a longer plate or a larger framework for a bulkier free flap. It needs future studies with a large sample size to generalize this first observation.

Difficulty of falling asleep and non-high-density lipoprotein cholesterol level among Canadian older adults: a cross-sectional analysis of the Canadian Longitudinal Study for Aging baseline data

OBJECTIVE

To examine whether difficulty of falling asleep (DoFA) is associated with non-high-density lipoprotein cholesterol (non-HDL-C) level among Canadian older adults.

METHODS

26,954 individuals aged 45–85 years from the baseline data of the Canadian Longitudinal Study for Aging were included in this study. DoFA was categorized into five groups by answer to the question “Over the last month, how often did it take you more than 30 min to fall asleep?” Response options are “Never, < 1 time/week, 1−2 times/week, 3−5 times/week, or 6−7 times/week”. Non-HDL-C, the difference of total cholesterol and HDL-C, were categorized into five categories based on these cut-offs (< 2.6 mmol/L, 2.6−3.7 mmol/L, 3.7−4.8 mmol/L, 4.8−5.7 mmol/L, and ≥ 5.7 mmol/L). Ordinal logistic regression (logit link) continuation ratio models were used to estimate the odds of higher non-HDL-C levels for DoFA status. Adjusted means of non-HDL-C by DoFA status were estimated by general linear models. All analyses were sex separately using analytic weights to ensure generalizability.

RESULTS

The proportions of DoFA in five categories were 41.6%, 25.7%, 13.6%, 9.4%, 9.7% for females and 52.9%, 24.9%, 10.5%, 6.1%, 5.6% for males, respectively. After adjustment of demographical and other covariates (such as depression, comorbidity, sleeping hour, etc.) compared to those who reported never having DoFA, the ORs (95% CIs) of higher levels of non-HDL-C for those whose DoFA status in < 1 time/week, 1−2 times/week, 3−5 times/week, and 6−7 times/week were 1.12 (1.05−1.21), 1.09 (0.99−1.18), 1.20 (1.09−1.33), 1.29 (1.17−1.43) in females and 1.05 (0.98−1.13), 0.95 (0.87−1.05), 1.21 (1.08−1.37), 0.97 (0.85−1.09) in males, respectively. The adjusted means of non-HDL-C among the five DoFA status were 3.68 mmol/L, 3.73 mmol/L, 3.74 mmol/L, 3.82 mmol/L, 3.84 mmol/L for females and 3.54 mmol/L, 3.58 mmol/L, 3.51 mmol/L, 3.69 mmol/L, 3.54 mmol/L for males, respectively.

CONCLUSIONS

The results of this study have identified a risk association pattern between DoFA status and non-HDL-C levels in females but not in males. Further research is needed to confirm these findings.

Shifting and reducing breathing disturbance in patients with very severe obstructive sleep apnea by modified Z-palatoplasty with one-layer closure in one-stage multilevel surgery

Very severe obstructive sleep apnea (OSA) with apnea-hypopnea index (AHI) ≥ 60 events/h differs in several areas from OSA with other severities, including having a low-level daytime partial pressure of oxygen and residual on-CPAP (continuous positive airway pressure) AHIs greater than 20/h. Patients with very severe OSA show narrow retroglossal space and confined framework, which is difficult to be enlarged via conventional Uvulopalatopharyngoplasty (UPPP) surgery, resulting in poor response to non-framework surgeries. Our latest report showed efficacy and efficiency for subjects undergoing modified Z-palatoplasty (ZPP) with one-layer closure in a one-stage multilevel surgery. It is unclear whether and how this procedure could help patients with very severe OSA characterized with confined framework. From Mar. 2015 to May 2018, we enrolled 12 patients with very severe OSA receiving one-stage multi-level surgery with modified ZPP with one-layer closure, CO2 laser partial tongue-base glossectomy, and bilateral septomeatoplasty. Our results show that the surgery reduced AHI from 73.8 ± 10.7 to 30.8 ± 23.2 events/h and achieved a mean AHI reduction of 58.3% (p < 0.001 against 0 reduction or no surgery). The surgery shifted components of the breathing disturbances. It reduced more apnea than hypopnea and might convert some apnea to hypopnea.

