Central cyanosis is seen if: (A) Methemoglobin 0.5 gm/dl, (B) O2 saturation < 85%, (C) O2 saturation < 94%, (D) Hb – 4 gm%
Answer is B. Oxygen saturation should be less than 85% for central cyanosis to occur. Deoxyhemoglobin level should be at least 5gm%.