Nocturnal hypoxia and arterial lactate levels in sleep-related breathing disorders

Arterial bicarbonate is associated with hypoxic burden and uncontrolled hypertension in obstructive sleep apnea - The ESADA cohort

OBJECTIVE

Blood bicarbonate concentration plays an important role for obstructive sleep apnea (OSA) patients to maintain acid-base balance. We investigated the association between arterial standard bicarbonate ([HCO3^-]) and nocturnal hypoxia as well as comorbid hypertension in OSA.

METHODS

A cross-sectional analysis of 3329 patients in the European Sleep Apnea Database (ESADA) was performed. Arterial blood gas analysis and lung function test were performed in conjunction with polysomnographic sleep studies. The 4% oxygen desaturation index (ODI), mean and minimum oxygen saturation (SpO₂), and percentage of time with SpO₂ below 90% (T90%) were used to reflect nocturnal hypoxic burden. Arterial hypertension was defined as a physician diagnosis of hypertension with ongoing antihypertensive medication. Hypertensive patients with SBP/DBP below or above 140/90 mmHg were classified as controlled-, uncontrolled hypertension, respectively.

RESULTS

The [HCO3^-] level was normal in most patients (average 24.0 ± 2.5 mmol/L). ODI, T90% increased whereas mean and minimum SpO₂ decreased across [HCO3^-] tertiles (ANOVA, p = 0.030, <0.001, <0.001, and <0.001, respectively). [HCO3^-] was independently associated with ODI, mean SpO₂, minimum SpO₂, and T90% after adjusting for confounders (β value [95%CI]: 1.21 [0.88-1.54], -0.16 [-0.20 to -0.11], -0.51 [-0.64 to -0.37], 1.76 [1.48-2.04], respectively, all p < 0.001). 1 mmol/L elevation of [HCO3^-] was associated with a 4% increased odds of uncontrolled hypertension (OR: 1.04 [1.01-1.08], p = 0.013).

CONCLUSION

We first demonstrated an independent association between [HCO3^-] and nocturnal hypoxic burden as well as uncontrolled hypertension in OSA patients. Bicarbonate levels as an adjunctive measure provide insight into the pathophysiology of hypertension in OSA.

Serum uric acid and arterial lactate levels in patients with obstructive sleep apnea syndrome: the effect of CPAP treatment

Objectives: Serum uric acid (UA) and arterial lactate acid (LA) are markers of oxidative stress and tissue hypoxia that are present in patients with obstructive sleep apnea syndrome (OSAS). The aim of the study was to evaluate the associations between UA and LA levels and OSAS characteristics as well as the effect of their levels after continuous positive airway pressure (CPAP) treatment.Methods: This is a retrospective of newly diagnosed patients with OSAS. UA and LA levels were measured the night before the diagnostic sleep study, and 6 months after CPAP therapy.Results: We evaluated 604 individuals with OSAS and 98 controls (i.e. individuals without sleep-related breathing disorders). Baseline median (IQR) serum UA levels were higher in OSAS patients compared to controls; 7.0 (6.4, 8.1) mg/dL vs 6.3 (6.1, 6.4) mg/dL, respectively (p < 0.001). This difference remained significant, after adjustment of serum UA to creatinine ratio (UA/Cr) (p < 0.001). Patients with OSAS had higher LA levels at baseline compared to controls; 2.26 (2.25, 2.31) mmol/L vs 1.90 (1.87, 1.97) mmol/L, respectively (p < 0.001). Both UA and LA levels decreased significantly after CPAP treatment [median (IQR): 7.0 (6.4, 8.1) mg/dL vs 6.4 (6.2, 6.8) mg/dL, p < 0.001 and 2.26 (2.25, 2.31) mmol/L vs 2.08 (2.07, 2.31) mmol/L, p < 0.001]. Several sleep parameters were independent predictors of UA and LA levels.Conclusion: In OSAS patients increased serum UA and arterial LA levels are found. CPAP therapy resulted in significant reductions in levels of both biomarkers.