Effects of six weeks high-intensity interval training and resistance training in adults with obesity and sleep related breathing disorders

Introduction

The effects of high-intensity interval training (HIIT) combined with resistance training (RT) in adults with obesity and sleep-related breathing disorders (SRBDs) is limited.

Objective

This study aimed to examine the effects of HIIT combined with RT on subjective sleep disorders in adults with obesity and SRBDs.

Material and Methods

This study was a pre- and post-test design. Seventeen adults with obesity and SRBDs were recruited into the study. They received 24 minutes of HIIT and 30 minutes of RT, 3 times/week for 6 weeks. The Epworth sleepiness scale (daytime sleepiness), Berlin questionnaire (snoring and daytime sleepiness category), estimated maximum oxygen consumption (VO₂max), muscle strength using 1-repetition maximum, anthropometric variables, and blood biomarkers were examined at baseline and after 6 weeks of training.

Results

The Epworth sleepiness scale, Berlin questionnaire (daytime sleepiness category), and the number of risks associated with sleep apnea using the Berlin questionnaire were significantly decreased after 6 weeks of training (all p<0.01). The estimated VO₂max and muscle strength were significantly increased at Week 6 (all p<0.05). Body weight, body mass index, % body fat, and hip circumference were significantly decreased at Week 6 (all p<0.05). No significant changes were observed in blood biomarkers, except for fasting blood glucose (p<0.01).

Conclusion

Six weeks of HIIT combined with RT has beneficial effects on subjective sleep disorders, estimated VO₂max, muscle strength, and most anthropometric variables in adults with obesity and SRBDs.

Increasing Hypopnea in Sleep Breathing Disturbance Improves Postoperative Oxygen Saturation in Patients with Very Severe Obstructive Sleep Apnea

In patients of very severe obstructive sleep apnea (OSA) with confined framework, reducing volume is difficult to achieve a postoperative apnea-hypopnea index (AHI) qualifying the classical surgical success. However, a higher AHI with a larger part of hypopneas may have similar or even less severity of oxygen (O2) desaturation, compared to a lower index mostly made of apneas. Here, in 27 consecutive enrolled patients, we show that besides the improvement of mean AHI, the multilevel surgery increased hypopnea in AHI from 29.1% to 77.3%, and improves postoperative O2 saturation by reducing desaturation frequency (mean desaturation index decreased from 62.5 to 24.4 events/h) and level (mean oxyhemoglobin saturation of pulse oximetry (SpO2) desaturation cut down from 10.0 to 5.8%). The mean SpO2 improved from 92.3% to 94.7%, and the improvement was positively related to the proportion increase of hypopnea/AHI. The results suggest that the non-framework surgery could help patients with very severe OSA whose AHIs are ≥60 events/h in terms of improving postoperative O2 saturation. Due to the improvement also presented in those not qualified as classical surgical success, further studies are needed to clarify the connection between O2 desaturation and various consequences to reconsider defining a surgical success.

Effects of cyclic intermittent hypoxia on ET-1 responsiveness and endothelial dysfunction of pulmonary arteries in rats

