 In Part A, 80 subjects will be randomized to 1of 4 treatment groups in a 1:1:1:1 ratio with 20 subjects in each treatment group. Subjects assigned to an iNO group will receive pulsed iNO at a dose of 0.003 mgkg IBWhr, 0.010 mgkg IBWhr, or 0.015 mgkg IBWhr, with a set pulse width PW of 260 milliseconds ms. Part A subjects assigned to the placebo group will receive nitrogen N2 at a randomly assigned device setting of 0.003, 0.010 or 0.015 mgkg IBWhr with a set PW of 260 ms. 