CENTRAL SLEEP APNEAS AND BLOOD PRESSURE DURING ACUTE EXPOSURE TO MODERATE ALTITUDE. (June 2018) - Bilo, G.
Abstract : Objective: The association between obstructive sleep apnea (OSA) and both acute and chronic blood pressure (BP) increase is well established but it is not clear whether similar relationship exists for central sleep apneas (CSA). CSA are common in advanced heart failure but in these patients BP is usually low due to the effects of the disease and drugs used. Exposure to elevated altitudes may induce both CSA and BP increase. Aim of this study was to investigate the relationship between the presence of CSA and BP changes in healthy subjects acutely exposed to moderate altitude (MA). Design and method: 44 healthy volunteers (mean age 41 ± 12y, 16 males) residing at low altitude were transported to the altitude of 2035 m asl (Sestriere, Italy). During the first and second 24-hours of exposure they underwent in a random order 24-hour ambulatory BP monitoring (AND TM-2430) and cardiorespiratory sleep study (Embletta). The investigations were performed also at sea level (SL). Analyses involved pairwise comparisons of BP and cardiorespiratory variables between SL and MA as well as unadjusted and adjusted correlations between changes in these variables. Results: Significant increases occurred at MA in 24-hour, daytime and night-time systolic/diastolic BP (difference vs. SL 5.36 ± 8.4/3.55 ± 4.6, 4.98 ± 11.0/2.98 ± 6.7, 4.97 ± 10.8/3.75 ± 7.0 mmHg), respectively. No changes in the size of nocturnal BP fall were observed. In parallel, the rate of CSA increased (total Apnea Hypopnea Index: 1.55 vs 4.90, p < .0001; central apnea index: 0.75 vs 1.30, p = 0.0004; Oxygen Desaturation Index 1.50 vs 7.85, p < .0001 for SL vs MA, respectively), while mean nocturnal oxyhemoglobin saturation decreased (95.7 ± 1.5% vs. 91.6 ± 1.5%, p < .001). No correlations between BP changes and indices characterizing breathing during sleep were observed either in univariate analysis (all correlation coefficients < 0.2) or after considering possible confounders (age, sex, BMI). Conclusions: At variance with what observed with OSA, presence and severity of CSA induced in healthy lowlanders by MA exposure seems unrelated to BP increase occurring in this condition, either during day or during night-time. This may depend either on pathophysiological differences between OSA and CSA or on inadequacies of indices characterizing breathing pattern during sleep.