Obstructive sleep apnoea (OSA) is a risk factor for cardiovascular disorders and in some cases is complication of pulmonary hypertension. We simulated OSA by exposing rats to cyclic intermittent hypoxia (CIH) to investigate its effect on pulmonary vascular endothelial dysfunction. Sprague-Dawley Rats were exposed to CIH (FiO₂ 9% for 1 min, repeated every 2 min for 8 h/day, 7 days/wk for 3 wk), and the pulmonary arteries of normoxia and CIH treated rats were analyzed for expression of endothelin-1 (ET-1) and ET receptors by histological, immunohistochemical, RT-PCR and Western Blot analyses, as well as for contractility in response to ET-1. In the pulmonary arteries, ET-1 expression was increased, and ET-1 more potently elicited constriction of the pulmonary artery in CIH rats than in normoxic rats. Exposure to CIH induced marked endothelial cell damage associated with a functional decrease of endothelium-dependent vasodilatation in the pulmonary artery. Compared with normoxic rats, ET_A receptor expression was increased in smooth muscle cells of the CIH rats, while the expression of ET_B receptors was decreased in endothelial cells. These results demonstrated endothelium-dependent vasodilation was impaired and the vasoconstrictor responsiveness increased by CIH. The increased responsiveness to ET-1 induced by intermittent hypoxia in pulmonary arteries of rats was due to increased expression of ET_A receptors predominantly, meanwhile, decreased expression of ET_B receptors in the endothelium may also participate in it.

Association of plasma homocysteine with self-reported sleep apnea is confounded by age: results from the national health and nutrition examination survey 2005-2006

High levels of plasma homocysteine are implicated in the pathogenesis of cardiovascular diseases especially if accompanied by sleep apnea, but a direct pathogenetic link between plasma homocysteine levels and obstructive sleep apnea is debatable. This association can have far-reaching public health implications considering the inverse association between folate and plasma homocysteine. We used data from the 2005-2006 cycle of the National Health and Nutrition Examination Survey (NHANES) to test the hypothesized associations. Of the 4490 subjects included in analysis, 177 reported sleep apnea. Age-standardized and design-effect-corrected prevalence rates were differential across gender, plasma homocysteine, and red cell folate status. Plasma homocysteine was positively correlated with age (r = 0.38, P < 0.0001). Multivariate analyses using sociodemographic and clinical covariates demonstrated that plasma homocysteine levels retained their respective associations with self-reported sleep apnea in all models except when age was included as a covariate. Our results demonstrate that the claimed association of plasma homocysteine with sleep apnea may be confounded by age.

Mechanisms of intermittent hypoxia induced hypertension

Exposing rodents to brief episodes of hypoxia mimics the hypoxemia and the cardiovascular and metabolic effects observed in patients with obstructive sleep apnoea (OSA), a condition that affects between 5% and 20% of the population. Apart from daytime sleepiness, OSA is associated with a high incidence of systemic and pulmonary hypertension, peripheral vascular disease, stroke and sudden cardiac death. The development of animal models to study sleep apnoea has provided convincing evidence that recurrent exposure to intermittent hypoxia (IH) has significant vascular and haemodynamic impact that explain much of the cardiovascular morbidity and mortality observed in patients with sleep apnoea. However, the molecular and cellular mechanisms of how IH causes these changes is unclear and under investigation. This review focuses on the most recent findings addressing these mechanisms. It includes a discussion of the contribution of the nervous system, circulating and vascular factors, inflammatory mediators and transcription factors to IH-induced cardiovascular disease. It also highlights the importance of reactive oxygen species as a primary mediator of the systemic and pulmonary hypertension that develops in response to exposure to IH.

Oxidant and redox signaling in vascular oxygen sensing: implications for systemic and pulmonary hypertension

It has been well known for >100 years that systemic blood vessels dilate in response to decreases in oxygen tension (hypoxia; low PO2), and this response appears to be critical to supply blood to the stressed organ. Conversely, pulmonary vessels constrict to a decrease in alveolar PO2 to maintain a balance in the ventilation-to-perfusion ratio. Currently, although little question exists that the PO2 affects vascular reactivity and vascular smooth muscle cells (VSMCs) act as oxygen sensors, the molecular mechanisms involved in modulating the vascular reactivity are still not clearly understood. Many laboratories, including ours, have suggested that the intracellular calcium concentration ([Ca2+]i), which regulates vasomotor function, is controlled by free radicals and redox signaling, including NAD(P)H and glutathione (GSH) redox. In this review article, therefore, we discuss the implications of redox and oxidant alterations seen in pulmonary and systemic hypertension, and how key targets that control [Ca2+]i, such as ion channels, Ca2+ release from internal stores and uptake by the sarcoplasmic reticulum, and the Ca2+ sensitivity to the myofilaments, are regulated by changes in intracellular redox and oxidants associated with vascular PO2sensing in physiologic or pathophysiologic conditions.

