Abstract 059: Continuous Positive Airway Pressure In The Treatment Of Nocturnal Supine Hypertension And Orthostatic Hypotension In Autonomic Failure

Supine hypertension affects most patients with autonomic failure (AF), complicates the treatment of orthostatic hypotension (OH) and induces nocturnal pressure diuresis, resulting in nocturnal volume depletion and worsening of daytime OH. However, it is often untreated for fear of worsening OH. We previously showed that continuous positive airway pressure (CPAP 4, 8, 12 and 16 cm H 2 O, each for 3 min) had an acute, dose-dependent, blood-pressure (BP)-lowering effect in these patients (maximal systolic BP [SBP] drop 22±4 mmHg with CPAP 16) driven by reductions in stroke volume (-16+3%) and cardiac output (-14±3%), suggesting a Valsalva-like effect. In this study, we hypothesized that overnight CPAP therapy can improve nocturnal supine hypertension, nocturia and daytime OH. Eleven AF patients with supine hypertension (age 74±2 years, 8 men, supine SBP 179±7 mmHg) had placebo or CPAP (8-12 cm H 2 O) applied for 8 hours (10pm-6am) in 2 separate nights. Supine BP was measured every 2 hr from 8pm-8am. Morning orthostatic tolerance was assessed at 8am. SBP significantly decreased during overnight CPAP therapy compared to placebo (Figure; P=0.044 by mixed-effects model) with a maximal reduction of 25±5 mmHg at 4 hours of CPAP. This BP effect was associated with lower nighttime diuresis (609±84 versus placebo 1004±160 mL; P=0.004) and improved morning orthostatic tolerance (AUC upright SBP 642±121 versus placebo 410±109 mmHg*min; P=0.014). In conclusion, CPAP is potentially a novel non-pharmacologic approach to treat the supine hypertension of AF that can improve nocturia and daytime OH.