Proteomic Study Identifies Glycolytic and Inflammation Pathways Involved in Recurrent Otitis Media

Recurrent acute otitis media (RAOM) in children is clinically defined as the occurrence of at least three episodes of acute otitis media over a course of 6 months. A further common pathological condition of interest in the context of pediatric otolaryngology is adenotonsillar hypertrophy (ATH), a common cause of obstructive sleep apnea syndrome. Aimed at unraveling the differential modulation of proteins in the two pathologies and at understanding the possible pathways involved in their onset, we analyzed the proteomic profile of the adenoids from 14 RAOM and ATH patients by using two-dimensional gel electrophoresis (2-DE) and mass spectrometry (MS). The 2-DE coupled with MS allowed us to identify 23 spots with significant (p-value < 0.05) changes in protein amount, recognizing proteins involved in neutrophil degranulation and glycolysis pathways.

The effect of CPAP treatment on venous lactate and arterial blood gas among obstructive sleep apnea syndrome patients

PURPOSE

The aim of this observational study was to investigate the influence of continuous positive airway pressure (CPAP) on arterial blood gas and venous lactate, markers of tissue hypoxia, among obstructive sleep apnea syndrome (OSAS) patients, and determine the risk factor of serum lactate and hydrogen ion concentration (PH) in OSAS patients.

MATERIALS AND METHODS

One-hundred and nine patients with newly diagnosed OSAS were enrolled in the study. All individuals were treated with CPAP for one night. Venous lactate and arterial blood gas were gathered from all subjects in the morning at the end of polysomnography and the next morning after CPAP treatment.

RESULTS

Of the 109 selected subjects, the average lactate level was 2.23 ± 0.59 mmol/L, and the mean PH, PaO₂, and PaCO₂ were 7.380 ± 0.23, 88.14 ± 17.83 mmHg, and 38.70 ± 4.28 mmHg, respectively. Compared to baseline, lactic acid significantly decreased (2.10 ± 0.50 mmol/L, p = 0.03), while PH increased (7.388 ± 0.27, p < 0.05) after CPAP treatment. In addition, neck circumference and the polysomnographic parameters, including apnea-hypopnea index, oxygen desaturation index (ODI), mean oxygen saturation (SpO₂), and the percentage of sleep time with SpO₂ <90 % (TS90 %), positively correlated with lactate, while age correlated negatively with lactate (all p < 0.05). Significantly positive associations were found between age, neck circumference, and PH; furthermore, a negative correlation was found between ODI and PH. Finally, after adjusting for confounding factors, TS90 % was the major contributing predictor for elevated lactate (p < 0.05), and age was a predictor for an increase in PH (p < 0.05).

CONCLUSIONS

The results indicated that CPAP treatment could reduce serum lactate and increase PH in OSAS patients and might alleviate acid-base balance disorders in OSAS. Furthermore, TS90 % was a risk factor for elevated lactate, and age was independently associated with PH.

Diagnostic capability of biological markers in assessment of obstructive sleep apnea: a systematic review and meta-analysis

OBJECTIVE

The purpose of this systematic review is to evaluate the diagnostic value of biological markers (exhaled breath condensate, blood, salivary and urinary) in the diagnosis of OSA in comparison to the gold standard of nocturnal PSG.

METHODS

Studies that differentiated OSA from controls based on PSG results, without age restriction, were eligible for inclusion. The sample of selected studies could include studies in obese patients and with known cardiac disease. A detailed individual search strategy for each of the following bibliographic databases was developed: Cochrane, EMBASE, MEDLINE, PubMed, and LILACS. The references cited in these articles were also crosschecked and a partial grey literature search was undertaken using Google Scholar. The methodology of selected studies was evaluated using the 14-item Quality Assessment Tool for Diagnostic Accuracy Studies.

RESULTS

After a two-step selection process, nine articles were identified and subjected to qualitative and quantitative analyses. Among them, only one study conducted in children and one in adults found biomarkers that exhibit sufficiently satisfactory diagnostic accuracy that enables application as a diagnostic method for OSA.

CONCLUSION

Kallikrein-1, uromodulin, urocotin-3, and orosomucoid-1 when combined have enough accuracy to be an OSA diagnostic test in children. IL-6 and IL-10 plasma levels have potential to be good biomarkers in identifying or excluding the presence of OSA in adults.

