What does severe asthma look like in a capnography?

"Shark Fin": Asthma is an obstructive airway disease that causes bronchospasm. This condition will produce a “shark fin” capnography waveform due to difficulty emptying alveoli. Characteristic "shark fin" appearance is a result of obstruction which causes turbulent mixing of dead space air with alveolar air. This mixing softens the rapid rise in CO2 concentration of exhaled air.

Great question.: Initially your pco2 will decrease since you are hyperventilating. This will cause your ph to increase. As your air trapping gets worse and your muscle fatigue your pco2 will be normal. This is when you will have impending respiratory failure and will need support very soon. You will have a normal ph at this time and people get fooled. Respiratory arrest is close and you will need life support.