Effects of Injection Site on the Accuracy of Thermal Washout: Discussion (6)
How Did the Injection Timing Affect RVEF?
Stroke volumes are considered to vary stroke by stroke, but it is more reasonable to assume that they fluctuate physiologically with respiratory movement. CO could be calculated as the mean of a few strokes, and thereby might be affected less by respiration than stroke volume, as previously stated by McMillan and Morris; however, others insist that random thermodilution measurements of CO during intermittent positive pressure ventilation should be avoided. Compared with CO, RVEF may be affected more by the respiratory cycle because the preload and afterload of the RV are largely influenced by respiratory movement. buy cipro
Jardin and others found that RVEF fluctuates greatly from 0.71 ±0.19 at early expiration to 0.37 ±0.10 at midinspiration during mechanical ventilation, determined by two-dimensional echocardiography. What is the true RVEF is the major issue, and Assmann and Falke advocate an automatically timed injection technique (sets of four determinations equally spread throughout the respiratory cycle) and a transient increase of respiratory rate. Our patients could breathe for themselves but were affected by hypoxemia, and so were treated with CPAP (see “Methods and Materials”).