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How does Peak Flow work?


I'm apparently diagnosed with Asthma, or that's currently what Doctors think is wrong with me. I am getting un convinced.. but hopefully some of these questions will help me to understand asthma (if that's what it is) or decide it's not and go back to a doctor.

So, the first thing is please can someone explain Peak Flow? I started doing it from a doctor when they were going through diagnosing me. I started with a blue inhaler, then went back to a doctor and had to do peak flow, then got a red/brown inhaler and went back 4 weeks later. They decided then that I had asthma, and the doctor was then rather unhelpful and just said 'carry on using the 2 inhalers' and, that I did not need to do peak flow anymore.

I got a cold/chest infection a while later, and thinking it was just a cold, never even used my blue inhaler. I had about a week of not sleeping, couching up slime. Tried my blue inhaler being so desperate, had a massive difference and ended up seeing a nurse the next day. They were so much more helpful than the Doctor, I got a peak flow booklet with questions in to fill in daily, and they increased the dose of the red/brown inhaler while I had the cold. 2 weeks after that I had to have a routine appointment with the main asthma nurse, who kept the increased dose of the red inhaler, just changed the times of day to help me in the evenings. I was noticing from about 6pm onwards until my night does I was struggling to breathe or coughing. They changed it so I now take 1 puff at about 5pm and 1 puff before I go to sleep which really helped. They also said to use the blue inhaler when I know I am about to do exercise. And I need to go back in 3 months. (or sooner if I need to) This appointment was 2 weeks ago, so I am now 2 weeks thorough 3 months.

All that time my peak flow has been a really wiggly line, can be well anywhere between about 300 and 440 most of the time. I don't really understand, I took the booklet and all the past charts to the nurse, she did not seem to think that it was a problem, or really say anything about it.

Last week is when I started to have problems. I was away with sea cadets staying in a old warship on a navel base which obviously involves lots more walking to everywhere than I do usually, and I had to march to breakfast and evening meals. That's before I even then do the day's activities! From the first walk from the coach to the ship (carrying my bag of clothing) I was having problems.. just simply walking down a ramp then up some stairs I could not breath.. The rest of the week when the same way. The 2nd day I got the highest peak flow I have ever had 460.. What I really do not understand is how the week when I am having so much time I can't breathe, and using my blue inhaler a lot does my peak flow get higher. I thought it got lower when I am struggling. My only possibly thought is using the blue inhaler makes it higher? What am I doing wrong? or what should happen? Basically I am really confused.

Yes, the day I had a bigger attack? (I think, I still do not really understand what the word 'attack' actually means) yes it was a lot lower that night. But the next morning it was fine and then wiggly again.

Now I have realised this is quite long, so I will leave it with just the issue of peak flow, then either add other questions at the bottom, or make new posts. I am not trying to make super long posts so no-one reads them and replies. But, I thank anyone who has read it all, and anyone who replies.

Thank you

3 Replies

Hi and welcome?!

Peak flow is a bit complicated some people can be really struggling and still do a good blow dont know how but generally it shows the dr how good is your asthma control the more wiggly it gets the less control you got the aim is to keep it in the well zone all the time so for you if your best was 460 then you calculate 80% of it which is about 370 so if your peak flow gets worse than that you need to use your blue inhaler and if gets to 50% thats when its time for hossie. You should ask your nurse or dr to give you the exact numbers for you as i cannot tell them as i am not a dr . Like my best is 450 but if it falls to 230 must go to hossie or if it falls to 310 must take steroids tablets and see the dr . So its quite important! Hope that this explains thing a little?

Any more questions dont be afraid to ask ?


Hello Yas

Thank you for reading and replying.

I think that i am having that, I am struggling and somehow get good results. The first nurse I saw said to go back if it got to 50 below whatever I blew that night on my machine at home. That night it was 410, so, that would mean go back when it gets to 360 which it has not ever done since. It's been between 380 and 470 are the lowest and highest.

