In the study by Haas et al.3 the patients who received Pentoxifylline had a mean Hb saturation of oxygen of 92.8% with a range of 89 to 96%, while in our study, the mean Hb saturation of oxygen was 87.5% with a range of 83 to 91% with pulmonary hypertension; consequently, failure of Pentoxifylline to improve oxygenation and 6-minute walk distance in our COPD patients may have been caused by the recruitment of previously unrecruited capillaries as a result of hypoxemia. The gene discussed is GSTM1; the disease is pulmonary arterial hypertension.