Evolution of cardiorespiratory interactions with age.

We describe an analysis of cardiac and respiratory time series recorded from 189 subjects of both genders aged 16-90. By application of the synchrosqueezed wavelet transform, we extract the respiratory and cardiac frequencies and phases with better time resolution than is possible with the marked events procedure. By treating the heart and respiration as coupled oscillators, we then apply a method based on Bayesian inference to find the underlying coupling parameters and their time dependence, deriving from them measures such as synchronization, coupling directionality and the relative contributions of different mechanisms. We report a detailed analysis of the reconstructed cardiorespiratory coupling function, its time evolution and age dependence. We show that the direct and indirect respiratory modulations of the heart rate both decrease with age, and that the cardiorespiratory coupling becomes less stable and more time-variable.

Nonlinear dynamics of cardiovascular ageing.

The application of methods drawn from nonlinear and stochastic dynamics to the analysis of cardiovascular time series is reviewed, with particular reference to the identification of changes associated with ageing. The natural variability of the heart rate (HRV) is considered in detail, including the respiratory sinus arrhythmia (RSA) corresponding to modulation of the instantaneous cardiac frequency by the rhythm of respiration. HRV has been intensively studied using traditional spectral analyses, e.g. by Fourier transform or autoregressive methods, and, because of its complexity, has been used as a paradigm for testing several proposed new methods of complexity analysis. These methods are reviewed. The application of time-frequency methods to HRV is considered, including in particular the wavelet transform which can resolve the time-dependent spectral content of HRV. Attention is focused on the cardio-respiratory interaction by introduction of the respiratory frequency variability signal (RFV), which can be acquired simultaneously with HRV by use of a respiratory effort transducer. Current methods for the analysis of interacting oscillators are reviewed and applied to cardio-respiratory data, including those for the quantification of synchronization and direction of coupling. These reveal the effect of ageing on the cardio-respiratory interaction through changes in the mutual modulation of the instantaneous cardiac and respiratory frequencies. Analyses of blood flow signals recorded with laser Doppler flowmetry are reviewed and related to the current understanding of how endothelial-dependent oscillations evolve with age: the inner lining of the vessels (the endothelium) is shown to be of crucial importance to the emerging picture. It is concluded that analyses of the complex and nonlinear dynamics of the cardiovascular system can illuminate the mechanisms of blood circulation, and that the heart, the lungs and the vascular system function as a single entity in dynamical terms. Clear evidence is found for dynamical ageing.

[Clinical use of autologous frozen blood in the surgery of three esophageal cancer patients].

Autologous frozen blood transfusion (AFBT) has advantages both of autologous and frozen blood transfusion. In AFBT there are no remarkable adverse effects which often emerge after usual heterologous blood transfusion. As a rule, four hundred milliliters of blood were drawn twice from patients and reserved as autologous frozen blood (AFB) preoperatively. It is supposed that radical operation of esophageal cancer using only AFB is difficult to perform because of various kinds of preoperative risks. In this paper three cases of radical esophageal cancer operations, in which only AFBT were used are reported. Pre- and postoperative liver functions were uneventful. RBC counts, Hb and Hct dropped after drawing blood and did not recover until the day of operation. Postoperatively, they deteriorated further but recovered to initial values without any specific treatment within 5 months after operation. Pre- and postoperative PaO2 values of AFBT were not different from those of the usual blood transfusion. Thus using only AFBT, esophageal cancer operations were performed without any disadvantageous effects.