For most data added to the Cambridge Structural Database (CSD), the information on the pressure at which the structure was collected will have been obtained from the CIF field _diffrn_ambient_pressure (see https://www.iucr.org/__data/iucr/cifdic_html/1/cif_core.dic/Idiffrn_ambient_pressure.html).
As part of the data curation process at the CCDC, efforts are made to standardise the data given in the deposited CIF to the units GPa, and to exclude cases where ambient pressure has been recorded in this field. The data curation process may also find cases where pressure information is given in the publication and missing from the deposited CIF.
CSD entries at high pressures can be therefore be found using ConQuest by performing an All Text search with 'Pressure' as a Required Field (from the 'Required Field' tab of the All Text query pane). The pressure values can also be found using the CSD Python API using the entry.pressure attribute.