Catheter-tipped micromanometers were used to simultaneously record left ventricular and aortic pressures, and left ventricular and aortic internal phonocardiograms in order to determine if they had a common mode of origin and propagation. Spectrographic analysis showed that even with high-pass filtration the phonocardiogram obtained with a commonly used system (Millar) contained large amounts of energy in the subaudible frequency range (below 40 Hz). It was possible to derive close facsimiles of the phonocardiograms by double differentiation of the corresponding pressure pulse and conversely to derive the pressure pulse by double integration of the phonocardiograms. The propagation velocities of the first heart sound, second heart sound, and the foot of the aortic pressure pulse were found to be similar and were respectively, 4.3 +/- 0.2, 4.6 +/- 0.3, and 4.2 +/- 0.2 m/sec (+/- SE). These data support the concept that the low frequency pressure variations produced by the heart, which predominate in the left ventricular and aortic pressure pulse waveforms, are generated and propagated in the same manner as the high frequency pressure variations, which are the first and second heart sounds.

Animals↗

PubMed1982

Relationship between stroke volume and pneumocardiogram.

The intratracheal pressure oscillations produced by the heartbeat, called the pneumocardiogram, were recorded in 15 dogs. It was found that a linear relationship existed between the amplitude of the major negative deflection of the pneumocardiogram and the cardiac stroke volume, the latter determined either by indicator dilution (avg r = 0.94) or by use of an electromagnetic flow probe (avg r = 0.95). This relationship existed in animals with both an open and a closed chest. The vector of left ventricular wall motion directed toward the lungs, determined by high-speed cineradiography of the motion of a tantalum marker inserted in the wall of the left ventricle, looked very similar to the pneumocardiogram. This study showed that the pneumocardiogram can be used as a noninvasive technique to measure changes in stroke volume and is caused primarily by the motion of the cardiac walls.

Animals↗

PubMed1981

Molecular diffusion cannot account for spreading of isotope distribution peaks during rapid axoplasmic transport.

Diffusion coefficients calculated from spreading peaks of isotope distributions formed during rapid axoplasmic transport are two orders of magnitude larger than coefficients established for proteins in water. For slow transport, however, the coefficients approximate those of diffusion in water. We propose a near-equilibrium partitioning mass transfer process as the major source of peak spreading during rapid transport and suggest the axon can be modeled by a chromatographic column.

Animals↗

PubMed1980