Effect of Continuous Positive Airway Pressure on Blood Pressure Variability in Patients With Obstructive Sleep Apnea

Sleep Apnea, Autonomic Disturbances, and Blood Pressure Variability

Augmented blood pressure variability has emerged as a quantity predictive of adverse cardiovascular outcomes. Among the range of intrinsic and extrinsic factors shown to increase night-time, circadian, short-term, and long-term blood pressure variations, the presence and severity of obstructive sleep apnea have emerged as one of the most prevalent and potent. Obstructive sleep apnea alters acutely the normal nocturnal equilibrium between sympathetic and parasympathetic tone, magnifying nocturnal blood pressure oscillations, and induces sustained autonomic aftereffects with the capacity to amplify short-term and intersessional blood pressure variabilities. The object of this brief review is to synthesize the current understanding of the potential interrelations between obstructive sleep apnea, the acute and sustained autonomic disturbances that it elicits, and beat-to-beat blood pressure fluctuation during sleep, nocturnal dipping status, and day-to-day blood pressure variability and the consequences of these perturbations for cardiovascular risk.

Relationship between 24 h blood pressure variability and mortality in acute myocardial infarction patients

BACKGROUND

In recent years, the mortality of patients with AMI has not declined significantly. The relationship between blood pressure variability (BPV) and acute myocardial infarction (AMI) is unclear. We explored the relationship between 24-h BPV and mortality in patients with AMI.

HYPOTHESIS

The mortality of patients with AMI is related to BPV. We hope to provide therapeutic ideas for reducing the risk of death in patients with AMI.

METHODS

This is a retrospective cohort study. We extracted and analyzed data from the MIMIC-IV 2.0, which was established in 1999 under the auspices of the National Institutes of Health (America). The average real variability (ARV) was calculated for the first 24-h blood pressure measurement after patients with AMI were admitted to the intensive care unit (ICU). Patients were divided into four groups according to ARV quartiles. The outcomes were 30-day, 1-year, and 3-year all-cause mortalities. Data were analyzed using Cox regression, Kaplan-Meier curves, and restricted cubic spline (RCS) curves.

RESULTS

We enrolled 1291 patients with AMI, including 475 female. The patients were divided into four groups according to the qualities of diastolic blood pressure (DBP)-ARV. There were significant differences in the 30-day, 1-year and 3-year mortality among the four groups (p = .02, p < .001, p < .001, respectively). After adjustment for confounding factors, systolic blood pressure (SBP)-ARV could not predict AMI patient mortality (p > .05), while the highest DBP-ARV was associated strongly with increased 30-day mortality (HR: 2.291, 95% CI 1.260-4.168), 1-year mortality (HR: 1.933, 95% CI 1.316-2.840) and 3-year mortality (HR: 1.743, 95% CI 1.235-2.461). Kaplan-Meier curves demonstrated that, regardless of SBP or DBP, the long-term survival probabilities of patients in the highest ARV group were significantly lower than that of those in other groups. RCS curves showed that the death risk of patients with AMI first decreased and then increased with the increase in ARV when DBP-ARV < 8.04. The 30-day death risk first increased and then decreased, and the 1-year and 3-year death risks increased and then stabilized with ARV increase when DBP-ARV > 8.04.

CONCLUSION

This study showed that patients with AMI may have an increased risk of short- and long-term death if their DBP-ARV is higher or lower during the first 24-h in ICU.

Blood pressure variability: methodological aspects, clinical relevance and practical indications for management - a European Society of Hypertension position paper ∗

Blood pressure is not a static parameter, but rather undergoes continuous fluctuations over time, as a result of the interaction between environmental and behavioural factors on one side and intrinsic cardiovascular regulatory mechanisms on the other side. Increased blood pressure variability (BPV) may indicate an impaired cardiovascular regulation and may represent a cardiovascular risk factor itself, having been associated with increased all-cause and cardiovascular mortality, stroke, coronary artery disease, heart failure, end-stage renal disease, and dementia incidence. Nonetheless, BPV was considered only a research issue in previous hypertension management guidelines, because the available evidence on its clinical relevance presents several gaps and is based on heterogeneous studies with limited standardization of methods for BPV assessment. The aim of this position paper, with contributions from members of the European Society of Hypertension Working Group on Blood Pressure Monitoring and Cardiovascular Variability and from a number of international experts, is to summarize the available evidence in the field of BPV assessment methodology and clinical applications and to provide practical indications on how to measure and interpret BPV in research and clinical settings based on currently available data. Pending issues and clinical and methodological recommendations supported by available evidence are also reported. The information provided by this paper should contribute to a better standardization of future studies on BPV, but should also provide clinicians with some indications on how BPV can be managed based on currently available data.

