Many patients with OSA are also hypertensive. We hypothesized that CPAP therapy will lead to a long-term improvement in blood pressure control as reflected by the need for less intense antihypertensive therapy.
We identified 50 patients on therapy with moderate to severe OSA who began CPAP therapy between January 2003 and August 2004 and followed for 1 year at the Oklahoma City VA medical center by review of sleep lab logs. Blood pressures and medications were obtained from clinic and pharmacy records. Patients with a >5 mmHg decrease in blood pressure were considered responders and compared to non-responders. Data are presented as mean ± SEM. Comparisons were performed using ANOVA for continuous variables and the Pearson chi-square test for categorical variables. A p value <0.05 was considered statistically significant.
There were 32 responders and 18 nonresponders. A majority of both responders (77%) and nonresponders (74%) had severe OSA with an apnea-hypopnea index (AHI) > 30 events/h. Responders were older and had a higher pre-CPAP blood pressure than nonresponders (Table). The awake room air PaO2 was lower and the PaCO2 higher in nonresponders and their AHI and body mass index tended to be higher and their mean nocturnal O2 saturation lower. The blood pressure fell gradually after the institution of CPAP in the responders but was unchanged in the nonresponders. The improvement in the responders was greatest after 12 months of CPAP. The number of antihypertensive medications was similar in both groups at the start of CPAP therapy and after 12 months.
CPAP therapy produces a gradual reduction in blood pressure which is significant at 12 months. This benefit occurs without any change in antihypertensive therapy.
In the poorly controlled hypertensive patient with OSA, CPAP therapy will help lowers blood pressure while it treats the OSA.Table 1VariableResponders (n=32)Non-responders (n=18)p ValueAge (years)61.7 ± 1.455.3 ± 1.90.01PaCO2 (mmHg)*41.9 ± 1.852.6 ± 2.60.005PaO2 (mmHg)*82.3 ± 3.655.7 ± 5.10.0006Mean nocturnal Oxygen saturation (%)91.7 ± 0.689.7 ± 0.80.06AHI51.1 ± 5.667.1 ± 7.70.1Antihypertensive medication (n)2.4 ± 0.22.2 ± 0.30.7Baseline MAP (mm Hg)101.1 ± 1.695.4 ± 2.10.04MAP at 12 months (mmHg)86.9 ± 2.198.2 ± 2.50.001BMI (kg/m2)36.0 ± 1.538.6 ± 20.3*
PaO2 and PaCO2 were measured on room air
Tanveer Ahmed, None.