Eucapnic intermittent hypoxia augments endothelin-1 vasoconstriction in rats: role of PKCdelta

We reported previously that simulating sleep apnea by exposing rats to eucapnic intermittent hypoxia (E-IH) causes endothelin-dependent hypertension and increases constrictor sensitivity to endothelin-1 (ET-1). In addition, augmented ET-1-induced constriction in small mesenteric arteries (sMA) is mediated by increased Ca(2+) sensitization independent of Rho-associated kinase. We hypothesized that exposing rats to E-IH augments ET-1-mediated vasoconstriction by increasing protein kinase C (PKC)-dependent Ca(2+) sensitization. In sMA, the nonselective PKC inhibitor GF-109203x (3 microM) significantly inhibited ET-1-stimulated constriction in E-IH arteries but did not affect ET-1-stimulated constriction in sham arteries. Phospholipase C inhibitor U-73122 (1 microM) also inhibited constriction by ET-1 in E-IH but not sham sMA. In contrast, the classical PKC (cPKC) inhibitor Gö-6976 (1 microM) had no effect on ET-1-mediated vasoconstriction in either group, but a PKCdelta-selective inhibitor (rottlerin, 3 microM) significantly decreased ET-1-mediated constriction in E-IH but not in sham sMA. ET-1 increased PKCdelta phosphorylation in E-IH but not sham sMA. In contrast, ET-1 constriction in thoracic aorta from both sham and E-IH rats was inhibited by Gö-6976 but not by rottlerin. These observations support our hypothesis that E-IH exposure significantly increases ET-1-mediated constriction of sMA through PKCdelta activation and modestly augments ET-1 contraction in thoracic aorta through activation of one or more cPKC isoforms. Therefore, upregulation of a PKC pathway may contribute to elevated ET-1-dependent vascular resistance in this model of hypertension.

Sleep‐Disordered Breathing and the Association With Cardiovascular Risk

Breathing-related sleep disorders, particularly obstructive sleep apnea, have been largely undiagnosed in people with cardiovascular disease, probably due to limited health care provider awareness of the association between the two conditions. Solid evidence is emerging that the apneic events that occur during sleep lead to acute and chronic hemodynamic changes during wake time, including elevated sympathetic tone, decreased stroke volume and cardiac output, increased heart rate, and changes in circulating hormones that regulate blood pressure, fluid volume, vasoconstriction, and vasodilation. Obstructive sleep apnea is associated with known cardiovascular risk factors such as obesity and hyperlipidemia, and is considered by many sleep clinicians to be an independent risk factor for hypertension. Additionally, sleep apnea has been implicated in the pathogenesis of heart failure and stroke. Treatment with positive airway pressure during sleep eliminates the apneic events and the ensuing acute hemodynamic changes. Improvements in daytime blood pressure and left ventricular function also have been noted in persons with hypertension and heart failure. Because effective treatment is available for sleep apnea, this condition needs to be diagnosed and treated in persons with cardiovascular disease.

Palatal and tongue base surgery for surgical treatment of obstructive sleep apnea: a prospective study

OBJECTIVE

To assess the effect of concurrent uvulopalatopharyngoplasty (UPPP) and hypopharyngeal procedures in obstructive sleep apnea (OSA) patients with diffuse airway narrowing.

STUDY DESIGN AND SETTING

Forty-eight patients were treated surgically by a single surgeon in private practice over 2 years. Symptoms, Epworth score, and polysomnographic outcome were assessed preoperatively and postoperatively. The Friedman staging system was applied. UPPP with genioglossus advancement, hyoid suspension, or radiofrequency treatment was carried out.

