Refractory hypertension and sleep apnoea: effect of CPAP on blood pressure and baroreflex.

This study was undertaken to determine whether abolition of obstructive sleep apnoea (OSA) by continuous positive airway pressure (CPAP) could reduce blood pressure (BP) in patients with refractory hypertension. In 11 refractory hypertensive patients with OSA, the acute effects of CPAP on nocturnal BP were studied during sleep and its longer term effects on 24-h ambulatory BP after 2 months. During a single night's application, CPAP abolished OSA and reduced systolic BP in stage 2 sleep from 138.3 +/- 6.8 to 126.0 +/- 6.3 mmHg. There was also a trend towards a reduction in average diastolic BP (from 77.7 +/- 4.5 to 72.9 +/- 4.5). CPAP usage for 2 months was accompanied by an 11.0 +/- 4.4 mmHg reduction in 24-h systolic BP. In addition, both the nocturnal and daytime components of systolic BP fell significantly by 14.4 +/- 4.4 and 9.3 +/- 3.9 mmHg, respectively. Diastolic BP was reduced significantly at night by 7.8 +/- 3.0 mmHg. In patients with refractory hypertension, acute abolition of obstructive sleep apnoea by continuous positive airway pressure reduces nocturnal blood pressure. These data also suggest that continuous positive airway pressure may reduce nocturnal and daytime systolic blood pressure chronically. Randomised trials are needed to confirm the latter results.     

Effect of continuous positive airway pressure on ambulatory blood pressure in patients with obstructive sleep apnoea

OBJECTIVES: Previous reports on the effects of continuous positive airway pressure (CPAP) therapy for obstructive sleep apnoea (OSA) on blood pressure has shown contradictory results. Accordingly, we have investigated the effects of CPAP on blood pressure and on the potential reversal of the diagnosis of hypertension in patients with OSA evaluated repeatedly by ambulatory blood pressure monitoring. METHODS: We studied 122 patients (104 men and 18 women), 55.1+/-10.5 years of age, with diagnosis of OSA corroborated by overnight polysomnography at the clinic. Among those patients, 83 were treated with CPAP after their first evaluation, while 39 remained without CPAP for the duration of the trial. Blood pressure was measured by ambulatory monitoring at 20-min intervals during the day and at 30-min intervals at night for 48 consecutive hours, at baseline and after 2 and 4 months of intervention. RESULTS: There was a small, but not statistically significant, reduction in ambulatory blood pressure in patients treated with CPAP (0.7 and 1.5 mmHg in 24-h mean of systolic and diastolic blood pressure after 2 months of therapy; 2.0 and 2.3 mmHg after 4 months; P>0.239). The blood pressure reduction was very similar in patients with OSA followed for 4 months without CPAP (1.9 and 2.2 mmHg in 24-h mean of systolic and diastolic blood pressure, respectively; P=0.543). We found a high (77%) prevalence of hypertension among the patients participating in this study, although only 37% were receiving antihypertensive medication at the time of recruitment. The prevalence of hypertension was slightly but not significantly reduced to just 74% after 4 months of treatment with CPAP. CONCLUSIONS: The small reduction in blood pressure for consecutive profiles of ambulatory monitoring can probably be explained by the documented 'ABPM pressor effect' on patients using the ambulatory device for the first time. The high prevalence of hypertension among patients with OSA is not significantly reduced by treatment with CPAP. These results suggest that patients with OSA should always be properly evaluated for diagnosis of hypertension, and provided, if needed, with antihypertensive treatment apart from the recommended CPAP.     

