What is the first action to take for a patient on O2 who starts convulsing?

In the scenario where a patient on oxygen begins convulsing, the appropriate first action is to remove the oxygen mask. During a convulsion, there is a risk of the patient inadvertently inhaling foreign substances or causing an obstruction to their own airway. Keeping the oxygen mask on could lead to suffocation if the patient is unable to breathe properly during the seizure. By removing the mask, you can ensure that the patient's airway is not compromised and that they can breathe freely.

Once the patient is stable, other actions such as calling for emergency help may follow, but the immediate priority is addressing any potential risk to the patient's airway caused by the seizure activity. This approach emphasizes safety and proper care in a high-stress situation where immediate action is necessary.