Subcutaneous emphysema, including preperitoneal emphysema, and organ emphysema such as insertion of gas into the tissue planes of the omentum, are all considered under this heading. The occurrence of subcutaneous emphysema may not manifest itself until later during a long laparoscopic operation. Insufflation of the preperitoneal space or of the omentum will be immediately apparent on initial laparoscopic exploration. These latter two problems become issues only if they prevent the ability of the surgical team to safely visualize the organs in the operative field. In this case, the operation may need to be converted to an open incision, delayed while the CO2 gas is absorbed, or cancelled. Rarely do further complications occur. In the case of subcutaneous emphysema, the increased CO2 load to the patient's system can result in systemic acidosis. This may not be apparent simply from the measurement of end-tidal CO2 on the ventilator, which will be elevated as a result of the emphysema but may remain static although elevated. In patients with preexisting cardiopulmonary disease, inability to process the excess CO2 that is absorbed may lead to a systemic acidosis with resultant hemodynamic and metabolic complications.