Tuesday, January 26, 2010

Peak flows

From what I can remember, peak flows were not used as part of any asthma action plan when I was a kid. Basically, they were used to monitor the course of an asthmatics lung volumes over time. They were also used before and after breathing treatments to determine effectiveness of therapy.

My doctors and respiratory therapists had me use them, and always encouraged me to use them at home, yet I rarely did. When I was at the asthma hospital I blew into a peak flow three times a day and recorded the results. During the last three months at the asthma hospital, I monitored peak flows and I blew into a spirometer twice daily and monitored these results too.

When I was discharged, however, I do not remember any mention of me monitoring my peak flow results to help me determine (based on downward trends) if I should take my rescue medicine, or call my doctor, or get my lungs to the ER. If I remember right, no such asthma action plan existed back the. However, my memory may not serve me right.

I was however, taught to learn my signs and symptoms of asthma, and to use these to determine if I should use my rescue inhaler, let my parents know, or call my doctor. Trending down peak flows was not listed as a symptom. I have the list of symptoms, and it's not on it.

I think the asthma action plan as we know it today was started around 1997 or so when the first Asthma Guidelines were released. Still, I could be wrong.

Regardless, when I was a kid my peak flow number rose and fell based on how well my lungs were doing, and monitoring them would have been an ideal way for me to determine how to treat myself. As an adult, however, I find that my peak flows are the same (between 600 and 650) regardless of how well I feel.

As a matter of fact, when my asthma was so bad in 1998 that I was admitted for 10 days for it, my peak flows were still between 650 and 700. Now how I could be short of breath and still have my peak flows being normal was and still is beyond me. My doctor was perplexed by this too.

And while those Q1 hour breathing treatments provided me relief (yes, that's what it took for up to four days before I caught my breath), my pre and post peak flows still never changed.

So, while I blow in my peak flows and record the results from time to time just in case they decide to tank, I'm unable to use peak flows as part of my asthma action plan. I therefore have no choice but to use symptom monitoring.

In the course of being an RT I have, however, encountered a few asthmatics similar to me, where peak flows were relevant as a kid and yet irrelevant as an adult. In fact, I had such a patient just the other day.

I do have a theory for this. In fact I read this somewhere. It's that the degree of chronic inflammation was the same in my childhood lungs as my adult lungs, yet my childhood lungs were smaller and more sensitive to my asthma triggers, and thus more brittle. My larger adult lungs are less sensitive to my asthma triggers, and less brittle.

Likewise, even during one of my adult flares, the degree of "obstruction" may cause me to feel dyspneic, but doesn't block my airways as bad as they did when I was a kid with smaller airways.

I have no evidence here, but I THINK this (airways getting larger as we grow older) is why asthma quite often seems to disappear as asthmatics get older. Well, at least this is one of the reasons. The other is, as we get older, we are removed from asthma triggers, and thus our asthma becomes so mild we barely know we have it (of course that's a discussion for another day).

So while I continue to teach my asthmatic patients about the importance of peak flows, and while I do pre and post bronchodilator peak flows on all my asthmatic patients, they really serve no purpose for me.

However, just in case, I do blow into one from time to time just for fun. Or, perhaps I do it just in case I'm wrong. I am wrong from time to time. If you don't believe me, just ask my wife.

1 comment:

  1. I also can have high peak flows while still being symptomatic. Also my peak flow and FEV1 can be wildly different (e.g. 96% PEFR, 67% FEV1).

    I attribute it to the fact that a peak flow requires only a momentary maximal push to push that lever as high as it can go, whereas symptom free breathing requires being to sustain that effort over a long period of time. Quite a different matter.