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Peak flow

Public summary: 

A peak flow meter often used by medical staff to measure the maximum speed you can expel a 'huff' of air. This can be used to gather useful information about the function of the lungs.

Using a peak flow meter to measure peak flow rates
Useful information
Kit List: 

Peak flow meter & disposable mouth pieces
Peak flow meter
Models of normal and constricted airways (made from foam and tape)
Bung with a hole in it, plus blu-tac (possibly, if I have finished making it!)


This experiment allows kids to have fun competing to see who has the highest peak flow and also acts as a starting point for discussion of lungs, breathing and conditions such as asthma.

-get kids to use a peak flow meter

-what is a peak flow meter and what might it be used for?
- basic explanation of how the lungs work
-why do you want to know about your peak flow rate? asthma, fibrosis, COPD etc

It's very important to establish in the beginning how much the kid knows already. Generally, kids either know a lot (i.e. if they are asthmatic) or very little. If they know very little, keep things very basic. If they know a lot, you can go into more detail; i.e. how the lungs work; that lungs are made out of tissue; tissue structure can change (inflammation; fibrosis)- how this affects your breathing


Peak Flow

1. Establish how much the child knows already:

- Ask them if they know what a peak flow is.
- If they do ask them what it's used for. (chances are a good chunk of them have asthma and will have used one).
- If they don't know what it is, ask them what they think it might be used for.
- This should be quite easy to guess from the design, but if they're struggling, work them round to it.
- Point out the meter - ie it's for measuring something.
- at the 0 end of the meter there's a wacking great mouth shaped hole, so how do you think you get the meter to move?
- If they say blowing into, then ask them what sort of diseases it might be used for. asthma, emphysema, bronchitis.

2. Then link what it's for to a discussion on asthma.
- So if it's for seeing how well someone with asthma breaths, do you think asthmatics can blow more or less on it?
- Why do they blow less. (see diagram below)
- Lungs = set of bags at end of set of tubes.
- Ref them to lung model for how lungs work, but basically say muscles make air move in and out.
- In asthmatics, the tubes are narrower.
- Tubes are narrower because...
- Need to pitch this depending on age of kid.
- Mention allergy.
- Mention other things that can trigger, eg asthma, cold air.

3. Do only kids have asthma?
No - adults can get it as well. Late in life onset and child onset forms of asthma are common.

4. So do you thinks astmatics blow the same thing on the peak flow all day?
No - they are usually worse in the morning that they are in the evening.

5. Finally, see what the kids can blow and match it Vs the diagram below.

6. For older kids it might be worth going into:

a Why narrower tubes stop you blowing as well.
b. Inflamation.
c. Other things that you use lung function tests for: COPD, Sarcoidosis, Fibrosis etc.

You can also get kids to put a straw in their mouth and breathe out through it for a few breaths, to demonstrate how much more difficult it is to exhale through smaller tubes. Only let them do this if they are sensible, breathe normally for only a few breaths, and are SITTING DOWN while they do so!

It might also be possible to plug the end of a mouthpiece with the rubber bung, put a straw through the bung (you will need blue tack to make it airtight) and then compare the peak flow reading that can be achieved blowing through the straw to that blowing straight through the mouthpiece, again demonstrating the effects of narrowed airways.

Risk Assessment
Date risk assesment last checked: 
Mon, 27/01/2020
Risk assesment checked by: 
Date risk assesment double checked: 
Mon, 27/01/2020
Risk assesment double-checked by: 
Beatrix Huissoon
Risk Assessment: 

Measuring peak flow using a peak flow meter.

Hazard Risk Likelihood Severity Overall Mitigation Likelihood Severity Overall
Mouthpiece Transfer of infection from mouthpiece. 3 2 6 Make sure to use a new mouth piece each time, and dispose of old ones. 1 2 2
Over-Exertion Fainting risk due to over-exertion. 3 3 9 The risk of this is probably low, but keep an eye on people using the peak flow meter to ensure that they are not over-exerting themselves to this point. Be aware of what participants might fall on in the event of fainting. Only allow them to try the exhaling through straws part if they are SITTING DOWN, and only let them do so for a few, gentle breaths.
In case of accident, call a first aider.
2 3 6