Augmentation of respiratory sinus arrhythmia in response to progressive hypercapnia in conscious dogs

• Published in: American journal of physiology. Heart and circulatory physiology 2001-05, Vol.280 (5), p.H2336-H2341
• Main Authors: Yasuma, Fumihiko, Hayano, Jun-Ichiro
• Format: Article
• Language: English
• Subjects: Animals; Arrhythmia, Sinus - physiopathology; Autonomic Nervous System - physiology; Blood Pressure - physiology; Chemoreceptor Cells - physiology; Consciousness; Dogs; Heart Rate - physiology; Hypercapnia - physiopathology; Respiration
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.2001.280.5.h2336

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 Respiratory sinus arrhythmia (RSA) may serve to enhance pulmonary gas exchange efficiency by matching pulmonary blood flow with lung volume within each respiratory cycle. We examined the hypothesis that RSA is augmented as an active physiological response to hypercapnia. We measured electrocardiograms and arterial blood pressure during progressive hypercapnia in conscious dogs that were prepared with a permanent tracheostomy and an implanted blood pressure telemetry unit. The intensity of RSA was assessed continuously as the amplitude of respiratory fluctuation of heart rate using complex demodulation. In a total of 39 runs of hypercapnia in 3 dogs, RSA increased by 38 and 43% of the control level when minute ventilation reached 10 and 15 l/min, respectively ( P  <   0.0001 for both), and heart rate and mean arterial pressure showed no significant change. The increases in RSA were significant even after adjustment for the effects of increased tidal volume, respiratory rate, and respiratory fluctuation of arterial blood pressure ( P