A noninvasive, flexible sleeve intended to be used during pulmonary artery catheterization to cover and protect the exposed proximal end of a pulmonary artery catheter to prevent contamination (extending the sterile field of the external catheter) and/or to contain a backflow of blood (e.g., during catheter introduction, repositioning or removal). It is typically transparent, made of synthetic polymers, and includes appropriate connectors for distal attachment to the catheter introducer, and proximal attachment to the extracorporeal portion of the catheter. Neither the catheter nor introduction/procedural devices are included (i.e., not a set). This is a single-use device.