Phase I Trial of Inhaled Nitric Oxide to Treat Acute Pulmonary Embolism

We propose to enroll a total of 25 patients with recently diagnosed pulmonary embolism. Inclusion criteria will include moderate to severe shortness of breath as rated by the patient on a standard scoring system, a systolic blood pressure of \>89 mm Hg unless the patient has a known prior history of low blood pressure, and blood oxygen saturation of \>80%. Exclusion criteria will include: altered mental status, inability to use a nasal cannula, a large need for supplemental oxygen, pregnancy, pneumothorax, recent use of nitrate-containing medications, recent use of thrombolytic drugs, requirement for inotropic or pressor support, or a level of methemoglobin greater than 10%. After obtaining informed consent, subjects will have blood drawn and vital signs will be obtained. They will subsequently begin to breathe oxygen and NO supplied through a nasal cannula delivered from the iNOvent device. The patients will undergo serial measurements of their blood pressure, arterial oxygen saturation and will have their serum methemoglobin level monitored via a non-invasive probe. Titration of the amount of NO delivered will be made periodically based on the patient's vital signs. If an absolute safety endpoint is reached, NO will be rapidly weaned. Based on the patient's response to NO as determined by their vital signs, a maintenance dose of NO, not to exceed 25 ppm, will be reached. Subjects will continue to receive this concentration for up to 2 hours prior to weaning. Patients will be asked once more to rate the severity of their shortness of breath and blood will be drawn just prior to weaning. Should the patient reach a safety endpoint, the NO will be weaned at an earlier timepoint. We will determine the percentage of patients able to complete the full protocol without reaching a safety endpoint, the percent change in methemoglobin level, the trend in patient-reported shortness of breath, percent change in SBP and oxygen saturation and the number of patients who withdraw during induction for any reason.