High night-to-night variability in sleep apnea severity is associated with uncontrolled hypertension

Obstructive sleep apnea (OSA) severity can vary markedly from night-to-night. However, the impact of night-to-night variability in OSA severity on key cardiovascular outcomes such as hypertension is unknown. Thus, the primary aim of this study is to determine the effects of night-to-night variability in OSA severity on hypertension likelihood. This study uses in-home monitoring of 15,526 adults with ~180 nights per participant with an under-mattress sleep sensor device, plus ~30 repeat blood pressure measures. OSA severity is defined from the mean estimated apnea-hypopnoea index (AHI) over the ~6-month recording period for each participant. Night-to-night variability in severity is determined from the standard deviation of the estimated AHI across recording nights. Uncontrolled hypertension is defined as mean systolic blood pressure ≥140 mmHg and/or mean diastolic blood pressure ≥90 mmHg. Regression analyses are performed adjusted for age, sex, and body mass index. A total of 12,287 participants (12% female) are included in the analyses. Participants in the highest night-to-night variability quartile within each OSA severity category, have a 50-70% increase in uncontrolled hypertension likelihood versus the lowest variability quartile, independent of OSA severity. This study demonstrates that high night-to-night variability in OSA severity is a predictor of uncontrolled hypertension, independent of OSA severity. These findings have important implications for the identification of which OSA patients are most at risk of cardiovascular harm.

Ambulatory Blood Pressure Variability after Adenotonsillectomy in Childhood Sleep Apnea

OBJECTIVE

To investigate the influence of adenotonsillectomy (T&A) on ambulatory blood pressure (BP) variability in children with obstructive sleep apnea (OSA).

STUDY DESIGN

Prospective, interventional study.

METHODS

Children with OSA symptoms were recruited from a tertiary center. After OSA diagnosis was confirmed (ie, apnea-hypopnea index [AHI] > 1), these children underwent T&A for treatment. We performed polysomnography and 24-hour recordings of ambulatory BP before and 3 to 6 months postoperatively. Ambulatory BP variability was presented as the standard deviation of mean blood pressure in the 24-hour monitoring of ambulatory BP. Differences in BP variability among different subgroups were tested using a multivariable linear mixed model.

RESULTS

A total of 190 children were enrolled (mean age: 7.8 ± 3.3 years; 73% were boys; 34% were obese). The AHI significantly decreased from 12.3 ± 17.0 to 2.7 ± 5.5 events/hr after T&A. Overall, daytime, and nighttime ambulatory BP did not significantly change postoperatively, and overall, daytime, and nighttime ambulatory BP variability did not differ significantly preoperatively and postoperatively. In the subgroup analysis, children aged <6 years demonstrated a significantly greater decrease in ambulatory BP variability postoperatively than those aged >6 years (nighttime diastolic BP variability: 9.9 to 7.7 vs. 8.9 to 9.4). Children with hypertension also showed a significantly greater decrease in ambulatory BP variability than those without hypertension.

CONCLUSIONS

We concluded that overall ambulatory BP variability does not significantly change after T&A in children with OSA. Moreover, young-aged and hypertensive children demonstrate a significant decrease in BP variability after T&A.

LEVEL OF EVIDENCE

4 Laryngoscope, 132:2491-2497, 2022.

Evaluation and Management of Secondary Hypertension

Hypertension is a major cause of cardiovascular morbidity and mortality globally. Many patients with hypertension have secondary causes of hypertension that merit further evaluation. For example, secondary hypertension can result in target organ damage to the heart, kidneys, and brain independent of the effects of blood pressure. Several causes benefit from targeted therapies to supplement first-line antihypertensive agents. However, secondary hypertension is often underrecognized. The goal of this review is to highlight optimal approaches to the diagnosis and management of common causes of secondary hypertension, including primary aldosteronism, renovascular hypertension, obstructive sleep apnea, and drug-induced hypertension.

