EFFECT OF INTRA-THORACIC PRESSURE ON LEFT-VENTRICULAR PERFORMANCE

Left ventricular dysfunction is common in respiratory-distress syndrome, asthma and obstructive lung disease. To understand the contribution of intrathoracic pressure to this problem, we studied the effects of Valsalva and Müller maneuvers on left ventricular function in eight patients. Implantation of intramyocardial markers permitted beat-by-beat measurement of the velocity of fiber shortening (VCF) and left ventricular volume. During the Müller maneuver, VCF and ejection fraction decreased despite an increase in left ventricular volume and a decline in arterial pressure. In addition, when arterial pressure was corrected for changes in intrapleural pressure during either maneuver it correlated better with left ventricular end-systolic volumes than did uncorrected arterial pressures. These findings suggest that negative intrathoracic pressure affects left ventricular function by increasing left ventricular transmural pressures and thus afterload. We conclude that large intrathoracic-pressure changes, such as those that occur in acute pulmonary disease, can influence cardiac performance. (N Engl J Med 301:453–459, 1979) PREVIOUS investigators1 2 3 4 5 have noted that respiration and respiratory maneuvers may affect cardiac function. The exact mechanisms by which left ventricular function is depressed during exacerbation of chronic obstructive lung disease, asthma, adult respiratory-distress syndrome and restrictive lung disease have been a subject of continuing controversy.6 7 8 9 10 11 Franklin et al.1 and Hoffman et al.4 measured instantaneous flows in the aorta and pulmonary artery and observed that, during inspiration, right ventricular stroke volume increased but left ventricular stroke volume decreased. These changes were attributed to alterations in ventricular filling produced by changes in intrathoracic pressure during normal inspiration. Best and Taylor12 have stated. © 1979, Massachusetts Medical Society. All rights reserved.