Blood pressure variability in obstructive sleep apnea: role of sympathetic nervous activity and effect of continuous positive airway pressure

BACKGROUND: Many studies support a link between obstructive sleep apnea (OSA), increased blood pressure (BP) and/or BP variability, and sympathetic nervous system (SNS) activity. We assessed the relationship between SNS activity and 24-h BP variability in patients with OSA, and the effect of continuous positive airway pressure (CPAP) on BP variability. DESIGN: Forty-one patients with a respiratory disturbance index (RDI) > 15 were randomized into CPAP or CPAP placebo groups for a 1-week trial. METHODS: Ambulatory BP, 24-h urine norepinephrine (NE) and polysomnography were measured prior to treatment and after 1 and 7 days of treatment. RESULTS: Neither RDI nor 24-h urine NE levels were related to 24-h mean BP levels. While RDI was associated only with night-time BP variability, daytime urine NE levels were associated with both night-time and daytime BP variability. After treatment, the BP variability decreased significantly but equally in both active and placebo CPAP groups. CONCLUSIONS: Obstructive sleep apnea is more related to BP variability than BP. Sympathetic nervous activity, as inferred from daytime urine NE, is related to changes in BP variability in OSA patients. BP variability is not specifically affected by CPAP.     

Falls in blood pressure in patients with obstructive sleep apnoea after long-term nasal continuous positive airway pressure treatment

OBJECTIVES: Effective treatment of obstructive sleep apnoea (OSA) with nasal continuous positive airway pressure (nCPAP) lowers blood pressure (BP). The long-term effects of nCPAP treatment on BP in OSA patients are not well known. The time period of such treatment sufficient to lower BP in OSA patients is also not known. We investigated compliance with long-term nCPAP therapy and its effects on BP. METHODS: This observational study involved 66 OSA patients [59 men, seven women; mean age, 51 (48-54) years; body mass index (BMI), 28.7 (27.7-29.7) kg/m; apnoea and hypopnoea, 50.3 (45.6-55.0)/h; 95% confidence intervals]. BP and BMI were measured before the study and at two checkpoints after usage of nCPAP [620 (552-688) and 1071 (1000-1143) days]. RESULTS: The different times between the first and second checkpoints for detecting objective compliance were 17 (4-30) min (P = 0.003). Diastolic BP decreased by 5.9 (3.1-8.7) mmHg after 600 days nCPAP treatment and by 4.6 (2.0-7.2) mmHg after 1000 days (P = 0.0006). Systolic BP and BMI did not change significantly. Usage of nCPAP treatment for a daily average of 3 h was needed to achieve a significant decrease in diastolic BP [7.4 (4.3-10.6) mmHg, P < 0.0001]. Diastolic BP of normotensive OSA patients did not change significantly by nCPAP treatment, but that of hypertensive OSA patients decreased significantly within 1 month-3 years of nCPAP treatment whether or not medication was used. CONCLUSIONS: In patients with severe OSA, the use of nCPAP for a daily average of 3 h would be sufficient to decrease the diastolic BP of hypertensive OSA patients.     

The effects of continuous positive airway pressure therapy withdrawal on cardiac repolarization: data from a randomized controlled trial

Aims The preliminary evidence supports an association between obstructive sleep apnoea (OSA), disturbed cardiac repolarization, and consequent cardiac dysrhythmias. The aim of the current trial was to assess the effects of continuous positive airway pressure (CPAP) therapy withdrawal on the measures of cardiac repolarization in patients with OSA. Methods and results Forty-one OSA patients established on CPAP treatment were randomized to either CPAP withdrawal (subtherapeutic CPAP) or continue therapeutic CPAP for 2 weeks. Polysomnography was performed, and indices of cardiac repolarization (QT(c), TpTe(c) intervals) and dispersion of repolarization (TpTe/QT ratio) were derived from 12-lead electrocardiography (ECG) at baseline and 2 weeks. Continuous positive airway pressure withdrawal led to a recurrence of OSA. Compared with therapeutic CPAP, subtherapeutic CPAP for 2 weeks was associated with a significant increase in the length of the QT(c) and TpTe(c) intervals (mean difference between groups 21.4 ms, 95% CI 11.3-1.6 ms, P < 0.001 and 14.4 ms, 95% CI 7.2-21.5 ms, P < 0.001, respectively) and in the TpTe/QT ratio (mean difference between groups 0.02, 95% CI 0.00-0.03, P = 0.020). There was a statistically significant correlation between the change in apnoea/hypopnoea index (AHI) from baseline, and both the change in the QT(c) interval and the TpTe(c) interval (r = 0.60, 95% CI 0.36-0.77, P < 0.001 and r = 0.45, 95% CI 0.17-0.67, P = 0.003, n = 41, respectively). Conclusion Continuous positive airway pressure withdrawal is associated with the prolongation of the QT(c) and TpTe(c) intervals and TpTe/QT ratio, which may provide a possible mechanistic link between OSA, cardiac dysrhythmias, and thus sudden cardiac death.     

