Blood pressure reactivity during Nasal Continuous Positive Airway Pressure in Obstructive Sleep Apnea Syndrome

Park, D H; Jeong, D U

Abstract

OBJECTIVES
Nasal continuous positive airway pressure (CPAP) corrected elevated blood pressure (BP) in some studies of obstructive sleep apnea syndrome (OSAS) but not in others. Such inconsistent results in previous studies might be due to differences in factors influencing the effects of CPAP on BP. The factors referred to include BP monitoring techniques, the characteristics of subjects, and method of CPAP application. Therefore, we evaluated the effects of one night CPAP application on BP and heart rate(HR) reactivity using non-invasive beat-to-beat BP and BP measurement in normotensive and hypertensive subjects with OSAS.
METHODS
Finger arterial BP and oxygen saturation monitoring with nocturnal polysomnography were performed in 10 OSAS patients (mean age 52.2+/-12.4 years ; 9 males, 1 female ; respiratory disturbance index (RDI)>5)for one baseline night and another CPAP night. Beat-to-beat measurement of BP and HR was done with finger arterial BP monitor(Finapres(R)) and mean arterial oxygen saturation (SaO2) was also measured at 2-second intervals for both nights. We compared the mean values of cardiovascular and respiratory variables between baseline and CPAP nights using Wilcoxon signed ranks test. Delta BP, defined as the subtracted value of CPAP night BP from baseline night BP, was correlated with age, body mass index (BMI), baseline night values of BP, BP variability, HR, HR variability, mean SaO2and respiratory disturbance index (RDI), and CPAP night values of TWT%(total wake time%)and CPAP pressure, using Spearman's correlation. Reults : 1) Although increase of mean SaO2 (p<.01)and decrease of RDI (p<.01) were observed on the CPAP night, there were no significant differences in other variables between two nights. 2) However, delta BP tended to increase or decease depending on BP values of the vaseline night and age. Delta systolic BP and baseline systolic BP showed a significant positive correlation (p<.01), but delta diastolic BP and baseline diastolic BP did not show a significant correlation except for a positive correlation in wake stage (p<.01). Delta diastolic BP and age showed a significant negative correlation (p<.05)during all stages except for REM stage, but delta systolic BP and age did not. 3) Delta systolic and diastolic BPs did not significantly correlate with other factors, such as BMI, baseline night values of BP variability, HR, HR variability, mean SaO2 and RDI, an CPAP night values of TWT% and CPAP pressure, except for a positive correlation of delta diastolic pressure and TWT% of CPAP night(p<.01).
CONCLUSION
We observed that systolic BP and diastolic BP tended to decrease, increase or remain still in accordance with the systolic BP level of vaseline night and aging. We suggest that BP reactivity by CPAP be dealt with as a complex phenomenon rather than a simple undifferentiated BP decrease.