Exaggerated blood pressure variability in patients with pneumoconiosis: a pilot study.

BACKGROUND: Chronic hypoxia is a risk factor for cardiovascular disease, but its association with blood pressure (BP) remains unclear. We performed this study to clarify the hypothesis that chronic hypoxia is associated with abnormal BP variability in patients with pneumoconiosis.

METHODS: We recruited 19 patients with pneumoconiosis and 30 age- and BP level-matched control subjects. We used simultaneous pulse oximetry and ambulatory BP monitoring for all subjects. We evaluated their BP levels and variability by determining the SD and coefficient of variation (CV) of the BP data. The dipper pattern was defined as nocturnal BP fall ≥10%; the nondipper pattern was defined as nocturnal BP fall ≥0% but <10%; the riser pattern was defined as nocturnal BP fall <0%. Pearson and Spearman correlation coefficients were used to calculate the correlations between parameters.

RESULTS: In patients with pneumoconiosis, the daytime systolic BP (SBP) level was lower, the CV in 24-hour SBP (P < 0.05) and diastolic BP (P < 0.001) were higher than that in control subjects. And although not statistically significant (P = 0.13), the odds ratio of riser pattern was 3.73 in patients with pneumoconiosis, and their nighttime pulse rate was significantly higher (P < 0.05) than that in control subjects. The median daytime pulse oximetry oxygen saturation was inversely associated with mean (r = -0.30; P < 0.01) and SD (r = -0.38; P < 0.001) in daytime SBP. The median nighttime pulse oximetry oxygen saturation was inversely associated (r = -0.55; P < 0.001) and the mean nighttime pulse rate was associated (r = 0.51; P < 0.001) with CV in nighttime SBP. Partial pressure of oxygen was inversely associated with CV in daytime SBP (r = -0.24; P < 0.05).

CONCLUSIONS: Exaggerated BP variability was seen in patients with pneumoconiosis, and the measures of hypoxia were associated with large fluctuations in ambulatory BP. Chronic and intermittent hypoxia could be the contributing factors of these findings.

CLINICAL TRIAL REGISTRATION: Clinical Trial Number UMIN000000894 (University Hospital Medical Information Network Clinical Trials Registry website).