Effect of continuous positive airway pressure on ambulatory BP in patients with sleep apnea and hypertension: a placebo-controlled trial

BACKGROUND: Obstructive sleep apnea syndrome (OSAS) is an independent risk factor for arterial hypertension. Several controlled trials have investigated the effect of continuous positive airway pressure (CPAP) on BP in patients with OSAS, but its effect on hypertensive patients has not been analyzed specifically. OBJECTIVE: To analyze the effect of CPAP on ambulatory BP in patients with OSAS and hypertension who were undergoing antihypertensive treatment. Design and patients: We conducted a parallel, randomized, placebo-controlled trial in 68 patients with OSAS and hypertension, who were receiving treatment with antihypertensive medication. Patients were randomly allocated to either therapeutic or subtherapeutic CPAP for 4 weeks. Ambulatory BP was registered at baseline and after treatment. Antihypertensive treatment was not changed during the study. Changes in BP were assessed on an intention-to-treat basis. RESULTS: There were no baseline differences in the apnea-hypopnea index, comorbidities, or ambulatory BP between groups. Objective compliance with CPAP was similar in both the therapeutic and subtherapeutic groups (5.0 +/- 1.4 h/d vs 4.4 +/- 1.9 h/d, respectively; p = 0.13 [mean +/- SD]). There was a small and statistically nonsignificant decrease (- 0.3 +/- 6.3 mm Hg vs - 1.1 +/- 7.9 mm Hg; difference, - 0.8 mm Hg [95% confidence interval, - 2.7 to 4.3]; p = 0.65) in 24-h mean BP (24hMBP) in both subtherapeutic and therapeutic groups after 4 weeks of treatment. No significant changes in systolic, diastolic, daytime, or nighttime BP were observed. The normal circadian dipper pattern was restored in a higher proportion of patients in the therapeutic group compared to the subtherapeutic CPAP group, although differences were not significant (11 of 32 patients vs 3 of 25 patients; odds ratio, 3.84; 95% confidence interval, 0.82 to 20.30; p = 0.10). There was no correlation between the magnitude of change in 24hMBP and CPAP compliance, OSAS severity, or number of antihypertensive drugs used. CONCLUSION: Four weeks of CPAP did not reduce BP in patients with OSAS and hypertension who were treated with antihypertensive medication, compared to placebo group.     

Relationship between Chemosensitivity, Obesity and Blood Pressure in Obstructive Sleep Apnoea

It has previously been documented that patients with obstructive sleep apnoea (OSA) have an abnormal blood pressure (pressor) response to acute hypoxia when awake. The relationship between hypoxic chemosensitivity and 24 h blood pressure in OSA is not known. Twenty-four hour ambulatory BP (ABP) was measured at 15 min intervals for 24 h using a non-invasive device (Oxford Medilog ABP or Spacelabs 90207 recorder) in 49 men (mean age 51 ± 9 years), with OSA. The BP response to acute hypoxia was measured either directly (radial arterial line) or indirectly (Finapress) during wakefulness. The pressor response to hypoxia (expressed as the slope of the regression line of mean BP on % fall in arterial oxygen saturation) was compared with the results of the ABP recording, sleep study data and clinical variables. A pressor response to acute hypoxia was present in all patients (mean 1.4 ± 1.1 mmHg/% δSaO₂, range 0.1-4.5). There was a relationship between the magnitude of the pressor response to hypoxia, severity of sleep apnoea (RDI and minimum SaO₂) and central obesity (waist measurement). In contrast, there was no relationship between BP response to hypoxia during wakefulness and 24-h BP. However, increasing obesity and severity of OSA were associated with loss of the normal fall in BP at night. We conclude that enhanced chemosensitivity is common in OSA but there is no demonstrable link between chemosensitivity and mean daytime or night-time ABP.     