Immunoregulatory Effect of Short-Chain Fatty Acids from Gut Microbiota on Obstructive Sleep Apnea-Associated Hypertension

The intestine is the largest bacterial ecosystem and immune response organ of the human body. The microbiota regulates the metabolic and immune functions of the host through their metabolites. Short-chain fatty acids (SCFAs) are part of the metabolites of the gut microbiota (GM), providing energy to intestinal epithelial cells and regulating the immune system. A decrease in SCFA-producing bacteria, imbalanced effector T-helper cells (Th cells), and increasing corresponding inflammatory cytokine were found in both animal models and clinical patients with obstructive sleep apnea (OSA) and hypertension (HTN). Intervention with probiotics, prebiotics, or postbiotics in animal models simulating OSA-associated HTN restored blood pressure to normal, which allows the hypothesis that GM are involved in the pathophysiology of OSA-induced HTN patients through their metabolites' SCFAs; however, the exact regulatory mechanism is not completely clear. This review describes the potential mechanisms of SCFAs, a major metabolite of the GM, in the pathology of OSA-induced HTN, from the perspective of immune system regulation in the available studies.

New and Emerging Approaches to Better Define Sleep Disruption and Its Consequences

Current approaches to quantify and diagnose sleep disorders and circadian rhythm disruption are imprecise, laborious, and often do not relate well to key clinical and health outcomes. Newer emerging approaches that aim to overcome the practical and technical constraints of current sleep metrics have considerable potential to better explain sleep disorder pathophysiology and thus to more precisely align diagnostic, treatment and management approaches to underlying pathology. These include more fine-grained and continuous EEG signal feature detection and novel oxygenation metrics to better encapsulate hypoxia duration, frequency, and magnitude readily possible via more advanced data acquisition and scoring algorithm approaches. Recent technological advances may also soon facilitate simple assessment of circadian rhythm physiology at home to enable sleep disorder diagnostics even for “non-circadian rhythm” sleep disorders, such as chronic insomnia and sleep apnea, which in many cases also include a circadian disruption component. Bringing these novel approaches into the clinic and the home settings should be a priority for the field. Modern sleep tracking technology can also further facilitate the transition of sleep diagnostics from the laboratory to the home, where environmental factors such as noise and light could usefully inform clinical decision-making. The “endpoint” of these new and emerging assessments will be better targeted therapies that directly address underlying sleep disorder pathophysiology via an individualized, precision medicine approach. This review outlines the current state-of-the-art in sleep and circadian monitoring and diagnostics and covers several new and emerging approaches to better define sleep disruption and its consequences.

Long-Term Habitual Vigorous Physical Activity Is Associated With Lower Visit-to-Visit Systolic Blood Pressure Variability: Insights From the SPRINT Trial

BACKGROUND

Our work aimed to investigate the association between vigorous physical activity and visit-to-visit systolic blood pressure variability (BPV).

METHODS

We conducted a post hoc analysis of SPRINT (Systolic Blood Pressure Intervention Trial), a well-characterized cohort of participants randomized to intensive (<120 mm Hg) or standard (<140 mm Hg) systolic blood pressure targets. We assessed whether patients with hypertension who habitually engage in vigorous physical activity would have lower visit-to-visit systolic BPV compared with those who do not engage in vigorous physical activity. Visit-to-visit systolic BPV was calculated by SD, average real variability (ARV), and SD independent of the mean (SDIM) using measurements taken during the 1-, 2-, 3-, 6-, 9-, and 12-month study visits. A medical history questionnaire assessed vigorous physical activity, which was divided into 3 categories according to the frequency of vigorous physical activity.

RESULTS

A total of 7,571 participants were eligible for analysis (34.8% female, mean age 67.9 ± 9.3 years). During a follow-up of 1-year, vigorous physical activity could significantly reduce SD, ARV, and SDIM across increasing frequency of vigorous physical activity. There were negative linear trends between frequency of vigorous physical activity and visit-to-visit systolic BPV.

CONCLUSIONS

Long-term engagement in vigorous physical activity was associated with lower visit-to-visit systolic BPV.

CLINICAL TRIALS REGISTRATION

SPRINT (Systolic Blood Pressure Intervention Trial); Trial Number: NCT01206062, https://clinicaltrials.gov/ct2/show/NCT01206062.