You said about it being wiggly? is that good or bad? Mine's quite wiggly, as you can see above, that is a difference of 90 in between 4 weeks. I'm guessing that is quite a mix? Also, what is hossie? I have never heard of that before.

I was away with cadets last week, I had to march 4 times a day (to breakfast and evening meals, and back) which I really struggled with. But, the 2nd day of the trip I got one of the two scores of 470 I have had. I also had an 'attack' that week, and so I was trying the take my blue inhaler 1 puff a minute. I read this in a asthma UK booklet. That night I was with another staff member, who was asking about my day, I replied It was quite enjoyable, except this when I was not able to breathe. She started shouting saying taking it that much can be dangerous.. I am not someone to argue. But, surly not taking it and stopping breathing is worse? But, their are a few other things where we defiantly have different information from different places, so, I have decided to follow the advice from the nurses to take the blue inhaler before exercise, and the book when it is an attack as described in the book.

Now I am thinking about if I should go back or not, I have been to a nurse 2 times in 4 weeks. I am supposed to go for a review thing in 3 months, but go back earlier if any problems. It is not really a problem, just that I am worried by how much I still struggled doing exercise last week, even with now 4 puffs of the red inhaler a day, and 2 puffs of the blue inhaler before any exercise. I start college again next month studding adventure sports, and last year I missed 6 months of practicals because they thought I could have a heart problem, had to go to a specialist, have a scan, get the results. And could not exercise in all that time. So, the last thing I want now I know it's asthma, is to miss anything at college this year. But, I've been to the nurse twice in 4 weeks, don't want o be wasting time, as their are posters everywhere about.



hossie = shortened version of hospital!

So if your best peak flow (the highest number you've ever had) is 470, then your ""green"" zone is 350-470 (Normally indicates asthma symptoms are minimal), you're ""Amber"" zone is 230-350 (This would usually be the point asthma is starting to become a problem, either take your reliever or if that is not having an effect you should try and see a doctor). Anything below 350 would be your ""red"" zone (Red normally indicates an asthma attack and so you would follow the asthma attack plan). Peak flow is just a good tool to use in monitoring your asthma. Different people experience symptomsat different levels, and for some individuals peak flow is not a very useful measuring tool as it is too late to respond to increasing symptoms. Always go by how you feel first and foremost, but peak flow can be useful if you're feeling unsure. Wiggly peak flows are generally a bad sign - you want as little variability as possible - but in the green zone, to show your airways are as open as possible. Make sure to stand up and take a big breath before doing your peak flow, make sure to do it three times, and record the best score of the three!

In terms ofgoing back to see the nurse, the general rule is that doctors/nurses would ALWAYS rather see an asthmatic who is probably alright, than wait a few days/weeks and see an asthmatic who is really very poorly! It is worth taking the time to ensure you are getting the most out of your current treatment regime, and also that you're on the best treatment for you! Don't worry about feeling like you're going too frequently - getting used to a new diagnosis is always tricky!! I currently see my consultant at least every 3 weeks, and my GP at least every fortnight - although sometimes she doesnt want to go more than a week without pestering me!! It's worth it to get things under control!!

In an attack its not so much the worry of 'overdosing' on salbutamol in the traditional sense. You will get palpitations and tremors if you take a lot (if you really took loads you can get high lactate and low potassium, but that does take an awful lot). Its more that sitting at home relying on insane amounts of salbutamol to keep breathing is potentially dangerous as it means you could potentially get very poorly before getting help. That is why the standard 'rule of thumb' is 10 puffs. I think asthma UK says 2 puffs every 2 minutes - but there is a page on the site called 'what to do in an asthma attack' if you wanted to check that out. Up to ten puffs. If by that point you've not started improving, then it would be appropriate to seek medical help (usually by ringing 999). You may read people on here talking about taking significantly more than that, that is sort of an exception (that comes from a site that attracts more severe asthmatics) when people have been specifically told they can have more salbutamol than normal before getting help.

If i were you i'd go back to the nurse to clear things up - be proactive about your health - honestly - they get people going for some really stupid reasons, and yours isnt a stupid reason!!!

HTH! Soph


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