In vivo cardiac phase response curve elucidates human respiratory heart rate variability.

Recovering interaction of endogenous rhythms from observations is challenging, especially if a mathematical model explaining the behaviour of the system is unknown. The decisive information for successful reconstruction of the dynamics is the sensitivity of an oscillator to external influences, which is quantified by its phase response curve. Here we present a technique that allows the extraction of the phase response curve from a non-invasive observation of a system consisting of two interacting oscillators--in this case heartbeat and respiration--in its natural environment and under free-running conditions. We use this method to obtain the phase-coupling functions describing cardiorespiratory interactions and the phase response curve of 17 healthy humans. We show for the first time the phase at which the cardiac beat is susceptible to respiratory drive and extract the respiratory-related component of heart rate variability. This non-invasive method for the determination of phase response curves of coupled oscillators may find application in many scientific disciplines.

Bridging different perspectives of the physiological and mathematical disciplines.

The goal of this report is to discuss educational approaches for bridging the different perspectives of the physiological and mathematical disciplines. These approaches can enhance the learning experience for physiology, medical, and mathematics students and simultaneously act to stimulate mathematical/physiological/clinical interdisciplinary research. While physiology education incorporates mathematics, via equations and formulas, it does not typically provide a foundation for interdisciplinary research linking mathematics and physiology. Here, we provide insights and ideas derived from interdisciplinary seminars involving mathematicians and physiologists that have been conducted over the last decade. The approaches described here can be used as templates for giving physiology and medical students insights into how sophisticated tools from mathematics can be applied and how the disciplines of mathematics and physiology can be integrated in research, thereby fostering a foundation for interdisciplinary collaboration. These templates are equally applicable to linking mathematical methods with other life and health sciences in the educational process.

Physiological considerations about life cycles of universities.

In Austria, a new federal law concerning university reorganization (UG 2002) has led to the former university medical faculties in Vienna, Innsbruck and Graz becoming independent medical universities, despite warnings by competent persons that this could have negative consequences. One logical consequence for example, is a certain isolationist trend that will eventually lead to medicine withdrawing into a kind of "splendid isolation", physically separated, even, from the rest in brand new buildings. The splitting of each of the three Austrian universities, which included Medical Faculties, into a new Medical University and a 'Rest University', has led to the growth of two daughter cells each now larger in terms of administration than the former university. The historical development of universities in Europe has seen times of affluence and times of decline. The recent new laws will for a long period have a marked impact on medicine and on the Medical Universities.

Why life oscillates--biological rhythms and health.

A multitude of biological rhythms have been identified in the whole organism as well as within each living cell. Some of these rhythms reflect adaptations to our environment, while others run on their own. Recent evidence shows that these rhythms and their interaction might be more important not only for recreation but also for our health. Disturbance of the circadian rhythms by jet lag or shift work not only disturbs our metabolic balance but also increases the incidence of cancer. Rhythms in the organism obviously stabilize systemic functions: They increase organismic stability by calibrating the system's characteristics. Regulation curves in time and space are crucial for controlling physiological long-term stability. To be continuously aware of its properties an autopetic system may vary its parameters slightly over several time scales at different frequencies--akin to what our body does, e.g. in heart-rate variability.

Noninvasive assessment of vascular function.

Impaired arterial compliance contributing to increased blood pressure and cardiac workload is well accepted as a major factor in cardiovascular disease. Information on local arterial compliance is obtained when analyzing the deformation of selected arterial segments under stress. A more global measure of arterial compliance is obtained by analyzing the arterial pulse by so-called pulse wave analysis. The arterial pulse, even when measured locally, carries characteristic information from the whole arterial system because of reflection of waves at distinct sites of the arterial system. Pulse wave velocity and the transfer function for pulse transmission is obtained from the combined measurement of arterial pulses at proximal and distal measuring points. Both pulse wave velocity and transfer function importantly, but not exclusively, depend on arterial compliance. The reconstruction of the aortic pulse from peripheral pulse measurements using a population-based transfer function finally provides information on central effects of reduced arterial compliance and increased peripheral resistance which may help in the diagnosis and treatment of vascular disease.

Classification of sudden infant death (SID) cases in a multidisciplinary setting. Ten years experience in Styria (Austria).

OBJECTIVE: Sudden infant death syndrome (SIDS) remains a challenge for health professionals despite decreasing rates in recent years. The figures for different areas and time periods are hardly comparable, because of differences in postmortem investigations and classification criteria. In 1992, the European Society for the Study and Prevention of Infant Deaths (ESPID) proposed a classification for any sudden and unexpected death in infancy. This proposal has been used in our study since 1993 to better classify sudden infant death (SID) cases. METHOD: 56 consecutive SID cases observed between 1993 and 2002 in Styria, the south-eastern province of Austria, were analysed by a multidisciplinary team of health professionals. The study group consisted of pediatricians, forensic pathologists, pathologists, psychologists, nurses, members of the parents' association and health authorities. SID cases were analysed with regard to potential risk factors during pregnancy and early life, the circumstances of death (death scene) and post-mortem findings. From the latter, every SID was classified as either 1) classic SIDS, 2) borderline SIDS, 3) non-autopsied SID or 4) explained death. RESULTS: Of the 56 SID cases, 22 were assigned to category 1, 19 to category 2, four to category 3, and in 11 cases death could be explained by major post-mortem findings. For 17/22 cases in category 1 and 11/19 cases in category 2, the death scene investigation showed the typical risk profile of manner of bedding and/or environmental conditions. In three cases, child abuse or infanticide was considered possible but could not be proven despite careful autopsy. In recent years, SIDS incidence in Styria has decreased to approximately 0.18/1,000 live-born infants, and the few deaths still occurring mainly present with the typical risk profile. CONCLUSION: An extensive analysis of SID events is a prerequisite for reliable and comparable SIDS statistics. Our data show that in several SID cases careful post-mortem examinations led to an explanation of death. In other cases, minor alterations may have contributed to the lethal event. These findings should therefore be considered in the classification of SIDs. The ESPID classification of 1992 appears to be very useful for this purpose and its use may therefore be recommended.