Fluid displacement from the lower extremities to the upper body during sleep is strongly associated with obstructive sleep apnoea in hypertensive patients. The present pathophysiological study tests the hypothesis that intensified diuretic therapy will reduce the apnoea-hypopnoea index and blood pressure of uncontrolled hypertensive patients with obstructive sleep apnoea in proportion to the reduction in overnight change in leg fluid volume.
Uncontrolled treated hypertensive patients underwent overnight polysomnography and measurement of overnight changes in leg fluid volume and neck circumference. Those with an apnoea-hypopnoea index at least 20 events per hour (n = 16) received metolazone 2.5 mg and spironolactone 25 mg daily for 7 days after which the daily dose was doubled for 7 additional days. Baseline testing was again repeated.
Intensified diuretic therapy reduced the apnoea-hypopnoea index from 57.7 ± 33.0 to 48.5 ± 28.2 events per hour (P = 0.005), overnight change in leg fluid volume from –418.1 ± 177.5 to –307.5 ± 161.9 ml (P < 0.001) and overnight change in neck circumference from 1.2 ± 0.6 to 0.7 ± 0.4 cm (P < 0.001). There was an inverse correlation between the reduction in overnight change in leg fluid volume and decrease in apnoea-hypopnoea index (r = –0.734, P = 0.001). The reduction in overnight change in leg fluid volume was also significantly correlated with the change in morning blood pressure (r = 0.708, P = 0.002 for SBP; r = 0.512, P = 0.043 for DBP).
The findings provide further evidence that fluid redistribution from the legs to the neck during sleep contributes to the severity of obstructive sleep apnoea in hypertension and may be an important link between these two conditions.