Effects of leukotriene receptor antagonists on vascular endothelial growth factor levels in asthma.

I thank Dr. Cole for focusing on a figure I recently published in CHEST (August 2004).1 However, I totally disagree with his comments. Dr. Cole claims that the time interval between the two peaks of the so-called camel transpulmonary thermodilution curve (with two humps) that was presented in my article is “much too short” to mimic a right-to-left intracardiac shunt. When the camel curve is due to a right-to-left intracardiac shunt, the time interval between the two peaks represents the blood transit time between the right and left atrium through the pulmonary circulation.2 When the camel curve is due to a cross-talk phenomenon, the time interval between the two peaks is necessarily longer (and not shorter!), since it represents the blood transit time between the femoral vein (cold indicator injection) and the femoral artery (a longer distance means a longer time interval). Moreover and more importantly, in both cases the time interval between the two peaks is highly dependent on cardiac output and, for instance, will be three times shorter in a patient with a cardiac output of 9 L/min than if the cardiac output is only 3 L/min. Therefore, I still believe that the “eyeball” inspection of a transpulmonary thermodilution curve does not allow the discrimination between a cross-talk phenomenon and a right-to-left intracardiac shunt. The camel curve represented in my article is now depicted in Figure 1 with a different time scale and really looks like a camel curve due to a right-to-left intracardiac shunt.2