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Medical Forum / Diseases and Disorders / Asthma / November 2006how reliable are peak flow meters?
I use a plastic peak flow meter graded from zero to 850 and find that the peak flow is constant no matter how bad/good my asthma is. I try 3 times as strong as I can and take the highest number. How big of a change can this thing detect reliably. E.g. I can imgine that I can feel a 5% drop, but the 5% is not enought to be detected by the peak flow. > I use a plastic peak flow meter graded from zero to 850 and find that > the peak flow is constant no matter how bad/good my asthma is. I try 3 > times as strong as I can and take the highest number. How big of a > change can this thing detect reliably. E.g. I can imgine that I can > feel a 5% drop, but the 5% is not enought to be detected by the peak > flow.here is an answer I got off-line: http://pediatrics.aappublications.org/cgi/content/full/105/2/354 > > I use a plastic peak flow meter graded from zero to 850 and find that > > the peak flow is constant no matter how bad/good my asthma is. I try 3 [quoted text clipped - 4 lines] > > http://pediatrics.aappublications.org/cgi/content/full/105/2/354 I found the measurements useful for my kids. Each kid has different lung capacity so you have to establish (calibrate) normal peak flow numbers for each person. Decrease from the reference peak flow is what I go by. Our pediatric pulmonary specialist gives a range of acceptable values for each kid based on charts that he has and that helps too but I go by our own regular calibration to establish reference points as they grow bigger and stronger. We also have our own stereoscope to listen to their lungs if the readings come out low. > I found the measurements useful for my kids. Each kid has different > lung capacity so you have to establish (calibrate) normal peak flow [quoted text clipped - 4 lines] > reference points as they grow bigger and stronger. We also have our > own stereoscope to listen to their lungs if the readings come out low. You know? Whenever I show the doctors my peak flow charts for the kids, it's like they want to laugh. Then, I get a lecture on how the peak flows are effort dependent, as if I shouldn't rely on it to bring DS in when he's in the red zone. I have brought him in when he was in the red zone, but he looked fine at the time because 1) I had given him two treatments two hours apart when he was having some symptoms, 2) he always looks better at the doctor's office (adrenaline kicking in), and 3) the drop precedes the symptoms and I didn't wait long enough for things to come crashing down. Hence, I get my lecture. Why do I get a peak flow meter if they don't care about the numbers? I have found it very useful for predicting DS's asthma attacks, as his peak flows decline a few days before he has symptoms. They correlate well with how he is doing, so I chart daily and we make sure he is putting in effort. I almost want to hide the charts from the doctors, though, because no one takes them seriously. Does your doctor take them seriously? Where can I find one who does? We are seeing a pediatric pulmonologist for the first time next week. I don't know if I should bring his chart, but I will. The allergist looked at me like I just wasted my time. The pediatricians don't seem to care much for it, either. > You know? Whenever I show the doctors my peak flow charts for the kids, > it's like they want to laugh. Then, I get a lecture on how the peak flows [quoted text clipped - 16 lines] > will. The allergist looked at me like I just wasted my time. The > pediatricians don't seem to care much for it, either. It is more useful for some people than others. It is effort dependant (meaning the results will vary according to how hard the person tries to blow and technique used) - unlike spirometry. Not blowing very hard can artificially lower the numbers and cheating ("spitting" the breath) can raise them. Highly inconsistent results on successive trials is one clue of poor effort or technique. It is hard to accurately reproduce poor effort or cheating but true lung function should be pretty consistent. Also, PF's measure the flow through the large airways while asthma usually is more of an issue of the medium sized airways. For most people there is a correlation but for some there is not. You are right, in the majority of people who find a correleation the peak flows will drop ahead of the symptoms. That is one reason why they can be useful. The last problem is that, despite the fact that there are published charts predicting best peak flows, there is a lot of variation. I don't find those charts to be very useful. They run a great risk of underestimating severity if the person's baseline is higher than predicted so I tend to use them (the estimates) if they correleate with symptoms but ignore them if the person is having symptoms while hitting predicted bests. It is far better to establish a baseline from when the person is feeling well. That is the biggest difficulty I find with using peak flow meters - getting the patients to use them when they feel well. Doing this would allow for a more accurate baseline and a more taylored action plan and also is more sensisitve to detecting questionable control because you can look at variability and not just major drops. I would bring the results to the visit with the pulmonologist. You can talk to him about whether the numbers are turning out to be useful. It also would be interesting to know if the pediatrician has a general disdain for peak flows (which might bring into question general knowledge and attitudes toward asthma) or just doesn't think they are worthwhile in your particular case (and why).  