24-Hour Ambulatory Blood Pressure Variability in Children with Obstructive Sleep Apnea

OBJECTIVE

To evaluate blood pressure (BP) variability in 24-hour ambulatory BP monitoring in children with obstructive sleep apnea (OSA).

STUDY DESIGN

Case series study.

METHODS

Children aged 4 to 16 years with clinical symptoms were recruited in a tertiary medical center. Overnight polysomnography and 24-hour recordings of ambulatory BP were performed for each child. The severity of OSA was classified as primary snoring (apnea-hypopnea index [AHI] < 1), mild OSA (1 ≤ AHI < 5), moderate OSA (10 > AHI ≥ 5), and severe OSA (AHI ≥ 10). The standard deviation of mean BP was used as an indicator of BP variability.

RESULTS

A total of 550 children were included (mean age: 7.6 years; 70% were boys; 20% were obese). Compared with the children with primary snoring, children with severe OSA exhibited significantly higher nighttime systolic BP (108.0 vs. 100.5 mmHg, P < .001), nighttime diastolic BP (58.9 vs 55.6 mmHg, P = .002), nighttime mean arterial pressure (75.3 vs. 70.5 mmHg, P < .001), nighttime systolic BP load (40.5% vs. 25.0%, P < .001), nighttime diastolic BP load (25.3% vs. 12.9%, P < .001), and nighttime systolic BP variability (11.4 vs. 9.6, P = .001). Multiple linear regression analyses revealed an independent association between AHI and nighttime systolic BP variability (regression coefficient = 0.31, 95% CI = 0.06-0.56, P = .015) after adjustment for age, gender, adiposity, and hypertensive status.

CONCLUSIONS

OSA in children is associated with increased BP and BP variability.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:2126-2132, 2021.

Comparative effects of CPAP and mandibular advancement splint therapy on blood pressure variability in moderate to severe obstructive sleep apnoea

BACKGROUND

Obstructive sleep apnoea (OSA) is associated with increased blood pressure variability (BPV) and are risk factors for cardiovascular disease. We aimed to assess the comparative effects of two OSA therapies, continuous positive airway pressure (CPAP) and mandibular advancement splint (MAS), on BPV.

METHODS

This is a secondary analysis of data collected as part of a previously published randomised crossover trial of one month each of CPAP and MAS therapy. BPV was determined from 24-h-ambulatory blood pressure recordings in 92 patients with moderate to severe OSA at baseline and after one month of optimised treatment with each modality. BPV was assessed by three measures: Standard deviation of the mean (SD), Coefficient of variation (CoV), and the Average Real Variability (ARV) index.

RESULTS

Neither CPAP nor MAS therapy improved BPV, with no difference between treatments. BPV did not change in hypertensive OSA patients, however, there was a reduction in ARV of diastolic blood pressure in the effectively treated compared to ineffectively treated CPAP patients, Δ ARV 24-h-DBP (mmHg), -0.72 ± 2.14, 0.34 ± 1.52, P = 0.02, respectively. There was no difference between effective versus ineffective MAS treatment, Δ ARV 24-h-DBP (mmHg), -0.04 ± 2.4, 0.02 ± 1.9, P = 1.00, respectively.

CONCLUSIONS

One month of optimised CPAP or MAS therapy did not improve short term BPV in patients with moderate to severe OSA. The subgroup of patients on effective CPAP showed some improvement in BPV with CPAP but not MAS. Further work on the effect of OSA therapy on BPV following long-term therapy is needed.

A New Feature with the Potential to Detect the Severity of Obstructive Sleep Apnoea via Snoring Sound Analysis

The severity of obstructive sleep apnoea (OSA) is diagnosed with polysomnography (PSG), during which patients are monitored by over 20 physiological sensors overnight. These sensors often bother patients and may affect patients’ sleep and OSA. This study aimed to investigate a method for analyzing patient snore sounds to detect the severity of OSA. Using a microphone placed at the patient’s bedside, the snoring and breathing sounds of 22 participants were recorded while they simultaneously underwent PSG. We examined some features from the snoring and breathing sounds and examined the correlation between these features and the snore-specific apnoea-hypopnea index (ssAHI), defined as the number of apnoea and hypopnea events during the hour before a snore episode. Statistical analyses revealed that the ssAHI was positively correlated with the Mel frequency cepstral coefficients (MFCC) and volume information (VI). Based on clustering results, mild snore sound episodes and snore sound episodes from mild OSA patients were mainly classified into cluster 1. The results of clustering severe snore sound episodes and snore sound episodes from severe OSA patients were mainly classified into cluster 2. The features of snoring sounds that we identified have the potential to detect the severity of OSA.

