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The effect of respiration on diastolic blood flow velocities in the human heart.

This study was performed to evaluate the effects of respiration on diastolic blood flow velocity and its relevance for the determination of pulsed Doppler reference values from diastolic blood flow. Doppler signals were recorded from both the atrial and ventricular sides of the mitral valve and the tricuspid valve in 215 healthy volunteers (120 males and 95 females, with ages ranging from 1-65 years). Respiratory signals were recorded simultaneously by a mercury strain gauge around the thorax. From the medians of Doppler spectra the maximum velocity during early diastole (VmaxE), during atrial contraction (VmaxA) and the ratio between VmaxE and VmaxA (EA ratio) were obtained. On the atrial side of the tricuspid valve, VmaxE and VmaxA were significantly higher during inspiration than during expiration. On the ventricular side of the tricuspid valve, this was only found for VmaxE. On the atrial side of the mitral valve, VmaxE and VmaxA were significantly lower during inspiration than during expiration. At the ventricular side of the mitral valve, this was found only for VmaxE. No significant effect of respiration was found on the EA ratio. We conclude that there is a respiration-related effect on VmaxE and VmaxA. However, no significant effect is found on the EA ratio. Thus, for the determination of the EA ratio in intersubject studies, information about the respiratory cycle is not relevant.