Ambulatory blood pressure in relation to oxygen desaturation index as simultaneously assessed by nighttime finger pulse oximetry at home

Obstructive sleep apnea in relation to beat-to-beat, reading-to-reading, and day-to-day blood pressure variability

We investigated blood pressure (BP) variability as assessed by beat-to-beat, reading-to-reading and day-to-day BP variability indices in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). In 786 hospitalized hypertensives (mean age, 53.2 years; 42.2% women), we performed 10-min beat-to-beat (n = 705), 24-h ambulatory (n = 779), and 7-day home BP (n = 445) measurements and the full overnight polysomnography. Mild, moderate and severe OSAHS were defined as an apnea-hypopnea index of 5-14, 15-29, and ≥ 30 events per hour, respectively. BP variability indices including variability independent of the mean (VIM), average real variability (ARV), and maximum-minimum difference (MMD), were compared across the OSAHS severity groups. In univariate analysis, beat-to-beat systolic VIM and MMD, reading-to-reading asleep systolic and diastolic ARV and MMD increased from patients without OSAHS, to patients with mild, moderate and severe OSAHS. This increasing trend for beat-to-beat systolic VIM and MMD remained statistically significant after adjustment for confounders (P ≤ 0.047). There was significant (P ≤ 0.039) interaction of the presence and severity of OSAHS with age and body mass index in relation to the beat-to-beat systolic VIM and MMD and with the presence of diabetes mellitus in relation to asleep systolic ARV. The association was stronger in younger (age < 50 years) and obese (body mass index ≥ 28 kg/m²) and diabetic patients. None of the day-to-day BP variability indices reached statistical significance (P ≥ 0.16). BP variability, in terms of beat-to-beat systolic VIM and MMD and asleep reading-to-reading asleep systolic ARV, were higher with the more severe OSAHS, especially in younger and obese and diabetic patients.

Ambulatory blood pressure monitoring for the management of hypertension

ABSTRACT

Ambulatory blood pressure monitoring (ABPM) has become indispensable in the current management of hypertension. ABPM is particularly useful in the accurate diagnosis of hypertension. Its diagnostic thresholds had been recently established based on hard clinical outcomes. Cross-classification of patients according to office and ambulatory blood pressure identifies white-coat, masked, and sustained hypertension. ABPM is also useful in cardiovascular (CV) risk assessment. It provides information on daytime and nighttime blood pressure and circadian rhythm, particularly nighttime blood pressure dipping. Nighttime blood pressure is predictive of CV risk independent of office and daytime blood pressure. Isolated nocturnal hypertension is a special form of masked hypertension, with normal daytime but elevated nocturnal blood pressure. It also helps in the evaluation of blood pressure fluctuation and variation, such as morning blood pressure surge and reading-to-reading blood pressure variability. ABPM may derive several other indexes, such as ambulatory blood pressure index and salt sensitivity index, which may be useful in CV evaluations.

Associations between nocturnal continuous blood pressure fluctuations and the characteristics of oxygen desaturation in patients with obstructive sleep apnea: a pilot study

BACKGROUND

Patients with obstructive sleep apnea (OSA) frequently experience apnea-related oxygen desaturation events (ODE) accompanied by striking blood pressure (BP) fluctuations during sleep. We aimed to investigate the effects of characteristics of ODE on nocturnal BP fluctuations in OSA patients.

METHODS AND RESULTS

A total of 6199 ODE were obtained from 30 patients with who underwent overnight portable monitoring and beat-to-beat BP monitoring simultaneously. The associations between nocturnal BP parameters and the characteristics of ODE were studied. The mean value of systolic BP (SBP) monitored during ODE was higher than the non-hypoxia SBP value (122.0 ± 15.9 vs. 120.4 ± 15.1 mmHg, P = 0.001) and nighttime SBP value (122.0 ± 15.9 vs. 120.8 ± 15.0 mmHg, P = 0.002). SBP variability (SBPV) during ODE was higher than the values not during ODE (14.0 ± 2.8 vs. 13.2 ± 2.6 mmHg, P = 0.043) and nighttime SBPV (14.0 ± 2.8 vs. 12.9 ± 2.3 mmHg, P < 0.001). Hypoxia SBP index, defined as the percentage of SBP surge (△SBP) ≥10 mmHg to all △SBP during ODE, increased with greater respiratory event index (P = 0.01). Both the coefficient of variation for SBP values of an ODE (SBPV') and event-related SBP elevation (△SBP') increased with raised amplitude of ODE (P < 0.001 for SBPV' and P < 0.001 for △SBP'). Similar results were observed when the duration of events was analyzed (P < 0.001 for SBPV' and P < 0.001 for △SBP').

CONCLUSION

BP related to ODE may be the main component of increased BP during sleep in OSA patients. In addition to the frequency of respiratory events, the amplitude and duration of ODE may have a role in nocturnal BP fluctuations in OSA patients.

A randomized controlled trial on ambulatory blood pressure lowering effect of CPAP in patients with obstructive sleep apnea and nocturnal hypertension

Objective: In a randomised controlled trial, we investigated the blood pressure (BP) lowering effect of continuous positive airway pressure (CPAP) in patients with moderate-severe obstructive sleep apnoea syndrome (OSAS, an apnoea-hypopnoea index, AHI of 15 or higher) and nocturnal hypertension (night-time systolic/diastolic BP ≥120/70 mmHg).Methods: Sixty patients were randomly assigned to CPAP or sham CPAP, while maintaining their antihypertensive treatment. Ambulatory BP monitoring was performed at baseline (first run-in visit) and the end of follow-up. Clinic and home BP were measured at baseline and each of the monthly follow-up visits.Results: Of the 60 patients, 47 completed the 3-month study. CPAP (n = 26), compared with sham CPAP (n = 21), slightly and non-significantly reduced 24-h systolic/diastolic BP by -2.8/-2.5 mmHg (p ≥ 0.27), with a slightly greater between-group difference in the daytime (-4.0/-2.8 mmHg, p ≥ 0.29) than night-time (-0.2/-1.5 mmHg, p ≥ 0.50). The CPAP treatment did not significantly influence clinic or home BP during follow-up (p ≥ 0.27). Nonetheless, simple and partial correlation analyses showed that the ambulatory BP lowering effect was dependent on the daytime pulse rate at baseline (r ≥ 0.47, p ≤ 0.01). In patients with a daytime pulse rate greater than 85 beats/min, the mean changes in daytime systolic BP were significantly greater in the CPAP (n = 10) than sham CPAP group (n = 11), with a between-group mean difference of -10.1 mmHg (p = 0.048).Conclusions: The CPAP treatment did not show significant ambulatory BP lowering effect in patients with moderate-severe OSAS and nocturnal hypertension. However, it may be effective in lowering daytime BP in patients with a faster pulse rate.