Long-term effect of continuous positive airway pressure on BP in patients with hypertension and sleep apnea

OBJECTIVE: To analyze the long-term effect of continuous positive airway pressure (CPAP) on ambulatory BP in patients with obstructive sleep apnea (OSA) and hypertension, and to identify subgroups of patients for whom CPAP could be more effective. METHODS: We conducted a prospective, long-term follow-up trial (24 months) in 55 patients with OSA and hypertension (mean CPAP use, 5.3 +/- 1.9 h/d [+/- SD]). Twenty-four-hour ambulatory BP monitoring (ABPM) was measured at baseline and after intervention with CPAP on an intention-to-treat basis. In addition, the correlation between the changes in 24-h mean arterial pressure (24hMAP) and CPAP compliance, OSA severity, and baseline ABPM was assessed. RESULTS: At the end of follow-up, a significant decrease was shown only in diastolic BP (- 2.2 mm Hg; 95% confidence interval [CI], - 4.2 to - 0.1; p = 0.03) but not in 24hMAP or other ABPM parameters. However, a correlation between changes in 24hMAP and baseline systolic BP (r = - 0.43, p = 0.001), diastolic BP (r = - 0.38, p = 0.004), and hours of use of CPAP (r = - 0.30, p = 0.02) was observed. A significant decrease in the 24hMAP was achieved in a subgroup of patients with incompletely controlled hypertension at entry (- 4.4 mm Hg; 95% CI, - 7.9 to - 0.9 mm Hg; p = 0.01), as well as in those with CPAP compliance > 5.3 h/d (- 5.3 mm Hg; 95% CI, - 9.5 to - 1.2 mm Hg; p = 0.01). Linear regression analysis showed that baseline systolic BP and hours of CPAP were independent predictors of reductions in BP with CPAP. CONCLUSION: Long-term CPAP reduced BP modestly in the whole sample. However, patients with higher BP at entry and good CPAP compliance achieved significant reductions in BP.     

Circadian rhythm of blood pressure in patients with obstructive sleep apnea.

AIMS: The aims of this study were to examine the circadian variation in blood pressure (BP) in obstructive sleep apnea (OSA) and to compare this between normotensive and hypertensive subjects. METHODS: We measured 24-hour ambulatory BP (ABP) in 72 men (mean age 51 +/- 8 years), with OSA diagnosed on overnight sleep study. Measurements of BP were made at 15 min intervals for 24 h using either an Oxford Medilog ABP or Spacelabs 90207 recorder. All recordings were performed after > or = 3 week washout of anti-hypertensive drugs. The day-time monitoring period was defined as 07:00 hrs to 22:00 and night-time 22:00 to 07:00. The ratio of night:day systolic and diastolic BP was calculated. RESULTS: The patients were obese (mean body mass index 33 +/- 5 kg/m2) with a central pattern of obesity (waist:hip ratio 0.99 +/- 0.14, normal < 0.94). The mean 24-h ABP (systolic/diastolic) was 138 +/- 18/88 +/- 12 mmHg. The mean daytime ABP was 143 +/- 18/93 +/- 12 and night-time ABP 128 +/- 20/80 +/- 12 Hg. The night:day BP ratio was 0.90 +/- 0.07 (systolic) and 0.87 +/- 0.09 (diastolic) indicating that average BP was lower during the night. This pattern was similar in normotensive and hypertensive subjects. In contrast there was a significant relationship between increasing BMI and night:day blood pressure ratio (r = 0.56, p < 0.001) independent of the effects of OSA. CONCLUSION: In contrast to previous studies, men with OSA have a normal diurnal pattern of blood pressure levels. These findings suggest that any influence of OSA on BP is manifested throughout the 24-h period.     

