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Purpose: Patterned breathing allows standardized serial measurements of heart rate variability and baroreflex indices. The slow breathing augments these parameters, and regular exercises, including yoga breathing practices with even respiratory rates have long-term beneficial effects in cardiovascular diseases. The role of temporization of breathing phases, i.e. the ratio of expiration to inspiration, is not known. In order to characterize the hemodynamic and autonomic responses during varying breathing phases 27 volunteers performed three short breathing sessions at 6/minutes frequency with 5:5, 3:7 and 7:3 inspiration expiration ratios., Results: The immediate responses in arterial pressure and heart rate were negligible. The time domain parameters of heart rate variability (SDRR, PNN50,RMSSD) increased significantly with patterned breathing. So did the spontaneous baroreflex gain of increasing sequences (up-BRS, from 12 ± 7 to 17 ± 10 ms/mmHg, p < 0.05), and the cross-spectral low frequency gain, the LFalpha (from 11 ± 7 to 15 ± 7 ms/mmHg, p < 0.05). None of these parameters differed significantly from each other while using any of tested inspiratory-expiratory patterns., Conclusion: The major determinant of autonomic responses induced by slow patterned breathing is the breathing rate itself. From our observations, it follows that slow breathing exercises performed either with diagnostic or therapeutic purpose could be simplified, allowing more extensive investigations.

1. Although the increased heart rate variability in healthy subjects in association with slow patterned breathing and continuous positive airway pressure is well documented, there is no general agreement regarding the underlying mechanism. The arterial baroreceptor stimulation due to greater blood pressure variability, the stimulation of pulmonary stretch and low pressure baroreceptors can play important role in this phenomenon. 2. In order to assess the interplay between blood pressure and heart rate changes we have studied nine healthy volunteers (mean age was 22 yrs. range 19-24), by applying 6/min patterned breathing, and continuous positive airway pressure of 10 cm of water. ECG and finger blood pressure (Finapres 2300) was continuously recorded. The oscillation amplitude of R-R intervals were analysed as well as the time and frequency domain indexes of heart rate variability. The oscillation amplitude and the corresponding frequency domain components of systolic blood pressure were also calculated. 3. The forced deep breathing caused significant increase in heart rate variability as indicated by time and frequency domain analysis of R-R intervals (LF HRV ms2: spontaneous: 777.40 +/- 526.1, patterned breathing 6828.00 +/- 5468.0). The application of CPAP in the same rhythm during patterned breathing resulted in further enhancement in heart rate variability (LF HRV ms2: 9052.00 +/- 4533.0). The analysis of the same frequency domain components of systolic blood pressure showed marked elevation of the total and low frequency power during patterned breathing. (LF BPV mm Hg2: spontaneous: 8.24 +/- 6.2, patterned breathing: 16.22 +/- 9.7). Applying CPAP with the same breathing pattern elicited further significant increment in systolic blood pressure fluctuation (LF BPV mm Hg2: deep breathing + CPAP: 27.11 +/- 9.8). The baroreflex sensitivity as calculated from spontaneous HR and BP sequences was 11.66 +/- 2.9 at baseline and increased to 17.66 +/- 6.1 and changed to 15.22 +/- 3.2 with the addition of patterned breathing and CPAP, respectively. 4. Our findings indicate that the heart rate and blood pressure responses to slow patterned breathing may be interpreted as consequences of an altered baroreflex sensitivity. In contrast the active breathing with CPAP exerts mechanical effects which in turn present an augmented systemic baroreflex trigger, however, the baroreflex sensitivity remains unchanged.

The existence of an active vasodilator system in the human skin microvasculature is well documented, but its physiological role and the underlying mechanisms are not completely understood. Cutaneous blood flow increases during isometric handgrip exercise. To examine whether this response is mediated by active vasodilation, isometric handgrip exercise testing was performed in nine healthy subjects. Local iontophoresis of atropine was applied to the forearm skin. Skin blood flow (SBF) monitoring by means of laser Doppler flowmetry was combined with continuous noninvasive blood pressure monitoring. SBF monitoring was performed at a site pretreated with atropine and an adjacent control area. Mean arterial pressure (MAP) was recorded noninvasively. Cutaneous vascular resistance (CVR) was calculated as MAP/SBF for the atropine treated and the control areas. Changes in CVR were expressed as percent deviation from the baseline (dCVR). Isometric handgrip exercise resulted in a marked reduction in CVR at the control site (dCVR: -66 +/- 4%). In contrast, the CVR was not significantly altered at the atropinetreated site (2.4 +/- 7%). It is concluded that isometric exercise induces an atropine-sensitive vasodilation which is mediated by muscarinic receptors in the human skin.

Objective and Method: Laser Doppler flowmetry is a non-invasive tool in assessing the temporary changes of skin microcirculation. Another non-invasive equipment the Finapres 2300 finger blood pressure monitor provides a continuous blood pressure signal. The combination of the two devices allows short-term monitoring of the changes in the resistance of skin microvasculature. In order to assess the role of skin blood vessels in physiological responses to complex reflex tests Valsalva manoeuvre was performed by 12 healthy volunteers. For comparison a thermal stimulation (cold pressor) test was also done., Results: The two tests resulted in skin blood flow responses of similar magnitude. The changes in calculated regional peripheral resistance (dRPR) indicated that both responses involved active vasoconstrictor mechanisms. It is of importance that the active vasoconstriction could be documented only at the late strain phase (V2) but not in the early strain phase (V1) of the Valsalva manoeuvre (%dRPR in V1 = 0.14 vs. V2 = 0.96, p < 0.05)., Conclusions: In conclusion our findings support the theory that changes in the tone of the skin blood vessels parallel the changes in systemic vasculature in response to complex reflex tests. This is the first report which documents the feasibility of the continuous monitoring of the regional peripheral resistance.

Central hemodynamic responses during upright exercise were studied at 1 year in 40 orthotopic cardiac transplant recipients. Hemodynamic responses were characterized by slow rise in heart rate and blunted peak exercise heart rate response, a significant early increase in stroke index followed by a plateau phase, and a steady increase in ventricular filling pressures and pulmonary artery pressure. In spite of exclusive utilization of the Frank-Starling mechanism to augment cardiac output during early exercise, the pressure responses were comparable to those reported in normal subjects. Our observations also indicate that similarly to normal subjects, the heart rate response plays an important role in the cardiac output achieved at maximum exercise. Although patients with younger donor hearts achieved a more favorable maximum heart rate, the other hemodynamic parameters showed no correlation with the donor heart age. Thus, no hemodynamic disadvantage of older donor hearts could be demonstrated. These data provide further enlightenment regarding the mechanisms of the well-preserved functional capacity noted in these patients.

The evolution of resting hemodynamics was studied at 1 week and 1 year in 40 patients following orthotopic cardiac transplantation. Abnormal hemodynamics after transplantation, characterized by elevated ventricular filling pressures (indicating diastolic dysfunction) and also by pulmonary hypertension, showed normalization by 1 year. In the absence of innervation, the resting heart rate of heart transplant recipients should theoretically be close to the intrinsic heart rate predicted by the age of the donor heart. In this study, a high incidence of relative sinus bradycardia (an indicator of sinus node dysfunction) was noted in the first post-operative week, although again there was a tendency to normalization by 1 year. These beneficial changes help to explain the dramatic and sustained improvement in the functional capacity of these patients late after transplantation.