Cardiosomatic coupling as a differential indicator for coma depth and effectivity of sensorial stimulation

Coma is understood as a dissociation of endogenous brain stem rhythms or ph asic activity states of different compartments of the nervous system. Hence the awakening from coma is connected with a temporal coupling of activity states and this can be regarded as a presupposition for an integrated behav iour of the entire organism. Following this theory, we postulate that the a ctivity coupling between motoric tonus and heart rate (cardiosomatic coupli ng) increases with growing closeness to consciousness and that if the patie nt is addressed specifically (sensoric stimulation) a rectified alteration in coupling can be achieved. We examined 47 patients with severe brain-head traumata. They were measured in three different coma depths (Glasgow Coma Scale 3 to 5, 6 to 7, and 8 t o 10), some of them several times (but due to the clinical conditions not e ach patient in each of the coma depths). For every patient we recorded the muscle tonus of the forearm and the frontal muscles (by a surface EMG) as w ell as the heart rate (HR). Multiple measurements of one patient in one com a group were averaged, so that we had 82 measurements distributed over the three coma groups. We analysed the heart rate variability, EMG variability and the cardiosomatic coupling (crosscorrelation of HR and EMG) for a stand ardised intervention scheme with a 5-minute baseline and an intervention ph ase lasting for 6 minutes, which comprised a visual, acoustic, tactile and vestibular stimulation (each for 1.5 minutes). The result of this investigation shows that the cardiosomatic coupling incr eases with closeness to consciousness and under stimulation. Depending on t he analysed muscle tonus, the increase in cardiosomatic coupling can be con firmed from the point of reaching a GCS score of 8 to 10 (forearm musculatu re) or 6 to 7 (frontal musculature). Thus our initial thesis could be confi rmed. A possible explanation for the differential effect of forearm muscles and frontal muscles might be the fact that the frontal muscles belongs clo ser to the axial and proximal motor system and, in addition, mirrors emotio nal reactions, while the forearm muscles belongs to the distal motor system . During the re-integration of motor and cardiovascular system the centres which are controlled by the brain stem would then be reached first, even be fore cortical centres show a phase coupling.