Comparison of objective methods to classify the pattern of respiratory sinus arrhythmia during mechanical ventilation and paced spontaneous breathing

Abstract

Respiratory sinus arrhythmia (RSA) is a fluctuation of heart period that occurs during a respiratory cycle. It has been suggested that inspiratory heart period acceleration and expiratory deceleration during spontaneous ventilation (henceforth named positive RSA) improve the efficiency of gas exchange compared to the absence or the inversion of such a pattern (negative RSA). During mechanical ventilation (MV), for which maximizing the efficiency of gas exchange is of critical importance, the pattern of RSA is still the object of debate. In order to gain a better insight into this matter, we compared five different methods of RSA classification using the data of five mechanically ventilated piglets. The comparison was repeated using the data of 15 volunteers undergoing a protocol of paced spontaneous breathing, which is expected to result in a positive RSA pattern. The results showed that the agreement between the employed methods is limited, suggesting that the lack of a consensus about the RSA pattern during MV is, at least in part, of methodological origin. However, independently of the method used, the pattern of RSA within the respiratory cycle was not consistent among the subjects and conditions of MV considered. Also, the outcomes showed that even during paced spontaneous breathing a negative RSA pattern might be present, when a low respiratory frequency is imposed.

Processing of fMRI-related anxiety and information flow between brain and body revealed a preponderance of oscillations at 0.15/0.16 Hz

“…Besides oscillations in blood pressure with frequencies below 0.1 Hz 43 , the cardiovascular rhythm in the 0.15-Hz band with an origin in the reticular formation in the brainstem 11 , and BOLD oscillations between 0.13 and 0.17 Hz 44 , coherent breathing and RRI oscillations at ~ 0.15 Hz have also been reported during low and elevated anxiety 33 . A wave-by-wave analysis in a few healthy subjects revealed a breathing period duration of 6.7 ± 0.33 s (mean ± SD) and a RRI period duration of 6.6 ± 0.29 s. This was associated with a coherence between the two rhythms, which is characteristic for negative RSA 34 , 35 .…”

“…The dominant information flow in this case is from respiratory to cardiac signals. Recent research from Rassler et al 33 , 34 shows that besides the classical or positive RSA also a paradoxical beat-to-beat interval (RRI) increase (cardio-deceleration) during inspiration or negative RSA (nRSA) can be observed 35 . In this case, the interaction between respiration and RRI is dominated by a strong feedback with a preference for a flow from cardiac to respiratory signals.…”

Processing of fMRI-related anxiety and bi-directional information flow between prefrontal cortex and brain stem

“…The brainstem is also important for anxiety processing. Notably, in situations of elevated anxiety, negative RSA (i.e., cardiac deceleration during inspiration, acceleration during expiration 32 ) is prevailing 33 . This negative RSA, which was primarily observed in frequency bands centered at 0.1 and 0.15 Hz 33 seems to be accompanied by two BOLD signals in brain stem.…”

Analysis of Respiratory Sinus Arrhythmia and Directed Information Flow between Brain and Body Indicate Different Management Strategies of fMRI-Related Anxiety

“…Prior to our observation, nRSA has been described in anesthetized patients [ 31 ] or in persons with paced slow breathing [ 32 ]. While classical RSA means a respiration-driven modulation in HR, the rather uncommon nRSA is thought to result from a change in dominance; this means that the cardiac rhythm gains dominance over the respiratory rhythm.…”

“…Of note, (classical) RSA and nRSA are not the only phase-relations in cardio-respiratory coupling. Breathing and RRI oscillations may adopt any other phase-relation, which is termed “indefinite RSA” [ 32 ]. The portion of indefinite RSA was higher during breathing in the 0.2–0.4 Hz band compared to slow breathing.…”