F. Yasuma et Ji. Hayano, Impact of acute hypoxia on heart rate and blood pressure variability in conscious dogs, AM J P-HEAR, 279(5), 2000, pp. H2344-H2349
Citations number
43
Categorie Soggetti
Cardiovascular & Hematology Research
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
To examine whether the impacts of hypoxia on autonomic regulations involve
the phasic modulations as well as tonic controls of cardiovascular variable
s, heart rate, blood pressure, and their variability during isocapnic progr
essive hypoxia were analyzed in trained conscious dogs prepared with a perm
anent tracheostomy and an implanted blood pressure telemetry unit. Data wer
e obtained at baseline and when minute ventilation ((V) over dot I) first r
eached 10 ((V) over dot I10), 15 ((V) over dot I15), and 20 ((V) over dot I
20) 1/min during hypoxia. Time-dependent changes in the amplitudes of the h
igh-frequency component of the R-R interval (RRIHF) and the low-frequency c
omponent of mean arterial pressure (MAPLF) were analyzed by complex demodul
ation. In a total of 47 progressive hypoxic runs in three dogs, RRIHF decre
ased at (V) over dot I15 and (V) over dot I20 and MAPLF increased at (V) ov
er dot I10 and (V) over dot I15 but not at (V) over dot I20, whereas heart
rate and arterial pressure increased progressively with advancing hypoxia.
We conclude that the autonomic responses to isocapnic progressive hypoxia i
nvolve tonic controls and phasic modulations of cardiovascular variables; t
he latter may be characterized by a progressive reduction in respiratory va
gal modulation of heart rate and a transient augmentation in low-frequency
sympathetic modulation of blood pressure.