Obstructive Sleep Apnea, Hypertension, and Cardiovascular Risk: Epidemiology, Pathophysiology, and Management

PURPOSE OF REVIEW

Given the rising prevalence of obstructive sleep apnea (OSA), we aimed to review the epidemiologic and pathophysiologic relationship of OSA, hypertension, and cardiovascular disease, and to summarize recent advances in the treatment of OSA.

RECENT FINDINGS

OSA is associated with an elevated risk of hypertension and cardiovascular disease. Several pathophysiologic factors contribute to the relationship between OSA and vascular risk, including neurohormonal dysregulation, endothelial dysfunction, and inflammation. While CPAP reduces blood pressure, it has not been demonstrated to reduce cardiovascular risk. The combination of CPAP and weight loss has a synergistic effect on blood pressure and several metabolic parameters. Adherence to CPAP is poor across studies, potentially contributing to the attenuation of perceived cardiovascular benefit from CPAP therapy. A greater emphasis on adherence to CPAP and the combination of CPAP and weight loss are central to reducing cardiovascular risk among individuals with OSA.

Moderate to Severe Obstructive Sleep Apnea in Military Personnel Is Not Associated With Decreased Exercise Capacity

STUDY OBJECTIVES

Studies of older and less active patients with obstructive sleep apnea (OSA) have reported decreased exercise capacity as measured by peak oxygen uptake (VO₂ max) during cardiopulmonary exercise testing (CPET). We looked to determine whether VO₂ max was decreased in younger patients with OSA who regularly exercise as would be encountered in the military.

METHODS

We evaluated military personnel who had undergone pulmonary function testing (PFT), CPET, and polysomnography (PSG) as part of the larger STAMPEDE III study for comprehensive evaluation of exertional dyspnea. For analysis, patients were classified into two groups, the OSA group with an apnea-hypopnea index (AHI) ≥ 15 events/h and a control group with an AHI < 15 events/h.

RESULTS

Mean AHI was 32.7 in the OSA group (n = 40) versus 5.8 in the control group (n = 58) with no significant difference in age (40.7 years versus 39.4 years) or body mass index (30.4 kg/m² versus 29.9 kg/m²). PFT was normal in both groups including diffusing capacity (100.7% versus 96.5%) and FEV₁ (89.2% versus 86.2%). VO₂ max was not significantly different in the OSA group compared to the control group (101.3% versus 102.8%; P = .60) with both groups having normal exercise capacity. Exercise blood pressure response was normal and peak heart rate trended toward a blunted response in the OSA group (166.0 bpm versus 171.6 bpm, P = .09).

CONCLUSIONS

Younger military personnel with moderate to severe OSA do not have decreased exercise capacity. The effect of OSA on exercise tolerance may be influenced by additional factors and is likely too small to be noted in this population.

COMMENTARY

A commentary on this article appears in this issue on page 819.

Systemic hypertension in obstructive sleep apnea

There is consistent epidemiological evidence that sleep disordered breathing and systemic arterial hypertension are deeply associated, being linked through a bidirectional complex interaction among multiple mechanisms including autonomic nervous system alterations, inflammation, hormonal and hemodynamic components, sleep alterations. However there are several unanswered questions not only from a pathophysiological perspective, but also regarding the effects of obstructive sleep apnea (OSA) treatment on arterial blood pressure values. At present, while many studies have supported the possibility to obtain at least a small blood pressure reduction with OSA treatment, in particular in hypertensive patients, large trials have not clearly confirmed a significant anti-hypertensive effect, nor a beneficial effect of this intervention on cardiovascular endpoints including cardiovascular mortality. Aim of the present review article is to address the relationship between OSA and hypertension in the light of the latest evidence in the field. Moreover we will discuss research topics which need to be investigated in the future, in order to better clarify still pending issues with the aim of obtaining an early diagnosis, a more suitable phenotyping including comorbidities, and better strategies to improve patients' compliance and adherence to treatment.

