Determinants of respiratory sinus arrhythmia in the vagotomized rabbit.

Abstract	After cardiac denervation, a small-amplitude respiratory sinus arrhythmia (RSA) has been described in animals and humans. Its mechanical and chemical determinants were investigated in 19 urethan-anesthetized, vagotomized, and mechanically ventilated rabbits. We measured the influence on RSA of arterial blood gases, beta-adrenergic blockade, and phasic and steady changes in right atrial pressure (RAP) induced by changes in tidal volume (VT, 20, 40, 60 ml), respiratory frequency (RF, 10, 20, 30 cycles/min), and dextran-induced RAP increases. Phasic changes in RAP during each recording were quantified as standard deviation of the first derivative of the RAP signal (dRAP) as a measure of magnitude of variations of the rate of change due to respiration. RSA was assessed by combined autoregressive power spectral analysis of R-R interval and respiration on sequences of 256 heart-beats. Despite vagotomy, RSA was present in all recordings in all animals. During room air breathing, RSA changes were dependent on RF and VT (P < 0.025 and P < 0.001, respectively) and correlated with dRAP (P < 0.001) and arterial PO2 (P < 0.001). beta-Adrenergic blockade did not change the amplitude of this residual RSA or its dependence on ventilatory mechanics. Dextran-induced increase in mean RAP from 2.9 to 11.9 mmHg did not modify RSA or dRAP. During 100% O2 inhalation, RSA changes were no longer significantly linked to RF and VT, and also the correlation of RSA with dRAP was reduced (P < 0.05). Changing the arterial PCO2 from 28 to 79 mmHg (induced by increasing dead space at fixed ventilation) did not modify RSA.(ABSTRACT TRUNCATED AT 250 WORDS)
Authors	S Perlini, P L Soldá, M Piepoli, G Sala-Gallini, A Calciati, G Finardi, L Bernardi
Journal	The American journal of physiology (Am J Physiol) Vol. 269 Issue 3 Pt 2 Pg. H909-15 (Sep 1995) ISSN: 0002-9513 [Print] United States
PMID	7573534 (Publication Type: Journal Article)
Chemical References	Adrenergic beta-Antagonists Carbon Dioxide Oxygen
Topics	Adrenergic beta-Antagonists (pharmacology) Anesthesia Animals Arrhythmia, Sinus (physiopathology) Atrial Function, Right Biomechanical Phenomena Carbon Dioxide Denervation Heart Rate Oxygen Parasympathetic Nervous System (physiopathology) Partial Pressure Pressure Rabbits Respiration Respiration, Artificial Thoracotomy Vagotomy

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