Positive end-expiratory pressure (PEEP) level to prevent expiratory flow limitation during cardiac surgery: study protocol for a randomized clinical trial (EFLcore study)

Abstract

Background: Lung dysfunction commonly occurs after cardiopulmonary bypass (CPB). Randomized evidence suggests that the presence of expiratory flow limitation (EFL) in major abdominal surgery is associated with postoperative pulmonary complications. Appropriate lung recruitment and a correctly set positive end-expiratory pressure (PEEP) level may prevent EFL. According to the available data in the literature, an adequate ventilation strategy during cardiac surgery is not provided. The aim of this study is to assess whether a mechanical ventilation strategy based on optimal lung recruitment with a best PEEP before and after CPB and with a continuous positive airway pressure (CPAP) during CPB would reduce the incidence of respiratory complications after cardiac surgery.

Methods/design: This will be a single-center, single-blind, parallel-group, randomized controlled trial. Using a 2-by-2 factorial design, high-risk adult patients undergoing elective cardiac surgery will be randomly assigned to receive either a best PEEP (calculated with a PEEP test) or zero PEEP before and after CPB and CPAP (equal to the best PEEP) or no ventilation (patient disconnected from the circuit) during CPB. The primary endpoint will be a composite endpoint of the incidence of EFL after the weaning from CPB and postoperative pulmonary complications.

Discussion: This study will help to establish a correct ventilatory strategy before, after, and during CPB. The main purpose is to establish if a ventilation based on a simple and feasible respiratory test may preserve lung function in cardiac surgery.

Trial registration: ClinicalTrials.gov, ID: NCT02633423 . Registered on 6 December 2017.

Keywords: Protective ventilation, Cardiopulmonary bypass, Respiratory failure, Low tidal volume, Continuous positive airway pressure, Postoperative pulmonary complications.

Conflict of interest statement

Ethics approval and consent to participate

In order to obtain Ethics Committee approval, documentation was submitted in December 2017 to the San Raffaele Hospital Ethics Committee (N approv) and we are currently waiting for approval.

All patients will give their informed consent to participate to this study. A trained researcher will collect the informed consent documents.

Consent for publication

All patients gave their informed consent to the publication of clinical data. A trained researcher will collect the informed consent documents.

Competing interests

The authors declare that they have no competing interests.

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Figures

Fig. 1

The Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) Figure of this trial

Fig. 2

The trial flowchart. Description of the ventilatory strategies and allocation of patients before, during, and after cardiopulmonary bypass

Fig. 3

The PEEP test. Flow-volume loops of patients undergoing positive end-expiratory pressure (PEEP) test. a Subtraction of 3 cmH2O of PEEP in this cohort of patients leads to an increase of expiratory flow: these patients are classified as not flow-limited. b Subtraction of 3 cmH2O of PEEP does not increase expiratory flow, except for a brief, initial, transient increase, which is mainly the result of a sudden reduction of volume of the upper airways and denotes flow limitation. See text for further explanations