After target pulmonary hypertension had been achieved and stabilized for at least 20 min, hemodynamic measurements were made and blood samples were obtained for NO2− measurement. Animals were then treated with placebo (n = 4), DETA/NO (n = 4), or DPTA/NO (n = 4) aerosol. DETA/NO and DPTA/NO (60 μmol; Sigma Chemical; St. Louis, MO) solutions (12 mM) were freshly prepared by dissolving each drug in 5 mL of phosphate buffer (WA Hospital Central Pharmaceutical Manufacturing Facility) [pH 7.4] immediately before inhalation therapy. The dose used in this study was derived from the data of Cornfield et al,13 adjusted for body weight. Normal saline, DETA/NO, or DPTA/NO solutions were aerosolized into the respiratory tract via a Sidestream Jet Nebuliser (Medic-Aid; West Sussex, UK) driven by 100% oxygen at a flow rate of 2 to 3 L/min. Aerosols were delivered into the lungs over 20 min by connecting the nebulizer to the inspiratory limb of the breathing circuit. Hemodynamic measurements were repeated at 5, 10, 15, 20, 25, 30, 45, 60, 75, 90, 105, 120, 180, and 240 min after aerosol therapy was commenced. Further blood samples for NO2− measurement were collected at 15, 30, 45, 60, 75, 90, 180, and 240 min. Piglets were killed with IV pentobarbitone at the end of study.