Phase‐ and frequency coordination of cardiac and respiratory function

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Abstract
ECG and respiration (by nose thermistor sensor) were measured in 160 healthy volunteers under resting conditions. Frequency analysis allowed to distinguish fast (center frequency ≈ 0,25 Hertz), medium (center frequency ≈ 0,1 Hertz) and slow waves (center frequency = 0,05 Hertz) of heart rate variability. The fast waves are related to respiratory sinus arrhythmia, which mirrors parasympathetic tone and the slow waves are mainly connected with the sympathetic nervous activities, whereas medium waves are influenced by both the sympathetic and the parasympathetic nervous system. Simultaneously we calculated the heart ‐ respiration coupling by recording a total of ≈ 18.000 respiratory cycles as well as the time from the R‐peak to the onset of the next inspiration. Three distinct peaks of coincidence are related to afferents discharging in the isometric systolic phase (peak I ), to the baroreceptor afferents in the great arterial vessels (peak 2) and afferents excited in the relaxation or diastolic filling phase (peak 3), respectively . The pulse‐respiration quotient (PRQ) represents the state of the autonomie nervous system (ANS): Ergotropic conditions lead to an individual's PRQ with no special preference, whereas during tropho‐tropic conditions the PRQs exhibit a preference for a 4:1 ratio. The latter is shown by measurement under resting conditions. The above‐mentioned cardio‐respiratory interactions could be used for a multidimensional assessment of autonomie functions. Differentiation between ergotropy and trophotropy, sympathetic or parasympathetic arousal, sympathicotony and parasympathicotony is possible using these parameters and allows to study the autonomie activity from different viewpoints. Moreover, such a multidimensional description of the ANS might prove to be a valuable instrument for the clinical investigation of the state of the autonomie nervous system.