Signature00doc > It is more useful for some people than others. It is effort dependant > (meaning the results will vary according to how hard the person tries to > blow and technique used) - unlike spirometry. Not blowing very hard can > artificially lower the numbers and cheating ("spitting" the breath) can > raise them. Thanks for your response. DS does spit to cheat, but I can hear it and he doesn't do it anymore. Highly inconsistent results on successive trials is one clue of > poor effort or technique. It is hard to accurately reproduce poor effort > or cheating but true lung function should be pretty consistent. HIs numbers are consistent with his symptoms, and the charts are consistent. > Also, PF's measure the flow through the large airways while asthma usually > is more of an issue of the medium sized airways. For most people there is > a correlation but for some there is not. You are right, in the majority of > people who find a correleation the peak flows will drop ahead of the > symptoms. That is one reason why they can be useful. > a baseline from when the person is feeling well. That is the biggest > difficulty I find with using peak flow meters - getting the patients to > use them when they feel well. Doing this would allow for a more accurate > baseline and a more taylored action plan and also is more sensisitve to > detecting questionable control because you can look at variability and not > just major drops. We use the peak flow everyday. > I would bring the results to the visit with the pulmonologist. You can > talk to him about whether the numbers are turning out to be useful. It > also would be interesting to know if the pediatrician has a general > disdain for peak flows (which might bring into question general knowledge > and attitudes toward asthma) or just doesn't think they are worthwhile in > your particular case (and why). I'm not sure, but the allergist seems to not believe the numbers, either, and she's supposed to be our asthma specialist (but she referred us to the pulmonologist). > I'm not sure, but the allergist seems to not believe the numbers, either, > and she's supposed to be our asthma specialist (but she referred us to the > pulmonologist). Again, "why" is always a fair question. Signature00doc >> I'm not sure, but the allergist seems to not believe the numbers, either, >> and she's supposed to be our asthma specialist (but she referred us to >> the pulmonologist). > > Again, "why" is always a fair question. Why does she not believe the numbers? She said it was effort dependent, that the numbers could be down because of a cold or whatnot. She speaks about studies and such. Really, it is a general distrust of the meters, I think. That I've seen the numbers correlate for DS doesn't seem to make a difference to her, considering the studies. I'm not sure what studies, I think it's the ones comparing spirometry with peak flows? I'm sure spirometry is better, but we don't have a spirometer at home. >>> I'm not sure, but the allergist seems to not believe the numbers, >>> either, and she's supposed to be our asthma specialist (but she referred [quoted text clipped - 9 lines] > think it's the ones comparing spirometry with peak flows? I'm sure > spirometry is better, but we don't have a spirometer at home. As I have said before PF's are not for everyone. If the person does not give a consistent effort with good technique whether due to age or other factors then it won't work. This is not the case for most asthmatics - i.e most can use it correctly. As I said before there is also a group of people for whom the numbers won't correlate. However, most asthmatics can use them well and get a good correlation. The part about the colds reducing the numbers is a bit odd. That would be a real decrease in lung finction - exactly what it is supposed to do. Of course, spirometry is better and is a very useful office test if the doc has it but it is generally not available for home use. While it is important to realise that PFM's are not for everyone it is also not correct to say that they are not useful for anyone either. She may have studies that demonstrate pitfall of relying on PFM's alone but I doubt she has any that show they are generally useless. They are still recommended by the allergy and pulmonology speciality groups so her opinion, if you understand it correctly, is at best a minority. Signature00doc > As I have said before PF's are not for everyone. If the person does not > give a consistent effort with good technique whether due to age or other [quoted text clipped - 5 lines] > The part about the colds reducing the numbers is a bit odd. That would be > a real decrease in lung finction - exactly what it is supposed to do. She said that if the kids are congested, they won't try as hard. Of > course, spirometry is better and is a very useful office test if the doc > has it but it is generally not available for home use. While it is [quoted text clipped - 4 lines] > by the allergy and pulmonology speciality groups so her opinion, if you > understand it correctly, is at best a minority. She did give me back the chart to give to the pulmonologist. She never said it was completely useless, but I did get that message from her lecture and the smile on her face that said, "Aw, how sweet of you to chart, but it was a waste of time." So, no, she never actually said it was a waste of time, it was just her body language and lecture. Thanks for your input. I will bring everything to the pulmonologist. I sat up last night trying to see how much the air quality impacts his peak flows and it was "unhealthy for sensitive groups" or "unhealthy" on two of the last three times he hit the red zone. The third time he hit, there was no data. Lately, he has very high peak flows and the air quality is "good" more than it has been since I've started recording. > I sat up last night trying to see how much the air quality impacts his peak > flows and it was "unhealthy for sensitive groups" or "unhealthy" on two of > the last three times he hit the red zone. The third time he hit, there was > no data. Lately, he has very high peak flows and the air quality is "good" > more than it has been since I've started recording. What I'm about to suggest is