Published ahead of print on July 17, 2003, doi:10.1164/rccm.200301-135OC Am. J. Respir. Crit. Care Med., Volume 168, Number 6, September 2003, 671-676 A more recent version of this article appeared on September 15, 2003
Submitted on January 30, 2003 CYCLIC CHANGES IN ARTERIAL PULSE DURING RESPIRATORY SUPPORT REVISITED BY DOPPLER-ECHOCARDIOGRAPHYAntoine Vieillard-Baron1,1 Medical Intensive Care Unit, University Hospital Ambroise Pare, Assistance Publique Hopitaux de Paris, Boulogne, France, 2 Department of Biostatistics, University Hospital Ambroise Pare, Assistance Publique Hopitaux de Paris, Boulogne, France * To whom correspondence should be addressed. E-mail: francois.jardin{at}apr.ap-hop-paris.fr.
It has long been known that there are cyclic changes in arterial pressure during mechanical ventilation. They are caused by cyclic changes in both right and left ventricular stroke output, occurring in opposite phases. As a result, arterial pulse is increased during inspiration, and decreased during expiration. A cyclic improvement in left ventricular systolic function could thus be expected during mechanical lung inflation. We tested this hypothesis in 31 septic patients mechanically ventilated in controlled mode, by combining left ventricular measurements by transesophageal echocardiography with invasive arterial pressure recordings and Doppler analysis of pulmonary venous flow, and right and left ventricular stroke output. Lung inflation by tidal ventilation significantly improved left ventricular stroke output (26±0.4 cm3/m2, mean±SEM, versus 22.3±0.4 cm3/m2 at end-expiration). Beat-to-beat analysis of pulmonary venous flow velocity illustrated the boosting effect on lung inflation on pulmonary venous return. The beneficial effect of inspiration thus appeared directly related to a significant increase in left ventricular diastolic volume (60.3±1.5 cm3/m2, versus 53.3±1.4 cm3/m2 at end-expiration), and, to a lesser extent, to an improved left ventricular ejection fraction. We concluded that the transient beneficial hemodynamic effect of tidal ventilation on the left ventricular pump is essentially mediated by an improved left ventricular filling. Key words: Mechanical ventilation, left ventricular preload, left ventricular afterload, left ventricular contractility, pulmonary venous floW
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