THE EFFECT OF CONTINUOUS POSITIVE AIRWAY PRESSURE TREATMENT ON CARDIOVASCULAR REACTIVITY IN OBSTRUCTIVE SLEEP APNEA.

Obstructive sleep apnea (OSA) is a disorder in which patients intermittently stop breathing while sleeping. OSA has been associated with an increased risk for cardiovascular disease. This study investigates the role of the blood pressure (BP) response to voluntary breath-holding as an indicator of treatment success. We have found that OSA patients have elevated BP responses to voluntary breath-holding compared to people of a similar age and body weight. This study has found that with adequate treatment, this BP response is effectively attenuated. We propose a voluntary 20 second breath-hold as an effective and objective measure of treatment success in OSA. Purpose (a): To investigate whether or not well-treated obstructive sleep apnea (OSA) subjects will have a decreased Δ systolic blood pressure (SBP) response to voluntary apnea than untreated subjects. Methods (b): 21 OSA patients were stratified into treated (n=15) and untreated (n=6) groups based on their Treatment Success Index (TSI). The TSI takes into account a patient’s continuous positive airway pressure (CPAP) compliance and reduction in apnea-hypopnea index (AHI). Patients with TSIs of less than 85 (out of 100) were considered “untreated” while those over 85 were considered “treated.” This study took place at Sleep Consultants, Inc (Fort Worth, TX). Patients were instrumented with 3-lead ECG, pulse oximeter and a Finometer, which recorded beat-to-beat blood pressure. After respiring normally 3 times, the patient was asked to initiate a voluntary apnea for 20 seconds and the SBP response was recorded. An unpaired t-test was performed on group averages, where a p2values were calculated where indicated with ANOVAs to determine significance. Results (c): The untreated mean ∆ SBP was 24.04 ± 7.271 mm Hg and the treated mean was 12.23 ± 3.57 mm Hg, which was significantly different (p=0.00165). TSI and ∆SBP were inversely and significantly correlated (P= -0.69, p=0.00119). The different treatment groups did not desaturate differently (p>0.05), and greater desaturations did not produce greater ∆ SBP responses (R2=0.003, p> 0.05). Conclusions (d): The SBP response to voluntary breath-holds decreases with adequate CPAP treatment independently from SaO2. Therefore, the underlying increase in sympathetic nervous activity (SNA) that drives the ∆ SBP response is likely attenuated with adequate CPAP treatment. This study proves the utility of this maneuver in evaluating treatment efficacy (i.e. reduction in SNA reactivity) in OSA patients in a clinical setting.