I suffered anxiety attacks after I left the Marines in 1975. One tour in 'Nam and two tours with Operation Plowshare had put me to the limits of adrenal extremes more than once. Here is my experience, and I hope it helps.
Anxiety/panic attacks are a life threatening disorder. Only personnel specially trained in dealing with this medical/psychological condition should attempt intervention. Few ambulance crews have this training: it occurs only in combat veterans and police officers who have experienced repetitive life-threatening situations where violence is the only answer.
1. Normal life. Pulse 60, 120/80 bp, feeling at rest. Life is good.
2. Trigger. Some unwanted and repetitive reminder of a situation where an instant fight-or-flight response made the difference between life and death. 10-15% adrenal reaction. Pulse 75, 130/90 bp. Can be as mild as a call from an old friend who insists on blathering about his days in combat (best forgotten) or a scene on TV showing full-auto fire in a staged presentation. It takes a half-hour to restore calm. No medical intervntion required or desirable.
3. Trigger/reminder. The combination of an environmental trigger and a verbal reminder of a stressful situation can start a 10-35% adrenal reaction. Fight-or-flight reaction is a very present issue, and it is necessary to "break" with the situation or face a full-blown anxiety attack. The absolute worst thing that can happen is some idiot tries to get you to calm down, or threatens a physical restraint. A very critical time. This is otherwise called "jungle nerves" and an hour or two at this level of stress can precipitate a "thousand-yard stare." Again, let the stressed out person regain calm on his own: do not attempt intervention.
4. Trigger/reminder/actual threat. 100% adrenal reaction, pulse 120-170, bp 160+/120+. It becomes impossible to tell a perceived threat from a genuine threat as during a military counterattack. Spiralling bp/pulse can result in myocardial infarction. Physical strength becomes "superhuman," muscles become hard as pine boards, reflexes become uncontrollable. Using such phrases as "calm down" are a certain provocation and shall result in fight-or-flight. Medical intervention is now necessary, but let the attack run its course.
5. Post-arousal exhaustion. Pulse 170+, BP off the scale, cold skin, unable to move, death seems greatly preferable to another anxiety/panic attack. It is a life-threatening disorder and only beta-blockers by inhalation will reduce the attack.
It is as much a physical disorder as a delayed reaction to an overwhelming environmental stress that puts the safety of the victim and others in question.
The main hope of a PTSD victim is never to have to endure that sort of arousal again, at least until he can come to grips with it on his own terms.