Pulmonary Hypertension (PPH) and Diet Drugs

One unexpected aspect of Fen Phen drug has been dramatic increase in Pulmonary Hypertension. Apparently pulmonary hypertension is caused by changes in the blood vessels in the lungs. These blood vessels produce complicated chemical compounds. In some people, a chemical called endothelin which causes these blood vessels to constrict is overproduced. Of course the restriction in blood vessels gives rises to increase in blood pressure which is one of the symptoms of the disease.

Perhaps slow breathing in some way influences the chemical compound production by these cells in the lung. I wonder if resperate exercise might not be helpful to pulmonary hypertension patients.
The disease might also give us another window in possible effects of slow breathing exercises. Changes in breathing may stimulate these cells to produce less or more of chemical compounds even in healthy normal people and may therefore have effect on BP.