Inhibition of Plasma Kallikrein as a New Therapy for Lung Injury

Inclusion Criteria: * Age \>18 years admitted to the ICU with primary diagnosis of lung injury. The criteria for the diagnosis of lung injury include five principal elements: hypoxemia (blood oxygen saturation (PaO2) ≤92% when breathing ambient air, ratio of PaO2 to the fraction of inspired oxygen (FiO2) ≤300), diffuse pulmonary infiltrates on chest radiographs, decreased lung compliance, and the absence of congestive heart failure. * Both males and females will be recruited in the proportion in which they are admitted to the ICU with lung injury. * Arterial cannula in place as part of usual care for the measurement of blood gases. * Patients may or may not be intubated and mechanically ventilated. * Able to provide informed consent, or if unable to do so, a responsible person: medical treatment decision maker is available (by telephone if necessary) who can be approached to seek consent. Exclusion Criteria: * Other causes of lung infiltrates: pulmonary oedema, alveolar haemorrhage, adverse drug reactions, radiation injury and the idiopathic pneumonitis syndrome. * Significant dysfunction of non-pulmonary organs in the opinion of the treating ICU consultant. * Death is deemed imminent or inevitable or there is underlying disease with a life expectancy of less than 90 days. * Previously enrolled in this study. * Enrolled in another study. * Usually receives home oxygen. * Usually receives any type of assisted ventilation at home. e.g. continuous positive airway pressure for obstructive sleep apnoea. * Pregnant or might be pregnant. Women aged 18 to 49 are excluded unless there is documented menopause, hysterectomy or surgical sterilisation, or a pregnancy test is negative. * Objection from the treating clinician. * Consent refused by the patient or substitute decision maker.