 In Part B, 60 subjects will be randomized to 1 of 3 treatment groups in a 1:1:1 ratio with 20 subjects in each treatment group. Subjects assigned to an iNO group will receive pulsed iNO at either 0.030 mgkg IBWhr or 0.075 mgkg IBWhr, with a set PW of 260 ms. Part B subjects assigned to placebo will receive N2 at a randomly assigned device setting of 0.030 mgkg IBWhr or 0.075 mgkg IBWhr with a set PW of 260 ms. 