Introduction Procalcitonin (PCT) is activated during cardiopulmonary bypass (CPB) and may be a predictor of acute respiratory distress syndrome (ARDS). The objective of this study is to determine whether patients with different serum PCT concentrations exhibit different rates of developing moderate to severe ARDS.

Methods and analysis This is a prospective, single centre, observational cohort study. All patients admitted to the cardiosurgery department for cardiac surgery with CPB were screened for study eligibility. All eligible patients received a CPB procedure. Blood samples were obtained to determine white cell counts as well as N-terminal pro-B-type natriuretic peptide, C reactive protein and PCT levels. Patients were assigned to the PCT elevated cohort or the control cohort based on serum PCT concentrations on the first postoperative day with a cut-off value of 7.0 ng/mL. Data, including baseline, perioperative and outcome data, were collected daily for 7 days. The primary end point was the incidence of moderate to severe ARDS, which was diagnosed according to the Berlin definition.

Ethics and dissemination The study was approved by the Institutional Review Board of Fujian Provincial Hospital. Study findings are disseminated through peer-reviewed publications and conference presentations.

Study registration Chinese Clinical Trial Registry (ChiCTR-OCH-14005076).