Impact of acute hypoxia on heart rate and blood pressure variability in conscious dogs

• Published in: American journal of physiology. Heart and circulatory physiology 2000-11, Vol.279 (5), p.H2344-H2349
• Main Authors: Yasuma, Fumihiko, Hayano, Jun-Ichiro
• Format: Article
• Language: English
• Subjects: Acute Disease; Animals; Arrhythmia, Sinus - physiopathology; Biological Clocks; Blood Pressure; Consciousness; Disease Progression; Dogs; Electrocardiography; Heart Rate; Hypoxia - physiopathology; Signal Processing, Computer-Assisted; Tidal Volume
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.2000.279.5.h2344

1  First Department of Internal Medicine, Nagoya University School of Medicine, Nagoya 466-8550; and 2  Third Department of Internal Medicine, Nagoya City University Medical School, Nagoya 467-8601, Japan To examine whether the impacts of hypoxia on autonomic regulations involve the phasic modulations as well as tonic controls of cardiovascular variables, heart rate, blood pressure, and their variability during isocapnic progressive hypoxia were analyzed in trained conscious dogs prepared with a permanent tracheostomy and an implanted blood pressure telemetry unit. Data were obtained at baseline and when minute ventilation ( I ) first reached 10   ( I 10), 15 ( I 15), and 20 ( I 20) l/min during hypoxia. Time-dependent changes in the amplitudes of the high-frequency component of the R-R interval (RRIHF) and the low-frequency component of mean arterial pressure (MAPLF) were analyzed by complex demodulation. In a total of 47 progressive hypoxic runs in three dogs, RRIHF decreased at I 15 and I 20 and MAPLF increased at I 10 and I 15 but not at I 20, whereas heart rate and arterial pressure increased progressively with advancing hypoxia. We conclude that the autonomic responses to isocapnic progressive hypoxia involve tonic controls and phasic modulations of cardiovascular variables; the latter may be characterized by a progressive reduction in respiratory vagal modulation of heart rate and a transient augmentation in low-frequency sympathetic modulation of blood pressure. sympathetic nervous system; parasympathetic nervous system; trained dog; complex demodulation; respiratory sinus arrhythmia; Mayer waves