Blood pressure responsiveness to obstructive events during sleep after chronic CPAP.

The aim of this study was to investigate whether chronic continuous positive airway pressure (CPAP) affects blood pressure (BP) responsiveness to obstructive events occurring on the first night of CPAP withdrawal in obstructive sleep apnoea (OSA) after chronic treatment. Thirteen male subjects with severe OSA underwent nocturnal polysomnography with beat-by-beat BP monitoring before treatment and after 4.9 +/- 3.4 months of home CPAP (mean daily use 5.1 +/- 1.7 h). Variations in oxyhaemoglobin saturation (deltaSa,O2), systolic (deltaPs), and diastolic (deltaPd) BP within nonrapid eye movement apnoeas and hypopnoeas were measured on a sample of pre- and post-treatment events. In addition, a pretreatment sample was selected for deltaSa,O2 to match post-treatment events. The higher the mean deltaSa,O2 was in the full pretreatment sample, the more deltaSa,O2, deltaPs and deltaPd were attenuated after treatment. Mean deltaPs decreased from 47.3 +/- 8.5 in the full pretreatment sample to 42.2 +/- 6.9 in the selected pretreatment sample, to 31.5 +/- 5.9 mmHg in the post-treatment sample. The post-treatment value differed significantly from both the pretreatment values. The corresponding values for mean deltaPd were 27.0 +/- 3.5, 24.0 +/- 3.1 and 19.6 +/- 3.7 mmHg, with all values differing significantly from each other. Chronic continuous positive airway pressure is followed by a decrease in apnoea/ hypopnoea-related blood pressure swings, possibly secondary to both reduced severity of event-related hypoxaemia and decreased responsiveness to obstructive events secondary to chronic prevention of nocturnal intermittent hypoxaemia.     

Treatment of obstructive sleep apnoea with nasal continuous positive airway pressure in stroke.

The prevalence of obstructive sleep apnoea (OSA) following stroke is high and OSA is associated with increased morbidity, mortality and poor functional outcome. Nasal continuous positive airway pressure (nCPAP) is the treatment of choice for OSA, but its effects in stroke patients are unknown. The effectiveness and acceptance of treatment with nCPAP in 105 stroke patients with OSA, admitted to rehabilitation was prospectively investigated. Subjective wellbeing was measured with a visual analogue scale in 41 patients and 24-h blood pressure was determined in 16 patients before and after 10 days of treatment. Differences were compared between patients who did and did not accept treatment. There was an 80% reduction of respiratory events with concomitant increase in oxygen saturation and improvement in sleep architecture. No serious side-effects were noticed. Seventy-four patients (70.5%) continued treatment at home. Nonacceptance was associated with a lower functional status, as measured by the Barthel Index, and the presence of aphasia. Ten days after initiation of nCPAP, compliant users showed a clear improvement in wellbeing (differences in visual analogue scale (deltaVAS) mean+/-SD 26+/-26 mm) versus noncompliant patients (deltaVAS 2+/-25 mm, p=0.021). Only the compliant group had a reduction in mean nocturnal blood pressure (deltaBP; -8+/-7.3 mmHg versus 0.8+/-8.4 mmHg, p=0.037). Stroke patients with obstructive sleep apnoea can be treated effectively with nasal continuous positive airway pressure and show a similar improvement and primary acceptance to obstructive sleep apnoea patients without stroke. Continuous positive airway pressure acceptance is associated with improved wellbeing and decreased nocturnal blood pressure.     

