Air carrier First Officer reported CO2 poisoning during preflight due to the lack of airflow during preflight with dry ice supplemental procedures in effect. The flight crew was transported to a hospital for medical evaluation.

Narrative

While performing preflight duties we were notified via ACARS that were being dispatched using Maintenance Dry Ice Supplemental procedures in Effect. We reviewed and executed the QRH procedures for Dry Ice Supplemental Procedures - Ground. We also reviewed the De-icing and Anti-Icing QRH procedure and discussed the threats associated with both. We agreed to monitor the Drager Monitors and our own physiological conditions for the effects of CO2. We agreed to use 100% oxygen if we started having symptoms. At some point in the De-ice / Anti-ice process the Drager alerts went off. We reviewed our condition and agreed to use 100% if we started to have symptoms. I announced I wasn't feeling well and started to identify the symptoms I was feeling. The Drager monitor levels continued to rise. We both went on 100% oxygen. We queried the ice-man to ask how much longer they had in the de-ice process. They responded they were almost done. I expressed concern my symptoms were not improving and worsening. We determined the safest course of action was increase airflow to the cockpit and remove ourselves from the environment. We opened both windows and the main cabin door to increase airflow to the cockpit. We requested stairs be brought to the airplane immediately and de-ice process be terminated. The station asked if we required medical attention and in the interest of safety I responded yes. We exited the aircraft and met medical personnel inside. It was determined that I needed to be brought to the hospital for further evaluation. With full support of the Duty Officer and Captain; I was transported to the hospital and evaluated.CO2 poisoning due to lack of airflow IAW de-ice procedures with dry-ice supplemental procedure in place.Not allow dry-Ice supplemental procedures when weather requires de-ice or any other situation where the air flow is required to be shut off.