A review of the associations between obstructive sleep apnea and hypertensive disorders of pregnancy and possible mechanisms of disease

Obesity is prevalent among pregnant women in the United States; 15-20% of obese pregnant women have obstructive sleep apnea. The prevalence of obstructive sleep apnea increases along with body mass index, age and in the presence of other co-morbidities. Untreated obstructive sleep apnea in women is associated with a range of cardiovascular, pulmonary and metabolic co-morbidities; recent studies suggest that women with obstructive sleep apnea in pregnancy may be at significantly greater risk of entering pregnancy with chronic hypertension and/or of developing hypertensive disorders of pregnancy: gestational hypertension; preeclampsia; or eclampsia. This has serious public health implications; hypertensive disorders of pregnancy are a major cause of maternal and neonatal morbidity and mortality and are associated with a greater lifetime risk for cardiovascular disease. The mechanisms that associated obstructive sleep apnea with hypertensive disorders of pregnancy have not been defined, but several pathways are scientifically plausible. In this review, we will present a comprehensive literature review of the following: the associations between obstructive sleep apnea and hypertensive disorders of pregnancy; the proposed mechanisms that may connect obstructive sleep apnea and hypertensive disorders of pregnancy; and the effectiveness of treatment at mitigating these adverse outcomes.

Obstructive sleep apnea increases systolic and diastolic blood pressure variability in hypertensive patients

OBJECTIVE

Obstructive sleep apnea (OSA) has been identified as the most common secondary contributing factor for the development and worsening of hypertension. However, the underlying relationships between blood pressure variability (BPV) and OSA are still not very clear. Therefore, we investigated the influences of OSA on BPV in hypertensive patients and explored the potential pathophysiologic mechanisms.

PARTICIPANTS AND METHODS

Ambulatory blood pressure (BP) monitoring was carried out and polysomnography was performed to detect sleep apnea. A total of 86 hypertensive individuals were divided into patients without OSA (n=43) and patients with severe OSA (n=43). Systolic and diastolic BPV were obtained by calculating the SD, coefficient of variation, and average real variability during day-time, night-time, and over 24 h. The relationship between OSA and BPV was assessed after adjustment for potential confounding variables (age, sex, BMI, neck circumference, heart rate, and snoring history).

RESULTS

Compared with participants without OSA, nocturnal systolic BPV and 24-h systolic BP average real variability from OSA participants were obviously increased (P<0.05), but there were no statistically significant differences in day-time and 24-h systolic BP SD and coefficient of variation (P>0.05). Compared with participants without OSA, 24-h diastolic BPV and day-time diastolic BP SD from OSA participants were markedly increased (P<0.05), but nocturnal indices showed no significant differences between the two groups.

CONCLUSION

OSA mainly increases night-time systolic and 24-h diastolic BPV in hypertensive patients. This may provide a plausible explanation for OSA remaining a major risk determinant for cardiovascular diseases.

The acute effect of continuous positive airway pressure titration on blood pressure in awake overweight/obese patients with obstructive sleep apnoea

OBJECTIVES

Continuous positive airway pressure (CPAP) improves upper airway obstruction in patients with obstructive sleep apnoea (OSA), who often are overweight-obese. Although it is thought that CPAP improves long-term blood pressure control (BP), the impact of acute and short-term CPAP use on the cardiovascular system in obese patients has not been described in detail.

METHODS

Obese patients (body mass index, BMI > 25 kg/m²) with OSA were studied awake, supine during incremental CPAP titration (4-20 cmH₂O, +2 cmH₂O/3 mins). BP was measured continuously with a beat-to-beat BP monitor (Ohmeda 2300, Finapres Medical Systems, Amsterdam/NL), BP variability (BPV) was calculated as the standard deviation of BP at each CPAP level, the 95% confidence interval (95%CI) was calculated and changes in BP and BPV were reported.