Variables affecting the change in systemic blood pressure in response to nasal CPAP in obstructive sleep apnea patients

We hypothesized that an improvement in systemic blood pressure (BP) during continuous positive airway pressure (CPAP) treatment of obstructive sleep apnea (OSA) would be related to severity of hypertension (HTN), morphometric parameters such as body mass index, and level of CPAP adherence. We tested this hypothesis with a retrospective review of 85 consecutive OSA patients who had completed diagnostic and CPAP titration polysomnograms and were equipped with a CPAP-adherence monitoring system for a minimum of 1 month of observation. Sphygmomanometer-obtained BP readings were compared at baseline and after 4–6 weeks of CPAP therapy. Presentation BP was significantly and strongly associated with the change in BP seen with treatment. Those with an elevated systolic and diastolic BP and those with an elevation of either systolic or diastolic BP showed a significant fall in BP on CPAP. Those with a BP below the hypertensive range of 140/90 on presentation did not have a significant drop in BP with CPAP. There were no significant changes in systolic, diastolic, or mean BP when patients were categorized by the severity of HTN, as determined by the number of antihypertensive medications prescribed or if they were categorized by the degree of CPAP adherence, objectively determined by the average use of more or less than 4 h/night. We conclude that HTN at initial presentation is among the most important indicators of potential benefit of CPAP administration on BP.     

Abnormal vasoactive hormones and 24-hour blood pressure in obstructive sleep apnea

BACKGROUND: Patients with obstructive sleep apnea (OSA) are at increased risk for hypertension. The mechanisms responsible for the development of hypertension are controversial. We hypothesized that patients with OSA had an abnormal 24-h blood pressure (BP) and an abnormal activity in vasoactive hormones, and that both BP and hormones were normalized during treatment with long-term nasal continuous positive airway pressure (CPAP). METHODS: The 24-h BP and plasma levels of the vasoactive hormones (renin, angiotensin II, aldosterone, atrial natriuretic peptide, brain natriuretic peptide, vasopressin, and endothelin-1) were measured in 24 patients with OSA and in 18 control subjects. Thirteen patients with OSA were reexamined after 14 months of CPAP therapy. RESULTS: Patients with OSA had significantly increased BP and heart rate and a reduced nocturnal BP drop. Both angiotensin II (13.3 +/- 1.6 v 7.8 +/- 1.0 pmol/L) and aldosterone (94.0 +/- 9.4 v 62.2 +/- 4.5 pmol/L) were significantly higher in OSA than in control subjects. Positive correlations were found between angiotensin II and daytime BP (systolic: r = 0.49, P <.01; diastolic: r = 0.52, P <.01). The CPAP therapy resulted in a decrease in BP, and this CPAP-induced reduction in BP was correlated with a decrease in both plasma renin (r = 0.76 to 0.92, all P <.01) and plasma angiotensin II concentration (r = 0.58 to 0.81, all P <.05). CONCLUSIONS: Plasma angiotensin II and aldosterone were elevated in OSA, and plasma angiotensin II was correlated with BP. Long-term CPAP reduced BP, and this decrease in BP was correlated with the reductions in plasma renin and angiotensin II levels. We suggest that OSA mediates hypertension, at least in part, via a stimulation of angiotensin II production.     

Established vascular effects of continuous positive airway pressure therapy in patients with obstructive sleep apnoea—an update

The aim of this review was to summarize the current data from randomised controlled trials (RCTs) on vascular effects of continuous positive airway pressure (CPAP) therapy in patients with obstructive sleep apnoea (OSA). There is good evidence from RCTs that CPAP lowers blood pressure (BP) to a clinically significant amount. The effect seems to be dependent on the hours of nightly CPAP usage. Data from RCTs have also proven a beneficial effect of CPAP on measures of vascular function such as endothelial function and arterial stiffness. However, there is still a lack of evidence from RCTs proving that CPAP reduces vascular events and mortality.     

Pulmonary hypertension in obstructive sleep apnoea: effects of continuous positive airway pressure: a randomized, controlled cross-over study.