RESULTS

In 37 patients with complete data, the average apnea-hypopnea index (AHI) was reduced from 46.5 +/- 24.8 to 14.9 +/- 16.8. The Epworth score was reduced from 12.1 +/- 4.9 to 6.7 +/- 3.7. Most patients reported improved sleep quality, alertness, memory, concentration, and mood.

CONCLUSION

Successful outcome, defined by symptom and AHI reduction, was achieved with multilevel surgery for most patients with advanced Friedman stages 2 and 3.

SIGNIFICANCE

Multilevel surgery seems effective in treating severe OSA patients with diffuse airway narrowing.

EBM RATING

C-4.

A case of achondroplasia with severe pulmonary hypertension due to obstructive sleep apnea

Achondroplasia is the most common skeletal dysplasia in children. Achondroplasic patients have a short cranial face and midface hypoplasia. They often have sleep-related respiratory disturbances that lead to hypoxemia caused by midfacial hypoplasia, a small upper airway, hypotonia of airway muscles, or brain stem compression. It has been well described that obstructive sleep apnea can cause pulmonary hypertension (PH) through the mechanism of chronic hypoxemia. However, severe PH due to obstructive-type sleep disorder is rare in patients with achondroplasia. In this report, we describe a 5-year-old girl with achondroplasia whose severe PH was caused by upper-airway obstruction and was resolved gradually after adenotonsillectomy.

Serum homocysteine levels and cardiovascular morbidity in obstructive sleep apnea syndrome

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is associated with cardiovascular morbidity and mortality. Elevated levels of serum homocysteine are also associated with cardiovascular morbidity and mortality. We aimed to investigate serum homocysteine levels and conventional cardiovascular risk factors (cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglycerides) in OSAS patients with and without cardiovascular diseases (CVD).

METHODS AND RESULTS

Levels of homocysteine, cholesterol, LDL, HDL and triglycerides were measured in 114 obese, male participants after overnight fasting. The presence of OSAS was determined by standard overnight polysomnography. The cases included OSAS patients (apnea-hypopnea index: AHI5) with CVD (OSAS+CVD group) (n:25) and without CVD (OSAS-CVD group) (n:47). Control group was patients without OSAS (AHI<5) with CVD (CVD group) (n:42). The serum homocysteine levels were significant.

Prevalence of Moderate or Severe Left Ventricular Diastolic Dysfunction in Obese Persons with Obstructive Sleep Apnea

We investigated prior to gastric bypass surgery the prevalence of left ventricular diastolic dysfunction (LVDD) by Doppler and tissue Doppler echocardiography in 14 obese women and in 6 obese men, mean age 45 years, with a mean body mass index of 49+/-5 kg/m2 who had nocturnal polysomnography for obstructive sleep apnea (OSA). The Doppler and tissue Doppler echocardiographic data were analyzed blindly without knowledge of the clinical characteristics or whether OSA was present or absent. Of 20 patients, 8 (40%) had no OSA, 4 (20%) had mild OSA, and 8 (40%) had moderate or severe OSA. Moderate or severe LVDD was present in 4 of 8 patients (50%) with moderate or severe OSA and in none of 12 patients (0%) with no or mild OSA (p<0.01). Obese patients with moderate or severe OSA have a higher prevalence of moderate or severe LVDD than obese patients with no or mild OSA.

Augmented Endothelin Vasoconstriction in Intermittent Hypoxia-Induced Hypertension

