Difficult airway is defined as situation that face mask ventilation, laryngoscopy, or intubation Cannot be done by clinician as easy as he expects where it. Difficulties in children airway management do not occur frequently and aggressive airway management in children is not required often.We present a case of "Cannot ventilate, Cannot intubate" scenario in a five years old girl with a supraglottic cyst in operating room. We started to sedate the patient with ketamine for awake intubation but the cyst obstructed the airway and we couldn’t ventilate her with mask. Two try of intubation with tube and bougie were failed and rigid bronchoscope could maintain the airway finally.

Background: Cytoglobin (Cygb) is a relatively newly identified globin protein that acts as an oxygen transporter in tissues like hemoglobin (Hb) in erythrocytes and myoglobin (Mb) in muscles. The natural oxidation of the Fe2+ ion in its heme group into metglobin (globin-Fe3+) made the loses of oxygen binding functions. It is known metHb and metMb can be reduced enzymatically using diaphorase or cyb5r3. However, metCygb reductase had not been previously identified. This study aims to analyze the reducing activity of bovine diaphorase on metCygb. Methods: Diaphorase was isolated from bovine erythrocyte and purified using gel filtration and cationicexchanger chromatography. Its purity was verified by SDS-PAGE and western blot (WB). The metCygb was obtained from Cygb oxidation with potassium ferrocyanide and its reducing activity was determined by spectroscopy. Results: The diaphorase (MW=30. 09 kDa) was purified 10. 77-fold from crude enzyme with specific activity against metHb 8. 479 U/mg. The purity was confirmed by WB using primary antibody anti-cyb5r3. The purified enzyme reduced metCygb at 0. 785 μ, gmin-1, which was 13. 7 times less than the Vmax of metHb. Conclusions: In conclusion, the purified diaphorase from bovine erythrocytes did not significantly reduce metCygb rather than metHb, a natural substrate in cells.