AHEART March 47/3

Pinna, G. D., R. Maestri, A. Mortara, and M. T. La Rovere. Cardiorespiratory interactions during periodic breathing in awake chronic heart failure patients. Am. J. Physiol. Heart Circ. Physiol. 278: H932–H941, 2000.—We applied spectral techniques to the analysis of cardiorespiratory signals [instantaneous lung volume (ILV), instantaneous tidal volume (ITV), arterial O2 saturation (SaO2) at the ear, heart rate (HR), systolic (SAP), and diastolic (DAP) arterial pressure] during nonapneic periodic breathing (PB) in 29 awake chronic heart failure (CHF) patients and estimated the timing relationships between respiratory and slow cardiovascular (,0.04 Hz) oscillations. Our aim was 1) to elucidate major mechanisms involved in cardiorespiratory interactions during PB and 2) to test the hypothesis of a central vasomotor origin of PB. All cardiovascular signals were characterized by a dominant ($84% of total power) oscillation at the frequency of PB (mean 6 SE: 0.022 6 0.0008 Hz), highly coherent ($0.89), and delayed with respect to ITV (ITV-HR, 2.4 6 0.72 s; ITV-SAP, 6.7 6 0.65 s; ITV-DAP, 3.2 6 0.61 s; P , 0.01). SaO2 was highly coherent with (coherence function 5 0.96 6 0.009) and almost opposite in phase to ITV. These findings demonstrate the existence of a generalized cardiorespiratory rhythm led by the ventilatory oscillation and suggest that 1) the cyclic increase in inspiratory drive and cardiopulmonary reflexes and 2) mechanical effects of PBinduced changes in intrathoracic pressure are the more likely sources of the HR and blood pressure oscillations, respectively. The timing relationship between ITV and blood pressure signals excludes the possibility that PB represents the effect of a central vasomotor rhythm.