Among patients with severe obstructive sleep apnea (OSA) and untreated hypertension, those whose high blood pressure (BP) is induced by transient apnea events are likely to achieve lower blood pressure by using continuous positive airway pressure (CPAP), according to study findings published in the British Medical Journal Open Respiratory Research.
Severe OSA may trigger numerous pathways that are linked to increased BP and hypertension. Researchers sought to identify patients with OSA and untreated hypertension whose blood pressure could be reduced through CPAP treatment. The researchers hypothesized that patients with different levels of OSA-triggered BP surges would have different BP responses to CPAP therapy. Investigators defined a BP surge as the value of event-related systolic BP (SBP) elevation; the BP index was defined as the number of BP surge events that were at least 10 mm Hg per hour.
The researchers conducted a single-center, prospective observational study (ClinicalTrials.gov Identifier: NCT03246022) of patients aged 18 to 75 years with severe OSA and untreated hypertension who had never before used CPAP. Between April 2018 and July 2020, the researchers compiled BP surge/index patient profiles. Participants all had an in-office BP consistently higher than 140/90 mmHg and an apnea-hypopnea index (AHI) of at least 30 events per hour. At baseline, participants had a mean (SD) office SBP of 151.3 (7.4) mmHg and a mean diastolic (D)BP of 95.9 (6.8) mmHg.
Participants (mean age, 44.3 [9.9] years; 8.5% women; mean AHI, 66 [17.6] events/hour) were stratified into high and low BP surge groups (n=65 for each group) according to the median BP index. Each group received CPAP for 4 weeks (average CPAP duration 6.2 [1.2] hours/night; mean CPAP pressure 10.2 [1.3] mmHg).
At the 4-week follow-up, the researchers found a moderate but significant decrease in in-office and asleep BPs compared with baseline (decrease office SBP, 3.8 mmHg; 95% CI, 3.1-4.4; office DBP, 2.6 mmHg; 95% CI, 2.1-3.2; and asleep SBP, 5.5 mmHg; 95% CI, 4.3-6.7; asleep DBP, 3.0 mmHg; 95% CI, 2.4-3.6; all P <.05). Notably, the high surge group vs low surge group had a more significant decrease in in-office SBP (5.3 mmHg vs 2.2 mmHg; P =.003) and in-office DBP (4.0 mmHg vs 1.2 mmHg; P <.001). The disparity in decrease was more noticeable in the asleep SBP (9.0 mmHg vs 2.1 mmHg; P <.001). In the asleep DBP, there was no significant difference (4.1 mmHg vs 1.9 mmHg).
In the high BP surge group, 30 participants with a better BP response were subsequently followed-up at 24 months. CPAP compliance, sex, hypersomnolence, baseline BP, body mass index, and age — all factors affecting BP decrease during treatment with CPAP — were assessed with multiple linear regression models. The researchers found optimal BP control was reached in 60% of these patients and more than 83% achieved a BP of less than140/90 mmHg after 24 months of CPAP (notably, 5 patients did not complete follow-up). Baseline vs 24-month follow-up in-office SBP was 151.4 mmHg vs 129.7 mmHg and in office DBP was 98.0 mmHg vs 85.3 mmHg. BP decrease was significantly associated with BP index during CPAP treatment, according to linear regression. The researchers found no association between BP reductions and baseline BP values, hypersomnolence, CPAP use, or AHI.
Study limitations include selection bias, lack of generalizability beyond patients with severe OSA and untreated hypertension, and the use of a single-center observational design without randomized controls.
“In this study of 130 patients with severe OSA and untreated hypertension, we found that the impact of CPAP on BP control depended on the obstructive respiratory event-triggered BP surge profiles; only patients with high BP surge profiles could benefit from CPAP in terms of BP reduction,” the researchers concluded. “Further randomized controlled trials in large samples are needed to confirm our findings,” the researchers added.
This article originally appeared on Pulmonology Advisor
Meng Z, Chen Y, Yang T, et al. New perspective on exploring the predictive factors of blood pressure reduction during CPAP treatment in people with severe OSA and hypertension: A prospective observational study. BMJ Open Respir Res. May 2023;10(1):e001560. doi:10.1136/bmjresp-2022-001560