What has given this appearance?
There is a large volume of free gas under the diaphragm displacing and compressing organs. This is tension pneumoperitoneum.
Why would there be a reduced cardiac output in this patient?
There will be not only positive pressure in the thoracic cavity impeding cardiac output, but the inferior vena cava will also be compressed reducing venous return.
Significant pneumoperitoneum with displacement of diaphragm, abdominal organs and compression of thoracic structures.