njit-etd2003-081 - New Jersey Institute of Technology

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mortality and sudden death. [2] Because of some of the similarities between patients
with severe pulmonary disease and patients with severe heart disease, the systematic
study of the autonomic disturbances in these individuals, along with an analysis of the
survival of the patients with and without treatment should be undertaken.
Respiratory sinus arrhythmia (RSA) is a phenomenon that has been recognized
and studied for years, and it has been described as a rhythmical fluctuation in R-R
intervals that is characterized by a decrease in the RR interval length during inspiration,
and an increase in the R-R interval length during expiration [2]. Spectral analysis
techniques have allowed researchers to conclude that RSA can primarily be attributed to
vagal activity and can be used as an index of vagal control of the heart. It has been
shown that the variation of blood pressure seen with respiration is also associated with
the heart rate variability. The physiologic mechanism of heart rate variability is
mediated through respiratory afferents synapsing in the medulla oblongata and
entraining the central regulatory oscillator. Similarly, the mechanism of blood pressure
variability (BPV) is entrained to respiration, and is a combination of the effects of the
changes of stroke volume and the increase in vagal tone with inspiration. With the use
of spectral analysis, the raw data obtained by blood pressure and heart rate monitoring
can be broken down into useful observations. The interpretation of the significance of
the data are still being refined, but for several cardiac disease states there have been
clear indications that the loss of RSA is associated with increased morbidity, and
increased sudden death.
Since the relationship of altered heart rate variability and increased mortality
have been documented in cardiac populations, the population of patients with severe