<prompt> Cyanosis NOT improving with 100 oxygen in case of:Cardiac AsthmaInterstitial lung diseaseBronchial asthmaTetralogy of Fallot TOF  <response>: Answer is D Tetralogy of Fallot TOF: Presence of cyanosis that does not improve with supplemental oxygen suggest true pathological cardiac or pulmonary shunting of blood. Presence of a cyanotic hea disease with an active right to left shunt Tetralogy of Fallot is a characteristic cause for failure of improvement with 100 oxygen supplementation. This occurs because desaturated blood in TOF shunts directly from the right deoxygenated side of the hea to the left side systemic of the hea by passing the lungs where oxygenation occurs. 