121. Cyanosis unresponsive to oxygen in the nondistressed patient: ddx / Criteria to discharge methemaglobinemia patient October 25th, 2007 by reuben in .cyanosis Back Top Tags: card 120. Pulse ox in methemaglobinemia / Tests in the cyanotic patient 122. When is cyanosis visible? / What causes a left shift in the hemoglobin-oxygen dissociation curve? Leave a Reply Cancel reply Please post any discussion to the emupdates Reddit page.