a heck of a lot of work unless you have some programming skills but ... I have intermittent atrial fibrillation plus COPD and/or(?) emphysema. I have kept PEF and pulse records since I was first diagnosed in 1995. I wrote software to do this and to plot the results both fully and statistically smoothed to show trends. This has served me well since I have found most doctors are not very good at visualizing the picture from a page of numbers. At one point, I raised the question of whether Pulmicort was really doing much good. If it wasn't, I would prefer to avoid steroids. My doctor agreed so I tapered off over a two week period and my graphs made it instantly obvious that the Pulmicort was helping me so I re-started it. It was also suggested that I switch from Atrovent to Spiriva. Again the graphs showed that there was a little improvement and certainly no negative effects. Plotting the data you have on graph paper is a lot of work but once you get caught up, it isn't to bad to keep up. Also, I take PEF readings before I take my meds twice a day and plot the results as two traces on one graph, blue for morning and red for evening. It makes any changes _very_ obvious. Ted >> I sat up last night trying to see how much the air quality impacts his >> peak flows and it was "unhealthy for sensitive groups" or "unhealthy" on [quoted text clipped - 26 lines] > results as two traces on one graph, blue for morning and red for evening. > It makes any changes _very_ obvious. Thanks. I was in the midst of graphing this morning. I am obsessed with numbers, DH says. Graphing works for me. >>> I sat up last night trying to see how much the air quality impacts his >>> peak flows and it was "unhealthy for sensitive groups" or "unhealthy" on [quoted text clipped - 28 lines] > Thanks. I was in the midst of graphing this morning. I am obsessed with > numbers, DH says. Graphing works for me. You don't happen to have access to APL2 do you? If so I could give you my software. Ted >> Thanks. I was in the midst of graphing this morning. I am obsessed with >> numbers, DH says. Graphing works for me. > > You don't happen to have access to APL2 do you? If so I could give you my > software. I'm not sure what that is. I have been using Microsoft Works spreadsheet. It works for me. I also have My Peak Flow program. I've only been graphing peak flows, but now I've started plotting am vs. pm readings and charting the air quality and symptoms. That way, the doctors can see how well the symptoms correlate with the peak flows. >>> Thanks. I was in the midst of graphing this morning. I am obsessed with >>> numbers, DH says. Graphing works for me. [quoted text clipped - 6 lines] > the air quality and symptoms. That way, the doctors can see how well the > symptoms correlate with the peak flows. APL2 is a very powerful programming language but you seem to have something that works and that's what counts. :-) Ted >>>> Thanks. I was in the midst of graphing this morning. I am obsessed >>>> with numbers, DH says. Graphing works for me. [quoted text clipped - 9 lines] > APL2 is a very powerful programming language but you seem to have > something that works and that's what counts. :-) Hey, thanks guys. I just went to the pulmonologist and he liked the chart -- even went and made photocopies. His plan is to throw everything but the kitchen sink at this and see if it works, then peel back slowly on the treatments until we have the minimum number of drugs necessary to treat. If it doesn't work at all, then he'll dig deeper. I'm willing to try it at this point. If it works, great. I'd rather not be too invasive, if it's not necessary. > Hey, thanks guys. I just went to the pulmonologist and he > liked the chart -- even went and made photocopies. His plan is > to throw everything but the kitchen sink at this and see if it > works, then peel back slowly on the treatments until we have > the minimum number of drugs necessary to treat. Isn't this doing it backwards? If you're taking a lot of medication, how will you know what's working and what's not working? And if you have a reaction, how will you know what's causing it? Do you then stop taking everything? I've never heard of this before. Or am I misinterpreting what you mean? >> Hey, thanks guys. I just went to the pulmonologist and he liked the >> chart -- even went and made photocopies. His plan is to throw everything [quoted text clipped - 6 lines] > reaction, how will you know what's causing it? Do you then stop taking > everything? We were doing it the other way around all these years and it hasn't worked. The doc's reasoning is to first get the inflammation under control. Then, we will peel back slowly. I understand we will peel back one med at a time. If asthma worsens, we put it back and peel another one off until we get the minimum number of meds. sorry i didn't get back to your question re:specialist referral sooner. i only check the threads once a month or so. sounds like it's working ok for you. we went through the same thing when the kids were small and slowly took them off meds. now sigulair is all they need and they keep a puffer with them plus epipen at school's nurses office. some times there is no choice but to work backwards for the small kids because you can't take the risk of taking them off. our specialist has a computer setup with breathing instruments hooked up digitally and the kids cycle through a test routine every six months or so during the period when we were reducing meds. kids are down to one attack per two years now (maybe even less) instead of 2 per year several years back so we don't even have to run the computer tests anymore. > >> Hey, thanks guys. I just went to the pulmonologist and he liked the > >> chart -- even went and made photocopies. His plan is to throw everything [quoted text clipped - 12 lines] > If asthma worsens, we put it back and peel another one off until we get the > minimum number of meds. |
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