In Reply.—We have no catheterization data on pulmonary hypertension in patients with CF prior to the onset of overt right-sided heart failure and thus are unable to evaluate any treatment measures at this stage of the disease. Long-term controlled studies of many moderately involved patients with CF would be necessary and, to our knowledge, this type of information will not be available for many years.
With regard to the questions concerning Pv̄o2, all of our patients had abnormal values (<34 mm Hg) and all also had arterial Po2 below 50 mm Hg. In this group, therefore, we are unable to comment on the relationship between a variety of arterial Po2 values and the Pv̄o2. A preliminary examination of nPv̄o2 data in our patients (analyzable data are available on 25 of the 31 patients catheterized) does not suggest a clear indication of a relationship with survival.