RESULTS

15 patients (12 male, 48 ± 10) years, BMI 38.9 ± 5.8 kg/m²) were studied; the baseline BP was 131.0 ± 10.2/85.1 ± 9.1 mmHg. BP and BPV increased linearly with CPAP titration (systolic BP r = 0.960, p < .001; diastolic BP r = 0.961, p < .001; systolic BPV r = 0.662, p = .026; diastolic BPV r = 0.886, p < .001). The systolic BP increased by +17% (+23.15 (7.9, 38.4) mmHg; p = .011) and the diastolic BP by +23% (+18.27 (2.33, 34.21) mmHg; p = .009), when titrating CPAP to 20 cmH₂O. Systolic BPV increased by +96% (+5.10 (0.67, 9.53) mmHg; p < .001) and was maximal at 14 cmH₂O, and diastolic BPV by +97% (+3.02 (0.26, 5.78) mmHg; p < .001) at 16 cmH₂O.

CONCLUSION

Short-term incremental CPAP leads to significant increases in BP and BPV in obese patients with OSA while awake. Careful titration of pressures is required to minimise the risk of nocturnal awakenings while improving BP control.

Blood-pressure variability in patients with obstructive sleep apnea: current perspectives

Obstructive sleep apnea (OSA) is often associated with hypertension and other cardiovascular diseases. Blood pressure (BP) variability is part of the assessment of cardiovascular risk. In OSA, BP variability has been studied mainly as very short-term (beat-by-beat) and short-term (24-hour BP profile) variability. BP measured on consecutive heartbeats has been demonstrated to be highly variable, due to repeated peaks during sleep, so that an accurate assessment of nocturnal BP levels in OSA may require peculiar methodologies. In 24-hour recordings, BP frequently features a "nondipping" profile, ie, <10% fall from day to night, which may increase cardiovascular risk and occurrence of major cardiovascular events in the nocturnal hours. Also, BP tends to show a large "morning BP surge", a still controversial negative prognostic sign. Increased very short-term BP variability, high morning BP, and nondipping BP profile appear related to the severity of OSA. Treatment of OSA slightly reduces mean 24-hour BP levels and nocturnal beat-by-beat BP variability by abolishing nocturnal BP peaks. In some patients OSA treatment turns a nondipping into a dipping BP profile. Treatment of arterial hypertension in OSA usually requires both antihypertensive pharmacological therapy and treatment of apnea. Addressing BP variability could help improve the management of OSA and reduce cardiovascular risk. Possibly, drug administration at an appropriate time would ensure a dipping-BP profile.

Cardiorespiratory interaction with continuous positive airway pressure

The treatment of choice for obstructive sleep apnoea (OSA) is continuous positive airway pressure therapy (CPAP). Since its introduction in clinical practice, CPAP has been used in various clinical conditions with variable and heterogeneous outcomes. In addition to the well-known effects on the upper airway CPAP impacts on intrathoracic pressures, haemodynamics and blood pressure (BP) control. However, short- and long-term effects of CPAP therapy depend on multiple variables which include symptoms, underlying condition, pressure used, treatment acceptance, compliance and usage. CPAP can alter long-term cardiovascular risk in patients with cardiorespiratory conditions. Furthermore, the effect of CPAP on the awake patient differs from the effect on the patients while asleep, and this might contribute to discomfort and removal of the use interface. The purpose of this review is to highlight the physiological impact of CPAP on the cardiorespiratory system, including short-term benefits and long-term outcomes.

Impact of in-hospital blood pressure variability on cardiovascular outcomes in patients with acute coronary syndrome

To evaluate the impact of blood pressure variability (BPV) on cardiovascular outcomes in patients with acute coronary syndrome, short-term BPV was estimated by using weighted standard deviation of 24-hour ambulatory blood pressure monitoring readings. The primary outcome was in-hospital major adverse cardiac events (MACE). Overall, 200 patients (mean age, 58.6 years; 27.5% women; 38% with diabetes mellitus; and 47% smokers) were divided into low and high BPV groups based on the median value (9.45). Patients in the high BPV group were more likely to have in-hospital MACE compared with patients with low BPV (47% vs 27%, P = .003). Multivariate binary logistic regression analysis of incidence of MACE showed that BPV (odds ratio, 2.4; confidence interval, 1.2-4.5 [P = .008]) and presence of type II diabetes mellitus (odds ratio, 2.6; confidence interval, 1.2-5.3 [P = .008]) were the only independent predictors of in-hospital MACE derived mainly by hypertensive emergencies. BPV could be an important risk factor for in-hospital MACE in patients with acute coronary syndrome.