Biomaterial Database

Influence of ten-day head-down bedrest on human carotid baroreceptor-cardiac reflex function. 1992

D L Eckberg, and J M Fritsch

Department of Medicine, Hunter Holmes McGuire Department of Veterans Affairs Medical Center, Richmond, Virginia 23249.

We studied the effects of simulated microgravity on baroreceptor-cardiac reflex mechanisms, with complex pressure changes delivered to neck chambers worn by six healthy young men, before, during (days 1, 3, 6, and 10), and after ten days' 6 degrees head-down bedrest. During held expiration, a computer-driven bellows increased neck pressure to 40 mmHg for about 4 s, and then decreased pressure to -65, by 15 mmHg R-wave triggered decrements. We plotted R-R intervals as functions of carotid distending pressures (systolic less neck chamber pressures). Each experimental session comprised seven stimulus sequences delivered over about 15 min and averaged. Comparisons between results before bedrest and on the tenth day of bedrest showed that average baseline R-R intervals increased from 933 +/- (SEM) 24 to 1077 +/- 35 msec (P less than 0.05, Wilcoxon signed rank test); maximum slopes (R-R interval/carotid distending pressure) decreased from 4.5 +/- 0.4 to 3.6 +/- 0.7 msec/mmHg (P = 0.11); R-R interval response ranges decreased from 263 +/- 31 to 182 +/- 18 msec (P = 0.03); and operational points (positions of R-R intervals at resting pressures on the stimulus-response relation) remained constant. Our results suggest that head-down bedrest progressively impairs baroreceptor-cardiac reflex responses in healthy human subjects.

UI	MeSH Term	Description	Entries
D007024	Hypotension, Orthostatic	A significant drop in BLOOD PRESSURE after assuming a standing position. Orthostatic hypotension is a finding, and defined as a 20-mm Hg decrease in systolic pressure or a 10-mm Hg decrease in diastolic pressure 3 minutes after the person has risen from supine to standing. Symptoms generally include DIZZINESS, blurred vision, and SYNCOPE.	Hypotension, Postural,Orthostatic Hypotension,Postural Hypotension
D008297	Male		Males
D011311	Pressoreceptors	Receptors in the vascular system, particularly the aorta and carotid sinus, which are sensitive to stretch of the vessel walls.	Baroreceptors,Receptors, Stretch, Arterial,Receptors, Stretch, Vascular,Stretch Receptors, Arterial,Stretch Receptors, Vascular,Arterial Stretch Receptor,Arterial Stretch Receptors,Baroreceptor,Pressoreceptor,Receptor, Arterial Stretch,Receptor, Vascular Stretch,Receptors, Arterial Stretch,Receptors, Vascular Stretch,Stretch Receptor, Arterial,Stretch Receptor, Vascular,Vascular Stretch Receptor,Vascular Stretch Receptors
D001794	Blood Pressure	PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS.	Systolic Pressure,Diastolic Pressure,Pulse Pressure,Pressure, Blood,Pressure, Diastolic,Pressure, Pulse,Pressure, Systolic,Pressures, Systolic
D002339	Carotid Arteries	Either of the two principal arteries on both sides of the neck that supply blood to the head and neck; each divides into two branches, the internal carotid artery and the external carotid artery.	Arteries, Carotid,Artery, Carotid,Carotid Artery
D006321	Heart	The hollow, muscular organ that maintains the circulation of the blood.	Hearts
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000328	Adult	A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available.	Adults
D013026	Space Flight	Travel beyond the earth's atmosphere.	Space Exploration,Space Travel,Spaceflight,Exploration, Space,Explorations, Space,Flight, Space,Flights, Space,Space Explorations,Space Flights,Space Travels,Spaceflights,Travel, Space,Travels, Space
D014893	Weightlessness	Condition in which no acceleration, whether due to gravity or any other force, can be detected by an observer within a system. It also means the absence of weight or the absence of the force of gravity acting on a body. Microgravity, gravitational force between 0 and 10 -6 g, is included here. (From NASA Thesaurus, 1988)	Microgravity,Zero Gravity,Gravity, Zero