Effect of phasic respiration on left ventricular dimension and performance in a normal population. An echocardiographic study.

Echocardiographic examination of the left ventricle (LV) in 30 normal subjects, 5 to 47 years of age, was performed in order to analyze the effects of phasic respiration on LV dimensions and derived LV function. Peak expiratory and peak inspiratory LV diastolic and systolic dimensions were measured and extrapolated to volume estimates using a standard formula. Although there was wide variation in the individual measurements, and particularly in systolic dimension, the mean peak inspiratory diastolic dimension, derived diastolic volume, and stroke volume all decreased significantly (P less than 0.001); a smaller decrease in ejection fraction was seen (P less than 0.02), while the changes in mean end-systolic dimension and end-systolic volume were not significant. While these observed changes may reflect a true physiologic variation, an artifactual component cannot be excluded. Regardless of their physiologic significance, however, these data show that the effect of phasic respiration is a factor to be considered in correlative echocardiographic studies of LV function in both normal and, possibly, pathologic cardiovascular conditions.