Biomarkers associated with obstructive sleep apnea: A scoping review

The overall validity of biomarkers in the diagnosis of obstructive sleep apnea (OSA) remains unclear. We conducted a scoping review to provide assessments of biomarkers characteristics in the context of obstructive sleep apnea (OSA) and to identify gaps in the literature. A scoping review of studies in humans without age restriction that evaluated the potential diagnostic value of biological markers (blood, exhaled breath condensate, salivary, and urinary) in the OSA diagnosis was undertaken. Retained articles were those focused on the identification of biomarkers in subjects with OSA, the latter being confirmed with a full overnight or home-based polysomnography (PSG). Search strategies for six different databases were developed. The methodology of selected studies was classified using an adaptation of the evidence quality criteria from the American Academy of Pediatrics. Additionally the biomarkers were classified according to their potential clinical application. We identified 572 relevant studies, of which 117 met the inclusion criteria. Eighty-two studies were conducted in adults, 34 studies involved children, and one study had a sample composed of both adults and children. Most of the studies evaluated blood biomarkers. Potential diagnostic biomarkers were found in nine pediatric studies and in 58 adults studies. Only nine studies reported sensitivity and specificity, which varied substantially from 43% to 100%, and from 45% to 100%, respectively. Studies in adults have focused on the investigation of IL-6, TNF-α and hsCRP. There was no specific biomarker that was tested by a majority of authors in pediatric studies, and combinatorial urine biomarker approaches have shown preliminary promising results. In adults IL-6 and IL-10 seem to have a favorable potential to become a good biomarker to identify OSA.

Metabolic dysfunction in obstructive sleep apnea: A critical examination of underlying mechanisms

It has recently become clear that obstructive sleep apnea (OSA) is an independent risk factor for the development of metabolic syndrome, a disorder of defective energy storage and use. Several mechanisms have been proposed to explain this finding, drawing upon the characteristics that define OSA. In particular, intermittent hypoxia, sleep fragmentation, elevated sympathetic tone, and oxidative stress - all consequences of OSA - have been implicated in the progression of poor metabolic outcomes in OSA. In this review we examine the evidence to support each of these disease manifestations of OSA as a unique risk for metabolic dysfunction. Tissue hypoxia and sleep fragmentation are each directly connected to insulin resistance and hypertension, and each of these also may increase sympathetic tone, resulting in defective glucose homeostasis, excessive lipolysis, and elevated blood pressure. Oxidative stress further worsens insulin resistance and in turn, metabolic dysfunction also increases oxidative stress. However, despite many studies linking each of these individual components of OSA to the development of metabolic syndrome, there are very few reports that actually provide a coherent narrative about the mechanism underlying metabolic dysfunction in OSA.

Serum uric acid and lactate levels among patients with obstructive sleep apnea syndrome: which is a better marker of hypoxemia?

BACKGROUND AND OBJECTIVES

Tissue hypoxia due to repeated sleep apneas leads to increased serum levels of uric acid (UA) and lactate in patients with obstructive sleep apnea syndrome (OSAS). Studies on assessment of serum level of UA in patients of OSAS are available. However, research on simultaneous evaluation of levels of serum lactate and UA is lacking.

DESIGN AND SETTING

Prospective, case-control study in a tertiary care institution.

PATIENTS AND METHODS

Forty patients suffering from OSAS, diagnosed by night polysomnography (PSG), were included in this study. Forty age- and sex-matched subjects in whom the presence of OSAS was ruled out by night PSG were included as healthy controls. Participants underwent a procedure for the measurement of serum UA and lactate before and after sleep.

RESULTS

Both before and after sleep UA levels of patients with OSAS were found to be significantly higher (P=.001 and .002, respectively) as compared to UA levels of controls. A statistically significant (P=.02) overnight (after sleep) rise was observed in the serum lactate level of OSAS patients. The correlation between serum UA values and %TSTs (percentage of total sleep time spent) below 95% SaO2 (arterial oxygen saturation) was statistically significant (P=.02). The correlation was positive with %TSTs below 90% SaO2, whereas it was found negative with normal basal oxygen. No significant correlation was observed between serum UA and the AHI (apnea-hypopnea index). Polysomnographic variables failed to show significant correlation with serum UA on respective multiple regression models controlling for age, body mass index, and waist-hip ratio. However, plasma lactate levels after sleep correlated with %TSTs below 95% of SaO2 and AHI with P values of .02 and .01, respectively.

CONCLUSIONS

Both serum UA and lactate were positively correlated with the degree of hypoxia in OSAS. The plasma UA levels in patients with OSAS did not show an overnight rise. However, the plasma lactate levels were higher in the morning. The measurement of serum lactate level was a better marker of oxidative stress among patients with OSAS.