AIMS: We tested the hypothesis that: (i) obstructive sleep apnoea (OSA) by itself originates pulmonary hypertension (PH); and (ii) the application of continuous positive airway pressure (CPAP) can reduce pulmonary pressure. METHODS AND RESULTS: In this randomized and cross-over trial, 23 middle-aged OSA (apnoea-hypopnoea index, 44.1 +/- 29.3 h(-1)) and otherwise healthy patients and 10 control subjects were included. OSA patients randomly received either sham or effective CPAP for 12 weeks. Echocardiographic parameters, blood pressure recordings, and urinary catecholamine levels were obtained at baseline and after both treatment modalities. At baseline, OSA patients had higher pulmonary artery systolic pressure than control subjects (29.8 +/- 8.8 vs. 23.4 +/- 4.1 mmHg, respectively, P = 0.036). Ten out of 23 patients [43%, (95% CI: 23-64%)] and none of the control subjects had PH at baseline (P = 0.012). Two patients were removed from the study because of inadequate CPAP compliance. Effective CPAP induced a significant reduction in the values for pulmonary systolic pressure (from 28.9 +/- 8.6 to 24.0 +/- 5.8 mmHg, P < 0.0001). The reduction was greatest in patients with either PH or left ventricular diastolic dysfunction at baseline. CONCLUSION: Severe OSA is independently associated with PH in direct relationship with disease severity and presence of diastolic dysfunction. Application of CPAP reduces pulmonary systolic pressure levels.     

Blood pressure changes after automatic and fixed CPAP in obstructive sleep apnea: relationship with nocturnal sympathetic activity

Treatment of obstructive sleep apnea (OSA) by continuous positive airway pressure (CPAP) usually causes a reduction in blood pressure (BP), but several factors may interfere with its effects. In addition, although a high sympathetic activity is considered a major contributor to increased BP in OSA, a relationship between changes in BP and in sympathetic nervous system activity after OSA treatment is uncertain. This study was undertaken to assess if, in OSA subjects under no pharmacologic treatment, treatment by CPAP applied at variable levels by an automatic device (APAP) may be followed by a BP reduction, and if that treatment is associated with parallel changes in BP and catecholamine excretion during the sleep hours. Nine subjects underwent 24-h ambulatory BP monitoring and nocturnal urinary catecholamine determinations before OSA treatment and 2 months following OSA treatment by APAP (Somnosmart2, Weinmann, Hamburg, Germany). Eight control subjects were treated by CPAP at a fixed level. After APAP treatment, systolic blood pressure (SBP) decreased during sleep (p < 0.05), while diastolic blood pressure (DBP) decreased both during wakefulness (p < 0.05) and sleep (p < 0.02). Similar changes were observed in subjects receiving fixed CPAP. Nocturnal DBP changes were correlated with norepinephrine (in the whole sample: r = .61, p < 0.02) and normetanephrine (r = .71, p < 0.01) changes. In OSA subjects under no pharmacologic treatment, APAP reduces BP during wakefulness and sleep, similarly to CPAP. A reduction in nocturnal sympathetic activity could contribute to the reduction in DBP during sleep following OSA treatment.     

Baroreflex control of heart rate during sleep in severe obstructive sleep apnoea: effects of acute CPAP.

Baroreflex control of heart rate during sleep (baroreflex sensitivity; BRS) has been shown to be depressed in obstructive sleep apnoea (OSA), and improved after treatment with continuous positive airway pressure (CPAP). Whether CPAP also acutely affects BRS during sleep in uncomplicated severe OSA is still debatable. Blood pressure was monitored during nocturnal polysomnography in 18 patients at baseline and during first-time CPAP application. Spontaneous BRS was analysed by the sequence method, and estimated as the mean sequence slope. CPAP did not acutely affect mean blood pressure or heart rate but decreased cardiovascular variability during sleep. Mean BRS increased slightly during CPAP application (from 6.5+/-2.4 to 7.5+/-2.9 ms x mmHg(-1)), mostly in response to decreasing blood pressure. The change in BRS did not correlate with changes in arterial oxygen saturation or apnoea/hypopnoea index. The small change in baroreflex control of heart rate during sleep at first application of continuous positive airway pressure in severe obstructive sleep apnoea was unrelated to the acute resolution of nocturnal hypoxaemia, and might reflect autonomic adjustments to positive intrathoracic pressure, and/or improved sleep architecture. The small increase in baroreflex control of heart rate during sleep may be of clinical relevance as it was accompanied by reduced cardiovascular variability, which is acknowledged as an independent cardiovascular risk factor.     

