Joint Symbolic Dynamic Analysis of Cardiorespiratory Interactions in Patients on Weaning Trials

Assessing autonomic control provides information about patho-physiological imbalances. Measures of variability of the cardiac interbeat duration RR(n) and the variability of the breath duration T
_Tot
(n) are sensitive to those changes. The interactions between RR(n) and T
_Tot
(n) are complex and strongly non-linear. A study of joint symbolic dynamics is presented as a new short-term non-linear analysis method to investigate these interactions in patients on weaning trials. 78 patients from mechanical ventilation are studied: Group A (patients that failed to maintain spontaneous breathing and were reconnected) and Group B (patients with successful trials). Using the concept of joint symbolic dynamics, cardiac and respiratory changes were transformed into a word series, and the probability of occurrence of each word type was calculated and compared between both groups. Significant differences were found in 13 words, and the most significant p
_n
(w
_{c010, r010}
): 0.0041 plusmn 0.0036 (group A) against 0.0012 plusmn 0.0024 (group B), p-value = 0.00001. The number of seldom occurring word types (forbidden words) also presents significant differences fw
_cr
: 6.9 plusmn 6.6 against 13.5 plusmn 5.3, p-value = 0.00004. Joint symbolic dynamics provides an efficient non-linear representation of cardiorespiratory interactions that offers simple physiological interpretations