If his care team has placed him in a prone position while on the ventilator, it is most likely due to the fact that he has significant issues with oxygenation. Prone positioning does not have any effects on clotting. That is, the ability for oxygen to enter his body via his lungs is significantly impaired due to damage in his lungs. What that damage is from is difficult to say at this point without knowing the full details but most commonly in these circumstances, it is due to one of two things (both of which can occur at the same time). The first is a marked amount of fluid build-up in the lungs due to a failing/injured heart. When the heart cannot beat efficiently (notably the left side of the heart), fluid backs up into the pulmonary vasculature and then spills into the lung tissue itself. The second is aspiration. During a resuscitation, it is not uncommon for patients to aspirate gastric secretions/vomit into their airway and lungs. This can kick of a storm of inflammation in the lungs as well as even a pneumonia and subsequently compromise oxygenation. Overall, if the lung injury is severe enough, resulting effects can cause other organ systems to be injured/fail (notably the kidneys).
Ventilator management of patients with these types of issues can be tricky but any potential harm delivered by the ventilator (and appropriate settings by an experienced care team can minimize this harm) is far outweighed by the benefit provided by the ventilator (getting oxygen in and carbon dioxide out).
It is unlikely that his current lung issue is driven by any form of pneumothorax (hole punctured in the lung) as that is (usually) easily solved with a (or a few) chest tubes and if you subsequently have a pneumothorax with chest tubes in place, we really do not then put you into prone positioning.
It's not uncommon for folks who have a cardiac arrest and are resuscitated to then have another arrest given all of the damage that the body subsequently gets exposed to as a result of the initial arrest and lack of perfusion. As an example, high levels of acid can build up which can predispose to another arrest as can recurrent abnormal heart rhythms.
At this point, based on everything that has been shared in this thread (and it's really the only place I've been looking at for updates so I apologize if I have missed something), Damar would appear to have multiorgan system dysfunction/failure (CNS, Cardiac, Pulmonary). This is a difficult position to be in.
