The purpose of this study is to determine whether giving inhaled nitric oxide to adults with acute respiratory distress syndrome (ARDS) who have developed pulmonary hypertension (elevated blood pressure in the blood vessels of the lungs) increases the likelihood that their condition will improve. Currently, there is no specific treatment for pulmonary hypertension that results from ARDS. Researchers want to learn whether the use of inhaled nitric oxide can improve pulmonary hypertension and thus improve the ability of other organs to work better. Participants will undergo an echocardiogram before taking inhaled nitric oxide and on days 2 and 4 of the study. Medical information, including vital signs and medications, will also be recorded. The use of inhaled nitric oxide to specifically target pulmonary hypertension in ARDS, as in this study, is investigational, although nitric oxide is frequently used for ARDS.