<prompt> Flat capnogram found in AEDisconnection of anesthetic tubingAccidental extubationMechanical ventilation failureBronchospasm  <response>: All the four options given in the question can cause flat Capnography. But, bronchospasm is the single best answer here as only severe bronchospasm causing complete respiratory obstruction can cause a flat capnograph. However, bronchoconstriction is usually partial which causes a steep plateau in capnograph not flat capnograph.A flat capnograph is seen in accidental extubation, equipment failure, disconnection dissociation of a tube, total occlusion, mechanical ventilation failure, cardiac arrest, severe bronchospasm completely obstructing the airway and complete occlusion of pulmonary circulation. 