Increased microcirculatory heterogeneity in patients with obstructive sleep apnea

[Obstructive sleep apnea in cardiology clinical practice. Epidemiology, diagnosis, and treatment. Observational, cross-sectional, retrospective study]

Objective

To determine the clinical-epidemiological characteristics, diagnostic feasibility of home respiratory polygraphy and treatment of patients with suspected obstructive sleep apnea (OSA) at cardiovascular risk.

Methods

An observational, cross-sectional, descriptive study was conducted in patients seen in a cardiology outpatient service with suspected OSA, from January 2015 to December 2019. The information was obtained from medical records, and a descriptive statistical analysis was applied to this information.

Results

138 files were reviewed; only 8% of the home respiratory polygraphs were discarded, because they did not meet the required quality standards. It was demonstrated that 89% suffered from OSA, 60% moderate to severe; in men after 50 years of age. The main cardiovascular risk factors was hypertension (89%). The most prevalent heart disease was hypertension (52%). Cardiovascular pharmacological treatment was improved in 82% of the cases. Cardiac rehabilitation in 30%, noninvasive mechanical ventilation 41%, fixed modality 33%, and self-adjustable 9%, all with telemetry.

Conclusions

The prevalence and severity of OSA is higher in the presence of risk or established cardiovascular disease. In the presence of clinical suspicion, it is feasible to confirm the diagnosis with home respiratory poligrafy due to the level of precision and the lower infrastructure required. Greater involvement of the cardiologist in the diagnosis and treatment of this disorder is necessary due to the significant risk of cardiovascular disease it represents.

Nailfold capillaroscopic changes of sleep apnea patients

BACKGROUND

Obstructive Sleep Apnea Syndrome (OSAS) have frequent association with comorbidities and this makes it an independent risk factor for cardiovascular disease. Not only endothelial dysfunction, but also arterial stiffening, increased inflammatory mediators, oxidative stress after hypoxemia that develops due to OSAS, cause vascular pathologies in all diameters of vessels. Nail bed capillaroscopy is a simple, noninvasive, useful method to examine microcirculation and evaluate nail bed capillary abnormalities in diseases that cause vascular damage. The aim of this study is to examine microvascular changes in the nail bed of OSAS patients by capillaroscopy.

METHODS

59 OSAS patients and 60 healthy cases (totally 119) were included. One single attended polysomnography was applied with Embla N7000 series (RemLogic Eastmed, Natus); and apnea-hypopnea index (AHI), oxygen de-saturation index >4% (ODI4%), minimum oxygen saturation (SaO2 Min.), total duration of oxygen desaturation, comorbidities, body mass index (BMI), smoking habit, sleep questionnaire applications were analyzed. Nailfold capillaroscopy was performed using a digital dermoscope (Molemax II, X30) and all images were evaluated for capillary density, capillary loop enlargement, capillary tortuosity, branching vessels, micro hemorrhages, avascular areas and splinter hemorrhages.

RESULTS

The prevalence rates of all capillaroscopy findings were significantly higher in the patient group (p < 0.05). There was an inverse and moderate relationship between AHI and mean saturation (p < 0.05). A statistically significant correlation was detected between the presence of hypertension (HT) and the severity of capillary tortuosity (CT) (p = 0.002), avascular area (AA) (p = 0.004), and periungual cyanosis (PUC) (p = 0.042); also between smoking habit and intensity of capillary dilatation, enlargement dilatation-enlarged giant capillaries (CELON) (p = 0.004), CT (p = 0.018) findings. Capillary distribution (CD), CELON, CT and AA findings were significantly higher in the group with low mean saturation (p < 0.05). DM was found to be significantly higher in individuals with high Epworth Sleep Scale (ESS) (p = 0.035).

