Hemoptysis and Munchausen syndrome.

ences in gastric wall and arterial blood bicarbonate in the first 120 min of peritonitis, and this is what we found and what we reported. Though we have some difficulty with the focus of your letter, it remains that this paper does not assail the use of tonometry but presents only direct measurements. Our data are in no way contradictory of your comments regarding gastric mucosal pH and your graphics. In fact, we have gone one step further and calculated the gastric mucosal pH as directly measured, as computed from tissue bicarbonate, and computed from arterial bicarbonate (enclosed). These are to some extent artifactual, of course, since tissue bicarbonate was derived from measured gastric wall pH and Pco2. Nevertheless, neither graph proves other than that in the first 2 h there are differences related to the estimate of bicarbonate. Whether these differences are of clinical importance is entirely contingent on the clinical circumstance. To this extent, we believe you are in error in assuming that tissue and venous Pco2 would predictably vary with arterial Pco2. That applies if the animal or the patient is breathing spontaneously and when the ventilation/perfusion ratio is decreased because cardiac output and pulmonary blood flow are decreased. It is not obtained when the patient fails to ventilate, and there is a progressive increase in arterial Pco2 or in settings of septic shock when cardiac output is increased or normal. Therefore, I'm not sure that as a general rule you would want to always rely on the gradient between stomach wall and arterial Pco2 to refine tonometry measurements. Both septic rats and control rats were anesthetized for intervals exceeding 4 h. By definition, such controls are used because of the very fact that there are issues of stability of the preparation that included minor reductions in cardiac output and therefore minor increases in arterial blood lactate and decreases in PaCO2. The paper supported the concepts underlying tonometry, especially with respect to PaCO2.