Effect of Supplemental Oxygen on Blood Pressure in Obstructive Sleep Apnea (SOX). A Randomized Continuous Positive Airway Pressure Withdrawal Trial.

RATIONALE: Obstructive sleep apnea (OSA) is associated with systemic hypertension. Either overnight intermittent hypoxia, or the recurrent arousals that occur in OSA, could cause the daytime increases in blood pressure (BP). OBJECTIVES: To establish the role of intermittent hypoxia in the increased morning BP in patients with OSA. METHODS: Randomized, double-blinded, crossover trial assessing the effects of overnight supplemental oxygen versus air (sham) on morning BP, after continuous positive airway pressure (CPAP) withdrawal in patients with moderate to severe OSA. The primary outcome was the change in home morning BP after CPAP withdrawal for 14 nights, oxygen versus air. Secondary outcomes included oxygen desaturation index (ODI), apnea-hypopnea index (AHI), subjective sleepiness (Epworth Sleepiness Scale score), and objective sleepiness (Oxford Sleep Resistance Test). MEASUREMENTS AND MAIN RESULTS: Supplemental oxygen virtually abolished the BP rise after CPAP withdrawal and, compared with air, significantly reduced the rise in mean systolic BP (-6.6 mm Hg; 95% confidence interval [CI], -11.3 to -1.9; P = 0.008), mean diastolic BP (-4.6 mm Hg; 95% CI, -7.8 to -1.5; P = 0.006), and median ODI (-23.8/h; interquartile range, -31.0 to -16.3; P < 0.001) after CPAP withdrawal. There was no significant difference, oxygen versus air, in AHI, subjective sleepiness, or objective sleepiness. CONCLUSIONS: Supplemental oxygen virtually abolished the rise in morning BP during CPAP withdrawal. Supplemental oxygen substantially reduced intermittent hypoxia, but had a minimal effect on markers of arousal (including AHI), subjective sleepiness, or objective sleepiness. Therefore intermittent hypoxia, and not recurrent arousals, appears to be the dominant cause of daytime increases in BP in OSA.

Effect of CPAP on cardiovascular events in minimally symptomatic OSA: long-term follow-up of the MOSAIC randomised controlled trial.

The effect of continuous positive airway pressure (CPAP) on cardiovascular events is uncertain in minimally symptomatic obstructive sleep apnoea. Previous 2-year follow-up data from the Multicentre Obstructive Sleep Apnoea Intervention Cardiovascular (MOSAIC) trial showed a marginal reduction in cardiovascular events with CPAP therapy. We now present long-term MOSAIC study follow-up data. Median (first quartile, third quartile) follow-up was 5.0 (2.2, 5.0) and 3.7 (1.5, 5.0) years for CPAP and standard care, respectively. Compared to standard care, CPAP had no statistically significant effect on the risk of cardiovascular events (HR=0.83, p=0.54, 95% CI 0.46-1.51).

Accuracy of individual variables in the monitoring of long-term change in pulmonary sarcoidosis as judged by serial high-resolution CT scan data.

BACKGROUND: In pulmonary sarcoidosis, the optimal means of quantifying change is uncertain. The comparative usefulness of simple lung function trends and chest radiography remains unclear. We aimed to explore and contrast the disease-monitoring strategies of serial pulmonary function tests (PFTs) and chest radiography compared against morphologic change on high-resolution CT (HRCT) scan. METHODS: Seventy-three patients with sarcoidosis were identified who had two HRCT scans with concurrent chest radiography and PFTs. Chest radiography and HRCT scans were assessed by two radiologists for change in disease extent. Concordance between the scoring systems, as well as agreement between PFT trends (% change from baseline in FEV, FVC, and diffusing capacity of the lung for carbon monoxide [Dlco]), chest radiography, and chest HRCT scan change, were examined using the weighted κ coefficient of variation (Kw). RESULTS: There was fair agreement between change in extent of disease on chest radiograph and significant PFT trends (Kw = 0.35, P < .001) and moderate agreement between change in extent of disease on serial HRCT scan and significant PFT trends (Kw = 0.64, P < .0001). The integration of Dlco trends did not improve concordance between change on HRCT scan and PFT change. Change in gas transfer coefficient (ie, Dlco/alveolar volume) displayed no overall linkage with change in disease extent on chest radiograph (Kw = 0.07, P = .27) and only poor agreement with change in disease extent on HRCT scan (Kw = 0.17, P = .07). CONCLUSIONS: Significant PFT trends correlate better with morphologic change as defined by serial HRCT scan than extent of disease on radiograph. Isolated change in gas transfer coefficient is more frequently discordant with change in disease extent on chest radiograph and HRCT scan and may suggest a pulmonary vascular component.