CONCLUSION

In this study; 1) the nail bed capillaroscopy was used to examine vascular damage in OSAS, and 2) irregularities detected in the distal nail bed specific to a disease have been mentioned for the first time. It has been shown that endothelial damage is particularly related to the severity of hypoxia. HT and smoking history causes endothelial damage independent of the severity of the disease and hypoxia. Also, ESS may be more determinant in the screening of sleep disorders in diabetic patients.

The Assessment of Endothelial Dysfunction among OSA Patients after CPAP Treatment

Background and Objectives: Microcirculation dysfunction is present in patients with obstructive sleep apnea (OSA). Intermittent hypoxia generates “oxidative stress”, which contributes to chronic inflammation. The secretion of nitric oxide (NO), which is responsible for adequate regulation of the endothelium, is impaired due to a decrease in endothelial nitric oxide synthetase (eNOS) expression and an increase in endogenous eNOS inhibitors. Furthermore, nocturnal awakenings lead to the dysregulation of cortisol release and increased stimulation of the sympathetic nervous system. The non-invasive method of choice in OSA treatment is continuous positive airway pressure (CPAP). Materials and Methods: PubMed, Scopus, and Google Scholar databases were searched, and only papers published in the last 15 years were subsequently analyzed. For this purpose, we searched for keywords in article titles or contents such as “obstructive sleep apnea”, “microcirculation”, and “CPAP”. In our review, we only studied English articles that reported systemic reviews and meta-analyses, clinical studies, and case reports. Results: Endothelial dysfunction can be assessed by methods based on reactive hyperemia, such as flow-mediated dilation (FMD) measured by ultrasonography, laser-Doppler flowmetry (LDF), or capillaroscopy. In invasive techniques, intravenous administration of vasodilator substances takes place. Some surveys detected impaired microcirculation in OSA patients compared with healthy individuals. The level of dysfunction depended on the severity of OSA. CPAP treatment significantly improved endothelial function and microvascular blood flow and lowered the inflammatory mediator level. Conclusions: The first-choice treatment—CPAP—reduces the number of apneas and hypopneas during the night, induces the reversal of hypopnea and the chronic inflammatory state, and enhances activation of the sympathetic nervous system. Changes are visible as improved blood flow in both macro- and microcirculation, increased arterial elasticity, and decreased stiffness. Thus, early implementation of adequate treatment could be essential to reduce high cardiovascular risk in patients with OSA.

Obstructive apnea causes microvascular perfusion maldistribution in the lungs of rats

Obstructive sleep apnea (OSA) is associated with significant cardiovascular consequences, including pulmonary hypertension, yet little is known about its effects on pulmonary microvascular perfusion. To investigate effects of OSA on pulmonary microvascular perfusion, we clamped the tracheal cannulas of anesthetized, spontaneously breathing rats to simulate obstructive apnea. The clamp remained in place for 10 breaths before it was released to allow the animals to again breathe spontaneously. We repeated this protocol every 20 s until the rat experienced a total of five apneic episodes of 10 breaths each. We then infused into a femoral vein 10⁸ fluorescent latex particles (4 µm diameter), which became trapped within the pulmonary microcirculation. We removed the lungs, allowed them to air-dry, and quantified the particle distributions in sections of the lungs using dispersion index (DI) analysis, a method we developed previously. The log of the DI (logDI) is a measure of perfusion maldistribution. Greater log(DI) values correspond to greater maldistribution. Apneic lungs had average logDI values of 1.28 (SD 0.24). Rats not subjected to apnea had average logDI values of 0.85 (SD 0.08) ( P ≤ 0.05). Rats that received latex particles 10 min or 24 h after apnea had average logDI values of 0.97 (SD 0.31) and 0.84  (SD 0.38), respectively (not significant). Our results demonstrate, for the first time, that a few apneic events produced significant, but temporary, perfusion maldistribution within the pulmonary microcirculation. Repeated nightly episodes of apnea over months and years may explain why human patients with OSA suffer from significantly greater cardiovascular disease than those without OSA.