Cardiovascular and metabolic effects of CPAP in obese males with OSA.

Obstructive sleep apnoea is associated with increased blood pressure and other features of the metabolic syndrome. The aim of the present study was to determine the relative effectiveness of continuous positive airway pressure (CPAP) in modifying these outcomes. A randomised placebo-controlled blinded crossover trial comparing cardiovascular and metabolic outcomes after 6 weeks of therapeutic and sham CPAP was performed in 34 CPAP-na?ve patients (mean+/-SD body mass and respiratory disturbance indices were 36.1+/-7.6 and 39.7+/-13.8, respectively). Mean waking systolic and diastolic blood pressure fell by 6.7 and 4.9 mmHg, respectively, when compared with sham CPAP. No change was observed in glucose, lipids, insulin resistance or the proportion of patients with metabolic syndrome. In CPAP-compliant patients the fall in blood pressure was greater and the baroreceptor sensitivity improved significantly but no metabolic variable changed. In obese Caucasians with untreated obstructive sleep apnoea, continuous positive airways pressure can improve baroreceptor responsiveness and reduce waking blood pressure within 6 weeks, but this treatment period was insufficient to modify insulin resistance or change the metabolic profile. The mechanisms underlying this difference in the time course of blood pressure and metabolic response to continuous positive airway pressure in obstructive sleep apnoea requires further exploration.     

An auto-continuous positive airway pressure device controlled exclusively by the forced oscillation technique.

The forced oscillation technique (FOT) has been demonstrated to be a very sensitive tool for the assessment of upper airway obstruction during nasal continuous positive airway pressure (CPAP) therapy for obstructive sleep apnoea (OSA). The present study was designed to evaluate the therapeutic efficacy of a novel auto-CPAP device based exclusively on the FOT. Following manual CPAP titration, 18 patients with OSA (mean apnoea/hypopnoea index (AHI) 48.0+/-28.1) were allocated to conventional CPAP and auto-CPAP treatment under polysomnographic control in randomized order. The patients were asked to assess their subjective daytime sleepiness using the Epworth Sleepiness Scale (ESS). The mean AHI during auto-CPAP treatment was 3.4+/-3.4 and was comparable with that obtained during conventional CPAP treatment (4.2+/-3.6). The analysis of sleep architecture, the arousal index (6.6+/-2.1 versus 7.3+/-4.4) or the ESS (5.6+/-1.8 versus 7.3+/-4.4) did not reveal any significant differences. However, the mean CPAP pressure during auto-CPAP treatment (0.84+/-0.26 kPa) and in particular the pressure applied in the lateral body position (0.74+/-0.35 kPa), was significantly lower than that employed in conventional CPAP treatment (0.93+/-0.16 kPa, both comparisons: p<0.05). The auto-continuous positive airway pressure device proved equally as effective as conventional continuous positive airway pressure. However, the mean treatment pressure was significantly reduced, especially when patients were sleeping in the lateral position.     

Pulse wave analysis in a pilot randomised controlled trial of auto-adjusting and continuous positive airway pressure for obstructive sleep apnoea

Purpose  

Non-invasive measurements of arterial stiffness including the augmentation index (AIx) and central blood pressure (BP) have been used to assess the cardiovascular health of patients with obstructive sleep apnoea (OSA), a well-established independent risk factor of cardiovascular disease. Continuous positive airway pressure (CPAP) can significantly reduce the AIx, but no studies have analysed the effect of auto-adjusting PAP (APAP) or studied morbidly obese patients with severe OSA at higher risk of cardiovascular disease. In this randomised, single-blinded crossover pilot trial, we aimed to compare the efficacy of CPAP with APAP (ResMed S8 Autoset II) in improving peripheral BP, central BP and the AIx, using SphygmoCor technology.