Abstract
Heart-rate variability (HRV) induced by the Aschner eyeball-pressure test was analyzed in 7 adult dogs. Ocular compression (OC) used was 95 g/cm2, and duration was 20 seconds. Average, standard deviation (SDR-R), coefficient of variance (CVR-R) of the RR interval (RRI) of electrocardiogram, and beat-to-beat instantaneous heart rates (IHR) were used as indices for HRV. The RRI time series (RRITS) was divided into short-term (STTS) and long-term time series (LTTS) by means of a 13-point simple moving average method. The mean cycle of STTS correlated closely with that of the respiration curve (r=0.974), indicating that the STTS reflects respiratory sinus arrhythmia (RSA). No HRV variables in the STTS changed significantly, but SDRR and CVR-R in the RRITS and CVR-R in the LTTS increased significantly (P<0.05) as a result of OC. Therefore, OC-induced parasympathotonia may reflect on CVR-R of the RRI in dogs with RSA. The maximum physiological bradycardia caused by OC was-10.4±3.4 beats/min (-13.1±5.0%) compared to the mean IHR one minute before compression. On the basis of the 95% confidence interval of bradycardia (-12.9-7.8 beats/min)(-16.8-9.4%), we concluded that the hyper-reflexia of this test as applied to dogs represents a drop in heart rate of 17% or more.
