HEMODYNAMIC FACTORS REGULATING BLOOD-PRESSURE DURING SLEEP IN PATIENTS WITH MILD ESSENTIAL-HYPERTENSION

Blood pressure (BP) values (systolic BP=Ps, diastolic BP=Pd, heart rat e=HR) fluctuate widely throughout the day, and are at their lowest lev els during sleep (sleep-Ps=Ps(0), sleep-Pd=Pd-0, sleep-HR=HR(0)). We a nalyzed the relationships among these values using the Windkessel mode l (logarithmic gradient of diastolic pressure decay A=E/R, E=elastic m odulus, R=vascular resistance). Intra-arterial BP and ECG were recorde d throughout 24 hours in 23 patients with mild essential hypertension (EH) by telemetry, and EEG was monitored during the night. The wavefor m of each BP pulse was analyzed by computer. The dye-dilution method w as used to obtain the cardiac output while the subjects were awake, re cumbent and during slow-wave sleep on the EEG. A high correlation coef ficient (r) was observed between mean BP and root EX root during sleep (r=0.88, p<0.001). Sleep-HR was determined from the waveform that mos t effectively permitted peripheral blood flow. Furthermore, the simple algebraic relationships Pd is-approximately-equal-to phi X Pd-0 and p hi is-approximately-equal-to FI+a(1)(BI)+b(1) (a(1),b(1)=constant) wer e observed between Pd-0 and different 24 h Pd values [FI=e(A(RRo-RR)); BI=baroreflex index=RRXPd/(RR(0)XPd(0))-1, which was significantly co rrelated with the baroreflex sensitivity, r=0.79; RR(0) and RR are the RR intervals in Pd-0 and Pd waves]. The mean r between Pd(0)X phi and the actual Pd over 24 h was 0.91+/-0.02 (SD). We conclude that sleep- BP and sleep-HR depend mainly on root E x root R, m[m=log(e),(Ps/Pd)] and E/R, whereas BP variability (phi) over a 24 h period is related to HR variation, the baroreflex index and E/R in mild EH patients.