We reported previously that simulating sleep apnea in rats by exposing them 7 hours per day to intermittent hypoxia/hypercapnia (IH) elevates plasma endothelin-1 and causes hypertension, which is reversed by an endothelin-1 antagonist. We hypothesized that in this model of sleep apnea–induced hypertension, vascular sensitivity to endothelin-1 is increased in combination with the elevated plasma endothelin-1 to cause the endothelin-1–dependent hypertension. In small mesenteric arteries with endothelial function disabled by passing air through the lumen, diameter and vessel wall [Ca 2+ ] were recorded simultaneously. IH arteries demonstrated increased constrictor sensitivity to endothelin-1 (percentage max constriction 100±0% IH versus 80±10% Sham; P <0.05). This was accompanied by increased calcium sensitivity of IH arteries. In contrast, constrictor sensitivity and increases in vessel wall [Ca 2+ ] to KCl and phenylephrine were not different between IH and Sham arteries. We have shown previously that endothelin-1 constriction in mesenteric arteries is mediated by endothelin A receptors. In the current study, the selective increase in endothelin-1 constriction in IH resistance arteries was accompanied by increased expression of endothelin A receptor expression (densitometry units 271±23 IH versus 158±25 Sham; P <0.05). Thus, IH hypertension appears to cause alterations in signaling components unique to endothelin-1 at the receptor level and in postreceptor signaling that increases calcium sensitivity during endothelin A activation. Future studies will determine the specific changes in vascular smooth muscle signaling in IH hypertension causing this augmented contractile phenotype.

Efficacy and co-morbidity of oral appliances in the treatment of obstructive sleep apnea-hypopnea: a systematic review

The Obstructive Sleep Apnea-Hypopnea Syndrome (OSAHS) is a common sleep-related breathing disorder characterized by repetitive obstructions of the upper airway during sleep. Modification of pharyngeal patency by Oral Appliance (OA) therapy has been suggested as an alternative to various treatment modalities for OSAHS. To determine the evidence base with respect to the efficacy and co-morbidity of OA therapy in OSAHS, we conducted a systematic review of the available literature. Primary outcome measures were the reduction in number of upper-airway obstructions and co-morbidity related to the craniomandibular or craniofacial complex, respectively. Eligible studies regarding efficacy were independently assessed by two assessors using a quality assessment scale. Effect sizes of methodologically sound studies were calculated. In identical interventions, effect sizes were pooled with the use of a random-effects model. Given the scarcity of controlled studies related to co-morbidity, appraisal was confined to a description of eligible studies. Sixteen controlled trials related to efficacy were identified. With respect to the primary outcome measure, OA therapy was clearly more effective than control therapy (pooled effect size, -0.96; 95% confidence interval [CI], -1.49 to -0.42) and possibly more effective than uvulopalatopharyngoplasty. Although patients generally preferred OA therapy, improvement of respiratory variables, such as the number of upper-airway obstructions, was usually better in Continuous Positive Airway Pressure (CPAP) therapy (pooled effect size, 0.83; 95% CI, 0.59 to 1.06). Moreover, specific aspects related to OA design may influence patient-perceived efficacy and preference. Twelve patient-series and one controlled trial related to co-morbidity were identified. Analysis of the data suggests that OA therapy may have adverse effects on the craniomandibular and craniofacial complex. Although CPAP is apparently more effective and adverse effects of OA treatment have been described, it can be concluded that OA therapy is a viable treatment for, especially, mild to moderate OSAHS. Controlled studies addressing the specific indication and co-morbidity of OA therapy are warranted.

Autonomic dysregulation as a basis of cardiovascular, endocrine, and inflammatory disturbances associated with obstructive sleep apnea and other conditions of chronic hypoxia, hypercapnia, and acidosis

Obstructive sleep apnea has traditionally been viewed as a structural disease. A multitude of systemic endocrine and cardiovascular abnormalities have been previously attributed to the prevalence of obesity in these patients. A growing body of clinical evidence, however, points to a relationship between sleep apnea and its systemic abnormalities independent of obesity. We hypothesize that this association is based on a maladaptive autonomic response of chemoreceptors, reacting to the hypoxia, hypercapnia, and acidosis of sleep apnea. The elevated sympathetic response triggers an inflammatory cascade that results in a myriad of downstream consequences including insulin resistance, hypertension, diabetes, atherosclerosis and metabolic syndrome. The sympathetic bias and endocrine disturbances may further exacerbate sleep disturbance in a potentially pernicious cycle. Our proposal may extend to any chronic respiratory or metabolic conditions that manifest hypoxia, hypercapnia, and acidosis and elicit a maladaptive autonomic and inflammatory response.