The arterial baroreflex and the cardiopulmonary reflex in borderline hypertension

An elevation of the cardiopulmonary baroreflex control of the forearm vascular resistances due to an impairment of the arterial baroreflex has been postulated in borderline hypertension. The purpose of the study is to verify this hypothesis. The arterial baroreflex sensitivity, measured by the phenylephrine method is similar in borderline hypertensive and normotensive subjects of the same age. The forearm and the splanchnic vascular resistances are studied in borderline hypertension and normotension during leg negative body pressure at -40 and -70 mmHg. Baseline forearm resistances are higher in borderline hypertension. The increase of forearm resistance is similar in borderline hypertension and normotension when variations are expressed in percentage of the basal values. The elevation of plasma norepinephrine is similar in the two groups. The tachycardia and the elevation of splanchnic resistances are similar in borderline hypertensive and normotensive subjects. We conclude that: The arterial baroreflex is acting normally in borderline hypertension. The cardiopulmonary baroreflex control of the forearm vascular resistances is normal in borderline hypertension. The elevation of the basal forearm vascular resistances is not due to a sympathetic hyperactivity.