Answer: Thanks for your question. We are not entirely sure if we understand your question.
In the Basic Life Support Patient Care Standards (BLS-PCS) Section 1- General Standards of Care page 1-6 it states that the secondary survey physical assessment (which includes initial vital signs) should generally be completed within 5min or less. Following this, if the patient meets the indications and conditions for the Cardiac Ischemia Medical Directive then a paramedic may provide the treatment prescribed in this medical directive if certified and authorized.
You are correct that since the dosing interval for NTG is every 5min, a repeat set of vital signs are required prior to repeat administration.
As for your comment surrounding deactivations resulting from a time gap of 3min from vital signs prior to NTG, we have no knowledge of this nor would we support this position.
We believe that paramedics should assess patients as per the BLS-PCS, make a treatment decision, follow their medical directives where appropriate, and make a transport decision. The SWORBHP Medical Council does not support micro-managing paramedic scene management as long as patient care remains priority based and timely.