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Heart rate and breathing rate fluctuations represent interacting physiological oscillations. These interactions are commonly studied using respiratory sinus arrhythmia (RSA) of heart rate variability (HRV) or analyzing cardiorespiratory synchronization. Earlier work has focused on a third type of relationship, the temporal ratio of respiration rate and heart rate (HRR). Each method seems to reveal a specific aspect of cardiorespiratory interaction and may be suitable for assessing states of arousal and relaxation of the organism. We used HRR in a study with 87 healthy subjects to determine the ability to relax during 5 day-resting periods in comparison to deep sleep relaxation. The degree to which a person during waking state could relax was compared to somatic complaints, health-related quality of life, anxiety and depression. Our results show, that HRR is barely connected to balance (LF/HF) in HRV, but significantly correlates to the perception of general health and mental well-being as well as to depression. If relaxation, as expressed in HRR, during day-resting is near to deep sleep relaxation, the subjects felt healthier, indicated better mental well-being and less depressive moods.

Pressure-controlled intermittent coronary sinus occlusion has been reported to reduce infarct size in dogs with coronary artery occlusion, possibly because of increased ischemic zone perfusion and washout of toxic metabolites. The influence of this intervention on regional myocardial function was investigated in open and closed chest dogs. In six open chest dogs with severe stenosis of the left anterior descending coronary artery and subsequent total occlusion, a 10 minute application of intermittent coronary sinus occlusion increased ischemic myocardial segment shortening from 5.5 ± 1.2 to 8.2 ± 2.6% (NS) and from −0.1 ± 2.1 to 2.3 ± 1.2% (NS), respectively.In eight closed chest anesthetized dogs, intermittent coronary sinus occlusion was applied for 2.5 hours between 30 minutes and 3 hours of intravascular balloon occlusion of the proximal left anterior descending coronary artery. Standardized two-dimensional echocardio-graphic measurements of left ventricular function were performed to derive systolic sectional and segmental fractional area changes in five short-axis cross sections of the left ventricle. Fractional area change in all the severely ischemic segments (< 5% systolic wall thickening) was −4.0 ± 4.7% at 30 minutes after occlusion, and increased with subsequent 60 and 150 minutes of treatment to 13.1 ± 3.3 and 7.0 ± 3.3%, respectively (p < 0.05). At the most extensively involved low papillary muscle level of the ventricle, regional ischemic fractional area change was increased by intermittent coronary sinus occlusion between 30 and 180 minutes of coronary occlusion from −0.4 ± 0.1 to 14.4 ± 4% (p < 0.05), whereas a further deterioration was noted in untreated dogs with coronary occlusion.Continuous arterial and coronary venous blood density measurements were performed in seven open chest dogs to determine the influence of pressure-controlled intermittent coronary sinus occlusion on ischemic myocardial washout. The arteriovenous density gradient was 0.16 ± 0.05 g/Iiter during coronary artery occlusion, and decreased to 0.05 ± 0.08 g/liter (p < 0.05) as a result of the intervention, suggesting a significant fluid washout from the myocardium. It is concluded that pressure-controlled intermittent coronary sinus occlusion provides recovery of cardiac function and that this benefit might be associated with enhanced ischemic zone washout.